HIV vaccines may 'harm' patients

HIV vaccines being developed may do patients more harm than good, studies in mice suggest.

The latest findings strengthen concerns that the adenoviruses being used in some experimental HIV vaccines could speed up T-cell exhaustion.

This would mean a HIV-positive patient would progress more rapidly to AIDS.

Recombinant adeno-associated viruses (rAAV) have been used as vectors to carry selected elements of the HIV-1 virus and act as a vaccine. The latest research could explain why clinical trials into such vaccines have so far led to disappointing results.

It focused on rAAV vectors of different serotypes, all of which expressed HIV-1 gag proteins - essential for virus replication.

The vaccines were injected into female mice, which received a primer and a booster injection one to two months later.

Follow-up assays on immune response demonstrated that CD8+ T cells produced in response to the vaccine poorly protected from infection in a challenge model.

They also proliferated poorly when they came into contact with their antigen.

Additionally, only low levels of the cytokine interferon-gamma were produced in response to gag stimulation.

If an rAAV-vector vaccine against HIV dampens immune response in this way, it could increase the recipient's susceptibility to AIDS by removing their natural immune defences, say the study authors.

Lead researcher Dr Hildegund Ertl, from the Wistar Institute Vaccine Center in Philadelphia, said: 'The results mean that rAAV vaccines against HIV may cause harm and that, without additional preclinical studies, they should not be used in humans.'

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