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Accelerate lung repair in SARS‐CoV‐2 pneumonia is essential for pandemic handling. Innate lymphoid cells (ILCs) are likely players, given their role in mucosal protection and tissue homeostasis. We studied ILC subpopulations at two time points in a cohort of patients admitted in the hospital due to SARS‐CoV‐2 infection. COVID‐19 patients with moderate/severe respiratory failure featured profound depletion of circulating ILCs at hospital admission, in agreement with overall lymphocyte depletion. However, ILCs recovered in direct correlation with lung function improvement as measured by oxygenation index and in negative association with inflammatory and lung/endothelial damage markers like RAGE. While both ILC1 and ILC2 expanded, ILC2 showed the most striking phenotype changes, with CCR10 upregulation in strong correlation with these parameters. Overall, CCR10 + ILC2 emerge as relevant contributors to SARS‐CoV‐2 pneumonia recovery., Moderate to severe COVID‐19 is associated with an overall decrease in all innate lymphoid cells’ subsets in parallel with the well‐known lymphopenia. We report, in association with the oxygenation improvement, a significant expansion of ILC1, irrespectively of CD161 expression, and of CCR10 expressing ILC2, suggesting their involvement in lung regeneration.

Mucosal vaccination is regarded as a promising alternative to classical, intramuscular vaccine delivery. However, only a limited number of vaccines have been licensed for mucosal administration in humans. Here we propose Leishmania tarentolae, a protozoan parasite, as a potential antigen vehicle for mucosal vaccination, for administration via the rectal or oral routes. To test this hypothesis, we exploited L. tarentolae for the production and delivery of SARS-CoV-2 antigens. Two antigens were assayed in BALB/c mice: Lt-spike, a L. tarentolae clone engineered for the surface expression of the SARS-CoV-2 spike protein; RBD-SD1, a purified portion of the spike protein, produced by another engineered clone of the protozoon. Immune response parameters were then determined at different time points. Both antigens, administered either separately or in combination (Lt-spike + RBD-SD1, hereafter LeCoVax-2), determined significant IgG seroconversion and production of neutralizing antibodies after subcutaneous administration, but only in the presence of adjuvants. After rectal administration, the purified RBD-SD1 antigen did not induce any detectable immune response, in comparison with the intense response observed after administration of LeCoVax-2 or Lt-spike alone. In rectal administration, LeCoVax-2 was also effective when administered without adjuvant. Our results show that L. tarentolae is an efficient and safe scaffold for production and delivery of viral antigens, to be used as vaccines. In addition, rectal vaccination experiments prove that L. tarentolae is suitable as a vaccine vehicle and adjuvant for enteral vaccination. Finally, the combined preparation LeCoVax-2 can be considered as a promising candidate vaccine against SARS-CoV-2, worthy of further investigation.

Both B cells and T cells are involved in an effective immune response to SARS‐CoV‐2, the disease‐causing virus of COVID‐19. While B cells—with the indispensable help of CD4+ T cells—are essential to generate neutralizing antibodies, T cells on their own have been recognized as another major player in effective anti‐SARS‐CoV‐2 immunity. In this report, we provide insights into the characteristics of individual HLA‐A*02:01‐ and HLA‐A*24:02‐restricted SARS‐CoV‐2‐reactive TCRs, isolated from convalescent COVID‐19 patients. We observed that SARS‐CoV‐2‐reactive T‐cell populations were clearly detectable in convalescent samples and that TCRs isolated from these T cell clones were highly functional upon ectopic re‐expression. The SARS‐CoV‐2‐reactive TCRs described in this report mediated potent TCR signaling in reporter assays with low nanomolar EC50 values. We further demonstrate that these SARS‐CoV‐2‐reactive TCRs conferred powerful T‐cell effector function to primary CD8+ T cells as evident by a robust anti‐SARS‐CoV‐2 IFN‐γ response and in vitro cytotoxicity. We also provide an example of a long‐lasting anti‐SARS‐CoV‐2 memory response by reisolation of one of the retrieved TCRs 5 months after initial sampling. Taken together, these findings contribute to a better understanding of anti‐SARS‐CoV‐2 T‐cell immunity and may contribute to paving the way toward immunotherapeutics approaches targeting SARS‐CoV‐2., T cell receptors (TCRs) directed against previously identified SARS‐CoV‐2 target epitopes were isolated from convalescent COVID‐19 patients by single‐cell sequencing. Upon ectopic re‐expression, these SARS‐CoV‐2 TCRs conferred potent effector functions such as cytotoxicity and Interferon‐gamma production.

The increasing numbers of infected cases of coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) poses serious threats to public health and the global economy. Most SARS‐CoV‐2 neutralizing antibodies target the receptor binding domain (RBD) and some the N‐terminal domain (NTD) of the spike protein, which is the major antigen of SARS‐CoV‐2. While the antibody response to RBD has been extensively characterized, the antigenicity and immunogenicity of the NTD protein are less well studied. Using 227 plasma samples from COVID‐19 patients, we showed that SARS‐CoV‐2 NTD‐specific antibodies could be induced during infection. As compared to the results of SARS‐CoV‐2 RBD, the serological response of SARS‐CoV‐2 NTD is less cross‐reactive with SARS‐CoV, a pandemic strain that was identified in 2003. Furthermore, neutralizing antibodies are rarely elicited in a mice model when NTD is used as an immunogen. We subsequently demonstrate that NTD has an altered antigenicity when expressed alone. Overall, our results suggest that while NTD offers a supplementary strategy for serology testing, it may not be suitable as an immunogen for vaccine development., Receptor binding domain (RBD) of the SARS‐CoV‐2 spike protein has been extensively studied in functional antibody screening and COVID‐19 vaccine design. To explore the function of N‐terminal domain (NTD) of spike protein, we reveal that NTD is a supplementary antigen for serology testing, but not a suitable immunogen for vaccine design.

Myeloid‐derived suppressor cells (MDSCs) are important regulators of immune processes during sepsis in mice. However, confirming these observations in humans has been challenging due to the lack of defined preparation protocols and phenotyping schemes for MDSC subsets. Thus, it remains unclear how MDSCs are involved in acute sepsis and whether they have a role in the long‐term complications seen in survivors. Here, we combined comprehensive flow cytometry phenotyping with unsupervised clustering using self‐organizing maps to identify the three recently defined human MDSC subsets in blood from severe sepsis patients, long‐term sepsis survivors, and age‐matched controls. We demonstrated the expansion of monocytic M‐MDSCs and polymorphonuclear PMN‐MDSCs, but not early‐stage (e)‐MDSCs during acute sepsis. High levels of PMN‐MDSCs were also present in long‐term survivors many months after discharge, suggesting a possible role in sepsis‐related complications. Altogether, by employing unsupervised clustering of flow cytometric data we have confirmed the likely involvement of human MDSC subsets in acute sepsis, and revealed their expansion in sepsis survivors at late time points. The application of this strategy in future studies and in the clinical/diagnostic context would enable rapid progress toward a full understanding of the roles of MDSC in sepsis and other inflammatory conditions., M‐MDSCs and PMN‐MDSCs are expanded during septic shock. PMN‐MDSCs frequency remains elevated months after recovery from sepsis. Unsupervised metaclustering confirms and complements the results obtained by conventional gating.

