Immune responses in a horse inoculated with the VP2 gene of African horsesickness virus

The ability of a DNA vaccine to elicit an immune response in a horse was ev aluated. The outer capsid protein VP2 of African horsesickness virus is kno wn to elicit protective immunity in horses. Reverse transcribed DNA of the gene encoding VP2 was placed under the transcriptional control of the cytom egalovirus immediate-early enhancer/promoter and was injected on several oc casions intramuscularly into a horse. Low antibody levels could be detected by ELISA. Antibodies directed against VP2 alone were shown by Western blot while low levels of neutralizing antibodies were detected by a 50% plaque reduction assay. In contrast to a relatively poor humoral response, a signi ficant lymphoproliferative response in the presence of whole virus proteins , as well as a cytotoxic cellular reaction against virus-infected syngeneic target cells was shown.