Current issues in the immunoprophylaxis of vertical transmission of HIV

Humoral immunity is thought to play an important role in the natural history of HIV infection. It has been hypothesised that the presence of high titre neutralising antibody may protect against the maternal-fetal transmission of HIV-1 infection. HIV-Ig is a passive antibody preparation consisting of highly purified immune globulin containing high titres of antibody to HIV structural proteins. It contains considerable functional antibody in virus neutralisation and antibody dependent cytotoxicity assays. This product (and others) have undergone extensive investigation in preclinical (in vitro and animal models) and clinical trials. In a randomised, double-blind trial, pregnant women with HIV infection who were receiving antiretroviral therapy received either HIV-Ig or control intravenous Ig. While transmission rate was 5 to 6% in both treatment and control arms (sample size was too small to show a difference), infected infants who received HIV-Ig had a delayed time to culture positivity versus those receiving intravenous Ig, suggesting that HIV-Ig may have the ability to modify disease but not prevent infection. While this study did not prove an effect of HIV-Ig it did prove an effect of antiretroviral therapy in a population of women with prior zidovudine experience. Passive antibody preparations (HIV-Ig and monoclonal antibodies) may have the potential to decrease perinatal transmission in combination with antiretroviral agents, to levels less than 5%. Special niches where immunoglobulins and HIV vaccines may play a role, include treatment of infants born to women who do not receive prenatal care, or where the diagnosis of HIV in mother and infant is made only following delivery: a post-exposure prophylaxis strategy.