COVID‐19 is a life‐threatening disease leading to bilateral pneumonia and respiratory failure. The underlying reasons why a smaller percentage of patients present with severe pulmonary symptoms whereas the majority is only mildly affected are to date not well understood. Comparing the immunological phenotype in healthy donors and patients with mild versus severe COVID‐19 shows that in COVID‐19 patients, NK‐/B‐cell activation and proliferation are enhanced independent of severity. As an important precondition for effective antibody responses, T‐follicular helper cells and antibody secreting cells are increased both in patients with mild and severe SARS‐CoV‐2 infection. Beyond this, T cells in COVID‐19 patients exhibit a stronger activation profile with differentiation toward effector cell phenotypes. Importantly, when looking at the rates of pulmonary complications in COVID‐19 patients, the chemokine receptor CCR4 is higher expressed by both CD4 and CD8 T cells of patients with severe COVID‐19. This raises the hypothesis that CCR4 upregulation on T cells in the pathogenesis of COVID‐19 promotes stronger T‐cell attraction to the lungs leading to increased immune activation with presumably higher pulmonary toxicity. Our study contributes significantly to the understanding of the immunological changes during COVID‐19, as new therapeutic agents, preferentially targeting the immune system, are highly warranted., Patients with mild COVID‐19 after SARS‐CoV2 infection exhibit increased T‐cell activation and induction of T‐cell exhaustion. During severe COVID‐19 patients show massive T‐cell activation and upregulation of homing receptors promoting hyperinflammation and increased lung trafficking.

The pathogenesis of autoimmune complications triggered by SARS‐CoV2 has not been completely elucidated. Here, we performed an analysis of the cellular immune status, cell ratios, and monocyte populations of patients with COVID‐19 treated in the intensive care unit (ICU) (cohort 1, N = 23) and normal care unit (NCU) (cohort 2, n = 10) compared with control groups: patients treated in ICU for noninfectious reasons (cohort 3, n = 30) and patients treated in NCU for infections other than COVID‐19 (cohort 4, n = 21). Patients in cohort 1 presented significant differences in comparison with the other cohorts, including reduced frequencies of lymphocytes, reduced CD8+T‐cell count, reduced percentage of activated and intermediate monocytes and an increased B/T8 cell ratio. Over time, patients in cohort 1 who died presented with lower counts of B, T, CD4+T, CD8+T‐lymphocytes, NK cells, and activated monocytes. The B/T8 ratio was significantly lower in the group of survivors. In cohort 1, significantly higher levels of IgG1 and IgG3 were found, whereas cohort 3 presented higher levels of IgG3 compared to controls. Among many immune changes, an elevated B/T8‐cell ratio and a reduced rate of activated monocytes were mainly observed in patients with severe COVID‐19. Both parameters were associated with death in cohort 1., Patients with severe COVID‐19 present a particular set of immune changes in comparison to patients with mild disease and controls. These include consumption of certain monocyte and lymphocyte populations and an elevated B/T8 Ratio. COVID‐19 patients in general share a proinflammatory immunoglobulin profile with elevated proportions of IgG1 and/or IgG3.

Antibodies play an important role in host defense against microorganisms. Besides direct microbicidal activities, antibodies can also provide indirect protection via crosstalk to constituents of the adaptive immune system. Similar to many human chronic viral infections, persistence of Lymphocytic choriomeningitis virus (LCMV) is associated with compromised T- and B-cell responses. The administration of virus-specific non-neutralizing antibodies (nnAbs) prior to LCMV infection protects against the establishment of chronic infection. Here, we show that LCMV-specific nnAbs bind preferentially Ly6Chi inflammatory monocytes (IMs), promote their infection in an Fc-receptor independent way, and support acquisition of APC properties. By constituting additional T-cell priming opportunities, IMs promote early activation of virus-specific CD8 T cells, eventually tipping the balance between T-cell exhaustion and effector cell differentiation, preventing establishment of viral persistence without causing lethal immunopathology. These results document a beneficial role of IMs in avoiding T-cell exhaustion and an Fc-receptor independent protective mechanism provided by LCMV-specific nnAbs against the establishment of chronic infection., European Journal of Immunology, 51 (6), ISSN:0014-2980, ISSN:1521-4141

Lymphoid organ hypertrophy is a characteristic feature of acute infection and is considered to enable efficient induction of adaptive immune responses. Accordingly, oral infection with rotavirus induced a robust increase in cellularity in the mesenteric LNs, whose kinetics correlated with viral load and was caused by halted lymphocyte egress and increased recruitment of cells without altered cellular proliferation. Lymphocyte sequestration and mesenteric LN hypertrophy were independent of type 1 IFN receptor signaling or the continuous presence of TNF‐α. Our results support previous findings that adaptive immunity toward rotavirus is initiated primarily in the mesenteric LNs and show that type I IFN or TNF‐α are not required to coordinate the events involved in the LN response., Lymphoid organ hypertrophy facilitates lymphocyte priming in response to immune activation. We here report that mesenteric LN expansion in response to asymptomatic rotavirus infection in adult mice is independent of type I IFN and TNF‐α and caused both by enhanced recruitment and halted egress of lymphocytes.

Enterobacteriaceae are a large family of Gram-negative bacteria that includes both commensals and opportunistic pathogens. The latter can cause severe nosocomial infections, with outbreaks. This T cell subset was severely reduced in septic patients with K. pneumoniae bloodstream infection who also selectively lacked circulating K. pneumoniereactive to several Enterobacteriaceae species. These cross-reactive Th cell clones were expanded in vivo and a large fraction of them recognized the conserved outer membrane protein A (OmpA) antigen. Interestingly, Enterobacteriaceae broadly reactive T cells were also prominent among in vitro primed T cells. Collectively, these data point to the existence of immunodominant T cell epitopes shared among different Enterobacteriaceae species and targeted byT cells that are readily found in the pre-immune repertoire and are clonally expanded in the memory repertoire., European Journal of Immunology, 51 (3), ISSN:0014-2980, ISSN:1521-4141

