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Targeting CD40 by agonistic antibodies used as vaccine adjuvants or for cancer immunotherapy is a strategy to stimulate immune responses. The majority of studied agonistic anti-human CD40 antibodies require crosslinking of their Fc region to inhibitory FcγRIIb to induce immune stimulation although this has been associated with toxicity in previous studies. Here we introduce an agonistic anti-human CD40 monoclonal IgG1 antibody (MAB273) unique in its specificity to the CD40L binding site of CD40 but devoid of Fcγ-receptor binding, we demonstrate rapid binding of MAB273 to B cells and dendritic cells resulting in strong activationin vitroon human cells andin vivoin rhesus macaques. Dissemination of fluorescently labeled MAB273 after subcutaneous administration was found predominantly at the site of injection and specific draining lymph nodes. Phenotypic cell differentiation and upregulation of genes associated with immune activation were found in the targeted tissues. Antigen-specific T cell responses were enhanced by MAB273 when given in a prime-boost regimen and for boosting low preexisting responses. MAB273 may therefore be a promising immunostimulatory adjuvant that warrants future testing for therapeutic and prophylactic vaccination strategies.

A single dose of the replication-competent, live-attenuated yellow fever virus (YFV) 17D vaccine provides lifelong immunity against human YFV infection. The magnitude, kinetics, and specificity of B cell responses to YFV 17D are relatively less understood than T cell responses. In this clinical study, we focused on early immune events critical for the development of humoral immunity to YFV 17D vaccination in 24 study subjects. More specifically, we studied the dynamics of several immune cell populations over time and the development of neutralizing Abs. At 7 d following vaccination, YFV RNA in serum as well as several antiviral proteins were detected as a sign of YFV 17D replication. Activation of Th1-polarized circulating T follicular helper cells followed germinal center activity, the latter assessed by the surrogate marker CXCL13 in serum. This coincided with a plasmablast expansion peaking at day 14 before returning to baseline levels at day 28. FluoroSpot-based analysis confirmed that plasmablasts were specific to the YFV-E protein. The frequencies of plasmablasts correlated with the magnitude of neutralizing Ab titers measured at day 90, suggesting that this transient B cell subset could be used as an early marker of induction of protective immunity. Additionally, YFV-specific memory B cells were readily detectable at 28 and 90 d following vaccination, and all study subjects tested developed protective neutralizing Ab titers. Taken together, these studies provide insights into key immune events leading to human B cell immunity following vaccination with the YFV 17D vaccine.

Adaptive immune responses play critical roles in viral clearance and protection against re‐infection, and SARS‐CoV‐2 is no exception. What is exceptional, is the rapid characterization of the immune response to the virus performed by researchers during the first 20 months of the pandemic. This has given us a more detailed understanding about SARS‐CoV‐2 than we have about many viruses that have been with us for a long time. Furthermore, effective COVID‐19 vaccines were developed in record time, and their rollout worldwide is already making a significant difference, although major challenges remain in terms of equal access. The pandemic has engaged scientists and the public alike, and terms such as seroprevalence, neutralizing antibodies, antibody escape and vaccine certificates have become familiar to a broad community. Here, we review key findings concerning B cell and antibody (Ab) responses to SARS‐CoV‐2, focusing on non‐severe cases and anti‐spike (S) Ab responses in particular, the latter being central to protective immunity induced by infection or vaccination. The emergence of viral variants that have acquired mutations in S acutely highlights the need for continued characterization of both emerging variants and Ab responses against these during the evolving pathogen‐immune system arms race.

