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Objectives: Methotrexate (MTX) is one of the most commonly used medications to treat rheumatoid arthritis (RA). However, the effect of MTX treatment on cellular immune responses remains incompletely understood. This raises concerns about the vulnerability of these patients to emerging infections and following vaccination., Methods: In the current study, we investigated the impact of MTX treatment in patients with immune-mediated inflammatory disease on B and CD4 T cell SARS-CoV-2 vaccination responses. Eighteen patients with RA and two patients with psoriatic arthritis on MTX monotherapy were included, as well as 10 patients with RA without immunosuppressive treatment, and 29 healthy controls. CD4 T and B cell responses were analysed 7 days and 3-6 months after two SARS-CoV-2 messenger RNA vaccinations. High-dimensional flow cytometry analysis was used to analyse fresh whole blood, an activation-induced marker assay to measure antigen-specific CD4 T cells, and spike probes to study antigen-specific B cells., Results: Seven days following two SARS-CoV-2 vaccinations, total B and T cell counts were similar between MTX-treated patients and controls. In addition, spike-specific B cell frequencies were unaffected. Remarkably, the frequency of antigen-specific CD4 T cells was reduced in patients using MTX and correlated strongly with anti-RBD IgG antibodies. These results suggest that decreased CD4 T cell activity may result in slower vaccination antibody responses in MTX-treated patients., Conclusion: Taken together, MTX treatment reduces vaccine-induced CD4 T cell activation, which correlates with lower antibody responses., Trial Registration Number: NL8900., Competing Interests: Competing interests: FE, GW, SMvH and TWK report (governmental) grants from ZonMw to study immune response after SARS-Cov-2 vaccination in auto-immune diseases. FE also reports grants from Prinses Beatrix Spierfonds, CSL Behring, Kedrion, Terumo BCT, Grifols, Takeda Pharmaceutical and GBS-CIDP Foundation; consulting fees from UCB Pharma and CSl Behring; honoraria from Grifols. All other authors report no disclosures relevant to the manuscript., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Respiratory infections cause significant morbidity and mortality, yet it is unclear why some individuals succumb to severe disease. In patients hospitalized with avian A(H7N9) influenza, we investigated early drivers underpinning fatal disease. Transcriptomics strongly linked oleoyl-acyl-carrier-protein (ACP) hydrolase (OLAH), an enzyme mediating fatty acid production, with fatal A(H7N9) early after hospital admission, persisting until death. Recovered patients had low OLAH expression throughout hospitalization. High OLAH levels were also detected in patients hospitalized with life-threatening seasonal influenza, COVID-19, respiratory syncytial virus (RSV), and multisystem inflammatory syndrome in children (MIS-C) but not during mild disease. In olah -/- mice, lethal influenza infection led to survival and mild disease as well as reduced lung viral loads, tissue damage, infection-driven pulmonary cell infiltration, and inflammation. This was underpinned by differential lipid droplet dynamics as well as reduced viral replication and virus-induced inflammation in macrophages. Supplementation of oleic acid, the main product of OLAH, increased influenza replication in macrophages and their inflammatory potential. Our findings define how the expression of OLAH drives life-threatening viral disease., Competing Interests: Declaration of interests H.A.M. and B.Y.C. consult for Ena Respiratory. A.G.R. received research support from Illumina. P.G.T. is on the SAB of Immunoscape and Cytoagents, consulted for JNJ, received travel support/honoraria from Illumina and 10× Genomics, and has patents related to TCR discovery. J.C.C. and P.G.T. have patents related to treating or reducing severity of viral infections, including SARS-CoV-2., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Messenger RNA (mRNA) vaccines provide robust protection against SARS-CoV-2 in healthy individuals. However, immunity after vaccination of patients with multiple sclerosis (MS) treated with ocrelizumab (OCR), a B cell-depleting anti-CD20 monoclonal antibody, is not yet fully understood., Methods: In this study, deep immune profiling techniques were employed to investigate the immune response induced by SARS-CoV-2 mRNA vaccines in untreated patients with MS (n=21), OCR-treated patients with MS (n=57) and healthy individuals (n=30)., Results: Among OCR-treated patients with MS, 63% did not produce detectable levels of antibodies (non-seroconverted), and those who did have lower spike receptor-binding domain-specific IgG responses compared with healthy individuals and untreated patients with MS. Before vaccination, no discernible immunological differences were observed between non-seroconverted and seroconverted OCR-treated patients with MS. However, non-seroconverted patients received overall more OCR infusions, had shorter intervals since their last OCR infusion and displayed higher OCR serum concentrations at the time of their initial vaccination. Following two vaccinations, non-seroconverted patients displayed smaller B cell compartments but instead exhibited more robust activation of general CD4 + and CD8 + T cell compartments, as indicated by upregulation of CD38 and HLA-DR surface expression, when compared with seroconverted patients., Conclusion: These