Equine Infectious Anemia Virus as a Model for Lentiviral Pathogenesis

Abstract

Equine infectious anemia virus (EIAV), the etiologic agent of equine infectious anemia (EIA) or swamp fever, is a unique macrophage-tropic lentivirus. EIA, described in the veterinary literature in the mid-19th century, was one of the first diseases determined to be caused by a “filterable agent.” However, studies of the virus languished as methods for its culture in horse leukocytes were not described until the 1960s, and even then difficulty working with equine cultures forestalled its detailed characterization. EIAV was adapted to growth in a persistently infected cell line in 1973, and evidence that EIAV was a retrovirus was presented in 1976. A detailed characterization of viral structural proteins was finally available in the early 1980s.1 Although of considerable veterinary importance, studies of EIAV remained relatively obscure in comparison to the oncogenic retroviruses, especially those affecting more amenable animal models such as chickens and mice. EIAV and the other so-called “slow viruses” of ungulates, maedi-visna virus (MVV) of sheep and caprine-arthritis encephalitis virus (CAEV) of goats, garnered some attention due to reports that described their ability to form viral swarms during persistent infection.