Cellular & Molecular Immunology

Background: Patients receiving anti-TNF treatment for chronic inflammatory disease display impaired antibody responses, but it remains unclear how immune memory formation is affected. We evaluated antibody responses and memory B cells (Bmem) after COVID-19 booster vaccination in inflammatory bowel disease (IBD) patients receiving anti-TNF treatment. Methodology: Blood was sampled at baseline, 1, and 6 months after WH1/BA.5 bivalent or XBB.1.5 monovalent vaccination from 27 IBD patients receiving intravenous anti-TNF and 44 controls. Neutralizing antibodies were measured using an infectious virus assay. SARS-CoV-2 spike receptor binding domain (RBD)-specific serum IgG was quantified by ELISA, and RBD-specific Bmem were immunophenotyped by flow cytometry using recombinant proteins from ancestral, Omicron BA.1, BA.5, XBB.1.5, and JN.1 variants. Results: Serum IgG to vaccine RBD and neutralizing antibodies in patients increased pre to 1 month post-vaccination, but were lower than controls. Ancestral-, BA.5- and XBB.1.5-specific Bmem increased after vaccination but were significantly lower in patients than controls. Within RBD-specific Bmem, frequencies of recently activated CD21lo cells were increased after vaccination, and were higher in patients than controls. Fewer antigen-specific Bmem in patients expressed IgG4, and more expressed IgG3 or IgD following vaccination. Following vaccination, more RBD-specific Bmem recognized multiple viral variants. However, patients had fewer Bmem that could bind to subvariants than controls. Conclusion: Antibody and Bmem responses to COVID-19 booster vaccination in anti-TNF-treated IBD patients displayed reduced capacity, durability and cross-reactivity, suggesting impaired immune memory for protection against breakthrough infection. This supports the recommendation for annual booster vaccination to prevent severe disease and viral spread.

Echovirus 18 (E18) is a predominant pathogen causing aseptic meningitis in children, and post-E18 infection frequently triggers myasthenia gravis-like autoimmune neurological damage. This pathological process relies on neonatal Fc receptor (FcRn)-mediated IgG transcytosis across mucosal barriers, and FcRn also acts as an essential functional receptor required for E18 attachment and uncoating during host cell invasion. At present, no E18-specific prophylactic vaccine has been clinically approved, and anti-FcRn monoclonal antibodies are the available therapeutics to alleviate autoantibody-mediated tissue injury. We constructed an integrated automated phylogenetic pipeline named evolution_conservation, which enables rapid tracing of the evolutionary position and genetic relatedness of clinical isolates to identify closely related strains from previous outbreaks. Serving as an in silico alternative to animal experiments, this pipeline supports reference-guided vaccine design and longitudinal comparative assessment of vaccine safety and efficacy, facilitates identification of patient populations presenting rare post-viral sequelae, and accelerates clinical trial progression. In this study, we inserted the pre-screened linear epitope E18-3 into a truncated hepatitis B core (HBc) scaffold to generate chimeric virus-like particles (VLPs). A non-invasive floss-based gingival mucosal immunization mouse model was established, with subcutaneous Freunds adjuvant immunization set as the control group. ELISA results confirmed that gingival mucosal delivery of particulate HBc-E18-3 VLPs alone could induce sustained high levels of antigen-specific intestinal IgG in vivo. Drawing on research paradigms of therapeutic neoantigen vaccines for tumor recurrence prevention, the evolution_conservation bioinformatic pipeline and mucosal VLP platform described herein establish an innovative framework for developing antigen-competitive prophylactic and therapeutic vaccines targeting FcRn for myasthenia gravis and autoimmune encephalitis.

IgM is the most ancient antibody isotype, playing an important role in both circulatory and mucosal immune responses across vertebrates, yet structural characterization of its polymeric forms is limited outside of mammals. Here, we report the cryo-electron microscopy structure of mallard duck secretory (S) IgM at 3.37-[A] resolution. The structure revealed a pentameric core globally similar to human SIgM, supporting the view that pentameric IgM is subject to strong evolutionary constraints. However, compared to mammalian structures, we observed species-specific differences at molecular interfaces. Surface plasmon resonance binding assays characterizing secretory component (SC)-IgM interactions supported structural observations and, when compared to IgA binding, revealed isotype-specific contributions from the avian SC N-terminal extension. Together, these findings establish a comparative structural framework for polymeric IgM across vertebrates and provide insight into how avian SIgM-specific features may support mucosal immunity in birds.