findings highlight the importance of optimising treatment regimens when scheduling SARS-CoV-2 vaccination for OCR-treated patients with MS to maximise their humoral and cellular immune responses. This study provides valuable insights for optimising vaccination strategies in OCR-treated patients with MS, including the identification of CD38 and HLA-DR as potential markers to explore vaccine efficacy in non-seroconverting OCR-treated patients with MS., Competing Interests: Competing interests: JK received research grants for multicentre investigator-initiated trials (DOT-MS trial, ClinicalTrials.gov Identifier: NCT04260711 (ZonMw) and BLOOMS trial (ZonMw and Treatmeds), ClinicalTrials.gov Identifier: NCT05296161); received consulting fees from F Hoffmann-La Roche, Biogen, Teva, Merck, Novartis and Sanofi/Genzyme (all payments to institution); reports speaker relationships with F Hoffmann-La Roche, Biogen, Immunic, Teva, Merck, Novartis and Sanofi/Genzyme (all payments to institution); and adjudication committee of MS clinical trial of Immunic (payments to institution only)., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Premature lymphocytes develop into non-autoreactive, mature naïve CD4 + or CD8 + T cells in the thymus before entering the circulation. However, in-depth characterization of human thymocyte development remains challenging due to limited availability of human thymus samples and the fragile nature of thymocyte populations. Thymocytes often do not survive cryopreservation and thawing procedures, especially the fragile CD4 + CD8 + double positive population. It is generally recommended to use fresh human thymus tissue on the day of excision to avoid any biases in thymocyte composition. This hampers the possibility to perform multiple experiments on the same thymus sample. To establish how the thymocyte viability and composition can be maintained, we compared two thymocyte isolation methods used for human and/or mice thymi, three cryopreservation methods in combination with our most gentle thawing technique. Based on our findings we established that fresh human thymi remain viable in cold storage for up to two days post-surgery without compromising thymocyte composition. Thymocytes can be cryopreserved if required, although the CD4 + CD8 + double positive populations may be reduced. Our study provides thoroughly optimized methods to study human thymocyte development over a considerable time-frame post-surgery., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Influenza viruses are notorious for their capacity to evade host immunity. Not only can they evade recognition by virus-neutralizing antibodies, there is also evidence that they accumulate mutations in epitopes recognized by virus-specific CD8 + T cells. In addition, we have shown previously that human influenza A viruses were less well recognized than avian influenza viruses by CD8 + T cells directed to the highly conserved, HLA-A*02:01 restricted M1 58-66 epitope located in the Matrix 1 (M1) protein. Amino acid differences at residues outside the epitope were responsible for the differential recognition, and it was hypothesized that this reflected immune adaptation of human influenza viruses to selective pressure exerted by M1 58-66 -specific CD8 + T cells in the human population. In the present study, we tested this hypothesis and investigated if selective pressure exerted by M1 58-66 epitope-specific CD8 + T cells could drive mutations at the extra-epitopic residues in vitro. To this end, isogenic influenza A viruses with the M1 gene of a human or an avian influenza virus were serially passaged in human lung epithelial A549 cells that transgenically express the HLA-A*02:01 molecule or not, in the presence or absence of M1 58-66 epitope-specific CD8 + T cells. Especially in the virus with the M1 gene of an avian influenza virus, variants emerged with mutations at the extra-epitopic residues associated with reduced recognition by M1 58-66 -specific T cells as detected by Next Generation Sequencing. Although the emergence of these variants was observed in the absence of selective pressure exerted by M1 58-66 epitope-specific CD8 + T cells, their proportion was much larger in the presence of this selective pressure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Influenza B viruses (IBVs) cause substantive morbidity and mortality, and yet immunity towards IBVs remains understudied. CD8 + T-cells provide broadly cross-reactive immunity and alleviate disease severity by recognizing conserved epitopes. Despite the IBV burden, only 18 IBV-specific T-cell epitopes restricted by 5 HLAs have been identified currently. A broader array of conserved IBV T-cell epitopes is needed to develop effective cross-reactive T-cell based IBV vaccines. Here we identify 9 highly conserved IBV CD8 + T-cell epitopes restricted to HLA-B*07:02, HLA-B*08:01 and HLA-B*35:01. Memory IBV-specific tetramer + CD8 + T-cells are present within blood and tissues. Frequencies of IBV-specific CD8 + T-cells decline with age, but maintain a central memory phenotype. HLA-B*07:02 and HLA-B*08:01-restricted NP 30-38 epitope-specific T-cells have distinct T-cell receptor repertoires. We provide structural basis for the IBV HLA-B*07:02-restricted NS1 196-206 (11-mer) and HLA-B*07:02-restricted NP 30-38 epitope presentation. Our study increases the number of IBV CD8 + T-cell epitopes, and defines IBV-specific CD8 + T-cells at cellular and molecular levels, across tissues and age., (© 2024. The Author(s).)

