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Background: Children are less susceptible than adults to symptomatic COVID‐19 infection, but very few studies addressed their underlying cause. Moreover, very few studies analyzed why children highly exposed to the virus remain uninfected. Methods: We analyzed the serum levels of ACE2, angiotensin II, anti-spike and anti-N antibodies, cytokine profiles, and virus neutralization in a cohort of children at high risk of viral exposure, cohabiting with infected close relatives during the lockdown in Spain. Results: We analyzed 40 children who were highly exposed to the virus since they lived with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-infected relatives during the lockdown for several months without taking preventive measures. Of those, 26 reported mild or very mild symptoms. The induced immune response to the virus was analyzed 3 months after the household infection. Surprisingly, only 15 children had IgG anti-S (IgG+) determined by a sensitive method indicative of a past infection. The rest, negative for IgG anti-N or S in various tests, could be further subdivided, according to IgM antibodies, into those having IgM anti-S and IgM anti-N (IgG−IgMhigh) and those having only IgM anti-N (IgG−IgMlow). Interestingly, those two subgroups of children with IgM antibodies have strikingly different patterns of cytokines. The IgMhigh group had significantly higher IFN-α2 and IFN-γ levels as well as IL-10 and GM-CSF than the IgMlow group. In contrast, the IgMlow group had low levels of ACE2 in the serum. Both groups have a weaker but significant capacity to neutralize the virus in the serum than the IgG+ group. Two children were negative in all immunological antibody tests. Conclusions: A significant proportion of children highly exposed to SARS-CoV-2 did not develop a classical adaptive immune response, defined by the production of IgG, despite being in close contact with infected relatives. A large proportion of those children show immunological signs compatible with innate immune responses (as secretion of natural antibodies and cytokines), and others displayed very low levels of the viral receptor ACE2 that may have protected them from the virus spreading in the body despite high and constant viral exposure., This research was funded by grants from “Ministerio de Ciencia e Innovación” (PID-2019104760RB-100); “Comunidad de Madrid” (S2017/BMD-3671. INFLAMUNE-CM; FEDER and COTRAVI-19-CM) to MF; Consejo Superior de Investigaciones Científica, CSIC (CSIC-COV19-108, SGL210235) to MF and UB; CRUE-Supera COVID; the European Development Regional Fund “A way to achieve Europe” (ERDF); Merck, Sharp and Dohme Investigator Studies Program (code MISP# IIS 60257); and Fondo Supera COVID-19 (2020–001) to SSV. The study also received institutional grants from “Fundación Ramón Areces” and “Banco de Santander.”

The long quest for efficient drug administration has been looking for a universal carrier that can precisely transport traditional drugs, new genomic and proteic therapeutic agents. Today, researchers have found conditions to overcome the two main drug delivery dilemmas. On the one side, the versatility of the vehicle to efficiently load, protect and transport the drug and then release it at the target place. On the other hand, the questions related to the degree of PEGylation which are needed to avoid nanoparticle (NP) aggregation and opsonization while preventing cellular uptake. The development of different kinds of lipidic drug delivery vehicles and particles has resulted in the development of ionizable lipid nanoparticles (iLNPs), which can overcome most of the typical drug delivery problems. Proof of their success is the late approval and massive administration as the prophylactic vaccine for SARS-CoV-2. These ILNPs are built by electrostatic aggregation of surfactants, the therapeutic agent, and lipids that self-segregate from an aqueous solution, forming nanoparticles stabilized with lipid polymers, such as PEG. These vehicles overcome previous limitations such as low loading and high toxicity, likely thanks to low charge at the working pH and reduced size, and their entry into the cells via endocytosis rather than membrane perforation or fusion, always associated with higher toxicity. We herein revise their primary features, synthetic methods to prepare and characterize them, pharmacokinetic (administration, distribution, metabolization and excretion) aspects, and biodistribution and fate. Owing to their advantages, iLNPs are potential drug delivery systems to improve the management of various diseases and widely available for clinical use., We acknowledge financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU) (RTI2018-099965- B-I00, AEI/FEDER,UE) proyectos de I+D+i de programación conjunta internacional MCIN/AEI (CONCORD, PCI2019- 103436) cofunded by the European Union and Generalitat de Catalunya (2017-SGR-1431). ICN2 is supported by the Severo Ochoa program from Spanish MINECO (SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya.

This work was supported by the Spanish Ministry of Science, Innovation and Universities (RTI-2018-094213-A-I00 and PID-2021- 123810OBI00) to MD, the “Atracció n de Talento Investigador” programme (2017-T1/BMD-5155) funded by the “Comunidad de Madrid” to MD, the Spanish National Research Council (CSIC)’s Global Health Platform (PTI Salud Global, CSIC-COV19-012/ 012202020E086) to MD, and a “Ramon y Cajal” Incorporation grant (RYC-2017) from the Spanish Ministry of Science, Innovation and Universities and research incorporation grant (202240I182) from CSIC to AN.

Current vaccines against SARS-CoV-2, based on the original Wuhan sequence, induce antibodies with different degrees of cross-recognition of new viral variants of concern. Despite potent responses generated in vaccinated and infected individuals, the Omicron (B.1.1.529) variant causes breakthrough infections, facilitating viral transmission. We previously reported a vaccine based on a cyclic peptide containing the 446-488 S1 sequence (446-488cc) of the SARS-CoV-2 spike (S) protein from Wuhan isolate. To provide the best immunity against Omicron, here we compared Omicron-specific immunity induced by a Wuhanbased 446-488cc peptide, by a Wuhan-based recombinant receptor-binding domain (RBD) vaccine and by a new 446-488cc peptide vaccine based on the Omicron sequence. Antibodies induced by Wuhan peptide 446-488cc in three murine strains not only recognized the Wuhan and Omicron 446-488 peptides similarly, but also Wuhan and Omicron RBD protein variants. By contrast, antibodies induced by the Wuhan recombinant RBD vaccine showed a much poorer cross-reactivity for the Omicron RBD despite similar recognition of Wuhan and Omicron peptide variants. Finally, although the Omicron-based 446-488cc peptide vaccine was poorly immunogenic in mice due to the loss of T cell epitopes, co-immunization with Omicron peptide 446-488cc and exogenous T cell epitopes induced strong cross-reactive antibodies that neutralized Omicron SARS-CoV-2 virus. Since mutations occurring within this sequence do not alter T cell epitopes in humans, these results indicate the robust immunogenicity of 446-488cc-based peptide vaccines that induce antibodies with a high crossrecognition capacity against Omicron, and suggest that this sequence could be included in future vaccines targeting the Omicron variant., This work was supported by Instituto de Salud Carlos III, Fondo Europeo de Desarrollo Regional “Una manera de hacer Europa” under grant PI20/00260, Gobierno de Navarra under grant 0011- 3597-2020-000024 to PS and by Paula & Rodger Riney Foundation to JJL. This research was also supported by Spanish Research Council (CSIC) grants 202120E079 (to JG-A) and 2020E84 (to ME), Spanish Ministry of Science and Innovation (MCIN)/Spanish Research Agency (AEI)/10.13039/501100011033 grant (PID2020-114481RBI00; to JG-A and ME), and Centro de Investigación Biomédica en Red de Enfermedades Infecciosas (CIBERINFEC) co-financed with FEDER funds (to JG-A). This research work was also funded by the European Commission-NextGenerationEU, through CSIC’s Global Health Platform (PTI Salud Global) (to JG-A and ME). JG-A and ME also acknowledge financial support from the Spanish State Research Agency, AEI/10.13039/501100011033, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2013-0347, SEV- 2017-0712).

28 p.-4 fig.-4 tab., Chemoattraction, defined as the migration of a cell toward a source of a chemical gradient, is controlled by chemoattractant receptors. Chemoattraction involves two basic activities, namely, directional sensing, a molecular mechanism that detects the direction of a source of chemoattractant, and actin-based motility, which allows the migration of a cell towards it. Current models assume first, that chemoattractant receptors govern both directional sensing and motility (most commonly inducing an increase in the migratory speed of the cells, i.e. chemokinesis), and, second, that the signaling pathways controlling both activities are intertwined. We performed a meta-analysis to reassess these two points. From this study emerge two main findings. First, although many chemoattractant receptors govern directional sensing, there are also receptors that do not regulate cell motility, suggesting that is the ability to control directional sensing, not motility, that best defines a chemoattractant receptor. Second, multiple experimental data suggest that receptor-controlled directional sensing and motility can be controlled independently. We hypothesize that this independence may be based on the existence of separated signalling modules that selectively govern directional sensing and motility in chemotactic cells. Together, the information gathered can be useful to update current models representing the signalling from chemoattractant receptors. The new models may facilitate the development of strategies for a more effective pharmacological modulation of chemoattractant receptor-controlled chemoattraction in health and disease. “We shall not cease from exploration And the end of all our exploring Will be to arrive where we started And know the place for the first time” from “Little Gidding” by T.S. Elliot, This work was supported by grants SAF-2014-53151-R (Ministerio de Economía y Competitividad), SAF2017-83306-R (Ministerio de Ciencia, Innovación y Universidades), RIER (RETICS Program/Instituto de Salud Carlos III) (RD08/0075, RD16/0012/0007) and PID2020-114147RB-100 (Ministerio de Ciencia e Innovación).

