ABSTRACT
An efficient vaccine against human immunodeficiency virus (HIV) must induce good cellular immune responses. To do this, it must be processed and presented by dendritic cells, which are required for primary T-lymphocyte stimulation. We have previously shown that a model lipopeptide containing a short epitopic peptide from HIV-1 was endocytosed and presented in association with major histocompatibility complex class I molecules by human dendritic cells to specific CD8+ T lymphocytes, but the cross-presentation pathway needed to be precisely determined. We have studied a longer lipopeptide (Pol461-484) and another lipopeptide (Nef66-97) currently being used in vaccine trials. Like the shorter lipopeptide, the rhodamine-labeled Pol461-484 lipopeptide was internalized by endocytosis, as assessed by confocal microscopy. The lipopeptides were processed by dendritic cells and presented to CD8+ T cells specific for the HLA-A*0201-restricted Pol476-484 and the HLA-A*0301-restricted Nef73-82 epitope, respectively. Presentation of both lipopeptides was inhibited by brefeldin A. Presentation of the Pol lipopeptide was inhibited by epoxomycin, a proteasome-specific inhibitor, but not by monensin. This shows that it gained access to the cytosol to be digested by the proteasome. In contrast, presentation of the Nef lipopeptide was not inhibited by epoxomycin but was inhibited by monensin, a classical inhibitor of acid-dependent endosomal enzyme activity, indicating an endocytic processing pathway yielding to major histocompatibility complex class I-restricted presentation. Therefore, the two lipopeptides followed different cross-presentation pathways, both resulting in efficient presentation to CD8+ T lymphocytes.
Major histocompatibility complex class II DR alleles DRB1*1501 and those encoding HLA-DR13 are preferentially associated with a diminution in maternally transmitted human immunodeficiency virus 1 infection in different ethnic groups: determination by an automated sequence-based typing method.