FIG. 6.

Generation of binding and neutralizing antibodies following the second booster immunization with the modified ΔV2 gp140 protein. (A) The generation of antienvelope antibodies in two rhesus macaques (J408 and H445) vaccinated with the modified ΔV2 gp140 immunogen was determined by ELISA as described in Materials and Methods. Dashed lines indicate times of immunizations. DNA, animals received three monthly immunizations with DNA vectors expressing the gp140 form of this immunogen; DNA plus Protein, animals received a fourth DNA immunization and purified oligomeric ΔV2 gp140 protein; Protein, the animals were immunized with the purified oligomeric ΔV2 gp140 protein alone. (B) Neutralization activities against the SF162ΔV2 and SF162 isolates of sera following the second boost were compared to those of sera collected following the first boost (see also Fig. 4). Nonspecific neutralization recorded with preimmunization sera (Pre-bleeds) is also shown.