SARS-CoV-2-specific CD8 + T cells recognize conserved viral peptides and in the absence of cross-reactive antibodies form an important line of protection against emerging viral variants as they ameliorate disease severity. SARS-CoV-2 mRNA vaccines induce robust spike-specific antibody and T cell responses in healthy individuals, but their effectiveness in patients with chronic immune-mediated inflammatory disorders (IMIDs) is less well defined. These patients are often treated with systemic immunosuppressants, which may negatively affect vaccine-induced immunity. Indeed, TNF inhibitor (TNFi)-treated inflammatory bowel disease (IBD) patients display reduced ability to maintain SARS-CoV-2 antibody responses post-vaccination, yet the effects on CD8 + T cells remain unclear. Here, we analyzed the impact of IBD and TNFi treatment on mRNA-1273 vaccine-induced CD8 + T cell responses compared to healthy controls in SARS-CoV-2 experienced and inexperienced patients. CD8 + T cells were analyzed for their ability to recognize 32 SARS-CoV-2-specific epitopes, restricted by 10 common HLA class I allotypes using heterotetramer combinatorial coding. This strategy allowed in-depth ex vivo profiling of the vaccine-induced CD8 + T cell responses using phenotypic and activation markers. mRNA vaccination of TNFi-treated and untreated IBD patients induced robust spike-specific CD8 + T cell responses with a predominant central memory and activated phenotype, comparable to those in healthy controls. Prominent non-spike-specific CD8 + T cell responses were observed in SARS-CoV-2 experienced donors prior to vaccination. Non-spike-specific CD8 + T cells persisted and spike-specific CD8 + T cells notably expanded after vaccination in these patient cohorts. Our data demonstrate that regardless of TNFi treatment or prior SARS-CoV-2 infection, IBD patients benefit from vaccination by inducing a robust spike-specific CD8 + T cell response., Competing Interests: Declaration of competing interest No conflict of interest to report., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Diabetes mellitus is on the rise globally and is a known susceptibility factor for severe influenza virus infections. However, the mechanisms by which diabetes increases the severity of an influenza virus infection are yet to be fully defined. Diabetes mellitus is hallmarked by high glucose concentrations in the blood. We hypothesized that these high glucose concentrations affect the functionality of CD8 + T cells, which play a key role eliminating virus-infected cells and have been shown to decrease influenza disease severity. To study the effect of hyperglycemia on CD8 + T cell function, we stimulated peripheral blood mononuclear cells (PBMCs) from donors with and without diabetes with influenza A virus, anti-CD3/anti-CD28-coated beads, PMA and ionomycin (PMA/I), or an influenza viral peptide pool. After stimulation, cells were assessed for functionality [as defined by expression of IFN-γ, TNF-α, macrophage inflammatory protein (MIP)-1β, and lysosomal-associated membrane protein-1 (CD107a)] using flow cytometry. Our results showed that increasing HbA1c correlated with a reduction in TNF-α production by CD8 + T cells in response to influenza stimulation in a TCR-specific manner. This was not associated with any changes to CD8 + T cell subsets. We conclude that hyperglycemia impairs CD8 + T cell function to influenza virus infection, which may be linked with the increased risk of severe influenza in patients with diabetes., (© 2024. The Author(s).)