TRIANNI mice carry an entire set of human immunoglobulin V region gene segments and are a powerful tool to rapidly isolate human monoclonal antibodies. After immunizing these mice with DNA encoding the spike protein of SARS‐CoV‐2 and boosting with spike protein, we identified 29 hybridoma antibodies that reacted with the SARS‐CoV‐2 spike protein. Nine antibodies neutralize SARS‐CoV‐2 infection at IC50 values in the subnanomolar range. ELISA‐binding studies and DNA sequence analyses revealed one cluster of three clonally related neutralizing antibodies that target the receptor‐binding domain and compete with the cellular receptor hACE2. A second cluster of six clonally related neutralizing antibodies bind to the N‐terminal domain of the spike protein without competing with the binding of hACE2 or cluster 1 antibodies. SARS‐CoV‐2 mutants selected for resistance to an antibody from one cluster are still neutralized by an antibody from the other cluster. Antibodies from both clusters markedly reduced viral spread in mice transgenic for human ACE2 and protected the animals from SARS‐CoV‐2‐induced weight loss. The two clusters of potent non‐competing SARS‐CoV‐2 neutralizing antibodies provide potential candidates for therapy and prophylaxis of COVID‐19. The study further supports transgenic animals with a human immunoglobulin gene repertoire as a powerful platform in pandemic preparedness initiatives. This article is protected by copyright. All rights reserved

Most subjects develop antibodies to SARS‐CoV‐2 following infection. In order to estimate the duration of immunity induced by SARS‐CoV‐2 it is important to understand for how long antibodies persist after infection in humans. Here, we assessed the persistence of serum antibodies following WT SARS‐CoV‐2 infection at 8 and 13 months after diagnosis in 367 individuals. The SARS‐CoV‐2 spike IgG (S‐IgG) and nucleoprotein IgG (N‐IgG) concentrations and the proportion of subjects with neutralizing antibodies (NAb) were assessed. Moreover, the NAb titers among a smaller subset of participants (n = 78) against a WT virus (B) and variants of concern (VOCs): Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.2) were determined. We found that NAb against the WT virus persisted in 89% and S‐IgG in 97% of subjects for at least 13 months after infection. Only 36% had N‐IgG by 13 months. The mean S‐IgG concentrations declined from 8 to 13 months by less than one third; N‐IgG concentrations declined by two‐thirds. Subjects with severe infection had markedly higher IgG and NAb levels and are expected to remain seropositive for longer. Significantly lower NAb titers against the variants compared to the WT virus, especially after a mild disease, suggests reduced protection against VOCs., A year after WT SARS‐CoV‐2 infection high seropositivity rate was observed: 89% of subjects had persisting neutralizing antibodies and up to 97% had anti‐spike IgG antibodies. Compared to the WT virus, neutralizing antibody titers were reduced for variants of concern Alpha, Beta, and Delta.

日本薬剤師研修センター集合研修認定講座（2単位） 開催日時：令和3年10月16日(土) 14時00分～18時00分 会場：22号館404教室 主催：城西大学薬学部、城西国際大学薬学部. 共催：日本薬剤師研修センター、城西大学薬友会、城西大学同窓会. 協賛：公益社団法人日本薬学会、一般社団法人埼玉県薬剤師会、一般社団法人埼玉県病院薬剤師会、一般社団法人日本女性薬剤師会. 後援：城西大学父母後援会、城西大学薬学協力会、TJUP : 埼玉県東上地域大学教育プラットフォーム. テーマ：「感染症と免疫について考える―基礎と臨床」 演題1「感染症に対する生体防御反応の基礎」 演者：城西大学薬学部 客員教授 辻 勉 先生 p.1 演題2「新型コロナウイルス感染症病棟における薬学的管理の実際」 演者：埼玉医科大学総合医療センター 薬剤部 課長 大澤 雄一郎 先生 p.9 演題3「中小病院におけるCOVID-19への対応－発熱外来を中心に－」 演者：シャローム病院 外科部長・外来診療部長 小澤修太郎 先生 p.15. 薬学部生涯教育講座テーマ・演者一覧（過去10回） p.20

ATP-binding cassette (ABC) transporters represent a heterogeneous group of ATP-dependent transport proteins, which facilitate the import and/or export of various substrates, including lipids, sugars, amino acids and peptides, ions, and drugs. ABC transporters are involved in a variety of physiological processes in different human tissues. More recent studies have demonstrated that ABC transporters also regulate the development and function of different T cell populations, such as thymocytes, Natural Killer T cells, CD8+ T cells, and CD4+ T helper cells, including regulatory T cells. Here, we review the current knowledge on ABC transporters in these T cell populations by summarizing how ABC transporters regulate the function of the individual cell types and how this affects the immunity to viruses and tumors, and the course of autoimmune diseases. Furthermore, we provide a perspective on how a better understanding of the function of ABC transporters in T cells might provide promising novel avenues for the therapy of autoimmunity and to improve immunity to infection and cancer.

Optimal vaccines are needed for sustained suppression of SARS‐CoV‐2 and other novel coronaviruses. Here, we developed a recombinant type 5 adenovirus vector encoding the gene for the SARS‐CoV‐2 S1 subunit antigen (Ad5.SARS‐CoV‐2‐S1) for COVID‐19 immunization and evaluated its immunogenicity in mice. A single immunization with Ad5.SARS‐CoV‐2‐S1 via S.C. injection or I.N delivery induced robust antibody and cellular immune responses. Vaccination elicited significant S1‐specific IgG, IgG1, and IgG2a endpoint titers as early as 2 weeks, and the induced antibodies were long lasting. I.N. and S.C. administration of Ad5.SARS‐CoV‐2‐S1 produced S1‐specific GC B cells in cervical and axillary LNs, respectively. Moreover, I.N. and S.C. immunization evoked significantly greater antigen‐specific T‐cell responses compared to unimmunized control groups with indications that S.C. injection was more effective than I.N. delivery in eliciting cellular immune responses. Mice vaccinated by either route demonstrated significantly increased virus‐specific neutralization antibodies on weeks 8 and 12 compared to control groups, as well as BM antibody forming cells (AFC), indicative of long‐term immunity. Thus, this Ad5‐vectored SARS‐CoV‐2 vaccine candidate showed promising immunogenicity following delivery to mice by S.C. and I.N. routes of administration, supporting the further development of Ad‐based vaccines against COVID‐19 and other infectious diseases for sustainable global immunization programs., Vaccine development against SARS‐CoV‐2 addresses the ongoing challenges posed by this pathogen and ensures preparedness for future outbreaks of coronaviruses. Subcutaneous or intranasal administration of Ad5.SARS‐CoV‐2 S1 results in multifaceted immune responses in mice, including GCs and long‐lived antibody forming cells, representing an attractive COVID‐19 vaccination strategy.

The innate immune response generated against influenza infection is critical for the inhibition of viral dissemination. The trachea contains different types of innate immune cells that protect the respiratory tract from pathogen invasion. Among them, γδ T cells have the ability to rapidly generate large amounts of pro‐inflammatory cytokines to preserve mucosal barrier homeostasis during infection. However, little is known about their role during the early phase of influenza infection in the airways. In this study, we found that, early after infection, γδ T cells are recruited and activated in the trachea and outnumber αβ T cells during the course of the influenza infection that follows. We also showed that the majority of the recruited γδ T cells express the Vγ4 TCR chain and infiltrate in a process that involves the chemokine receptor CXCR3. In addition, we demonstrated that γδ T cells promote the recruitment of protective neutrophils and NK cells to the tracheal mucosa. Altogether, our results highlight the importance of the immune responses mediated by γδ T cells., Innate recognition of influenza virus infection is critical for the control of the viral dissemination. Among the innate immune cells recruited to the infected trachea, Vγ4 + γδ T cells rapidly secrete IL‐17A that contributes to neutrophil recruitment and the elimination of virus‐infected cells from the trachea.

