Assessment of new in vitro and in vivo models for mumps virus replication

Abstract

Mumps virus (MuV) is a paramyxovirus which causes mumps, a communicable disease in humans characterised by pain and swelling of the parotid gland(s). Suspected mumps cases are confirmed by PCR detection of MuV nucleotide sequences followed by virus isolation using Vero cells. Veros are the “gold-standard” for MuV isolation however they may select for attenuated or adapted virus variants and produce genetically altered viruses unsuitable for research, although this has never been confirmed. A cell line investigation was performed to assess genetic stability, viral fitness and plaque phenotype of MuV through serial passage in a panel of cell lines including Veros. Primary ex-vivo human airway epithelial cultures were infected with different MuV strains to investigate their susceptibility to MuV. The data presented here shows mutations in MuV introduced during passage through Vero and other continuous cell lines for the first time and suggests alternative cell lines for MuV propagation. HAE cells are demonstrated to be capable of isolating MuV from a clinical sample and producing progeny virus with superior genetic similarity to the parent virus when compared with Vero’s. No animal model exists for MuV therefore in vivo knowledge of the virus is limited. Ferrets are established as a successful model for influenza virus. MuV and influenza share certain biological features such as utilisation of sialic acid as the cellular receptor and both are negative-sense single-stranded RNA viruses. This suggests that ferrets may be useful as a MuV model. Ferrets were assessed as an in vivo mumps model by investigation of clinical signs, virus shedding and recovery from tissues, serum antibody response and detectable immune response in PBMCs. The data presented here demonstrate that ferrets elicit a mumps-specific neutralising antibody response and mount a cytokine response consistent with viral infection, however due to lack of clinical symptoms, virus shedding and virus recovery from tissues, the ferret model is very limited in its usefulness for MuV research.