CD8 + T cells provide robust antiviral immunity, but how epitope-specific T cells evolve across the human lifespan is unclear. Here we defined CD8 + T cell immunity directed at the prominent influenza epitope HLA-A*02:01-M1 58-66 (A2/M1 58 ) across four age groups at phenotypic, transcriptomic, clonal and functional levels. We identify a linear differentiation trajectory from newborns to children then adults, followed by divergence and a clonal reset in older adults. Gene profiles in older adults closely resemble those of newborns and children, despite being clonally distinct. Only child-derived and adult-derived A2/M1 58 + CD8 + T cells had the potential to differentiate into highly cytotoxic epitope-specific CD8 + T cells, which was linked to highly functional public T cell receptor (TCR)αβ signatures. Suboptimal TCRαβ signatures in older adults led to less proliferation, polyfunctionality, avidity and recognition of peptide mutants, although displayed no signs of exhaustion. These data suggest that priming T cells at different stages of life might greatly affect CD8 + T cell responses toward viral infections., (© 2023. The Author(s).)

Pregnancy poses a greater risk for severe COVID-19; however, underlying immunological changes associated with SARS-CoV-2 during pregnancy are poorly understood. We defined immune responses to SARS-CoV-2 in unvaccinated pregnant and nonpregnant women with acute and convalescent COVID-19, quantifying 217 immunological parameters. Humoral responses to SARS-CoV-2 were similar in pregnant and nonpregnant women, although our systems serology approach revealed distinct antibody and FcγR profiles between pregnant and nonpregnant women. Cellular analyses demonstrated marked differences in NK cell and unconventional T cell activation dynamics in pregnant women. Healthy pregnant women displayed preactivated NK cells and γδ T cells when compared with healthy nonpregnant women, which remained unchanged during acute and convalescent COVID-19. Conversely, nonpregnant women had prototypical activation of NK and γδ T cells. Activation of CD4+ and CD8+ T cells and T follicular helper cells was similar in SARS-CoV-2-infected pregnant and nonpregnant women, while antibody-secreting B cells were increased in pregnant women during acute COVID-19. Elevated levels of IL-8, IL-10, and IL-18 were found in pregnant women in their healthy state, and these cytokine levels remained elevated during acute and convalescent COVID-19. Collectively, we demonstrate perturbations in NK cell and γδ T cell activation in unvaccinated pregnant women with COVID-19, which may impact disease progression and severity during pregnancy.

Objectives: High-magnitude CD8 + T cell responses are associated with mild COVID-19 disease; however, the underlying characteristics that define CD8 + T cell-mediated protection are not well understood. The antigenic breadth and the immunodominance hierarchies of epitope-specific CD8 + T cells remain largely unexplored and are essential for the development of next-generation broad-protective vaccines. This study identified a broad spectrum of conserved SARS-CoV-2 CD8 + T cell epitopes and defined their respective immunodominance and phenotypic profiles following SARS-CoV-2 infection., Methods: CD8 + T cells from 51 convalescent COVID-19 donors were analysed for their ability to recognise 133 predicted and previously described SARS-CoV-2-derived peptides restricted by 11 common HLA class I allotypes using heterotetramer combinatorial coding, which combined with phenotypic markers allowed in-depth ex vivo profiling of CD8 + T cell responses at quantitative and phenotypic levels., Results: A comprehensive panel of 49 mostly conserved SARS-CoV-2-specific CD8 + T cell epitopes, including five newly identified low-magnitude epitopes, was established. We confirmed the immunodominance of HLA-A*01:01/ORF1ab 1637-1646 and B*07:02/N 105-113 and identified B*35:01/N 325-333 as a third epitope with immunodominant features. The magnitude of subdominant epitope responses, including A*03:01/N 361-369 and A*02:01/S 269-277 , depended on the donors' HLA-I context. All epitopes expressed prevalent memory phenotypes, with the highest memory frequencies in severe COVID-19 donors., Conclusion: SARS-CoV-2 infection induces a predominant CD8 + T memory response directed against a broad spectrum of conserved SARS-CoV-2 epitopes, which likely contributes to long-term protection against severe disease. The observed immunodominance hierarchy emphasises the importance of T cell epitopes derived from nonspike proteins to the overall protective and cross-reactive immune response, which could aid future vaccine strategies., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

Background: Patients affected by different types of autoimmune diseases, including common conditions such as multiple sclerosis (MS) and rheumatoid arthritis (RA), are often treated with immunosuppressants to suppress disease activity. It is not fully understood how the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific humoral and cellular immunity induced by infection and/or upon vaccination is affected by immunosuppressants., Methods: The dynamics of cellular immune reactivation upon vaccination of SARS-CoV-2 experienced MS patients treated with the humanized anti-CD20 monoclonal antibody ocrelizumab (OCR) and RA patients treated with methotrexate (MTX) monotherapy were analyzed at great depth via high-dimensional flow cytometry of whole blood samples upon vaccination with the SARS-CoV-2 mRNA-1273 (Moderna) vaccine. Longitudinal B and T cell immune responses were compared to SARS-CoV-2 experienced healthy controls (HCs) before and 7 days after the first and second vaccination., Results: OCR-treated MS patients exhibit a preserved recall response of CD8 + T central memory cells following first vaccination compared to HCs and a similar CD4 + circulating T follicular helper 1 and T helper 1 dynamics, whereas humoral and B cell responses were strongly impaired resulting in absence of SARS-CoV-2-specific humoral immunity. MTX treatment significantly delayed antibody levels and B reactivation following the first vaccination, including sustained inhibition of overall reactivation marker dynamics of the responding CD4 + and CD8 + T cells., Conclusions: Together, these findings indicate that SARS-CoV-2 experienced MS-OCR patients may still benefit from vaccination by inducing a broad CD8 + T cell response which has been associated with milder disease outcome. The delayed vaccine-induced IgG kinetics in RA-MTX patients indicate an increased risk after the first vaccination, which might require additional shielding or alternative strategies such as treatment interruptions in vulnerable patients., Funding: This research project was supported by ZonMw (The Netherlands Organization for Health Research and Development, #10430072010007), the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement (#792532 and #860003), the European Commission (SUPPORT-E, #101015756) and by PPOC (#20_21 L2506), the NHMRC Leadership Investigator Grant (#1173871)., Competing Interests: NV, RH, Jv, LK, CK, TA, LK, MS, MD, Rd, Nd, Cv, AB, EM, KK, Kv, ES, LB, GW, ST, Zv, LW, TK, FE, TR, Sv, At, Cv No competing interests declared, JK has speaking relationships with Merck, Biogen, TEVA, Sanofi, Genzyme, Roche and Novartis. AmsterdamUMC, location VUmc, MS Center Amsterdam has received financial support for research activities from Merck, Celgene, Biogen, GlaxoSmithKline, Immunic, Roche, Teva, Sanofi, Genzyme, and Novartis, (© 2022, Verstegen et al.)