Persistent virus infections with non‐ or poorly cytopathic viruses are commonly associated with B cell dysregulations. These include the induction of hypergammaglobulinemia and the emergence of virus‐unspecific antibodies. These seemingly unspecific antibody responses interfere with the virus‐specific humoral immunity and contribute to delayed virus control. Whether these virus‐unspecific antibodies are induced in the B cell follicle or at extrafollicular sites and whether one specific CD4 T cell subset is involved in the polyclonal B cell activation is unclear. Here we studied virus‐unrelated IgG antibody responses against self or foreign antigens in the context of persistent lymphocytic choriomeningitis virus (LCMV) infection. We found that the LCMV‐unspecific antibody response is short‐lived and induced predominantly at extrafollicular sites and depends on the presence of LCMV‐specific CD4 T cells. Our data support a scenario in which activated, virus‐specific CD4 T cells provide help to non‐specific B cells at extrafollicular sites, supporting the production of virus unspecific IgG antibodies during persistent viral infection., Chronic LCMV infection induces an LCMV‐unspecific antibody (IgG) response, which is short‐lived, and is induced predominantly at extrafollicular sites. This unspecific IgG response depends on the presence of LCMV‐specific CD4 T cells.

The helminth Schistosoma mansoni (S. mansoni) induces a network of regulatory immune cells, including interleukin (IL)-10-producing regulatory B (Breg) cells. However, the signals required for the development and activation of Breg cells are not well characterized. Recent reports suggest that helminths induce type I interferons (IFN-I), and that IFN-I drives the development of Breg cells in humans. We therefore assessed the role of IFN-I in the induction of Breg cells by S. mansoni. Mice chronically infected with S.mansoni or intravenously injected with S.mansoni soluble egg antigen (SEA) developed a systemic IFN-I signature. Recombinant IFNα enhanced IL-10 production by Breg cells stimulated with S. mansoni soluble egg antigen (SEA) in vitro, while not activating Breg cells by itself. IFN-I signalling also supported ex vivo IL-10 production by SEA-primed Breg cells but was dispensable for activation of S. mansoni egg-induced Breg cells in vivo. These data indicate that while IFN-I can serve as a co-activator for Breg cell IL-10 production, they are unlikely to participate in the development of Breg cells in response to S. mansoni eggs. This article is protected by copyright. All rights reserved.

Non‐typeable Haemophilus influenzae (NTHi) is a pathogen that commonly colonizes the nasopharynx of preschool children, causing opportunistic infections including acute otitis media (AOM). Patients suffering from chronic obstructive pulmonary disease (COPD) are persistently colonized with NTHi and occasionally suffer from exacerbations by the bacterium leading to increased morbidity. Elongation‐factor thermo unstable (EF‐Tu), a protein critical for bacterial protein synthesis, has been found to moonlight on the surface of several bacteria. Here, we show that antibodies against NTHi EF‐Tu were present in children already at 18 months of age, and that the IgG antibody titers increased with age. Children harboring NTHi in the nasopharynx also displayed significantly higher IgG concentrations. Interestingly, children suffering from AOM had significantly higher anti‐EF‐Tu IgG levels when NTHi was the causative agent. Human sera recognized mainly the central and C‐terminal part of the EF‐Tu molecule and peptide‐based epitope mapping confirmed similar binding patterns for sera from humans and immunized mice. Immunization of BALB/c and otitis‐prone Junbo (C3H/HeH) mice promoted lower infection rates in the nasopharynx and middle ear, respectively. In conclusion, our results suggest that IgG directed against NTHi EF‐Tu may play an important role in the host immune response against NTHi.

Changes in the epigenetic landscape of immune cells are a crucial component of gene activation during the induction of inflammatory responses, therefore it has been hypothesized that epigenetic modulation could be employed to restore homeostasis in inflammatory scenarios. Fungal pathogens cause a large burden of morbidity and even mortality due to the hyperinflammatory processes that induce mucosal, allergic or systemic infections. Bromodomain and extraterminal domain (BET) proteins are considered as one as the most tantalizing pharmacological targets for the modulation of inflammatory responses at the epigenetic level. Nothing is known of the role of BET inhibitors on the inflammation induced by fungal pathogens. In the present study, we assessed the in vitro efficacy of the small molecular histone mimic BET inhibitor I‐BET151 to modulate innate immune responses during fungal–immune interaction with the clinically relevant fungal pathogens Candida albicans and Aspergillus fumigatus. Our results prove that BET inhibitors (I‐BETs) represent an important modulator of inflammation induced by fungal pathogens: both direct production of proinflammatory cytokines and the induction of trained immunity were inhibited by I‐BET151. These modulatory effects are likely to have important potential implications in clinically relevant situations., Treatment of immune cells with the clinically relevant small molecular histone mimic BET inhibitor I‐BET151 allows the modulation of immune responses during fungal–immune interaction through the reprogramming of the epigenetic landscape of the cells, decreasing the production of pro‐inflammatory cytokines and inhibiting the induction of trained immunity.

Treatment with convalescent plasma has been shown to be safe in coronavirus disease in 2019 (COVID‐19) infection, although efficacy reported in immunocompetent patients varies. Nevertheless, neutralizing antibodies are a key requisite in the fight against viral infections. Patients depleted of antibody‐producing B cells, such as those treated with rituximab (anti‐CD20) for hematological malignancies, lack a fundamental part of their adaptive immunity. Treatment with convalescent plasma appears to be of general benefit in this particularly vulnerable cohort. We analyzed clinical course and inflammation markers of three B‐cell‐depleted patients suffering from COVID‐19 who were treated with convalescent plasma. In addition, we measured serum antibody levels as well as peripheral blood CD38/HLA‐DR‐positive T‐cells ex vivo and CD137‐positive T‐cells after in vitro stimulation with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)‐derived peptides in these patients. We observed that therapy with convalescent plasma was effective in all three patients and analysis of CD137‐positive T‐cells after stimulation with SARS‐CoV‐2 peptides showed an increase in peptide‐specific T‐cells after application of convalescent plasma. In conclusion, we here demonstrate efficacy of convalescent plasma therapy in three B‐cell‐depleted patients and present data that suggest that while application of convalescent plasma elevates systemic antibody levels only transiently, it may also boost specific T‐cell responses., Treatment of B‐cell depleted patients suffering from COVID‐19 with convalescent plasma led to viral clearance and was followed by an increase in peptide‐specific CD4+ T‐cells suggesting that transient antibody titers promoted specific cellular immunity in these patients.

