Immunogenicity of Recombinant Adenovirus-Human Immunodeficiency Virus Vaccines in Chimpanzees Following Intranasal Administration

Recombinant adenovirus (Ad)-human immunodeficiency virus (HIV) vaccines expressing HIVIIIB Env and Gag proteins were evaluated for immunogenicity in chimpanzees following intranasal administration. When Ad7-, Ad4-, and Ad5-vectored vaccines were administered sequentially at 0, 24, and 52 weeks, respectively, to three chimpanzees, the inoculations resulted in limited virus replication in the nasopharynx, but extensive Ad-HIV replication occurred in the intestine. High-titered IgG serum antibody responses to Env and Gag that were nonneutralizing were induced following booster administration of Ad4-HIV recombinant viruses. Following the Ad5-HIV booster, low levels of neutralizing antibodies as well as V3 loop antibodies were induced in all three chimpanzees that persisted for several months. Administration of a gp160 subunit vaccine (baculovirus derived) in SAF-m 24 weeks later boosted broadly neutralizing serum antibodies that peaked within 1 month of the injection. Two additional subunit boosters 19 and 37 weeks later were progressively less effective at stimulating serum neutralizing antibody responses. Substantial local immune responses were induced in nasal, vaginal, and salivary secretions following the third Ad-HIV intranasal immunization. These responses were further boosted with the gp160 subunit vaccine, which also stimulated production of rectal antibodies. The predominant responses in all secretions tested were of the IgG isotype, although some IgA responses were also detected. Strong blastogenic responses to HIV recombinant Env and Gag proteins were induced after each immunization.