Avaliação de padrões peptídicos imunodominantes do vírus da hepatite C restritos ao HLA do tipo I

Abstract

Hepatitis C is the name given to the Hepacivirus hominis (HCV) disease, representing a major global health problem due to high morbidity and mortality rates, as HCV infection is responsible for causing severe liver changes, including fibrosis, cirrhosis, and hepatocellular carcinoma. HCV transmission is associated with direct contact with contaminated blood, and there is an estimative that more than 71 million people are chronically infected with the virus. Currently, there are no approved vaccines against hepatitis and even though direct antiviral agents (DAAs) therapies are highly effective, limitations such as the possibility of reinfection and and very high price treatment remain to be of concern. During a viral infection, the process of peptide presentation by MHC class I to CD8+ T lymphocytes is known to be essential for triggering an effective antiviral response, relevant to the improved development of HCV vaccine prototypes. This project aimed to present an overview of HCV-derived immunodominant epitopes restricted to HLA-A*02:01 using in silico and in vitro tools. For in silico studies, 59 polyprotein sequences from 7 genotypes of the virus were obtained from NCBI nucleotide and used for peptide prediction in NetCTL 2.0 software. About 2700 peptides with a combined score ≥ 0.75 were considered with potential to activate CD8+ T cells, identified and maintained for in silico functional analysis. In addition, physicochemical properties, and the capacity of induction of cytokines of the Th1 and/or Th2 axes of the cellular immune response by these peptides were also analyzed. Such analyses indicated a clear tendency to induce the regulatory cytokine IL-4 when compared to IFN-γ. For in vitro evaluation of peptide-MHC-I affinity, a peptide microarray system was performed using the peptides derived from the 7 HCV genotypes and a recombinant HLA-A*02:01 molecule. This strategy allowed the screening of immunodominant reactive amino acid sequences, and 615 peptides reactive to HLA-A*02:01 were observed in vitro. Finally, the results obtained in silico and in vitro allowed the identification of peptides with high reactivity to HLA-A*02:01, observing a predominance of reactive sequences in the regions of the p7, NS2 and NS5B proteins. In addition, the amino acid patterns observed in the reactive peptides has demonstrated the prevalence of leucine and tryptophan residues, highlighting the importance of these residues for the binding of the epitope to the TCR and, consequently, for the activation of CD8+ T lymphocytes. Overall, the HCV-derived and HLA-A2*02:01-restricted peptide patterns observed in this work provide important information for the development of a multi-epitope vaccine effective against multiple HCV genotypes.