Immunology

Background: Short-chain fatty acids (SCFAs) are microbial metabolites with immunoregulatory properties. Human milk contains SCFAs which have been proposed as potential modulators of infant immune development. We aimed to examine associations between human milk SCFA concentrations and infant allergic disease outcomes in a high-risk cohort of infants of atopic mothers. Methods: SCFAs were measured by targeted liquid chromatography-mass spectrometry in human milk samples collected at 3 and 6 months postpartum from atopic mothers enrolled in the Infant Fish Oil Supplementation (IFOS) Study (n=147). Associations between milk SCFA concentrations and early childhood allergic disease outcomes (atopic dermatitis, food allergy, allergic rhinitis, and allergen sensitisation at 1 and 2-3 years) were examined using logistic regression. Results: Human milk SCFA concentrations were broadly stable between 3 and 6 months postpartum, except for acetate which was significantly elevated at 6 months. No significant associations were observed between human milk SCFA concentrations and any allergic disease outcome after correction for multiple comparisons (all p>0.05). Conclusions: Human milk SCFA concentrations are not associated with allergic disease outcomes up to 4 years of age. These findings suggest that oral SCFA exposure via human milk is insufficient to reduce infant allergy risk, and that gut SCFA production may be a more relevant target for future allergy prevention research.

Monocytes are critical regulators of allergic inflammation, whose functions are modified by IgE-driven processes. Monocytes are heterogeneous; comprised of multiple subsets which implies differential functions. In allergic inflammation, this heterogeneity is likely influenced by IgE-mediated effects. We sought to identify phenotypically distinct monocyte subsets related to allergic disease and then further delineate functional differences in cytokine release and antiviral responses. Using high dimensional spectral flow cytometry, we identified monocyte surface phenotypes directly related to surface levels of the high affinity IgE receptor (Fc{epsilon}RI) and surface-bound IgE. Fc{epsilon}RI+IgE+ monocytes, or FIMs, correlated with allergic disease and the level of atopy (i.e. serum IgE levels) of individual subjects. The FIM population also had differential surface expression of other molecules of monocyte maturation, which closely resembled a type 2 conventional dendritic cell (cDC2) phenotype. Functionally, FIMs had enhanced antiviral responses and IgE-driven IL-10 cytokine release. Finally, we showed that FIMs could be identified at higher levels in lung tissue from individuals with asthma. This study supports that atopic disease drives differential monocyte phenotypes, with the FIM population, specifically, as a more mature cell population closely related to dendritic cells with enhanced antiviral responses. The presence of monocytes in lung tissue during lethal asthma exacerbation further supports a role in regulating tissue inflammatory responses in allergic airway disease.

Cross-reactive antibodies against dengue virus are known to cause antibody-dependent enhancement (ADE) of infection or disease severity under specific conditions. In our previous study, we showed that primary immunization with the COVID-19 vaccine induces induces cross-reactive IgG causing ADE against dengue. In the present study, we investigated the influence of IgG Fc-glycosylation (analyzed by LC-MS/MS) on ADE mediated by cross-reactive IgG against dengue from IgG against SARS-CoV-2. We found a clear correlation between anti-DENV2 E IgG2 galactosylation and the ADE capacity of cross-reactive IgG against dengue in individuals vaccinated against COVID-19. IgG2 sialylation increased over time; however, it was not correlated with ADE capacity. This phenomenon was restricted to IgG2, whereas anti-DENV2 E IgG1 Fc-glycosylation remained stable after COVID-19 vaccination.

