AIDS vaccines: New hope for problem-plagued path
10 November 2008
3 days ago
PARIS (AFP) — A strategic tack in the quarter-century-old effort to devise an AIDS vaccine, which last year became darkly clouded by problems, could be more promising than thought, according to a study published on Sunday.
Research — among lab primates, not humans — shows that a vaccine based on priming “killer” T-cells, the heavy artillery of the immune system, can work, its authors said.
This approach was massively hit by the failure last year of what seemed a highly promising candidate, a prototype called V520 developed by the US pharma giant Merck.
V520 used a modified form of a virus for the common cold as a “Trojan horse” to deliver elements of the human immunodeficiency virus (HIV) into the body to prime the immune defences.
The new research, carried out among rhesus monkeys, likewise uses a cold virus to deliver the vaccine.
But unlike the Merck vaccine, it proved emphatically that T-cells could be marshalled into action to tackle simian immunodeficiency virus (SIV), a close cousin to HIV.
When injected with a lethal dose of SIV, monkeys were able to brake replication of the virus and remained healthy for more than 500 days after infection.
T-cell vaccines are not of the preventative kind, like the vaccines for polio or smallpox, which have become famous for shielding us against microbial infection.
Instead, they are “therapeutic” vaccines, meaning that they train killer T-cells to fan out on a search-and-destroy mission after infection, slaughtering enough infected cells to keep the viral invaders in line.
AIDS first emerged in 1981. Swift progress in identifying the virus that caused it unleashed early optimism that a vaccine would quickly emerge.
Out of the 50 candidates that have been evaluated among humans, only two vaccines have made it through all three phases of trials, and both were flops.
About 30 vaccines remain in the pipeline.
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Read full article at AFP
