Endosomal compartment: Also a dock for MHC class I peptide loading

The relevance of HLA class II genes in JAK2 V617F-positive myeloproliferative neoplasms

In the present study we analyzed the relevance of HLA class II in JAK2 V617F-positive (JAK2 V617F+) myeloproliferative neoplasms (MPNs) focusing on genotype diversity, associations with specific alleles and haplotypes and the level of gene expression. One hundred and thirty-nine JAK2 V617F+ MPN patients and 1083 healthy controls, typed by Next generation sequencing (NGS) were included in the study. Multivariate generalized linear models with age as a covariate were applied for analysis of HLA-II allele and haplotype associations. Publicly available gene expression datasets were used to analyze HLA-II pathway genes expression in CD34+ stem cells (SCs) from MPN patients and healthy controls. We did not observe differences in HLA evolutionary divergence (HED) between JAK2 V617F+ MPNs and healthy controls. Two alleles: HLA-DPB1*03:01, DQB1*04:02 and 4 haplotypes: DPB1*02:01-DQA1*05:05-DQB1*03:01-DRB1*11:01, DPB1*04:02-DQA1*05:05-DQB1*03:01-DRB1*11:03, DPB1*02:01-DQA1*01:04-DQB1*05:03-DRB1*14:04, and DPB1*04:01-DQA1*03:01-DQB1*03:02-DRB1*04:01 had significantly lower frequency in MPN patients compared to controls. Additionally, we observed HLA-II alleles and haplotypes with statistically higher frequencies in JAK2 V617F+ patients. Differential gene expression analysis showed down-regulation of HLA-DRB1, -DRA, -DMA, -DMB, -DOA,-DRB4, CIITA, and CD74 genes in JAK2 V617F+ MPN CD34+ SCs as compared to normal CD34 + SCs. In conclusion, this study provides evidence for the pleiotropic effects of HLA-II genes in JAK2 V617F-driven MPNs.

Development of a Molecular Adjuvant to Enhance Antigen-Specific CD8+ T Cell Responses

Despite promising progress in malaria vaccine development, an efficacious subunit vaccine against P. falciparum remains to be licensed and deployed. This study aimed to improve on the immunogenicity of the leading liver-stage vaccine candidate (ChAd63-MVA ME-TRAP), known to confer protection by eliciting high levels of antigen-specific CD8⁺ T cells. We previously showed fusion of ME-TRAP to the human MHC class II invariant chain (Ii) could enhance CD8⁺ T cell responses in non-human primates, but did not progress to clinical testing due to potential risk of auto-immunity by vaccination of humans with a self-antigen. Initial immunogenicity analyses of ME-TRAP fused to subdomains of the Ii showed that the Ii transmembrane domain alone can enhance CD8⁺ T cell responses. Subsequently, truncated Ii sequences with low homology to human Ii were developed and shown to enhance CD8⁺ T cell responses. By systematically mutating the TM domain sequence, multimerization of the Ii chain was shown to be important for immune enhancement. We subsequently identified several proteins from a variety of microbial pathogens with similar characteristics, that also enhance the CD8⁺ T cell response and could therefore be used in viral vector vaccines when potent cell mediated immunity is required.

HLA class II antigen-processing pathway in tumors: Molecular defects and clinical relevance

The human leukocyte antigen (HLA) class II antigen-processing machinery (APM) presents to cognate CD4⁺ T-cells antigenic peptides mainly generated from exogeneous proteins in the endocytic compartment. These CD4⁺ T cells exert helper function, but may also act as effector cells, thereby recognizing HLA class II antigen-expressing tumor cells. Thus, HLA class II antigen expression by tumor cells influences the tumor antigen (TA)-specific immune responses and, depending on the cancer type, the clinical course of the disease. Many types of human cancers express HLA class II antigens, although with marked differences in their frequency. Some types of cancer lack HLA class II antigen expression, which could be due to structural defects or deregulation affecting different components of the complex HLA class II APM and/or from lack of cytokine(s) in the tumor microenvironment. In this review, we have summarized the information about HLA class II antigen distribution in normal tissues, the structural organization of the HLA class II APM, their expression and regulation in malignant cells, the defects, which have been identified in malignant cells, and their functional and clinical relevance.

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.