BackgroundFlavivirus infections pose a significant global health burden underscoring the need for the development of safe and efficient vaccination strategies. Available flavivirus vaccines are from time to time concomitantly delivered to individuals in need. Co-administration of different vaccines saves time and visits to health care units and vaccine clinics. It serves to provide protection against multiple pathogens in a shorter time-span, both for individuals living in, or travelling to, endemic areas. However, safety and immunogenicity-related responses have not been appropriately evaluated upon concomitant delivery of these vaccines. Therefore, we performed an open label, non-randomized clinical trial studying the safety and immunogenicity following concomitant delivery of the Yellow fever virus (YFV) vaccine with Tick-borne encephalitis virus (TBEV) and Japanese encephalitis virus (JE) virus vaccines.Methods and findingsFollowing screening, healthy study subjects were enrolled into different cohorts receiving either TBEV and YFV vaccines, JEV and YFV vaccines, or in control groups receiving only the TBEV, JEV, or YFV vaccine. Concomitant delivery was given in the same or different upper arms for comparison in the co-vaccination cohorts. Adverse effects were recorded throughout the study period and blood samples were taken before and at multiple time-points following vaccination to evaluate immunological responses to the vaccines. Adverse events were predominantly mild in the study groups. Four serious adverse events (SAE) were reported throughout the trial, none of them deemed related to vaccination. The development of neutralizing antibodies (nAbs) against TBEV, JEV, or YFV was not affected by the concomitant vaccination strategy. Concomitant vaccination in the same or different upper arms did not significantly affect safety or immunogenicity-related outcomes. Exploratory studies on immunological effects were additionally performed and included studies of lymphocyte activation, correlates associated with germinal center activation, and plasmablast expansion.ConclusionsInactivated TBEV or JEV vaccines can be co-administered with the live attenuated YFV vaccine without an increased risk of adverse events and without reduced development of nAbs to the respective viruses. The vaccines can be delivered in the same upper arm without negative outcome.Trial registrationEudra CT 2017-002137-32Author summaryWhy was this study done?Flavivirus infections pose a significant global health burden, underscoring the need for the development of safe and efficient vaccination strategiesCo-administration of different flavivirus vaccines saves time and visits to health care units and vaccine clinics. It serves to provide protection against multiple pathogens in a shorter time-span, both for individuals living in or travelling to endemic areasSafety and immunogenicity-related responses have not been appropriately evaluated upon co-administration of many vaccines including currently used flavivirus vaccines, such as Yellow fever virus (YFV), Tick-borne encephalitis virus (TBEV), and Japanese encephalitis virus (JE) virus vaccinesBecause of this, we performed an open label, non-randomized clinical trial studying the safety and immunogenicity following co-administration of YFV vaccine with TBEV and JEV vaccinesWhat did the researchers find?Adverse events, neutralizing antibodies (nAbs) and other related immunological parameters were not adversely affected by concomitant delivery of the vaccinesConcomitant vaccination in the same versus different upper arms of study participants did not significantly affect safety or immunogenicity outcomesWhat do these findings mean?Co-administration of YFV vaccine and TBEV or JEV vaccines is feasible without increased risk of adverse events or reduced development of nAbs against the respective viruses. Furthermore, the vaccines can safely be delivered in the same upper arm without negative outcome

Mucosa-associated invariant T (MAIT) cells are unconventional T cells with innate-like capacity to rapidly respond to microbial infection via MR1-restricted antigen recognition. Emerging evidence indicate that they can also act as rapid sensors of viral infection via innate cytokine activation. However, their possible role in the immune response to mRNA vaccination is unknown. Here, we evaluated the involvement of MAIT cells in individuals vaccinated with the BNT162b2 mRNA SARS-CoV-2 vaccine. MAIT cell levels, phenotype and function in circulation were preserved and unperturbed through day 35 post-vaccination in healthy donor (HD) vaccinees, as well as people living with HIV (PLWH) or with primary immunodeficiency (PID). Unexpectedly, pre-vaccination and post-vaccination levels of MAIT cells correlated positively with the magnitude of the SARS-CoV-2 spike protein-specific CD4 T cell and antibody responses in the HD vaccinees. This pattern was largely preserved in the PID group, but less so in the PLWH group. Furthermore, in the HD vaccinees levels of MAIT cell activation and cytolytic potential correlated negatively to the adaptive antigen-specific immune responses. These findings indicate an unexpected association between MAIT cell compartment characteristics and the immune response magnitude to the BNT162b2 mRNA vaccine.

