Science / Medicine : Researchers Focus on Latent AIDS Viruses

AIDS researchers are carefully studying a small number of cases in which people appear to have been infected with the AIDS virus several years before such infection could be detected with standard blood tests.

The situation is called “latency.” It was a key topic of discussion last week at an AIDS meeting sponsored by Abbott Laboratories.

In a latent viral infection, viral genes become incorporated into the genes of infected cells, but no viral particles are produced. As a result, an infected person would not produce antibody molecules in response to the multiplying virus.

But after a period of time--perhaps months or years--the virus begins to reproduce and antibody molecules are made.

While latency is of great scientific interest as a means of better understanding the AIDS virus, its practical significance is not clear.

So far, the situation has apparently been observed with the AIDS virus in several French hemophiliacs studied by Dr. Luke Montagnier of the Pasteur Institute in Paris and two homosexuals being studied in Frankfurt, West Germany. Their latent AIDS virus infections have lasted two years or more, compared to the approximately one year of latency that had been detected in earlier studies.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, cautioned that researchers will need “to learn from experience” how long the latency period is and how frequently the apparently rare situation occurs. Another unanswered question is whether the virus can be transmitted during the latent phase of infection.

New blood tests that can detect viral genes in the absence of viral particles or antibodies are under development. When they become widely available, “people in high-risk groups may wish to have their blood checked for latent infection,” Fauci said.

Latent AIDS virus infections are not expected to affect the safety of the blood supply. This is because individuals in AIDS high-risk groups are already ineligible to donate blood, even if they test negative for AIDS antibodies.

In another development, scientists may soon have a better means of distinguishing the original human immunodeficiency virus, known as HIV-1, from a variant AIDS virus, known as HIV-2.

According to Flossie Wong-Staal of the National Cancer Institute, a recently discovered protein is unique to HIV-2 and not found in HIV-1. The discovery should lead to the development of blood tests that can reliably distinguish between the two viruses.

HIV-2 was originally detected in West Africa. But now infected individuals have been found in other parts of Africa and Western Europe.