Efforts to develop a universal influenza vaccine have primarily focused on the surface-exposed viral hemagglutinin (HA), but neuraminidase (NA) is an additional target for cross-reactive, protective responses. Here, we used hyperglycosylation as an immunogen design approach to reshape anti-NA humoral immunity toward conserved antigenic regions. Iterative design produced a hyperglycosylated NA immunogen that retained enzymatic activity and reactivity to a conformation-specific antibody recognizing the conserved catalytic site. In mice, the hyperglycosylated immunogen elicited serum antibody responses of comparable magnitude to those elicited by the wild-type NA immunogen. However, serum antibodies elicited by the hyperglycosylated immunogen had increased breadth, recognizing N2 NAs from H2N2 and H3N2 viruses spanning nearly 65 years of antigenic drift, as well as a heterosubtypic N9 NA. Single B cell analyses identified a monoclonal antibody that competed with a component of the serum antibody response elicited by the hyperglycosylated immunogen, and structural characterization showed that it recognizes a previously undefined, conserved epitope at the NA tetramer interface. Passive transfer of this interface-directed antibody partially protected mice against lethal heterologous influenza challenge. Collectively, these data show that glycan shielding can reshape and enrich humoral responses toward a conserved antigenic region on NA. The immunogen and hyperglycosylation design strategy described here provide a template for developing next- generation NA-based influenza vaccines. ONE SENTENCE SUMMARYA hyperglycosylated influenza neuraminidase immunogen reshapes humoral immunity and elicits antibodies targeting a conserved tetramer-interface epitope.

Production of aberrant glycans by cancer cells constitutes a key immunosuppressive strategy to avoid destruction by immune cells. Although sialic acid-containing glycans are known to dampen the activation of lymphocytes, including Natural Killer (NK) cells, the role of fucose-containing glycans remains poorly characterized. In this work, we explored the role of Lewis X (LeX) in cancer cell-NK cell interactions. We induced ectopic expression of FUT9, an 1-3/4-fucosyltransferase, in two colorectal cancer cell lines and showed this enzyme only synthesized LeX structures but not sialyl-LeX. FUT9 introduction was not associated with altered MHC class I surface expression, nor with CD2 (which has been proposed as a receptor for LeX) binding to cancer cells. By inhibiting fucosylation we could demonstrate that CD2 binding was furthermore independent of surface fucosylated glycans in three independent cell lines. Lastly, FUT9/LeX had a limited role in cancer cell destruction and expression of activation markers by NK cells. Overall, our study suggests that, unlike sialylated glycans, 1-3/4-fucosylated glycans have limited impact on cancer cell evasion of NK cell-mediated destruction.

Tear fluid is amenable to non-invasive and repeated collection, making it a practical specimen for evaluating exercise-related physiological responses. However, the immediate proteome-wide alterations in tear fluid following acute exercise have not been characterised. In this study, we performed quantitative proteomic profiling of paired tear samples from healthy female participants before and immediately after a single exercise session using data-independent acquisition liquid chromatography-tandem mass spectrometry (DIA-LC-MS/MS). Among the 3,173 identified proteins, 744 were significantly altered post-exercise, of which 484 were up-regulated and 260 down-regulated. Functional enrichment analysis revealed that up-regulated proteins were predominantly associated with translation and ribosome biogenesis, whereas down-regulated proteins were involved in glycan metabolism, lysosomal processing, and extracellular matrix organisation. Collectively, these findings indicate that acute exercise elicits a rapid and coordinated reconfiguration of the tear proteome. This investigation provides a molecular basis for understanding exercise-mediated modulation of tear composition and ocular surface homeostasis.

Autoantibodies neutralizing type I IFNs (AAN-IFN-I) have been found in significant proportions of cases of severe, critical, and fatal COVID-19 pneumonia. We performed a systematic review of 54 studies reporting auto-Abs against type I IFNs and a meta-analysis of 20 studies reporting auto-Abs neutralizing type I IFNs published between 2020 and 2026. The meta-analysis included data for 11,380 SARS-CoV-2-infected individuals from Europe, North America, South America, Asia, the Middle East, North Africa and international multicenter cohorts, including 7,814 with severe or critical disease (69%). The pooled prevalence of AAN-IFN-I was estimated at 7.9% (95% CI, 6.0-10.4). Disease severity was strongly associated with AAN-IFN-I prevalence (OR, 11.7; 95%CI, 7.6-17.9; P=5x10^-29). The pooled prevalence of AAN-IFN-I reached 11.4% (95% CI, 10.2-12.7%) in patients with severe or critical COVID-19 and 15.3% (95% CI, 12.1-19.2%) in those who died. The prevalence of AAN-IFN-I increased with age in patients with severe, critical, or fatal COVID-19. AAN-IFN-I probably accounted for about 1.1 million of the 7.1 million deaths from COVID-19. AAN-IFN-I are strong, common, global determinants of life-threatening COVID-19 pneumonia.

