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HIV/AIDS Vaccine To Begin Phase I Human Trials
An anonymous reader writes "An HIV/AIDS vaccine developed in Ontario has applied for Phase 1 human trials. Safety and immunogenicity studies of the vaccine, dubbed SAV001-H, have already been completed on animals. Phase 1 human trials will check the safety of the vaccine on HIV positive volunteers. Phase 2 will then test immunogenicity."
The question is really if this is a vaccine or therapeutic vaccine, I couldn't find that in the article. The difference being a regular vaccine will prevent the virus from infecting you while a therapeutic will either prevent the virus from spreading in your body but you might still be a carrier or eradicate the virus from you completely thus destroying it.
Just a side note since a lot of discussion on HIV and AIDS. HIV is the virus, the virus attacks the immune system destroying your white blood cells, when your white blood cell count falls below a certain amount per 1mm of blood or some measurement you have AIDS or auto-immune deficiency syndrome caused by HIV.
The virus wont kill you, what will kill you in the end is a basic infection that your body cant handle, even the common cold.
Don't get too excited. A few other promising AIDS vaccines have made it this far. Phase I testing is just testing for safety, not effectiveness. Phase II testing is for effectiveness, and phase III testing is for effectiveness in a larger population. VaxGen's vaccine made it to Phase III before it turned out not to be very effective. 95% of the new drugs that make it to the beginning of testing in humans don't turn out to be useful.
This is a phase one trial, which doesn't test whether it works, it tests whether it is harmful. The vaccine will be administered to a number of people who already have HIV to see if they have any adverse reaction to it. Presumably the next phase of the trial will be to give it to some people in high-risk demographics and see whether any of them still manage to contract HIV. If they do, then the vaccine doesn't work, although if a smaller number of them contract the disease than would be expected to statistically then it may be worth bringing to market anyway. The final stage will almost certainly involve injecting someone who has been vaccinated with blood from an HIV-positive patient to see whether it really works.
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A few points;
1: While you can inject the HIV virus into other animals, the virus will not enter their cells due to the variations between human CD40 and the animals' copy. They can get the virus in them, but it won't do anthing.
2: There are animals whose cell surface ligands are similar enough to the human ones that the virus *does* infect them. if I recall correctly, HIV is capable (though much less efficiently) of entering the cells of certain apes, cats, and armadillos (an eclectic combination to be sure).
3: Of those animals that will play host to the virus, none of them develop symptoms of AIDS. They will host the virus, spread it around, but will not suffer immunoinhibition. This really isn't that uncommon; humans carry several viruses with no measuarble histological effect. This means that there are no suitable animal models for vaccine testing; human testing really is the only viable option.
4:It has long been theorized that the difference between being HIV positive and having AIDS is merely the amount of virus spreading in the system. i.e. if you can keep the viral load low enough, you won't get AIDS. If this is indeed the case, then even a therapeutic vaccine will be a huge step forward in the mortality rates of those infected.
5: Yes, HIV mutates quite quickly. For this reason, the approach that has long been favored is a competitve virus that targets the same cell types as HIV, yet does not have the same level of virulence (a latent infection rather than an actively spreading one). This is the same strategy employed with polio; the original polio vaccine was an actively spreading infectious virus that simply didn't cause the same disease symptoms. It also spread from person to person just like the disease it was meant to treat. This "similar but safer" strategy is likely the only way to have the 'treatment' evolve quickly enough to keep in step with the target. This is also the most difficult type of vaccine for which to acquire testing approval (for obvious reasons).
6: Other vaccine types are much less likely to be effective against a quickly mutating target like HIV. While they may prime the immune system effectively enough against a single strain of the virus, it's much less likely to work against other strains (same reason that you have to get the flu shot every year rather than just once).
7: It was recently shown that HIV can spread through cell:cell junctions. This being the case, it is unlikely that typical vaccines (other than live virus) will be effective, because there is no chance for antibodies (the typical immune system mediator) to interfere in this infection process. Now, it is unlikely that cell:cell spread is sufficient to get viral load to the point of causing AIDS, but it is still a factor to be considered when making predictions about vaccine efficacy (viral clearance is extremely unlikely).
8: This is a phase 1 trial. It's a small scale trial where they're testing for toxicity, not efficacy (phase 2/3). In other words, this trial is designed to answer the question, "is it safe?" It will not answer the question, "does it work?"
HIV mutates a lot, but a whole lot of that is thought to be stochastic mutation. The most basic version of this would be where type A becomes type B, but type B also mutates back into type A just as fast, so after a few dozen generations, the population reaches an equilibrium, half of each type. The point is, it's not evolutionary mutation - you have the random mutation part, but until there's some sort of selection pressure, you don't have evolution. There's a difference between having to deal with non directed mutation (which is what stochastic means in this context) and actual evolution. HIV mutates a lot - HIV is NOT evolving rapidly.
HIV appears to have four types (in this case, of outer protein coats) which are usually called A, B, C & D, but again, nothing is selecting for one type over the others and there's theoretically no pressure for HIV to evolve because of this particular mutation. Some flus have a lot more than four types. Right now, the swine flue that has people worried is type H1N1, and there are six or seven types just for the N part of that classification, and maybe 30 or so total type combinations possible.
A highly effective vaccine in this case would probably require it make the body's immune system target some part of HIV's protein coat that doesn't usually mutate, just so it doesn't have to fiddle around dealing with the cycle of forward and backwards mutation.
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