Current coronavirus disease-19 (COVID-19) vaccines are administered by the intramuscular route, but this vaccine administration failed to prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus infection in the upper respiratory tract, mainly due to the absence of virus-specific mucosal immune responses. It is hypothesized that intranasal (IN) vaccination could induce both mucosal and systemic immune responses that blocked SARS-CoV-2 transmission and COVID-19 progression. Here, we evaluated in mice IN administration of three modified vaccinia virus Ankara (MVA)-based vaccine candidates expressing the SARS-CoV-2 spike (S) protein, either the full-length native S or a prefusion-stabilized [S(3P)] protein; SARS-CoV-2-specific immune responses and efficacy were determined after a single IN vaccine application. Results showed that in C57BL/6 mice, MVA-based vaccine candidates elicited S-specific IgG and IgA antibodies in serum and bronchoalveolar lavages, respectively, and neutralizing antibodies against parental and SARS-CoV-2 variants of concern (VoC), with MVA-S(3P) being the most immunogenic vaccine candidate. IN vaccine administration also induced polyfunctional S-specific Th1-skewed CD4+ and cytotoxic CD8+ T-cell immune responses locally (in lungs and bronchoalveolar lymph nodes) or systemically (in spleen). Remarkably, a single IN vaccine dose protected susceptible K18-hACE2 transgenic mice from morbidity and mortality caused by SARS-CoV-2 infection, with MVA-S(3P) being the most effective candidate. Infectious SARS-CoV-2 viruses were undetectable in lungs and nasal washes, correlating with high titers of S-specific IgGs and neutralizing antibodies against parental SARS-CoV-2 and several VoC. Moreover, low histopathological lung lesions and low levels of pro-inflammatory cytokines in lungs and nasal washes were detected in vaccinated animals. These results demonstrated that a single IN inoculation of our MVA-based vaccine candidates induced potent immune responses, either locally or systemically, and protected animal models from COVID-19. These results also identified an effective vaccine administration route to induce mucosal immunity that should prevent SARS-CoV-2 host-to-host transmission., We thank CSIC and MCIN for continuous support. We thank Centro de Investigación en Sanidad Animal (CISA)- Instituto Nacional de Investigaciones Agrarias (INIA-CSIC) (Valdeolmos, Madrid, Spain) for the BSL-3 facilities. SARSCoV- 2 MAD6 virus isolate was kindly provided by José M. Honrubia and Dr. Luis Enjuanes (CNB-CSIC, Madrid, Spain). We thank the Histology Facility at CNB-CSIC for histological preparation of biological samples. We thank Carlos Ó scar Sánchez Sorzano from the CNB Bioinfomatic Unit for help with the statistical analysis. We thank Iván Jareño from the CNB Animal Faci l i t ies for help and assistance.

Various species of the SARS-CoV-2 host cell receptor, the angiotensin-converting enzyme 2 (ACE2), are present in serum, which may result from virus entry and subsequent proteolytic processing of the membrane receptor. We have recently demonstrated changes of particular ACE2 species in virus infected humans, either cleaved fragments or circulating full-length species. Here, we further explore the potential of serum ACE2 as a biomarker to test SARS-CoV-2 infection and vaccine efficacy in virus susceptible transgenic K18-hACE2 mice expressing human ACE2. First, in serum samples derived from K18-hACE2 mice challenged with a lethal dose of SARS-CoV-2, we observed an increase in the levels of cleaved ACE2 fragment at day 2 post-challenge, which may represent the subsequent proteolytic processing through virus entry. These elevated levels were maintained until the death of the animals at day 6 post-challenge. The circulating full-length ACE2 form displayed a sizable peak at day 4, which declined at day 6 post-challenge. Noticeably, immunization with two doses of the MVA-CoV2-S vaccine candidate prevented ACE2 cleaved changes in serum of animals challenged with a lethal dose of SARS-CoV-2. The efficacy of the MVA-CoV2-S was extended to vaccinated mice after virus re-challenge. These findings highlight that ACE2 could be a potential serum biomarker for disease progression and vaccination against SARS-CoV-2., This study was funded in part by the Instituto de Investigación Sanitaria y Biomédica de Alicante (ISABIAL; grant 2020-0308), the Direcció General de Ciència I Investigació, Generalitat Valenciana (AICO/2021/308), and by the Instituto de Salud Carlos III (ISCIII, grants PI19-01359), co-financed by the Fondo Europeo de Desarrollo Regional (FEDER, “Investing in your future”) and through CIBERNED, ISCIII. We also acknowledge financial support from the Spanish Ministerio de Economía y Competitividad, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2017-0723). This research was also supported by Fondo COVID-19 grant COV20/00151 (Spanish Health Ministry, Instituto de Salud Carlos III (ISCIII)), Fondo Supera COVID-19 grant (Crue Universidades-Banco Santander), and Spanish Research Council (CSIC) grant 202120E079 (to JG-A); CSIC grant 2020E84, Ferrovial, and MAPFRE donations (to ME); and Spanish Ministry of Science and Innovation (MCIN)/Spanish Research Agency (AEI)/10.13039/501100011033 grant (PID2020-114481RB-I00; to JG-A and ME). This research work was also funded by the European Commission- NextGenerationEU, through CSIC’s Global Health Platform (PTI Salud Global) (to JG-A and ME). MPL is supported by a BEFPI scholarship from the Generalitat Valenciana. JGA and ME acknowledges financial support from the Spanish State Research Agency, AEI/10.13039/501100011033, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2013-0347, SEV-2017-0712).

Oncogene-immortalized bone marrow-derived macrophages are considered to be a good model for the study of immune cell functions, but the factors required for their survival and proliferation are still unknown. Although the effect of the thyroid hormones on global metabolic and transcriptional responses in macrophages has not yet been examined, there is increasing evidence that they could modulate macrophage functions. We show here that the thyroid hormone T3 is an absolute requirement for the growth of immortal macrophages. The hormone regulates the activity of the main signaling pathways required for proliferation and anabolic processes, including the phosphorylation of ERK and p38 MAPKs, AKT, ribosomal S6 protein, AMPK and Sirtuin-1. T3 also alters the levels of metabolites controlling transcriptional and post-transcriptional actions in macrophages, and causes widespread transcriptomic changes, up-regulating genes needed for protein synthesis and cell proliferation, while down-regulating genes involved in immune responses and endocytosis, among others. This is not observed in primary bone marrow-derived macrophages, where only p38 and AMPK activation is regulated by T3 and in which the metabolic and transcriptomic effects of the hormone are much weaker. However, the response to IFN-γ is reduced by T3 similarly in immortalized macrophages and in the primary cells, confirming previous results showing that the thyroid hormones can antagonize JAK/STAT-mediated signaling. These results provide new perspectives on the relevant pathways involved in proliferation and survival of macrophage cell culture models and on the crosstalk between the thyroid hormones and the immune system., This work has been funded by grants SAF2017-83289-R and PID2020-116146RB-I00 to SA and AA, PID2019-104284RBI00/AEI/10.13039/501100011033 to AC and SAF2017-90604REDT to AA and AC from Ministerio de Ciencia Innovación y Universidades; by grant B2017/BMD-3724 to SA and AA from the Comunidad de Madrid; and by CIBERONC CB/16/00228 to AA from the Instituto de Salud Carlos III. The cost of this publication has been paid in part by FEDER Funds.

Immunosuppressant conditions such as hematological malignancies increase the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. It has been described in the literature that patients on anti-CD20 maintenance therapies for lymphoid malignancies are susceptible to having recurrent flares together with viral replication or reinfections, although these cases are scarce. These patients are not well represented in randomized controlled trials, and as a consequence, the evidence for the use of certain treatments in this scenario is lacking. We present two cases of patients with B-cell lymphoma on remission and treated with rituximab on maintenance. They developed at least 1 flare of coronavirus disease 2019 (COVID-19) after acute infection and always after receiving rituximab. RT-PCR was positive in the nasopharyngeal swab and also in plasma. Patients were treated during flares with remdesivir, hyperimmune plasma, and corticosteroids. These two cases showed the unresolved problem of COVID-19 in immunosuppressant patients and showed that despite the vast amount of information available on SARS-CoV-2, information in this subgroup of patients is lacking., This study was supported by Plan Nacional de I+D+i 2013‐2016, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spanish Network for Research in Infectious Diseases (REIPI RD16/0016/0001)—cofinanced by the European Development Regional Fund “A way to achieve Europe”, Operative Program Intelligence Growth 2014‐2020.

