AEGiS-CATIE: Weakened vaccine still causes AIDS

Weakened vaccine still causes AIDS

TreatmentUpdate82 - Vol. 9, No. 8 - pp. 4-5; October 1997
Sean Hosein

Given the huge number of deaths due to HIV infection and the lack of a cure, many are calling for an increased focus on vaccine research. IAPAC (International Association of Physicians in AIDS Care) has recently begun a campaign to test a weakened HIV vaccine in people. IAPAC points to research on a similar vaccine using SIV, which causes AIDS in monkeys, that seemed to protect some monkeys from developing AIDS. However, long-term results from those experiments have found that a large proportion of vaccinated monkeys have become infected with SIV.

Latest results

Over the past 4 years, a team at the Dana-Farber Cancer Institute has vaccinated 18 monkeys with a live but weakened form of SIV called delta-3. At first, technicians could barely detect SIV in the monkeys' blood samples, but now four have high viral loads. One monkey has developed AIDS, while another's immune system shows signs of damage. The senior member of this research team has admitted that their vaccine clearly causes disease. Researchers at the Aaron Diamond centre in New York and others in the US and England have also seen vaccinated monkeys develop AIDS.

What went wrong?

In lab experiments when a gene called "nef" is removed or deleted from SIV, the virus becomes much less likely to cause disease. So researchers have made various SIV vaccines with nef deleted. However, when these weakened SIV vaccines were injected into monkeys, they still developed AIDS. It is not yet clear if the virus changed and became more aggressive or if the animals' immune systems could no longer "contain" SIV infection.

Back to the drawing board?

For now its back to the drawing board as the various teams try to create SIV that are even weaker than delta-3, yet still effective, in the hope that they won't cause AIDS in vaccinated monkeys. These experiments suggest that an effective human vaccine is still years away.

REFERENCES:

1.Cohen J. Weakened SIV vaccine still kills. Science 1997;278:5335:24-25.

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