Background Growing evidence suggests that the gut microbiome influences nasal and ocular allergic inflammation through gut-mucosal immune interactions. Yet, its association with Allergic rhinitis (AR) and allergic eye symptoms (AES) remains incompletely understood in large population-based cohorts. Objective To examine associations between the gut microbiome and self-reported AR and AES in Finnish adults. Methods Shallow metagenomic sequencing was performed on stool samples from a population-based cohort (FINRISK02; n = 7,231). Microbial taxonomic and functional profiles were compared between individuals with AR (n = 1,950), AES (n = 1,554), combined allergies (AR and/or AES; n = 2,305), and controls without reported symptoms (n = 3,175). Results Allergic groups exhibited lower microbial richness and phylogenetic diversity than controls. Shared microbial and functional signatures were observed across AR and AES, consistent with their high co-occurrence (N = 1,199). Compared with controls, allergic groups showed enrichment of 17 bacterial species, predominantly from the Clostridia class, including taxa previously associated with asthma, chronic obstructive pulmonary disease, and atopic dermatitis. Allergic individuals also exhibited enrichment of pathways related to mucosal carbohydrate processing, shikimate metabolism, histidine turnover, and broader amino acid metabolism. Concurrent enrichment of histidine biosynthesis and degradation suggested altered microbial histidine metabolism. Conclusions Adult allergic symptoms are associated with gut microbiome taxonomic and functional alterations linked to mucosal barrier function and immune-related metabolism, supporting a shared gut-mucosal immune axis across allergic phenotypes.

Dimeric immunoglobulin A (dIgA) is generated from IgA monomers (mIgA) via JCHAIN-dependent polymerization. DIgA is transported across epithelial barriers by the poly Ig receptor (PIGR) and confers mucosal protection, while serum contains substantial amounts of IgA monomers. Distinct plasma cell subsets have been proposed to produce either monomeric or dimeric IgA, with bone marrow plasma cells as a primary source of mIgA. Here, we addressed whether IgA plasma cell populations segregate based on mIgA or dIgA production. Flow cytometric analysis of antibody-secreting cells from bone marrow, lymphoid and mucosal tissues revealed universal intracellular JCHAIN expression across isotypes and failed to identify a discrete JCHAIN-negative IgA plasma cell population. To detect polymeric IgA, we generated a recombinant soluble PIGR that selectively bound JCHAIN-containing dIgA in Western blot, ELISA, and flow cytometry. Soluble PIGR binding was detected in all IgA plasma cells irrespective of tissue origin, arguing against a dedicated mIgA-producing plasma cell subset incapable of dIgA formation. Ex vivo cultures and single-cell DropMap secretion assays demonstrated that bone marrow and lamina propria IgA antibody-secreting cells co-secrete mIgA and dIgA. These findings suggest that dIgA assembly and secretion are general properties of IgA plasma cells and disfavor a dedicated mIgA-producing population.

