Production of Barley yellow dwarf virus antisera by DNA immunization

Antibodies were produced against the 22-kDa coat protein (CP) of Barley yel low dwarf virus strain PAV (BYDV-PAV) by DNA immunization. A cDNA sequence encoding the 22-kDa CP was cloned into a mammalian expression vector (pcDNA 22K), 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 e ncoding the mouse cytotoxic T-lymphocyte antigen 4 to generate pCTLA422K. T hree weeks post immunization, BYDV-PAV-specific immune response was detecte d in serum. Sera from mice injected with pCTLA422K DNA had significantly hi gher antibody titers than those from mice injected with pcDNA22K. Increases in antibody titers were observed over time with each subsequent DNA inject ion. Further, there were large increases in antibody titers when DNA-immuni zed mice were boosted with purified BYDV-PAV virions. These antibody respon ses were higher than that obtained by a single injection of purified BYDV-P AV. The results demonstrate that antibodies against BYDV-PAV can be generat ed using DNA immunization. With this approach, it may be possible to produc e antisera against luteoviruses that occur in low concentrations in host pl ant tissue and are very difficult to purify.