Important note: Information in this article was accurate in 1998. The state of the art may have changed since the publication date.
Associated Press - Thursday, November 12, 1998
Joseph B. Verrengia, Associated Press Writer
In a study to be released Friday, virologists at Thomas Jefferson University in Philadelphia said that patients with the HIV provirus -- the genetic component of the AIDS virus -- might still be able to transmit the virus to others if they fail to practice safe sex.
In test-tube experiments, the scientists were able to grow the AIDS virus when they combined tiny provirus samples from the men with blood from individuals who had never been infected.
The researchers described these provirus reservoirs as the "Trojan horse" of AIDS, and said they may lurk in the brain and retina cells, too. Determining how to eradicate these last traces is the "endgame" in the two-decade battle against AIDS, they said.
The study will be presented Friday at the annual infectious-diseases meeting being held in Denver.
"In many patients, we've gone 90 yards and we're at the point where we just have to push the ball over the goal line," said Dr. Roger J. Pomerantz, director of the Center of Human Virology at Thomas Jefferson. "But those last 10 yards can be very hard."
In a separate study, Brown University researchers will report that combination drug therapy effectively lowers viral levels in the genital tracts of HIV- infected women. This may reduce the risk of transmitting the virus to adults during sex and to babies during childbirth, said obstetrics researcher Dr. Susan Cu-Uvin.
However, Cu-Uvin said, up to 3 percent of the women in the Brown study did not have detectable levels of HIV in their blood but still had HIV traces in their genital fluids, indicating the presence of provirus.
Other AIDS researchers agreed that these reservoirs of dormant HIV probably represent the final barrier to curing AIDS.
The first step, researchers said, is determining precisely where the genetic traces of HIV are hiding.
A likely location, they said, is the CD4 T cells. The cells function as the immune system's memory and are found throughout the body. Up to 1 million of these cells appear to hang onto the blueprint of HIV for as long as 10 years so the body will recognize the infection and mount a defense if it appears again.
In the Philadelphia study, Pomerantz sampled cells in the semen of seven men who had no detectable HIV freely circulating in their blood or semen.
Pomerantz found provirus reservoirs locked in cells of four of the men. The three other men could have provirus reservoirs in cells located in other difficult-to-study crannies of the body, such as the brain or the retina of the eye, he said.
"These are the patients who are doing the best," Pomerantz said. "If it happens in them, it is likely to be more common in the general HIV-infected community."
He recommended that these men continue taking AIDS drugs and practice safe sex.
AIDS researchers are debating how to best treat -- and perhaps cure -- these carriers.
Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases in Bethesda, Md., has attempted to purge the infected memory cells by triggering them to spring to life with hormones.
In theory, the activated memory cells would release their virus and die. Antiviral drugs would catch the released virus.
Another strategy is to give patients higher doses of existing AIDS drugs or use more powerful ones still in testing stages.
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