HLA-B27 and antigen presentation: at the crossroads between immune defense and autoimmunity

The enigma of sclera-specific autoimmunity in scleritis

Scleritis is a severe and painful ophthalmic disorder, in which a pathogenic role for collagen-directed autoimmunity was repeatedly suggested. We evaluated the presence of sclera-specific antibodies in a large cohort of patients with non-infectious scleritis. Therefore, we prospectively collected serum samples from 121 patients with non-infectious scleritis in a multicenter cohort study in the Netherlands. In addition, healthy (n = 39) and uveitis controls (n = 48) were included. Serum samples were tested for anti-native human type II collagen antibodies using a validated enzyme-linked immunosorbent assay (ELISA). Further, sclera-specific antibodies were determined using indirect immunofluorescence (IIF) on primate retinal/scleral cryosections. Lastly, human leukocyte antigen (HLA) typing was performed in 111 patients with scleritis. Anti-type II collagen antibodies were found in 13% of scleritis patients, in 10% of healthy controls and in 11% of uveitis controls (p = 0.91). A specific reaction to scleral nerve tissue on IIF was observed in 33% of patients with scleritis, which was higher than in healthy controls (11%; p = 0.01), but similar to uveitis controls (25%; p = 0.36). Reactivity to the scleral nerve tissue was significantly associated with earlier onset of scleritis (48 versus 56 years; p < 0.001), bilateral involvement (65% versus 42%; p = 0.01), and less frequent development of scleral necrosis (5% versus 22%; p = 0.02). HLA-B27 was found to be twice as prevalent in patients with scleritis (15.3%) compared to a healthy population (7.2%). In conclusion, scleral nerve autoantibody reactivity was more common in scleritis and uveitis patients in contrast to healthy controls. Further research is needed to characterize these scleral-nerve directed antibodies and assess their clinical value.

Reactive Arthritis in Children: Case Report, Narrative Review and Proposed Therapy

Reactive arthritis is an acute inflammatory aseptic arthritis that is preceded by an infectious process in genetically predisposed individuals. It has been associated with gastrointestinal or genitourinary infection. Reactive arthritis is rare in children. In this review, we present two index cases that need biologic treatment followed by a thorough review of reactive arthritis in children and adolescents with proposed treatment algorithm.

HLA-B*27 and Ankylosing Spondylitis: 50 Years of Insights and Discoveries

PURPOSE OF REVIEW

To commemorate the 50th anniversary of the groundbreaking discovery of a remarkably strong association between HLA-B*27 and ankylosing spondylitis (AS).

RECENT FINDINGS

In addition to HLA-B*27, more than 116 other recognized genetic risk variants have been identified, while epigenetic factors largely remain unexplored in this context. Among patients with AS who carry the HLA-B*27 gene, clonally expanded CD8 + T cells can be found in their bloodstream and within inflamed tissues. Moreover, the α and β chain motifs of these T-cell receptors demonstrate a distinct affinity for certain self- and microbial-derived peptides, leading to an autoimmune response that ultimately results in the onset of the disease. These distinctive peptide-binding and presentation characteristics are a hallmark of the disease-associated HLA-B*27:05 subtype but are absent in HLA-B*27:09, a subtype not associated with the disease, differing by only a single amino acid. This discovery represents a significant advancement in unraveling the 50-year-old puzzle of how HLA-B*27 contributes to the development of AS. These findings will significantly accelerate the process of identifying peptides, both self- and microbial-derived, that instigate autoimmunity. This, in return, will pave the way for the development of more accurate and effective targeted treatments. Moreover, the discovery of improved biomarkers, in conjunction with the emerging technology of electric field molecular fingerprinting, has the potential to greatly bolster early diagnosis capabilities. A very recently published groundbreak paper underscores the remarkable effectiveness of targeting and eliminating disease-causing T cells in a HLA-B*27 patients with AS. This pivotal advancement not only signifies a paradigm shift but also bolsters the potential for preventing the disease in individuals carrying high-risk genetic variants.

