Re: Re: Re: Some Random Comments 1 November 2004
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Nicholas Bennett,
Infectious Disease Postdoc/Clinician
Department of Pediatrics, University Hospital, Syracuse NY

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Re: Re: Re: Re: Some Random Comments

The serology dilutions aren't the titre changes in response to infection, but the same kind of test (ELISA or similar) to those in question for HIV. Some examples I pulled randomly from Google/Pubmed are:

RSV: 1:100 Influenza 1:100 CMV 1:40

There is certainly at least one ELISA for HIV that uses neat serum or plasma [1].

I would say that the HIV tests have been developed to at least as high, if not higher, degrees of pathogen isolation as seen with any other infection. The problem, as we've seen here, is not whether HIV has been isolated but whether the methods used are considered by various people as valid. Most virologists would say yes.

As to direct effects due to HIV: the lymphoma risk seems to be due to HIV infection and subsequent immune hyperactivation. HIV causes dementia by killing certain supportive glial cells, which are also CD4+. The malabsorption syndrome may also be due to HIV, although I have also heard CMV implicated.

I would say that CD4 counts are still considered important: but not for prognosis. They have always been more strongly predictive of current risk of OIs. Technically you could live reasonably happily with low CD4s, assuming you didn't get PCP or candida or something else commensal. However, judging from the observed risks seen with CD4 counts below 200, I wouldn't be particularly keen to do so.

The comments on removing HIV are interesting... The problem is that even though (RNA) viral load is shut down to "undetectable" level, (DNA) proviral load declines much less rapidly and is very resistant to any kind of attack: both immune-mediated and therapeutic. It seems that low-level reactivation of this reservoir occurs, which is probably where drug- resistant and immune escape mutations arise from. There is good evidence that even with this incomplete shutting down the immune system does start to rebuild itself, not just in terms of numbers but also in the repertoire of antigens it can respond to. Whether a complete clearance of the infection would result in a complete restoration I don't know. My understanding is that the damage is cumulative, and the amount of repair that is done drops off as the time course of the infection progresses. Whether this means that any amount of infection means a normal immune system can never be reattained I don't know. It's quite likely that a mildly damaged system will work perfectly well - or well enough at least.

Nick Bennett njb35@cantab.net

1. http://www.rapidtest.com/HIV(1+2)_1516.doc

Competing interests: None declared