Herpes virus cleared from blood for first time

A COMMON virus that can reduce lifespan and cause blindness has been cleared from human blood for the first time.

Cytomegalovirus (CMV), a type of herpes virus, is carried by about 70 per cent of people and, although it usually doesn't cause illness, shaves 3.7 years off life expectancy.

In people with a weakened immune system, however, the virus awakens and can cause serious illness and blindness. This can be a particular problem if the only available donor for a bone marrow transplant is infected with CMV and the recipient is not.

CMV only expresses a handful of genes when it is dormant. One of them is UL138. To investigate what it does to cells, Michael Weekes at the University of Cambridge and colleagues grew healthy human cells alongside cells that were made to express UL138 in the presence of labelled amino acids – the raw ingredients used to make proteins. They then used mass spectrometry to identify how UL138 changed the cells' expression of proteins.

"We know that viruses remodel the landscape at the surface of the cell, so we've been asking 'what proteins are on the cell surface and how does CMV change that?'" says Paul Lehner, also at Cambridge, who supervised the work. CMV appears to dampen the production of a protein called MRP1 that pumps toxic chemicals out of cells – including the cancer drug vincristine. If infected cells can no longer pump out vincristine, perhaps this would kill them while sparing healthy cells that remove the poison?

To find out, the team took blood samples from 15 volunteers with CMV, treated the samples with vincristine and then reactivated the virus. "We either dramatically reduced or eliminated our ability to [detect] any virus," says Lehner, who presented the results at the Strategies for Engineered Negligible Senescence conference in Cambridge this month.

"It will be fascinating to see how this new method comes to be applied in clinical practice," says Paul Moss of the University of Birmingham, UK. Vincristine can have severe side effects, so is unlikely to be used to clear CMV in healthy people or transplant patients. However, it could be used to treat donor blood or stem cells from bone marrow before transplantation.