Here, we describe a new, simple, highly multiplexed serological test that generates a more complete picture of seroconversion than single antigen-based assays. Flow cytometry is used to detect multiple Ig isotypes binding to four SARS-CoV-2 antigens: the Spike glycoprotein, its RBD fragment (the main target for neutralizing antibodies), the nucleocapsid protein, and the main cysteine-like protease in a single reaction. Until now, most diagnostic serological tests measured antibodies to only one antigen and in some laboratory-confirmed patients no SARS-CoV-2-specific antibodies could be detected. Our data reveal that while most patients respond against all the viral antigens tested, others show a marked bias to make antibodies against either proteins exposed on the viral particle or those released after cellular infection. With this assay, it was possible to discriminate between patients and healthy controls with 100% confidence. Analysing the response of multiple Ig isotypes to the four antigens in combination may also help to establish a correlation with the severity degree of disease. A more detailed description of the immune responses of different patients to SARS-CoV-2 virus might provide insight into the wide array of clinical presentations of COVID-19., This work was supported by: Spanish National Research Council (CSIC-202020E079, CSIC-COVID19-028); Madrid Regional Government “IMMUNOTHERCAN” [S2017/BMD-3733-2 (MVG)]; Spanish Ministry of Science and Innovation [(MCIU/AEI/FEDER, EU, RTI2018-093569-B-I00 (MVG), SAF2017-82940-R (JMRF), SAF2017-83265-R (HTR); SAF2017-82886-R (FSM)]; Health Institute Carlos III (ISCIII) [RETICS Program RD16/0012/0006; RIER (EMGC); PI19/00549 (AA)]; “La Caixa Bank Foundation” (HR17-00016), Fondo Supera COVID (CRUE-Banco de Santander), both to FSM.

Heterologous polyclonal antibodies might represent an alternative to the use of convalescent plasma or monoclonal antibodies (mAbs) in coronavirus disease (COVID‐19) by targeting multiple antigen epitopes. However, heterologous antibodies trigger human natural xenogeneic antibody responses particularly directed against animal‐type carbohydrates, mainly the N‐glycolyl form of the neuraminic acid (Neu5Gc) and the α1,3‐galactose, potentially leading to serum sickness or allergy. Here, we immunized cytidine monophosphate‐N‐acetylneuraminic acid hydroxylase and α1,3‐galactosyl‐transferase (GGTA1) double KO pigs with the Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spike receptor binding domain to produce glyco‐humanized polyclonal neutralizing antibodies lacking Neu5Gc and α1,3‐galactose epitopes. Animals rapidly developed a hyperimmune response with anti‐SARS‐CoV‐2 end‐titers binding dilutions over one to a million and end‐titers neutralizing dilutions of 1:10 000. The IgG fraction purified and formulated following clinical Good Manufacturing Practices, named XAV‐19, neutralized spike/angiotensin converting enzyme‐2 interaction at a concentration, GGTA1/CMAH double KO pigs produced high titers of XAV‐19, an anti‐SARS‐Cov‐2 RBD glyco‐humanized polyclonal antibody. XAV‐19 is presented with a high complement activation and a high neutralization potency in vitro and in cell‐based neutralization assays. XAV‐19 does not interact with human Fc gamma receptors, preventing Fc‐dependent enhancement or immune cells skewing.

The interferon pathway, a key antiviral defense mechanism, is being considered as a therapeutic target in COVID‐19. Both, substitution of interferon and JAK/STAT inhibition to limit cytokine storms have been proposed. However, little is known about possible abnormalities in STAT signaling in immune cells during SARS‐CoV‐2 infection. We investigated downstream targets of interferon signaling, including STAT1, STAT2, pSTAT1 and 2, and IRF1, 7 and 9 by flow cytometry in 30 patients with COVID‐19, 17 with mild, and 13 with severe infection. We report upregulation of STAT1 and IRF9 in mild and severe COVID‐19 cases, which correlated with the IFN‐signature assessed by Siglec‐1 (CD169) expression on peripheral monocytes. Interestingly, Siglec‐1 and STAT1 in CD14+ monocytes and plasmablasts showed lower expression among severe cases compared to mild cases. Contrary to the baseline STAT1 expression, the phosphorylation of STAT1 was enhanced in severe COVID‐19 cases, indicating a dysbalanced JAK/STAT signaling that fails to induce transcription of interferon stimulated response elements (ISRE). This abnormality persisted after IFN‐α and IFN‐γ stimulation of PBMCs from patients with severe COVID‐19. Data suggest impaired STAT1 transcriptional upregulation among severely infected patients may represent a potential predictive biomarker and would allow stratification of patients for certain interferon‐pathway targeted treatments., Anomalous upregulation of STAT1 and IRF9 (key components of IFN signaling) in B and T cells and monocytes from patients with severe COVID‐19, with absence of pSTAT1 upregulation upon IFN restimulation. Mild COVID‐19 group had strong STAT1 and IRF9 upregulation. image, publishedVersion

Growing evidence suggests that conventional dendritic cells (cDCs) undergo aberrant maturation in COVID‐19, which negatively affects T‐cell activation. The presence of effector T cells in patients with mild disease and dysfunctional T cells in severely ill patients suggests that adequate T‐cell responses limit disease severity. Understanding how cDCs cope with SARS‐CoV‐2 can help elucidate how protective immune responses are generated. Here, we report that cDC2 subtypes exhibit similar infection‐induced gene signatures, with the upregulation of interferon‐stimulated genes and interleukin (IL)‐6 signaling pathways. Furthermore, comparison of cDCs between patients with severe and mild disease showed severely ill patients to exhibit profound downregulation of genes encoding molecules involved in antigen presentation, such as MHCII, TAP, and costimulatory proteins, whereas we observed the opposite for proinflammatory molecules, such as complement and coagulation factors. Thus, as disease severity increases, cDC2s exhibit enhanced inflammatory properties and lose antigen presentation capacity. Moreover, DC3s showed upregulation of anti‐apoptotic genes and accumulated during infection. Direct exposure of cDC2s to the virus in vitro recapitulated the activation profile observed in vivo. Our findings suggest that SARS‐CoV‐2 interacts directly with cDC2s and implements an efficient immune escape mechanism that correlates with disease severity by downregulating crucial molecules required for T‐cell activation. This article is protected by copyright. All rights reserved

