Production of Barley yellow dwarf virus antisera by DNA immunization

Antibodies were produced against the 22-kDa coat protein (CP) of Barley yellow dwarf virus strain PAV (BYDV-PAV) by DNA immunization. A cDNA sequence encoding the 22-kDa CP was cloned into a mammalian expression vector (pcDNA22K), entrapped in liposomes, and injected intramuscularly into BALB/c mice. To target the antigen to sites of immune induction and, thereby, enhance the immune response, the 22-kDa sequence was also fused with the sequence encoding the mouse cytotoxic T-lymphocyte antigen 4 to generate pCTLA422K. Three weeks post immunization, BYDV-PAV-specific immune response was detected in serum. Sera from mice injected with pCTLA422K DNA had significantly higher antibody titers than those from mice injected with pcDNA22K. Increases in antibody titers were observed over time with each subsequent DNA injection. Further, there were large increases in antibody titers when DNA-immunized mice were boosted with purified BYDV-PAV virions. These antibody responses were higher than that obtained by a single injection of purified BYDV-PAV. The results demonstrate that antibodies against BYDV-PAV can be generated using DNA immunization. With this approach, it may be possible to produce antisera against luteoviruses that occur in low concentrations in host plant tissue and are very difficult to purify.