The emergence of COVID-19 has led to a worldwide challenge for the rapid development of vaccines. Several types of safe and effective vaccines have been available in a time frame never seen before. Now that several hundred million people have been vaccinated there is an opportunity to compare vaccines in terms of protection and immune response. Here, we have applied a highly sensitive multiplexed flow cytometry method to measure simultaneously IgM, IgG1 and IgA anti-spike protein antibodies generated in response to three vaccines: ChAdOx1 (Oxford-AstraZeneca), mRNA-1273 (Moderna), and BNT162b2 (Pfizer-BioNTech). We have found that mRNA vaccines (mRNA-1273 and BNT162b2) induce a stronger humoral response, both after the first and the second dose, than the adenovirus-based ChAdOx1 vaccine. We also found that, in the elderly, antibody titers negatively correlate with the age of the donor but, also, that antibody titers remain stable for at least 6 months after complete vaccination. Finally, we found that one dose of BNT162b2 is sufficient to induce the highest antibody titers in seropositive pre-vaccination donors. We hope these data will help to guide future decisions on vaccination strategies., This work was funded by intramural grant CSIC-COVID19-004: 202020E081 (to BA). L.H has been supported by an FPI fellowship from the Spanish Ministry of Science and Innovation.

We generated an optimized COVID-19 vaccine candidate based on the modified vaccinia virus Ankara (MVA) vector expressing a full-length prefusion-stabilized SARS-CoV-2 spike (S) protein, termed MVA-CoV2-S(3P). The S(3P) protein was expressed at higher levels (2-fold) than the non-stabilized S in cells infected with the corresponding recombinant MVA viruses. One single dose of MVA-CoV2-S(3P) induced higher IgG and neutralizing antibody titers against parental SARS-CoV-2 and variants of concern than MVA-CoV2-S in wild-type C57BL/6 and in transgenic K18-hACE2 mice. In immunized C57BL/6 mice, two doses of MVA-CoV2-S or MVA-CoV2-S(3P) induced similar levels of SARS-CoV-2-specific B- and T-cell immune responses. Remarkably, a single administration of MVA-CoV2-S(3P) protected all K18-hACE2 mice from morbidity and mortality caused by SARS-CoV-2 infection, reducing SARS-CoV-2 viral loads, histopathological lesions, and levels of pro-inflammatory cytokines in the lungs. These results demonstrated that expression of a novel full-length prefusion-stabilized SARS-CoV-2 S protein by the MVA poxvirus vector enhanced immunogenicity and efficacy against SARS-CoV-2 in animal models, further supporting MVA-CoV2-S(3P) as an optimized vaccine candidate for clinical trials., This research was supported by Spanish Health Ministry, Instituto de Salud Carlos III (ISCIII), Fondo COVID-19 grant COV20/00151, Fondo Supera COVID-19 (Crue Universidades-Banco Santander) grant and Spanish Research Council (CSIC) grant 202120E079 (to JG-A), CSIC grant 2020E84, La CaixaImpulse grant CF01-00008, Ferrovial and MAPFRE donations (to ME), and Spanish Ministry of Science and Innovation (MICINN), Spanish Research Agency grant PID2020-114481RB-I00 (to JG-A and ME). This research work was also funded by the European Commission-NextGenerationEU, through CSIC’s Global Health Platform (PTI Salud Global) (to JG-A and ME). JC acknowledges MICINN and CSIC support (project number 202020E079). RD received grants from the European Commission Horizon 2020 Framework Programme: Project VIRUSCAN FETPROACT-2016: 731868 and EPIC-CROWN-2-2021:101046084, and Fundación Caixa-Health Research HR18-00469 (Project StopEbola).

A microRNA (miRNA) often regulates the expression of hundreds of target genes. A fundamental question in the field of miRNA research is whether a miRNA exerts its biological function through regulating a small number of key targets or through small changes in the expression of hundreds of target genes. We addressed this issue by performing functional analysis of target genes regulated by miR-148a. We previously identified miR-148a as a critical regulator of B cell central tolerance and found 119 target genes that may mediate its function. We selected 4 of them for validation and demonstrated a regulatory role for Bim, Pten, and Gadd45a in this process. In this study, we performed functional analysis of the other miR-148a target genes in in vitro and in vivo models of B cell central tolerance. Our results show that those additional target genes play a minimal role, if any, in miR-148a-mediated control of B cell central tolerance, suggesting that the function of miRNAs is mediated by a few key target genes. These findings have advanced our understanding of molecular mechanisms underlying miRNA regulation of gene expression and B cell central tolerance., This work was supported by the grants RTI2018-100008-A-I00 funded by Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033/and FEDER, SI1-PJI-2019-00241 from Community of Madrid (Spain), merit award RyC-21155 funded by Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 and FSE to AG-M, and by the National Natural Science Foundation of China (81830047 to CX).

DC is supported by grant from Ayudas Fundación BBVA a Equipos de Investigación Cientıfí ca (BIOMEDICINA-2018) and “La Caixa” Banking Foundation (HR17-00016). MP is supported by the Spanish Science, Innovation and University Ministry (RT2018—094211-B-100-FEDER), La Caixa Foundation (LCF/ PR/HR20/52400017) and La Marató-TV3. Sí

Background: COVID‐19 can generate a broad spectrum of severity and symptoms. Many studies analysed the determinants of severity but not among some types of symptoms. More importantly, very few studies analysed patients highly exposed to the virus that nonetheless remain uninfected. Methods: We analysed serum levels of ACE2, Angiotensin II and anti-Spike antibodies in 2 different cohorts at high risk of viral exposure, highly exposed but uninfected subjects, either high risk health care workers or persons cohabiting with infected close relatives and seropositive patients with symptoms. We tested the ability of the sera of these subjects to neutralize lentivirus pseudotyped with the Spike-protein. Results: We found that the serum levels of ACE2 are significantly higher in highly exposed but uninfected subjects. Moreover, sera from this seronegative persons can neutralize SARS-CoV-2 infection in cellular assays more strongly that sera from non-exposed negative controls eventhough they do not have anti-CoV-2 IgG antibodies suggesting that high levels of ACE2 in serum may somewhat protect against an active infection without generating a conventional antibody response. Finally, we show that among patients with symptoms, ACE2 levels were significantly higher in infected patients who developed cutaneous as compared with respiratory symptoms and ACE2 was also higher in those with milder symptoms. Conclusions: These findings suggest that soluble ACE2 could be used as a potential biomarker to predict SARS-CoV-2 infection risk and to discriminate COVID-19 disease subtypes., This research was funded by grants from “Ministerio de Ciencia e Innovación” (SAF2013-42850-R, SAF2016-75988-R and PID-2019104760RB-100; FEDER), “Comunidad de Madrid (S2017/BMD-3671. INFLAMUNE-CM; FEDER) to MF, Consejo Superior de Investigaciones Científica, CSIC (CSIC-COV19-108, SGL210235) to MF and UB, CRUE-Supera COVID, the European Development Regional Fund ‘‘A way to achieve Europe’’ (ERDF), Merck, Sharp & Dohme Investigator Studies Program (code MISP# IIS 60257), and Fondo Supera COVID-19 (2020-001) to SS-V. Institutional grants from “Fundación Ramón Areces” and “Banco de Santander”. This research work was also funded by the European Commission – NextGenerationEU (Regulation EU 2020/2094), through CSIC's Global Health Platform (PTI Salud Global).

Metabolic associated fatty liver disease (MAFLD) is the most prevalent form of liver disease worldwide, accounting for a high liver-related mortality and morbidity with extensive multi-organ involvement. This entity has displaced viral hepatitis as the main cause of severe forms of hepatic diseases, although the onset and transition of MAFLD stages still remains unclear. Nevertheless, innate and adaptive immune responses seem to play an essential role in the establishment and further progression of this disease. The immune system is responsible of safeguard and preserves organs and systems function, and might be altered under different stimuli. Thus, the liver suffers from metabolic and immune changes leading to different injuries and loss of function. It has been stablished that cell-cell crosstalk is a key process in the hepatic homeostasis maintenance. There is mounting evidence suggesting that MAFLD pathogenesis is determined by a complex interaction of environmental, genetic and host factors that leads to a full plethora of outcomes. Therefore, herein we will revisit and discuss the interplay between immune mechanisms and MAFLD, highlighting the potential role of immunological markers in an attempt to clarify its relationship., The research leading to these results has received funding from the Consejerı́a de Salud de la Junta de Andalucı́a under grant agreement PC-0148-2016-0148, the Ministerio de Economı́a y Competitividad under grant agreement AGL2017-86927-R, the Instituto de Salud Carlos III under grant agreements PI16/01842, PI19/01404, PI19/00589, IFI18/00041 and CD18/00126, and the Fondo Europeo de Desarrollo Regional (FEDER) in cooperation with the Consejerı́a de Salud de la Junta de Andalucı́a (PE-0451- 2018). RG-D has received the Andrew K Burroughs Fellowship from European Association for the Study of the Liver (EASL), the Aprendizaje de Nuevas Tecnologı́as fellowship from Asociación Española para el Estudio del Hı́gado (AEEH), and the CIBERehd Grant to support researcher’s mobility.

