The Illusive Human Blood Virome

Swirling among the countless other ‘omic’ terms that have grown out of technological and scientific advances is the human virome, or the collection of viruses in and on the human body. Given how quickly viruses evolve, the human virome is changing constantly, affecting the human microbiome and even the genome. At first pass, this may seem like another fascinating realization borne out of modern scientific advances; however, as illustrated in a PLOS Pathogens publication, recent efforts to characterize the blood virome of more than 8,000 people resulted in surprising findings and the realization that significant challenges remain for researchers trying to identify novel viruses.

 

As you can imagine, identifying the viruses present in human blood is hugely important for ensuring the safety of blood transfusions and recognizing emerging pathogens. That’s why researchers undertook a study of whole genome sequence data derived from the blood of 8,240 people. Importantly, prior to the study’s analyses, none of the participants had been ascertained for infectious disease. Yet, researchers were able to map sequences to 94 different viruses in 42 percent of the participants. One of the notable viruses they found was papillomavirus, which was present in 13 individuals. While human papillomaviruses (HPVs) are a diverse group of more than 200 related viruses, certain ones have been tied to a high risk of cancer. Another virus they detected was herpesvirus 8 (HHV-8), which was found in three individuals. As you may know, HHV-8 can cause Kaposi sarcoma, a rare, lesion-inducing cancer. The researchers noted that these two findings in particular were relevant for transfusion medicine.

 

Unfortunately, the researchers attributed some 75 viruses to either environmental origins or the contamination of commercial reagents. In other words, substantial technical hurdles stand in the way of ideal identification of novel human pathogens, even with advances like whole genome sequencing. Despite such challenges, this study marks an impressive contribution to categorizing the many human DNA viruses. It’s also worth noting that for this study, researchers dug into almost one petabyte of sequence data. For reference, the Library of Congress had roughly 235 terabytes of data in April 2011, and a petabyte is more than four times that!