Word: viruses
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...recent strategy, shown effective for the first time at NIAID, may be able to thwart this evasive action. Known as "prime-boost," it gives the immune system a whiff of the virus' scent before hitting it with the actual vaccine. In Nabel's lab, that whiff consists of a snippet of DNA from HIV's outer coating--not enough to trigger a full immune response but, as his work was the first to show in animals, enough to put the system on alert. In the past this strategy hasn't worked in humans because our immune system, unlike those...
Even this two-stage counterattack isn't always sufficient, however. When that's the case, it's time for the heavy artillery--the even more specialized cells of the acquired immune response. These cells learn from experience. Once they have been exposed to a virus or bacterium, they will recognize it if it shows up a second time. That's why, for example, you can get chickenpox once but rarely twice...
...scientists cannot crib from nature for vaccines, as Jenner did for smallpox. But that is changing as researchers get a sense of how many instruments in the immune-system orchestra they have at their disposal, and how to get the best performance from them. With HIV, for example, the virus mutates too rapidly. No sooner has the acquired immune system learned to identify and lock in on it than HIV develops new antigens on its surface and turns invisible again...
...early to know whether this strategy will work against HIV, but it is already working against another deadly virus. Ebola, though it has claimed far fewer victims than HIV, has enormous potential for devastation. There is no cure or vaccine for it--but in a recent trial, Nabel's group has shown that DNA priming can protect monkeys from Ebola...
...available for human trials for another decade, but once it is, Nabel and others plan to use every trick they have learned to boost its effectiveness. They may, for example, mix cytokines with the vaccine, counting on these chemicals to rally extra killer T cells against the virus. They may give a small jolt of electricity along with the priming dose of viral DNA; that shock seems to enhance the DNA's ability to trigger a response. And they are even experimenting with firing the DNA directly into immune-system cells at high pressure with so-called gene guns...