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Universal influenza vaccine, maybe – eternal, maybe not

Universal influenza vaccine, maybe - eternal, maybe not

Having a “one-shot” vaccine that prevents all strains of influenza, present and future, is an ideal toward which many scientists (including several at Stanford) are working.

The reason we have to get immunized against influenza every year is that evolution outwits technology. Specifically, the particular spots on the influenza virus our vaccines happen to target – molecular “hooks” that grab onto particular sites on our cells’ surfaces, letting the virus clamber inside – keep changing their shapes from year to year, just enough to foil our vaccines.

Each variant, or strain, of influenza virus requires its own vaccine, thus forcing global health authorities to make educated guesses as to what strains are likely to emerge or recur several months hence, giving vaccine manufacturers time to ramp up supplies well in advance of the next season’s inevitable epidemic. (Each shot in the arm is actually several vaccines in one, because it immunizes against several influenza strains.)

Now researchers at Mount Sinai School of Medicine report, in the inaugural issue of the open-access, peer-reviewed online journal mBio, that they have created an influenza vaccine that appears to work against every known flu strain. They did this by producing a vaccine that sensitizes our immune systems to a different part of the virus from the ones we normally produce responses to. Instead of the “head” (a bulbous portion of the viral molecule containing the standard cell-attachment hooks), the experimental vaccine targets a spot on the viral molecule’s “stalk.” That stalk-specific spot appears not to vary from strain to strain – or, by extension, from year to year.

Well, not yet, anyway. Picture the viral-particle’s stalk as a neck on top of which sits a big fat fleshy head. Moreover, there’s an odd-shaped mole on the neck. That’s the spot the new vaccine targets. But our immune systems normally never see the mole because of the flabby jowls that droop down like drapery in front of it, obscuring it.

Now imagine a vaccine (as the Mt. Sinai investigators seem to have succeeded in doing) that can sensitize the immune system to the mole. If things go well, the immune system responds by producing a new set of antibodies that can insert themselves in that unwashed (unwatched, anyway) zone twixt head and neck, find the mole, and cling to it. The antibodies’ presence at that unsightly site summons microbe-gobbling immune cells, which come in and finish the virus off.

Trouble is, a likely reason that viral “mole” hasn’t been mutating is that there’s never been any evolutionary pressure for it to do so. Time will tell whether aiming for a hitherto hidden target on the influenza virus will up the ante, forcing new evasion maneuvers that once again defeat our vaccines, or whether this time the jig is up.

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