Infection by the Human Immunodeficiency Virus (HIV) triggers a nearly constant battle between two giants: the body's immune system and a powerful virus capable of replicating at a tremendous rate, according to two studies published yesterday.

The findings, which overturn previous ideas of how the virus attacks the body, could eventually mean a shift in the way doctors treat HIV and AIDS, which the virus causes.

The study, published yesterday in Nature, a prominent science journal in London, contradicts he long-held belief that HIV only explodes into a full-scale attack on the body after years of latency.

Researchers at both the University of Alabama at Birmingham and New York University found that, in fact, billions of viral and immune particles battle each other from the first day of an HIV infection. The fight progresses gradually to death, with the immune system losing a little ground every day.

Harvard researchers said they consider the work a considerable advance in scientists' understanding of AIDS.

"I consider these to be important papers," said Ronald C. Desrosiers, professor of microbiology and molecular genetics at the Medical School. "This research will help to focus researchers into the central question--how can every arm of immune response be up, yet the virus continues to replicate in the face of the immune response?"

The journal's editors have described the discoveries as some of the most significant findings on HIV and AIDS to have appeared in years.

"[The papers] are important because they illustrate the very dramatic, real nature of HIV-1 infection," Desrosiers said yesterday. "It is not a silent, latent infection."

Scientists now believe that the immune system is capable of controlling HIV well enough to keep infected people from having symptoms until late stages of infection, when the immune system has practically lost the battle.

Some new drugs all but stop the AIDS virus in its tracks, but not for long. According to Desrosiers, "within weeks or days, resistant virus appears."

These drugs were used by the researchers to understand the dynamics of HIV production. The researchers correlated the virus growth to the level of CD4, a type of white blood cell, and used three types of drugs to inhibit infection.

"The major observation in our work is the kinetics of virus turnover," said George M. Shaw, professor of medicine at the University of Alabama at Birmingham and author on one of the studies, "namely that the half life of the virus is about two days."

When the AIDS virus was discovered in 1984, AIDS seemed like a routine type of disease. HIV attacks a group of white blood cells, called CD4 or T4 cells, which are an essential part of the body's immune system. AIDS was thought to be direct result of this infection.

In 1986, researchers discovered that far too few T4 cells seemed to be infected. From that finding, the central mystery of AIDS was redefined--how could so few viruses be killing all of the white blood cells?

A Few years ago, the lymph nodes, where T cells come to maturity, were unveiled as a large reservoir of the virus, answering one of the researchers' questions. But then the question of how these cells fit into the slow and systematic destruction of the immune system was highlighted.

Researchers began to see that as time passed, more virus was present and fewer T cells existed. Common theory dictated that the virus worked slowly to destroy the immune system. No one seemed to think that the trend was the result of an ongoing and raging battle of virus versus immune system.