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Report from CROI 2010
By Dr. Marianne Harris
The
17th Conference on Retrovirus and Opportunistic
Infections was held in February 2010 in San Francisco.
Researchers from the BC Centre for Excellence in HIV/AIDS
presented two important studies.
Dr. Mark Hull and colleagues performed an analysis of
the Canadian Observational Cohort Collaboration (CANOC)
cohort, a cross-Canada collaboration. They analyzed 1,674 HIVpositive
adults who received highly active antiretroviral therapy
(HAART) between January 2000 and December 2008. Study
participants had all achieved two viral loads below 400 copies/mL
in a row, and had six or more viral load results available over
the following two years.
Participants were classified into four groups: full suppressors—
all viral loads during follow-up were below 50 copies/mL;
transient viremia (detectable virus in the blood)—viral loads
below 50 copies/mL for at least 75 percent of the time, and
the remaining viral loads were between 50 and 1000 copies/mL;
short-term persisting viremia—viral loads below 50
copies/mL 25 to 75 percent of the time; and long-term
persisting viremia—viral loads below 50 copies/mL less
than 25 percent of the time.
Viral rebound was defined as having two viral loads in a
row—from two different tests—above 1,000 copies/mL—this is
usually accepted as a sign of treatment failure and indicates the
need to change antiretroviral therapy. The risk of viral rebound
was about the same for people with transient viremia as for the
full suppressors, suggesting that occasional low-level viral load
“blips” don’t predict ultimate treatment failure. On the other
hand, people with short-term persisting viremia were about six
times as likely to experience viral rebound as full suppressors.
Long-term persisting viremia was even worse—people with longterm
persisting viremia were about 20 times more likely to have
viral rebound than the full suppressors.
These results confirm that sustained suppression of the viral
load to below 50 copies/mL, at least 75 percent of the time
remains the ideal goal of successful HAART.
The second presentation showed that PWAs with undetectable
levels of HIV in their blood are less likely to transmit the virus to
others. Dr. Julio Montaner presented data showing an association
between the number of people receiving HAART in BC and the
number of new HIV infections diagnosed in the province.
HAART first became available in BC in 1996, and over the
next three years the number of people in the province newly
diagnosed with HIV decreased by nearly half—from about 700
in 1996 to about 400 in 1999. Over the next several years, the
number of British Columbians receiving HAART remained stable
at about 2,500. Then, between 2004 and 2009, there was
roughly a doubling of the number of people receiving HAART
to about 5,000. A significant drop in the number of new HIV
diagnoses in BC again followed this expansion of HAART coverage,
despite that fact that more people were being tested.
Of note, starting in 2007 there was a targeted effort to encourage
HAART use particularly among injection drug users (IDU) in
Vancouver’s Downtown Eastside. Over the next two years, the
number of new HIV infections in this population fell by about half.
Dr. Montaner acknowledged that there may be many factors
contributing to the decline in new HIV diagnoses in this population
and in BC in general, and that a significant proportion (estimated
to be about 20 – 25 percent) of people who are HIV-positive aren’t
aware of their diagnosis. However, these BC data provide the first
evidence of an association between the number of people receiving
HAART and the rate of new HIV infections within a large population,
even amongst the most vulnerable IDU group.
Details on these and other conference presentations can be
found at the CROI website at www.retroconference.org/2010. 5
Dr. Marianne Harris is a family doctor with the
AIDS Research Program at
St. Paul’s Hospital in Vancouver.
MayqJune 2010 living5 33