Summary Background Severe dengue reflects a temporally regulated interaction between viral burden, NS1 antigenaemia, cytokine and chemokine amplification, endothelial activation, glycocalyx injury, and organ stress. Although individual cytokines, endothelial markers, viral-burden measures, and clinical markers have been widely studied, the integrated pathogen-host evidence base remains fragmented. We synthesised evidence for cytokine, endothelial, and viral-burden signatures associated with severe dengue and assessed whether paired pathogen-host measurement provides a biologically coherent framework for severity assessment. Methods We searched MEDLINE, Embase, Scopus, Web of Science, Cochrane Library, Global Health, WHO Global Index Medicus, and medRxiv from database inception to 30 April 2026, without language restriction, for studies reporting viral burden, NS1 antigenaemia, cytokine, chemokine, endothelial, glycocalyx, inflammatory, or routine host-response markers in laboratory-confirmed dengue with severity outcomes. Eligible designs were prognostic-factor association studies, cross-sectional biomarker studies, and multivariable prediction-model studies. Risk of bias was assessed using QUIPS for prognostic-factor studies, PROBAST for prediction-model studies, and the relevant JBI critical appraisal checklist for cross-sectional biomarker studies, with the Newcastle-Ottawa Scale used selectively for cohort or case-control designs not amenable to QUIPS. Random-effects meta-analysis pooled standardised mean differences using restricted maximum likelihood with Hartung-Knapp adjustment. The protocol was registered with PROSPERO (CRD420261396923) before final extraction and synthesis. Findings Of 4,180 records identified, 79 studies including 47,612 participants met eligibility criteria. Forty-nine studies evaluated paired pathogen-host markers, 14 evaluated viral burden or NS1 antigenaemia alone, nine evaluated host biomarkers alone, and seven reported multivariable prediction models. Pathogen-side markers showed modest pooled severity associations whose magnitude depended on day of illness, immune status, and infecting serotype. Cytokine and chemokine markers, particularly IL-10, IL-6, IL-8, and CXCL10/IP-10, showed larger pooled effects favouring severe disease, while endothelial and glycocalyx markers, including angiopoietin-2 and syndecan-1, provided the most direct mechanistic link to plasma leakage. Routine clinical markers, especially platelet count, AST, ferritin, ALT, and lactate, retained substantial discriminatory value. Prediction models reported areas under the curve of up to 0{middle dot}96 in internal validation and 0{middle dot}97 in discovery analyses, but three had been externally validated, calibration was reported in two, and decision-curve analysis in none. Interpretation Current evidence supports severe dengue as an integrated pathogen-host injury syndrome in which viral burden and NS1 antigenaemia interact with cytokine amplification, endothelial dysfunction, glycocalyx injury, and routine markers of organ stress. The strongest translational direction is not a single biomarker but a parsimonious cytokine-endothelial-pathogen panel requiring prospective external validation across age groups, serotypes, immune-status strata, and endemic regions. Existing evidence supports candidate marker prioritisation and mechanistic synthesis, but not immediate routine clinical deployment.

Recent epidemiologic studies indicate that adult-onset type 1 diabetes (AOT1D) is more common than childhood-onset type 1 diabetes, yet it remains clinically underrecognized. Because little is known about the emergence of islet autoantibodies in AOT1D, we conducted a retrospective study using electronic medical records from the United States Military Health System and longitudinal serum samples from 169 individuals with AOT1D and 40 healthy controls obtained from the Department of Defense Serum Repository. Among 643 prediagnostic samples from individuals with AOT1D, IA-2 autoantibodies were the most prevalent (50%), followed by GADA (46%), IA-2{beta} (34%), ZnT8-R (27%), and ZnT8-W (15%). Overall, 85% (144/169) of subjects were seropositive for at least one autoantibody prior to diagnosis. Analysis of the earliest available sample from all of the AOT1D cases, grouped into 5-year intervals preceding diagnosis, demonstrated a progressive increase in seropositivity over time: 38% of subjects were seropositive more than 20 years before diagnosis, increasing to 44% at 20-15 years, 59% at 15-10 years, 73% at 10-5 years, and 91% within 5 years of diagnosis. Among the 144 seropositive individuals, positivity for two or more autoantibodies was the most common pattern, occurring in 50% (72/144) of cases. Isolated GADA positivity (22%) and isolated IA-2/IA-2{beta} positivity (24%) occurred at similar frequencies, whereas isolated ZnT8 positivity was uncommon (4%). Temporal analysis showed that isolated GADA positivity appeared earliest, with a median onset of 7.9 years before diagnosis, whereas multiple-autoantibody positivity, IA-2 positivity, and ZnT8 positivity emerged later, with median onsets of 4.6, 4.5, and 1.9 years before diagnosis, respectively. These findings extend observations from pediatric type 1 diabetes to adults and demonstrate that AOT1D-associated autoimmunity often begins decades before clinical diagnosis, highlighting a potentially important window for risk stratification and preventive intervention.

