Development of a heterosexual transmission animal model of HIV using the East African baboon

Abstract

Human immunodeficiency virus, (HIV), is transmitted sexually by both homosexual and heterosexual contact. Heterosexual transmission is the major route of HIV spread in Africa, accounting for over 70% of all transmissions, and is still the mode of transmission that is least understood. The development of an animal model for heterosexual transmission is therefore of great value in understanding this mechanism of transmission and more importantly, for testing candidate anti-retroviral and immuno-modulating drugs as well as vaccines. In the attempt to develop the baboon as a heterosexual transmission animal model for HIV, six adult baboons were inoculated with HIV-2 and two with SimianlHuman Immunodeficiency Virus, (SHIV). Of the six exposed to HIV-2, two were inoculated via the penile urethra, two vaginally and two intravenously. Of the two exposed to SHIV, one was inoculated vaginally and the other intravenously. Two SIV negative baboons were also inoculated intravenously with saline and served as controls. Blood samples were obtained for culture and serology from all animals at regular time-points and biopsies of inguinal lymph node, spleen, liver, bone marrow and cerebral spinal fluid were obtained for culture from three animals, each representing one group. Virus was recovered from both blood and inguinal lymph node of all SHIV-infected and one of six HIV-2- infected baboons. In addition, all animals inoculated with SHIV were antibody positive by ELISA and one of six HIV-2-infected animals was weakly positive. These results show that the baboon can be developed further as an animal model for HIV. If developed further, the baboon will be a valuable and practical animal model for studying heterosexual transmission, assessing the role of co-factors in heterosexual transmission of HIV and testing the effectiveness of spermicides, pharmacological agents and vaccines in preventing the heterosexual transmission of HIV.