Acyclovir rescues E15 SMGs infected for 3 days with mCMV and cultured for an additional 3 days (E15 + 6) (A, C, D) or 9 days (E15 + 12) (B, C, F) in the presence (CMV + Acy3) or absence (CMV) of acyclovir treatment. On day 6 (A), there is a decrease in β-gal (mCMV) staining in CMV + Acy3 SMGs compared to mCMV SMGs; by day 12 (B), acyclovir treatment results in sparse β-gal staining. At E15+6, with mCMV infection alone (C), abnormal epithelia surround dilated lumina (*) and clusters of atypical basophilic cells are seen in the periphery (arrows); in contrast, acyclovir treatment (D) partially restores the epithelial phenotype to that seen in control SMGs, with fewer atypical mesenchymal cells (arrows). At E15 + 12, acyclovir treatment (F) results in the near normal appearance of epithelia and mesenchyme (m); this markedly differs from the histopathology seen in E15 + 12 CMV-infected SMGs (E). mc-metaplastic stromal cells. Bar: A, B: 50 μm; C-F: 30 μm.