Many immunocompromised patients mount suboptimal humoral immunity after SARS-CoV-2 mRNA vaccination. Here, we assessed the single-cell profile of SARS-CoV-2-specific T cells post-mRNA vaccination in healthy individuals and patients with various forms of immunodeficiencies. Impaired vaccine-induced cell-mediated immunity was observed in many immunocompromised patients, particularly in solid-organ transplant and chronic lymphocytic leukemia patients. Notably, individuals with an inherited lack of mature B cells, i.e., X-linked agammaglobulinemia (XLA) displayed highly functional spike-specific T cell responses. Single-cell RNA-sequencing further revealed that mRNA vaccination induced a broad functional spectrum of spike-specific CD4+ and CD8+ T cells in healthy individuals and patients with XLA. These responses were founded on polyclonal repertoires of CD4+ T cells and robust expansions of oligoclonal effector-memory CD45RA+ CD8+ T cells with stem-like characteristics. Collectively, our data provide the functional continuum of SARS-CoV-2-specific T cell responses post-mRNA vaccination, highlighting that cell-mediated immunity is of variable functional quality across immunodeficiency syndromes.

The lipid nanoparticle (LNP)-encapsulated, nucleoside-modified mRNA platform has been used to generate safe and effective vaccines in record time against COVID-19. Here, we review the current understanding of the manner whereby mRNA vaccines induce innate immune activation and how this contributes to protective immunity. We discuss innate immune sensing of mRNA vaccines at the cellular and intracellular levels and consider the contribution of both the mRNA and the LNP components to their immunogenicity. A key message that is emerging from recent observations is that the LNP carrier acts as a powerful adjuvant for this novel vaccine platform. In this context, we highlight important gaps in understanding and discuss how new insight into the mechanisms underlying the effectiveness of mRNA-LNP vaccines may enable tailoring mRNA and carrier molecules to develop vaccines with greater effectiveness and milder adverse events in the future.

Background Immunocompromised individuals are highly susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Whether vaccine-induced immunity in these individuals involves oral cavity, a primary site of infection, is presently unknown. Methods Immunocompromised patients (n = 404) and healthy controls (n = 82) participated in a prospective clinical trial (NCT04780659) encompassing two doses of the mRNA BNT162b2 vaccine. Primary immunodeficiency (PID), secondary immunodeficiencies caused by human immunodeficiency virus (HIV) infection, allogeneic hematopoietic stem cell transplantation (HSCT)/chimeric antigen receptor T cell therapy (CAR-T), solid organ transplantation (SOT), and chronic lymphocytic leukemia (CLL) patients were included. Salivary and serum immunoglobulin G (IgG) reactivities to SARS-CoV-2 spike were measured by multiplex bead-based assays and Elecsys anti-SARS-CoV-2 S assay. Findings IgG responses to SARS-CoV-2 spike antigens in saliva in HIV and HSCT/CAR-T groups were comparable to those of healthy controls after vaccination. The PID, SOT, and CLL patients had weaker responses, influenced mainly by disease parameters or immunosuppressants. Salivary responses correlated remarkably well with specific IgG titers and the neutralizing capacity in serum. Receiver operating characteristic curve analysis for the predictive power of salivary IgG yielded area under the curve (AUC) = 0.95 and positive predictive value (PPV) = 90.7% for the entire cohort after vaccination. Conclusions Saliva conveys vaccine responses induced by mRNA BNT162b2. The predictive power of salivary spike IgG makes it highly suitable for screening vulnerable groups for revaccination. Funding Knut and Alice Wallenberg Foundation, Erling Perssons family foundation, Region Stockholm, Swedish Research Council, Karolinska Institutet, Swedish Blood Cancer Foundation, PID patient organization of Sweden, Nordstjernan AB, Center for Medical Innovation (CIMED), Swedish Medical Research Council, and Stockholm County Council (ALF)., Graphical abstract, Context and significance People with a weakened immune system may respond less well to vaccination and are more vulnerable to infections. This work investigates the predictive value of saliva antibodies in immunocompromised patients. We report that IgG to SARS-CoV-2 spike in saliva correlated remarkably well to that detected in blood after Pfizer mRNA vaccination. Among the immunosuppressive conditions studied, low spike-IgG responses were mainly associated with genetic immune disorders, organ transplantation, chronic lymphatic leukemia, and immunosuppressants, while people living with human immunodeficiency virus or stem cell transplant responded comparably to healthy participants. The clear correlation between anti-spike-IgG in saliva and blood extends to the neutralizing capacity in serum. In conclusion, saliva is suitable and efficient for monitoring vaccine immunity and revaccination., Healy et al. report a clear correlation between salivary and blood IgG to SARS-CoV-2 spike in immunocompromised patients after mRNA vaccination. The specific IgG also correlates to the serum-neutralizing capacity. Their findings indicate that saliva is highly suitable for monitoring vaccine immunity in these extremely vulnerable patients.

