Gag protein epitopes recognized by CD4(+) T-helper lymphocytes from equineinfectious anemia virus-infected carrier horses

Antigen-specific T-helper (Th) lymphocytes are critical for the development of antiviral humoral responses and the expansion of cytotoxic T lymphocyte s (CTL), Identification of relevant Th lymphocyte epitopes remains an impor tant step in the development of an efficacious subunit peptide vaccine agai nst equine infectious anemia virus (EIAV), a naturally occurring lentivirus of horses. This study describes Th lymphocyte reactivity in EIAV carrier h orses to two proteins, p26 and p15, encoded by the relatively conserved EIA V gag gene, Using partially overlapping peptides, multideterminant and poss ibly promiscuous epitopes were identified within p26, One peptide was ident ified which reacted,vith peripheral blood mononuclear cells (PBMC) from all five EIAV-infected horses, and three other peptides were identified which reacted with PBMC from four of five EIAV-infected horses. Four additional p eptides containing both CTL and Th lymphocyte epitopes were also identified . Multiple epitopes were recognized in a region corresponding to the major homology region of the human immunodeficiency virus, a region with signific ant sequence similarity to other lentiviruses including simian immunodefici ency virus, puma lentivirus, feline immunodeficiency virus, Jembrana diseas e virus, visna virus, and caprine arthritis encephalitis virus. PBMC reacti vity to p15 peptides from EIAV carrier horses also occurred. Multiple p15 p eptides were shown to be reactive, but not all infected horses had Th lymph ocytes recognizing p15 epitopes, The identification of peptides reactive wi th PBMC from outbred horses, some of which encoded both CTL and Th lymphocy te epitopes, should contribute to the design of synthetic peptide or recomb inant vector vaccines for EIAV.