Antigen-specific Responses Research Articles

Establishment of CD1b-restricted immunity to lipid antigens in the pulmonary response to Mycobacterium tuberculosis infection.

CD1 is an antigen-presenting glycoprotein homologous to MHC I; however, CD1 proteins present lipid rather than peptide antigens. CD1 proteins are well established to present lipid antigens of Mycobacterium tuberculosis (Mtb) to T cells, but understanding the role of CD1-restricted immunity in vivo in response to Mtb infection has been limited by the availability of animal models naturally expressing the CD1 proteins implicated in human response: CD1a, CD1b, and CD1c. Guinea pigs, in contrast to other rodent models, express four CD1b orthologs, and here we utilize the guinea pig to establish the kinetics of gene and protein expression of CD1b orthologs, as well as the Mtb lipid-antigen and CD1b-restricted immune response at the tissue level over the course of Mtb infection. Our results indicate transient upregulation of CD1b expression during the effector phase of adaptive immunity that wanes with disease chronicity. Gene expression indicates that the upregulation of CD1b is the result of transcriptional induction across all CD1b orthologs. We show high CD1b3 expression on B cells, and identify CD1b3 as the predominant CD1b ortholog in pulmonary granuloma lesions. We identify ex vivo cytotoxic activity directed against CD1b that parallels the kinetic changes in CD1b expression in Mtb-infected lungs and spleen. This study confirms that CD1b expression is modulated by Mtb infection in lung and spleen, leading to pulmonary and extrapulmonary CD1b-restricted immunity as a component of the antigen-specific response to Mtb infection.

PRR adjuvants restrain high stability peptides presentation on APCs.

Adjuvants can affect APCs function and boost adaptive immune responses post-vaccination. However, whether they modulate the specificity of immune responses, particularly immunodominant epitope responses, and the mechanisms of regulating antigen processing and presentation remain poorly defined. Here, using overlapping synthetic peptides, we screened the dominant epitopes of Th1 responses in mice post-vaccination with different adjuvants and found that the adjuvants altered the antigen-specific CD4+ T-cell immunodominant epitope hierarchy. MHC-II immunopeptidomes demonstrated that the peptide repertoires presented by APCs were significantly altered by the adjuvants. Unexpectedly, no novel peptide presentation was detected after adjuvant treatment, whereas peptides with high binding stability for MHC-II presented in the control group were missing after adjuvant stimulation, particularly in the MPLA- and CpG-stimulated groups. The low-stability peptide present in the adjuvant groups effectively elicited robust T-cell responses and formed immune memory. Collectively, our results suggest that adjuvants (MPLA and CpG) inhibit high-stability peptide presentation instead of revealing cryptic epitopes, which may alter the specificity of CD4+ T-cell-dominant epitope responses. The capacity of adjuvants to modify peptide-MHC (pMHC) stability and antigen-specific T-cell immunodominant epitope responses has fundamental implications for the selection of suitable adjuvants in the vaccine design process and epitope vaccine development.

PRR adjuvants restrain high stability peptides presentation on APCs

Adjuvants can affect APCs function and boost adaptive immune responses post-vaccination. However, whether they modulate the specificity of immune responses, particularly immunodominant epitope responses, and the mechanisms of regulating antigen processing and presentation remain poorly defined. Here, using overlapping synthetic peptides, we screened the dominant epitopes of Th1 responses in mice post-vaccination with different adjuvants and found that the adjuvants altered the antigen-specific CD4+ T-cell immunodominant epitope hierarchy. MHC-II immunopeptidomes demonstrated that the peptide repertoires presented by APCs were significantly altered by the adjuvants. Unexpectedly, no novel peptide presentation was detected after adjuvant treatment, whereas peptides with high binding stability for MHC-II presented in the control group were missing after adjuvant stimulation, particularly in the MPLA- and CpG-stimulated groups. The low-stability peptide present in the adjuvant groups effectively elicited robust T-cell responses and formed immune memory. Collectively, our results suggest that adjuvants (MPLA and CpG) inhibit high-stability peptide presentation instead of revealing cryptic epitopes, which may alter the specificity of CD4+ T-cell-dominant epitope responses. The capacity of adjuvants to modify peptide–MHC (pMHC) stability and antigen-specific T-cell immunodominant epitope responses has fundamental implications for the selection of suitable adjuvants in the vaccine design process and epitope vaccine development.

