AIDS differs in women and men

January 31, 2000
Web posted at: 3:33 p.m. EST (2033 GMT)

SAN FRANCISCO (Reuters) -- It may be, as one researcher says, "blindingly obvious," but women are different from men, and AIDS researchers are just beginning to realize it.

The findings could mean that women need to be treated earlier than men with any drugs that are available, and drug companies and other researchers are being urged to do new studies and to go back over data from old studies to see if there is any evidence women do respond differently to drugs.

"Women appear to be progressing to AIDS at the same rate as men do," Dr. Thomas Quinn, an AIDS researcher at Johns Hopkins University in Baltimore, said in an interview. "But it is at half the viral load the men have."

Viral load is a measure of how much virus is circulating in the blood, and it is routinely used to measure how serious a person's HIV infection is.

"Until last year, everything was done in gay men. Now that women are infected, we see they are biologically different," Quinn said. "Ding-ding!"

Quinn, one of the organizers of the seventh Conference on Retroviruses and Opportunistic Infections, a meeting of AIDS researchers, said concerned scientists held a mini-meeting of their own to discuss gender differences in HIV.

They discussed several studies that show men and women have different responses to HIV infection, including one published in the journal Nature Medicine last month by Julie Overbaugh of the Fred Hutchison Cancer Research Centre in Seattle and colleagues in Nairobi, Kenya.

"We found that women from Kenya were often infected by multiple virus variants, whereas men from Kenya were not," they wrote.

Different variants

They found the men and women had sex just as often, and with just as many different partners. But the HIV infecting the men seemed to be of one sort, while women had several different variants.

This could be because the women were being infected with more than one kind of HIV, or that the virus was mutating quickly in their bodies, Quinn said.

"It is still not clear what it means," he said.

Women naturally have more CD4 T-cells -- cells that are supposed to recognise and help attack HIV but which themselves are targeted by the virus. A stronger immune response could put pressure on the virus, forcing it to change from one disguise to another to evade the cells.

Or women could get a bigger infection to start with.

"The remarkable observation -- it seems blindingly obvious when you read it -- is that women probably get a bigger (dose) of virus when they are infected compared to men," Robin Weiss, an AIDS expert at University College London, told the opening session of the conference.

Women who are infected sexually -- and they are now the biggest group affected by HIV -- are exposed through semen in the vagina, where it can survive for days. The virus gets in through the porous mucous membranes of the vagina.

If women are infected with more different genetic versions of HIV, this could mean they would react differently to drugs or a vaccine. The influenza vaccine, for example, must be changed every year because the influenza virus undergoes regular genetic shifts.

Whatever the differences, they do not seem to help women. Dr. Janet Blair of the Centres for Disease Control and Prevention (CDC) found that viral load was 52 percent to 85 percent lower in HIV-positive women, but they got sick at the same rate as men did.

"Gender was not significantly associated with progression to AIDS and death," Blair told the retrovirus meeting.

"However, this issue merits further exploration."

Copyright 2000 Reuters Limited. All rights reserved.