HIV Insights

October 1, 2008

Two new studies about HIV have come out of Duke recently, both hinting at the importance of more comprehensive education and testing programs.

The first concerns the potential spread of the virus in elderly populations. Regular HIV testing has traditionally been recommended for young people. The Centers for Disease Control and Prevention, for example, recommends HIV screening only for patients ages thirteen to sixty-four.

The rationale is that the screening is more cost-effective—even if the prevalence of the disease is low—because young people are likely to have more sex partners, and the benefits of early diagnosis and treatment will be enjoyed over a long period.

Cost-effectiveness is often measured in quality-adjusted life-years (QAYLs), a figure that takes into account numerous factors, including the quality and length of life.

But recent studies show that large numbers of Americans now remain sexually active well into their sixties, seventies, and even eighties, and, in response, a team of researchers, including some at Duke, designed a study to evaluate the cost-effectiveness of screening patients fifty-five to seventy-four.

Assuming that 0.5 percent of the study population was HIV-positive, the researchers found that HIV screening for patients aged sixty-five who were not sexually active would cost $55,440 per QALY gained, while screening for sexually-active sixty-five-year-olds would cost $30,020 per QALY. Researcher Gillian Sanders, an associate professor of medicine at the Duke Clinical Research Institute, says such figures are within the range of other accepted cost-effective ratios, and in the United States, these would generally be considered "a good use of our health-care dollars."

"All of us also need to remember that age doesn't protect anyone from HIV," Sanders says. "You're as vulnerable at sixty as you are at sixteen."

The second study has to do with the speed at which the HIV virus takes hold. Until now, scientists believed that the window of opportunity to intervene in the process of HIV-1 infection lay in the three to four weeks between transmission and the development of an established pool of infected CD4 T-cells, key infection fighters in the body.

But the new study, based on thirty people who were recently infected with HIV-1, showed that the virus does a great deal of damage to the immune system very early on. The researchers took blood samples from each of the study participants every three days for several months, measuring their plasma for four products of CD4 T-cell death.

They found that levels of one product in particular, known as "tumor necrosis factor-related apoptosis-inducing ligand" (TRAIL), increased significantly a full week before peak viral load, which occurs approximately seventeen days after HIV-1 transmission, suggesting that during the earliest period of infection, TRAIL may actually hasten HIV-1's destruction of CD4 T-cells.

Barton Haynes, the senior author of the study and director of the Center for HIV/
AIDS Vaccine Immunology at Duke Medical Center, says the findings suggest that an optimal vaccine strategy would have to pack a double punch: first, establishing as much immunity as possible before infection, much as classic vaccines do, and then following a few days later with a mechanism to provoke a strong, secondary, broad-based antibody response.