Analysis of molluscum contagiosum virus genomes isolated in Japan.

The genomes of 477 Japanese strains of molluscum contagiosum virus (MCV) were analyzed using an in-gel digestion method with the restriction enzyme BamHI, and classified into four types, including a newly detected type (MCV type 4). All type 1 (MCV-1) genomes examined so far in Japan showed a common difference from the genome of the MCV-1 prototype (MCV-1p), the type reported to be most prevalent in Europe. The common markers of the variants of MCV-1 were 24-kbp fusion fragments generated by the loss of a BamHI site between the D2 and F fragments of MCV-1p. These variants of MCV-1 were classified into three groups (MCV-1va, MCV-1vb, MCV-1vc), with the variability among them being due to additions and losses of BamHI sites located in the right terminus and around the E and I fragments of MCV-1va. The restriction map of MCV-4 was generated and lined up with those of the other types. Cross-hybridization analysis revealed that the organization of all types of MCV genomes were essentially colinear. Considerable numbers of BamHI restriction sites were conserved between MCV-2 and 4, indicating a close analogy between them. The overall prevalence of MCV, as shown by the ratios of MCV-1 (MCV-1p):MCV-2:MCV-3:MCV-4, was 436(0):13:24:4. Thus, the molecular epidemiology of MCV in Japan is characterized by the absence of the European prototype of MCV-1, the exclusive occurrence and abundance of variants of MCV-1, a greater prevalence of MCV-3 over MCV-2, and the presence of MCV-4.