International audience; Background Although the COVID-19 pandemic peaked in March/April 2020 in France, the prevalence of infection is barely known. Herein, we assessed the serological response against the SARS-CoV-2 virus in a large population working in one institution of the Paris conurbation. We set up two high-throughput and sensitive methods to assess SARS CoV-2 Nucleoprotein and Spike protein-specific IgG response along with a pseudo-neutralization assay in sera. We studied 1847 participants who also answered a web-based survey on clinical symptoms.Methods and Results In May-July 2020, 11% (95% CI: 9.7-12.6) of serums were positive for IgG against the SARS-CoV-2 N and S protein and 9.5% (CI:8.2-11.0) were pseudo-neutralizer. The prevalence of immunization was 11.6% (CI:10.2-13.2) considering positivity in at least one assays. In 5% (CI:3.9-7.1) of RT-qPCR positive individuals, no systemic IgGs were detected. Among immune individuals, 21% had been asymptomatic.Anosmia and ageusia occurred in 52% of the IgG-positive individuals and in 3% of the negative ones. In contrast, 30% of the anosmia-ageusia cases were seronegative suggesting that the true prevalence of infection may reach 16.6%. In sera obtained 4-8 weeks after the first sampling anti-N and anti-S IgG titers and pseudo-neutralization activity declined by 31%, 17% and 53%, respectively with half-life of 35, 87 and 28 days, respectively.Conclusions The population studied being not particularly exposed to SARS-CoV-2 infection is representative of active workers in the Paris conurbation, suggesting that the current epidemiological models may underestimate the true prevalence of infection. The short lifespan of the serological systemic responses hinders retrospective assessment of the epidemic extent.

Humoral immunity to the Severe Adult Respiratory Syndrome (SARS) Coronavirus (CoV)‐2 is not fully understood yet but is a crucial factor of immune protection. The possibility of antibody cross‐reactivity between SARS‐CoV‐2 and other human coronaviruses (HCoVs) would have important implications for immune protection but also for the development of specific diagnostic ELISA tests. Using peptide microarrays, n = 24 patient samples and n = 12 control samples were screened for antibodies against the entire SARS‐CoV‐2 proteome as well as the Spike (S), Nucleocapsid (N), VME1 (V), R1ab, and Protein 3a (AP3A) of the HCoV strains SARS, MERS, OC43, and 229E. While widespread cross‐reactivity was revealed across several immunodominant regions of S and N, IgG binding to several SARS‐CoV‐2‐derived peptides provided statistically significant discrimination between COVID‐19 patients and controls. Selected target peptides may serve as capture antigens for future, highly COVID‐19‐specific diagnostic antibody tests., SARS‐CoV‐2 whole‐proteome peptide microarray analysis of antibody reactivity in Covid‐19 patient sera revealed several epitopes and confirmed the presence of humoral cross‐reactivity between SARS‐CoV‐2 and ubiquitous “common cold” human coronaviruses. The identified epitopes may provide the basis for the development of a specific and sensitive diagnostic test.

SARS‐CoV‐2 infection causes an abrupt response by the host immune system, which is largely responsible for the outcome of COVID‐19. We investigated whether the specific immune responses in the peripheral blood of 276 patients associated to severity and progression of COVID‐19. At admission, dramatic lymphopenia of T, B and NK cells associated to severity. Conversely, the proportion of B cells, plasmablasts, circulating follicular helper T cells (cTfh) and CD56‐CD16+ NK‐cells increased. Regarding humoral immunity, levels of IgM, IgA and IgG were unaffected, but when degrees of severity were considered, IgG was lower in severe patients. Compared to healthy donors, complement C3 and C4 protein levels were higher in mild and moderate, but not in severe patients, while the activation peptide of C5 (C5a) increased from the admission in every patient, regardless their severity. Moreover, total IgG, the IgG1 and IgG3 isotypes and C4 decreased from day 0 to day 10 in patients who were hospitalized for more than two weeks, but not in patients who were discharged earlier. Our study provides important clues to understand the immune response observed in COVID‐19 patients, associating severity with an imbalanced humoral response and identifying new targets for therapeutic intervention., The study was funded by grants SAF2017-82886-R to FS-M from the Ministerio de Economía y Competitividad, and from “La Caixa Banking Foundation” (HR17-00016) to FS-M. Grant PI018/01163 to CMC and grant PI19/00549 to AA were funded by Fondo de Investigaciones Sanitarias, Ministerio de Sanidad y Consumo, Spain. SAF2017-82886-R, PI018/01163 and PI19/00549 grants were also cofunded by European Regional Development Fund, ERDF/FEDER. This work has been funded by grants Fondo Supera COVID (CRUE-Banco de Santander) to FSM, and “Ayuda Covid 2019” from Comunidad de Madrid.

© 2020 The Authors. European Journal of Immunology published by Wiley‐VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., SARS-CoV-2 has emerged as a human pathogen, causing clinical signs, from fever to pneumonia-COVID-19-but may remain mild or asymptomatic. To understand the continuing spread of the virus, to detect those who are and were infected, and to follow the immune response longitudinally, reliable and robust assays for SARS-CoV-2 detection and immunological monitoring are needed. We quantified IgM, IgG, and IgA antibodies recognizing the SARS-CoV-2 receptor-binding domain (RBD) or the Spike (S) protein over a period of 6 months following COVID-19 onset. We report the detailed setup to monitor the humoral immune response from over 300 COVID-19 hospital patients and healthcare workers, 2500 University staff, and 198 post-COVID-19 volunteers. Anti-SARS-CoV-2 antibody responses follow a classic pattern with a rapid increase within the first three weeks after symptoms. Although titres reduce subsequently, the ability to detect anti-SARS-CoV-2 IgG antibodies remained robust with confirmed neutralization activity for up to 6 months in a large proportion of previously virus-positive screened subjects. Our work provides detailed information for the assays used, facilitating further and longitudinal analysis of protective immunity to SARS-CoV-2. Importantly, it highlights a continued level of circulating neutralising antibodies in most people with confirmed SARS-CoV-2., We like to acknowledge the funding from the European Union H2020 ERA project (No 667824 – EXCELLtoINNOV) and the Fundação para a Ciência e a Tecnologia (FCT) to P.F‐C. (SFRH/BD/131605/2017), PTDC/MED‐IMU/28003/2017, and research4COVID19 (no. 231_596873172, Generating SARS‐CoV2 seroconversion assay and no. 729, High‐throughput SARS‐CoV2 neutralizing antibodies assessment), with additional support by Sociedade Francisco Manuel dos Santos.

Epstein–Barr virus (EBV) infection of B cells is associated with increased multiple sclerosis (MS) susceptibility. Recently, we found that CXCR3‐expressing B cells preferentially infiltrate the CNS of MS patients. In chronic virus‐infected mice, these types of B cells are sustained and show increased antiviral responsiveness. How EBV persistence in B cells influences their development remains unclear. First, we analyzed ex vivo B‐cell subsets from MS patients who received autologous bone marrow transplantation (n = 9), which is often accompanied by EBV reactivation. The frequencies of nonclass‐switched and class‐switched memory B cells were reduced at 3–7 months, while only class‐switched B cells returned back to baseline at 24–36 months posttransplantation. At these time points, EBV DNA load positively correlated to the frequency of CXCR3+, and not CXCR4+ or CXCR5+, class‐switched B cells. Second, for CXCR3+ memory B cells trapped within the blood of MS patients treated with natalizumab (anti‐VLA‐4 antibody n = 15), latent EBV infection corresponded to enhanced in vitro formation of anti‐EBNA1 IgG‐secreting plasma cells under GC‐like conditions. These findings imply that EBV persistence in B cells potentiates brain‐homing and antibody‐producing CXCR3+ subsets in MS., Using blood samples from autologous BMT‐ and natalizumab‐treated MS patients, we demonstrate that high B‐cell EBV load associates with the development of CXCR3+ class‐switched B cells (ex vivo) and plasma cells under IL‐21‐, CD40L‐ and IFN‐γ‐inducing conditions (in vitro). CXCR3 expression on these plasma cells correlated with enhanced EBNA1‐IgG secretion.

