The cytomegalovirus, otherwise known as CMV currently infects between 50 and 80 percent of the US population aged 40 and above. Normally it is relatively harmless and does not cause serious illness. However in vulnerable groups such as newborn infants, the very elderly or those infected with HIV or other diseases affecting the auto immune system, CMV can present serious and even fatal problems.
When most viruses attack the body, they are remembered by the immune system in case of future attack. That is why it is unusual to contract chickenpox, seasonal strains of influenza and many other virally transmitted diseases more than once.
CMV is different, and is one of very few viruses which can trick the bodys immune system and successfully attack several times. The mystery of how CMV is able to do this has recently been unraveled thanks to research by Oregon Health & Science University (OHSU).
By studying monkeys naturally infected with CMV, researchers discovered re-infection could only occur by the virus evading killer T cells, critical detector mechanisms in the immune system.
Dr Klaus Frueh, professor of microbiology at OHSU School of Medicine explains CMV evades these alert systems by making genes that disrupt the MHC-I molecules ability to communicate an ongoing infection to the T cells. In essence, CMV is able to cutoff an infected cells call for elimination. This allows CMV to overcome this critical immune barrier during re-infection.
The study reinforces the difficulties in formulating a successful vaccine against CMV, but on a positive note, if CMV could be used as a viral vector in the development of vaccine against HIV, Herpes, Hepatitis C and other viruses affecting the immune system, then unlike other viral vectors which may be used only once (due to their detection and future elimination by killer T cells). CMV could be used repeatedly to stimulate an immune response.