BackgroundImmunocompromised individuals are highly susceptible to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Whether vaccine-induced immunity in these individuals involves the oral cavity, a primary site of infection, is presently unknown.MethodsImmunocompromised individuals (n=404) and healthy controls (n=82) participated in a prospective clinical trial encompassing two doses of the mRNA BNT162b2 vaccine. Immunocompromised individuals included primary immunodeficiencies (PID) and secondary immunodeficiencies caused by human immunodeficiency virus (HIV) infection, allogeneic hematopoietic stem cell transplantation (HSCT)/chimeric antigen receptor T cell therapy (CAR-T), solid organ transplantation (SOT), and chronic lymphocytic leukemia (CLL). Saliva and serum samples were collected at four time points from the first vaccine dose until 2 weeks after second dose. SARS-CoV-2 spike specific immunoglobulin G (IgG) responses were quantified by a multiplex bead-based assay in saliva and correlated to paired serum IgG titers determined by Elecsys® Anti-SARS-CoV-2 S assay.ResultsIgG responses to the SARS-CoV-2 spike full-length trimeric glycoprotein (Spike-f) and S1 subunit in saliva in the HIV and HSCT/CAR-T groups were comparable to healthy controls. In contrast, PID, SOT, and CLL patients all displayed weaker responses which were mainly influenced by disease parameters or immunosuppressants. Salivary IgG levels strongly correlated with serum IgG titers on days 21 and 35 (rho=0.8079 and 0.7768, p=ConclusionsSaliva conveys humoral responses induced by BNT162b2 vaccination. The predictive power makes it highly suitable for screening low responding/vulnerable groups for revaccination.Trial RegistrationClinicalTrials.govIdentifier:NCT04780659FundingKnut and Alice Wallenberg Foundation, Erling Perssons family foundation, Region Stockholm, Swedish Research Council, Karolinska Institutet, The Swedish Blood Cancer Foundation and the organization for PID patient group in Sweden, and Nordstjernan AB. Center for Medical Innovation (CIMED), the Swedish Medical Research Council and the Stockholm County Council (ALF).GRAPHIC ABSTRACT

BackgroundPatients with immunocompromised disorders have mainly been excluded from clinical trials of vaccination against COVID-19. Thus, the aim of this prospective clinical trial was to investigate the safety and efficacy after two doses of BNT162b2 mRNA vaccination in five selected groups of immunocompromised patients and healthy controls.Methods539 study subjects (449 patients and 90 controls) were included in the clinical trial. The patients had either primary (n=90), or secondary immunodeficiency disorders due to human immunodeficiency virus infection (n=90), allogeneic hematopoietic stem cell transplantation/chimeric antigen receptor T cell therapy (n=90), solid organ transplantation (SOT) (n=89), or chronic lymphocytic leukemia (CLL) (n=90). The primary endpoint was seroconversion rate two weeks after the second dose. The secondary endpoints were safety and documented SARS-CoV-2 infection.FindingsAdverse events were generally mild, but one case of fatal suspected unexpected serious adverse reaction occurred. 72·2% of the immunocompromised patients seroconverted compared to 100% of the controls (p=0.004). Lowest seroconversion rates were found in the SOT (43·4%) and CLL (63·3%) patient groups with observed negative impact of treatment with mycophenolate mofetil and ibrutinib, respectively.InterpretationThe results showed that the mRNA BNT162b2 vaccine was safe in immunocompromised patients. The rate of seroconversion was substantially lower than in healthy controls, with a wide range of rates and antibody titres among predefined patient groups and subgroups. This clinical trial highlights the need for additional vaccine doses in certain immunocompromised patient groups and/or subgroups to improve immunity.FundingKnut and Alice Wallenberg Foundation, Nordstjernan AB, Region Stockholm, Swedish Research Council, Karolinska Institutet, and organizations for PID/CLL-patients in Sweden.

