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The transactive response DNA-binding protein (TARDBP/TDP-43) is known to stabilize the anti-HIV-1 factor, histone deacetylase 6 (HDAC6). TDP-43 has been reported to determine cell permissivity to HIV-1 fusion and infection acting on tubulin-deacetylase HDAC6. Here, we studied the functional involvement of TDP-43 in the late stages of the HIV-1 viral cycle. The overexpression of TDP-43, in virus-producing cells, stabilized HDAC6 (i.e., mRNA and protein) and triggered the autophagic clearance of HIV-1 Pr55Gag and Vif proteins. These events inhibited viral particle production and impaired virion infectiveness, observing a reduction in the amount of Pr55Gag and Vif proteins incorporated into virions. A nuclear localization signal (NLS)-TDP-43 mutant was not able to control HIV-1 viral production and infection. Likewise, specific TDP-43-knockdown reduced HDAC6 expression (i.e., mRNA and protein) and increased the expression level of HIV-1 Vif and Pr55Gag proteins and α-tubulin acetylation. Thus, TDP-43 silencing favored virion production and enhanced virus infectious capacity, thereby increasing the amount of Vif and Pr55Gag proteins incorporated into virions. Noteworthy, there was a direct relationship between the content of Vif and Pr55Gag proteins in virions and their infection capacity. Therefore, for TDP-43, the TDP-43/HDAC6 axis could be considered a key factor to control HIV-1 viral production and virus infectiveness.

The transactive response DNA-binding protein (TARDBP/TDP-43) influences the processing of diverse transcripts, including that of histone deacetylase 6 (HDAC6). Here, we assessed TDP-43 activity in terms of regulating CD4+ T-cell permissivity to HIV-1 infection. We observed that overexpression of wt-TDP-43 increased both mRNA and protein levels of HDAC6, resulting in impaired HIV-1 infection independently of the viral envelope glycoprotein complex (Env) tropism. Consistently, using an HIV-1 Env-mediated cell-to-cell fusion model, the overexpression of TDP-43 levels negatively affected viral Env fusion capacity. Silencing of endogenous TDP-43 significantly decreased HDAC6 levels and increased the fusogenic and infection activities of the HIV-1 Env. Using pseudovirus bearing primary viral Envs from HIV-1 individuals, overexpression of wt-TDP-43 strongly reduced the infection activity of Envs from viremic non-progressors (VNP) and rapid progressors (RP) patients down to the levels of the inefficient HIV-1 Envs observed in long-term non-progressor elite controllers (LTNP-EC). On the contrary, silencing endogenous TDP-43 significantly favored the infectivity of primary Envs from VNP and RP individuals, and notably increased the infection of those from LTNP-EC. Taken together, our results indicate that TDP-43 shapes cell permissivity to HIV-1 infection, affecting viral Env fusion and infection capacities by altering the HDAC6 levels and associated tubulin-deacetylase anti-HIV-1 activity. This work is supported by the Spanish AIDS network “Red Temática Cooperativa de Investigación en SIDA” RD12/0017/0002, RD12/0017/0028, RD12/0017/0034, RD16/0025/0011, RDCIII16/0002/0005 and RD16/0025/0041 as part of the Plan Nacional R + D+I and co-funded by the Spanish “Instituto de Salud Carlos III (ISCIII)-Subdirección General de Evaluación y el Fondo Europeo de Desarrollo Regional (FEDER)”. J.B. is a researcher from “Fundació Institut de Recerca en Ciències de la Salut Germans Trias i Pujol” supported by the Health Department of the Catalonian Government/Generalitat de Catalunya and ISCIII grant numbers PI17/01318 and PI20/00093 (to J.B.). Work in CC Lab was supported by grants SAF (2010-17226) and (2016-77894-R) from MINECO (Spain), FIS (PI 13/02269, ISCIII) and PI20/00093. Work in CF Lab was supported by the Cabildo Insular de Tenerife (grants CGIEU0000219140 and “Apuestas científicas del ITER para colaborar en la lucha contra la COVID-19”); the agreement with the Instituto Tecnológico y de Energías Renovables (ITER) to strengthen scientific and technological education, training research, development and innovation in Genomics, Personalized Medicine and Biotechnology (grant number OA17/008). A.V.-F.’s Lab is supported by the European Regional Development Fund (ERDF), RTI2018-093747-B-100 (“Ministerio de Ciencia e Innovación”, Spain), “Ministerio de Ciencia, Innovación y Universidades” (Spain), ProID2020010093 (“Agencia Canaria de Investigación, Innovación y Sociedad de la Información” and European Social Fund), UNLL10-3E-783 (ERDF and “Fundación CajaCanarias”) and “SEGAI-ULL”. S.P-Y is funded by “Fundación Doctor Manuel Morales” (La Palma, Spain) and “Contrato Predoctoral Ministerio-ULL Formación de Doctores” (2019 Program) (“Ministerio de Ciencia, Innovación y Universidades”, Spain). R.C.-R. is funded by RD16/0025/0011 and ProID2020010093 (“Agencia Canaria de Investigación, Innovación y Sociedad de la Información” and European Social Fund). J.G.-L. is funded by the “Juan de la Cierva de Incorporación” Spanish Program (IJC2019-038902-I) (“Ayudas Juan de la Cierva de incorporación; Agencia Estatal de Investigación. Ministerio de Ciencia e Innovación”). Sí

