Thursday, March 11, 2010

Hear no SIV, See no SIV, Speak no SIV

It is no surprise that in this blog space, there is absolutely 0 doubt that HIV exists. I think denying something with that much scientific evidence without presenting actual data of your own is a little silly.When asked on a Facebook discussion about where the Perth Group stood on SIVs we were met with this answer from an important player in the group, Valendar Turner (or at least someone claiming to be

"Yes, “SIV is not HIV” and you cannot know how closely they are related unless you first have proof for the existence of both. And you cannot have animal models and all the rest unless you first have proof for the existence of HIV. And to paraphrase Professor Weiss, you don’t prove the existence of HIV by proving the existence SIV.”

Aside from dodging the question about how the Perth Group stands on SIV, and a lot of circular reasoning I can see why they make this point. The problem is that they cannot offer an opinion either way. The virus is trap to their ideology. Saying” yes”” they believe it exists, or “no” it doesn’t will compromise their argument either way. The best they can do is not answer the question. This is because of the history of SIVmac.SIVmac (our HIV/AIDS model in macaques “mac”) came from the cross species transmission from an SIV from a Sooty Mangabey to macaques, in captivity. It is a really cool story I will have to share some time. Most people talk about HIV coming from chimps. This is true of HIV-1, the more common form that has become pandemic around the world. However, HIV-2 arose form the cross species transmission of a Sooty Mangabey SIV to humans. This is more common in western Africa where the Sooty Mangabey’s natural habitat is. The virus appears to be less pathogenic and less easily spread. Nonetheless it is a human immunodeficiency virus that has a brother in macaques. Because of some careful work, SIVmac239 fulfills a lot of the criteria the Perth Group uses to claim HIV-(1?) does not exist. There are EM pictures of the virus budding from a lymph cell of macaque 239-82.

(Daniel et al., 1985)
(Nicholson et al., 2007)

The virus was cloned after culture (sequence here) and the virus by the clone looks the same (above). Furthermore this virus does fulfill Koch’s postulates. Monkeys that were given infected blood from macaque 239-82 (example macaque 316-85) and the virus caused the same immunodeficiency, and the virus was isolated to make the infectious clone SIVmac316. The SIVmac239 clone can also be used to infect other animals, which present the same immunodeficiency symptoms. These experiments could never be done in people. Basically this virus rocks their argument.

The fact that it is so closely related to a similar HIV virus in humans makes the Perth Group walk a fine line. Because of the overwhelming evidence that SIV is a real virus (the animals are not given any drugs so its not the treatments, they are well fed no so starvation or oxidative stress, monkeys are not in any risk group so they are not IV drug users or hemophiliacs and although I never ask I would think most are not gay) so to deny this virus exists just makes them sound crazy. Yet if they do say this virus exists it opens the possibility of saying HIV-2 exists since both viruses have a common not so distant ancestor in Sooty Mangabeys. Now I cannot prove HIV exists by proving SIV does, but its presence cannot be dismissed either.

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