Inflammatory responses to pneumovirus infection in IFN-αBR gene-deleted mice

Pneumonia virus of mice (PVM; family Paramyxoviridae) is a natural pathogen of rodents that reproduces important clinical features of severe respiratory syncytial virus infection in humans. As anticipated, PVM infection induces transcription of IFN antiviral response genes preferentially in wild-type over IFN-alpha beta R gene-deleted (IFN-alpha beta R-/-) mice. However, we demonstrate that PVM infection results in enhanced expression of eotaxin-2 (CCL24), thymus and activation-regulated chemokine (CCL17), and the proinflammatory RNase mouse eosinophil-associated RNase (mEar) 11, and decreased expression of monocyte chemotactic protein-5, IFN-gamma-inducible protein-10, and TLR-3 in lung tissue of IFN-alpha beta R-/- mice when compared with wild type. No differential expression of chemokines MIP-1 alpha or MIP-2 or Th2 cytokines IL-4 or IL-5 was observed. Differential expression of proinflammatory mediators was associated with distinct patterns of lung pathology. The widespread granulocytic infiltration and intra-alveolar edema observed in PVM-infected, wild-type mice are replaced with patchy, dense inflammatory foci localized to the periphery of the larger blood vessels. Bronchoalveolar lavage fluid from IFN-alpha beta R-/- mice yielded 7- to 8-fold fewer leukocytes overall, with increased percentages of eosinophils, monocytes, and CD4(+) T cells, and decreased percentage of CD8(+) T cells. Differential pathology is associated with prolonged survival of the IFN-alpha beta R-/- mice (50% survival at 10.8 +/- 0.6 days vs the wild type at 9.0 +/- 0.3 days; p < 0.02) despite increased virus titers. Overall, our findings serve to identify novel transcripts that are differentially expressed in the presence or absence of IFN-alpha beta R-mediated. signaling, further elucidating interactions between the IFN and antiviral inflammatory responses in vivo.