As the establishment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell memory in children remains largely unexplored, we recruited convalescent COVID-19 children and adults to define their circulating memory SARS-CoV-2-specific CD4 + and CD8 + T cells prior to vaccination. We analyzed epitope-specific T cells directly ex vivo using seven HLA class I and class II tetramers presenting SARS-CoV-2 epitopes, together with Spike-specific B cells. Unvaccinated children who seroconverted had comparable Spike-specific but lower ORF1a- and N-specific memory T cell responses compared with adults. This agreed with our TCR sequencing data showing reduced clonal expansion in children. A strong stem cell memory phenotype and common T cell receptor motifs were detected within tetramer-specific T cells in seroconverted children. Conversely, children who did not seroconvert had tetramer-specific T cells of predominantly naive phenotypes and diverse TCRαβ repertoires. Our study demonstrates the generation of SARS-CoV-2-specific T cell memory with common TCRαβ motifs in unvaccinated seroconverted children after their first virus encounter., Competing Interests: Declaration of interests SARS-CoV-2 serological assays (US Provisional Application #62/994252, 63/018457, 63/020503, and 63/024436) and NDV-based SARS-CoV-2 vaccines (US Provisional Application #63/251020) list F.K. as a co-inventor. F.A. is also a co-inventor of the serological assay patents. Patent applications were submitted by the Icahn School of Medicine at Mount Sinai. Mount Sinai has spun out a company, Kantaro, to market serological tests for SARS-CoV-2. F.K. has consulted for Merck and Pfizer (before 2020) and is currently consulting for Pfizer, Third Rock Ventures, Seqirus, and Avimex. F.K. laboratory collaborates with Pfizer on the animal models of SARS-CoV-2. P.G.T. is on the SAB of Immunoscape and Cytoagents, has consulted for JNJ, received travel support and/or honoraria from Illumina, 10X Genomics, and has patents on TCR discovery and expression. P.S.P. received research grants from Astra Zeneca and Pfizer and has served on advisory boards for Sanofi Pasteur and Seqirus., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Understanding the generation of immunity to SARS-CoV-2 in lymphoid tissues draining the site of infection has implications for immunity to SARS-CoV-2. We performed tonsil biopsies under local anesthesia in 19 subjects who had recovered from SARS-CoV-2 infection 24-225 d previously. The biopsies yielded >3 million cells for flow cytometric analysis in 17 subjects. Total and SARS-CoV-2 spike-specific germinal center B cells, and T follicular helper cells, were readily detectable in human tonsils early after SARS-CoV-2 infection, as assessed by flow cytometry. Responses were higher in samples within 2 mo of infection but still detectable in some subjects out to 7 mo following infection. We conclude the tonsils are a secondary lymphoid organ that develop germinal center responses to SARS-CoV-2 infection and could play a role in the long-term development of immunity., (Copyright © 2022 by The American Association of Immunologists, Inc.)

Objectives: To evaluate whether a third vaccination shows an added effect on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) T-cell responses in patients with multiple sclerosis treated with ocrelizumab or fingolimod., Methods: This is a substudy of a prospective multicenter study on SARS-CoV-2 vaccination in patients with immune-mediated diseases. Patients with MS treated with ocrelizumab, fingolimod, and no disease-modifying therapies and healthy controls were included. The number of interferon (IFN)-γ secreting SARS-CoV-2-specific T cells at multiple time points before and after 3 SARS-CoV-2 vaccinations were evaluated., Results: In ocrelizumab-treated patients (N = 24), IFN-γ-producing SARS-CoV-2-specific T-cell responses were induced after 2 vaccinations with median levels comparable to healthy controls (N = 12) and patients with MS without disease-modifying therapies (N = 10). A third vaccination in ocrelizumab-treated patients (N = 8) boosted T-cell responses that had declined after the second vaccination, but did not lead to higher overall T-cell responses as compared to immediately after a second vaccination. In fingolimod-treated patients, no SARS-CoV-2-specific T cells were detected after second (N = 12) and third (N = 9) vaccinations., Discussion: In ocrelizumab-treated patients with MS, a third SARS-CoV-2 vaccination had no additive effect on the maximal T-cell response but did induce a boost response. In fingolimod-treated patients, no T-cell responses could be detected following both a second and third SARS-CoV-2 vaccination., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

