Suppression of maternal virus load with zidovudine, didanosine, and indinavir combination therapy prevents mother-to-fetus HIV transmission in macaques

Recently, we developed a maternal-fetal macaque model using a highly pathogenic HIV-2 strain, HIV-2(287), to study the time course of HIV transmission in utero. Most pregnant macaques (Macaca nemestrina) infected with HIV-2(287) (10-10(3) infective doses) transmitted HIV to their fetuses. as verified by positive identification of virus-infected mononuclear cells and free viral RNA in fetal blood. To determine whether an antiretroviral drug combination therapy composed of two dideoxynucleosides, azidothymidine (15 mg/kg) and dideoxyinosine (15 mg/kg), and a protease inhibitor, indinavir (25 mg/kg), could completely inhibit mother-to-fetus HIV transmission, we administered these drugs orally through gastric catheters to five pregnant macaques infected with 10 infective doses of HIV-2(287). Beginning 30 minutes after HIV inoculation, the dams were given the combination antiviral therapy three times daily until delivery by cesarean section. Drug treatment reduced the maternal virus load to a minimally detectable level but did not prevent primary HIV-2(287) infection. All fetal and infant blood samples were virus negative by internally controlled RNA polymerase chain reaction (QC-RNA-PCR) and virus coculture assays. Fetal and infant CD4(+) T-cell levels remained normal throughout the experiment. These findings strongly suggest that combination chemotherapy with azidothymidine, dideoxyinosine, and indinavir can suppress maternal viral load enough to prevent mother-to-fetus transmission of HIV.