Autoimmune diseases, such as systemic lupus erythematosus (SLE), are underscored by dysregulated B cell function including the production of autoantibodies, skewed population ratios, and aberrant signaling. Given that the family of nuclear factor kappa B (NF-{kappa}B) transcription factors govern responses to stimuli, survival, differentiation, and so forth understanding the intricate regulatory network of NF-{kappa}B in B cell biology is paramount for unraveling treatments for B cell-linked autoimmune diseases. Here, we focus on a negative regulator of NF-{kappa}B signaling, A20 (TNFAIP3), that deactivates NF-{kappa}B transcription factor translocation through the ubiquitination and deubiquitination of target proteins. Haploinsufficiency in A20 results in an autoimmune phenotype and mutations to A20 have been associated with SLE, suggesting implications to B cell function. To investigate the role of A20 in NF-{kappa}B in human B cells, we generated a TNFAIP3 knockout (KO) Raji cell line. Cells were stimulated with either anti-IgM or Resiquimod (R848) to activate distinct NF-{kappa}B signaling pathways. Using qRT-PCR, western blotting, and flow cytometry, we assessed differences in gene expression, protein production, and NF-{kappa}B activation. We observed key limitations in using Epstein-Barr virus transformed B cell lines to model inducible NF-{kappa}B signaling.

Introduction: Anaemia and micronutrient deficiencies are common in low- and middle-income countries, where vaccine-induced immune responses are often suboptimal. However, whether pre-vaccination nutritional status influences pneumococcal vaccine immunogenicity in young children remains poorly characterised. Methods: We examined associations between pneumococcal vaccine responses in 670 Kenyan children enrolled in three vaccine trials: PRISM (PCV10; n=195; NCT01028326), FPCV (fractional- and full-dose PCV10/PCV13; n=306; NCT03489018), and PATH-wSP (whole-cell pneumococcal vaccine; n=169; NCT02543892) and baseline anaemia (FPCV and PATH-wSP) and micronutrient status (iron, folate, zinc, and vitamins A, B12, D, and E). Analyses were performed separately for each trial. Primary outcomes were post-vaccination serotype- or antigen-specific IgG concentrations, opsonophagocytic activity (OPA) titres, and composite IgG or OPA z scores. Results: Vitamin B12 and haemoglobin concentrations were positively associated with composite and serotype- or antigen-specific antibody responses in analyses controlling for age, sex, malnutrition and inflammation. In the PRISM trial, PCV10-induced IgG (serotypes 1 and 6B) and OPA (serotypes 1, 4, 14, and 23F) responses were positively associated with vitamin B12 concentrations. Moderate anaemia was associated with lower IgG responses to serotypes 9V and 14 following full-dose PCV13 vaccination (FPCV) and lower antigen-specific IgG responses following the 1 mg PATH-wSP vaccine. No consistent associations were observed for ferritin, folate, zinc, or vitamins A, D, and E. Conclusion: Vitamin B12 deficiency and anaemia were associated with reduced pneumococcal vaccine responses in young Kenyan children. Optimising nutritional status before vaccination could be a strategy to improve vaccine responses in populations where anaemia and micronutrient deficiencies are common.

