Complement opsonization of HIV-1 results in a different intracellular processing pattern and efficiency leading to an enhanced MHC I presentation by dendritic cells

The antigen processing and presentation processes occurring in dendritic cells (DCs) required for induction of HIV-1 specific T cell responses, which are essential for controlling the viral infection in vivo. The initial interactions of DCs with free HIV-1 (FHIV), or complement opsonized HIV-1 (C-HIV) might influence the routing and nature of pathways used for MHC class I and II restricted presentation. We have examined FHIV, C-HIV, and complement and antibody opsonized HIV-1 (C-IgG-HIV) effects on immature DCs (IDCs) and mature DCs (MDCs) antigen proteolysis, MHC class I and II antigen presentation, and the role of endocytic receptors in presentation of antigens derived from HIV-1. We found that opsonized virions promoted MHC class I presentation by both IDCs and MDCs compared to F-HIV. Indicative of that complement opsonization routes more virions towards the MHC class I presentation pathway. We found that blocking macrophage mannose receptor (MMR) rerouted the HIV-1 to a path leading to higher levels of MHC class I and II presentation. Furthermore, the blocking of β7-integrin also gave an enhanced MHC class I and II presentation by both IDCs and MDCs, whereas the block of αMβ2 integrins, i.e. complement receptor 3 (CR3), decreased the MHC class I and II presentation. In addition, we found that IDCs and MDCs proteolytic activities were modulated by the HIV-1 exposure, for example C-HIV induced an increased proteasome activity in IDCs. Taken together, these findings indicated that endocytic receptors, such as MMR, CR3, and β7 integrin, can promote or disfavor antigen presentation by routing HIV-1 into different endosomal compartments with distinct properties and efficiencies for degradation of viral antigens and MHC class I and II presentation and that HIV-1 affects the antigen processing machineries.