P24.20 LB
Background: Epitopes displayed by MHC-I and MHC-II result from the intracellular degradation of antigens by multiple proteases and peptidases located in various subcellular compartments. We and others previously showed that due to structural homologies HIV protease-inhibitors (PIs) used in antiretroviral therapies (ART) affect proteasome activities in PBMC. Addition peptidases and several intracellular processing pathways are required for the complete production of MHC-I and MHC-II epitopes but the effect of ART on these pathways is not known.
Methods: Eight cellular peptidase activities were assessed in PBMCs, CD4 T cells, dendritic cells and macrophages treated with seven HIV PIs, NRTIs or NNRTIs. The impact on epitope presentation was measured by T cell killing assay. Using in vitro degradation of proteins in subcellular compartments of primary cells and mass spectrometry analysis we followed protein degradation into epitopes. Through computational analysis of degradation products we identified alterations in cleavage sites of antigenic proteins.
Results: HIV PI-induced alterations of cellular peptidase activities were variable according to PI, cell types and peptidases. PIs altered different steps of antigen processing: degradation patterns, amount and intracellular stability of epitopes. They affected MHC-I and MHC-II epitope production. Altered degradation patterns led to increased or decreased frequency of cleavage sites observed in control conditions and appearance of new cleavage sites, leading to the production of putative new epitopes and modified production of known epitopes. Accordingly HIV PIs increased or decreased recognition of HIV-infected cells by CD8 T cells.
Conclusions: Antiretroviral therapies including HIV PIs alter cellular peptidase functions in a sequence-dependent manner. This may lead to a diversification of pathogen-derived epitopes and possibly of immune responses against residual HIV or co-infecting pathogens in HIV-infected persons.
