Tissue-resident immunity mediates host defense against pathogens and enables rapid adaptive memory responses. However, the study of tissue-resident immunity is hindered by a singular lack of experimental systems allowing pathogenic epithelial infection amidst the full spectrum of endogenous immune subsets. Particularly in lung, differing notions of transient versus sustained residency of tissue-resident memory T cells (TRM) have questioned the extent to which recall immunity to respiratory pathogens occurs locally or in concert with secondary lymphoid organs. We thus generated long-term adult human distal lung organoids from intact tissue fragments in 3D air-liquid interface (ALI) culture that co-preserved epithelial and stromal architecture alongside endogenous lung-resident immune cells (T, B, NK, myeloid). The organoid T cells exhibited persistent cytokine-assisted maintenance, expressed residency and memory markers, and preserved T cell receptor (TCR) repertoires of cognate fresh tissue. SARS-CoV-2 vigorously infected the organoid lung epithelium, stimulated inflammatory cytokine production, and crucially, induced widespread SARS-CoV-2-specific, tissue-resident T cell responses. Our studies introduce a robust adult human lung organoid experimental system containing a physiologic air interface and diverse resident immune subsets, demonstrate the organ-autonomous sufficiency of lung pathogen memory T cell responses, distinct from secondary lymphoid tissue, and provide a platform to investigate tissue-resident immunity in health and disease.

Influenza virus cross-subtype antibodies targeting epitopes in the hemagglutinin (HA) head are rare because these epitopes are variable between influenza virus subtypes. We found that a large proportion of monoclonal antibodies (mAbs) isolated from individuals immunized with the 2021-22 seasonal influenza vaccine bound to an epitope on the HA head of both the H1N1 vaccine strain and H3N2 strains from the mid-1990s. The unmutated common ancestors of many of these mAbs reacted to both the 1990s H3s and the 2021-22 H1 vaccine strain. These cross-subtype antibodies were also found in polyclonal sera, but only among individuals born in the 1990s. Ferrets sequentially exposed to a 1990s H3N2 virus and contemporary influenza vaccine also produced H1/H3 cross-reactive antibodies. Recently, H1N1 viruses have acquired a substitution that abrogates the binding of these antibodies. Together, our study demonstrates how prior influenza virus exposures can influence the specificity of antibodies elicited by entirely different influenza virus subtypes.

Abstract Introduction Post Acute Sequelae of COVID-19 (PASC), also called Long COVID, is an infection-associated chronic syndrome. Despite proposed viral persistence mechanisms, no therapeutic benefit was observed in randomized placebo-controlled trials of nirmatrelvir/ritonavir (NMV/r) in adults with Long COVID, including the Selective Trial of Paxlovid for PASC (STOP-PASC). This systems immunology analysis aimed to characterize immune profiles of participants during clinical trial intervention, identify biomarkers associated with patient-reported outcomes, and investigate potential mechanisms underlying Long COVID. Methods We performed comprehensive immunological profiling of 152 STOP-PASC trial participants using plasma proteomics (Olink® Explore HT 5400 panel), autoantigen arrays, viral serology, and microclot assays at baseline, day 15, and week 10. We assessed associations between immune features and patient-reported outcomes. We also conducted meta-analysis of nine independent Long COVID proteomics cohorts (n = 590 total samples) to identify conserved inflammatory signatures. Results NMV/r treatment at day 15 compared with baseline induced transient changes in plasma proteins that normalized by week 10, primarily impacting myeloid cell/monocyte, lysosome, and complement activation pathways. Cardiovascular symptoms were negatively associated with SARS-CoV-2 antibody levels at baseline. No widespread differences in autoantibody profiles, Epstein-Barr virus (EBV) reactivation, or microclotting were observed between STOP-PASC Long COVID participants, pre-pandemic controls, and individuals without Long COVID. Meta-analysis of publicly available Olink® data from Long COVID cohorts identified a conserved 60-protein Long COVID Signature (LCS) score revealing multi-compartment immune activation involving monocyte, neutrophil, and T/NK cell modules. Conclusion These findings advance our understanding of Long COVID immunology and may help direct future proteomic biomarker endpoints for Long COVID clinical trials. Funding Source Pfizer Topic Categories Computational and Systems Immunology (COMP)

