Elucidation of the HLA class I antigen-presenting pathway in P. vivax infected reticulocytes

Background: Malaria is one of the most prevalent parasitic diseases in the world. Plasmodium vivax, the major species of malaria-causing parasite in Brazil, exclusively infects reticulocytes (retics) in the peripheral blood. This cell differs from erythrocyte due the presence of RNA and high capacity of protein expression. Results from our research group shown evidences that retic could acts as an antigen-presenting cell during malaria infection, leading to CD8+T cell activation and being therefore potential targets for cytotoxic effector cells. The aim of the present work is to demonstrate the presence of proteins involved in the HLA class I antigen presenting pathway in P. vivaxinfected and health donor (HD) retics, to determine P. vivax peptides that can be presented to CD8+ T cells and thus to identify new antigen candidates to be employed in vaccines. Materials and Methods: To evaluate the expression profile of proteins involved in antigen presented, retics were purified from peripheral blood from P. vivaxinfected patients and HD enrolled in this study at CEPEM in Porto Velho, Rondônia.The samples were resolved for western blot evaluation against ERAP1, Tapasin, TAP1 and LMP2 proteins. Bioinformatics analyses of public proteome and transcriptome data from HD and P. vivax-infected retics were performed aiming at establish the presence of the proteins involved in antigen presentation pathway. To determine which peptides may be presented, a search was made from P. vivax proteins that display motifs related to protein export from parasitoforus vacuole to host cell cytoplasm and proteasome cleavage sites. Results and Conclusions: Through the western blot were identified ERAP1 and TAP1 proteins in infected retics; Tapasin and LMP2 were identified in HD retics. In silico were found various proteins involved in the antigen presenting pathway, like proteasome subunits, HLA-ABC, ERAP1, trafficking-related proteins, beyond the presence of stimulatory molecules and absence of inhibitory molecules to T cell. Among P. vivax proteins were found 1104 proteins containing export motifs and proteasome cleavage sites. Thus, we have demonstrated the presence of proteins involved in HLA-I presenting pathway being an important clue to conclude de capacity of retics to present P. vivax antigens.