A new look at HIV transmission from seropositive mothers to their infants: the facts beyond serology.

Once the curtain of maternal antibodies is removed (12-18 months) only a fraction of the infants are seropositive. Some babies from whom virus has been isolated or detected in their cells subsequently become seronegative. What does the negative serology of these children really tell us about exposure to HIV? It is suggested that seroconverting is only one of the ways to respond to an HIV exposure from an infected mother; it is not the only or the best way. Some form of tolerance to HIV, emerging after in utero exposure of the fetus, could theoretically lead to a seronegative state despite infection. Based on monkey studies with simian immunodeficiency virus (SIV), this tolerance could offer protection against pathological outcome of the infection. Seronegative yet infected/exposed children of HIV-positive mothers exist, though their number remains unknown. They might hold the key to a protective immunity to HIV.