The rapid evolution of avian influenza A/H5N1, including the recent U.S. clade 2.3.4.4b outbreak, highlights its pandemic potential and the urgent need for durable, broadly protective vaccines. Given the capacity of CD8+ T cells to mediate cross-strain immunity, we investigated whether geographically distinct HLA-A33 allotypes, HLA-A*33:01 in East/Southeast Asia and HLA-A*33:03 in South Asia, differentially shape the influenza immunopeptidome and influence antiviral immunity. Antigen-presenting cells overexpressing HLA-A*33:01 or HLA-A*33:03 were transfected with single A/H5N1 antigens or infected with A/X-31 (H3N2) as a control comparison representing current seasonal influenza virus. We identified novel ligands restricted to HLA-A*33:01 (57 from A/H5N1; 55 from A/X-31) and HLA-A*33:03 (29 from A/H5N1; 45 from A/X-31). Although fewer peptides were recovered for HLA-A*33:03, a larger proportion of A/X-31-derived peptides were predicted as high-affinity binders (74%) compared with HLA-A*33:01 (61%), indicating qualitative differences in antigen presentation. To determine immunogenicity, peripheral blood lymphocytes from HLA-A*33:03-positive, A/H5N1-naive donors were stimulated with four conserved peptides: PB2GTF, PB2KTY, NPSVQ and PB1MTK. All elicited robust CD8 T cell activation despite the absence of prior A/H5N1 exposure, demonstrating cross-recognition by memory T cells primed against seasonal influenza. These findings define HLA-A33-restricted influenza epitopes and reveal allotype-specific presentation features that shape CD8+ T cell immunity. Conserved, immunogenic peptides identified here represent promising candidates for rational design of broadly cross-reactive vaccines to protect HLA-A33-expressing populations against severe A/H5N1 disease. Data are available via ProteomeXchange with identifier PXD078870. Author SummaryAvian influenza A/H5N1 continues to pose a significant pandemic threat because of its ability to infect humans and its potential to acquire sustained human-to-human transmissibility. While current influenza vaccines primarily target rapidly evolving viral surface proteins, CD8+ T cells can recognize more conserved internal viral proteins and may provide broader protection against diverse influenza strains. In this study, we investigated how two common HLA-A33 variants, which are prevalent in South, East, and Southeast Asian populations, present influenza-derived peptides to CD8+ T cells. We identified novel influenza peptides presented by HLA-A*33:01 and HLA-A*33:03. Importantly, several conserved A/H5N1-derived peptides were recognized by memory CD8+ T cells from healthy individuals with no prior exposure to A/H5N1, suggesting that previous infection with seasonal influenza viruses can generate cross-reactive immune responses. Our findings expand the current repository of influenza T cell targets and provide new insights into antiviral immunity in HLA-A33-expressing populations. The conserved and immunogenic peptides identified in this study may help guide the development of broadly protective influenza vaccines and contribute to future pandemic preparedness efforts.

Women are predisposed to systemic lupus erythematosus (SLE) with a prevalence ratio of up to 9:1 over men. Multiple mouse strains including NZM2328 exhibit strong female dominance in developing spontaneous lupus as in humans with SLE. While lupus-prone mice can develop disease under germ free (GF) condition, the role of gut microbiota in female bias for lupus nephritis is not investigated systematically. Here, using specific pathogen free (SPF) and GF NZM2328 mice, and employing microbiota-depletion and microbial-association strategies, we show that microbiota influences lupus-like disease outcomes differently in males and females. Female NZM2328 mice with intact microbiota presents higher inflammation factor expression, including X-chromosome linked TLRs, in the distal gut and systemic compartments, and higher activation of genes and biological pathways such as neutrophil extracellular trap (NET) formation and complement and coagulation cascade (CCC) pathways, associating with their higher disease susceptibility. Gut microbiota-depletion as well as GF derivation eliminated not only the modest differences in the serum and fecal antibody levels and nAg reactivity, but also the gender bias in the timing of clinical stage disease onset as well as systemic NET and CCC pathway activation. Reciprocally, conventionalization of GF NZM2328 mice at juvenile age restored the female bias in intestinal and systemic autoantibody levels, pro-inflammatory immune pathway activation, and the timing of clinical stage disease onset. Overall, our observations show that, while genetic susceptibility appears to be the cause of lupus-like disease in NZM2328 mice, differential activation of NET and CCC pathways in males and females upon exposure to gut microbes, in combination with host-factors, causes gender bias in disease outcomes. We conclude that microbiota exposure-dependent protection of males and overactivation of NET and CCC pathways in females could be contributing to the female bias in lupus-like disease in NZM2328 mice.