Antigen-specific immune reactions by expanded CD8+ T cell clones from HLA-B*27-positive patients with spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disease that is tightly linked to HLA-B*27 but the pathophysiological basis of this link is still unknown. It is discussed whether either the instability of HLA-B*27 molecules triggers predominantly innate immune reactions or yet unknown antigenic peptides presented by HLA-B*27 induce adaptive autoimmune reactions by CD8⁺ T cells. To analyze the pathogenesis of SpA, we here investigated the T cell receptor (TCR) usage and whole transcriptomes of CD8⁺ single cells from synovial fluid of HLA-B*27-positive SpA patients and HLA-B*27-negative controls. In HLA-B*27-positive patients, we confirmed preferential expression of several TCR β-chain families, found even more restricted usage of particular TCR α-chains, assigned matching TCR αβ-chain pairs with homologous CDR3-sequences, and detected identical TCR-chains in different patients. Gene expression analyses by single cell mRNAseq revealed that genes specific for the tissue resident memory phenotype, exhaustion, and apoptosis were particularly highly expressed in expanded clonotypes from HLA-B*27-positive SpA patients. Together, several independent lines of evidence argue in favor of an (auto)antigenic peptide related pathogenesis.

Association and Risk of Axial Spondyloarthritis of Scoliosis Patients: A Database Study

STUDY DESIGN

Retrospective longitudinal cohort study.

OBJECTIVE

To investigate the incidence and risk of axial spondyloarthritis (axSpA) in patients with scoliosis in Taiwan.

SUMMARY OF BACKGROUND DATA

Scoliosis and axSpA causes back pain which reduces quality of life in many patients. Both scoliosis and axSpA had attracted numerous research attention, but the association between the two was hardly known.

METHODS

In this retrospective study, the data of 25,566 patients were obtained from Taiwan's National Health Insurance Research Database. We identified patients diagnosed with scoliosis and included them in the study cohort. We included age- and sex-matched patients without scoliosis in the control cohort. The total follow-up period was 7 years. Cox proportional hazards models were used to analyze the retrieved data. Hazard ratios (HRs) and adjusted HRs were calculated.

RESULTS

The study and control cohorts included 4261 and 21,305 patients, respectively. The incidences of axSpA were 141 and 46 per 100,000 person-years in the study and control cohorts, respectively. The crude HRs and adjusted HRs for patients with scoliosis were 2.98 (95% confidence interval, 1.87-4.73; P < 0.001) and 2.78 (95% confidence interval, 1.74-4.43; P < 0.001), respectively. The prevalence of comorbidities such as chronic obstructive pulmonary disease, osteoporosis, depression, autoimmune diseases (rheumatoid arthritis and systemic lupus erythematosus), and thyroid disease was significantly higher in the study cohort.

CONCLUSION

Our findings indicate an association between scoliosis and axSpA. Additional studies should be performed to explain this phenomenon.Level of Evidence: 3.

Ankylosing spondylitis: etiology, pathogenesis, and treatments

Ankylosing spondylitis (AS), a common type of spondyloarthropathy, is a chronic inflammatory autoimmune disease that mainly affects spine joints, causing severe, chronic pain; additionally, in more advanced cases, it can cause spine fusion. Significant progress in its pathophysiology and treatment has been achieved in the last decade. Immune cells and innate cytokines have been suggested to be crucial in the pathogenesis of AS, especially human leukocyte antigen (HLA)‑B27 and the interleukin‑23/17 axis. However, the pathogenesis of AS remains unclear. The current study reviewed the etiology and pathogenesis of AS, including genome-wide association studies and cytokine pathways. This study also summarized the current pharmaceutical and surgical treatment with a discussion of future potential therapies.