Proteomic approach to identify host cell attachment proteins provides protective Pseudomonas aeruginosa vaccine antigen FtsZ

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes severe nosocomial infections in susceptible individuals due to the emergence of multidrug-resistant strains. There are no approved vaccines against P. aeruginosa infections nor candidates in active clinical development, highlighting the need for novel candidates and strategies. Using a cell-blot proteomic approach, we reproducibly identified 49 proteins involved in interactions with human lung epithelial cells across four P. aeruginosa strains. Among these were cell division protein FtsZ and outer membrane protein OpmH. Escherichia coli BL21 cells overexpressing recombinant FtsZ or rOpmH showed a 66- and 15-fold increased ability to attach to 16HBE14o− cells, further supporting their involvement in host cell attachment. Both antigens led to proliferation of NK and CD8+ cytotoxic T cells, significant increases in the production of IFN-γ, IL-17A, TNF and IL-4 in immunised mice and elicited strong antigen-specific serological IgG1 and IgG2c responses. Immunisation with FtsZ significantly reduced bacterial burden in the lungs by 1.9-log CFU and dissemination to spleen by 1.8-log CFU. The protective antigen candidate, FtsZ, would not have been identified by traditional approaches relying on either virulence mechanisms or sequence-based predictions, opening new avenues in the development of an anti-P. aeruginosa vaccine.

The characteristics of T-cell receptor repertoire in relation to systemic immune response of patients with ischemic stroke.

T lymphocytes play a vital role in the immune-inflammatory response following a stroke. However, the specific mechanisms behind the contrasting functions of T cells in the brain and peripheral tissues after a stroke remain unclear and require further investigation. T-cell receptors (TCRs) are essential in controlling how T lymphocytes develop and become active. This study aims to gain a deeper understanding of the biological function of T lymphocytes by analyzing the TCR repertoire in patients who have experienced an acute ischemic stroke (AIS). High-throughput TCR sequencing was conducted on peripheral blood samples from 25 AIS patients and 10 healthy controls. We compared the percentage of T cells and the characteristics of the TCR repertoire, specifically focusing on the recombination of V(D)J gene fragments and the diversity of the complementarity determining region 3 (CDR3) of the Vβ gene. Additionally, this study analyzed the potential biological significance of the skewed TCR repertoire in AIS patients. In patients with AIS, the proportion of circulating lymphocytes (LY%) decreased while the systemic immune-inflammatory index (SII) increased compared to healthy controls. The average number of TCR read pairs decreased, corresponding with the presence of lymphopenia. However, the recombination of V(D)J gene fragments, the number of CDR3 clonotypes, and the diversity of CDR3 was elevated in the peripheral blood of AIS patients. Furthermore, the increased number of CDR3 amino acid or nucleotide clonotypes was negatively correlated with neurologic deficits but positively correlated with AIS patients' systemic immune condition and functional outcomes. Our findings suggest that both immunosuppression and enhanced antigen-specific T-cell response may exist in the periphery of the AIS patients. Further investigation into the mechanisms underlying these opposing changes may lead to the discovery of novel targets to reverse immunosuppression or mitigate the detrimental effects of T cells in the lesioned brain of AIS patients.

