Research recently conducted at the Dartmouth Medical School has proven that the HIV virus can infect women not only through sexual intercourse by passing through a tear in the vaginal wall, but it can also infect organs in the upper reproductive tract.
"What this may mean down the road in terms of vaccine development, if one ever becomes available, is that it will have to be tested to see that it protects at all levels of the reproductive tract," DMS Physiology Professor Charles Wira said.
The research was conducted at the Veterans Administration Hospital in White River Junction, Vt. by Dartmouth Medical School professors as part of a program grant from the National Science Foundation.
Research Associate Professor of Medicine and Microbiology Alexandra Howell ran the laboratories at the VA Hospital, which she said are an "HIV core facility for Dartmouth investigators and VA investigators who want to do research with HIV."
Wira said the experiments examined how the HIV virus enters a woman's body.
He said between 40 and 70 percent of all cases of HIV infection worldwide occur as a result of sexual intercourse -- the virus in a male's semen "goes in through the reproductive tract and makes its way into the body."
"So far research has indicated the virus gets into the body through vaginal mucosa through a tear in the vaginal wall or cells in the tract," he said.
Wira said as part of the project studies, researchers used fallopian tube, cervical and uterine tissue cultures from hysterectomies and incubated the cells with the HIV virus.
"They became infected and were able to infect other cells," Wira said.
"HIV [normally] binds to a molecule at the CD4 receptor of a [blood] cell," Howell said. But target cells that were infected in their studies lacked CD4 receptors.
"We are continuing studies in the area of looking at the mechanisms the virus uses to gain entry when a cell lacks the CD4 receptor," she said.
This HIV research, which was conducted over the last two years, is part of a bigger project to understand how hormones regulate the immune system in the reproductive tract of women, "but at this time we don't know anything about the role of hormones and the way they influence infectivity," Wira said.
He said research conducted by DMS Microbiology Professor Hillary White showed that there are T-cells in the uterus that are able to kill viral infections.
"It appears that during the second half of the menstrual cycle, the ability of these cells to protect is shut off, which may be a very important step in allowing pregnancy to occur," Wira said.
"So we speculate that if the T-cells are shut off at this time and the virus is around, then maybe this is a way it could infect women."
He said this idea is only a hypothesis, and it needs to be pursued with further experimental studies.
Although DMS researchers have now proven alternate methods for women to contract the HIV virus, Wira said the new knowledge does not change recommended practices for prevention.
"Abstinence and barrier methods are still the only way" to protect against the HIV virus, he said.