Unusual Placement of an EBV Epitope into the Groove of the Ankylosing Spondylitis-Associated HLA-B27 Allele Allows CD8+ T Cell Activation

The human leukocyte antigen HLA-B27 is a strong risk factor for Ankylosing Spondylitis (AS), an immune-mediated disorder affecting axial skeleton and sacroiliac joints. Additionally, evidence exists sustaining a strong protective role for HLA-B27 in viral infections. These two aspects could stem from common molecular mechanisms. Recently, we have found that the HLA-B*2705 presents an EBV epitope (pEBNA3A-RPPIFIRRL), lacking the canonical B27 binding motif but known as immunodominant in the HLA-B7 context of presentation. Notably, 69% of B*2705 carriers, mostly patients with AS, possess B*2705-restricted, pEBNA3A-specific CD8+ T cells. Contrarily, the non-AS-associated B*2709 allele, distinguished from the B*2705 by the single His116Asp polymorphism, is unable to display this peptide and, accordingly, B*2709 healthy subjects do not unleash specific T cell responses. Herein, we investigated whether the reactivity towards pEBNA3A could be a side effect of the recognition of the natural longer peptide (pKEBNA3A) having the classical B27 consensus (KRPPIFIRRL). The stimulation of PBMC from B*2705 positive patients with AS in parallel with both pEBNA3A and pKEBNA3A did not allow to reach an unambiguous conclusion since the differences in the magnitude of the response measured as percentage of IFNγ-producing CD8+ T cells were not statistically significant. Interestingly, computational analysis suggested a structural shift of pEBNA3A as well as of pKEBNA3A into the B27 grooves, leaving the A pocket partially unfilled. To our knowledge this is the first report of a viral peptide: HLA-B27 complex recognized by TCRs in spite of a partially empty groove. This implies a rethinking of the actual B27 immunopeptidome crucial for viral immune-surveillance and autoimmunity.

Ankylosing Spondylitis: A Trade Off of HLA-B27, ERAP, and Pathogen Interconnections? Focus on Sardinia

The frequency of HLA-B27 in patients with Ankylosing Spondylitis (AS) is over 85%. There are more than 170 recognized HLA-B27 alleles but the majority of them is not sufficiently represented for genetic association studies. So far only two alleles, the HLA-B^*2706 in Asia and the HLA-B^*2709 in Sardinia, have not been found to be associated with AS. The highly homogenous genetic structure of the Sardinian population has favored the search of relevant variants for disease-association studies. Moreover, malaria, once endemic in the island, has been shown to have contributed to shape the native population genome affecting the relative allele frequency of relevant genes. In Sardinia, the prevalence of HLA-B^*2709, which differs from the strongly AS-associated B^*2705 prototype for one amino acid (His/Asp116) in the F pocket of the peptide binding groove, is around 20% of all HLA-B27 alleles. We have previously hypothesized that malaria could have contributed to the establishment of this allele in Sardinia. Based on our recent findings, in this perspective article we speculate that the Endoplasmic Reticulum Amino Peptidases, ERAP1 and 2, associated with AS and involved in antigen presentation, underwent co-selection by malaria. These genes, besides shaping the immunopeptidome of HLA-class I molecules, have other biological functions that could also be involved in the immunosurveillance against malaria.

Gastrointestinal and Hepatic Disease in Spondyloarthritis

The association of inflammatory arthritis with intestinal pathology extends back more than 100 years. This association is now supported by epidemiologic studies demonstrating an elevated prevalence of inflammatory bowel disease in spondyloarthritis and vice versa, compared with the general population. Genetic and intestinal microbiome studies have further linked these diseases. Although diabetes and nonalcoholic fatty liver disease disproportionately affect individuals with psoriatic arthritis, diseases of the esophagus, stomach, pancreas, and liver are not particularly common in spondyloarthritis. Clinicians should be aware of the differential diagnosis and the appropriate diagnostic tools available when evaluating digestive and hepatic disorders in spondyloarthritis.

The interplay between HLA-B27 and ERAP1/ERAP2 aminopeptidases: from anti-viral protection to spondyloarthritis