© 2021 Perez-Chacon, Vincent-Fabert and Zapata., B cell malignancies represent a vast group of different entities arising from the multiple differentiation stages of B cells. In humans, there is a large variety of B cell malignancies, most of which have counterparts in mice. Prognosis and treatment for these malignancies would be largely dependent on their type, stage and grade., GP-C and JMZ were supported by a grant from the Agencia Estatal de Investigacion (PID2019-110405RB-I00/AEI/10.13039/ 501100011033). CV-F was supported by the France Lymphome Espoir association of patients and the Ligue contre le cancer.

The COVID-19 pandemic caused by SARS-CoV-2 challenges the understanding of factors affecting disease progression and severity. The identification of prognostic biomarkers and physiological processes associated with disease symptoms is relevant for the development of new diagnostic and therapeutic interventions to contribute to the control of this pandemic. To address this challenge, in this study, we used a quantitative proteomics together with multiple data analysis algorithms to characterize serum protein profiles in five cohorts from healthy to SARS-CoV-2-infected recovered (hospital discharge), nonsevere (hospitalized), and severe [at the intensive care unit (ICU)] cases with increasing systemic inflammation in comparison with healthy individuals sampled prior to the COVID-19 pandemic. The results showed significantly dysregulated proteins and associated biological processes and disorders associated to COVID-19. These results corroborated previous findings in COVID-19 studies and highlighted how the representation of dysregulated serum proteins and associated BPs increases with COVID-19 disease symptomatology from asymptomatic to severe cases. The analysis was then focused on novel disease processes and biomarkers that were correlated with disease symptomatology. To contribute to translational medicine, results corroborated the predictive value of selected immune-related biomarkers for disease recovery [Selenoprotein P (SELENOP) and Serum paraoxonase/arylesterase 1 (PON1)], severity [Carboxypeptidase B2 (CBP2)], and symptomatology [Pregnancy zone protein (PZP)] using protein-specific ELISA tests. Our results contributed to the characterization of SARS-CoV-2–host molecular interactions with potential contributions to the monitoring and control of this pandemic by using immune-related biomarkers associated with disease symptomatology., This research was partially funded by Junta de Comunidades de Castilla-La Mancha (JCCM), Spain and EU-FEDER (grants MYCOTRAINING SBPLY/19/180501/000174 and GALINFEC SBPLY/17/180501/000185). EF-C has a predoctoral grant from UCLM. MC was funded by the Ministerio de Ciencia, Innovación y Universidades, Spain (grant FJC-2018-038277-I). IGF was supported by UCLM. MV was supported by UCLM and EU-FEDER.

[Introduction]: CD4+ T cells with regulatory function co-expressing Foxp3 and RORγt are linked to the development of oral tolerance towards innocuous food antigens in mice. This study aimed to discern the role played by IL-6 and retinoic acid (RA) in the in vitro generation of Foxp3+RORγt+ T cells and to investigate whether such cells have suppressive properties., [Methods]: CD4+CD25- T cells isolated from the spleen of BALB/c mice, were stimulated in the presence of IL-2 alone or together with TFG-β and different concentrations of IL-6 and/or RA. Percentage of Foxp3+, RORγt+, IL-17+, Foxp3+RORγt-, Foxp3+RORγt+, and Foxp3-RORγt+ T cells within the total CD4+ T cell population, production of cytokines (IL-10 and IL-17A) and gene expression (Foxp3, Rorc, Tgfb1, Il6, Il10, and Il17) were assessed at different time points. The phenotype and ability of cells generated from CD4+CD44-CD62L+ cells in the presence of RA to suppress effector T cell proliferation was assessed., [Results]: TGF-β plus IL-6 induced the generation of Foxp3+ and double positive Foxp3+RORγt+ T cells to a higher extent than TGF-β alone at the beginning of the incubation period, although expression of Foxp3 subsequently declined. RA, added to TGF-β, increased Foxp3 and Rorc expression and Foxp3 and RORγt transcription and promoted the differentiation of Foxp3+RORγt- and Foxp3+RORγt+ cells that expressed and secreted IL-17. Foxp3+ T cells generated in vitro in presence of RA were functionally suppressive., [Conclusions]: Under the influence of IL-2 and TGF-β, suppressive Foxp3+RORγt+ T cells that express and secrete IL-17 can be produced in vitro and RA further contributes to stabilize this phenotype., This work was supported by Ministerio de Ciencia e Innovación through grants AGL2017-88964-R, FPU16/01974 (to LP-R) and JCI-2017-31345 (to SB).

There are still many unanswered questions concerning viral SARS-CoV-2 pathogenesis in COVID-19. Accessory proteins in SARS-CoV-2 consist of eleven viral proteins whose roles during infection are still not completely understood. Here, a review on the current knowledge of SARS-CoV-2 accessory proteins is summarized updating new research that could be critical in understanding SARS-CoV-2 interaction with the host. Some accessory proteins such as ORF3b, ORF6, ORF7a and ORF8 have been shown to be important IFN-I antagonists inducing an impairment in the host immune response. In addition, ORF3a is involved in apoptosis whereas others like ORF9b and ORF9c interact with cellular organelles leading to suppression of the antiviral response in infected cells. However, possible roles of ORF7b and ORF10 are still awaiting to be described. Also, ORF3d has been reassigned. Relevant information on the knowns and the unknowns in these proteins is analyzed, which could be crucial for further understanding of SARS-CoV-2 pathogenesis and to design strategies counteracting their actions evading immune responses in COVID-19., NR was a fellow funded by project grant 202020E170 from PTI Salud Global (CSIC). SZ-L was a Juan de la Cierva Incorporación fellow IJCI-2017-31382. This work was supported by grants 202020E170 from PTI Salud Global (CSIC) to MM and CV20- 20089 of the Regional Government of Andalusia to JG.

During the last decade, many studies have demonstrated the role of CMV specific T-cell immune response on controlling CMV replication and dissemination. In fact, it is well established that transplanted patients lacking CMV-specific T-cell immunity have an increased occurrence of CMV replication episodes and CMV-related complications. In this context, the use of adoptive transfer of CMV-specific T-cells has been widely investigated and applied to Hematopoietic Stem Cell Transplant patients and may be useful as a therapeutic alternative, to reconstitute the CMV specific T-cell response and to control CMV viremia in patients receiving a transplantation. However, only few authors have explored the use of T-cell adoptive transfer in SOT recipients. We propose a novel review in which we provide an overview of the impact of using CMV-specific T-cell adoptive transfer on the control of CMV infection in SOT recipients, the different approaches to stimulate, isolate and expand CMV-specific T-cells developed over the years and a discussion of the possible use of CMV adoptive cellular therapy in this SOT population. Given the timeliness and importance of this topic, we believe that such an analysis will provide important insights into CMV infection and its treatment/prevention. This study was supported by the Spanish Ministry of Science, Innovation and University, Instituto de Salud Carlos III Grant/Award Numbers: PI17CIII-00014 (MPY110/18); DTS18CIII/00006 (MPY127/19); PI20-009 (MPY303/20). This work was supported by Plan Nacional de I + D+i 2013‐2016 and Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministry of Science, Innovation and University, Spanish Network for Research in Infectious Diseases (REIPI RD16/0016/0009), co-financed by European Development Regional Fund ‘A way to achieve Europe’. EG-R is supported by the Sara Borrell Program (CD18CIII/00007), Instituto de Salud Carlos III, Ministerio de Ciencia, Innovación y Universidades. FM is supported by the PFIS Program (F18III/00013), Instituto de Salud Carlos III, Ministerio de Ciencia, Innovación y Universidades. MN is supported by the FPU program (FPU19/05927), Ministerio de Ciencia, Innovación y Universidades. Sí

