Page #21
MA: So we have seen that some viral infections are fought rather succesfully using vaccines and some are not.
Do you know of any other problems with vaccines?
Q: I remember the dust-up about there being mercury in some vaccines.
MA: Yes some vaccines do contain Thimerasol, a mercury-containing preservative. However, there is no hard evidence that this product causes autism - and that is what has been claimed. But I do believe that children under 5 or 6 are often given Thimerasol free vaccines if possible, but my information might be a bit dated.
It is another aspect of vaccines that I would like to make you aware of and especially with the coming flu season.
Q: And what is that?
MA: It is a phenomena called antibody-dependent enhancement.
As we discussed this winter the majority of viral infections of animals and man are not fatal, but are followed by recovery and the development of a state of relative or absolute resistance against re-infection with the same virus.
Much of this resistance can be attributed to specific antiviral antibodies, although cellular immune mechanisms also contribute to the protection of the host.
However not all antiviral antibodies are necessarily virus neutralizing antibodies - in addition to these virus neutralizing antibodies or non-neutralizing antibodies a further group of antibodies exist: antibodies which enhance the infectivity of the virus.
This phenomenon is known as antibody-dependent-enhancement (ADE) of viral infectivity and has been observed with various macrophage-infecting viruses.
The common features of viruses exhibiting ADE are:
1. preferential replication in macrophages
2. ability to establish persistence
3. and antigenic diversity
Q: That's odd. How does it work?
MA: ADE occurs when the host is more efficiently infected by a combination of virus plus antibody than by the virus alone.
Can you see that?
Q: Yea, I guess. But it seems strange that an antibody would aid the virus in infection.
MA: Child, nothing in the world of Virology is strange. Let's go back to our favorite subject the HIV virus for a moment.
Page #22
MA: A recent article explains that a vaccine trial for HIV was stopped prematurely in September 2007 due to evidence that vaccinees may have been more susceptible to HIV infection than the placebo given control group.
This is very important - do you understand what I just said?
Q: Yes, they were trying to find a vaccine for AIDS and when the tried the experimental vaccine they had to stop the trials because the vaccinated subjects were acquiring AIDS faster than the control group. That not only seems Greek to me but a bit out of the way, as related to our discussion of the novel H1N1 virus.
MA: But it is central to our conversation. Some cells do not have the usual receptors on their surfaces that viruses use to gain entry. The antibodies bind to antibody Fc receptors that some of these cells have in their plasma membrane. The viruses then bind to the antigen binding site at the other end of the antibody - thus enhancing the infection.
So it is possible for antibodies to a virus to acctually enhance the ability of the virus to infect the host. That is why when you challange any host with either a virus or vaccine, you must be certain that the results are overwhelmingly positive. We must always look at the pitfalls that might appear in the very near future. It is kinda what they pay us for.
Q: OK, it's just that I don’t really get the problem yet. I understand that there is an inherent danger in giving new vaccines to large numbers of people. As you point out - sometimes these things can backfire. But do you really anticipate a problem with the flu vaccine - whatever that may be?
MA: No I don't, but as we started this conversation last summer - it is often the results that you do not plan for that are the most damaging.
Q: I don't understand?
MA: I did not expect you to - yet. We have discussed how influenza is spread, how it replicates, how it can be inhibited, , how vaccines are effective in preventing diseases in humans and animals and how some vaccines can have unintended consequences. We have spent some extra time on Neuraminidase, Glycosylation and SIAS. Now, we need to return our conversation to where we started on that hot summer day when I first met you. Is that OK with you?
Q: Good to go...
MA: When we first met last summer, we had a long conversation about the state of human evolution. How we as a species are doing in the big picture sort of thing. Because I am a bug doctor, my overall perspective is always going to be a bit skewed, and there is no denying that. However, let me ask you this. In the year since our conversation is there any development that alters your very steadfast opinion that, on balance, there are no real "game altering" factors on the horizon?
Q: MA, an asteroid could hit tomorrow, Russia might get pissed at the Chinese or the sun might send a toasty little flare our way. No one can know what might be.
MA: Well that is certainly true to a degree, but we make intelligent predictions every day on the future. When you buy a home, or sell some stock you are looking at future events and making an informed decision on the outlook for tomorrow. Wouldn't you agree?
Q: Well sure, to some degree. But, I know that you are speaking of a much larger evaluation with much greater consequences. And I am still not convinced that we can predict events on that scale.