Vertical human immunodeficiency virus type 1 - HIV-1 - Transmission - A review

Several factors appear to affect vertical HIV-1 transmission, dependent mai nly on characteristics of the mother (extent of immunodeficiency, co-infect ions, risk behaviour, nutritional status, immune response, genetical make-u p), but also if the virus (phenotype, tropism) and, possibly, of the child (genetical make-up). This complex situation is compounded by the fact that the virus may have the whole gestation period, apart from variable periods between membrane rupture and birth and the breast-feeding period, to pass f rom the mother to the infant. It seems probable that an extensive interplay of all factors occurs, and that some factors may be more important during specific periods and other factors in other periods. Factors predominant in protection against in utero transmission may be less important for peri-na tal transmission, and probably quite different from those that predominantl y affect transmission by mothers milk. For instance, cytotoxic T lymphocyte s will probably be unable to exert any effect during breast-feeding, while neutralizing antibodies will be unable to protect transmission by HIV trans mitted through infected cells. Furthermore, some responses may be capable o f controlling transmission of determined virus types, while being inadequat e for controlling others. As occurence of mixed infections and recombinatio n of HIV-1 types is a known fact, it does not appear possible to prevent ve rtical HIV-1 transmission by reinforcing just one of the factors, and proba bly a general strategy including all known factors must be used. Recent rep orts have brought information on vertical HIV-1 transmission in a variety o f research fields, which will have to be considered in conjunction as backg round for specific studies.