© 2021 Perez-Chacon and Zapata., Chronic lymphocytic leukemia (CLL)/Small lymphocytic lymphoma (SLL) is a heterogeneous disease consisting of at least two separate subtypes, based on the mutation status of the immunoglobulin heavy chain variable gene (IGHV) sequence. Exposure to antigens seems to play a role in malignant transformation and in the selection and expansion of more aggressive CLL clones. Furthermore, a biased usage of particular IGHV gene subgroups and the existence of stereotyped B-cell receptors (BCRs) are distinctive characteristics of human CLL. We have previously described that Traf2DN/BCL2 double-transgenic (tg, +/+) mice develop CLL/SLL with high incidence with aging. In this model, TNF-Receptor Associated Factor (TRAF)-2 deficiency cooperates with B cell lymphoma (BCL)-2 in promoting CLL/SLL in mice by specifically enforcing marginal zone (MZ) B cell differentiation and rendering B cells independent of BAFF for survival. In this report, we have performed the sequencing of the IGHV-D-J rearrangements of B cell clones from the Traf2DN/BCL2-tg+/+ mice with CLL/SLL. The results indicate that these mice develop oligoclonal and monoclonal B cell expansions. Allotransplantation of the oligoclonal populations into immunodeficient mice resulted in the preferential expansion of one of the parental clones. The analysis of the IGHV sequences indicated that 15% were mutated (M) and 85% unmutated (UM). Furthermore, while the Traf2DN/BCL2-tg-/- (wild-type), -/+ (BCL2 single-tg) and +/- (Traf2DNDN single-tg) littermates showed the expression of various IGHV gene subgroups, the CLL/SLL expanded clones from the Traf2DN/BCL2-tg+/+ (double-transgenic) mice showed a more restricted IGHV gene subgroup usage and an overrepresentation of particular IGHV genes. In addition, the HCDR3-encoded protein sequence indicates the existence of stereotyped immunoglobulin (Ig) in the BCRs and strong similarities with BCR recognizing autoantigens and pathogen-associated antigens. Altogether, these results highlight the remarkable similarities between the CLL/SLL developed by the Traf2DN/BCL2-tg+/+ mice and its human counterpart., This work was supported by grants from the Agencia Estatal de Investigacion (PID2019-110405RB-I00/AEI/10.13039/501100011033) and from the Instituto de Salud Carlos III (PI16/000895). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). The cost of this publication was paid in part by FEDER funds.

© 2021 Jaén, Sánchez-García, Fernández-Velasco, Boscá and Prieto., Inflammation is an a physiological response instead an essential response of the organism to injury and its adequate resolution is essential to restore homeostasis. However, defective resolution can be the precursor of severe forms of chronic inflammation and fibrosis. Nowadays, it is known that an excessive inflammatory response underlies the most prevalent human pathologies worldwide. Therefore, great biomedical research efforts have been driven toward discovering new strategies to promote the resolution of inflammation with fewer side-effects and more specificity than the available anti-inflammatory treatments. In this line, the use of endogenous specialized pro-resolving mediators (SPMs) has gained a prominent interest. Among the different SPMs described, lipoxins stand out as one of the most studied and their deficiency has been widely associated with a wide range of pathologies. In this review, we examined the current knowledge on the therapeutic potential of lipoxins to treat diseases characterized by a severe inflammatory background affecting main physiological systems, paying special attention to the signaling pathways involved. Altogether, we provide an updated overview of the evidence suggesting that increasing endogenously generated lipoxins may emerge as a new therapeutic approach to prevent and treat many of the most prevalent diseases underpinned by an increased inflammatory response., This work was supported by Ministerio de Economıa, Industria y ́ Competitividad, Ministerio de Ciencia, Investigación y Universidades, and Agencia Estatal de Investigación (SAF2017-82436R), Centro de Investigación Biomédica en Red en Enfermedades Cardiovasculares (CB16/11/00222), Consorcio de Investigación en Red de la Comunidad de Madrid, S2017/BMD-3686 and Fondo Europeo de Desarrollo Regional. RI holds a FPU PhD fellowship of the Ministerio de Ciencia, Investigación y Universidades (FPU16/00827).

19 Pág. Centro de Investigación en Sanidad Animal (CISA), Probiotics have been defined as live microorganisms that when administered in adequate amounts confer health benefits to the host. The use of probiotics in aquaculture is an attractive bio-friendly method to decrease the impact of infectious diseases, but is still not an extended practice. Although many studies have investigated the systemic and mucosal immunological effects of probiotics, not all of them have established whether they were actually capable of increasing resistance to different types of pathogens, being this the outmost desired goal. In this sense, in the current paper, we have summarized those experiments in which probiotics were shown to provide increased resistance against bacterial, viral or parasitic pathogens. Additionally, we have reviewed what is known for fish probiotics regarding the mechanisms through which they exert positive effects on pathogen resistance, including direct actions on the pathogen, as well as positive effects on the host., This work was supported by the European Research Council (ERC Consolidator Grant 2016 725061 TEMUBLYM), by the Spanish Ministry of Science, Innovation and Universities (project AGL2017-85494-C2-1-R) and by the Comunidad de Madrid (grant 2016-T1/BIO-1672).

© 2021 Piazzon, Mladineo, Dirks, Santidrián Yebra-Pimentel, Hrabar and Sitjà-Bobadilla., Ceratothoa oestroides (Cymothoidea, Isopoda) is a generalist crustacean parasite that negatively affects the economic sustainability of European sea bass (Dicentrarchus labrax) aquaculture in the North-East Mediterranean. While mortalities are observed in fry and fingerlings, infection in juvenile and adult fish result in approximately 20% growth delay. A transcriptomic analysis (PCR array, RNA-Seq) was performed on organs (tongue, spleen, head kidney, and liver) from infected vs. Ceratothoa-free sea bass fingerlings. Activation of local and systemic immune responses was detected, particularly in the spleen, characterized by the upregulation of cytokines (also in the tongue), a general reshaping of the immunoglobulin (Ig) response and suppression of T-cell mediated responses. Interestingly, starvation and iron transport and metabolism genes were strongly downregulated, suggesting that the parasite feeding strategy is not likely hematophagous. The regulation of genes related to growth impairment and starvation supported the growth delay observed in infected animals. Most differentially expressed (DE) transcripts were exclusive of a specific organ; however, only in the tongue, the difference between infected and uninfected fish was significant. At the attachment/feeding site, the pathways involved in muscle contraction and intercellular junction were the most upregulated, whereas the pathways involved in fibrosis (extracellular matrix organization, collagen formation, and biosynthesis) were downregulated. These results suggest that parasite-inflicted damage is successfully mitigated by the host and characterized by regenerative processes that prevail over the reparative ones., This work was funded by the EU H2020 program through the ParaFishControl Project (634429). This publication reflects only the authors' views and the European Union cannot be held responsible for any use that may be made of the information contained herein. MCP was funded by a Ramón y Cajal Postdoctoral Research Fellowship (RYC2018-024049-I/AEI/10.13039/501100011033 co-funded by the European Social Fund (ESF) & ACOND/2020 Generalitat Valenciana). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)

Dendrimeric peptide constructs based on a lysine core that comprises both B- and T-cell epitopes of foot-and-mouth disease virus (FMDV) have proven a successful strategy for the development of FMD vaccines. Specifically, BT dendrimers displaying two copies of the major type O FMDV antigenic B-cell epitope located on the virus capsid [VP1 (140–158)], covalently linked to a heterotypic T-cell epitope from either non-structural protein 3A [3A (21–35)] or 3D [3D (56–70)], named BT-3A and BT-3D, respectively, elicit high levels of neutralizing antibodies (nAbs) and IFN-γ-producing cells in pigs. To assess whether the inclusion and orientation of T-3A and T-3D T-cell epitopes in a single molecule could modulate immunogenicity, dendrimers with T epitopes juxtaposed in both possible orientations, i.e., constructs BTT-3A3D and BTT-3D3A, were made and tested in pigs. Both dendrimers elicited high nAbs titers that broadly neutralized type O FMDVs, although BTT-3D3A did not respond to boosting, and induced lower IgGs titers, in particular IgG2, than BTT-3A3D. Pigs immunized with B a control dendrimer displaying two B-cell epitope copies and no T-cell epitope, gave no nABs, confirming T-3A and T-3D as T helper epitopes. The T-3D peptide was found to be an immunodominant, as it produced more IFN-γ expressing cells than T-3A in the in vitro recall assay. Besides, in pigs immunized with the different dendrimeric peptides, CD4 T-cells were the major subset contributing to IFN-γ expression upon in vitro recall, and depletion of CD4 cells from PBMCs abolished the production of this cytokine. Most CD4IFN-γ cells showed a memory (CD42E3) and a multifunctional phenotype, as they expressed both IFN-γ and TNF-α, suggesting that the peptides induced a potent Th1 pro-inflammatory response. Furthermore, not only the presence, but also the orientation of T-cell epitopes influenced the T-cell response, as BTT-3D3A and B groups had fewer cells expressing both cytokines. These results help understand how BT-type dendrimers triggers T-cell populations, highlighting their potential as next-generation FMD vaccines., Spanish Ministry of Science, Innovation and Universities grants AGL2014-48923-C2 and AGL2017-89097-C2-2-R (to FS and DA) and AGL2016-349 76445-R to EB), as well as by Comunidad de Madrid co-financed with ECFEDER funds (S2013/ABI-350 2906-PLATESA and P2018/BAA-4370 to FS and EB) and by Generalitat de Catalunya (2009SGR492 to DA). Work at Centro de Biologı́a Molecular “Severo Ochoa” and at UPF was supported by Fundación Ramón Areces