Abstract Introduction: IL-15 is one of the most promising candidate cytokines in cancer immunotherapy due to its ability to promote the activity of different cytotoxic innate immune cell subsets such as NK, ILC1 and gammadelta T cells. During biosynthesis, IL-15 associates with IL-15alpha and is transported to the cell surface where IL-15Ralpha trans-presents IL-15 to target neighboring cells expressing the beta chain (IL-2Rbeta) and the common gamma chain. Our group previously showed that in autoimmune type 1 diabetes and early innate immune responses to infections trans-presentation by IL-15Ralpha is dispensable. Here we addressed the relative roles of IL-15 and trans-presented IL-15 in the control of established tumors and spontaneous tumor development. Methodology: Growth kinetics of tumor cell lines were monitored in WT, Il15-/- and Il15ra-/- mice. Spontaneous fibrosarcoma was induced with Methylcholanthrene (MCA) in WT, Il15-/- and Il15ra-/- mice. Cell lines were established from MCA-induced tumors to characterize their immunogenicity. Results: Growth of established tumor cell lines were comparable in the three genotypes. MCA-induced tumor incidence was reduced in Il15ra-/- mice when compared to WT and Il15-/- mice. In vitro, MCA tumor-derived cell lines expressed MHC-I and PD-L1 and had comparable proliferation rates. In vivo, MCA tumor-derived cell lines established from the 3 genotypes showed comparative growth in WT mice suggesting that IL-15 does not impact immunoediting. Nonetheless, NLRC5 expressing B16-F10 tumors were contained in WT and Il15ra-/- mice but not in Il15-/- mice. Conclusions: Taken together, these results show that in the absence of trans-presentation by IL-15Ralpha, IL-15 can better control spontaneous tumor development and that IL-15 signaling plays a minor role in immunosurveillance in this model. IL-15 signaling, independent of IL-15Ralpha has a significant role in the control of solid tumors.

Elastin degradation during chronic lung inflammation generates elastin peptides (EPs) with immunomodulatory properties. Because elastin is abundant in the lung, its breakdown in diseases such as chronic obstructive pulmonary disease (COPD) and asthma produces high EPs levels that may influence local immune responses. Here, we investigated the impact of EPs on group 2 innate lymphoid cells (ILC2) using mouse models of EP-induced emphysema and house dust mite (HDM)-induced asthma. EPs instillation reduced lung ILC2 numbers without affecting Th2 cells. In patients with COPD, we observed decreased CCL20 expression in lung immune cells and an inverse correlation between serum CCL20 levels and clinical indicators of elevated EPs burden. We also showed that EPs instillation during HDM-induced lung inflammation directly decreased CCL20 expression. These findings identify EPs as regulators of ILC2 trafficking through CCL20 downregulation, revealing a direct link between extracellular matrix (ECM) degradation and the chemokine networks orchestrating type 2 immunity. One Sentence SummaryElastin-derived peptides reshape type 2 immunity by blocking CCL20-driven ILC2 recruitment during lung inflammation.

SIGLECs remain poorly defined in human B-cell biology beyond SIGLEC-2/CD22 and SIGLEC-10. Here, we identify a previously unrecognized regulatory pathway involving the paired receptors SIGLEC-5 and SIGLEC-14 at the human B-T-cell interface. We show that activated B-cells differentially regulate these receptors: SIGLEC-5 is predominantly surface-expressed and induced by CD40 engagement, whereas SIGLEC-14 is primarily secreted and upregulated after both CD40 and TLR9 stimulation. We further identify EBP (elastin binding protein) and CTSA (cathepsin A) components of the elastin receptor complex (ERC), expressed by activated T-cells, as a novel ligand for both SIGLEC-5 and SIGLEC-14. Functionally, ERC-associated engagement of SIGLEC-5 on B-cells suppresses T-cell IFN-g; and IL-17 expression, establishing SIGLEC-5 as a B-cell-expressed inhibitory SIGLEC that restrains inflammatory T-cell cytokine responses. SIGLEC-14 does not alter this suppression, as SIGLEC-5+ B-cells from SIGLEC-14-sufficient and -null individuals show comparable inhibitory activity. These findings broaden SIGLEC-mediated adaptive immune regulation, with relevance to inflammatory and autoimmune disease.