The release of glucagon from pancreatic alpha cells is a core component of hypoglycaemic counter regulation. Several mechanisms regulate glucagon release including paracrine control by neighbouring cell types, and changes in extracellular glucose. While the inhibitory effect of glucose on glucagon secretion is well established, the exact way in which glucose metabolism contributes to alpha cell function remains unclear. Here, we use live-cell imaging of the redox potential in alpha cells within intact islets to investigate whether non-mitochondrial glucose metabolism contributes to the potentiation of glucagon secretion at low glucose. Our findings show that increased glucose metabolism through the pentose phosphate pathway elevates the cytosolic redox potential in alpha cells. Using a combination of antioxidant treatment and pre-incubation in 5 mM glucose, we find that the cytosolic redox potential affects PKA activity in alpha cells and that changes in whole body redox state affects the counterregulatory response in mice. These findings indicate that prior glucose-driven redox potential charging is essential for maintaining glucagon secretion at low glucose.

The continued emergence of betacoronaviruses underscores the urgent need for vaccines that provide broadly protective immunity. Here, we present an epitope-focused vaccine strategy targeting the conserved S2 stem-helix region of the spike fusion machinery, a broadly neutralizing antibody-(bnAb) epitope shared across betacoronaviruses yet partially occluded on the native spike. Immunization of non-human primates with engineered S2 stem-helix nanoparticle immunogens, alone or followed by a SARS-CoV-2 BA.1 spike mRNA boost, elicited broadly cross-reactive antibody responses against sarbecoviruses, merbecoviruses, and embecoviruses and neutralized SARS-CoV-2, multiple variants, other sarbecoviruses, and MERS-CoV. Vaccine-elicited monoclonal antibodies displayed broad in-vitro neutralizing activity and protected against both SARS-CoV-2 and MERS-CoV in-vivo. Structural analyses revealed conserved features between rhesus and human stem-helix bnAbs, supporting the translational potential. Overall, our findings provide proof-of-concept that epitope-focused nanoparticle immunogens can target partially occluded, immunoquiescent bnAb epitopes, laying the groundwork for pan-betacoronavirus vaccines that provide broad protection and strengthen pandemic preparedness. ONE SENTENCE SUMMARYEpitope-focused S2 stem-helix nanoparticle immunogens elicit protective broadly neutralizing antibodies (bnAbs) against diverse betacoronaviruses in non-human primates, establishing a framework for development of pan-betacoronavirus vaccines.

Current vaccines for respiratory viruses are primarily administered intramuscularly. Messenger RNA-lipid nanoparticle (LNP)-based intramuscular vaccination for respiratory coronaviruses induces strong systemic IgG antibody responses; they do not consistently elicit IgA in the upper and lower respiratory tracts. Using a synthetic consensus spike protein aimed to broadening immunity against SARS-like viruses, SarbConS, coupled to ferritin nanoparticles co-delivered with mastoparan-7 and an FDA-approved CpG adjuvant, we intranasally boost SARS-CoV-2-immune animals. This intranasal boosting strategy elicits durable mucosal IgA responses in the respiratory tract, along with robust systemic IgG responses, and demonstrates durable protection against SARS-CoV-2 and zoonotic SARS-like viruses from bats and pangolins. Intranasal delivery of mastoparan-7 and CpG with MERS-CoV spike protein similarly elicits MERS-CoV-specific mucosal IgA and protects against MERS-CoV challenge in mice. Moreover, we observe durable protection against these genetically divergent zoonotic SARS-like viral challenges compared to intramuscular mRNA-LNP or unadjuvanted intranasal spike boosters. Intranasal SarbConS-ferritin nanoparticle intranasal vaccination similarly elicited durable mucosal IgA and antigen-specific memory B cell responses in the airways. The protective efficacy of M7-CpG adjuvanted SarbConS ferritin nanoparticle intranasal boosters was abolished in IgA knockout mice, suggesting a requirement for IgA in mediating respiratory mucosal vaccine-mediated protection against coronavirus infection. Altogether, our results demonstrate that respiratory mucosal vaccination can elicit durable and cross-protective mucosal IgA responses against genetically diverse zoonotic coronaviruses with implications for improved mucosal vaccines for highly transmissible respiratory viral pathogens.

