A common yet deadly virus that hides in specific places in healthy people and is hard to find has now been discovered.
Most adults harbour the human cytomegalovirus (HCMV) that can cause severe illness and even death once their immune system is weakened or they are undergoing treatment for certain life-threatening diseases.
Researchers reported that stem cells that encircle blood vessels can be their hiding place - suggesting a potential new treatment target.
"Perivascular stem cells which are found in bone marrow and surround blood vessels in the body's organs are a reservoir of HCMV," said Graca Almeida-Porada, a professor of regenerative medicine at North Carolina-based Wake Forest Baptist Medical Center.
In people with weakened immune systems, including those with HIV, undergoing chemotherapy or who are organ or bone marrow transplant recipients, the virus can become re-activated.
Once re-activated, HCMV can cause a host of problems - from pneumonia to inflammation of the liver and brain - that are associated with organ rejection and death.
"There are anti-viral medications designed to prevent HCMV from re-activating, but HVMC infection remains one of the major complications after both organ and bone marrow transplants," Almeida-Porada explained.
Scientists have previously shown that one hiding place is hematopoietic stem cells, which give rise to blood cells.
Almeida-Porada's team hypothesised that cell populations in the body's tissues may be able to harbour the virus and suspected that perivascular cells that surround blood vessels were a likely culprit.
Their suspicions were confirmed when testing revealed that perivascular cells are susceptible to HCMV infection and that the virus can grow within these cells.
The team compared the susceptibility of perivascular cells from the liver, brain lung and bone marrow to the virus and found the highest rate of HCMV infection in lung perivascular cells.
"This may explain why pneumonia is the primary manifestation of the HCMV infection in bone marrow transplant recipients," Almeida-Porada noted.
Identifying the cells that can harbour the virus and are responsible for its re-activation could potentially lead to development of novel targeted therapies, said the research published in the American Journal of Transplantation.