The transactive response DNA-binding protein (TDP-43) is an important regulator of mRNA, being reported to stabilize the anti-HIV factor, histone deacetylase 6 (HDAC6). However, little is known about the role of TDP-43 in HIV infection. In this work, we seek for the TDP-43 function on regulating CD4+ T cell permissibility to HIV infection. We observed that over-expression of wt-TDP-43 in CD4+ T cells stabilized HDAC6, increasing mRNA and the protein levels of this antiviral enzyme. Under this experimental condition, HIV-1 infection was impaired, independently of the viral envelope glycoprotein (Env) complex tropism. The results obtained by using an HIV-1 Env-mediated cell-to-cell fusion model, under the same experimental conditions, suggest that the increase in TDP-43 levels negatively affects the viral Env fusion capacity. Moreover, the specific siRNA silencing of endogenous TDP-43 in target cells lead to a significant decrease in the levels of HDAC6 which consistently induces an increase in the fusogenic and infection activities of the HIV-1 Env. These observations were confirmed by using primary viral Envs from HIV+ individuals with different clinical phenotypes. An increase in the level of expression of wt-TDP-43 strongly reduced the Envs infection activity of viremic non-progressors (VNP) and rapid progressors (RP) HIV+ individuals down to the levels of the inefficient HIV-1 Envs from long-term non-progressor elite controllers (LTNP-EC) individuals. On the contrary, low levels of endogenous TDP-43, obtained after specific siRNA-TDP-43 knocking-down, significantly favors the infection activity of primary HIV-1 Envs of VNP and RP individuals, leading to an increase in the infection ability of the primary HIV-1/LTNP-EC Envs. Based on this evidence, we interpret that TDP-43 conditions cell permissibility to HIV infection by affecting viral Env fusion and infection capacities, at least by altering the cellular levels of the antiviral enzyme HDAC6.

The understanding of HIV-1 pathogenesis and clinical progression is incomplete because of the variable contribution of host, immune and viral factors. The involvement of viral factors has been investigated in extreme clinical phenotypes from rapid progressors to long-term non-progressors (LTNPs). Among HIV-1 proteins, the envelope glycoprotein complex (Env) has concentrated many studies for its important role in the immune response and in the first steps of viral replication. In this study, we analyzed the contribution of 41 Envs from 24 patients with different clinical progression rates and viral loads (VLs), LTNP-Elite Controllers (LTNP-ECs); Viremic LTNPs (vLTNPs), and non-controller’s individuals contemporary to LTNPs or recent, named Old and Modern progressors. We analyzed the Env expression, the fusion and cell-to-cell transfer capacities as well as viral infectivity. The sequence and phylogenetic analysis of Envs were also performed. In every functional characteristic, the Envs from subjects with viral control (LTNP-ECs and vLTNPs) showed significant lower performance compared to those from the progressor individuals (Old and Modern). Regarding sequence analysis, the variable loops of the gp120 subunit of the Env (i.e., V2, V4 and mainly V5) of the progressor individuals showed longer and more glycosylated sequences than controller subjects. Therefore, HIV-1 Envs presenting poor viral functions and shorter sequences were associated with viremic control and the non-progressor clinical phenotype, whereas functional Envs were associated with the lack of virological control and progressor clinical phenotypes. These correlations support the central role of Env genotypic and phenotypic characteristics in the in vivo HIV-1 infection and pathogenesis.IMPORTANCEThe role of the virus in the pathogenesis of HIV-1 infection has not been investigated in isolates from individuals with different progression rates. In this work, we studied the properties of the envelope glycoprotein complex (Env) in individuals with different progression rates to elucidate its role in pathogenesis. We estimated the Env expression, the CD4 binding, the fusion and cell-to-cell viral transfer capacities that affect the infectivity of the viral Envs in recombinant viruses. The Envs from individuals which control viral replication and lack clinical progression (LTNP-ECs and vLTNPs) showed lower functional capacities than from subjects with clinical progression (Old and Modern). The functional increase of the Envs characteristics was associated with an increase in viral infectivity and in increased length of variable loops and the number of glycosylation sites of the Env (gp120/SU). These results support the concept that viral characteristics contribute to viral infection and pathogenesis.

