Two defined cytotoxic T lymphocyte (CTL) epitopes from equine infectious an
emia virus (EIAV)-infected horses, equine leukocyte alloantigen (ELA)-A5.1
-restricted epitope 18a, and ELA-AS-restricted epitope 28b-1 were evaluated
for conservation among three wild-type EIAV strains. Epitope 18a variation
occurred in all three wild-type EIAV strains, while epitope 28b-1 varied i
n one strain. Further, 12% amino acid changes occurred in the Gag proteins
of a recently isolated wild-type strain, documenting a much greater Gag pro
tein variation than previously reported. Evaluation of epitope 18a among tw
o virus isolates from sequential disease episodes in a single horse, H513 (
ELA-A5.1/A8), demonstrated that no variation that affected CTL recognition
occurred. H513 PBMC had CTLm to epitope 18a before the occurrence of diseas
e episodes caused by viruses expressing epitope 18a; however, the frequenci
es were low (5-15/10(6) PBMC). Later in infection there was an absence of d
isease episodes associated with an increase in CTLm frequency to EIAV(WSU5)
-infected targets, but not epitope 18a-pulsed targets. Therefore, if CTLm t
o EIAV epitopes were involved in maintaining the carrier state in H513, the
y recognized epitopes Other than 18a. (C) 1999 Academic Press.