PCR contamination

[James Scutero]

T.J. Fitzmaurice writes:
>In article <3i9ugc$il9 at panix.com>, James Scutero <jscutero at panix.com> wrote:
>>ed at molbiol.uct.ac.za writes:
>>>Seconded!  If J Scutero - proponent of 
>>>misc.health.aids.anti-HHV.propaganda - would actually develop a 
>>>thesis rather than simply quoting wildly from papers, it might be 
>>>more interesting and more enlightening.  All he has done now is show 
>>>he can use a paper/bibliographic retrieval system.  I fhe really 
>>>doesn't like a herpesvirus as possible cause of KS, let him explain 
>>>why without the leaps of faith he normally indulges in to "prove" 
>>>a point.
>>
>>Man are you guys twisted! I was the first person to post that KS WAS caused
>Yes but you posted for a long time that it was HHV-6, and you cited several
>papers to backup the idea, you now seem to have done a U-turn, from your
>incontrovertible position.
>
Names of viruses change with time. HHV-6 was originally called HBLV-I until
it was found to primarily kill T cells. After being named HHV-6, it was
further broken down to variants A and B. Variant B is linked to exanthem
subitum, a benign febrile illness of early childhood. Variant A is found in
immunocompromised patients. And:
"The low detection rate of HHV-6 Variant A in PBMCs of the general population
(3%) and in lymph nodes from HIV-infected patients may underlie a different
tissue tropism with respect to variant B, as is also suggested by the frequent
occurrence of HHV-6 Variant A in Kaposi's sarcoma specimens of various origin,
including those derived from HIV-infected patients." Dolcetti, Riccardo et al.;
"Frequent detection of Human Herpesvirus 6 DNA in HIV-Associated 
Lymphadenopathy"; The Lancet 344:543, August 20, 1994.

So, there are two Variants(A and B) of the same virus(HHV-6). Variants A and
B are not found in the same tissues. Variants A and B are not found in the
same diseases. Still, they are considered to be Variants of the same virus.
How are the names of viruses chosen? When is a virus considered to be called
a "Variant" of another virus? Is genetic sequencing the determining factor
for the final taxonomic place for a virus, and if so, based on what criteria?

>>think I changed my mind? The KSHV is a close cousin to HHV-6 and it is a
>>herpes virus and it is the infectious agent that is the cause for KS.
>Thats like saying chicken pox is caused by Herpes simplex.
>And then arguing VZV is closely related so what you said is all right.

Well, the only way to find out is to study an electron micrograph of HHV-6
(variants A and B) and compare it to KSHV. Have you done a comparision of the
genetic sequences of KSHV and HHV-6(A and B) using GENEBANK?

>Might be and Are are two very very different things in science. HHV-6
>for all we knew might have caused KS, but evidence turned out differently.
>Some one usuing this kind of logic could have announced 15years ago
>that KS was caused by a totally novel herpesvirus, with no evidence.
>And he would have been rightly shot down in flames for saying this, as 
>with no evidence anything is just ....... worth that much. He would also
>be right. Being right is unfortunately not enough. You have to be able
>to prove it, until then you have to say I THINK, and this is why, or 
>PERHAPS this is the case. This may be what you mean in many cases, but
>it is not what you say. When the story changes, scepticism hangs in.
>
>Tim
I THINK you should tell me how these two viruses, HHV-6 and KSHV, 
differ physically and genetically.

-James M. Scutero