MATERNO-FETAL TRANSMISSION OF HUMAN-IMMUNODEFICIENCY-VIRUS - ANALYSIS OF RECENT EPIDEMIOLOGIC, IMMUNOLOGICAL AND VIROLOGICAL DATA

Transmission of human immunodeficiency virus (HIV) from mother to foetus/infant is thought to occur during pregnancy and delivery, with postnatal transmission via maternal breast feeding. Information on the prevalence of HIV infection in women of reproductive age is required to understand epidemiologic features, to predict its future course, to initiate counseling and testing programs, and to implement prevention strategies. In Europe and North America, transmission of HIV infection from mother to infant accounts for 15 to 20 % of AIDS in children. In contrast, reports from studies in Africa and South America give rates as high as 45 percent, probably underestimated due to the lack of systematic application of the Bangui clinical case definition of AIDS in Africa. Although studies have confirmed the occurrence of materno-foetal transmission of HIV infection, transmission routes remain unclear. Reports suggest transplacental passage, in some cases during early; pregnancy. The risk of foetal infection does not correlate with any particular maternal parameter, including T-cell levels and circulating anti-p24 or anti-gp120 antibodies, with the possible exception of some high-affinity neutralizing antibodies. The materno-foetal transmission of HIV infection may be related to the extent of maternal viraemia. Several possible mechanisms involved in foetal infection, related to the structure of the placenta, are proposed: (?) direct passage of infected maternal blood cells through the placental barrier; (2) Fc-R mediated transport across the placenta of viral particle bound to maternal HIV-specific IgG antibody; (3) direct viral binding and internalization of CD4 or CD4-like molecules, if they exist at the maternal-foetal interface. An animal model such as that of simian immunodeficiency virus (SIV) in macaques appears highly suitable for further studies concerning placental HIV transmission and its prevention.