Murine Cytomegalovirus and Human Cytomegalovirus Differ in Pyroptosis Induction in Different Cell Types During Productive Replication

Pyroptosis is a proinflammatory programmed cell death (PCD) that protects the host against invading viruses. We previously reported that pyroptosis plays a prominent role in the pathogenesis of murine cytomegalovirus (MCMV) retinal necrosis using mice with MAIDS as a mouse model for AIDS-related human cytomegalovirus (HCMV) retinal necrosis. Because MCMV and HCMV exhibit species specificity, we sought to determine if pyroptosis induction extends to different cell types of murine or human origin. In vitro studies were therefore performed in which MCMV-infected mouse fibroblasts and mouse macrophages were compared with HCMV-infected human fibroblasts and human ARPE-19 cells for stimulation of caspase-1, gasdermin G (GSDMD), and interleukin (IL)-18 and/or IL-1β transcripts as markers for canonical pyroptosis operation. Whereas MCMV stimulated significant stimulation of pyroptosis-associated transcripts during productive replication of mouse fibroblasts and mouse macrophages, significant stimulation of these transcripts was not detected during HCMV productive replication of human fibroblasts or ARPE-19 cells. Additional studies using UV-inactivated MCMV suggested that virion tegument proteins are not involved in the induction of pyroptosis in MCMV-infected mouse fibroblasts. We conclude that pyroptosis induction during productive replication of MCMV or HCMV is host cell type-dependent and may extend to species specificity, although virus-encoded PCD suppressors must be considered.