DOH Researchers Identify Maternal HIV-Levels That Predict Perinatal Transmission

Albany, December 18 -- New York State Health Department scientists have identified a threshold level of virus in the blood of an HIV-infected pregnant woman that will predict whether she has a high or a low risk of transmitting the virus to her infant.

The researchers also found that mothers with AZT-resistant virus can transmit the resistant strain to their newborns.

Using highly sophisticated laboratory tests to measure the number of viruses in the blood of HIV-infected pregnant women, the investigators demonstrated that women with viral levels above 50,000 viruses per milliliter had a 75 percent probability of transmitting the virus to their infants, compared with only a 3 percent risk of mother-to-child transmission for mothers with viral levels under 50,000 viruses per milliliter.

The study, published this week in the Proceedings of the National Academy of Sciences, was performed by a research team led by Drs. Barbara Weiser, Harold Burger, and Guowei Fang of the health department's Wadsworth Center.

This is a very important research finding, which has direct bearing on the question of how to prevent the spread of HIV from mother to child, said State Health Commissioner Barbara A. DeBuono, M.D. It underscores the importance of HIV testing early in pregnancy, so an infected woman and her physician may consider the potential benefit of anti-viral therapy to lower the amount of virus in her bloodstream.

The State Health Department scientists used a new testing technique, called quantitative competitive PCR, to rigorously measure the number of viruses in the blood of 30 HIV-infected women. They then determined which mothers transmitted HIV to their infants. Eight of ten women with the highest viral levels (95,000 - 850,000 viruses per milliliter of plasma) transmitted HIV to their newborns. None of the other 20 women with lower viral levels (250 - 78,000 viruses per milliliter) transmitted the virus to their infants.

These findings help to explain the fact that only about 25 percent of babies born to HIV-infected mothers become infected with the virus, State Health Commissioner Barbara A. DeBuono M.D. points out. "The data also form the scientific rationale for aiming to prevent HIV transmission by lowering the viral load in the mother."

The laboratory test process used by health department scientists is not widely available to practicing physicians and patients at the present time.

With access to sophisticated laboratory techniques in the future, physicians may be able to more accurately counsel HIV-infected women about their risk of having an HIV-infected child, Commissioner DeBuono said.

The study also addressed the issue of HIV resistance to the most widely used antiviral drug, zidovidine, called AZT. AZT resistance was detected in 3 of the 30 mothers in this study. Two of these women who had high viral levels transmitted AZT-resistant HIV to their infants. The third mother with a lower viral level did not transmit HIV to her baby, consistent with the study findings.

The research was supported by grants from the National Institutes of Health and the Pediatric AIDS Foundation.

Other investigators who worked on the study are: Dr. Roger Grimson, Dr. Sharon Nachman, and Dr. David Baker of SUNY Stony Brook; Dr. Pamela Tropper, Dr. Christine Reyelt, and Dr. Nancy Hutcheon of St. Joseph's Hospital in Paterson, N.J.; Dr. Douglas Mayers of the Walter Reed Army Institute and Naval Medical Research Institute; Dr. Owen Weislow of SRA Technologies; and Ms. Rosalyn Moore of the Wadsworth Center.

12/18/95-142 OPA

Contact: Claudia Hutton, Director, Public Affairs (518) 474-7354
New York State Department of Health Posted: January 23, 1996