Mapping of B-cell epitopes in rabbits immunised with various gag antigens for the production of HIV-1 gag capture ELISA reagents.

An HIV-1 p24 capture enzyme linked immunosorbent assay (ELISA) was developed and used in a study of B-cell epitopes in rabbits immunised with different gag p24 antigens. Rabbits were immunised with virion HIV-1/Lai, baculovirus recombinant p24, Escherichia coli recombinant p24-15 and a mixture of synthetic peptides representing sequences of HIV-1 gag p24 protein, respectively. Five out of nine rabbits developed antibodies that could be used for an antigen capture ELISA. No significant differences in IgG titers to the whole gag protein were seen when comparing rabbits immunised with four different antigens. Three major common linear epitope regions were mapped in the rabbits immunised with virion HIV-1/Lai and baculovirus recombinant p24. The rabbit immunised with HIV-1 gag peptides had the broadest linear epitope reactive responses whereas animals immunised with E. coli recombinant antigen had the most restricted linear epitope response. The capture ELISA method thus developed using the different rabbit anti-p24 IgG preparations was shown to capture isolates from HIV-1 subtypes or clades A to G. Only rabbits immunised with virion HIV-1/Lai and baculovirus recombinant p24 developed IgG that was capable of efficiently capturing HIV-1 p24 in ELISA, indicating the importance of preparing antibodies able to recognise native or discontinuous and linear antigen configurations.