The autosomal‐dominant hyper‐IgE syndrome (HIES), caused by mutations in STAT3, is a rare primary immunodeficiency that predisposes to mucocutaneous candidiasis and staphylococcal skin and lung infections. This infection phenotype is suggestive of defects in neutrophils, but data on neutrophil functions in HIES are inconsistent. This study was undertaken to functionally characterize neutrophils in STAT3‐deficient HIES patients and to analyze whether the patients` eosinophilia affects the neutrophil phenotype in S. aureus infection. Neutrophil functions and cell death kinetics were studied in eight STAT3‐deficient patients. Moreover, the response of STAT3‐deficient neutrophils to S. aureus and the impact of autologous eosinophils on pathogen‐induced cell death were analyzed. No specific aberrations in neutrophil functions were detected within this cohort. However, the half‐life of STAT3‐deficient neutrophils ex vivo was reduced, which was partially attributable to the presence of eosinophils. Increased S. aureus‐induced cell lysis, dependent on the staphylococcal virulence controlling accessory gene regulator (agr)‐locus, was observed in STAT3‐deficient neutrophils and upon addition of eosinophils. Accelerated neutrophil cell death kinetics may underlie the reported variability in neutrophil function testing in HIES. Increased S. aureus‐induced lysis of STAT3‐deficient neutrophils might affect pathogen control and contribute to tissue destruction during staphylococcal infections in HIES.

Type I interferons (IFNs) induce a detrimental response during Listeria monocytogenes (L. monocytogenes) infection. We were interested in identifying mechanisms linking IFN signaling to negative host responses against L. monocytogenes infection. Herein, we found that infection of myeloid cells with L. monocytogenes led to a coordinated induction of type I IFNs and activation of the integrated stress response (ISR). Infected cells did not induce Xbp1 splicing or BiP upregulation, indicating that the unfolded protein response was not triggered. CHOP (Ddit3) gene expression was upregulated during the ISR activation induced by L. monocytogenes. Myeloid cells deficient in either type I IFN signaling or PKR activation had less upregulation of CHOP following infection. CHOP‐deficient mice showed lower expression of innate immune cytokines and were more resistant than wild‐type counterparts following L. monocytogenes infection. These findings indicate that L. monocytogenes infection induces type I IFNs, which activate the ISR through PKR, which contributes to a detrimental outcome in the infected host.

Human cytomegalovirus (HCMV) infection drives the phenotypic and functional differentiation of NK cells, thereby influencing the responses of these cells after vaccination. NK cell functional differentiation is particularly advanced in African populations with universal exposure to HCMV. To investigate the impact of advanced differentiation on vaccine-induced responses, we studied NK-cell function before and after vaccination with Trivalent Influenza Vaccine (TIV) or diphtheria, tetanus, pertussis, inactivated poliovirus vaccine (DTPiP) in Africans with universal, lifelong HCMV exposure. In contrast to populations with lower prevalence of HCMV infection, no significant enhancement of NK-cell responses (IFN-γ, CD107a, CD25) occurred after in vitro re-stimulation of post-vaccination NK cells with TIV or DTPiP antigens compared to pre-vaccination baseline cells. However, both vaccinations resulted in higher frequencies of NK cells producing IFN-γ in response to exogenous IL-12 with IL-18, which persisted for up to 6 months. Enhanced cytokine responsiveness was restricted to less differentiated NK cells, with increased frequencies of IFN-γ+ cells observed within CD56bright CD57- , CD56dim CD57- NKG2C- and CD56dim CD57- NKG2C+ NK-cell subsets. These data suggest a common mechanism whereby different vaccines enhance NK cell IFN-γ function in HCMV infected donors and raise the potential for further exploitation of NK cell "pre-activation" to improve vaccine effectiveness.

The IL‐7 receptor specific α chain, CD127, can be expressed both as a membrane‐associated (mCD127) and a soluble form (sCD127), however, the mechanisms involved in their regulation remain to be defined. We first demonstrated in primary human CD8+ T cells that IL‐7‐induced downregulation of mCD127 expression is dependent on JAK and PI3K signaling, whereas IL‐7‐induced sCD127 release is also mediated by STAT5. Following stimulation with IL‐7, expression of alternatively spliced variants of the CD127 gene, sCD127 mRNA, is reduced, but to a lesser degree than the full‐length gene. Evaluation of the role of proteases revealed that MMP‐9 was involved in sCD127 release, without affecting the expression of mCD127, suggesting it does not induce direct shedding from the cell surface. Since defects in the IL‐7/CD127 pathway occur in various diseases, including HIV, we evaluated CD8+ T cells derived from HAART‐treated HIV‐infected individuals and found that IL‐7‐induced (1) downregulation of mCD127, (2) release of sCD127, and (3) expression of the sCD127 mRNA were all impaired. Expression of mCD127 and sCD127 is, therefore, regulated by distinct, but overlapping, mechanisms and their impairment in HIV infection contributes to our understanding of the CD8+ T cell dysfunction that persists despite effective antiretroviral therapy., IL‐7 induces sCD127 release through JAK, STAT5, and PI3K signaling, whereas IL‐7‐induced downregulation of mCD127 does not involve STAT5. Moreover, IL‐7 causes an increase in the ratio of sCD127/total CD127 mRNA. In HAART‐treated HIV infection, IL‐7‐induced sCD127 release, mCD127 downregulation, and the increased sCD127/total CD127 mRNA ratio are all impaired.

Acquisition of effector functions in T cells is guided by transcription factors including NF-κB that itself is tightly controlled by inhibitory proteins. The atypical NF-κB inhibitor IκBNS is involved in the development of Th1, Th17 and Treg cells. However, it remained unclear to which extend IκBNS contributes to the acquisition of effector function in T cells specifically responding to a pathogen during in vivo infection. Tracking of adoptively transferred T cells in Listeria monocytogenes infected mice uncovered antigen-specific activation of CD4+ T cells following in vivo pathogen encounter to strongly rely on IκBNS . While IκBNS was largely dispensable for the acquisition of cytotoxic effector function in CD8+ T cells, IκBNS -deficient Th1 effector cells exhibited significantly reduced proliferation, marked changes in the pattern of activation marker expression and reduced production of the Th1-cell cytokines IFNγ, IL2 and TNFα. Complementary in vitro analyses using cells from novel reporter and inducible knockout mice revealed that IκBNS predominantly affects the early phase of Th1-cell differentiation while its function in terminally differentiated cells appears to be negligible. Our data suggest IκBNS as a potential target to modulate specifically CD4+ T-cell responses. This article is protected by copyright. All rights reserved.