Germinal centers (GCs) are structures formed within B cell follicles critical for the generation of high affinity antibodies. The evaluation of GCs in secondary lymphoid tissues has emerged as a valuable means for understanding the immunological activity in vaccine responses, autoimmunity and cancer. The analysis has been facilitated by advances in sampling techniques, including non-invasive lymph node collection and fine needle aspiration. In this study, we performed a systematic comparison between immunohistology and flow cytometry for analysis of GCs with the major aim to identify strategies for data analysis that would allow to relate data acquired by the two methods. Lymph nodes from rhesus macaques were divided in half and analysed as either cryosections or cell suspensions. Using human markers such as PD-1 and Ki67 to identify T follicular helper (TFH) cells and GC B cells, we developed a method for GC analysis by immunohistology using CellProfiler™ software and a flow cytometry panel with relatively limited numbers of antibodies to be scalable and feasible for most laboratories to perform. While some discrepancies between the two methods were identified, TFH cells and GC B cells normalized by total CD3+ T cell or CD20+ B cell numbers, respectively, in immunohistology correlated well with matched data from flow cytometry. GC area normalized by section area in immunohistology also correlated well with TFH cells per total live cells from flow cytometry. Performing this type of data analysis would therefore facilitate comparison of results generated between the two methods.

SUMMARY Using non-human primates (NHPs), mice, and human primary cells, we found a role for interleukin-10 (IL-10) in the upregulation of the tissue-resident memory T cell (TRM) marker CD103. In NHPs, intravenous, but not subcutaneous, immunization with peptide antigen and an adjuvant combining an agonistic anti-CD40 antibody plus poly(IC:LC) induced high levels of CD103+ TRMs in the lung, which correlated with early plasma IL-10 levels. Blocking IL-10 reduced CD103 expression on human T cells stimulated in vitro with the adjuvant combination as well as diminished CD103 on lung-resident T cells in vivo in mice. Monocyte-produced IL-10 induced the release of surface-bound transforming growth factor β (TGF-β), which in turn upregulated CD103 on T cells. Early TGF-β imprinted increased sensitivity to TGF-β restimulation, indicating an early commitment of the T cell lineage toward TRMs during the priming stage of activation. IL-10-mediated TGF-β signaling may therefore have a critical role in the generation of TRM following vaccination., Graphical Abstract, In Brief Thompson et al. outline a role for early IL-10 following immunization in the release of TGF-β and subsequent differentiation of CD103+ TRMs. Using a combination of non-human primate, human, and murine systems, the authors demonstrate that blocking IL-10 reduces CD103 expression, whereas delivery of IL-10 can augment a CD103+ phenotype.

International audience; In cancer, infection and inflammation, the immune system's function can be dysregulated. Instead of fighting disease, immune cells may increase pathology and suppress host-protective immune responses. Myeloid cells show high plasticity and adapt to changing conditions and pathological challenges. Despite their relevance in disease pathophysiology, the identity, heterogeneity and biology of myeloid cells is still poorly understood. We will focus on phenotypical and functional markers of one of the key myeloid regulatory subtypes, the myeloid derived suppressor cells (MDSC), in humans, mice and non-human primates. Technical issues regarding the isolation of the cells from tissues and blood, timing and sample handling of MDSC will be detailed. Localization of MDSC in a tissue context is of crucial importance and immunohistochemistry approaches for this purpose are discussed. A minimal antibody panel for MDSC research is provided as part of the Mye-EUNITER COST action. Strategies for the identification of additional markers applying state of the art technologies such as mass cytometry will be highlighted. Such marker sets can be used to study MDSC phenotypes across tissues, diseases as well as species and will be crucial to accelerate MDSC research in health and disease.

Background: mmunocompromised individuals are highly susceptible to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Whether vaccine-induced immunity in these individuals involves the oral cavity, a primary site of infection, is presently unknown. Methods: Immunocompromised individuals (n=404) and healthy controls (n=82) participated in a prospective clinical trial encompassing two doses of the mRNA BNT162b2 vaccine. Immunocompromised individuals included primary immunodeficiencies (PID) and secondary immunodeficiencies caused by human immunodeficiency virus (HIV) infection, allogeneic hematopoietic stem cell transplantation (HSCT)/chimeric antigen receptor T cell therapy (CAR-T), solid organ transplantation (SOT), and chronic lymphocytic leukemia (CLL). Saliva and serum samples were collected at four time points from the first vaccine dose until 2 weeks after second dose. SARS-CoV-2 spike specific immunoglobulin G (IgG) responses were quantified by a multiplex bead-based assay in saliva and correlated to paired serum IgG titers determined by Elecsys Anti-SARS-CoV-2 S assay. Results: IgG responses to the SARS-CoV-2 spike full-length tr­imeric glycoprotein (Spike-f) and S1 subunit in saliva in the HIV and HSCT/CAR-T groups were comparable to healthy controls. In contrast, PID, SOT, and CLL patients all displayed weaker responses which were mainly influenced by disease parameters or immunosuppressants. Salivary IgG levels strongly correlated with serum IgG titers on days 21 and 35 (rho=0.8079 and 0.7768, p=

