NEW HIV LIFE CYCLE DATA

Photo: EM of HIV Replication

LOS ALAMOS, NM (3/15/96)- New research on the life cycle of HIV suggests the virus replicates at an even faster rate than previously believed. Nonetheless, new insights into HIV replication should help guide the development of new AIDS treatment strategies, report scientists at Los Alamos National Laboratory.

Researchers at Los Alamos' Theoretical Biology and Biophysics Group reported new estimates of how quickly the HIV-1 population multiplies in the body, how long HIV particles last and how long it takes for a viral particle to reproduce.

"We developed a new mathematical model which, combined with frequent sampling, allows us to make an accurate model of the kinetics of the viral particles," said Dr. Alan Perelson, of Los Alamos.

The studies show that far more infectious particles of HIV-1 are produced per day than previously estimated. A report in January 1995 by the same research team first documented a reliable minimal replication rate for HIV.

"Using better modeling techniques and better data sets from patients at different stages of the disease, we found about 10 billion virus particles are produced per day. That is a 15-fold increase from estimates we made a year ago," said Perelson.

The new study also reported the first estimate of how long HIV-infected cells live in the body. The majority live a day and a half.

The results also suggest the minimum duration of the HIV-1 life cycle in the body is 1.2 days on average. The life cycle is measured from the time a mature virus particle is released until it infects another cell and causes the release of a new generation of viral particles.

The study looked at the destruction of the cellular factories where viral particles are produced and at the mechanisms in the body by which particles are eliminated. A new drug that renders the virus incapable of infecting new cells was administered to five patients. The drug, ritonavir, was approved for general use only last week by the Food and Drug Administration. Ritonavir blocks an enzyme the virus needs to be infectious.

This drug treatment study covered a short time scale of just a week, and long-term trials are needed, Perelson notes. But the development of effective drug therapies requires a solid understanding of HIV's life cycle.

"Our hope to manage the disease over the long term depends on these numbers - we need to know how many viral particles are produced, where they are produced and how long the cells that produce them live," Perelson said.

The research appeared in the March 15, 1996 issue of Science.

Related information on the Internet

New Antiretrovirals

JAMA HIV Info.

HIV Replication Primer

Pathogenesis

YAHOO AIDS DIRECTORY