Loss of immune tolerance to the gut microbiome plays a pathogenic role in inflammatory bowel disease (IBD). How dietary factors alter host immune-gut microbiome interactions in IBD is unclear. Here, we apply multi-omics (immunoglobulin A or G and 16S rRNA sequencing [IgA-seq, IgG-seq], blood single-cell RNA sequencing [scRNA-seq], and immune repertoire sequencing) to investigate the effects of 12 weeks of vitamin D on host immune microbe interactions in patients with IBD. Vitamin D treatment associates with decreased disease activity and inflammatory markers and increased IgA-bound and decreased IgG-bound gut microbiota. Vitamin D alters the profiles of IgA-bound (increased Lachnospiraceae, Blautia) and IgG-bound (decreased Proteobacteria, Enterococcaceae) gut bacteria. Vitamin D increases B cell activating factor (BAFF) signaling between plasmacytoid dendritic cells and B cells, alters BCR and TCR clonotypes that associate with Ig-bound gut microbiota, and increases α4β7+ B and T regulatory cells. Our results demonstrate that vitamin D promotes immune tolerance to gut microbiota in patients with IBD. Clinical trial is registered under NCT04828031.

mRNA vaccination for SARS-CoV-2 (CoV-2) results in initial polyclonal antibodies of greater breadth compared to those stimulated by viral infection. Cellular, immunogenetic and antigenic factors leading to human antibody responses with broad viral variant recognition are poorly defined. Existing databases of CoV-2 binding antibodies have limited data about patient and B cell subset origins of the antibodies and their antigen variant binding. We used highly multiplexed panels of DNA-tagged CoV-2 antigens including Spike receptor binding domains from up to 20 viral variants to label and sort 6,262 antigen-binding B cells from peripheral blood of mRNA vaccinees, infected patients and the spleen and lymph nodes of deceased organ donors. Single-cell transcriptome and antigen DNA-tag data showed antigen-specific B cells enriched in a circulating class-switched memory subset with evidence of recent germinal center exposure, and in CD11c+ atypical B cells. Surprisingly, mRNA vaccination preferentially stimulates a subset of B cell receptor (BCR)-defined clonotypes, resulting in greater initial antigen binding breadth. Spleens show greater variant binding breadth than blood B cells from the initial months post-vaccination or infection. Together, these results systematically define the influence of CoV-2 mRNA vaccination and infection on particular B cell receptors and clonotypes, a topic of increasing importance as mRNA vaccination is evaluated for other pathogens. Supported by NIH/NIAID R01AI127877, NIH/NIAID R01AI130398, NIH 1U54CA260517, David Crown Foundation endowment/COVID-19 gift funds, NIH HIPC U19AI090023, U19AI057266, Sean N Parker Foundation/Sunshine Foundation, Early Postdoc.Mobility Fellowship Stipend (SNSF), Fulbright Fellowship, NHMRC Investigator grant, NSFC32270937/NSFC82341068 (Chinese NSF), Coulter COVID-19 Rapid Response Award, MSD kits. Viral Immunology (VIR)

Mouse lemurs (Microcebus spp.) are an emerging primate model organism, but their genetics, cellular and molecular biology remain largely unexplored. In an accompanying paper1, we performed large-scale single-cell RNA sequencing of 27 organs from mouse lemurs. We identified more than 750 molecular cell types, characterized their transcriptomic profiles and provided insight into primate evolution of cell types. Here we use the generated atlas to characterize mouse lemur genes, physiology, disease and mutations. We uncover thousands of previously unidentified lemur genes and hundreds of thousands of new splice junctions including over 85,000 primate splice junctions missing in mice. We systematically explore the lemur immune system by comparing global expression profiles of key immune genes in health and disease, and by mapping immune cell development, trafficking and activation. We characterize primate-specific and lemur-specific physiology and disease, including molecular features of the immune program, lemur adipocytes and metastatic endometrial cancer that resembles the human malignancy. We present expression patterns of more than 400 primate genes missing in mice, many with similar expression patterns to humans and some implicated in human disease. Finally, we provide an experimental framework for reverse genetic analysis by identifying naturally occurring nonsense mutations in three primate immune genes missing in mice and by analysing their transcriptional phenotypes. This work establishes a foundation for molecular and genetic analyses of mouse lemurs and prioritizes primate genes, isoforms, physiology and disease for future study.