The human leukocyte antigen class I gene HLA-B27 is the strongest risk factor for ankylosing spondylitis (AS), a chronic inflammatory arthritic disorder. More recently, the Endoplasmic Reticulum Aminopeptidase (ERAP) 1 and 2 genes have been identified by genome wide association studies (GWAS) as additional susceptibility factors. In the ER, these aminopeptidases trim the peptides to a length suitable to fit into the groove of the major histocompatibility complex (MHC) class I molecules. It is noteworthy that an epistatic interaction between HLA-B27 and ERAP1, but not between HLA-B27 and ERAP2, has been highlighted. However, these observations suggest a paramount centrality for the HLA-B27 peptide repertoire that determines the natural B27 immunological function, i.e. the T cell antigen presentation and, as a by-product, elicits HLA-B27 aberrant behaviours: (i) the misfolding leading to ER stress responses and autophagy and (ii) the surface expression of homodimers acting as ligands for innate immune receptors. In this context, it has been observed that the HLA-B27 carriers, besides being prone to autoimmunity, display a far better surveillance to some viral infections. This review focuses on the ambivalent role of HLA-B27 in autoimmunity and viral protection correlating its functions to the quantitative and qualitative effects of ERAP1 and ERAP2 polymorphisms on their enzymatic activity.

Human Leukocyte Antigen (HLA) and Immune Regulation: How Do Classical and Non-Classical HLA Alleles Modulate Immune Response to Human Immunodeficiency Virus and Hepatitis C Virus Infections?

The genetic factors associated with susceptibility or resistance to viral infections are likely to involve a sophisticated array of immune response. These genetic elements may modulate other biological factors that account for significant influence on the gene expression and/or protein function in the host. Among them, the role of the major histocompatibility complex in viral pathogenesis in particular human immunodeficiency virus (HIV) and hepatitis C virus (HCV), is very well documented. We, recently, added a novel insight into the field by identifying the molecular mechanism associated with the protective role of human leukocyte antigen (HLA)-B27/B57 CD8⁺ T cells in the context of HIV-1 infection and why these alleles act as a double-edged sword protecting against viral infections but predisposing the host to autoimmune diseases. The focus of this review will be reexamining the role of classical and non-classical HLA alleles, including class Ia (HLA-A, -B, -C), class Ib (HLA-E, -F, -G, -H), and class II (HLA-DR, -DQ, -DM, and -DP) in immune regulation and viral pathogenesis (e.g., HIV and HCV). To our knowledge, this is the very first review of its kind to comprehensively analyze the role of these molecules in immune regulation associated with chronic viral infections.

Identification of the core regulators of the HLA I-peptide binding process

During the display of peptide/human leukocyte antigen (HLA) -I complex for further immune recognition, the cleaved and transported antigenic peptides have to bind to HLA-I protein and the binding affinity between peptide epitopes and HLA proteins directly influences the immune recognition ability in human beings. Key factors affecting the binding affinity during the generation, selection and presentation processes of HLA-I complex have not yet been fully discovered. In this study, a new method describing the HLA class I-peptide interactions was proposed. Three hundred and forty features of HLA I proteins and peptide sequences were utilized for analysis by four candidate algorithms, screening the optimal classifier. Features derived from the optimal classifier were further selected and systematically analyzed, revealing the core regulators. The results validated the hypothesis that features of HLA I proteins and related peptides simultaneously affect the binding process, though with discrepant redundancy. Besides, the high relative ratio (16/20) of the amino acid composition features suggests the unique role of sequence signatures for the binding processes. Integrating biological, evolutionary and chemical features of both HLA I molecules and peptides, this study may provide a new perspective of the underlying mechanisms of HLA I-mediated immune reactions.

Coexistence of Ankylosing Spondylitis and Neurofibromatosis Type 1

Ankylosing spondylitis (AS) is a systemic disease primarily characterized by the inflammation of sacroiliac joints and axial skeleton. Neurofibromatosis type 1 (NF1) is a multisystem genetic disease which is characterized by cutaneous findings, most importantly café-au-lait spots and axillary freckling, by skeletal dysplasia, and by the growth of both benign and malignant nervous system neoplasms, most notably benign neurofibromas. In this case report, we present a 43-year-old male with AS and NF1.

