Broad serum neutralizing activity against HIV is rare and so far no vaccine has been able to elicit such a response. Although the response to the V3 variable domain sequences has been studies in Clade B HIV strains, the ability of the Clade C V3 region to induce neutralizing antibodies has not been studied. The researchers sought to immunize rabbits with consensus Clade C peptides spanning the V3 region of gp120. Rabbits were immunized multiple times and serum was collected at several time points in order to measure the capacity for these peptides to induce neutralizing antibodies to Clade C and other HIV viruses.