The gut microbiome plays a crucial role in modulating human immunity. Previously, we reported that antibiotic-induced microbiome perturbation affects influenza vaccine responses, depending on pre-existing immunity levels. Here, we employed a systems biology approach to analyze the impact of antibiotic administration on both primary and secondary immune responses to the rabies vaccine in humans. Antibiotic administration reduced the gut bacterial load, with a long-lasting reduction in commensal diversity. This alteration was associated with reduced rabies-specific humoral responses. Multi-omics profiling revealed that antibiotic administration induced (1) an enhanced pro-inflammatory signature early after vaccination, (2) a shift in the balance of vaccine-specific T-helper 1 (Th1) to T-follicular-helper response toward Th1 phenotype, and (3) profound alterations in metabolites, particularly in secondary bile acids in the blood. By integrating multi-omics datasets, we generated a multiscale, multi-response network that revealed key regulatory nodes, including the microbiota, secondary bile acids, and humoral immunity to vaccination.

Understanding T-Cell receptor (TCR) and epitope interactions is critical for advancing our knowledge of the human immune system. Traditional approaches that use sequence similarity or structure data often struggle to scale and generalize across diverse TCR/epitope interactions. To address these limitations, we introduce ImmuneCLIP, a contrastive fine-tuning method that leverages pre-trained protein language models to align TCR and epitope embeddings in a shared latent space. ImmuneCLIP is evaluated on epitope ranking and binding prediction tasks, where it consistently outperforms sequence-similarity based methods and existing deep learning models. Furthermore, ImmuneCLIP shows strong generalization capabilities even with limited training data, highlighting its potential for studying diverse immune interactions and uncovering patterns that improve our understanding of human immune recognition systems.

Bats are significant reservoir hosts of viruses, yet their antibody-mediated immunity, a key factor in shaping viral evolution and immune evasion, remains understudied. Unlike all other known mammals that possess a single immunoglobulin heavy chain (IgH) locus, we have identified dual, complete, and functional IgH loci on separate chromosomes in eleven bat species. This immunogenetic architecture is reminiscent of more limited duplicated loci in teleost fish but is novel among mammals. Using single-cell transcriptomic data from Eptesicus fuscus (big brown bats), we confirm functional rearrangement and expression of both IgH loci. These loci exhibit distinct mechanisms for generating antibody diversity and function, including biased usage favoring the smaller, more compact locus, and differential selection in antigen-experienced B cells and plasma cells. These findings reveal a unique adaptation in mammalian humoral immunity, offering new insights into the antibody responses in bats, the functional specialization of their humoral immunity and its potential role in resistance to viral pathogenesis. Supported by NSF IOS 2032157; NSF BII 2021909; NSF BII 2213854; NIH T32OD011121; NIH 5 T32 AI07290; NIH NIAID 5 R21 AI169548; LSRF; Open Phil; Stanford Woods Institute for the Environment EVP; Stanford CEHG Postdoctoral Fellowship; Stanford School of Medicine Dean’s Postdoctoral Fellowship, funds from the Stanford Pathology Department and an endowment from the Crown Fndn. Veterinary and Comparative Immunology (VET)

