May 8, 1997
Media Contact: Marc Kusinitz
Scientists at Johns Hopkins and other institutions report that a test that counts AIDS viruses in blood should be routinely used on newborns whose mothers are HIV-positive so that treatment with anti-HIV drugs can be started as early as possible.
The test, until now used only for measuring HIV in adults, offers hope that infants infected with HIV can be identified quickly and their lives extended, perhaps until they are able to respond to newer drug treatments that hold off AIDS indefinitely, according to Thomas C. Quinn, M.D., professor of medicine, molecular microbiology and immunology, and international health.
Based on detecting and measuring the genetic material of HIV in the blood, the test shows within a month after birth whether a baby born to an HIV-positive mother is also infected, according to Quinn. He co-author of a report on a government-funded study published in the May 8 issue of The New England Journal of Medicine. William T. Shearer of Baylor College of Medicine in Houston, Tex., is the principal author.
"Measuring viral RNA in the blood more accurately reflects the level of infection than the usual test that measures anti-HIV antibodies, because most antibodies newborns have are those they get from their mother in the womb," Quinn says. "Until now, doctors had to wait several months before the mothers' anti-HIV antibodies in the baby disappeared and the baby began making its own anti-HIV antibodies."
The ability to track the level of AIDS virus in infants not only lets doctors identify infected infants, but also shows whether babies were infected in the womb during birth, Quinn says. Infants infected in the womb have higher HIV levels when they are born than newborns who get infected only during birth, he explains. By one month of age, babies with low levels of virus tend to be "slow progressors" to AIDS, while those who have high levels may become rapid progressors. The team also found that only about one-fourth of babies born to infected mothers are infected.
Using the test, which measures virus RNA (genetic material) with a technique called polymerase chain reaction, the team found that the pattern of infection in infants differs from the adult pattern. In both infants and adults, the viral levels rise. However, in adults the virus levels fall quickly, while in infants the virus level falls slightly after a few months and remains much higher than in adults, Quinn explains. "These viral kinetics demonstrate why young children die faster with this disease than do adults."
"Our findings have defined what's happening to HIV levels in infected infants," he says.
Quinn said there is no specific level of virus beyond which infants will definitely progress rapidly to AIDS. But in infants with less than 70,000 viruses per milliliter by one month or thereafter, there was no progression.
"This study shows that if you treat babies early and keep their virus load below 70,000 you have a good chance of preventing an early death," says Quinn.
The researchers studied 106 infants for at least one year, or until infants younger than one year died of AIDS. (This study was done was before the discovery that AZT treatment significantly decreased risk of transmitting HIV during pregnancy..) The infants were part of the Women and Infants Transmission Study, funded by the National Institutes of Health.
Other authors of the report include Philip La Russa (Columbia Presbyterian Hospital, New York, N.Y.), Judy F. Lew, Lynne Mofenson and Vincent Smeriglio (National Institutes of Health, Bethesda, Md.), Susan Almy and Leslie Kalish (New England Research Institute, Watertown, Mass.) Kenneth Rich (University of Illinois at Chicago), Edward Handelsman (State University of New York Health Science Center at Brooklyn), Clemente Diaz (University of Puerto Rico, San Juan), and Marcello Pagano (Harvard School of Public Health, Boston, Mass.).