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New findings show most viruses on human skin have never been identified

After developing a set of tools to investigate the viral population or ‘virome’ of human skin, researchers from the University of Pennsylvania’s Perelman School of Medicine in Philadelphia say they have found that as much as 90% of the viruses on human skin have never been previously described (mBio Oct. 20, 2015).

“There has been a real need for a better understanding of these viruses, given their potential effects on our skin cells as well as on our resident bacteria,” senior author Elizabeth A. Grice, PhD, an assistant professor of Dermatology at Penn Medicine, said in a press release from the university. “Until now, relatively little work has been done in this area, in part because of the technical challenges involved. For example, a skin swab taken for analysis will contain mostly human and bacterial DNA, and only a tiny amount of viral genetic material—the proverbial needles in the haystack.”

Using catalogues of known viral genes to map viral distribution on the skin, as previous studies have done, is prone to overlooking any viruses not already catalogued, according to the release. To get around this limitation, the researchers used metagenomic sequencing of DNA from purified virus-like particles sampled from the skin of 16 healthy volounteers to evaluate the double-stranded DNA virome on human subjects. At the same time, they also sequenced the total skin microbiome to identify covariation between viruses and microbes, and to try and find any interactions between the two.

Within the samples, the most commonly identified skin-cell infecting virus was human papilloma virus, according to the study. However, a large majority of the DNA from the virus-like particles did not match viral genes in any existing database.

“More than 90 per cent was what we call viral dark matter—it had features of viral genetic material but no taxonomic classification,” Dr. Grice in the release.

Much of the viral DNA also appeared to belong to phage viruses that infect bacteria, demonstrating a direct interaction between this virome and the human skin microbiome, according to the release.

Not only do these findings provide a baseline healthy virome for comparison in future studies of disease states, but the authors have provided their algorithms for the DNA sequence analysis in the supplemental materials of the mBio paper so other researchers may replicate the study or conduct their own investigations.

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