Viral DNA Quantified with the Help of Super-Resolution Microscopy

24 October 2013

Scientists at the University of Zurich have used super-resolution microscopy to find out more about the way viruses affect cells. The method has helped the Swiss researchers visualize the infection at single-molecule resolution and contributed to measures aimed at quantifying viral DNA (vDNA) trafficking.

The first experiment with the new method, which labels newly synthesized virus without impacting infectivity and is to be fully described in the journal Cell Host and Microbe, was successful at analyzing adenovirus infection. The scientists monitored how a large pool of capsid-free vDNA was amassed in the cytosol upon virus uncoating, assuming that this was due to the fact that nuclear import of incoming vDNA was a bottleneck.

The insights obtained imply that the method could be extremely useful in monitoring the full replication cycle of DNA viruses since it can identify cellular and viral effector machineries on newly-replicated vDNA or immune sensors on cytoplasmic vDNA.

The scientists observed the behavior of vDNA during entry into cells that have been infected with viruses, which were labeled with the help of click chemistry to allow DNA visualization without sample denaturation. The demonstration shows that not all the incoming vDNA makes it to the cell nucleus as expected initially. A substantial part of it was accumulated in the cytosol, which could be a result of its antiviral defense reaction, said Professor Urs Greber, a cell biologist at the University who was in charge of the experiment.

The scientists also saw that cells of the same type absorb different amounts of vDNA into their nucleus, which could be due to their antiviral defense properties which are similar to those in the cytosol.