What are the top mistakes that research teams can make when trying to study HHV6?
Many groups studying HHV-6A/B in chronic conditions want to look in the plasma or cerebrospinal fluid (CSF), and fail to understand that HHV-6 DNA appears in those compartments only briefly and typically only during acute reactivations. These are low copy number viruses that spread cell-to-cell. They also generate potent chemokines and cytokines, even in latency.
There may be low-level DNA detectable by nested PCR in a chronic case, but generally, qPCR, ddPCR, and RNA sequencing techniques are not able to detect low level central nervous system infections of HHV-6A/B in plasma in ME/CFS and MS patients. HHV-6 DNA levels
can be extremely high in the brain, liver, or lung, with barely a trace in the plasma. So biopsy analysis is extremely important. Also, HHV-6A/B viral infections have scattered foci, multiple samples per biopsy are necessary to get a true understanding of prevalence in any organ.
Another mistake is to look at DNA in whole blood, where viruses like HHV-6B and EBV can be found in latent form. For HHV-6, this is too simplistic. It is more important to identify organ tissues where there might be active infection, or a smoldering infection – a latent infection that is still throwing off inflammatory cytokines and chemokines.
Finally, many studies fail to rule out inherited chromosomally integrated HHV-6, which occurs in 0.86% of the US population controls and 1.5 – 2% of patients. These patients will always be positive for HHV-6 DNA in the plasma and CSF, even if asymptomatic, so this condition needs to be determined. (This is easy to do by measuring HHV-6 DNA in whole blood by qPCR because there is one genome per nucleated cell, so the viral load is typically in the millions per mL.)
