HIV has been one of modern medicine's most implacable foes. Thirty one years since AIDS was first observed in the west with 30m deaths worldwide since, it has been tamed but not beaten.

However, now scientists are beginning, cautiously, to talk about the virus, HIV, that gives rise to AIDS, in terms of a cure.

The Today programme's science correspondent Tom Feilden reports on how a new generation of vaccines that focus on the fundamental elements of the virus that can't change are generating a new mood of optimism amongst researchers.

Jonathan Weber, from Imperial College and chair of the UK wide AIDS vaccine programme, explained to Today presenter Evan Davis that now scientists are daring to hope that the disease might be ultimately be defeatable.

There is now "cautious optimism" among scientists, Mr Weber explained.

"It might actually be possible" to develop a vaccine, he added.

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