Analyzing age-related changes in the B-cell repertoire is critical for understanding declining immune function in the elderly. New naïve B cell are produced in the bone marrow of elderly individuals, but changes in naïve B cell generation with age are poorly characterized. We conducted a longitudinal study of 74 healthy individuals from different age groups,with annual blood sampling for up to 10 years. Immunoglobulin heavy chain libraries prepared from peripheral blood B cells were characterized by high throughput DNA sequencing. We observed a non-linear age-associated decline in the percentage of naive B cells with major changes between 60 and 100 y.o. Younger individuals show more public naive B cell clones compared to the elderly, as well as more similar V gene usage patterns, suggesting increasing divergence of naïve BCR generation among elderly. Over time, V-gene usage in non-naive B-cell repertoires also diverged, particularly in IgG and IgM, potentially driven by the expansion of B-cell clones. Expanded B-cell clones detected longitudinally include those continuing to expand in successive years and showing increasing somatic hypermutation (SHM), in contrast to other large clones that persist without increasing SHM. These data highlight features that could contribute to immunological impairment in the elderly, including increased variation in naïve BCR repertoire, and occupancy of the B cell repertoire by large antigen-experienced clones. Supported by NIAID/NIH grants U19AI090019, U19AI057229, R01AI130398, R01AI127877 Computational and Systems Immunology (COMP)

Peptide macrocycles are promising therapeutics for a variety of disease indications due to their overall metabolic stability and potential to make highly selective binding interactions with targets. Recent advances in covalent macrocycle peptide discovery, driven by phage and mRNA display methods, have enabled the rapid identification of highly potent and selective molecules from large libraires of diverse macrocycles. However, there are currently limited examples of macrocycles that can be used to disrupt protein-protein interactions and even fewer examples that function by formation of a covalent bond to a target protein. In this work, we describe a directed counter-selection method that enables identification of covalent macrocyclic ligands targeting a protein-protein interaction using a phage display screening platform. This method utilizes binary and ternary screenings of a chemically modified phage display library, employing the stable and weakly reactive aryl fluorosulfate electrophile. We demonstrate the utility of this approach using the SARS-CoV-2 Spike-ACE2 protein-protein interaction and identify multiple covalent macrocyclic inhibitors that disrupt this interaction. The resulting compounds displayed antiviral activity against live virus that was irreversible after washout due to the covalent binding mechanism. These results highlight the potential of this screening platform for developing covalent macrocyclic drugs that disrupt protein-protein interactions with long lasting effects.

Clinical diagnosis typically incorporates physical examination, patient history, various laboratory tests, and imaging studies but makes limited use of the human immune system's own record of antigen exposures encoded by receptors on B cells and T cells. We analyzed immune receptor datasets from 593 individuals to develop MAchine Learning for Immunological Diagnosis, an interpretive framework to screen for multiple illnesses simultaneously or precisely test for one condition. This approach detects specific infections, autoimmune disorders, vaccine responses, and disease severity differences. Human-interpretable features of the model recapitulate known immune responses to severe acute respiratory syndrome coronavirus 2, influenza, and human immunodeficiency virus, highlight antigen-specific receptors, and reveal distinct characteristics of systemic lupus erythematosus and type-1 diabetes autoreactivity. This analysis framework has broad potential for scientific and clinical interpretation of immune responses.

B cells have important functions in gut homeostasis, and dysregulated B cell populations are frequently observed in patients with inflammatory bowel diseases, including both ulcerative colitis (UC) and Crohn's disease (CD). How these B cell perturbations contribute to disease remains largely unknown. Here, we perform deep sequencing of the B cell receptor (BCR) repertoire in four cohorts of patients with CD, together with healthy controls and patients with UC. We identify BCR clones that are shared between patients with CD but not found in healthy individuals nor in patients with UC, indicating CD-associated B cell immune responses. Shared clones are present in the inflamed gut mucosa, draining intestinal lymph nodes and blood, suggesting the presence of common CD-associated antigens that drive B cell responses in CD patients.

In serology, each sample is typically tested individually, one antigen at a time. This is costly and time consuming. Serology techniques should ideally allow recurrent measurements in parallel in small sample volumes and be inexpensive and fast. Here we show that mass cytometry can be used to scale up multiplexed serology testing by leveraging polystyrene beads uniformly loaded with combinations of stable isotopes. We generated 18,480 unique isotopically barcoded beads to simultaneously detect, in a single tube with 924 serum samples, the levels of immunoglobulins G and M against 19 proteins from SARS-CoV-2 (a total of 36,960 tests in 400 nl of sample volume and 30 μl of reaction volume). As a rapid, high-throughput and cost-effective technique, serology by mass cytometry may contribute to the effective management of public health emergencies originating from infectious diseases.

