Detection of viremia with lymphotropic DNA viruses, like HHV-6A/B and HHV-7, is best done in cell-free plasma, since the viral DNA is latent in some of the white blood cells. But cell-free plasma still contains much cellular DNA, and finding the viral DNA can be like finding a needle in a haystack.
A team from the University of Washington, led by Alex Greninger, noted that the DNA of DNA viruses is much more likely than cellular DNA to be present in small fragments, less than 120 base pairs. They took 12 plasma specimens known to be positive for various DNA viruses and filtered the cell-free plasma to remove the larger DNA fragments. The eluate containing the smaller fragments then was amplified over seven cycles, and sequenced. This procedure resulted in much higher ratios of virus/human cell-free DNA—for adenovirus, varicella-zoster virus and HHV-6, though not for Epstein-Barr virus—and improved sensitivity for detecting the viral DNA.
The extra step of filtering the cell-free DNA adds time and cost to the task of identifying viral DNA in cell-free plasma, so its utility in clinical diagnostics will likely depend on the development of techniques for reducing this extra time and cost.
Read the full article: Phung 2022