CD8 + T cells are a pivotal part of the immune response to viruses, playing a key role in disease outcome and providing long-lasting immunity to conserved pathogen epitopes. Understanding CD8 + T cell immunity in humans is complex due to CD8 + T cell restriction by highly polymorphic Human Leukocyte Antigen (HLA) proteins, requiring T cell epitopes to be defined for different HLA allotypes across different ethnicities. Here we evaluate strategies that have been developed to facilitate epitope identification and study immunogenic T cell responses. We describe an immunopeptidomics approach to sequence HLA-bound peptides presented on virus-infected cells by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Using antigen presenting cell lines that stably express the HLA alleles characteristic of Indigenous Australians, this approach has been successfully used to comprehensively identify influenza-specific CD8 + T cell epitopes restricted by HLA allotypes predominant in Indigenous Australians, including HLA-A*24:02 and HLA-A*11:01. This is an essential step in ensuring high vaccine coverage and efficacy in Indigenous populations globally, known to be at high risk from influenza disease and other respiratory infections., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Hensen, Illing, Rowntree, Davies, Miller, Tong, Habel, van de Sandt, Flanagan, Purcell, Kedzierska and Clemens.)

Morbidity and mortality rates from seasonal and pandemic influenza occur disproportionately in high-risk groups, including Indigenous people globally. Although vaccination against influenza is recommended for those most at risk, studies on immune responses elicited by seasonal vaccines in Indigenous populations are largely missing, with no data available for Indigenous Australians and only one report published on antibody responses in Indigenous Canadians. We recruited 78 Indigenous and 84 non-Indigenous Australians vaccinated with the quadrivalent influenza vaccine into the Looking into InFluenza T cell immunity - Vaccination cohort study and collected blood to define baseline, early (day 7), and memory (day 28) immune responses. We performed in-depth analyses of T and B cell activation, formation of memory B cells, and antibody profiles and investigated host factors that could contribute to vaccine responses. We found activation profiles of circulating T follicular helper type-1 cells at the early stage correlated strongly with the total change in antibody titers induced by vaccination. Formation of influenza-specific hemagglutinin-binding memory B cells was significantly higher in seroconverters compared with nonseroconverters. In-depth antibody characterization revealed a reduction in immunoglobulin G3 before and after vaccination in the Indigenous Australian population, potentially linked to the increased frequency of the G3m21* allotype. Overall, our data provide evidence that Indigenous populations elicit robust, broad, and prototypical immune responses following immunization with seasonal inactivated influenza vaccines. Our work strongly supports the recommendation of influenza vaccination to protect Indigenous populations from severe seasonal influenza virus infections and their subsequent complications., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

Indigenous people worldwide are at high risk of developing severe influenza disease. HLA-A*24:02 allele, highly prevalent in Indigenous populations, is associated with influenza-induced mortality, although the basis for this association is unclear. Here, we define CD8 + T-cell immune landscapes against influenza A (IAV) and B (IBV) viruses in HLA-A*24:02-expressing Indigenous and non-Indigenous individuals, human tissues, influenza-infected patients and HLA-A*24:02-transgenic mice. We identify immunodominant protective CD8 + T-cell epitopes, one towards IAV and six towards IBV, with A24/PB2 550-558 -specific CD8 + T cells being cross-reactive between IAV and IBV. Memory CD8 + T cells towards these specificities are present in blood (CD27 + CD45RA - phenotype) and tissues (CD103 + CD69 + phenotype) of healthy individuals, and effector CD27 - CD45RA - PD-1 + CD38 + CD8 + T cells in IAV/IBV patients. Our data show influenza-specific CD8 + T-cell responses in Indigenous Australians, and advocate for T-cell-mediated vaccines that target and boost the breadth of IAV/IBV-specific CD8 + T cells to protect high-risk HLA-A*24:02-expressing Indigenous and non-Indigenous populations from severe influenza disease.

