Vaccination with plasmid DNA expressing antigen from genomic or cDNA gene forms induces equivalent humoral immune responses

The antibody response to DNA vaccines containing either cDNA or genomic gene forms of the host protective antigen, 45W from Taenia ovis was compared in vaccinated Balb/c mice and outbred sheep by enzyme linked immunosorbant assay (ELISA). Plasmid DNA vaccines containing cDNA or genomic forms of the Taenia ovis host protective antigen 45W were constructed. In vitro transfection of Cos7 cell monolayers with the DNA vaccines revealed expression of full length, highly glycosylated 45W antigen of 40-65 kDa molecular weight. Glycosylation was confirmed using tunicamycin, where tunicamycin-treated transfected cells expressed a 45W protein of 28 kDa. Immunisation of Balb/c mice by intramuscular injection or gene gun delivery of plasmid DNA generated equivalent high titre antibody responses, regardless of whether the antigen gene contained introns. Intramuscular vaccination of outbred sheep with plasmid DNA also generated antibody responses, albeit of low titre. The fine specificity of the antibody response induced by DNA vaccination was compared with that elicited by immunisation with recombinant 45W protein. DNA vaccination elicited antibodies which did not bind linear peptide determinants, in contrast to serum from protein vaccinated mice. This result suggests that DNA vaccination elicits predominantly conformation;specific antibodies. (C) 1999 Elsevier Science Ltd. All rights reserved.