Re: The non-existent knobs on "HIV" particles 20 July 2004
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Nicholas Bennett,
Infectious Disease Postdoc/Clinician
Department of Pediatrics, University Hospital, Syracuse NY

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Re: Re: The non-existent knobs on "HIV" particles

As regards the Perth Group's continual obsession with gp120 knobs, I noticed their final paragraph: Zhu et al are commenting on the relative sparsity of EM-visible knobs and the Perth Group finish with:

"In other words the number of knobs, if indeed there are any at all present on the particles, are not reconcilable with the generally accepted view of HIV infectivity."

Err, I beg pardon but it's entirely reconcilable with the generally accepted view. The generally accepted view is that HIV is rather bad at infecting anything, yes people included! Particle/Pfu ratios as high as 100,000 have been reported. HIV is approximately 10 times less effective at needlestick transmission compared to hepatitis C, and 100 times less effective as hepatitis B (note though, it is still infectious!). This finding _explains_ the generally accepted view of HIV infectivity! One must wonder what other "generally accepted" misconceptions the Perth Group are living under. The conclusion they come to above is neither supported by the text they quote, nor by the rest of the primary literature. It's pure fabrication!

And if the Perth Group are trying to say that there are in fact no knobs on HIV virus particles, one must ask them why a gp120 deleted virus is replication defective? Like any other virus in existence, if you take away its putative cell-binding protein then it cannot replicate.

gp120 might not be a particularly stable molecule, at least in EM preparation, but it's certainly active. It can even be transferred to other viruses and causes specific infection of CD4+ T cells![1]

Once again, the EM evidence is trumped by the molecular biology of the virus. gp120 deleted virus is so badly affected that it is officially down graded to a category 2 pathogen (HIV is normally category 3). Arguing over whether or not HIV has EM-visible knobs is an entirely moot point... Certainly they exist because some groups have quantified them [2 -3 for example]. Reference 3 incidentally does show the spikes quite nicely in figure 3A, although the heavy metal staining method has hidden the viral core.

Refs:

1. Johnson et al. J Virol. 1997 Jul;71(7):5060-8. Specific targeting to CD4+ cells of recombinant vesicular stomatitis viruses encoding human immunodeficiency virus envelope proteins.

2. Hart et al. J Histochem Cytochem. 1993 Feb;41(2):265-71. Morphometric analysis of envelope glycoprotein gp120 distribution on HIV-1 virions.

3. Hart et al. Proc Natl Acad Sci U S A. 1991 Mar 15;88(6):2189-93. Binding of soluble CD4 proteins to human immunodeficiency virus type 1 and infected cells induces release of envelope glycoprotein gp120.

Competing interests: None declared