Background Understanding mid-term kinetics of immunity to SARS-CoV-2 is the cornerstone for public health control of the pandemic and vaccine development. However, current evidence is rather based on limited measurements, losing sight of the temporal pattern of these changes. Methods We conducted a longitudinal analysis on a prospective cohort of COVID-19 patients followed up for >6 months. Neutralizing activity was evaluated using HIV reporter pseudoviruses expressing SARS-CoV-2 S protein. IgG antibody titer was evaluated by ELISA against the S2 subunit, the receptor binding domain (RBD), and the nucleoprotein (NP). Statistical analyses were carried out using mixed-effects models. Findings We found that individuals with mild or asymptomatic infection experienced an insignificant decay in neutralizing activity, which persisted 6 months after symptom onset or diagnosis. Hospitalized individuals showed higher neutralizing titers, which decreased following a 2-phase pattern, with an initial rapid decline that significantly slowed after day 80. Despite this initial decay, neutralizing activity at 6 months remained higher among hospitalized individuals compared to mild symptomatic. The slow decline in neutralizing activity at mid-term contrasted with the steep slope of anti-RBD, S2, or NP antibody titers, all of them showing a constant decline over the follow-up period. Conclusions Our results reinforce the hypothesis that the quality of the neutralizing immune response against SARS-CoV-2 evolves over the post-convalescent stage. Funding This study was funded by 10.13039/501100016387Grifols, the Departament de Salut of the Generalitat de Catalunya (grant nos. SLD016 to J.B. and SLD015 to J.C.), the Spanish Health Institute Carlos III (grant nos. PI17/01518 and PI18/01332 to J.C.), CERCA Programme/Generalitat de Catalunya2017 SGR 252, and the crowdfunding initiatives #joemcorono, BonPreu/Esclat, and Correos. The funders had no role in the study design, the data collection and analysis, the decision to publish, or the preparation of the manuscript. E.P. was supported by a doctoral grant from the National Agency for Research and Development of Chile (ANID; 72180406). C.A.-N. was supported by a doctoral grant from Generalitat de Catalunya and Fons Social Europeu (FI). S.P.-Y. was supported by 10.13039/501100011850Fundación Canaria Doctor Manuel Morales and 10.13039/100015528Universidad de La Laguna., Graphical Abstract, Context and significance Assessing the durability of neutralizing responses against SARS-CoV-2 is crucial to predict the level of protection in post-convalescent COVID-19 patients. We monitored for >6 months a cohort of 210 SARS-CoV-2-infected individuals with a wide range of symptoms (from asymptomatic infection to severe disease). Our results indicate that neutralizing antibodies are stable for at least 6 months after infection. However, individuals with mild or asymptomatic infection developed lower titers of neutralizing antibodies and could be at higher risk of reinfection. Despite the maintenance of neutralizing antibodies, total antibody titers slowly but gradually declined over time without apparent stabilization. This observation requires further analysis to evaluate the potential role of viral persistence or viral re-exposure in maintaining neutralization titers., Pradenas et al. describe the kinetics of neutralizing antibodies against SARS-CoV-2 and demonstrate their association with clinical severity and their stability for at least 6 months, despite constant decay of IgG titers. These findings help us to understand the mid-term immune response and the impact on herd immunity.

Zika virus (ZIKV) infection and its associated congenital and other neurological disorders, particularly microcephaly and other fetal developmental abnormalities, constitute a World Health Organization (WHO) Zika Virus Research Agenda within the WHO’s R&D Blueprint for Action to Prevent Epidemics, and continue to be a Public Health Emergency of International Concern (PHEIC) today. ZIKV pathogenicity is initiated by viral infection and propagation across multiple placental and fetal tissue barriers, and is critically strengthened by subverting host immunity. ZIKV immune evasion involves viral non-structural proteins, genomic and non-coding RNA and microRNA (miRNA) to modulate interferon (IFN) signaling and production, interfering with intracellular signal pathways and autophagy, and promoting cellular environment changes together with secretion of cellular components to escape innate and adaptive immunity and further infect privileged immune organs/tissues such as the placenta and eyes. This review includes a description of recent advances in the understanding of the mechanisms underlying ZIKV immune modulation and evasion that strongly condition viral pathogenesis, which would certainly contribute to the development of anti-ZIKV strategies, drugs, and vaccines.

