Molluscum contagiosum virus (MCV) is a human poxvirus that produces small, benign skin tumors primarily in young children and encodes proteins that modulate the host immune response. The MC51L, MC53L, and MC54L open reading frames of MCV have significant amino acid sequence similarities and related proteins are encoded by other poxviruses. These three MCV genes were individually expressed in mammalian cells as glycosylated and secreted proteins. A database search detected partial sequences of homologous human and mouse cDNAs; determination of the complete sequences confirmed the homology and indicated potential signal peptides and N-glycosylation sites as well as a pattern of cysteines that are conserved in the viral proteins. The human gene, which was mapped to chromosome 11q13, was highly expressed in spleen and lymph nodes, suggesting an immune modulatory role. The latter finding is consistent with a recent report (Novick et al., 1999, Immunity 10, 127-136) that the human protein binds IL-18, suggesting an anti-inflammatory role for the poxvirus homologs.
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