look for viral mRNA expression that distinguishes the two.

this might be a useful reference: Rev. Med. Virol. 2012; 22: 144–155.

DOI: 10.1002

Laurie, thanks for the suggested reference. Hope to clarify my needs.

Pradeau et al. 2006, J Virol Methods. 2006 Jun;134(1-2) describe the usage of a reverse transcription-nested PCR to distinguish between latent and active infection. They consider U79/80 mRNA as a marker of HHV-6 reactivation.

Richard, would you recommend doing that in a diagnostic lab?

Many thanks!

http://www.sciencedirect.com/science/article/pii/S0166093405003873

No, it daes not!

EFK

if this mRNA can distinguish latent and active infection then should be able to make the primers according to the paper. Best to do it by real-time PCR and add a probe for greater specificity/sensitivity. any lab with real-time PCR capabilities should be able to run for you and they could probably help you find primers and probe. Don't think you need diagnostic lab and does not sound like the assay is truly diagnostic yet.

Kaleta, looks to me that you're not convinced by the paper findings. Is your experience telling something different?

I still do not get the picture of how would be possible to differentiate between latent and active infection by checking for mRNA expression. I mean, when mRNA is transcribed I would assume its sequence is similar in either case. Could be that the mRNA of ciHHV-6 has a shorter sequence due to nucleotide loss while integrating?

However, found that checking for U94 might give a hint, as it is expressed in latently infected PBMCs.

Any idea?

I am not familiar with all the genes of HHV-6 but other herpesviruses have certain genes (mRNA) that are turned on or off depending on their state of latency or active infection. It may be a quantitative difference. for example, during latent infection the mRNA for structural viral proteins is much lower than during an active infection. Also some viral regulatory genes such as U94 may have greater expression during latency as compared to active infection.

this is a good review of HHV-6 latency a section near the end described U94 gene role in maintaining viral latency.

Microbes Infect. 2011 August ; 13(8-9): 731–741

Thanks Richard, just got into this paper sa well!