Sexual and Mother‐to‐Child Transmission of the Human Immunodeficiency Virus Type 1: A Review

PROBLEM: Sexual and mother-to-child transmission of the human immunodeficiency virus (HIV) type 1 occurs only with a low percentage of infection. Many instances of sexual intercourse result in no transmission, and only 20% of children are infected from seropositive mothers (3% in mothers treated with azidothymidine). METHOD OF STUDY: We analyzed the presence of HIV in various ejaculates of the same HIV-infected patients, as well as in the cervico-vaginal fluid. We have studied the mechanism of transmission from mother to child, by analyzing the cell-to-cell transmission in the trophoblast. RESULTS: Some ejaculates collected at different times from the same HIV-infected males are free of virus, explaining the low rate of sexual transmission. We never found HIV in mobile spermatozoa. The trophoblast can be infected by HIV with a strain dependence and also transiently. By analyzing the tissue of the fetus, it was found that only some organs are infected, confirming the cell-to-cell transmission between the mother and child and not a true vertical transmission through the germinal lines. CONCLUSIONS: HIV is not always present in the genital secretion, explaining the low rate of sexual transmission. Mother-to-child transmission occurs during pregnancy but often after the second trimester and at delivery after cell-to-cell or blood transmission, respectively.