Understanding the presence and durability of antibodies against SARS-CoV-2 in the airways is required to provide insights into the ability of individuals to neutralize the virus locally and prevent viral spread. Here, we longitudinally assessed both systemic and airway immune responses upon SARS-CoV-2 infection in a clinically well-characterized cohort of 147 infected individuals representing the full spectrum of COVID-19 severity, from asymptomatic infection to fatal disease. In addition, we evaluated how SARS-CoV-2 vaccination influenced the antibody responses in a subset of these individuals during convalescence as compared with naive individuals. Not only systemic but also airway antibody responses correlated with the degree of COVID-19 disease severity. However, although systemic IgG levels were durable for up to 8 months, airway IgG and IgA declined significantly within 3 months. After vaccination, there was an increase in both systemic and airway antibodies, in particular IgG, often exceeding the levels found during acute disease. In contrast, naive individuals showed low airway antibodies after vaccination. In the former COVID-19 patients, airway antibody levels were significantly elevated after the boost vaccination, highlighting the importance of prime and boost vaccinations for previously infected individuals to obtain optimal mucosal protection.

Cell fate decisions during early B cell activation determine the outcome of responses to pathogens and vaccines. We examined the early B cell response to T-dependent antigen in mice by single-cell RNA sequencing. Early after immunization, a homogeneous population of activated precursors (APs) gave rise to a transient wave of plasmablasts (PBs), followed a day later by the emergence of germinal center B cells (GCBCs). Most APs rapidly exited the cell cycle, giving rise to non-GC-derived early memory B cells (eMBCs) that retained an AP-like transcriptional profile. Rapid decline of antigen availability controlled these events; provision of excess antigen precluded cell cycle exit and induced a new wave of PBs. Fate mapping revealed a prominent contribution of eMBCs to the MBC pool. Quiescent cells with an MBC phenotype dominated the early response to immunization in primates. A reservoir of APs/eMBCs may enable rapid readjustment of the immune response when failure to contain a threat is manifested by increased antigen availability. Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [2018-05973, SNIC 2019/8-289, 2020/16-34, 2017-01118, 2017-01439]; CancerfondenSwedish Cancer Society [CAN 2018/710]; Ake Wibergs Stiftelse [M18-0094]; German Research Foundation (DFG)German Research Foundation (DFG) [RE 4264/1-1]; Boehringer IngelheimBoehringer Ingelheim; European Research Council (ERC)European Research Council (ERC)European Commission [740349, 850638]; Bill & Melinda Gates FoundationBill & Melinda Gates FoundationCGIAR [OPP1156262]; Ministry of Science and Higher Education of the Russian Federation [075-15-2020784]

Distinct types of dorsal root ganglion sensory neurons may have unique contributions to chronic pain. Identification of primate sensory neuron types is critical for understanding the cellular origin and heritability of chronic pain. However, molecular insights into the primate sensory neurons are missing. Here we classify non-human primate dorsal root ganglion sensory neurons based on their transcriptome and map human pain heritability to neuronal types. First, we identified cell correlates between two major datasets for mouse sensory neuron types. Machine learning exposes an overall cross-species conservation of somatosensory neurons between primate and mouse, although with differences at individual gene level, highlighting the importance of primate data for clinical translation. We map genomic loci associated with chronic pain in human onto primate sensory neuron types to identify the cellular origin of human chronic pain. Genome-wide associations for chronic pain converge on two different neuronal types distributed between pain disorders that display different genetic susceptibilities, suggesting both unique and shared mechanisms between different pain conditions.