To better understand primary and recall T cell responses during coronavirus disease 2019 (COVID-19), it is important to examine unmanipulated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cells. By using peptide-human leukocyte antigen (HLA) tetramers for direct ex vivo analysis, we characterized CD8 + T cells specific for SARS-CoV-2 epitopes in COVID-19 patients and unexposed individuals. Unlike CD8 + T cells directed toward subdominant epitopes (B7/N 257 , A2/S 269 , and A24/S 1,208 ) CD8 + T cells specific for the immunodominant B7/N 105 epitope were detected at high frequencies in pre-pandemic samples and at increased frequencies during acute COVID-19 and convalescence. SARS-CoV-2-specific CD8 + T cells in pre-pandemic samples from children, adults, and elderly individuals predominantly displayed a naive phenotype, indicating a lack of previous cross-reactive exposures. T cell receptor (TCR) analyses revealed diverse TCRαβ repertoires and promiscuous αβ-TCR pairing within B7/N 105 + CD8 + T cells. Our study demonstrates high naive precursor frequency and TCRαβ diversity within immunodominant B7/N 105 -specific CD8 + T cells and provides insight into SARS-CoV-2-specific T cell origins and subsequent responses., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

How innate and adaptive immune responses work in concert to resolve influenza disease is yet to be fully investigated in one single study. Here, we utilize longitudinal samples from patients hospitalized with acute influenza to understand these immune responses. We report the dynamics of 18 important immune parameters, related to clinical, genetic and virological factors, in influenza patients across different severity levels. Influenza disease correlates with increases in IL-6/IL-8/MIP-1α/β cytokines and lower antibody responses. Robust activation of circulating T follicular helper cells correlates with peak antibody-secreting cells and influenza heamaglutinin-specific memory B-cell numbers, which phenotypically differs from vaccination-induced B-cell responses. Numbers of influenza-specific CD8 + or CD4 + T cells increase early in disease and retain an activated phenotype during patient recovery. We report the characterisation of immune cellular networks underlying recovery from influenza infection which are highly relevant to other infectious diseases.

The hallmarks of COVID-19 are higher pathogenicity and mortality in the elderly compared to children. Examining baseline SARS-CoV-2 cross-reactive immunological responses, induced by circulating human coronaviruses (hCoVs), is needed to understand such divergent clinical outcomes. Here we show analysis of coronavirus antibody responses of pre-pandemic healthy children (n = 89), adults (n = 98), elderly (n = 57), and COVID-19 patients (n = 50) by systems serology. Moderate levels of cross-reactive, but non-neutralizing, SARS-CoV-2 antibodies are detected in pre-pandemic healthy individuals. SARS-CoV-2 antigen-specific Fcγ receptor binding accurately distinguishes COVID-19 patients from healthy individuals, suggesting that SARS-CoV-2 infection induces qualitative changes to antibody Fc, enhancing Fcγ receptor engagement. Higher cross-reactive SARS-CoV-2 IgA and IgG are observed in healthy elderly, while healthy children display elevated SARS-CoV-2 IgM, suggesting that children have fewer hCoV exposures, resulting in less-experienced but more polyreactive humoral immunity. Age-dependent analysis of COVID-19 patients, confirms elevated class-switched antibodies in elderly, while children have stronger Fc responses which we demonstrate are functionally different. These insights will inform COVID-19 vaccination strategies, improved serological diagnostics and therapeutics.

SARS-CoV-2 causes a spectrum of COVID-19 disease, the immunological basis of which remains ill defined. We analyzed 85 SARS-CoV-2-infected individuals at acute and/or convalescent time points, up to 102 days after symptom onset, quantifying 184 immunological parameters. Acute COVID-19 presented with high levels of IL-6, IL-18, and IL-10 and broad activation marked by the upregulation of CD38 on innate and adaptive lymphocytes and myeloid cells. Importantly, activated CXCR3 + cT FH 1 cells in acute COVID-19 significantly correlate with and predict antibody levels and their avidity at convalescence as well as acute neutralization activity. Strikingly, intensive care unit (ICU) patients with severe COVID-19 display higher levels of soluble IL-6, IL-6R, and IL-18, and hyperactivation of innate, adaptive, and myeloid compartments than patients with moderate disease. Our analyses provide a comprehensive map of longitudinal immunological responses in COVID-19 patients and integrate key cellular pathways of complex immune networks underpinning severe COVID-19, providing important insights into potential biomarkers and immunotherapies., Competing Interests: The authors declare no competing interests., (© 2021 The Author(s).)

Objectives: As the world transitions into a new era of the COVID-19 pandemic in which vaccines become available, there is an increasing demand for rapid reliable serological testing to identify individuals with levels of immunity considered protective by infection or vaccination., Methods: We used 34 SARS-CoV-2 samples to perform a rapid surrogate virus neutralisation test (sVNT), applicable to many laboratories as it circumvents the need for biosafety level-3 containment. We correlated results from the sVNT with five additional commonly used SARS-CoV-2 serology techniques: the microneutralisation test (MNT), in-house ELISAs, commercial Euroimmun- and Wantai-based ELISAs (RBD, spike and nucleoprotein; IgG, IgA and IgM), antigen-binding avidity, and high-throughput multiplex analyses to profile isotype, subclass and Fc effector binding potential. We correlated antibody levels with antibody-secreting cell (ASC) and circulatory T follicular helper (cTfh) cell numbers., Results: Antibody data obtained with commercial ELISAs closely reflected results using in-house ELISAs against RBD and spike. A correlation matrix across ten measured ELISA parameters revealed positive correlations for all factors. The frequency of inhibition by rapid sVNT strongly correlated with spike-specific IgG and IgA titres detected by both commercial and in-house ELISAs, and MNT titres. Multiplex analyses revealed strongest correlations between IgG, IgG1, FcR and C1q specific to spike and RBD. Acute cTfh-type 1 cell numbers correlated with spike and RBD-specific IgG antibodies measured by ELISAs and sVNT., Conclusion: Our comprehensive analyses provide important insights into SARS-CoV-2 humoral immunity across distinct serology assays and their applicability for specific research and/or diagnostic questions to assess SARS-CoV-2-specific humoral responses., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

