Coxsackie virus entry and spread in HeLa cells is aided by microvesicle release.

Introduction: Microvesicles (MVs) released from the plasma membrane are important vectors in intercellular communications. Coxsackievirus B (CVB), a member of the enterovirus family, is the main cause of meningitis and encephalitis in infants which may result in neurodevelopmental defects. Calpains are calcium-dependant cysteine proteases that degrade cytoplasmic and cytoskeletal proteins and regulate a variety of actin-dependant cellular processes such as microvesiculation. Materials and methods: Coxsackievirus B1 (CVB1) was obtained from the Health Protection Agency (HPA, UK) and expanded by infecting HeLa cells. CVB1 was purified through centrifugation, and titres were determined by plaque assay on HeLa cells. For infection, cells were inoculated with CVB1 at a multiplicity of 50 PFU/cell and kept at 378C until fixation for flow cytometry or immunofluorescence assays were performed. Cells and cell-debrisfree culture supernatants were filtered through a 0.22 mm pore size membrane filter. MVs were recovered from the filter by washing and centrifugation (25,000 g for 1h). Results: CVB1 requires calpain activation for both entry and virus replication. Here, we show that knocking down calpain, using approaches such as small interfering RNA (siRNA), culminates in reduction of MV release, as we showed before, with another intracellular pathogen, the protozoan parasite, Trypanosoma cruzi. The reduction in MV release then abrogates CVB1 entry and spread in HeLa cells. The calpain inhibitor calpeptin also caused similar reduction in CVB1 entry and spread to healthy target cells. Discussion: Together, our findings provide evidence that CVB1 infected HeLa cells enhance MV production, and these MVs aid the spread of infection. Furthermore, inhibition of MV release using siRNA results in inhibition of CVB1 entry and spread.