Scientists have encountered unexpected success using a vaccine of immune cells to counter an HIV-like virus in monkeys.

HIV harms humans by destroying vital immune cells, leaving the body wide open to dangerous predatory infections.

The idea behind the vaccine is to prime the body's own immune system to cope better with the HIV assault.

While many vaccines are aimed at preventing illness by preparing an immune response in advance, this one might actually help patients who already have an established infection.

Alerting immune system

The research team behind the vaccine, from the Universite Rene Descartes in Paris, made the vaccine out of "dendritic cells".

These are immune cells which pick up bits of "foreign invaders", such as viruses, then present these fragments to aggressive immune cells so they can be recognised and attacked.

In this case, dendritic cells were taken out of the macaque monkeys, grown in culture and then treated with inactivated viruses - in this case "simian immunodeficiency virus" (SIV), the monkey equivalent of HIV.

When the treated cells were injected back into the monkeys levels of SIV in the blood fell dramatically, dropping to only a fiftieth of previous levels.

'Surprising'

In addition, levels of another key immune cell, CD4 - used as an indicator of the health of the immune system - rose after the vaccine was applied.

The beneficial effects were maintained throughout the study.

Dr Bruce Walker, of Massachussetts General Hospital, and an expert in HIV, said that the method could present a "major new therapeutic approach to HIV".

However, he said that the findings were "surprising" and needed to be repeated in other monkeys to be fully convincing.