Comparison of Immune Gene Expression Between Virulent EIAV and an Attenuated Vaccine Strain

The equine infectious anemia virus (EIAV) is closely related to HIV and has been used as a model to identify protective mechanisms against these viruses. In horses, EIA infection progresses for about a year before the horse manages to control virus replication. Exactly how the immune system operates to gain this control is still under investigation. A modified live vaccine provides effective protection against a challenge with a virulent strain of EIAV without causing disease, though the mechanism of protection remains undefined. We believe that cellular immune responses play a key role in controlling EIAV in the horse. We hypothesize that cytotoxic T lymphocytes (CTL) are upregulated in vaccinated ponies and that there would be a difference in this CTL response between the vaccine and virulent virus- infected ponies. To test this hypothesis, ponies were inoculated with either the vaccine or virulent strain of the virus. Whole blood samples were collected into PAXgene tubes weekly during the acute infection stage (first 6 weeks) and at monthly intervals thereafter corresponding to the chronic infection phase. Total RNA was isolated from the PAXgene tubes and gene expression for both cytokine and CTL markers were determined using qRT-PCR. Gene expression patterns occurring in response to the in vivo infections with the parental virus and the attenuated vaccine were then compared. The results of this study will help to further elucidate the protective mechanisms controlling EIAV replication in horses and could be of interest to those researchers working on HIV