Sunday Times (Johannesburg) - October 15, 2008
Claire Keeton

Top researchers at the international AIDS Vaccine Conference 2008 today debated whether monkeys should be the "gatekeepers" for whether human clinical trials of new vaccines go ahead.

One of the strongest points from the "No" team, opposing the proposal of "non-human primates as gatekeepers", was that this would delay the process of testing vaccines in people.

David Weiner from the School of Medicine at the University of Pennysylvania, who helped to develop the vaccines against the rotavirus, cholera and malaria said: "We used humans quickly as far as we could."

He also made the point that macaques were an "imperfect model" for humans since they were different, in physiology and gut flora to name just two differences.

"Microbicides protected macques and they did not protect humans," said Weiner.

In contrast, Dr Paul Johnson from the Primate Research Center at Harvard Medical School, from the "Yes team" said that: "SIV/macaque models accurately mirror the course of HIV infection in humans."

He said: "Monkeys serve as a reasonable tool to predict immunogenicity (measuring their immune response)."

If primates have no response to an experimental vaccine, humans are not likely to respond either, argued Johnson, supporting the animal model testing as "an important screening tool" that could save millions of dollars.

Peggy Johnston, of the US National Institute of Allergy and Infectious Diseases, said the opposing teams had agreed that:

# Non-human primate models certainly are useful;

# Immunogenicity data in non-human primates for new vaccines should be taken into account;

# The decision to move forward cannot be based on monkey data alone; and

# Non-human primates are not appropriate gatekeepers for all vaccines.

Neither team argued that monkey data should block Phase I (first phase of testing the safety and efficacy) trials of new vaccine candidates for research going ahead.

The "Yes" team said such data could help prioritise which vaccine to choos, and they suggested a "low bar" (showing a vaccine offers some immunogenicity and efficacy against infection) to scale up to Phase II trials.

Jeffrey Lifson, from the "Yes team, concluded: "The real role for macaques as gatekeepers is not that you have to jump the bar but that you are forced to answer relevant questions."

In contrast, Jerald Sadoff fromt the "No" team stated that no decisions should be made from the results of non-human primate data as there is no valid model.

At the moment there is no effective vaccine against HIV -- which means there is no way of knowing if a vaccine would work on monkeys or not -- and thus no "validated model" in non-human primates, he stated.

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