The Peptide Repertoire of HLA-B27 may include Ligands with Lysine at P2 Anchor Position.

The HLA-B*27 peptidome has drawn significant attention due to the genetic association between some of the HLA-B*27 alleles and the inflammatory rheumatic disease ankylosing spondylitis (AS), for which a comprehensive biological explanation is still lacking. This study aims to expand the known limits of the HLA-B*27 peptidome to facilitate selection and testing of new peptides, possibly involved in the disease. The HLA peptidomes of HeLa and C1R cell lines stably transfected with the AS-associated HLA-B*27:05 allele, the nonassociated HLA-B*27:09 allele, or their cysteine 67 to serine mutants (C67S), are analyzed on a very large scale. In addition, the peptidomes of HLA-B*27:05 and HLA-B*27:05-C67S are analyzed from the spleens of rats transgenic for these alleles. The results indicate that C67S mutation increases the percentage of peptides with glutamine or lysine at their P2 position (P2-Lys), in both HLA-B*27:05 and HLA-B*27:09. Furthermore, a small fraction of HLA-B*27 peptides contains lysine at their second position (P2), in addition to the more commonly found peptides with arginine (P2-Arg) or the less common glutamine (P2-Gln) located at this anchor position. Overall these data indicate that peptides with P2-Lys should be considered as real ligands of HLA-B*27 molecules and taken into account while looking for putative peptides implicated in the AS.

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 ß-chain analysis identified common TCRBV and TCRBJ gene segments and shared CDR3ß 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.

Sensitization to nsLTP: A Retrospective Study in An Italian Pediatric Population over the Last Decade.

Background: Food allergy is common in the Mediterranean, especially concerning lipid transfer proteins (LTPs) allergy. LTPs are widespread plant food allergens in fruits, vegetables, nuts, pollen, and latex. Also, LTPs are prevalent food allergens in the Mediterranean area. They can sensitize via the gastrointestinal tract and cause a wide range of conditions: from mild reactions, such as oral allergy syndrome, to severe reactions, such as anaphylaxis. LTP allergy in the adult population is well described in the literature, concerning both the prevalence and clinical characteristics. However, there is poor knowledge about its prevalence and clinical manifestation in children living in the Mediterranean. Materials and Methods: This study, including 800 children aged from 1 to 18 years, investigated the prevalence of 8 different molecules of nonspecific LTP over time in an Italian pediatric population visited over the last 11 years. Results: About 52% of the test population was sensitized to at least one LTP molecule. For all the LTPs analyzed, sensitization increased over time. In particular, using the years 2010 through 2020 as a comparison, the major increases were observed for the LTPs of the English walnut Jug r 3, the peanut Ara h 9, and the plane tree Pla a 3 (about 50%); the increase of the LTP of the Hazelnut Cor a 8 was about 36%, and that of the LTP of the artemisia Art v 3 was approximately 30%. Conclusions: The latest evidence in the literature indicates an increase in food allergy prevalence in the general population, including children. Therefore, the present survey represents an interesting perspective about the pediatric population of the Mediterranean area, exploring the trend of LTP allergy.

An allelic variant in the intergenic region between ERAP1 and ERAP2 correlates with an inverse expression of the two genes.

The Endoplasmatic Reticulum Aminopeptidases ERAP1 and ERAP2 are implicated in a variety of immune and non-immune functions. Most studies however have focused on their role in shaping the HLA class I peptidome by trimming peptides to the optimal size. Genome Wide Association Studies highlighted non-synonymous polymorphisms in their coding regions as associated with several immune mediated diseases. The two genes lie contiguous and oppositely oriented on the 5q15 chromosomal region. Very little is known about the transcriptional regulation and the quantitative variations of these enzymes. Here, we correlated the level of transcripts and proteins of the two aminopeptidases in B-lymphoblastoid cell lines from 44 donors harbouring allelic variants in the intergenic region between ERAP1 and ERAP2. We found that the presence of a G instead of an A at SNP rs75862629 in the ERAP2 gene promoter strongly influences the expression of the two ERAPs with a down-modulation of ERAP2 coupled with a significant higher expression of ERAP1. We therefore show here for the first time a coordinated quantitative regulation of the two ERAP genes, which can be relevant for the setting of specific therapeutic approaches.