Merkel Cell Polyomavirus

Merkel cell polyomavirus
Merkel cell polyomavirus was first described in January 2008. MCV is one of seven known human tumor viruses. It is suspected to cause the majority of cases of Merkel cellcarcinoma, a rare but aggressive form of skin cancer. Approximately 80% of Merkel cell carcinoma (MCC) tumors have been found to be infected with MCV. MCV appears to be a common —if not universal—infection of older children and adults. It is found in respiratory secretions suggesting that it may be transmitted by a respiratory route. Most MCV viruses found in MCC tumors, however, have at least twomutations that render the virus nontransmissible: 1) The virus is integrated into the host genome in a monoclonal fashion and 2) The viral T antigen has truncation mutations that leave the T antigenunable to initiate DNA replication needed to propagate the virus.
Evidence that MCV is the cause of MCC tumors that are infected with the virus comes from studies in which oncoproteins from the virusare inhibited. Knock down of these viral proteins causes cells from MCV-positive MCC tumors to die whereas there is no effect on cells from tumors that are uninfected with the virus.
Prevention,diagnosis, and treatment

Persons who have Merkel cell carcinoma with this virus are not infectious to others and no infectious restrictions are warranted. The reasons for this are: 1) the virus intumors is already mutated and no longer can be transmitted from tumors, and 2) most persons are already naturally exposed to this virus as children and young adults by other asymptomatic carriers.
Basedon current data, prevention advice for MCC is similar to other skin cancers, such as avoiding sun burns and unnecessary sun exposure together with use of sun lotion. This may prevent mutations in thevirus that increase risk for MCC among those already infected with MCV. Persons with immunosuppression (e.g., AIDS or transplant patients) are at higher risk for this cancer and may benefit from...