PACTG 185 compared the effectiveness of AZT alone versus AZT plus immune globulin containing HIV-1 antibodies in preventing perinatal HIV transmission. The trial was designed to learn if the spread of HIV from mother to child could be reduced further by the addition of immune globulin. PACTG 185 was stopped early after the rate of mother-to-infant transmission was found to be only 5 percent for both groups.

As reported in the current issue of NEJM, Dr. Mofenson and her colleagues investigated the factors associated with transmission of HIV in this study. The researchers measured HIV levels in blood samples from 497 HIV-infected pregnant women, all of whom received AZT or AZT in combination with other drugs. Their infants were tested for HIV at birth, and at ages 6 weeks, 6 months and 1 year.

The investigators found that women who had higher levels of HIV-1 RNA in their blood were most likely to bear a child who was infected with the virus.

They also measured other factors that might increase the chances for transmitting HIV from mother to child. These included the numbers of CD4+ T cells, the amount of virus that could be cultured from blood, and the presence of an infection of the membrane containing amniotic fluid at delivery, called chorioamnionitis. Many of these factors were found to increase the risk of HIV transmission when considered alone. However, when all factors were evaluated together, only levels of HIV RNA were found to predict the likelihood of HIV infection.

The risk of transmission was lowest in women with undetectable viral RNA (fewer than 500 copies of viral RNA per ml of blood). None of the 84 women who had undetectable RNA levels at entry into the study and none of the 107 women who had undetectable RNA levels at delivery transmitted HIV to their infants. However, transmission did oc
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Contact: John Bowersox
jbowersox@nih.gov
301-402-1663
NIH/National Institute of Allergy and Infectious Diseases
4-Aug-1999