Three mucosal sites (vagina, tongue, and anus) infected with the L1-L2ATGko mutant demonstrated strong viral DNA and E4 expression but absence of L1. Viral DNA positivity was detected in the vaginal tracts and oral cavities of the infected animals of the L1-L2ATGko mutant (A, ISH, 20×, and arrows). L1 was undetectable in these tissues by immunohistochemistry (IHC) with MPV.B9 (A, 10×). However, all infected tissues showed intracytoplasmic E4 expression ranging from multifocal and light (anus) to more extensive and strongly positive expression (tongue and anus) (A). L1 expression is scattered but marked in wild-type MmuPV1 infected tissues by MPV.B9 in the nuclei of infected cells (B, 20×).