A computational docking study on the pH dependence of peptide binding to HLA-B27 sub-types differentially associated with ankylosing spondylitis

A single amino acid difference (Asp116His), having a key role in a pathogenesis pathway, distinguishes HLA-B*27:05 and HLA-B*27:09 sub-types as associated and non-associated with ankylosing spondylitis, respectively. In this study, molecular docking simulations were carried out with the aim of comprehending the differences in the binding behavior of both alleles at varying pH conditions. A library of modeled peptides was formed upon single point mutations aiming to address the effect of 20 naturally occurring amino acids at the binding core peptide positions. For both alleles, computational docking was applied using Autodock 4.2. Obtained free energies of binding (FEB) were compared within the peptide library and between the alleles at varying pH conditions. The amino acid preferences of each position were studied enlightening the role of each on binding. The preferred amino acids for each position of pVIPR were found to be harmonious with experimental studies. Our results indicate that, as the pH is lowered, the capacity of HLA-B*27:05 to bind peptides in the library is largely lost. Hydrogen bonding analysis suggests that the interaction between the main anchor positions of pVIPR and their respective binding pocket residues are affected from the pH the most, causing an overall shift in the FEB profiles.

ERAP1 reduces accumulation of aberrant and disulfide-linked forms of HLA-B27 on the cell surface

OBJECTIVE

Endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) variants contribute to the risk of ankylosing spondylitis in HLA-B27 positive individuals, implying a disease-related interaction between these gene products. The aim of this study was to determine whether reduced ERAP1 expression would alter the cell surface expression of HLA-B27 and the formation of aberrant disulfide-linked forms that have been implicated in the pathogenesis of spondyloarthritis.

METHODS

ERAP1 expression was knocked down in monocytic U937 cells expressing HLA-B27 and endogenous HLA class I. The effect of ERAP1 knockdown on the accumulation HLA-B alleles (B18, B51, and B27) was assessed using immunoprecipitation, isoelectric focusing, and immunoblotting, as well as flow cytometry with antibodies specific for different forms of HLA-B27. Cell surface expression of aberrant disulfide-linked HLA-B27 dimers was assessed by immunoprecipitation and electrophoresis on non-reducing polyacrylamide gels.

RESULTS

ERAP1 knockdown increased the accumulation of HLA-B27 on the cell surface including disulfide-linked dimers, but had no effect on levels of HLA-B18 or -B51. Antibodies with unique specificity for HLA-B27 confirmed increased cell surface expression of complexes shown previously to contain long peptides. IFN-γ treatment resulted in striking increases in the expression of disulfide-linked HLA-B27 heavy chains, even in cells with normal ERAP1 expression.

CONCLUSIONS

Our results suggest that normal levels of ERAP1 reduce the accumulation of aberrant and disulfide-linked forms of HLA-B27 in monocytes, and thus help to maintain the integrity of cell surface HLA-B27 complexes.

The Ankylosing Spondylitis-associated HLA-B*2705 presents a B*0702-restricted EBV epitope and sustains the clonal amplification of cytotoxic T cells in patients

HLA-B*27 is strongly associated with an inflammatory autoimmune disorder, the Ankylosing Spondylitis (AS) and plays a protective role in viral infections. The two aspects might be linked. In this work, we compared in B*2705/B*07 positive patients with AS, the CD8+ T cell responses to two immunodominant EBV-derived epitopes restricted for either the HLA-B*27 (pEBNA3C) or the HLA-B*07 (pEBNA3A). We have unexpectedly found that the HLA-B*07-restricted EBNA3A peptide is presented by both the B*0702 and the B*2705 but not by the non AS-associated B*2709, that differs from the AS-associated B*2705 for a single amino acid in the peptide-binding groove (His116Asp). We then analysed 38 B*2705-positive/B*07-negative (31 AS-patients and 7 healthy donors) and 8 B*2709-positive/B*07-negative subjects. EBNA3A-specific CD8+ T lymphocytes were present in 55.3% of the HLA-B*2705 but in none of the B*2709 donors (p=0.0049). TCR β-chain analysis identified common TCRBV and TCRBJ gene segments and shared CDR3β sequences in pEBNA3A-responsive CTLs of B*2705 carriers, suggesting the existence of a shared TCR repertoire for recognition of the uncanonical B*2705/pEBNA3A complex. These data highlight the plasticity of the AS-associated HLA-B*2705, which presents peptides with suboptimal binding motifs, possibly contributing both to its enhanced capacity to protect against pathogens and to predispose to autoimmunity.

