Possible step towards HIV vaccine

Tuesday September 20th, 2011

Scientists have made a discovery about how HIV attacks the immune system, saying this may help in the development of a vaccine.

Dr Adriano Boasso of Imperial College London, UK, and colleagues believe HIV causes the innate immune system to overreact, which weakens the effectiveness of the next line of defence, the adaptive immune system.

The virus uses the membrane of the cell it infects, which contains cholesterol. So the team investigated the effects of removing this cholesterol. They found it stopped HIV from setting off the innate immune response, allowing the adaptive immune system to mount a stronger response.

This shows that the series of events does indeed occur, that is, HIV overstimulates the innate response and that this weakens the adaptive response.

"HIV is very sneaky," says Dr Boasso. "It evades the host's defences by triggering overblown responses that damage the immune system. It's like revving your car in first gear for too long. Eventually the engine blows out.

"This may be one reason why developing a vaccine has proven so difficult. Most vaccines prime the adaptive response to recognise the invader, but it's hard for this to work if the virus triggers other mechanisms that weaken the adaptive response."

Without cholesterol, the virus is not infectious and cannot activate immune cells called plasmacytoid dendritic cells, but is still recognised by T cells.

"It's like an army that has lost its weapons but still has flags, so another army can recognise it and attack it," said Dr Boasso. His team are now investigating whether this inactivated virus could be developed into a vaccine for HIV.

Details of the study are published in the journal Blood.

A. Boasso, et al. Over-activation of plasmacytoid dendritic cell inhibits anti-viral T cell responses: a model for HIV immunopathogenesis. Blood, published online September 19, 2011.

Tags: Flu & Viruses | Pharmaceuticals | UK News

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