Contamination of PCR with HHV-6

[James Scutero]

Charles H. Calisher writes:
>In his pointedly passing on the reference to possible contamination of PCR 
>samples by HHV-6 in human breath, J. Scutero does not explain how controls 
>might be negative and KS patients positive for HHV-6.  Why not?
>
The KS researchers might not have had KSHV or HHV-6 variant A in their 
respiratory tracts and so they could not contaminate their samples.
The KS researchers could have also practiced better hygienic techniques in
the lab while they performed PCR-like wearing a mask!

According to Kelley and McClain:

"     The extreme sensitivity of the PCR makes this technique especially
vulnerable to contamination. False positive reactions may result from a number
of different sources including DNA from shed epithelial cells or hair, DNA
suspended on gloves, clothing, or airborne particles. Equipment (pipettors,
centrifuges, water baths, autoclaves, etc.) can also contribute contaminating
particles to the reaction. Cross-contamination of reagents with positive
controls also occurs. The most common source of PCR contamination is PCR
products carried over from previous reactions."

1. Kitchin PA, Szotyori A. Fromholc C, Almond N: Avoidance of PCR false
positives. Nature 344:201. 1990.

2. Kellogg DE, Kwok S: Detection of human immunodeficiency virus. In Innis
MA , Gelfand DH. Sninsky JJ, White TJ, (eds): "PCR Protocols: A Guide to
Methods and Applications," Troy, MO: Academic Press, 1989, p337

3. Ibid, p. 142

4. Kwok S, Higuchi R: Avoiding false positives with PCR. Nature 339:237, 1989.

Nobel Laureate, Kary Mullis, the inventor of PCR, will use this very same
sensitivity and contamination issue of PCR in the O.J. Simpson trial in
order to defend Mr. Simpson. 

-James M. Scutero