Specificity of response to viral proteins in horses infected with equine infectious anemia virus.

Three structural proteins of equine infectious anemia virus were purified, labeled with 125I, and utilized in radioimmunoassays with horse sera and antisera to heterologous retroviruses. Whereas radioimmunoassay titers for the major protein, p25, were 500- to 1,000-fold higher than titers in immunodiffusion, for clinical purposes these two procedures were equivalent. Antibodies to two low-molecular-weight proteins, p12 and p10, were also found in infected horses, but with a lower frequency and lower titers. As a rule, only sera positive for p25 also contained antibody to p12 and p10. Antisera to the major structural protein of other retroviruses did not precipitate equine infectious anemia virus p25. These sera include antibody to mammalian type C viruses, bovine leukemia virus, visna virus, mouse mammary tumor virus, squirrel monkey retrovirus, and Mason-Pfizer monkey virus.