Understanding the presence and durability of antibodies against SARS-CoV-2 in the airways is required to provide insights on the ability of individuals to neutralize the virus locally and prevent viral spread. Here, we longitudinally assessed both systemic and airway immune responses upon SARS-CoV-2 infection in a clinically well-characterized cohort of 147 infected individuals representing the full spectrum of COVID-19 severity; from asymptomatic infection to fatal disease. In addition, we evaluated how SARS-CoV-2 vaccination influenced the antibody responses in a subset of these individuals during convalescence as compared to naïve individuals. Not only systemic but also airway antibody responses correlated with the degree of COVID-19 disease severity. However, while systemic IgG levels were durable for up to 8 months, airway IgG and IgA had declined significantly within 3 months. After vaccination, there was an increase in both systemic and airway antibodies, in particular IgG, often exceeding the levels found during acute disease. In contrast, naïve individuals showed low airway antibodies after vaccination. In the former COVID-19 patients, airway antibody levels were significantly elevated after the boost vaccination, highlighting the importance of prime and boost vaccination also for previously infected individuals to obtain optimal mucosal protection.

While myeloid-derived suppressor cells (MDSCs) in humans and mice have been intensively investigated, there is limited knowledge of these cells in nonhuman primates (NHPs). NHPs serve as critical models for late-stage testing of several biomedical inventions before proceeding with clinical trials and it is therefore important to fully understand their immune compartments and similarities with humans. Here, using antihuman cross-reactive antibodies, we provide flow cytometric analysis protocols for identification of MDSCs in the blood of rhesus macaques, one of the major NHP species as experimental models. Discrepancies and similarities between rhesus and human MDSCs are discussed.

While myeloid-derived suppressor cells (MDSCs) in humans and mice have been intensively investigated, there is limited knowledge of these cells in nonhuman primates (NHPs). NHPs serve as critical models for late-stage testing of several biomedical inventions before proceeding with clinical trials and it is therefore important to fully understand their immune compartments and similarities with humans. Here, using antihuman cross-reactive antibodies, we provide flow cytometric analysis protocols for identification of MDSCs in the blood of rhesus macaques, one of the major NHP species as experimental models. Discrepancies and similarities between rhesus and human MDSCs are discussed.

The immunopathology of COVID-19 remains enigmatic, exhibiting immunodysregulation and T cell lymphopenia. Monocytic myeloid-derived suppressor cells (M-MDSC) are T cell suppressors that expand in inflammatory conditions, but their role in acute respiratory infections remains unclear. We studied blood and airways of COVID-19 patients across disease severity at multiple timepoints. M-MDSC frequencies were elevated in blood but not in nasopharyngeal or endotracheal aspirates of COVID-19 patients compared to controls. M-MDSCs isolated from COVID-19 patients suppressed T cell proliferation and IFNγ production partly via an arginase-1 (Arg-1) dependent mechanism. Furthermore, patients showed increased Arg-1 and IL-6 plasma levels. COVID-19 patients had fewer T cells, and displayed downregulated expression of the CD3ζ chain. Ordinal regression showed that early M-MDSC frequency predicted subsequent disease severity. In conclusion, M-MDSCs expand in blood of COVID-19 patients, suppress T cells and strongly associate with disease severity, suggesting a role for M-MDSCs in the dysregulated COVID-19 immune response.

The outbreak and spread of SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus 2), the cause of coronavirus disease 2019 (COVID-19), is a current global health emergency and a prophylactic vaccine is needed urgently. The spike glycoprotein of SARS-CoV-2 mediates entry into host cells, and thus is a target for neutralizing antibodies and vaccine design. Here we show that adjuvanted protein immunization with SARS-CoV-2 spike trimers, stabilized in prefusion conformation, results in potent antibody responses in mice and rhesus macaques with neutralizing antibody titers orders of magnitude greater than those typically measured in serum from SARS-CoV-2 seropositive humans. Neutralizing antibody responses were observed after a single dose, with exceptionally high titers achieved after boosting. Furthermore, neutralizing antibody titers elicited by a dose-sparing regimen in mice were similar to those obtained from a high dose regimen. Taken together, these data strongly support the development of adjuvanted SARS-CoV-2 prefusion-stabilized spike protein subunit vaccines.