Diabetes mellitus (DM) is a serious global health problem currently affecting over 450million people worldwide. Defining its interaction with major global infections is an international public health priority. Melioidosis is caused byBurkholderia pseudomallei, an exemplar pathogen for studying intracellular bacterial infection in the context of DM due to the 12‐fold increased risk in this group. We characterized immune correlates of survival in peripheral blood of acute melioidosis patients with and without DM and highlight different immune response patterns. We demonstrate the importance of circulating NK cells and show that CX3CR1 expression on lymphocytes is a novel correlate of survival from acute melioidosis. Furthermore, excessive serum levels of IL‐15 and IL‐18BP contribute to poor outcome independent of DM comorbidity. CD8+Tcells and granzyme B expression in NK cells are important for survival of non‐DM patients, whereas high antibody titers againstB. pseudomalleiand double‐negative Tcells are linked to survival of DM patients. Recall responses support a role of γδ T‐cell‐derived IFN‐γ in the establishment of protective immunity in the DM group. Defining the hallmarks of protection in people with DM is crucial for the design of new therapies and vaccines targeting this rapidly expanding risk group.

Lyme disease is a common multi-system disease caused by infection with a tick-transmitted spirochete, Borrelia burgdorferi and related Borrelia species. The monoglycosylated diacylglycerol known as B. burgdorferi glycolipid II (BbGL-II) is a major target of antibodies in sera from infected individuals. Here we show that CD1b presents BbGL-II to human T cells and that the T cell receptor (TCR) mediates the recognition. However, we did not detect increased frequency of CD1b-BbGL-II binding T cells in the peripheral blood of Lyme disease patients compared to controls. Unexpectedly, mapping the T cell specificity for BbGL-II-like molecules using tetramers and activation assays revealed a concomitant response to CD1b-expressing antigen presenting cells in absence of BbGL-II. Further, among all major classes of self-lipid tested, BbGL-II responsive TCRs show strong cross-reactivity to diacylglycerol, a self-lipid antigen with structural similarities to BbGL-II. Extending prior work on MHC and CD1b, CD1c, and CD1d proteins, this study provides evidence for cross-reactive CD1b-restricted T cell responses to bacterial and self-antigens, and identifies chemically defined targets for future discovery of self and foreign antigen cross-reactive T cells. This article is protected by copyright. All rights reserved.

Influenza virus infection triggers an increase in the number of monocyte‐derived dendritic cells (moDCs) in the respiratory tract, but the role of these cells during antiviral immunity is still unclear. Here we show that during influenza infection, moDCs dominate the late activation of CD8+ T cells and trigger the switch in immunodominance of the CD8+ T‐cell response from acidic polymerase specificity to nucleoprotein specificity. Abrogation of monocyte recruitment or depletion of moDCs strongly compromised host resistance to secondary influenza challenge. These findings underscore a novel function of moDCs in the antiviral response to influenza virus, and have important implications for vaccine design.

The Th17/IL-17 pathway is implicated in the pathogenesis of periodontitis (PD), however the mechanisms are not fully understood. We investigated the mechanism by which the periodontal pathogens Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa) promote a Th17/IL-17 response in vitro, and studied IL-17(+) CD4(+) T-cell frequencies in gingival tissue and peripheral blood from patients with PD versus periodontally healthy controls. Addition of Pg or Aa to monocyte/CD4(+) T-cell co-cultures promoted a Th17/IL-17 response in vitro in a dose- and time-dependent manner. Pg or Aa stimulation of monocytes resulted in increased CD40, CD54 and HLA-DR expression, and enhanced TNF-α, IL-1β, IL-6 and IL-23 production. Mechanistically, IL-17 production in Pg-stimulated co-cultures was partially dependent on IL-1β, IL-23 and TLR2/TLR4 signalling. Increased frequencies of IL-17(+) cells were observed in gingival tissue from patients with PD compared to healthy subjects. No differences were observed in IL-17(+) CD4(+) T-cell frequencies in peripheral blood. In vitro, Pg induced significantly higher IL-17 production in anti-CD3 mAb-stimulated monocyte/CD4(+) T-cell co-cultures from patients with PD compared to healthy controls. Our data suggest that periodontal pathogens can activate monocytes, resulting in increased IL-17 production by human CD4(+) T cells, a process that appears enhanced in patients with PD.

CD200 receptor 1(CD200R1) signalling limits myeloid cell responses and reduces autoimmunity, alloimmunity and viral‐mediated immunopathology, but has never been examined in the context of eosinophilic inflammation. Susceptibility to lung fungal infection is associated with T‐helper 2 (Th2) cytokine dominated responses and strong eosinophilic pathology. Blockade of CD200R1 enhances type I cytokine responses in many infectious and non‐infectious settings and so may promote a more protective response to fungal infection. By contrast, we demonstrate that, rather than promoting type I cytokine responses, CD200R1 blockade enhanced eosinophilia in a mouse model of Cryptococcus neoformans infection, whereas CD200R1 agonism reduced lung eosinophilia – with neither strategy completely altering fungal burden. Thus, we reveal a surprising disconnect between pulmonary eosinophilia and cryptococcal burden and dissemination. This research has 2 important implications. Firstly, a lack of CD200R1 signalling enhances immune responses regardless of cytokine polarisation, and secondly reducing eosinophils does not allow protective immunity to develop in susceptible fungal system. Therefore, agonists of CD200R1 may be beneficial for eosinophilic pathologies.

Interferon gamma (IFN‐γ) plays an important role in the antiviral immune response during respiratory syncytial virus (RSV) infections. Monocytes and T cells are recruited to the site of RSV infection, but it is unclear whether cell‐cell interactions between monocytes and T cells regulate IFN‐γ production. In this study, micro‐array data identified the upregulation of sialic acid‐binding immunoglobulin‐type lectin 1 (Siglec‐1) in human RSV‐infected infants. In vitro, RSV increased expression of Siglec‐1 on healthy newborn and adult monocytes. RSV‐induced Siglec‐1 on monocytes inhibited IFN‐γ production by adult CD4+ T cells. In contrast, IFN‐γ production by RSV in newborns was not affected by Siglec‐1. The ligand for Siglec‐1, CD43, is highly expressed on adult CD4+ T cells compared to newborns. Our data show that Siglec‐1 reduces IFN‐γ release by adult T cells possibly by binding to the highly expressed CD43. The Siglec‐1‐dependent inhibition of IFN‐γ in adults and the low expression of CD43 on newborn T cells provides a better understanding of the immune response against RSV in early life and adulthood.