CHICAGO Instead of infiltrating breaks in the
skin, HIV appears to attack normal, healthy genital tissue in
women, U.S. researchers said on Tuesday in a study that offers
new insight into how the AIDS virus spreads.
They said researchers had assumed the human
immunodeficiency virus, or HIV, sought out breaks in the skin,
such as a herpes sore, in order to gain access to immune system
cells deeper in the tissue.
Some had even thought the normal lining of the vaginal
tract offered a barrier to invasion by the virus during sexual
"Normal skin is vulnerable," Thomas Hope of Northwestern
University's Feinberg School of Medicine said in a telephone
"It was previously thought there had to be a break in it
somehow," said Hope, who is presenting his findings at a
meeting of the American Society for Cell Biology in San
He said until now, scientists had little understanding of
the details of how HIV is transmitted sexually in women.
Hope and colleagues at Northwestern in Chicago and Tulane
University in New Orleans developed a new method for seeing the
virus at work. They studied newly removed vaginal tissue taken
from hysterectomy surgeries, and introduced the virus which
carried fluorescent, light-activated tracers.
They watched under a microscope as the virus penetrated the
outer lining of the female genital tract, called the squamous
epithelium. They also observed the same process in nonhuman
In both cases, they found HIV was able to quickly move past
the genital skin barrier to reach immune cells, which the virus
Hope said the study suggests the virus takes aim at places
in the skin that had recently shed skin cells, in much the same
way that skin on the body flakes off.
The finding casts doubt on the prior theory of the virus
requiring a break in the skin or gaining access through a
single layer of skin cells that line the cervical canal.
And it might explain why some prevention efforts have
failed. Hope said one clinical trial in Africa in which women
used a diaphragm to block the cervix had no effect at reducing
transmission of the virus. Nor have studies of drugs designed
to prevent lesions in genital herpes proven effective.
Hope said the findings emphasize the need for treatments
such as a vaccine to prevent infection.
And it makes clear the need for the use of condoms, which
are highly effective at preventing infection.
"People need to remember that they are vulnerable," Hope
said. "The sad part is if people just used a condom, we
wouldn't have this problem."
In the United States, HIV is mostly passed among men who
have sex with men. Females account for 26 percent of all new
HIV cases in the United States, according to the U.S. Centers
for Disease Control and Prevention.
Globally, HIV is more commonly spread by heterosexual sex.
The virus has infected 33 million people globally and has
killed 25 million.
(Editing by Will Dunham and Mohammad Zargham)