Substantial inter-individual variation in susceptibility to viral infection persists despite widespread vaccination, and its immunological basis remains poorly understood. We investigated how innate and adaptive immune responses contribute to susceptibility to SARS-CoV-2 infection during the early COVID-19 pandemic. We compared two groups of vaccinated individuals who either remained uninfected or became infected during the first Omicron wave. Blood samples were collected at baseline and 24 weeks later. Peripheral blood mononuclear cells (PBMCs) and polymorphonuclear neutrophils (PMNs) were isolated and stimulated with the TLR7/8 agonist R848 to assess innate responses. PBMCs were stimulated with SARS-CoV-2 peptide pools and highly purified inactivated viruses (ancestral and Omicron BA.1) to evaluate adaptive immunity. Prior to infection, individuals in the infected group exhibited reduced CD4 and CD8 T cells proliferative responses, alongside with increased TNF production across all stimulation conditions, despite largely comparable immune phenotypes, indicating a pre-existing functional immune deficit. Following infection, T-cell proliferation and IFN-gamma production were partially restored in response to viral antigens, although responses to Omicron BA.1 remained suboptimal. This functional deficit was accompanied by heightened inflammatory activity, including increased TNF and IFN-gamma production, elevated anti-nucleocapsid IgG3 levels, higher frequencies of B cells and myeloid cells, reduced circulating interferon-inducible T-cell Alpha Chemoattractant (I-TAC) concentrations, and a modest impairment in PMN IL-8 responses. Notably, these alterations were detectable prior to infection and persisted thereafter, indicating that they represent determinants rather than consequences of viral infection. Importantly, beyond differences in the magnitude of immune responses, protection was associated with the degree of functional coordination within the humoral compartment, as reflected by the relationship between Spike-binding antibodies and neutralizing activity. Together, these results demonstrate that susceptibility to Omicron infection is linked to a pre-existing and persistent functional immune imbalance affecting both innate and adaptive arms of immunity.

Post-acute infection syndromes (PAIS) follow viral syndromes including post-acute sequelae of COVID19 (PASC) which complicates 10-25% of SARS-CoV-2 infections. These syndromes lack precise explanatory mechanisms. We studied 173 human saliva proteomes during respiratory viral syndromes, seeking associations between 44 clinically-relevant protein expression patterns and subsequent sequelae counts. Exploratory models adjusted by extensive clinical annotations found interactions between 23 acutely-responsive proteins and SARS-CoV-2 infection that inversely predicted subsequent neurocognitive sequelae. An overlapping 19 acutely-responsive proteins during any acute respiratory viral syndrome inversely predicted general fatigue-related sequelae. Altogether, 29 proteins, derived from interferon stimulated genes (ISG), were uniformly beneficial, including 13 predictive of both neurocognitive and general sequelae. The proteins suggested both shared early pathobiology and virus-specific protective responses that shaped resolution of acute disease and different PAIS. Acutely elevated protective ISG proteins associated with reduced post-viral symptoms identify investigational starting points for novel mechanisms, diagnostics and therapeutics for PASC and PAIS.

A major goal for hepatitis C virus (HCV) vaccine development is to elicit broadly neutralizing antibodies (bNAbs) against the E1E2 glycoprotein complex located on the viral surface. Inducing HCV bNAbs requires engagement of their germline B cell precursors. HCV glycoproteins usually do not bind and activate inferred germline precursors of bNAbs (igl-bNAbs), possibly because most circulating strains contain non-conserved isolate-specific residues, even in bNAb epitopes. Here, we generated stabilized native-like soluble E1E2 (sE1E2) antigens based on a consensus sequence of HCV (HepCon) to limit the exposure of antigenically rare residues. The antigenicity and glycosylation profiles show that HepCon sE1E2 resembles a native-like E1E2 heterodimer. HepCon sE1E2 induced cross-reactive neutralizing antibody responses as a soluble protein immunogen and as membrane-anchored mRNA-delivered immunogen in animals. Importantly, HepCon sE1E2 engages multiple igl-bNAbs against two major epitopes: antigenic region 3 (AR3), which is targeted by igl-bNAbs derived from the widely expressed human VH1-69 B cell gene, and antigenic region 4 (AR4), which is only present on native-like E1E2. Nanoparticles with HepCon sE1E2 efficiently activated B cell lines expressing AR3 and AR4 igl-bNAb B cell receptors in vitro. Finally, using HepCon sE1E2 we elucidated the atomic contacts of an AR3 igl-bNAb by cryo-electron microscopy. Thus, HepCon sE1E2 is a promising candidate for germline-targeting vaccination strategies.

