Immunologic responses of HIV-1-infected study subjects to immunization with a mixture of peptide protein...

V3 loop peptide sequences from several HIV-1 strains were covalently linked to purified protein derivative (PPD) of Mycobacterium tuberculosis. A mixture of PPD conjugates of V3 loop peptides from six different strains of HIV-1 induced a stronger antibody response than a single V3 peptide-conjugate administered to guinea pigs and humans. Sera from animals immunized with a PPD-six peptide-PPD conjugate neutralized multiple primary-isolate strains of HIV-1. Potent immune responses were noted only when animals were primed with bacillus Calmette-Guerin (BCG), PPD was covalently bound to the peptides, and PPD was used as the carrier protein. Based on these animal studies, an immunogen consisting of PPD-conjugated V3 loop peptides from five HIV-1 strains was tested in 7 HIV-1 seropositive PPD skin test positive study subjects. Vaccinees exhibited over time a uniform increase in neutralizing antibodies for both laboratory adapted and primary isolates of HIV-1, including strains from multiple clades. In 3 patients with baseline viral loads between 8000 and 12,000 RNA copies/ml, the viral load declined in 2 patients to <400 copies/ml and in 1 patient to 1200 copies/ml without concurrent administration of highly active antiretroviral therapy (HAART).