FREQUENCY OF MEMORY CYTOTOXIC T-LYMPHOCYTES TO EQUINE INFECTIOUS-ANEMIA VIRUS PROTEINS IN BLOOD FROM CARRIER HORSES

Horses with equine infectious anemia virus (EIAV) have episodes of vir emia and disease; however, most eventually become inapparent carriers. A possible mechanism of control is cytotoxic T lymphocytes (CTL). To evaluate CTL in inapparent carriers with low viral loads, peripheral b lood mononuclear cells (PBMC) were stimulated in vitro with autologous EIAV-infected PBMC and human IL-2 to detect memory CTL (CTLm). In ini tial studies, three carriers had CTLm and one of these had low-level e ffector CTL (CTLe). The CTLm were restricted by equine lymphocyte allo antigen-A (ELA-A) locus encoded MHC class I molecules on autologous eq uine kidney (EK) target cells. In addition, EK cells did not express M HC class II molecules. The CTLm frequency in PBMC from five inapparent carriers infected for 22 to 50 months was determined by limiting dilu tion analysis. PBMC were diluted, stimulated, and tested on EK cell ta rgets infected with EIAV and recombinant vaccinia viruses expressing E IAV Env or Gag/Pr proteins. All five carriers had CTLm to EIAV-infecte d targets, while four had CTLm to targets expressing Env and four had CTLm to targets expressing Gag/Pr proteins. The CTLm frequency range w as 60 to 468 per 10(6) PBMC to EIAV-infected targets, 4 to 286 to Env- expressing targets, and 25 to 190 to Gag/Pr-expressing targets. These results should facilitate the identification of epitopes recognized by predominant CTLm from horses controlling a lentivirus infection. (C) 1997 Academic Press.