IntroductionIntestinal barrier failure is a key characteristic of both kinds of inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohns disease (CD). The intestinal barrier, or gut mucosal barrier, is composed of mucus and a tightly interconnected single layer of intestinal epithelial cells (IEC) that line the gut. Together, these components work to contain the gut microbiota within the gut lumen and when they fail, microbes, microbial products, or microbial components cause damage, inflammation, and immune activation in host tissue. We previously reported that High mobility group box 1 (HMGB1) in colonic mucus aggregates bacteria, limits bacterial invasion through mucus, and prevents bacteria from adhering to host tissue. Epithelial surface-associated HMGB1 is decreased in active UC lesions and low levels of HMGB1 are associated with high levels of tissue-adherent bacteria expressing adhesins carrying the molecular target of HMGB1 (ToH1). The study reported here was designed to determine whether HMGB1 defense is also compromised in active lesions from CD patients. MethodsImmunofluorescence microscopy was used to visualize mucus and HMGB1 in tissue from colonic resections performed in CD and non-IBD control patients. ResultsActive CD lesions had areas where the IEC were absent or pulling away from underlying tissue along with areas of increased mucus thickness and goblet cells full of mucus highly positive for alpha-linked-fucose residues. The surface associated HMGB1 was also decreased in active CD lesions. ConclusionTissue from CD patients exhibited cellular and acellular intestinal barrier defects in comparison to control patients. We observed the previously reported loss of IEC barrier integrity and abnormalities in the amount and distribution of mucus in CD lesions. We also report for the first time that CD is associated with decreased HMGB1 defense at the colon surface.

Fc receptor-like protein 5 (FCRL5) is a low-affinity IgG receptor expressed on B cells, with emerging therapeutic relevance due to its expression on multiple myeloma cells, and a potential role in regulating B cell responses. Previous reports on the FCRL5-IgG interaction vary widely in reported affinities, binding differences across IgG subclasses, and molecular requirements for maximal binding. Furthermore, the impact of Fc-engineering strategies, as used in (therapeutic) monoclonal antibodies, remains poorly understood. Here, we provide a comprehensive biochemical analysis of the FCRL5-IgG interaction. We demonstrate that FCRL5 is a true IgG Fc-receptor, binding with very low affinity (60-80 M). FCRL5 binds IgG in a manner involving primarily the two N-terminal domains of FCRL5, and the third domain for maximal binding, but with distinct essential residues in the IgG Fc-tail. Surface plasmon resonance analysis of the binding of FCRL5 to the various IgG subclasses revealed a preference for IgG1 and IgG4. Interestingly, various Fc-engineered IgG variants commonly used for silencing or enhancing of Fc receptor binding do not impact FCRL5 binding. Screening the binding of a set of IgG antibodies carrying defined sets of Fc-mutations to FCRL5 revealed E293 as a key binding determinant and led to the discovery of E293R as a mutation that selectively abrogates FCRL5 binding while preserving binding to other classical Fc{gamma}Rs. Lastly, we show that FCRL5 has considerable preference for binding afucosylated IgG. Together, our results define the essential characteristics of the IgG-FCRL5 interaction and demonstrate the potential of both naturally occurring IgG variants as well as therapeutically explored bioengineered IgG formats to differentially engage FCRL5.

