Dying so we might live
Protesters are up in arms over experiments that give
Does the prospect of developing an effective AIDS vaccine
justify condemning chimpanzees to death? That's the stark question
dividing biomedical researchers in the US, now that virologists know
that some strains of HIV cause the same fatal illness in chimps as
they do in people.
Already, several chimps have been
deliberately infected with HIV strains that can kill them. And the
researcher who discovered that chimps can develop AIDS plans to
expose up to four more animals to his lethal virus.
experiments could be the prelude to vaccine experiments involving
larger numbers of apes. That prospect has outraged animal welfare
campaigners-and many researchers. No scientist would infect a person
with HIV deliberately, they point out. Being our closest living
relatives, they argue, chimps should be treated with similar
"You can compare a chimp to a mildly retarded
child. Just because it's mildly retarded doesn't mean you abuse it,"
says Alfred Prince, a virologist at the New York Blood Center. Along
with 11 other scientists, he has sent a letter to the journal
Science raising ethical and scientific objections to the use
of lethal HIV strains in chimps. Another of the signatories is
primatologist Jane Goodall, famous for her studies of wild chimps in
Chimps are no longer used in research in many
countries, including Britain and Australia. But in the US, more than
100 of the apes have been infected with different strains of HIV
since the early 1980s. Until recently, it seemed that HIV never
causes AIDS in chimps. This meant that chimps fell from favour as an
animal model for AIDS research and limited the controversy
surrounding the experiments.
But that all changed in 1997,
when Frank Novembre of the Yerkes Regional Primate Research Center
in Atlanta reported a single case of HIV causing AIDS in a chimp
(Journal of Virology, vol 71, p 4086). Since then, the virus
responsible has been deliberately passed on to a handful of other
chimps. None of these animals has yet developed AIDS, but some have
extremely low levels of CD4 cells, the white blood cells that are
destroyed by HIV. This suggests that it is only a matter of time
before they become sick and die.
"The good news is that we
now have a pathogenic HIV model in a chimp," says Alan Schultz, head
of preclinical research in the AIDS vaccine programme of the
National Institute of Allergy and Infectious Diseases (NIAID) near
Washington DC. "The bad news is that to do meaningful vaccine
experiments, we will have to put chimps' lives at risk."
NIAID is now funding Novembre to expose up to four more chimps to
lethal HIV strains, with the aim of working out the smallest dose
needed to establish an infection via the rectum. Novembre and
virologist Patricia Fultz of the University of Alabama at Birmingham
have already exposed chimps with good immune responses to less
virulent strains of HIV to one of the new aggressive strains. The
existing infection appeared to offer some protection.
for a vaccine that can completely prevent HIV infection are fading,
however, so attention is shifting towards vaccines that might slow
the progression to AIDS. These could be tested in chimps infected
with the lethal strains. The alternative-going straight into tests
on people with HIV-is complicated by the widespread use of
anti-retroviral drugs, which also delay the progression to AIDS.
This would make it difficult to distinguish the effect of the
vaccine from that of the drugs.
Fultz argues that terminal
experiments involving chimps are a necessary evil. "With 40 million
people infected in the world, there is a great need for a vaccine"
But Prince claims the chimp experiments are
flawed. The virulent HIV strains are more aggressive than the
strains that usually infect people, he says, so potentially
effective vaccines could get overlooked. Fultz disagrees: "The
strain I have is very much like HIV in humans."
of the scientific arguments, however, many people would oppose the
experiments on ethical grounds-particularly in the light of current
efforts to grant legal rights to chimps and other great apes (This
Week, 13 February, p 20). Prince hopes his letter to
Science will provoke sufficient public outcry to prompt a
moratorium on potentially terminal AIDS experiments involving
From New Scientist, 20 February