VANCOUVER, BC--The new understanding of the importance of viral
dynamics in the progression of HIV infection (see "New Thinking
on HIV Progression Leads to New Strategies") has led to new
guidelines for deploying drugs now available to treat HIV (a list
of available agents is on page 13). Experts now recommend reducing
viral load to below detectable limits, as an indication that viral
replication has been curtailed as much as possible.
This is important for two reasons. The first is to reduce the
number of new cells being infected and destroyed by HIV. The second
is to spike one of the virus's main weapons: its ability to mutate
and become drug-resistant. Less replication means fewer new virions,
which means fewer mutants.
In his presentation at the 11th International Conference on AIDS,
Paul Volberding, MD, director of the AIDS Program, San Francisco
General Hospital (SFGH), translated this into practical terms
as "response-optimized HIV therapy" (see table ).
At SFGH, antiviral treatment is recommended for all patients with
viral load greater than 5,000 to 10,000 copies of viral RNA per
milliliter of plasma, regardless of CD4 cell count. In those with
viral load over 5,000 to 10,000 and CD4 counts of 350 to 500,
recommended treatment is two nucleoside analogs plus a protease
inhibitor, if needed, to reduce viral load to less than 10,000
"If the baseline viral load is 50,000/mL or less, use of
two nucleoside analogs may lower it to 5,000 to 10,000,"
he said. "If viral load is 50,000 to 150,000, you may be
able to get down to that threshold by adding a protease inhibitor."
The 5,000 to 10,000 copies/mL guideline was based in part on the
limits of tests used to measure viral load. Newer tests have reduced
that threshold to 100 to 500 copies/mL, and third-generation tests
now used in research detect 10 to 20 copies/mL, allowing testing
of the hypothesis that reducing the viral load to below that level
could result in long-term "cure" of the disease (see"
Early Combination Treatment May Provide HIV Control" for
a report of ongoing tests of this hypothesis presented in Vancouver).