Enhancing preventive and therapeutic cancer vaccine efficacy through biotherapeutic ligand-associated extracellular vesicles

Extracellular vesicles (EVs), secreted by almost all living cells, have gained significant attention for their role in intercellular communication and their potential as versatile carriers for biotherapeutics. However, the clinical translation of EV-based therapies faces significant challenges, primarily due to the lack of efficient methods for loading biotherapeutic agents into EVs. This study introduces a simple, reproducible strategy for the simultaneous incorporation of various biotherapeutics within EVs. The process is gentle and preserves the essential physicochemical and biological characteristics of EVs, thereby protecting labile ligands from premature degradation and elimination. The binding and uptake efficiency of EVs by target cells reached approximately 97 % within 24 h of incubation. Administration of EVs loaded with oligodeoxynucleotides (ODN) resulted in a 4-fold increase in IFNγ+ CD4+ T cells and a 5-fold increase in IFNγ+ CD8+ T cells in the spleens and lymph nodes. Additionally, the co-administration of EVs with ODN and ovalbumin (OVA) induced elevated Th1-biased antibody responses and antigen-specific cytotoxic T-cell responses, providing long-lasting complete protection in 60 % of mice against T-cell thymoma challenge. Furthermore, EVs associated with three different ligands (OVA, CpG-ODN, and α-GalCer) effectively regressed established murine melanoma and significantly improved survival rates in mice. This study presents a powerful and promising approach to overcoming the limitations of EV-based cancer vaccines, advancing the development of effective cancer immunotherapies. SummaryImmunization with EVs that are co-associated with antigen and biotherapeutic cargo through a lyophilization-based technique elicits potent anti-cancer immunity.

Inserting CTL Epitopes of the Viral Nucleoprotein to Improve Immunogenicity and Protective Efficacy of Recombinant Protein against Influenza A Virus.

Conserved influenza virus proteins, such as the hemagglutinin stem domain (HA2), nucleoprotein (NP), and matrix protein (M), are the main targets in the development of universal influenza vaccines. Previously, we constructed a recombinant vaccine protein Flg-HA2-2-4M2ehs containing the extracellular domain of the M2 protein (M2e) and the aa76-130 sequence of the second HA subunit as target antigens. It demonstrated immunogenicity and broad protection against influenza A viruses after intranasal and parenteral administration. This study shows that CD8+ epitopes of NP, inserted into a flagellin-fused protein carrying M2e and HA2, affect the post-vaccination immune humoral response to virus antigens without reducing protection. No differences were found between the two proteins in their ability to stimulate the formation of follicular Th in the spleen, which may contribute to a long-lasting antigen-specific humoral response. The data obtained on Balb/c mice suggest that the insertion of CTL NP epitopes into the flagellin-fused protein carrying M2e and HA2 reduces the antibody response to M2e and A/H3N2. In C57Bl6 mice, this stimulates the formation of NP-specific CD8+ Tem and virus-specific mono- and multifunctional CD4+ and CD8+ Tem in the spleen and completely protects mice from influenza virus subtypes A/H1N1pdm09 and A/H3N2.

Development of bovine IgG3-specific assays using a novel recombinant single-domain binding reagent

Cattle express three subclasses of IgG antibody - IgG1, IgG2 and IgG3. Unlike IgG1 and IgG2, IgG3 was described relatively recently and the role of this subclass in immunity is unknown. Using recombinant bovine IgG1, IgG2 and IgG3 monoclonal antibodies (mAbs), we demonstrated that only one of the commercially available anti-bovine IgG mAbs tested was able to recognize IgG3, and no mAb exclusively bound IgG3. Here, we evaluated a small ankyrin repeat protein, called Ankyron™ AZS40101, that was generated to bind to bovine IgG3. Ankyron™ AZS40101 bound specifically to IgG3 with minimal reactivity to IgG1 and IgG2. Ankyron™ AZS40101 was shown to be useful in ELISA assays as either a capture or detection reagent. Utilisation of Ankyron™ AZS40101 alongside IgG1 and IgG2 specific mAbs to detect antigen-specific IgG subclasses in the serum of cattle sequentially vaccinated with heterologous foot-and-mouth disease virus capsid antigens revealed a low-level antigen-specific IgG3 response, in addition to IgG1 and IgG2 responses. Assessment of the total IgG1, IgG2 and IgG3 levels in healthy cattle plasma samples showed that IgG3 was measurable at a mean concentration of 0.19mg/mL, although this was significantly lower than those of IgG1 (mean 3.28mg/mL) and IgG2 (mean 3.41mg/mL). Thus, Ankyron™ AZS40101 is a new reagent that provides utility for measurement of bovine IgG3 responses to infection and vaccination.