Enhanced Direct Major Histocompatibility Complex Class I Self-Antigen Presentation Induced by Chlamydia Infection

The direct major histocompatibility complex (MHC) class I antigen presentation pathway ensures intracellular peptides are displayed at the cellular surface for recognition of infected or transformed cells by CD8(+) cytotoxic T lymphocytes. Chlamydia spp. are obligate intracellular bacteria and, as such, should be targeted by CD8(+) T cells. It is likely that Chlamydia spp. have evolved mechanisms to avoid the CD8(+) killer T cell responses by interfering with MHC class I antigen presentation. Using a model system of self-peptide presentation which allows for posttranslational control of the model protein's stability, we tested the ability of various Chlamydia species to alter direct MHC class I antigen presentation. Infection of the JY lymphoblastoid cell line limited the accumulation of a model host protein and increased presentation of the model-protein-derived peptides. Enhanced self-peptide presentation was detected only when presentation was restricted to defective ribosomal products, or DRiPs, and total MHC class I levels remained unaltered. Skewed antigen presentation was dependent on a bacterial synthesized component, as evidenced by reversal of the observed phenotype upon preventing bacterial transcription, translation, and the inhibition of bacterial lipooligosaccharide synthesis. These data suggest that Chlamydia spp. have evolved to alter the host antigen presentation machinery to favor presentation of defective and rapidly degraded forms of self-antigen, possibly as a mechanism to diminish the presentation of peptides derived from bacterial proteins.

Peptide handling by HLA-B27 subtypes influences their biological behavior, association with ankylosing spondylitis and susceptibility to endoplasmic reticulum aminopeptidase 1 (ERAP1)

HLA-B27 is strongly associated with ankylosing spondylitis (AS). We analyzed the relationship between structure, peptide specificity, folding, and stability of the seven major HLA-B27 subtypes to determine the role of their constitutive peptidomes in the pathogenicity of this molecule. Identification of large numbers of ligands allowed us to define the differences among subtype-bound peptidomes and to elucidate the peptide features associated with AS and molecular stability. The peptides identified only in AS-associated or high thermostability subtypes with identical A and B pockets were longer and had bulkier and more diverse C-terminal residues than those found only among non-AS-associated/lower-thermostability subtypes. Peptides sequenced from all AS-associated subtypes and not from non-AS-associated ones, thus strictly correlating with disease, were very rare. Residue 116 was critical in determining peptide binding, thermodynamic properties, and folding, thus emerging as a key feature that unified HLA-B27 biology. HLA-B27 ligands were better suited to TAP transport than their N-terminal precursors, and AS-associated subtype ligands were better than those from non-AS-associated subtypes, suggesting a particular capacity of AS-associated subtypes to bind epitopes directly produced in the cytosol. Peptides identified only from AS-associated/high-thermostability subtypes showed a higher frequency of ERAP1-resistant N-terminal residues than ligands found only in non-AS-associated/low-thermostability subtypes, reflecting a more pronounced effect of ERAP1 on the former group. Our results reveal the basis for the relationship between peptide specificity and other features of HLA-B27, provide a unified view of HLA-B27 biology and pathogenicity, and suggest a larger influence of ERAP1 polymorphism on AS-associated than non-AS-associated subtypes.

Genetics, environment, and gene-environment interactions in the development of systemic rheumatic diseases

Rheumatic diseases offer distinct challenges to researchers because of heterogeneity in disease phenotypes, low disease incidence, and geographic variation in genetic and environmental factors. Emerging research areas, including epigenetics, metabolomics, and the microbiome, may provide additional links between genetic and environmental risk factors in the pathogenesis of rheumatic disease. This article reviews the methods used to establish genetic and environmental risk factors and studies gene-environment interactions in rheumatic diseases, and provides specific examples of successes and challenges in identifying gene-environment interactions in rheumatoid arthritis, systemic lupus erythematosus, and ankylosing spondylitis. Emerging research strategies and future challenges are discussed.

