USS Clueless              Voyages of a restless mind

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Stardate 20011105.1800 (On Screen): Our immune systems have a form of memory, embodied in certain T4 cells. After they've been sensitized to a certain specific invader, they roam our blood seeking that invader and usually not finding it. But if they do, they begin to rapidly divide, generate antibodies to attack that invader, and generate a certain hormone which activates the rest of the immune system. As a result, you can only get a given viral disease once. There are, for instance, four kinds of measles viruses. Now there are vaccines for them all, but when I was young those vaccines didn't exist and it was routine for all kids to get all four of them -- and I have had them, and can never get them again because my body "remembers" them and is ready to fight. If I'm infected with one of those viruses, my immune system will react rapidly and kill it off before the viruses can cause me any harm at all.

So why do I seem to get a cold every winter? It's because each time it's a new disease. The ability of the T4 cells to recognize an invader is extremely specific; it takes very little change in the invader to evade previous detection and force a new round of recognition and sensitization. Adenoviruses are very mutable in certain areas and each year somewhere in the world some virus mutates and changes its antigens in such a way as to be different than before. This new strain then spreads all over the world, fostering yet another mutant somewhere, and so we all get sick every year. (Or at least it seems as if I do. I always get everything which is going around; I always have.)

The point of a vaccine is to pre-sensitize you to the antigen for a given virus (or something-else). In the case of a relatively stable virus like the four versions of measles, or smallpox, it's not too hard to make a vaccine and once given it (with a suitable booster schedule) you're fixed for life. But they can't vaccinate against adenoviruses because of this pesky mutability; even if they could make a vaccine for all the existing strains, they couldn't predict what new ones would pop up, and thus the vaccine wouldn't prevent them.

This article describes how a new form of HIV has appeared which is particularly mutable; this is obviously bad news. But while one reason it's bad is because of the stated fact that it may be able to develop resistance to the drugs used to suppress it, another reason is that HIV is already a virus which, like adenoviruses, has the ability to change its antigens. There are already many unique strains known which are sufficiently different to require separate vaccination, and there's every reason to believe that new ones will continue to develop -- and now, that they will develop at a much higher rate. I've always been skeptical about the prospects for an HIV vaccine; now I'm even more so. (discuss)

In the meantime, it seems as if it should be unnecessary to mention that having sex with a virgin won't cure you of HIV.