B cell-intrinsic IFN-γ promotes excessive CD11c+ age-associated B cell differentiation and compromised germinal center selection in lupus mice

CD11c+ age-associated B cells (ABCs) have emerged as a key component in protective and autoreactive B cell responses. Lupus is an autoimmune disorder linked to reduced efficacy of vaccines and increased susceptibility to infections. Previously, we reported that excessive CD11c+ ABCs not only significantly contribute to autoantibody production but also promote aberrant T cell activation and compromised affinity-based germinal center selection in response to immunization in lupus mice. Yet, the regulation of CD11c+ ABC differentiation is not fully understood. In this study, we show that B cell-intrinsic IFN-γ is required for excessive CD11c+ ABC differentiation in lupus mice. B cell-intrinsic IFN-γ is mainly produced by CD11c+ ABCs. IFN-γ-deficiency leads to decreased expression of ABC characteristic genes. We further show that ablating IFN-γ can normalize T cell overactivation and rescue antigen-specific GC responses in lupus mice. Our study offers insight into the crucial role of B cell-intrinsic IFN-γ in promoting excessive CD11c+ ABC differentiation, which compromises affinity-based germinal center selection and affinity maturation in lupus, providing a potential strategy to normalize vaccine responses in lupus.

A Metal-Phenolic Network-Enabled Nanoadjuvant to Modulate Immune Responses.

The presence of hierarchical suppressive pathways in the immune system combined with poor delivery efficiencies of adjuvants and antigens to antigen-presenting cells are major challenges in developing advanced vaccines. The present study reports a nanoadjuvant constructed using aluminosilicate nanoparticles (as particle templates), incorporating cytosine-phosphate-guanosine (CpG) oligonucleotides and small-interfering RNA (siRNA) to counteract immune suppression in antigen-presenting cells. Furthermore, the application of a metal-phenolic network (MPN) coating, which can endow the nanoparticles with protective and bioadhesive properties, is assessed with regard to the stability and immune function of the resulting nanoadjuvant in vitro and in vivo. Combining the adjuvanticity of aluminum and CpG with RNA interference and MPN coating results in a nanoadjuvant that exhibits greater accumulation in lymph nodes and elicits improved maturation of dendritic cells in comparison to a formulation without siRNA or MPN, and with no observable organ toxicity. The incorporation of a model antigen, ovalbumin, within the MPN coating demonstrates the capacity of MPNs to load functional biomolecules as well as the ability of the nanoadjuvant to trigger enhanced antigen-specific responses. The present template-assisted fabrication strategy for engineering nanoadjuvants holds promise in the design of delivery systems for disease prevention, as well as therapeutics.

Naturally acquired adaptive immunity to Streptococcus pneumoniae is impaired in rheumatoid arthritis patients.

Patients with rheumatoid arthritis (RA) have an increased susceptibility to infections, including those caused by Streptococcus pneumoniae. Why RA is associated with increased susceptibility to S. pneumoniae is poorly understood. This study aims to assess the effects of RA and B-cell depletion therapy on naturally acquired antibody responses to 289 S. pneumoniae protein antigens using a novel protein array. IgG responses to S. pneumoniae were characterised in serum from RA patients and disease controls (myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)) using whole-cell ELISA, a flow cytometry opsonisation assay and an S. pneumoniae protein array. For the RA patients, results were compared before and after B-cell depletion therapy. Compared to a well-characterised disease control group of ME/CFS patients, RA patients had reduced antibody responses to multiple S. pneumoniae protein antigens, with significant IgG recognition of approximately half the number of antigens along with reduced median strengths of these responses. Reduction in multiple array antigen-specific responses also correlated with reduced IgG opsonisation of S. pneumoniae. Although B-cell depletion therapy with rituximab did not reduce overall IgG recognition of S. pneumoniae in the RA group, it was associated with marked disruption of pre-existing IgG repertoire to protein antigens in individual patients. These data show RA is associated with major disruption of naturally acquired adaptive immunity to S. pneumoniae, which can be assessed rapidly using a protein antigen array and is likely to contribute towards the increased incidence of pneumonia in patients with RA.