Understanding mid-term kinetics of immunity to SARS-CoV-2 is the cornerstone for public health control of the pandemic and vaccine development. However, current evidence is rather based on limited measurements, thus losing sight of the temporal pattern of these changes1–6. In this longitudinal analysis, conducted on a prospective cohort of COVID-19 patients followed up to 242 days, we found that individuals with mild or asymptomatic infection experienced an insignificant decay in neutralizing activity that persisted six months after symptom onset or diagnosis. Hospitalized individuals showed higher neutralizing titers, which decreased following a two-phase pattern, with an initial rapid decline that significantly slowed after day 80. Despite this initial decay, neutralizing activity at six months remained higher among hospitalized individuals. The slow decline in neutralizing activity at mid-term contrasted with the steep slope of antibody titers change, reinforcing the hypothesis that the quality of immune response evolves over the post-convalescent stage4,5.

In untreated HIV-1-infected individuals, viremia is positively associated with disease progression. However, some viremic non progressors (VNPs) individuals show paradoxical high CD4+ T cell counts. HIV-1 envelope glycoprotein complex (Env) is a major cytopathic determinant in viral replication; therefore, we have deeply characterized Env function in this rare clinical phenotype. Full-length Env clones isolated from individuals with Viral Load (VL) > 10,000 copies/mL classified as VNPs (n = 15) or rapid progressors (RPs, n = 17) were geno- and phenotypically analyzed by determining diversity, expression, CD4 binding/signaling, fusogenicity, infectivity and autophagy induction. Selected Env clones from VNPs and RPs (n = 32) showed similar expression, fusion and infection abilities. Env clones from both groups showed similar affinity for CD4 during cell-to-cell transmission and consistently induced similar levels of CD4 signaling, measured by α-tubulin acetylation. Moreover, we demonstrate for the first time that primary Env clones from VNP and RP induce autophagy in uninfected cells and that this feature correlated with fusogenic capacity but was unrelated to disease progression. In conclusion, our data suggest that Env clones from VNP individuals are fully functional. Therefore, the paradoxical CD4+ T cell count stability coexisting with high levels of viral replication is unrelated to Env function. This work is supported by Spanish AIDS network “Red Temática Cooperativa de Investigación en SIDA” RD12/0017/0002, RD12/0017/0028, RD12/0017/0034, RD16/0025/0011, RD16/0025/00XX and RD16/0025/0041 as part of the Plan Nacional R + D+ I and cofunded by Spanish “Instituto de Salud Carlos III (ISCIII)-Subdirección General de Evaluación y el Fondo Europeo de Desarrollo Regional (FEDER)”. Work in JB’s lab is supported by the Spanish Ministry of Health Project Number EC11-043 (to JB and AV-F), by the CNRS PICS program (to MB-P), J.B. and C.C. are researchers from Fundació Institut de Recerca en Ciències de la Salut Germans Trias i Pujol supported by the Health Department of the Catalan Government/Generalitat de Catalunya and ISCIII grant numbers PI14/01307 (to JB) and PI15/01053 (to CC). Work in CL-G’s lab was supported by grants SAF (2010-17226) and (2016-77894-R) from MINECO (Spain) and FIS (PI 13/02269, ISCIII). A.V-F’s Lab is supported by the European Regional Development Fund (ERDF), SAF2015-64118-R (MINECO, Spain) “Fundación CajaCanarias” BIO29, UNLL10-3E-783 (ERDF and “Fundación CajaCanarias”). D.M-A and S.M-H are funded by Fundación CajaCanarias BIO29, SAF2011-24671-FPI, “TESIS2017010116- and TESIS2015-010038-Programa Predoctoral de Formación del Personal Investigador, Agencia Canaria de Investigación, Innovación y Sociedad de la Información” and European Social Fund-fellowships. R.C-R is funded by RIS-RETIC RD16/0025/0011 and J.E-H is funded by the Cabildo Tenerife “Agustin de Betancourt” 2017 Program. Sí