Contact: Hali Wickner (603) 650-1520
AIDS Virus Risk in Women May Be Enhanced
For immediate release
May 14, 1997
Dartmouth Medical School
Contact: Hali Wickner
(603) 650-1520
AIDS Virus Risk in Women May Be Enhanced
Women may be more vulnerable than previously assumed to contracting the AIDS virus from their male sexual partners, according to findings by Dartmouth Medical School and VA Medical Center researchers.
Their studies, the first to demonstrate that the AIDS virus infects
normal tissues throughout the female reproductive tract, could help unlock new
approaches for AIDS treatment and prevention.
The implications are far-ranging. Vaccine development and disease
prevention should aim to confer protection throughout the female reproductive
tract and the right protocols could exclude the AIDS virus from the body by
containing and destroying it within the tract.
The researchers have discovered that HIV, the AIDS-causing virus, can
invade cells within any female reproductive tract organ--vagina, cervix,
uterus, fallopian tubes--meaning that the entire tract is at risk. Until now,
infection was presumed to occur when cells infected with HIV or HIV itself
entered the body through the vagina or cervix.
A team headed by immunologist Alexandra Howell, a medical school
research associate professor at the White River Junction VA, reported their
results in the May issue of the Journal of Virology. Colleagues include
Charles Wira, Michael Fanger, Grant Yeaman, Robert Edkins, Sherry Rier and Judy
Stern.
"Our findings suggest that efforts to control heterosexual transmission
of HIV-1 should include protection at all sites, not just the lower
reproductive tract," Howell said.
Howell and her colleagues are part of a broad Dartmouth Medical School
collaboration that is exploring immunity in the female reproductive tract to
learn how hormones regulate protection.
The program, headed by co-author Wira, focuses on the lining of the
female reproductive tract organs. This mucosa constitute a remarkably diverse
protective system that fluctuates with the reproductive cycle and functions
differently in each organ, offering some intriguing clues to disease
susceptibility and protection.
As Wira explained, "Until this time, we thought that HIV infection was
through a tear in the vaginal mucosa that allows virus to contact the blood, or
after cells in the vagina pick up virus and transfer it to the body. These
studies indicate that not only do cervical and vaginal cells have the potential
to become infected, but so do uterine and fallopian tube cells." Virus may
travel up the reproductive tract either free or in association with sperm and
non-motile cells that are known to reach the fallopian tube, the site of
fertilization.
The Dartmouth team obtained reproductive tract tissues from normal
women undergoing hysterectomy for medical reasons. In the laboratory, they
infected tissue sections as well as single cells from each organ with several
strains of the human immunodeficiency virus-type 1 (HIV-1). They found that
HIV-l infected cells at all sites, including the upper tract (fallopian tube)
and that it infected other types of cells besides T cells and macrophages.
The researchers are currently examining whether female sex hormones,
whose levels fluctuate during the normal menstrual cycle, alter susceptibility
to HIV-1. The investigation builds on related Dartmouth findings that immune
protection in the uterus is turned off during the latter part of the menstrual
cycle, when implantation occurs. "This may mean that women are more
susceptible to HIV infection during certain stages of the menstrual cycle,"
Howell said.
Linking results of several projects, Wira sets a possible scenario.
"Hormonal changes during the menstrual cycle may create a window of opportunity
for HIV infection via the uterus. Studies by (microbiologist) Hillary White, a
program member, suggest that immune cells that would normally kill virally
infected cells are shut down during the second half of the menstrual cycle when
implantation is most likely to occur. HIV, which may be in the ejaculate, can
enter into the uterus. Uterine surface cells not only become infected, but
transmit virus systemically."
-DMS-
RSS