© 2020 Valle-Noguera, Gómez-Sánchez, Girard-Madoux and Cruz-Adalia., Since their discovery, innate lymphoid cells (ILCs) have gradually been gaining greater relevance in the field of immunology due to their multiple functions in the innate immune response. They can mainly be found in mucosal and barrier organs like skin, gut, and lungs, and have been classified into five main types (NKs, ILC1s, ILC2s, ILC3s, and Lti cells) according to their function and development. They all play major roles in functions such as tissue homeostasis, early pathogen defense, regulation of inflammation, or tissue remodeling. ILCs are mostly tissue-resident cells tightly bound to the tissue structure, a fact that requires long and complex protocols that do not always provide sufficient yield for analysis. This suggests the need for optimized approaches aimed at ensuring that enriched and viable ILC samples are obtained, in order to furnish quality results. Herein a detailed protocol is established for obtaining a single-cell suspension highly enriched in lymphoid cells from mouse gut in order to identify the different subsets of ILCs by means of flow cytometry. The cell marker panel and flow cytometry gating strategies for identification and quantification of all the different ILC populations are provided for simultaneous analysis. Moreover, the protocol described includes a procedure for studying the different cytokines produced by ILC3s involved in maintaining the integrity of the gut barrier and defending against extracellular pathogens. As a result, herein an efficient method is presented for studying mouse ILCs within the lamina propria of the small intestine and colon; this can constitute a useful tool for future investigations in the field., The present research was supported by grant Nº RTI2018-093647-B-I00 to AC-A from Ministerio de Ciencia, Innovación e Universidades (MCIU), Agenda Estatal de Investigación (AEI), and Fondo Europeo de Desarrollo Regional (FEDER). AV-N is a recipient of an FPI fellowship (PRE2019-090341) from the Spanish Ministry of Science, Innovation, and Universities.

© 2020 Rodríguez-Fernández, Mellado, Thelen and Murphy., Chemoattraction is a process that involves directed cell movement toward extracellular chemical stimuli. It is a fundamental feature of all biological systems that was discovered in the late nineteenth century, when the word “chemotaxis” was coined by the German biologist Wilhelm Pfeffer. Metchnikoff’s 1882 description of macrophages from starfish larvae migrating toward an implanted rose thorn irritant represents a seminal observation of chemoattraction in vivo. Since then immunologists have described many chemoattractants, including nucleotides, adenosine, lipids (e.g., leukotrienes, prostaglandins, and platelet-activating factor), proteolytic fragments of complement proteins (e.g., C3a and C5a), small peptides (e.g., N-formyl peptides), and small proteins (e.g., chemokines, non-chemokine cytokines, and defensins). Chemokines comprise the largest known group of chemoattractants (1, 2)., Work supported by grants SAF2017-83306-R (MICIU) and RIER (RETICS Program/ISCIII) (RD08/0075) (JLR-F); grants SAF2017-82940-R AEI/FEDER, UE and RD12/0012/0006 (RETICS Program/ISCIII) (MM); grants from the SNSF (310030_163336/1 and Sinergia CRSII3_160719) and Helmut Horten Foundation (MT); and supported in part by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH (PMM).

© 2020 Martınez-Rey, Carmona-Rodríguez, Fernández-Aceñero, Mira and Santos Mañes., Tumor-infiltrating lymphocytes (TILs) are major players in the immune-mediated control of cancer and the response to immunotherapy. In primary cancers, however, TILs are commonly absent, suggesting T-cell entry into the tumor microenvironment (TME) to be selectively restricted. Blood and lymph vessels are the first barriers that circulating T-cells must cross to reach the tumor parenchyma. Certainly, the crossing of the endothelial cell (EC) basement membrane (EC-BM)—an extracellular matrix underlying EC—is a limiting step in T-cell diapedesis. This review highlights new data suggesting the antioxidant enzyme superoxide dismutase-3 (SOD3) to be a regulator of EC-BM composition in the tumor vasculature. In the EC, SOD3 induces vascular normalization and endows the EC-BM with the capacity for the extravasation of effector T-cells into the TME, which it achieves via the WNT signaling pathway. However, when activated in tumor cells, this same pathway is reported to exclude TILs. SOD3 also regulates TIL density in primary human colorectal cancers (CRC), thus affecting the relapse rate and patient survival., This work was funded by the Spanish Ministry of Science, Innovation and Universities (SAF2017-83732-R; AEI/FEDER, EU), the Comunidad de Madrid (B2017/BMD-3733; InmunothercanCM), and the Fundación Domingo Martínez and the Fundacioń Merck-Salud. DM-R was supported by a predoctoral fellowship from the Spanish Ministry of Science, Innovation and Universities and the EU European Social Fund (PRE2018-084023).

1 figure, 1 table, Sepsis is a serious global health problem. In addition to a high incidence, this syndrome has a high mortality and is responsible for huge health expenditure. The pathophysiology of sepsis is very complex and it is not well-understood yet. However, it is widely accepted that the initial phase of sepsis is characterized by a hyperinflammatory response while the late phase is characterized by immunosuppression and immune anergy, increasing the risk of secondary infections. Granzymes (Gzms) are a family of serine proteases classified according to their cleavage specificity. Traditionally, it was assumed that all Gzms acted as cytotoxic proteases. However, recent evidence suggests that GzmB is the one with the greatest cytotoxic capacity, while the cytotoxicity of others such as GzmA and GzmK is not clear. Recent studies have found that GzmA, GzmB, GzmK, and GzmM act as pro-inflammatory mediators. Specially, solid evidences show that GzmA and GzmK function as extracellular proteases that regulate the inflammatory response irrespectively of its ability to induce cell death. Indeed, studies in animal models indicate that GzmA is involved in the cytokine release syndrome characteristic of sepsis. Moreover, the GZM family also could regulate other biological processes involved in sepsis pathophysiology like the coagulation cascade, platelet function, endothelial barrier permeability, and, in addition, could be involved in the immunosuppressive stage of sepsis. In this review, we provide a comprehensive overview on the contribution of these novel functions of Gzms to sepsis and the new therapeutic opportunities emerging from targeting these proteases for the treatment of this serious health problem., This work was supported in part by FEDER/Gobierno de Aragón (group B29), Ministerio de Economia y Competitividad [SAF2014-54763-C2-1 and SAF2017-83120-C2-1-R (JP-P), SAF2014-54763-C2-2-R (EG)] and Instituto de Salud Carlos III (PI16-00526, LM-L; PI18/00527, JP-P). Predoctoral grants/contracts from Fundacion Santander/Universidad de Zaragoza (LS and MA), Ministerio de Ciencia, Innovación y Universidades (MG-T). MA has a Juan de la Cierva Contract (Ministerio de Ciencia, Innovación y Universidades) and JS-M a Rio Hortega Contract (Instituto de Salud Carlos III). JP was supported by Fundación Aragon I+D (ARAID).

Background: Primary immunodeficiencies (PIDs) are a heterogeneous group of disorders. The lack of comprehensive disease-specific mutation databases may hinder or delay classification of the genetic variants found in samples from these patients. This is especially true for familial hemophagocytic lymphohistiocytosis (FHL), a life-threatening PID classically considered an autosomal recessive condition, but with increasingly demonstrated genetic heterogeneity. Objective: The aim of this study was to build an open-access repository to collect detailed information on the known genetic variants reported in FHL. Methods: We manually reviewed more than 120 articles to identify all reported variants related to FHL. We retrieved relevant information about the allelic status, the number of patients with the same variant, and whether functional assays were done. We stored all the data retrieved in a PostgreSQL database and then built a website on top of it, using the Django framework. Results: The database designed (FHLdb) (https://www.biotoclin.org/FHLdb) contains comprehensive information on reported variants in the 4 genes related to FHL (PRF1, UNC13D, STXBP2, STX11). It comprises 240 missense, 69 frameshift, 51 nonsense, 51 splicing, 10 in-frame indel, 7 deep intronic, and 5 large rearrangement variants together with their allelic status, carrier(s) information, and functional evidence. All genetic variants have been classified as pathogenic, likely pathogenic, uncertain significance, likely benign or benign, according to the American College of Medical Genetics guidelines. Additionally, it integrates information from other relevant databases: clinical evidence from ClinVar and UniProt, population allele frequency from ExAC and gnomAD, and pathogenicity predictions from well-recognized tools (e.g., PolyPhen-2, SIFT). Finally, a diagram depicts the location of the variant relative to the gene exon and protein domain structures. Conclusion: FHLdb includes a broad range of data on the reported genetic variants in familial HLH genes. It is a free-access and easy-to-use resource that will facilitate the interpretation of molecular results of FHL patients, and it illustrates the potential value of disease-specific databases for other PIDs., This study was funded by Instituto de Salud Carlos III, grants PI17/00660 and PI18/00346, cofinanced by the European Regional Development Fund (ERDF). LB-M is supported by a Formació de Personal Investigador (FPI) fellowship from Generalitat de Catalunya (2018_FI_B00072). FC was funded by grants SAF2015-68472-C2-2-R from the Ministerio de Economía y Competitividad (Spain) and FEDER (EU) and RTI2018- 096824-B-C22 from the Spanish Ministry of Science, Innovation and Universities co-financed by ERDF (FC), and by Direcció General de Recerca, Generalitat de Catalunya (2014SGR-866 and 2017SGR-702).

