Posted on March 25, 2004 at 1:00 p.m.

BIRMINGHAM, AL — In individuals newly infected with HIV, the virus that establishes infection is susceptible to inactivation by antibodies from the transmitting partner, according to a recent study by researchers at the University of Alabama at Birmingham (UAB). Details of the study are published in the March 26 issue of Science.

The new information may be helpful in developing a vaccine against HIV. “Following infection, it takes a couple of weeks for the body’s immune system to mount an attack, allowing the virus to replicate unchecked,” said Cynthia Derdeyn, Ph.D., research instructor with the department of microbiology at UAB and lead investigator of the study. “However, our study shows that during this time the virus also is especially vulnerable. Perhaps this period of greater susceptibility can be exploited."

Heterosexual transmission accounts for the majority of HIV infections worldwide. But studies aimed at determining how the virus is acquired have focused primarily on homosexual and mother-to-infant transmissions. “In this study, we closely examined male-to-female and female-to-male transmissions,” Derdeyn said.

The study was part of a larger ongoing project in Zambia led by Dr. Susan Allen, associate professor of public health at UAB, to test, counsel and monitor heterosexual couples in which one partner is HIV positive. “All couples are encouraged to use condoms and to take precautions to avoid transmission,” Derdeyn said. “As a result the project has significantly reduced the transmission rate from more than 20 percent to 8 percent among participating partners.” Couples are seen and non-infected partners are tested for HIV every three months. “This allows us to quickly identify newly infected individuals, something that is normally very difficult to do,” Derdeyn said.

Among newly infected partners, researchers discovered unusual characteristics about the virus. “The virus that established the infection is less shielded than the virus in the infecting partner,” Derdeyn said. “Its entry molecule is smaller in size and has less sugar substance covering its surface, which means it is less protected.”

Findings raise many questions about how and why the virus must shed some of its armor before leaving its host and how the unprotected virus is able to avoid an attacking immune system as it escapes an individual with an established infection. “More research is needed but we believe these findings are key in better understanding the nature of how the infection is acquired, especially heterosexually,” Derdeyn said.

NOTE: The University of Alabama at Birmingham is a separate, independent campus from the University of Alabama, which is located in Tuscaloosa. Please use University of Alabama at Birmingham on first reference and UAB on second reference.