Unknown virus in ‘throwaway’ DNA discovered

Dr Aris Katzourakis and Dr Amr Aswad, both of the Zoology Department, have found that Next-Generation Sequencing and its associated online DNA databases could be used in the field of viral discovery. 

Whilst their research focused on the genome of fish, the method can be used to identify viruses in a range of different species, and the team have now developed algorithms that detect DNA from viruses in the blood or tissue sample of the species studied.

Dr Katzourakis and Dr Aswad initially discovered the new use for the database by chance while looking for an ancient herpes virus in primates. When looking through the database they found evidence of two new undocumented viruses.

To determine if they could intentionally achieve the same result, they established a separate project to find new fish-infecting herpes viruses by using the technique to examine more than 50 fish genomes for recognisable viral DNA. 

Their results found a distant lineage of unusual viruses – possibly a new viral family – scattered in fragments of 15 different species of fish, including the Atlantic salmon and rainbow trout.

Dr Aris Katzourakis said: ‘In the salmon genome we found what seems to be a complete and independent viral genome, as well as dozens of fragments of viral DNA that had integrated into the fish DNA. We know from recent studies that viruses are able to integrate into the genome of their host, sometimes remaining there for millions of years. In this case, it looks like the virus may have acquired the ability to integrate by stealing a gene from the salmon itself, which explains how it has become so widespread in the salmon genome.’

Dr Amr Aswad, said: ‘Discovering new viruses has historically been biased towards people and animals that exhibit symptoms of disease. But, our research shows how useful next generation DNA sequencing can be in viral identification.’

Using this approach could be used to identify viruses in a range of different species, particularly those known to harbour transmissible disease. A strength of the technique is the speed with which viruses can be discovered, and it provides a unique resource for looking for pathogenic and benign viruses that would otherwise have remained undiscovered.

Original publication: https://academic.oup.com/ve/article/doi/10.1093/vex016/4061468/A-novel-v...