{"entity":{"id":"mcpyv-status","kind":"term","name":"Merkel cell polyomavirus (MCPyV) status","aka":["MCPyV","Merkel cell polyomavirus","MCV","virus-positive Merkel cell carcinoma","virus-negative Merkel cell carcinoma","MCPyV-positive","MCPyV-negative","large T antigen","CM2B4","MCPyV oncoprotein antibodies","AMERK","Merkel polyomavirus antibody titre"],"tldr":"About eight in ten Merkel cell carcinomas are driven by a common skin virus that has stitched itself into the tumour's DNA; the virus-negative rest are driven by sunlight and carry a huge mutation load. Both respond to immunotherapy, and in virus-positive patients a blood antibody test against the viral protein can track the cancer after treatment.","summary":"What is measured: whether a Merkel cell carcinoma carries integrated Merkel cell polyomavirus, and the patient's antibody response to its oncoproteins. How: immunohistochemistry for the viral large T antigen (CM2B4 antibody) or PCR for viral DNA on the tumour; serum antibodies to the small and large T oncoproteins (the AMERK test) in about half of patients at diagnosis, whose titre falls after successful treatment and rises months before a recurrence is visible (antibodies to the capsid protein are common in healthy people and useless). Virus-negative tumours carry an ultraviolet mutational signature, very high tumour mutational burden and TP53 and RB1 mutations; virus-positive tumours have few mutations yet respond just as well to PD-1 and PD-L1 blockade (avelumab in JAVELIN Merkel 200, pembrolizumab in KEYNOTE-017, retifanlimab). What a result changes: prognosis (virus-positive slightly better), the surveillance strategy (serial titres in seropositive patients in place of some imaging), stratification in trials, and eligibility for T-cell therapies directed at viral antigens. Where it matters: Merkel cell carcinoma.","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Merkel_cell_polyomavirus","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Merkel_cell_polyomavirus"}],"tags":[],"related":["avelumab","pembrolizumab","retifanlimab","tmb","ihc","mutational-signature","tumour-markers"],"cancers":["merkel-cell-carcinoma"],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Biomarkers"},"route":"/terms/mcpyv-status/","neighbours":{"drug":[{"id":"avelumab","kind":"drug","name":"Avelumab","route":"/drugs/avelumab/"},{"id":"pembrolizumab","kind":"drug","name":"Pembrolizumab","route":"/drugs/pembrolizumab/"},{"id":"retifanlimab","kind":"drug","name":"Retifanlimab","route":"/drugs/retifanlimab/"}],"term":[{"id":"ihc","kind":"term","name":"Immunohistochemistry (IHC)","route":"/terms/ihc/"},{"id":"mutational-signature","kind":"term","name":"Mutational signature","route":"/terms/mutational-signature/"},{"id":"tumour-markers","kind":"term","name":"Tumour markers (CEA, LDH, chromogranin, thyroglobulin)","route":"/terms/tumour-markers/"},{"id":"tmb","kind":"term","name":"Tumour mutational burden (TMB)","route":"/terms/tmb/"}],"cancer":[{"id":"merkel-cell-carcinoma","kind":"cancer","name":"Merkel cell carcinoma","route":"/cancers/merkel-cell-carcinoma/"}]}}