Maternal Transmission and Viral Load

One important paper was overlooked at the Surrogate Markers
meeting; it had been presented the week before, at the ICAAC
(Interscience Conference on Antimicrobial Agents and
Chemotherapy) conference in Orlando, Florida. It was one of
the "late breaker" presentations at ICAAC -- meaning that the
results were available too late for regular submission, and
therefore were not published in the abstracts which were
distributed prior to the conference. As a result, an
important finding did not get immediate attention.

This study was directed by Barbara Weiser, M.D., and Harold
Burger, M.D., co-directors of HIV research at the New York
State Department of Health's Wadsworth Center in Albany, New
York, and including investigators at other medical centers in
New York and New Jersey. It measured the plasma HIV RNA
levels in 27 mothers at the time of delivery. Eight of the 11
mothers with the highest levels of HIV RNA (greater than
175,000 copies per ml of plasma) transmitted HIV to their
infants; but none of the 16 mothers with lower viral load
transmitted HIV. This result was strongly statistically
significant (p<.001).

The researchers had already published a paper in which they
used quantitative viral cultures, instead of plasma HIV RNA,
to measure viral load in the mothers' blood. The viral
cultures worked less well; one mother with a low level and
three with a mid-range level (in the viral culture tests) had
high levels of HIV RNA, and did transmit the virus.

The researchers concluded, "These data identify HIV-1 plasma
RNA level as a major determinant of mother-to-child
transmission and provide a strong scientific rationale for
implementing multiple strategies to interrupt transmission by
reducing viral load."

This work was funded by the Pediatric AIDS Foundation, and
the U.S. National Institutes of Health.