Reprint of "genetics of autoimmunity: an update"

The advent of genome-wide association studies (GWAS) has produced tremendous insights into the genetics of immune-mediated diseases allowing to identify hundreds of associated variants, some of which disease-specific and some others shared by groups of diseases. However, each variant usually accounts for a small genetic risk and all together they explain a relatively small portion of heritability for each disease. In addition, many of the associated variants map in regions of still undisclosed functions. This opens up to a new era of studies in search of the "missing heritability" which might partially be explained by gene-gene interactions and/or additive effects impacting on biochemical pathways relevant for the disease pathogenesis. The introduction of the immunochip analysis that allows to analyze thousands of patients for variations more strictly correlated with the immune/inflammatory functions is now allowing to single out relevant pathways shared by different diseases. Finally, great expectations are brought about from the studies on the effects that epigenetic modifications can have on the tuning of the expression of single allele/s in myeloid cells as well as in target tissues. Some of these topics have been discussed at the 15th International Congress of Immunology.

HLA genotypes and rubella vaccine immune response: additional evidence

Recent population-based studies have demonstrated the genetic heritability of rubella vaccine response and assessed that the HLA system may explain about 20% of the inter-individual variance in humoral immune response to this vaccine. Our earlier studies compared HLA allelic associations with rubella vaccine-specific antibodies between two smaller cohorts of healthy Rochester, MN, children (346 and 396 subjects) after two doses of rubella-containing vaccine. This study found that specific HLA alleles were consistently associated with rubella-specific antibody titers (B*27:05, DPA1*02:01, and DPB1*04:01 alleles). The current study examined HLA associations in an independent larger cohort of 1012 healthy San Diego, CA, subjects (age 19-40 years) after rubella vaccine in order to replicate our previous findings in the Rochester subjects. Two HLA associations of comparable magnitudes were consistently observed between B*27:05 (median NT50 Rochester cohort 48.9, p=0.067; San Diego cohort 54.8, p=0.047) and DPB1*04:01 (median NT50 Rochester cohort 61.6, p<0.001; San Diego cohort 70.8, p=0.084) alleles and rubella virus-neutralizing antibody titers. Additional HLA alleles resulted in consistent effects on IL-6 production in both cohorts, but did not meet criteria for statistical significance. Our data suggest these HLA alleles play a role in rubella vaccine-induced immunity and provide the basis for future studies that may explain the mechanism(s) by which these HLA polymorphisms affect immune responses to rubella vaccine.

Genetics of autoimmunity: an update

The advent of genome-wide association studies (GWAS) has produced tremendous insights into the genetics of immune-mediated diseases allowing to identify hundreds of associated variants, some of which disease-specific and some others shared by groups of diseases. However, each variant usually accounts for a small genetic risk and all together they explain a relatively small portion of heritability for each disease. In addition, many of the associated variants map in regions of still undisclosed functions. This opens up to a new era of studies in search of the "missing heritability" which might partially be explained by gene-gene interactions and/or additive effects impacting on biochemical pathways relevant for the disease pathogenesis. The introduction of the immunochip analysis that allows to analyze thousands of patients for variations more strictly correlated with the immune/inflammatory functions is now allowing to single out relevant pathways shared by different diseases. Finally, great expectations are brought about from the studies on the effects that epigenetic modifications can have on the tuning of the expression of single allele/s in myeloid cells as well as in target tissues. Some of these topics have been discussed at the 15th International Congress of Immunology.

Chemical biology of antigen presentation by MHC molecules

MHC class I and MHC class II molecules present peptides to the immune system to drive proper T cell responses. Pharmacological modulation of T-cell responses can offer treatment options for a range of immune-related diseases. Pharmacological downregulation of MHC molecules may find application in treatment of auto-immunity and transplantation rejection while pharmacological activation of antigen presentation would support immune responses to infection and cancer. Since the cell biology of MHC class I and MHC class II antigen presentation is understood in great detail, many potential targets for manipulation have been defined over the years. Here, we discuss how antigen presentation by MHC molecules can be modulated by pharmacological agents and how chemistry can further support the study of antigen presentation in general. The chemical biology of antigen presentation by MHC molecules shows surprising options for immune modulation and the development of future therapies.