More Bad News
On AIDS - Virus
Apparently Unreachable
By Maggie Fox
Health and Science Correspondent
WASHINGTON (Reuters) - Scientists had more bad news for HIV patients on Thursday, saying they found that, within days of infecting someone, the virus manages to find hiding places that no drug currently in use is able to reach.
The finding is another setback to doctors who had hoped that perhaps HIV could be stopped early, either with quick drug treatment or by somehow stimulating the body's immune system.
Microbiologist Ashley Haase of the University of Minnesota and colleagues said that within 3 days of getting into the body, the virus sneaks into cells known as resting T-cells.
These cells are good hiding places because they are inactive and thus not noticed by the immune system. Nor can they be targeted by drugs, which need some kind of activity by the virus or the cells it infects in order to work.
``These cells fly below the radar screen of the immune system,'' Haase, who reported his team's work in the journal Science, said in a statement.
``They also live a long time and won't be affected by our current combinations of anti-AIDS drugs.''
Resting T-Cells
HIV infects immune system cells known as CD4 T-cells. When it gets inside, it takes over a cell's machinery and makes it crank out copies of the virus, eventually killing the cell.
While it is actively doing this, the body's other immune cells can detect the activity and move in. And drugs can stop various stages of the hijacking -- which is why cocktails of HIV drugs can help suppress the virus.
But the virus can also get into inactive T-cells, known as ''resting'' T-cells. They can exist in the body for years, even decades, without doing anything. The virus sits inside there too, quiet and unnoticed.
It had been thought that it took some time for the virus to find these latent cells. But Haase's team, working first in monkeys and then in HIV patients, found it finds its way in within 3 days of infection -- before a patient has a single symptom.
To discover this, Haase's team infected 14 rhesus monkeys vaginally, to simulate the most common way HIV is passed on around the world. They killed several of the monkeys one, three, seven and 12 days after infection and looked to see where they could find the virus in their bodies.
Within three days, the resting CD4 T-cells were infected and by the 12th day the virus was found throughout the lymphatic systems and organs of the animals.
``HIV replicates in these cells whether or not they are demonstrably activated and proliferating and the infected cells that are not proliferating have lower levels of viral gene expression and are longer-lived,'' the researchers wrote.
They looked at patients with HIV infections and found a similar pattern. At least half the cells infected early on were resting T-cells, Haase said.
``This study identifies a source of cells that are invulnerable to current therapies,'' Haase said. In addition, most vaccine techniques need activated T-cells to work.
``Sobering News''
Dr. Anthony Fauci, head of the National Institute of Allergies and Infectious Diseases (NIAID), said the study helped explain why people who took strong cocktails of drugs for years were not cured.
``We have shown that you can whittle down the latent reservoir to virtually undetectable levels, but as soon as we stop the drugs, 2 1/2 weeks later, boom -- the virus came right back,'' he said in a telephone interview.
This suggested the virus was hiding.
``This paper shows that this occurs literally at the time of entry of the virus, so it's sobering news,'' he said in a telephone interview.
Fauci added that he never thought there would be a cure for HIV infection anyway.
``I think that we need to work on ways that we can develop drugs that target these latently infected cells, and enhance the immune system so it contains these cells,'' he said.
The body does this naturally, for example, with herpes viruses that infect just about everybody but cause no more trouble than the occasional cold sore.
``We don't die of disseminated herpes disease because our immune system is strong enough to contain it,'' Fauci said.