Chikungunya virus (CHIKV) disease typically resolves following acute infection; however, some individuals develop chronic CHIKV disease (CCD) characterized by persistent, debilitating joint pain. Antibodies help clear CHIKV through neutralization and Fc effector functions. Previous studies have associated CCD with a poor neutralizing antibody response; however, the role of Fc effector functions in CCD development remains unclear. Here, purified IgG from post-acute serum of individuals who either resolved CHIKV disease or developed CCD was evaluated for IgG activity and Fc effector functions to identify correlations with disease progression and biomarkers for CCD. Resolution was associated with higher levels of CHIKV-specific IgG and IgG1 and stronger CHIKV neutralization. Regression analysis identified bulk IgG2 as a strong predictor of CHIKV disease progression. Development of CCD was associated with enhanced IgG-mediated complement deposition on infected cells. These findings suggest that localized complement activation at sites of infection may contribute to persistent inflammation underlying CCD.

Sensory neurons have been increasingly recognized as vital contributors to deep tissue function. However, how these specialized neurons contribute to salivary gland function remains largely undefined. Here, we uncover a role for trigeminal somatosensory afferents in salivary gland perception and function using in situ-based classification, in vivo calcium imaging, behavioral assays, and targeted ablation. Retrograde labeling from the submandibular gland complex revealed substantial direct innervation from trigeminal neurons. Further categorization confirmed that Trpv1+ sensory neurons provided dense innervation of the Whartons ducts. TRPV1 agonist ductal infusion directly activated gland complex-associated neurons in the trigeminal ganglia and evoked a robust pain phenotype. Targeted Trpv1+ ablation disrupted Whartons ducts structure and dramatically reduced stimulated saliva volume. Our work provides the first evidence that Trpv1+ sensory neurons maintain salivary architecture and are necessary for stimulated saliva production, revealing a vital interoceptive role for direct trigeminal innervation in submandibular gland health.

Interactions between intraepithelial lymphocytes (IELs) and the intestinal epithelium are central to mucosal homeostasis and disease. However, mechanistic in vitro studies describing their crosstalk in humans are limited by scarceness of primary material and insufficient knowledge about co-culture requirements. Here, we establish an autologous human duodenal IEL-organoid co-culture system encompassing expandable and bankable IEL and organoid protocols, with co-culture conditions that allow viability of both cell types. This system enables successive interrogation of lympho-epithelial interactions starting from minimal biopsy material. Under baseline conditions, CD45CD8CD103TCR{beta} IELs retain tissue-residency and effector features and induce an epithelial interferon response and chemokine production, without overt epithelial apoptosis. IL-15 and IL-21, essential cytokines involved in IEL-activation in intestinal enteropathies like celiac disease, increases granzyme B expression and interferon-{gamma} secretion but do not trigger epithelial cell death. However, enforcing IEL-epithelial contact using an anti-CD3-anti-Ep-CAM bispecific antibody induces epithelial apoptosis accompanied by increased tumor necrosis factor (TNF) and FAS-ligand (FASLG) secretion. These findings validate the platforms ability to resolve non-destructive and cytotoxic lympho-epithelial interaction and provide a tractable system for studying intestinal inflammation and immune-mediated epithelial cell death.

SARS-CoV-2 evolution has reduced the efficacy of clinical monoclonal antibodies, underscoring the need for therapeutics targeting conserved viral regions. The Spike (S) heptad repeat 2 (HR2) stem helix is highly conserved across SARS-CoV-2 variants and related betacoronaviruses. Although antibodies to this region can neutralize infection, their natural occurrence and evolution remain poorly understood. We previously identified human neutralizing antibodies to a conserved peptide within this region (HR2 coldspot). Here, we show that plasma IgG reactivity to this region remains rare, even after repeated antigen exposure. Longitudinal analysis over 30 months revealed continued somatic hypermutation of HR2-specific antibodies, yet none surpassed the potency or breadth of hr2.016, which emerged shortly after primary infection. Crystal structures of four HR2 stem helix antibodies revealed convergent recognition across distinct antibody lineages. Comparison of hr2.016 with its non-neutralizing clonal relative hr2.086 showed that structural convergence masks distinct binding kinetics. Surface plasmon resonance and molecular dynamics simulations revealed a more stable interaction network for hr2.016, with slower dissociation and prolonged S residence time. Neutralization required the IgG format, supporting an avidity-driven mechanism. Together, these findings define kinetic and avidity constraints governing neutralization at the HR2 stem helix and position hr2.016 as a resilient therapeutic candidate.

