HIV RNA GOOD PRENATAL PREDICTOR

By Sean Henahan, Access Excellence

LOS ANGELES (3/6/96)- An HIV-positive mother's level of viral RNA is a useful predictor of transmission risk to the unborn child, report researchers from the University of California, Los Angeles, School of Medicine.

The researchers studied 92 HIV-1 seropositive women (95 pregnancies) and their 97 infants. Forty-two mothers (43 pregnancies) received antiretroviral therapy with zidovudine during pregnancy and/or during labor and delivery. Eleven infants received prophylactic zidovudine for the first six weeks after delivery.

Twenty of the 97 infants in the study were perinatally infected with HIV-1. Mothers transmitting the virus were much more likely to have higher HIV RNA levels (50,000 RNA copies/ml or more) than mothers who did not transmit the virus to their babies. No HIV transmission occurred when RNA levels were below 20,000/ml.

The study also appears to provide more support for using zidovudine (formerly known as AZT) in pregnant women to prevent perinatal transmission. The FDA approved the use of zidovudine for this indication following definitive results from clinical trials showing reduced HIV transmission among treated women. Indeed, in this study, none of the 22 women receiving zidovudine in an an open-label study transmitted the virus.

The information from this study should help physicians to gauge the risk of a pregnant woman transmitting HIV to her unborn child. In addition to zidovudine, the original antiretroviral drug, several newer agents have also been shown to be beneficial in the pediatric setting. An increasing amount of data now suggests that measuring HIV-RNA viral load is the most useful way to measure whether or not the drugs are working. (See accompanying article for more info.)

"The results of our study extend recent findings suggesting that HIV-1 load is an important factor associated with perinatal transmission. However, given the multifactorial nature of perinatal HIV-1 transmission, exceptions to these levels will undoubtedly occur, depending on such variables as viral phenotype, the presence of chorioamnionitis, the timing of transmission, the use of antiretroviral therapy in mothers and infants, and obstetrical and delivery factors," noted Ruth E. Dickover, Ph.D., from the Department of Pediatrics, UCLA School of Medicine, Los Angeles, Calif.

The researchers believe zidovudine exert its protective effect by reducing maternal HIV-1 levels prior to delivery, inhibiting HIV-1 in blood and secretions and in the fetus during labor and delivery, and preventing HIV-1 from establishing infection in the fetus/infant.

"These results strongly suggest that one of the major protective effects of zidovudine treatment lies in its ability to decrease maternal HIV-1 levels prior to delivery. This does not rule out the potential of zidovudine protection of the fetus in utero. Further studies will be needed to address the role of zidovudine infusion and/or treatment of the infant following delivery in preventing late in utero or intrapartum transmission," Dr. Dickover added.

However, researchers caution that much research is still needed in this area. None of the HIV RNA quantification assays are yet licensed for clinical use. Questions also remain about the reliability of the assays when they are performed under less stringent conditions by hospital and commercial laboratories. Also, little is known about how the various different assays and specimen collection and processing techniques compare. More information is also required on the fluctuations in HIV RNA levels over time and under various clinical circumstances and the impact of HIV-related infections and cancers on viral load.

This research appeared in the Journal of the American MedicalAssociation, Feb. 28, 1996.

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