Responses on Vaccination of Mice With a Homologous Vector

We evaluated changes in global and human immunodeficiency virus (HIV)–specific genital T cells after vaccination of female mice with a replication-defective adenovirus vector of human serotype 5 (AdHu5) expressing Gag protein of HIV-1, in the presence or absence of preexisting immunity to the vaccine carrier. Our data show that preexisting immunity causes a rapid and transient decrease of genital CD41 T cells without increasing the expression of chemokine (C-C motif) receptor 5. Furthermore, preexposure to AdHu5 affects long-term alterations in the magnitude and quality of vaccine-induced Gag-specific CD81 T cell responses. AdHu5-specific antibodies interfere with the induction of transgene product–specific CD81 T cell responses in systemic compartments, whereas somemechanism other than antibodies also seems to affect those that home to the genital tract. In 2 phase IIb clinical trials (Step and Phambili trials), vaccination with an adenovirus (Ad) vector of human serotype 5 (AdHu5) expressing antigens of human immunodeficiency virus (HIV) induced potent T cell responses but failed to reduce transmission rates or significantly lower viral loads in individuals who becam