Having problems with message search?
Treatment and Prevention
Exchange Vows at International Conference
Jon Cohen
Science 15
August 2008:
MEXICO CITY--AIDS
researchers have long argued that HIV prevention and treatment efforts should
go hand in hand, but they rarely do. Their fickle relationship received intense
scrutiny at the XVII International AIDS Conference held here last week.
"They keep going to the altar," said Myron "Mike" Cohen of
the University of North Carolina (UNC), Chapel Hill, in a plenary presentation.
"They never get married. They have to get married today."
More
than 20,000 researchers, health care workers, representatives from hard-hit
communities, and activists attended the conference, which had never been held
in Latin America before. The meeting ran 3 to 8 August, and about one-fourth of
the participants came from the region.
As
usual at these gatherings, science shared the limelight with diverse issues
such as scaling up access to anti-HIV drugs, the increasing criminal
prosecution of people who infect others, and the need for countries to address
their epidemics in ostracized groups. Protests were more muted than in past
years, although several added a novel Latin American spice to this conference
staple.
New
research findings were fewer and farther between than ever, creating the sense
that the meeting has evolved into a giant review paper rather than a place for
colleagues to share their latest data. "This is more a world AIDS summit,
where every 2 years we reexamine everything we know," said Julio Montaner,
the new president of the International AIDS Society (IAS), the meeting's
organizer.
Cohen
was one of several presenters who stressed that the great gains in treatment
have overshadowed prevention needs. Today, 3 million people in low- and
middle-income countries receive anti-HIV drugs, but an estimated five people
become infected for every two on treatment. "There has not been that push
for prevention as there's been for treatment," said Peter Piot, head of
the Joint United Nations Programme on HIV/AIDS. "If we thought the first
phase was hard, we have to prepare for even tougher times."
Piot
also noted that the characteristics of the epidemic keep changing in different
locales, urging countries to "know their epidemics" and target
prevention to the most vulnerable groups. In Thailand, where the epidemic has
been concentrated among injecting drug users and sex workers, married women now
account for more new infections than any other group. In parts of sub-Saharan
Africa, where epidemics have been primarily driven by heterosexual sex,
injecting drug use is an increasingly important mode of spread. China, which
has a large number of infected injecting drug users, today has a growing
epidemic in men who have sex with men. In the United States, infections of
whites peaked in the mid-1980s; blacks now account for 45% of the new
infections and have an eight times higher risk of becoming infected, according
to new estimates published by the U.S. Centers for Disease Control and
Prevention (CDC). "The end of AIDS is nowhere in sight," said Piot.
|
Efficacy Trials
of Biomedical Prevention |
||
|
Intervention |
Completed |
Effective |
|
Male circumcision |
3 |
3 |
|
HSV-2 suppression |
2 |
0 |
|
Bacterial STI |
5 |
1 |
|
Cervical barriers |
1 |
0 |
|
Microbicides |
9 |
0 |
|
Vaccines |
4 |
0 |
|
Total |
24 |
4 |
Little success. This
prevention scorecard shows a stark
bottom line for pills, shots, gels, and
diaphragms.
SOURCE:
JUDITH WASSERHEIT/UW, NANCY PADIAN/UCSF
The success with
combinations of potent anti-HIV drugs, which reduce the amount of virus people
carry and make them less infectious, has led to the increasing awareness that
treatment is prevention, both for individuals and populations. But the
degree to which the drugs can prevent infections has proved highly contentious.
A
statement issued by the Swiss Federal Commission for HIV/AIDS in January on
this topic served as a lightning rod. After reviewing the scientific
literature, the Swiss commission concluded that a heterosexual person faced
virtually no risk of becoming infected by having unprotected sex with an HIV-infected
person on continued treatment, provided that person had undetectable levels of
virus in the blood for 6 months and no sexually transmitted infections. The
statement stopped short of explicitly discounting the value of condoms, but
many thought that was its implicit message.
