The EIAV (equine infectious anemia virus) multi-species attenuated vaccine EIAV DLV121 successfully prevented the spread of equine infectious anemia (EIA) in China in the 1970s and provided an excellent model for the study of protective immunity to lentiviruses. In this study, we compared immune responses induced by EIAV DLV121 to immunity elicited by the virulent EIAV LN40 strain and correlated immune responses to protection from infection. Horses were randomly grouped and inoculated with either EIAV DLV121 (Vaccinees, Vac) or a sublethal dose of EIAV LN40 (asymptomatic carriers, Car). Car horses became EIAV LN40 carriers without disease symptoms. Two of the four Vac horses were protected against infection and the other two had delayed onset or reduced severity of EIA with a lethal EIAV LN40 challenge 5.5months post initial inoculation. In contrast, all three Car animals developed acute EIA and two succumbed to death. Specific humoral and cellular immune responses in both Vac and Car groups were evaluated for potential correlations with protection. These analyses revealed that although plasma viral loads remained between 10 3 and 10 5copies/ml for both groups before EIAV LN40 challenge, Vac-treated animals developed significantly higher levels of conformational dependent, Env-specific antibody, neutralizing antibody as well as significantly elevated CD4 + T cell proliferation and IFN-γ-secreting CD8 + T cells than those observed in EIAV LN40 asymptomatic carriers. Further analysis of protected and unprotected cases in vaccinated horses identified that cellular response parameters and the reciprocal anti-p26-specific antibody titers closely correlated with protection against infection with the pathogenic EIAV LN40. These data provide a better understanding of protective immunity to lentiviruses.
All Science Journal Classification (ASJC) codes
- Immune response