Efficient replication of pneumonia virus of mice (PVM) in a mouse macrophage cell line.

Pneumonia virus of mice (PVM; family Paramyxoviridae, subfamily Pneumovirinae) is a natural respiratory pathogen of rodent species and an important new model for the study of severe viral bronchiolitis and pneumonia. However, despite high virus titers typically detected in infected mouse lung tissue in vivo, cell lines used routinely for virus propagation in vitro are not highly susceptible to PVM infection. We have evaluated several rodent and primate cell lines for susceptibility to PVM infection, and detected highest virus titers from infection of the mouse monocyte-macrophage RAW 264.7 cell line. Additionally, virus replication in RAW 264.7 cells induces the synthesis and secretion of proinflammatory cytokines relevant to respiratory virus disease, including tumor necrosis factor-alpha (TNF-alpha), interferon-beta (IFN-beta), macrophage inflammatory proteins 1alpha and 1beta (MIP-1alpha and MIP-1beta) and the functional homolog of human IL-8, mouse macrophage inflammatory peptide-2 (MIP-2). Identification and characterization of a rodent cell line that supports the replication of PVM and induces the synthesis of disease-related proinflammatory mediators will facilitate studies of molecular mechanisms of viral pathogenesis that will complement and expand on findings from mouse model systems.

Mucosal inoculation with an attenuated mouse pneumovirus strain protects against virulent challenge in wild type and interferon-gamma receptor deficient mice.

Protective mechanisms underlying the responses to mucosal vaccination are not yet clearly defined. Using the natural mouse pneumovirus pathogen, pneumonia virus of mice (PVM), we explore responses of wild type and interferon-gamma (IFNgamma) receptor gene-deleted mice to virulent challenge after mucosal vaccination with an attenuated virus strain. Serum neutralizing antibodies develop after intranasal inoculation with 30 pfu of attenuated, replication-competent PVM strain 15, which correlate with diminished gross and microscopic pulmonary pathology and protection from weight loss in response to subsequent challenge with the virulent parent PVM strain J3666. Virus replication in response to challenge was blunted in PVM strain 15 vaccinated mice, as was local production of secretory mediators IFNgamma, TNF-alpha, MIP-1 alpha, and MIP-2. Interestingly, responses of vaccinated IFNgamma receptor gene-deleted mice were indistinguishable from those of the wild type, suggesting that IFNgamma signaling may not be crucial for the generation of adaptive responses to pneumovirus infection in vivo.