The role of the immune response in developing tuberculosis infection: from latent infection to active tuberculosis

Despite advancements in modern medicine, tuberculosis continues to be one of the leading causes of death globally. Findings indicate that COVID-19 may trigger the activation of tuberculosis infection (TB), leading to its spread. Despite the development of new immunological diagnostic methods for latent tuberculosis infection (LTBI), it is still unclear how the infection transitions to an active TB state. The goal of the study is to provide insights into the progression of tuberculosis infection from a latent to an active state. This article presents recent research data focused on investigating the pathogenesis of LTBI, particularly the immune responses in the interaction between Mycobacteria tuberculosis (Mtb) and the host. It describes the mechanisms of T-cell immunity and cytokine activation, supporting the concept of type 1, type 2, and type 3 immune responses. According to the conducted studies, Th17 cells have a significant role in the development of type 3 antigen-specific responses. The cytokines IL-6 and IL-23 activate STAT3, which is necessary to trigger the expression of Th17. Future research on the role of Th17 cells and cytokines, particularly IL-6 and IL-21, may be beneficial in understanding the shift from LTBI to active TB.

In vivo edited eosinophils reconcile antigen specific Th2 response and mitigate airway allergy

BackgroundImprovement is needed in the remedies used to control Th2 polarization. Bioengineering approaches have modified immune cells that have immunosuppressive functions. This study aims to generate modified eosinophils (Meos) in vivo and use Meos to balance Th2 polarization and reduce airway allergy.MethodsA cell editor was constructed. The editor contained a peptide carrier, an anti-siglec F antibody, MHC II, ovalbumin, and LgDNA (DNA extracted from a probiotic, Lactobacillus rhamnosus GG). Which was designated as Cedit. Meos are eosinophils modified using Cedits. An airway Th2 polarization mouse model was established used to test the effect of Meos on suppressing airway allergy.ResultsThe Cedits remained physically and chemically stable in solution (pH7.2) for at least 96 h. Cedits specifically bound to eosinophils, which are designated as Meos. Meos produced programmed death ligand-1 (PD-L1); the latter induced antigen specific CD4+ T cell apoptosis. Administration of Cedits through nasal instillations generated Meos in vivo, which significantly reduced the frequency of antigen specific CD4+ T cells in the airways, and mitigated airway Th2 polarization.ConclusionsWe constructed Cedit, which could edit eosinophils into Meos in vivo. Meos could induce antigen specific CD4+ T cell apoptosis, and reconcile airway Th2 polarization.

Interleukin 9 mediates T follicular helper cell activation to promote antibody responses.

Antigen-specific humoral responses are orchestrated through complex interactions among immune cells in lymphoid tissues, including the collaboration between B cells and T follicular helper (Tfh) cells. Accumulating evidence indicates a crucial role for interleukin-9 (IL-9) in the formation of germinal centers (GCs), enhancing the generation of class-switched high-affinity antibodies. However, the exact function of IL-9 in Tfh cell regulation remains unclear. In this study, we examined the humoral immune responses of CD4Cre/+Il9rafl/fl mice, which lack an IL-9-specific receptor in Tfh cells. Upon intraperitoneal immunization with sheep red blood cells (SRBCs), CD4Cre/+Il9rafl/fl mice displayed diminished levels of SRBC-specific IgG antibodies in their sera, along with reduced levels of GC B cells and plasma cells. Notably, Il9ra-deficient Tfh cells in the spleen exhibited decreased expression of their signature molecules such as B-cell lymphoma 6, C-X-C chemokine receptor 5, IL-4, and IL-21 compared to control mice. In models of allergic asthma induced by house dust mite (HDM) inhalation, CD4Cre/+Il9rafl/fl mice failed to elevate serum levels of HDM-specific IgE and IgG. This was accompanied by reductions in Tfh cells, GC B cells, and plasma cells in mediastinal lymph nodes. Furthermore, group 2 innate lymphoid cells (ILC2s) were identified as producers of IL-9 under immunizing conditions, possibly induced by leukotrienes released by activated IgD+ B cells around the T-B border. These observations may indicate the critical role of IL-9 receptor signaling in the activation of Tfh cells, with ILC2s potentially capable of supplying IL-9 in organized lymphoid tissues.