"There's
condom absolutism, and everyone who questions it is put into controversy,"
said Bernard Hirschel, who heads the HIV/AIDS program at the University
Hospital, Geneva. The main aims of the statement, he said, were to tell "discordant"
couples--in which one is infected and the other isn't--who met these criteria
that they could safely try to have children and also to combat a Swiss law that
says an HIV-infected person who has sex without a condom can be held criminally
liable, even in the absence of infecting a consenting partner.
Kevin
De Cock, head of HIV/AIDS for the World Health Organization, and others blasted
the statement as irresponsible. "It just doesn't seem like a cautious
public health recommendation," said De Cock. "I don't think anyone's
shown the threshold below which people cannot transmit."
A
model published in the 26 July issue of The
Lancet by David Wilson and colleagues at the University of New
South Wales in Sydney, Australia, further emphasized the dangers. The study
devised a mathematical model to compare 10,000 discordant couples that had
unprotected sex for 10 years with the same number of couples who used condoms
80% of the time. The risk of transmission increased four times in the
unprotected group because of occasional viral rebounds that happen to people on
effective treatment.
Also
hotly contested was the degree to which ongoing treatment can prevent
transmission on the population scale. IAS President Montaner, a researcher at
the University of British Columbia, co-authored an article in the 1 July issue
of the Canadian
Medical Association Journal that contends that potent
treatment led to a decrease in HIV's spread in British Columbia. Specifically,
their study notes that new HIV infections dropped about 50% in British Columbia
from 1995 to 1998, the years when highly potent anti-HIV drugs first became
available. During the same years, syphilis infections increased, suggesting
that the drop was not due to condom use or other behavioral changes. "Antiviral
therapy greatly lowers infectiousness," contended Montaner.
But
epidemiologist Geoffrey Garnett of Imperial College London countered that
antiretroviral drugs are unlikely to make a large impact on transmission on a
global scale. Roughly 80% of infected people do not even know their status. Of
those who do, most are not eligible for free treatment until their immune
systems have been substantially damaged--which means most transmissions occur
long before people are taking the drugs.
Garnett
and others encouraged their colleagues to embrace the notion of
"combination prevention." No currently available intervention can by
itself turn an epidemic around, but by combining treatment with preventive
measures such as condoms and circumcision, it may be possible to create "a
natural synergy," Garnett said. "Rather than arguing for a single
magic bullet, we really need to be trying to focus everything that we can on
what works to realize these natural synergies."
The
growing enthusiasm for combination prevention in part reflects the dispiriting
fact that the vast majority of biomedical prevention studies, from large human
vaccine trials to microbicides to treatment of sexually transmitted diseases,
have failed (see table). Still, many investigators have high hopes for what
could be something of a magic bullet: pre-exposure prophylaxis (PrEP), which
gives anti-HIV drugs to uninfected
people. The idea is that people at high risk of infection will take the drugs
shortly before having sex, much in the way that people take antimalarial drugs
before visiting countries where that disease is prevalent. Studies around the
world are now enrolling more than 18,000 people to test this concept--more than
the number of people in AIDS vaccine trials, noted Mitchell Warren, head of the
AIDS Vaccine Advocacy Coalition in New York City. UNC's Cohen predicted that
PrEP, similar to the successful strategy used to prevent transmission of HIV
from an infected, pregnant woman to her baby, "is almost certain to
work."
The
approach has had remarkable success in monkeys. Walid Heneine of CDC in
Atlanta, Georgia, described experiments in which he and his colleagues inserted
anti-HIV drugs into the vaginas of six monkeys and then 30 minutes later tried
to infect the animals with vaginal infusions of an engineered AIDS virus. None
of the animals became infected after 20 such "challenges," whereas
seven of eight untreated control animals did.
Anthony
Fauci, head of the U.S. National Institute of Allergy and Infectious Diseases
in Bethesda, Maryland, said PrEP may lead to protection in more ways than one:
The drugs prevent infections by killing or weakening the AIDS virus, which
could trigger immune responses that subsequently derail infections. "That
may be the first vaccine," said Fauci.
It's time to go back to school!
Get the latest trends and gadgets that make the grade on AOL Shopping.
Offline 
Send Email