Maintaining brain homeostasis is crucial for proper function of the central nervous system and has traditionally been attributed to neuronal and glial interactions. However, recent research highlights the essential role of brain-resident immune cells in this process. Our study characterizes brain-specific CD8+ T cells and elucidates their significant contribution to brain homeostasis and behavior. We identified a distinct population of CD8+ T cells that infiltrates the brain during early development, undergoes clonal expansion, and acquires effector memory-like characteristics through interactions with microglia. Notably, the absence of these cells results in hyperactivation of neuronal activity and abnormal behaviors, due to loss of regulation of interferon-gamma (IFN-{gamma}) secreted by CD8+ T cells. Our findings demonstrate that IFN-{gamma} secreting brain-specific CD8+ T cells are crucial for maintaining the physiological level of neuronal excitability and normal behavioral patterns. This study provides novel insights into neuroimmune interactions, emphasizing the critical role of CD8+ T cells in sustaining brain function and behavior.

CD40, a co-stimulatory receptor of the tumor necrosis factor receptor superfamily expressed on microglia and macrophages, is an upstream regulator of innate antiviral defense in coronavirus-induced neuroinflammation, but its specific role in the visual system remains undefined. Here, we demonstrate that CD40 signaling is essential for restricting retrograde axonal transport of the murine {beta}-coronavirus RSA59 from the brain to the retina and for preventing chronic neurodegeneration in a model of viral optic neuritis. Wild-type and CD40-/- mice were intracranially inoculated with RSA59, and viral burden, neuroinflammation, and neurodegeneration were assessed at acute (day 5), bridging (day 7), and chronic (day 30) stages. CD40-/- mice exhibited significantly increased clinical severity and [~]30% mortality by day 12 post-infection, compared to 100% survival in WT mice. CD40 deficiency resulted in elevated viral loads in the optic nerve and enhanced retrograde viral dissemination across all retinal layers, whereas in WT mice, the virus was largely confined to the ganglion cell layer. CD40-/- mice exhibited impaired early microglial activation and compensatory astrogliosis during the acute and bridging phases. By day 30 p.i., although viral-N protein was undetectable by immunohistochemistry in both genotypes, CD40-/- optic nerves retained significantly higher persistent viral RNA and exhibited extensive demyelination, oligodendrocyte loss, axonal depletion, and upregulation of phagocytic markers. Critically, CD40-/- retinas showed persistent astrogliosis, accumulation of phagocytic microglia/macrophages, and a significant loss of Brn3a+ retinal ganglion cells. These findings establish CD40 as a critical molecular node governing coronavirus optic neuritis, linking early innate immune regulation to long-term neuronal survival.

Inflammatory bowel disease (IBD) is associated with chronic intestinal inflammation and gut microbial dysbiosis, yet effective microbiome-targeted therapeutics remain limited. Here, we investigated the anti-inflammatory and microbiome-modulating activities of metabolites isolated from Garcinia brassii, an endemic species of the Australian Wet Tropics. Five compounds, including a new natural product named garcitine, were isolated and structurally characterised. In human immune cells, garcinol and garcinia biflavonoid 1 significantly suppressed lipopolysaccharide-induced production of IL-1{beta}, IL-6, and TNF without detectable cytotoxicity, while parvifoliol F selectively inhibited IL-1{beta} release. Therapeutic efficacy was further evaluated in a TNBS-induced murine colitis model, where garcinia biflavonoid 1 and parvifoliol F significantly reduced colonic inflammation and improved histopathological outcomes. 16S rRNA sequencing demonstrated that both compounds restored gut microbial homeostasis by reversing colitis-associated dysbiosis and reducing inflammation-associated microbial signatures. Functional pathway prediction further suggested suppression of pro-inflammatory microbial metabolic pathways following treatment. Together, these findings demonstrate that Garcinia-derived metabolites alleviate experimental colitis through coordinated immunomodulatory and microbiome-reprogramming mechanisms and identify garcinia biflavonoid 1 and parvifoliol F as promising candidates for microbiome-targeted IBD therapeutics.