The long-term objective of this project is to establish an animal model with a high incidence of fetal infection of the chimeric HIV-1/SIV, RT-SHIV. This animal model will be used to determine if combination anti-retroviral chemotherapy is more effective than monotherapy in prevention of virus transmission from mother to fetus. The first aim of this project is to identify the minimum intra-amniotic dose of the RT-SHIV that will result in 100% infection of the offspring. To date, two pregnant macaques have been inoculated with the RT-SHIV virus, the first at 124 days gestation with undiluted virus stock (104 TCID50) and the second at 119 days gestation with a 1:100 dilution of the stock. Intra-amniotic injections were done under ultrasound guidance to prevent direct infection of the fetus. Care was taken not to infect the mother. Maternal blood was collected at weekly intervals for clinical and virological monitoring. Infants were delivered by C-section to prevent any possible exposure to blood and fluids at the time of birth. Dams were euthanized at C-section. Infant blood was collected for virological and clinical monitoring. Infants were euthanized at ~1 month of age. Analysis of the RT-SHIV in the peripheral blood mononuclear cells by coculture indicated that both dams were infected 7 days after inoculation. Only one of the infants, from the dam inoculated with undiluted stock, was shown to be positive by coculture. Cord blood, amniotic fluid, and amniotic cells from both dams were negative by coculture. RNA and DNA polymerase chain reaction analyses are yet to be conducted.