Selecting peptides to optimize Th1 responses to an equine lentivirus using HLA-DR binding motifs and defined HIV-1 Th peptides.

Three moderately to broadly recognized equine infectious anemia virus (EIAV) peptides that contained helper T-lymphocyte (Th) 1 epitopes were previously identified. Although lipopeptide immunization was only weakly immunostimulatory in a preliminary study, as measured by T-lymphocyte proliferation responses, it was of interest to define additional broadly recognized Th1 epitopes to include in future immunization trials. Using broadly cross-reactive and conserved Th epitopes known in the related human immunodeficiency virus-1 (HIV-1) and binding motifs defined in human leukocyte antigen DR molecules as guides, this work identified three new peptides containing Th1 epitopes recognized by 60-75% of EIAV infected horses. The observed similarity across species of major histocompatibility complex (MHC) class II binding motifs and the conservation of Th peptides between related viruses should allow easier targeting of Th epitope regions in less well characterized pathogens and/or in species whose MHC class II molecules are poorly defined.