Which cells does HIV infect?

LOUIS J. KAWALEK ljk at welchlink.uoregon.edu
Sun Apr 9 14:12:18 EST 1995


On Mon, 3 Apr 1995, Christopher J. Savoie wrote:

> Dear Lou,
> 
> Why cooldn't CD8's be infected?  They are all derived from CD4+
> thymocytes (double positives) which are known to be the MOST infected
> compartment in the thymus of SCID/HU mice infected with HIV?

	I can't say that they couldn't.  My assumption was as follows:

	Let's assume that a virus infects a double positive cell in the 
thymus.  The virus incroporates its genetic material into that of the 
host cell.  The host cell subsequently undergoes genetic rearrangement, 
turning it into an exclusively CD4+ or CD8+ cell.  I always assumed that 
the viral genome was removed at this point, because the host cell didn't 
know where to put it.  Now the cell becomes a clean CD4+ OR CD8+ cell.  
Now if the cell were exposed to the virus, only the CD4+ cells would be 
infected.

> It seems rather silly to suggest that CD8's which are derived 
> from CD4's would be UNINFECTED.

	Here's a question.  We have demonstrated infection of CD4+ 
cells.  There has probably been demonstration of infected double positive 
cells.  Has there ever been demonstration of exclusively CD8+ cells?  If 
there had been, I think your theory would be proven.  If not, why not?  
Is the virus cleared during rearrangement, or is there another theory?  
Or is it that no one thought to look?

> But that's OK...most others assume the same at present.  Because they
> think that the thymus goes on an early retirement after puberty...The
> CD4 folks have so many research dollars tied up in studying CD4 cells
> that they never really look at the CD8's, which control viral disease
> progression.  The CD8 folks see the CD8's as the unaffected saviors
> in the battle against disease progression, not as targets themselves.  

	Hardly.  I am quite aware of the role of both CD4+ and CD8+ 
cells.  In my previous post, I mentioned the interdependence of the two 
cell 
types.  I just figured we'd have identified exclusively CD8+ cells 
infected with HIV if your theory held true(and if these had been 
identified, I'd have thought it would have stirred up an initial 
controversy over whether our understanding of how the virus infects cells 
is correct...until someone thought of your answer).

> CD4 and CD8 researchers tend to be mutually exclusive
> groups in immunology/virology.  And they've convinced each other
> that the CD8's are doing just fine until they suddenly drop dead
> at the onset of AIDS.

	I don't think they ever just drop dead at the onset of AIDS.  
More than likely, as older cells reach senesence, there are no newer, 
younger cells being generated due to lack of stimulation, which is a 
direct result of the infection of the CD4+ cells(since these provide that 
stimulation).

				Thanks,
				  Lou



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