We previously reported inherited RORgammaT deficiency in seven patients from three ancestries (Chilean, Palestinian, Saudi Arabian) with mycobacterial disease and chronic mucocutaneous candidiasis (CMC). We report here five additional patients from different ancestries (Afghan, Indian, Iranian, Japanese, Sri Lankan), each homozygous for a new loss-of-function RORC variant. All but one patient, the exception receiving early prophylaxis, developed mycobacterial disease due to a near-complete depletion of innate-like adaptive T cells, including MAIT and iNKT cells, low counts of adaptive TH1* and CD8+ T cells, and impaired Mycobacterium-induced IFN-gamma production by the remaining cells of these subsets, NK cells, conventional CD4+ T, Vdelta1, and Vdelta2 gamma-delta T cells. Most patients also displayed CMC due to their low counts of TH17 and TH1* cells. One patient died from disseminated Bacille Calmette-Guerin (BCG) vaccine infection, but, unexpectedly, all the other patients are still alive and clinically stable. RORgammaT is essential for protective immunity against mycobacteria and Candida in humans.

Tuberculosis (TB) has been a leading cause of death from a single infectious agent for decades. Bacille Calmette-Guerin (BCG) remains both the primary TB vaccine strategy and the oldest vaccine in circulation, with severe limitations in adult populations. Recently, live attenuated vaccine strategies, or generating safe strains of Mycobacterium tuberculosis (Mtb) through genetic engineering, have shown considerable promise. We previously developed an attenuated strain of Mtb lacking the nucleoid-associated protein Lsr2 ({Delta}lsr2) which is also phthiocerol dimycocerosates (PDIM) deficient and induces an immune response that represents an intermediate stage between the parental Mtb strain and BCG. In this study we examined the immune response of {Delta}lsr2 vaccinated mice in comparison to BCG and found a substantially stronger CD4 and CD8 T cell responses from {Delta}lsr2 vaccinated mice. Complementary, we conducted Mtb protection studies in {Delta}lsr2 and BCG vaccinated mice and guinea pigs, where we found that {Delta}lsr2 provided superior protection in both animals. This improved protection is shown with reduced bacterial burden and improved organ pathology in the lungs and spleen. Taken together, our work shows {Delta}lsr2 serves as a promising vaccine candidate for continued preclinical development.

Individuals with diabetes are at increased risk for severe outcomes from vaccine-preventable infections and often mount weaker immune responses to vaccination. The factors underlying this impaired immunity remain unclear, and defining them is critical to improve vaccine strategies for this vulnerable population. Here, we focused on insulin deficiency as a contributing factor. Following immunization with an alum-adjuvanted protein subunit vaccine, insulin-deficient mice exhibited reduced antigen-specific IgG antibody responses, decreased lymphocyte numbers, and lower germinal center B-cell counts within the vaccine-draining lymph node. Three-dimensional whole-organ light sheet microscopy combined with virtual reality-assisted analysis revealed significantly smaller germinal center volumes in insulin-deficient mice than controls. These findings indicate that insulin deficiency can significantly constrain germinal center responses and impair antibody production from vaccination. Our results provide foundational evidence that diabetes-associated metabolic changes can significantly and negatively influence the quality of vaccine-induced immunity and highlight insulin deficiency as a potential physiological factor.

Dysregulated gut homing of leukocytes drives chronic inflammation in Crohns disease (CD). We employed phage display selection campaigns with libraries of stabilized, constrained peptides against endogenous conformation states of the cannabinoid receptor CB2R on human T cells, to discover novel receptor antagonists with potential to inhibit gut homing. Cluster and frequency analysis of 50,000 enriched sequences resulted in expression and functional characterisation of 10 protein candidates using assays of glucose uptake, ERK phosphorylation (pERK) and beta-arrestin recruitment. Each candidate antagonised CB2R activity with recorded IC50 values of between 5-10 nM. Cannabinoid receptor nanodisc binding experiments and SPR confirmed CB2R selectivity. SLKC_09 with an IC50 of 5.4 nM, was studied in a mouse model of chronic ileitis where it significantly inhibited gut homing of CD4+ & CD8+ naive, effector and memory cell types. Our findings highlight an alternative route to therapeutic inhibition of leukocyte trafficking in CD with a biologic inhibitor of CB2R.