HIV-1 Viral Load

M. Doherty M_Doherty at NIH.gov
Thu Mar 21 09:44:17 EST 1996

In article <4irggf$b88 at newsgate.dircon.co.uk>, infobase at dircon.co.uk wrote:

> Information/discussion is requested on the ability of viral load, as
> currently measured in HIV-1 infection, to acurately reflect the
> changes in viral population which may be expected under the influence
> of RT inhibitors, protease inhibitors, NNRTI's and combinations of
> these drugs.
> If these agents alter viral production so that defective or
> non-functional virions are produced, how would the current assays for
> viral load reflect that?
> If these agents alter viral production so that non-intact viral
> particulate matter is produced instead of intact virions, how would
> the current assays for viral load reflect this?
> Insight into these questions is crucial to ensure correct management
> of therapeutic decisions based on the viral load measure. Obviously,
> this measure is redundant if it cannot differentiate between
> functional and non-functional virions, or intact virions and particles
> of viral components. 

Most labs (at least those I work with) approach the problem from 2
directions - first to measure the production of viral specific RNA - this
tells you what is happening inside infected cels.  Second, assay the
ability of material produced to infect human cells - this tells you how
much of that viral message gives you active infective virus.  We use PCR
for the first method and infection of a CD4 line for the second - both are
very sensitive and thus give a very accurate picture of viral load.

The problem of course, is that viral load apparently varies greatly with
time and location, so a large number of timepoints and different biopsies
need to be taken to get an accurate picture of what the effect of any
particular treatment is.  Not an easy process!

Cheers, Mark

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