HIV's viral helper

USC researchers report in the New England Journal of Medicine that a common virus appears to push HIV's progression in infected babies

LOS ANGELES, July 8, 1999 -- Infants infected with both HIV and another virus known as cytomegalovirus appear to more speedily show serious symptoms of HIV and AIDS (or die) than babies infected with HIV alone, according to researchers at the University of Southern California.

The common cytomegalovirus, or CMV, infects a majority of the world's people by the time they are in their 40s, although it usually causes no symptoms in most healthy individuals. But for babies who are HIV-positive, it can be deadly. Those babies may quickly come down with motor problems, stunted brain growth, pneumonia and other symptoms of AIDS, report USC researchers in this week's issue of the New England Journal of Medicine.

The discovery sheds light on how viruses may work together to cause disease and may lead scientists toward further understanding of how and why some individuals have more rapid progression of HIV, the virus that causes AIDS.

"CMV may also impact adults with HIV, especially if they get infected with HIV and CMV at the same time--or perhaps even after they are infected with HIV," says Andrea Kovacs, M.D., USC associate professor of pediatrics and pathology. "Hopefully this will spur research on viral interactions and the impact on disease."

In studies sponsored by the National Heart, Lung and Blood Institute and the National Institutes of Health General Clinical Research Center, Kovacs and her colleagues monitored babies born to HIV-positive mothers. They kept track of which infants contracted CMV, one of the herpes viruses, and when they were infected with it.

By the time babies reached 18 months of age, HIV had progressed more quickly in about seven of every 10 infants with both infections, compared to only three of every 10 infants with HIV but not CMV. Babies with both infections were more than twice as likely than babies with HIV alone to have died or come down with serious symptoms such as pneumonia, and nearly three times as likely to show stunted brain growth or motor problems.

There may be some give-and-take between the viruses, according to Kovacs: Babies with HIV tend to contract CMV more often than other babies, too. More than 4% of HIV-positive and HIV-negative babies in the study were infected with CMV in the womb (far greater than the 1% infected with CMV in the womb in non-HIV infected populations). But by six months of age, about 40% of HIV-positive babies were infected with CMV, far higher than the 15% of HIV-negative babies who were infected with the virus.

So what accounts for the interplay between the viruses? Perhaps CMV produces a protein within human cells that helps HIV replicate and spread. CMV may affect the immune system as a whole so that the body cannot fight infections, or CMV may promote HIV's growth locally in tissues, says Kovacs, director of the Comprehensive Maternal-Child HIV Management and Research Center at LAC+USC Medical Center.

Scientists in Kovacs' lab and other AIDS researchers are looking into these and other possibilities through further studies, she says.

CMV has been associated with HIV since its beginnings. Because patients with advanced HIV or AIDS have compromised immune systems, CMV can manifest itself as a disease in those patients with symptoms such as a low-grade fever, blindness, mouth sores and a swollen esophagus. But the USC study shows that CMV appears to further the symptoms of HIV.

In laboratory experiments, CMV and HIV have been shown to help each other grow. However, scientists have previously had difficulty demonstrating the effect in human beings.

The Centers for Disease Control reports that about 2.2 million Americans carry the HIV virus, and more than 315,000 people in the U.S. were diagnosed with AIDS in the last decade.

Numbers are much higher for CMV, which is the virus most frequently transmitted to a developing child before birth, according to the CDC. Among HIV-free mothers and babies, infants who get CMV in the womb may still develop serious neurological symptoms. CMV requires close and intimate contact with an infected person, who can transmit the virus through saliva, urine or other body fluids.

Andrea Kovacs, et. al., "Cytomegalovirus infection and HIV-1 disease progression in infants born to HIV-1 infected women," New England Journal of Medicine, Vol. 341, No. 2, pp. 77-84.