Can a ‘vaccine’ based on HIV’s coat protein gp160 help to slow progression
to AIDS in people infected with the virus? Robert Redfield, from the Walter
Reed Army Institute of Research near Washington DC, thinks the answer is
yes. His results, presented in Amsterdam, drew a mixture of scepticism and
wary optimism from his peers
Redfield has been studying a group of about 30 infected volunteers who
have received the protein as an immune therapy, in a preparation made by
the American company MicroGeneSys. The men were inoculated between two and
three years ago. Redfield says that most of the men produce new T cells
and antibodies against the virus. Natural infection with HIV does not stimulate
this response. The levels of their CD4 T cells also stabilise, he says.
More surprisingly, Redfield says, the levels of HIV’s genetic material in
the bloodstream drop, indicating that something is reducing the amount of
Redfield is also enthusiastic that the antibodies the men produce in
response to the vaccine ‘recognise’ a wide range of strains of HIV. A larger,
controlled trial of the immune therapy began last winter
Daniel Hoth, from the National Institutes of Health in the US, was cautious.
‘I think the results are extremely interesting,’ he said. ‘What is unknown
is whether they are clinically meaningful.’
Scientists warn that the study may not have gone on long enough to show
whether the effects are lasting, and that the changes in the levels of T
cells may not be significant. Some suggest that the virus that appears to
be removed from the bloodstream may simply be shifted elsewhere, into the
lymph nodes for example. Redfield thinks this is unlikely
The MicroGeneSys preparation is made in genetically engineered insect
cells. The engineered gp160 protein is unfolded, unlike the real thing.
Hoth says it is therefore ‘completely predictable’ that the protein will
look different to the immune system and stimulate a different response
Hoth is also cautious about the ideas of Jonas Salk, who wants to develop
a vaccine that triggers only T cells, not antibodies (This Week, last issue).
‘All of this remains a hypothesis,’ he says.