HLA-DR peptide inhibits HIV-induced syncytia

The infectivity of the human immunodeficiency virus (HIV) is related to the structure of its envelope protein, gp160, which is responsible for viral entry. We considered the possibility that a structural homology between gp160 and major histocompatibility complex (MHC) molecules might be associated with the extraordinary affinity that gp120 has for its receptor, CD4. Amino acid sequence comparisons revealed five regions of structural similarity between the HLA-DRβ molecule and gp160. The DR2β synthetic peptides containing these regions were examined for their ability to block HIV-induced syncytia formation using a ⁵¹Cr release assay. The peptide β141-155 inhibited the formation of syncytia whereas the other four DRβ peptides with gp160 similarity did not. Our results indicate that this region in gp120, which is similar to an HLA-DR region, is crucial to T cell-gp120 interactions, and should be considered in the design of future vaccines.