Deletion of CCR1 Attenuates Pathophysiologic Responses during Respiratory Syncytial Virus Infection

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Abstract
The role of chemokines in chronic inflammatory responses are central to the recruitment of particular subsets of leukocytes. In the present studies, we have examined the role of CCR1 in the developing pathogenesis of respiratory syncytial virus (RSV) in the lungs of infected BALB/c mice. Although we did not observe significant differences in clearance of RSV, we were able to identify decreased pathophysiologic responses in CCR1−/− mice. CCR1−/− mice displayed a significant reduction in both airway hyperresponsiveness and mucus production that corresponded to significant increases in IFN-γ and CXCL10. The goblet cell hyper/metaplasia and the expression of mucus-associated gene, gob5, were correspondingly reduced in the CCR1−/− mice. In addition, the Western blot analysis of gob5 protein indicated that CCR1−/− mice have virtually no up-regulation of the protein at day 6 of infection compared with wild-type-infected mice. Results from bone marrow chimeric mice indicated that partial reconstitution of the response could be achieved in the CCR1−/− mice with wild-type bone marrow cells, suggesting that these cells have a role in the response. However, transplanting of CCR1−/− bone marrow into wild-type mice did demonstrate an incomplete deficit in RSV-induced responses, indicating that CCR1+ parenchymal cells may also play a significant role in the process. Thus, the presence of CCR1 appears to have a significant role in the development of detrimental airway physiologic responses during RSV infection. These data suggest that CCR1 may be a potential target during detrimental pulmonary responses during infection.