immune response against the virus to try to kill off as many viral particles and virally infected cells as possible, or they can sabotage the reproductive efforts of the virus so that no new particles are made.

Drugs that boost the immune system are similar to vaccines, and in many cases employ the same strategies, only they are administered after the person has become infected. In fact, some vaccines are being tested on people with AIDS to see whether they prolong the asymptomatic period or otherwise halt progression of the disease by boosting the immune response. In theory, all of the vaccines under development are potentially useful in treating people after they become infected or after they develop AIDS. In addition to the vaccines already discussed, which all seek to elicit antibody and killer T-cell production, scientists are also testing the possibility of giving antibodies directly to patients who are HIV seropositive and to those who already have AIDS. The problem with the antibody approach, say scientists, is viral mutability. If an antibody is given that helps the immune system kill off one viral variant, many more slip by undetected. Most scientists are coming to the conclusion that the most effective antiviral strategies combine many different activities. In other words, therapeutic approaches of the future may well combine drugs that boost the immune system with ones that inhibit viral replication.

A New Generation of Drug Treatments

The general hope is that a new generation of drugs may help extend the asymptomatic period from 10 to 30 years or more. While this is not as desirable as completely eliminating the virus from a person's system, it will allow an HIV seropositive individual to enjoy a longer disease-free life and may also limit the severity of any symptoms should they develop.

Antimicrobial drugs each work differently, but they all share the same fundamental goal—to sabotage the biochemical machinery that produces the progeny of the infecting microogranism. Since each machine is different, each therapeutic monkey wrench must be tailor-made to the machine it is trying to inhibit. A big problem in drug development, however, is that the host cellular machinery is often very similar to the machinery used by the replicating virus or bacteria. In fact, viruses are heavily dependent on the host cell's machinery to carry out their reproduction. So drug developers walk a tightrope trying to find agents that harm specifically microbial machines but that leave cellular machines intact. To the degree that drugs fail to be specific for their microbial targets, they cause side effects. Sometimes a drug that is very



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