Using TriLink CleanTag technology, researchers at the University of Wurzburg have developed a deep sequencing method that more reliably detects reactivation of HHV-6, a virus that infects nearly 100% of humans by early childhood.
Once infected, the virus incorporates into the subtelomeric end of chromosomes of the host, typically establishing life-long latency without complications.
"However, under certain circumstances, the virus can be triggered to reactivate later in life. Although it’s still unclear exactly how the virus is reactivated, it can reactivate in the lungs, heart, brain, kidney, and gastrointestinal tract, particularly in people with immune deficiencies (or people with conditions requiring immune suppression, such as transplant patients). HHV-6 reactivation can cause a variety of clinical manifestations, including encephalitis, bone marrow suppression, pneumonitis, and in extreme cases, even death.
One substantial problem in treating these cases is how difficult it is to identify HHV-6 reactivation (which includes types HHV-6A and B).
"Germ line inheritance of chromosomally integrated HHV-6 makes viral DNA-based analysis difficult for determination of early stages of viral activation," stated the authors.
Furthermore, except in acute or initial infections, the viral DNA can typically be found only by biopsy, as it does not circulate in peripheral blood.
In a recent publication in Genomic Medicine, researchers describe an early stage of viral reactivation marked by the transcription of several viral small non-coding RNAs (sncRNAs), including sncRNA-U14, which result from transactivation.
Notably, at this early stage, there is no detectable increase in viral replication and initial experiments have shown that the integrated viral genome is often lost during initial stages of viral reactivation.
These results are corroborated with clinical evidence, as demonstrated by the case of a 15-year-old girl who fell ill and died after starting an antibiotic to treat acne.
The researchers became interested in the case because HHV-6 was detected at high viral load during the course of the disease. For this reason, they analyzed samples of blood, as well as pre-and post-mortem tissue for presence of sncRNA.
Strikingly, skin biopsies taken at the beginning of the disease course were positive for sncRNA-U14, which was detectable several days before detection of the viral load (see Figure 1). This served as an indicator that sncRNA-U14 may be a clinically relevant early biomarker for HHV-6 reactivation. Additionally, biopsy samples of the kidney, liver, and clots were also positive for sncRNA-U14 later in the disease course.
While promising, more research is necessary to further support these results and better understand how the viral lifecycle impacts the clinical manifestation of HHV-6 reactivation. Furthermore, as the research continues, the clinical relevance of early detection, from a treatment perspective, will hopefully emerge.
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