An improved understanding of human T cell-mediated immunity in COVID-19 is important for optimizing therapeutic and vaccine strategies. Experience with influenza shows that infection primes CD8 + T cell memory to peptides presented by common HLA types like HLA-A2, which enhances recovery and diminishes clinical severity upon reinfection. Stimulating peripheral blood mononuclear cells from COVID-19 convalescent patients with overlapping peptides from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) led to the clonal expansion of SARS-CoV-2-specific CD8 + and CD4 + T cells in vitro, with CD4 + T cells being robust. We identified two HLA-A*02:01-restricted SARS-CoV-2-specfic CD8 + T cell epitopes, A2/S 269-277 and A2/Orf1ab 3183-3191 Using peptide-HLA tetramer enrichment, direct ex vivo assessment of A2/S 269 + CD8 + and A2/Orf1ab 3183 + CD8 + populations indicated that A2/S 269 + CD8 + T cells were detected at comparable frequencies (∼1.3 × 10 -5 ) in acute and convalescent HLA-A*02:01 + patients. These frequencies were higher than those found in uninfected HLA-A*02:01 + donors (∼2.5 × 10 -6 ), but low when compared to frequencies for influenza-specific (A2/M1 58 ) and Epstein-Barr virus (EBV)-specific (A2/BMLF 1280 ) (∼1.38 × 10 -4 ) populations. Phenotyping A2/S 269 + CD8 + T cells from COVID-19 convalescents ex vivo showed that A2/S 269 + CD8 + T cells were predominantly negative for CD38, HLA-DR, PD-1, and CD71 activation markers, although the majority of total CD8 + T cells expressed granzymes and/or perforin. Furthermore, the bias toward naïve, stem cell memory and central memory A2/S 269 + CD8 + T cells rather than effector memory populations suggests that SARS-CoV-2 infection may be compromising CD8 + T cell activation. Priming with appropriate vaccines may thus be beneficial for optimizing CD8 + T cell immunity in COVID-19., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

Seasonal influenza virus infections cause 290,000-650,000 deaths annually and severe morbidity in 3-5 million people. CD8+ T-cell responses towards virus-derived peptide/human leukocyte antigen (HLA) complexes provide the broadest cross-reactive immunity against human influenza viruses. Several universally-conserved CD8+ T-cell specificities that elicit prominent responses against human influenza A viruses (IAVs) have been identified. These include HLA-A*02:01-M158-66 (A2/M158), HLA-A*03:01-NP265-273, HLA-B*08:01-NP225-233, HLA-B*18:01-NP219-226, HLA-B*27:05-NP383-391 and HLA-B*57:01-NP199-207. The immunodominance hierarchies across these universal CD8+ T-cell epitopes were however unknown. Here, we probed immunodominance status of influenza-specific universal CD8+ T-cells in HLA-I heterozygote individuals expressing two or more universal HLAs for IAV. We found that while CD8+ T-cell responses directed towards A2/M158 were generally immunodominant, A2/M158+CD8+ T-cells were markedly diminished (subdominant) in HLA-A*02:01/B*27:05-expressing donors following ex vivo and in vitro analyses. A2/M158+CD8+ T-cells in non-HLA-B*27:05 individuals were immunodominant, contained optimal public TRBV19/TRAV27 TCRαβ clonotypes and displayed highly polyfunctional and proliferative capacity, while A2/M158+CD8+ T cells in HLA-B*27:05-expressing donors were subdominant, with largely distinct TCRαβ clonotypes and consequently markedly reduced avidity, proliferative and polyfunctional efficacy. Our data illustrate altered immunodominance patterns and immunodomination within human influenza-specific CD8+ T-cells. Accordingly, our work highlights the importance of understanding immunodominance hierarchies within individual donors across a spectrum of prominent virus-specific CD8+ T-cell specificities prior to designing T cell-directed vaccines and immunotherapies, for influenza and other infectious diseases., Competing Interests: The authors have declared that no competing interests exist.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.