Anticipating the Flu Virus

If the announcement had been made almost anywhere else, it would probably have been dismissed as one more false alarm. But the word came from the Pasteur Institute in Paris, fons et origo of epochal research into man's relationship with the microbes: Institute scientists had devised a vaccine to protect against the present generation of influenza virus and against generations yet unborn. The vaccine, said last week's announcement, will be available almost immediately.

The flu virus is notorious for its frequent mutations. About every ten years, on the average, the transformation is so marked that the antibody system of a person who has been infected with the most recently prevalent strain, or vaccinated against it, does not recognize the new one. So he has no immunity.

In 1957 and 1968, no one was immune to the radically different "Asian A2" and Hong Kong strains that erupted in those years. The Pasteur scientists do not claim to have anticipated such a major mutation. But in between such large alterations, the virus undergoes a process called "antigenic drift," in which subtle changes occur in the virus' protein overcoat. The now prevalent London flu strain represents one of several such minor changes in the basic Hong Kong virus of 1968, and generally available vaccines are only 50% effective against it.

Forced Evolution. Until now, a vaccine to combat a newly evolved strain could be prepared only after the event (TIME, Aug. 21). Ideally, as Professor Claude Hannoun explained it, scientists would like to anticipate all the antigenic changes that nature might make in the next few years in the virus' protein coat. But how to anticipate nature? That would require capturing all the Hong Kong derivative strains now available, growing them in the laboratory and attacking them with different types of antibody. Most would be neutralized, but in this artificial equivalent of the Darwinian process of natural selection, a few mutant strains would survive because their protein coat patterns differ from those of earlier strains. If, as is almost certain, the survivors share a certain characteristic--what virologists call a common antigen--it should be possible to make a vaccine which would protect against that antigen and therefore against all such strains.

Hannoun reported that by using a technique devised by Australian Immunologist Fazekas de Saint Groth, his research team had artificially caused such mutants to evolve. He was confident that they had anticipated all the minor changes that nature could produce in the next five years. Thus, he claims, they have produced a vaccine effective against all strains that may develop naturally from now until about 1978. Samples prepared before the London flu strain emerged, he said, had proved 84% effective in tests on human subjects.

Raised Brows. To protect its patent rights, the self-supporting Pasteur Institute has not yet documented its find in scientific publications. Partly for that reason, some scientists still kept their eyebrows raised. How, they asked, could anyone be certain that he had anticipated all the mutants that resourceful nature might produce? It may take five years, they concluded, to prove the institute's claim that this was indeed a "revolutionary discovery."

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