Effect of preexisting immunity to adenovirus on transgene product-specific genital T cell 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 CD4(+) 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 CD8(+) T cell responses. AdHu5-specific antibodies interfere with the induction of transgene product-specific CD8(+) T cell responses in systemic compartments, whereas some mechanism other than antibodies also seems to affect those that home to the genital tract.