Infections with SARS-CoV-2 and the development of immunity to the virus and its antigenic variants have been unevenly documented globally, with African populations particularly understudied. As SARS-CoV-2 transitions toward being an endemic pathogen, a more nuanced understanding of immune protection in diverse populations is required. In 2023, we conducted a cross-sectional study of 1,000 Ghanaian residents to assess SARS-CoV-2 prevalence and antibody correlates of immunity against SARS-CoV-2 variants. We found an active SARS-CoV-2 infection rate of 1.3% and a 57% vaccination rate. We observed anti-SARS-CoV-2 Spike plasma antibody sero-positivity of 98.7%, with urban compared to rural residents having higher anti-SARS-CoV-2 plasma and saliva antibody concentrations. Vaccinated and urban individuals exhibited significantly greater Spike-pseudotyped virus neutralization than nonvaccinated and rural individuals. Notably, plasma antibodies preferentially bound Wuhan-Hu-1 over Omicron Spike variants. Our findings indicate significant prior and ongoing SARS-CoV-2 transmission as well as immunological imprinting by Wuhan-Hu-1-like SARS-CoV-2 in Ghana.

Food Protein-Induced Enterocolitis (FPIES) is a non-IgE mediated GI food allergy characterized by delayed, protracted vomiting, accompanied by lethargy and pallor, usually 1-4 hours following ingestion of the food allergen. The pathophysiology of FPIES remains unknown and currently there are no diagnostic biomarkers available to assess disease activity or its resolution. Over the last two decades, FPIES has become increasingly recognized in both pediatric and adult patients. Forty years later after the initial FPIES description, the first international classification of diseases (ICD-10) code for FPIES was established and the first international consensus guidelines for diagnosis and management of FPIES was published.On June 22, 2022, the National Institute of Allergy and Infectious Diseases (NIAID) held its first virtual multidisciplinary workshop on FPIES. Various clinical and translational aspects of FPIES, as well as the important areas of unmet needs were discussed as priorities for future research during this 2-day virtual workshop. The following report provides a summary of content of the workshop, including updated literature on the topic areas, as well as providing a critical commentary on the state of FPIES.

Many questions remain about the prevalence and effects of SARS-CoV-2 infection in malaria-endemic African countries like Uganda, particularly in vulnerable groups such as pregnant women. We describe SARS-CoV-2 immunoglobulin (Ig)G and IgM antibody responses and clinical outcomes in mother-infant dyads enrolled in malaria chemoprevention trials in Uganda. From December 2020-February 2022, among 400 unvaccinated pregnant women enrolled at 12-20 weeks gestation and followed through delivery, 128 (32%) were seronegative for anti-SARS-CoV-2 IgG and IgM at enrollment and delivery, 80 (20%) were infected prior to or early in pregnancy, and 192 (48%) were infected or re-infected with SARS-CoV-2 during pregnancy. We observed preferential binding of plasma IgG to WuhanHu-1-like antigens in individuals seroconverting up to early 2021, and to Delta variant antigens in a subset of individuals in mid-2021. Breadth of IgG binding to all variants improved over time, consistent with affinity maturation of the antibody response in the cohort. No women experienced severe respiratory illness during the study. SARS-CoV-2 infection in early pregnancy was associated with lower median length-for-age Z-score at age 3 months compared with no infection or late pregnancy infect (-1.54 versus -0.37 and -0.51, P 5 0.009). These findings suggest that pregnant Ugandan women experienced high levels of SARS-CoV-2 infection without severe respiratory illness. Variant-specific serology testing demonstrated evidence of antibody affinity maturation at the population level. Early gestational SARS-CoV-2 infection was associated with transient shorter stature in early infancy. Further research should explore the significance of this finding and define targeted measures to prevent infection in pregnancy.