Fig. 2.

Induction of a type 1 immune response to the 19-kD antigen by DNA vaccination. (a) Antibody responses to the 19-kD antigen were measured by ELISA assay in sera from mice immunized by DNA vaccination. A strong IgG2a response was consistent with induction of a type 1 immune response. There was no detectable antibody response to the 19-kD antigen in mice immunized with vector control. (b) Splenocytes from vaccinated and control mice were incubated with 19-kD antigen purified from recombinant mycobacteria (‘19 kD’), or from Escherichia coli after expression as an acylated (‘lipoprotein’) or non-acylated (‘polypeptide’) histidine-tagged recombinant. In each case, a strong IFN-γ response was observed using splenocytes from mice immunized with the 19-kD construct.