Myeloid C-type lectin receptors (CLRs) comprise a family of receptors expressed by immune myeloid cells that share homologous C-type lectin domains. The implication of these CLRs in the regulation of homeostasis and activation of myeloid cells has generated a buoyant growth in the number of studies involving these receptors. Since their first description, diverse nomenclature has been used to refer to each of them, ranging from systematic classifications, such as gene name or cluster of differentiation, to non-systematic ones that include terminology based on gene expression patterns or function. In this review, we aim to summarize the different names used for the main myeloidCLRs and analyzewhich of themhave beenmore frequently used in the literature. In addition, we have examined the evolution of the terminology applied to these myeloid CLRs over time. Based on this analysis, we propose a consensus alias for each of those myeloid CLRs. However, we acknowledge that systematicity is required beyond this terminology based on use frequency. Therefore, we have included gene names as the standardization tool to gather the maximum agreement. We suggest that a standard nomenclature consisting of both gene names and consensus alias should be included at least in scientific abstracts, which would help to identify relevant literature, saving time and effort and fostering the research in this field in a more systematic manner. CF was supported by AECC Foundation (INVES192DELF). Work in the DS laboratory was funded by the CNIC and grant SAF2016-79040-R from Ministerio de Ciencia, Innovacion e Universidades (MCIU), Agencia Estatal de Investigacion and Fondo Europeo de Desarrollo Regional (FEDER); B2017/BMD-3733 Immunothercan-CM from Comunidad de Madrid; RD16/0015/0018-REEM from FIS-Instituto de Salud Carlos III, MICINN, and FEDER; Acteria Foundation; Constantes y Vitales prize (Atresmedia); La Marato de TV3 Foundation (201723); the European Research Council (ERC-2016-Consolidator Grant 725091); and the European Commission (635122-PROCROP H2020). The CNIC is supported by the MCIU and the Pro-CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Sí

Type 1 diabetes (T1D) is prompted by defective immunological tolerance, an event in which dendritic cells (DCs) are crucial as immune response orchestrators. In fact, they contribute to maintaining tolerance to self-antigens, but they can also prompt an immunogenic response against them, leading to autoimmunity. Countless factors can potentially impact on the proper functionality of the DCs, which range from altered subset distribution, impaired phagocytic function to abnormal gene expression. Moreover, in T1D, metabolic dysregulation could impair DC functions as well. Indeed, since T1D clinical course is likely to be more aggressive in children and adolescents and entails severe dysglycemia, the aim of this study was to analyze circulating DCs subpopulations in pediatric T1D at different stages, as well as to characterize their phagocytosis ability and tolerance induction potential. Thus, pediatric patients newly diagnosed with T1D, with established disease and control subjects were recruited. Firstly, DCs subsets from peripheral blood were found quantitatively altered during the first year of disease, but recovered in the second year of progression. Secondly, to study the tolerogenic functionality of DCs, liposomes with phosphatidylserine (PS) were designed to mimic apoptotic beta cells, which are able to induce tolerance, as previously demonstrated by our group in DCs from adult patients with T1D. In this study, monocyte-derived DCs from pediatric patients with T1D and control subjects were assessed in terms of PS-liposomes capture kinetics, and transcriptional and phenotypic changes. DCs from pediatric patients with T1D were found to phagocyte PS-liposomes more slowly and less efficiently than DCs from control subjects, inversely correlating with disease evolution. Nonetheless, the transcription of PS receptors and immunoregulatory genes, cytokine profile, and membrane expression of immunological markers in DCs was consistent with tolerogenic potential after PS-liposomes phagocytosis. In conclusion, T1D progression in childhood entails altered peripheral blood DCs subsets, as well as impaired DCs phagocytosis, although tolerance induction could still function optimally. Therefore, this study provides useful data for patient follow-up and stratification in immunotherapy clinical trials., This work has been funded by the Spanish Government (FIS PI15/00198 and PI18/00436) co-financed with the European Regional Development funds (FEDER), and by DiabetesCero Foundation. CIBER of Diabetes and Associated Metabolic Diseases (CIBERDEM) is an initiative from Instituto de Salud Carlos III (Spain). SR-F was supported by the Agency for Management of University and Research Grants (AGAUR) of the Generalitat de Catalunya. ICN2 was supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706).

15 pages, 8 figures, 3 tables, Mediterranean mussels (Mytilus galloprovincialis) are sessile filter feeders that live in close contact with numerous marine microorganisms. As is the case in all invertebrates, mussels lack an adaptive immune system, but they respond to pathogens, injuries or environmental stress in a very efficient manner. However, it is not known if they are able to modify their immune response when they reencounter the same pathogen. In this work, we studied the transcriptomic response of mussel hemocytes before and after two consecutive sublethal challenges with Vibrio splendidus. The first exposure significantly regulated genes related to inflammation, migration and response to bacteria. However, after the second exposure, the differentially expressed genes were related to the control and inhibition of ROS production and the resolution of the inflammatory response. Our results also show that the second injection with V. splendidus led to changes at the transcriptional (control of the expression of pro-inflammatory transcripts), cellular (shift in the hemocyte population distribution), and functional levels (inhibition of ROS production). These results suggest that a modified immune response after the second challenge allowed the mussels to tolerate rather than fight the infection, which minimized tissue damage., This work was conducted with the support of the projects AGL2015-65705-R and RTI2018-095997-B-I00 (Ministerio de Ciencia, Innovación y Universidades, Spain), IN607B 2016/12 (Consellería de Economía, Emprego e Industria-GAIN, Xunta de Galicia), and VIVALDI (678589) (EU H2020). MR-C acknowledges additional funding from the Spanish Ministerio de Economía y Competitividad for her predoctoral contract (BES2016-076302).

Dendritic cells (DCs) control innate and adaptive immunity by patrolling tissues to gather antigens and danger signals derived from microbes and tissue. Subsequently, DCs integrate those environmental cues, orchestrate immunity or tolerance, and regulate tissue homeostasis. Recent advances in the field of immunometabolism highlight the notion that immune cells markedly alter cellular metabolic pathways during differentiation or upon activation, which has important implications on their functionality. Previous studies showed that active oxidative phosphorylation in mitochondria is associated with immature or tolerogenic DCs, while increased glycolysis upon pathogen sensing can promote immunogenic DC functions. However, new results in the last years suggest that regulation of DC metabolism in steady state, after immunogenic activation and during tolerance in different pathophysiological settings, may be more complex. Moreover, ontogenically distinct DC subsets show different functional specializations to control T cell responses. It is, thus, relevant how metabolism influences DC differentiation and plasticity, and what potential metabolic differences exist among DC subsets. Better understanding of the emerging connection between metabolic adaptions and functional DC specification will likely allow the development of therapeutic strategies to manipulate immune responses. The DS laboratory is funded by the CNIC and grant SAF2016-79040-R from Ministerio de Ciencia, Innovacione Universidades (MCIU), Agencia Estatal de Investigacion, and Fondo Europeo de Desarrollo Regional (FEDER); B2017/BMD-3733 Immunothercan-CM from Comunidad de Madrid; RD16/0015/0018-REEM from FIS-Instituto de Salud Carlos III, MICINN, and FEDER; Acteria Foundation; Constantes y Vitales prize (Atresmedia); La Marato de TV3 Foundation (201723); the European Commission (635122-PROCROP H2020); and the European Research Council (ERC-2016-Consolidator Grant 725091). SKW is supported by a European Molecular Biology Organization Long-term Fellowship (grant ALTF 438-2016) and a CNIC-International Postdoctoral Program Fellowship (grant 17230-2016). SCK is a recipient of a FPU fellowship (FPU16/03142) from the Spanish Ministry of Education, Culture and Sports. EP is supported by a predoctoral grant from the Spanish Ministry of Economy and Competitiveness (BES-2017-079717). IH-M receives the support of a fellowship from la Caixa Foundation (ID 100010434, fellowship code: LCF/BQ/IN17/11620074) and from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 713673. The CNIC is supported by the MCIU and the Pro-CNIC Foundation and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Sí

