Agence France Presse (11.30.11) - Thursday, December 08, 2011
Results of a laboratory test on mice may open a promising new
path toward a vaccine against HIV, an approach scientists call
"vectored immunoprophylaxis" (VIP).
Researchers have been searching for "broadly neutralizing
antibodies" (bNAbs) from among the small number of people with
an innate ability to resist HIV. So far, this has turned up
about 20 bNAbs, but there are unknowns about how they work and
whether they can be made vaccine-deliverable.
The research team, led by David Baltimore of the California
Institute of Technology (Caltech), said it has developed a way
to deliver bNAb-making genes in lab mice genetically modified
to be susceptible to HIV infection. Using the VIP approach,
the team injected a harmless adeno-associated virus into the
leg muscle of mice, where it entered cells and expressed bNAbs
The mice were then injected intravenously with one nanogram of
HIV, enough to infect most unvaccinated mice, and even
eventually 125 nanograms. "We show that humanized mice
receiving VIP appear to be fully protected from HIV infection,
even when challenged intravenously with very high doses of
replication-competent virus," the authors wrote.
VIP is "like gene therapy, but distinct," said Baltimore. VIP
took up residence in the muscle tissue but did not slot genes
into the mouse's DNA code, he explained. "It's not an
'insertion' but a free plasmid-like element that will exist in
muscle cells," he said.
The researchers stressed that the jump from mice to humans is
large. "We're not promising that we've actually solved the
human problem," Baltimore said. "But the evidence for
prevention in these mice is very clear."
Baltimore was co-winner of the 1975 Nobel Prize for Medicine
for his work on reverse transcriptase, a key enzyme in the
replication of retroviruses, the family which includes HIV.
Results of the study, "Antibody-Based Protection Against HIV
Infection by Vectored Immunoprophylaxis," were published in