Full-length single-cell BCR sequencing paired with RNA sequencing reveals convergent responses to pneumococcal vaccination

Single-cell RNA sequencing (scRNA-seq) can resolve transcriptional features from individual cells, but scRNA-seq techniques capable of resolving the variable regions of B cell receptors (BCRs) remain limited, especially from widely-used 3′-barcoded libraries. Here, we report a method that can recover paired, full-length variable region sequences of BCRs from 3′-barcoded scRNA-seq libraries. We first verify this method (B3E-seq) can produce accurate, full-length BCR sequences. We then apply this method to profile B cell responses elicited against the capsular polysaccharide of Streptococcus pneumoniae serotype 3 (ST3) by glycoconjugate vaccines in five infant rhesus macaques. We identify BCR features associated with specificity for the ST3 antigen which are present in multiple vaccinated monkeys, indicating a convergent response to vaccination. These results demonstrate the utility of our method to resolve key features of the B cell repertoire and profile antigen-specific responses elicited by vaccination.

SARS-CoV-2-specific CD8+ T cells from people with long COVID establish and maintain effector phenotype and key TCR signatures over 2 years

Long COVID occurs in a small but important minority of patients following COVID-19, reducing quality of life and contributing to healthcare burden. Although research into underlying mechanisms is evolving, immunity is understudied. SARS-CoV-2-specific T cell responses are of key importance for viral clearance and COVID-19 recovery. However, in long COVID, the establishment and persistence of SARS-CoV-2-specific T cells are far from clear, especially beyond 12 mo postinfection and postvaccination. We defined ex vivo antigen-specific B cell and T cell responses and their T cell receptors (TCR) repertoires across 2 y postinfection in people with long COVID. Using 13 SARS-CoV-2 peptide-HLA tetramers, spanning 11 HLA allotypes, as well as spike and nucleocapsid probes, we tracked SARS-CoV-2-specific CD8+ and CD4+ T cells and B-cells in individuals from their first SARS-CoV-2 infection through primary vaccination over 24 mo. The frequencies of ORF1a- and nucleocapsid-specific T cells and B cells remained stable over 24 mo. Spike-specific CD8+ and CD4+ T cells and B cells were boosted by SARS-CoV-2 vaccination, indicating immunization, in fully recovered and people with long COVID, altered the immunodominance hierarchy of SARS-CoV-2 T cell epitopes. Meanwhile, influenza-specific CD8+ T cells were stable across 24 mo, suggesting no bystander-activation. Compared to total T cell populations, SARS-CoV-2-specific T cells were enriched for central memory phenotype, although the proportion of central memory T cells decreased following acute illness. Importantly, TCR repertoire composition was maintained throughout long COVID, including postvaccination, to 2 y postinfection. Overall, we defined ex vivo SARS-CoV-2-specific B cells and T cells to understand primary and recall responses, providing key insights into antigen-specific responses in people with long COVID.

Different Antigen-Specific CD4+ and CD8+ T-Cell Response against HCMV Proteins in Pregnant Women with Primary Infection and in Control Subjects with Remote Infection.