CD137 (4-1BB, Tnsfr9) is a member of the TNF-receptor (TNFR) superfamily without known intrinsic enzymatic activity in its cytoplasmic domain. Hence, akin to other members of the TNFR family, it relies on the TNFR-Associated-Factor (TRAF) family of adaptor proteins to build the CD137 signalosome for transducing signals into the cell. Thus, upon CD137 activation by binding of CD137L trimers or by crosslinking with agonist monoclonal antibodies, TRAF1, TRAF2, and TRAF3 are readily recruited to the cytoplasmic domain of CD137, likely as homo- and/or heterotrimers with different configurations, initiating the construction of the CD137 signalosome. The formation of TRAF2-RING dimers between TRAF2 molecules from contiguous trimers would help to establish a multimeric structure of TRAF-trimers that is probably essential for CD137 signaling. In addition, available studies have identified a large number of proteins that are recruited to CD137:TRAF complexes including ubiquitin ligases and proteases, kinases, and modulatory proteins. Working in a coordinated fashion, these CD137-signalosomes will ultimately promote CD137-mediated T cell proliferation and survival and will endow T cells with stronger effector functions. Current evidence allows to envision the molecular events that might take place in the early stages of CD137-signalosome formation, underscoring the key roles of TRAFs and of K63 and K48-ubiquitination of target proteins in the signaling process. Understanding the composition and fine regulation of CD137-signalosomes assembly and disassembly will be key to improve the therapeutic activities of chimeric antigen receptors (CARs) encompassing the CD137 cytoplasmic domain and a new generation of CD137 agonists for the treatment of cancer., Funding was from Instituto de Salud Carlos III (ISCIII) (PI16/00895 to JZ), Ministerio de Economía y Competitividad (MINECO) RTC-16-5118-1 to JZ and IM, SAF 2014-52361-R and SAF 2017-83267-C2-1R to IM; and Cancer Research Institute (CRI) CLIP Grant 2017, Asociación Española Contra el Cancer, Fundación BBVA and I-ON Network-BMS to IM. The cost of this publication was paid in part by funds from the European Fund for Economic and Regional Development (FEDER).

Four inflammatory diseases are strongly associated with Major Histocompatibility Complex class I (MHC-I) molecules: birdshot chorioretinopathy (HLA-A*29:02), ankylosing spondylitis (HLA-B*27), Behçet's disease (HLA-B*51), and psoriasis (HLA-C*06:02). The endoplasmic reticulum aminopeptidases (ERAP) 1 and 2 are also risk factors for these diseases. Since both enzymes are involved in the final processing steps of MHC-I ligands it is reasonable to assume that MHC-I-bound peptides play a significant pathogenetic role. This review will mainly focus on recent studies concerning the effects of ERAP1 and ERAP2 polymorphism and expression on shaping the peptidome of disease-associated MHC-I molecules in live cells. These studies will be discussed in the context of the distinct mechanisms and substrate preferences of both enzymes, their different patterns of genetic association with various diseases, the role of polymorphisms determining changes in enzymatic activity or expression levels, and the distinct peptidomes of disease-associated MHC-I allotypes. ERAP1 and ERAP2 polymorphism and expression induce significant changes in multiple MHC-I-bound peptidomes. These changes are MHC allotype-specific and, without excluding a degree of functional inter-dependence between both enzymes, reflect largely separate roles in their processing of MHC-I ligands. The studies reviewed here provide a molecular basis for the distinct patterns of genetic association of ERAP1 and ERAP2 with disease and for the pathogenetic role of peptides. The allotype-dependent alterations induced on distinct peptidomes may explain that the joint association of both enzymes and unrelated MHC-I alleles influence different pathological outcomes., Ministry of Science, Innovation, and Universities of the Government of Spain and by an institutional grant of the Fundación Ramón Areces to the CBMSO

GM-CSF promotes the functional maturation of lung alveolar macrophages (A-MØ), whose differentiation is dependent on the peroxisome proliferator-activated receptor gamma (PPARγ) transcription factor. In fact, blockade of GM-CSF-initiated signaling or deletion of the PPARγ-encoding gene PPARG leads to functionally defective A-MØ and the onset of pulmonary alveolar proteinosis. In vitro, macrophages generated in the presence of GM-CSF display potent proinflammatory, immunogenic and tumor growth-limiting activities. Since GM-CSF upregulates PPARγ expression, we hypothesized that PPARγ might contribute to the gene signature and functional profile of human GM-CSF-conditioned macrophages. To verify this hypothesis, PPARγ expression and activity was assessed in human monocyte-derived macrophages generated in the presence of GM-CSF [proinflammatory GM-CSF-conditioned human monocyte-derived macrophages (GM-MØ)] or M-CSF (anti-inflammatory M-MØ), as well as in ex vivo isolated human A-MØ. GM-MØ showed higher PPARγ expression than M-MØ, and the expression of PPARγ in GM-MØ was found to largely depend on activin A. Ligand-induced activation of PPARγ also resulted in distinct transcriptional and functional outcomes in GM-MØ and M-MØ. Moreover, and in the absence of exogenous activating ligands, PPARγ knockdown significantly altered the GM-MØ transcriptome, causing a global upregulation of proinflammatory genes and significantly modulating the expression of genes involved in cell proliferation and migration. Similar effects were observed in ex vivo isolated human A-MØ, where PPARγ silencing led to enhanced expression of genes coding for growth factors and chemokines and downregulation of cell surface pathogen receptors. Therefore, PPARγ shapes the transcriptome of GM-CSF-dependent human macrophages (in vitro derived GM-MØ and ex vivo isolated A-MØ) in the absence of exogenous activating ligands, and its expression is primarily regulated by activin A. These results suggest that activin A, through enhancement of PPARγ expression, help macrophages to switch from a proinflammatory to an anti-inflammatory polarization state, thus contributing to limit tissue damage and restore homeostasis., This work was supported by grants from Ministerio de Economía y Competitividad (SAF2014-54423-R and SAF2017-83785-R to MAV and ALC, SAF2014-56819-R and SAF2015-71878-REDT to AC, and SAF2015-69905 to CA), Comunidad Autónoma de Madrid/FEDER (RAPHYME S2010/BMD-2350 to ALC, AP-K and AC), Instituto de Salud Carlos III (PI14/00075, PI17/00037 and Red de Investigación en Enfermedades Reumáticas, RIER RD16/0012/0007 to AP-K), and cofinanced by the European Regional Development Fund “A way to achieve Europe” (ERDF).

DNGR-1 (encoded by CLEC9A) is a C-type lectin receptor (CLR) with an expression profile that is mainly restricted to type 1 conventional dendritic cells (cDC1s) both in mice and humans. This delimited expression pattern makes it appropriate for defining a cDC1 signature and for therapeutic targeting of this population, promoting immunity in mouse models. Functionally, DNGR-1 binds F-actin, which is confined within the intracellular space in healthy cells, but is exposed when plasma membrane integrity is compromised, as happens in necrosis. Upon F-actin binding, DNGR-1 signals through SYK and mediates cross-presentation of dead cell-associated antigens. Cross-presentation to CD8+ T cells promoted by DNGR-1 during viral infections is key for cross-priming tissue-resident memory precursors in the lymph node. However, in contrast to other closely related CLRs such as Dectin-1, DNGR-1 does not activate NFκB. Instead, recent findings show that DNGR-1 can activate SHP-1 to limit inflammation triggered by heterologous receptors, which results in reduced production of inflammatory chemokines and neutrophil recruitment into damaged tissues in both sterile and infectious processes. Hence, DNGR-1 reduces immunopathology associated with tissue damage, promoting disease tolerance to safeguard tissue integrity. How DNGR-1 signals are conditioned by the microenvironment and the detailed molecular mechanisms underlying DNGR-1 function have not been elucidated. Here, we review the expression pattern and structural features of DNGR-1, and the biological relevance of the detection of tissue damage through this CLR. FC was a recipient of a PhD La Caixa fellowship (LCF/BQ/ES14/10320011). CF was supported by AECC Foundation (INVES192DELF). Work in the DS laboratory was funded by the CNIC; by the European Research Council (ERC-2016-Consolidator Grant 725091); by the European Commission (635122-PROCROP H2020); by Ministerio de Ciencia, Innovación e Universidades (MICINN), Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional (FEDER) (SAF2016-79040-R); by Comunidad de Madrid (B2017/BMD-3733 Immunothercan-CM); by FIS-Instituto de Salud Carlos III, MICINN and FEDER (RD16/0015/0018-REEM); by Acteria Foundation; by Atresmedia (Constantes y Vitales prize); and by Fundació La Marató de TV3 (201723). The CNIC was supported by the Instituto de Salud Carlos III (ISCIII), the MICINN, and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Sí