Background/Objectives: Human cytomegalovirus (HCMV) is the most frequent cause of congenital infections. The HCMV-specific T-cell response in primary infection may help define reliable correlates of immune protection in pregnancy. In this study, the antigen-specific T-cell response against different HCMV proteins (IE-1, pp65, gB, gHgLpUL128L) was investigated in pregnant women with primary infection and in control subjects with remote infection to identify possible components of a vaccine. Methods: Blood samples from 35 pregnant women with HCMV primary infection and 30 HCMV-seropositive healthy adult subjects with remote infection were tested. The antigen-specific T-cell response was measured using cytokine intracellular staining after stimulation with IE-1, pp65, gB and gHgLpUL128L peptides pool. Results: The pp65-specific CD4+ T-cell response was higher in pregnant women with HCMV primary infection at the late time point and in control subjects with remote infection, while the pregnant women at the early time point showed a higher gB-specific CD8+ T-cell response. Regarding the CD4+ and CD8+ T-cell phenotypes, we observed that HCMV-specific CD4+ and CD8+ T cells expressing CD45RA+ remained constant in pregnant women with primary infection at the early and late time points and in subjects with remote infection, while HCMV-specific CD4+ and CD8+ T cells expressing IL-7R+ or producing IL-2 were higher in control subjects with remote infection than in pregnant women with HCMV primary infection. Conclusions: The T-cell response was higher against gB in the early phase of infection and against pp65 in the late phase. Therefore, these proteins should be taken into consideration as candidates for a vaccine.

A mouse protozoan boosts antigen-specific mucosal IgA responses in a specific lipid metabolism- and signaling-dependent manner

IgA antibodies play an important role in mucosal immunity. However, there is still no effective way to consistently boost mucosal IgA responses, and the factors influencing these responses are not fully understood. We observed that colonization with the murine intestinal symbiotic protozoan Tritrichomonas musculis (T.mu) boosted antigen-specific mucosal IgA responses in wild-type C57BL/6 mice. This enhancement was attributed to the accumulation of free arachidonic acid (ARA) in the intestinal lumen, which served as a signal to stimulate the production of antigen-specific mucosal IgA. When ARA was prevented from undergoing its downstream metabolic transformation using the 5-lipoxygenase inhibitor zileuton or by blocking its downstream biological signaling through genetic deletion of the Leukotriene B4 receptor 1 (Blt1), the T.mu-mediated enhancement of antigen-specific mucosal IgA production was suppressed. Moreover, both T.mu transfer and dietary supplementation of ARA augmented the efficacy of an oral vaccine against Salmonella infection, with this effect being dependent on Blt1. Our findings elucidate a tripartite circuit linking nutrients from the diet or intestinal microbiota, host lipid metabolism, and the mucosal humoral immune response.

A Longitudinal Analysis of Memory Immune Responses in Convalescent Crimean-Congo Hemorrhagic Fever Survivors in Uganda.

Evaluating the adaptive immune responses to natural infection with Crimean-Congo hemorrhagic fever (CCHF) virus (CCHFV) in human survivors is critical to the development of medical countermeasures. However, the correlates of protection are unknown. As the most prevalent tick-borne human hemorrhagic fever virus with case fatality rates of 5%-30% and worldwide distribution, there is an urgent need to fill these knowledge gaps. Here, we describe adaptive immune responses in a cohort of Ugandan CCHF survivors via serial sampling over 6 years. We demonstrate persistent antibodies after infection and cross-neutralization against various clades of authentic CCHFV, as well as potent effector function. Moreover, we show for the first time persistent, polyfunctional antigen-specific memory T-cell responses to multiple CCHFV proteins up to 9 years after infection. Together, this data provides immunological benchmarks for evaluating CCHFV medical countermeasures and information that can be leveraged toward vaccine immunogen design and viral target identification for monoclonal antibody therapies.

201.2: Patients remaining donor specific antibody (DSA) negative post transplantation have more regulated and fewer antigen specific Th-1 cell responses to mismatched donor human leucocyte antigens (HLA) versus those who develop DSA.

201.2: Patients remaining donor specific antibody (DSA) negative post transplantation have more regulated and fewer antigen specific Th-1 cell responses to mismatched donor human leucocyte antigens (HLA) versus those who develop DSA.