RV-Mediated Mechanisms of Neutrophil Motility /Inflammat

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The inflammatory response induced by rhinovirus is characterized by the predominance of airway neutrophils that correlates with the severity of asthma exacerbation. Despite considerable recent evidence that supports the importance of neutrophils in the pathogenesis of asthma, there is limited understanding of how rhinovirus modulates neutrophil function. The long-term goal of this proposal is to characterize the signaling mechanisms by which respiratory viral infections induce neutrophil motility and recruitment to the airway, and to identify novel therapeutic targets that limit viral-induced inflammatory responses. Substantial evidence suggests that rhinovirus infections induce neutrophilic inflammation indirectly by promoting the release of inflammatory mediators from airway epithelial cells. We now have exciting new data that indicate that rhinovirus 16 also has direct effects on neutrophil signaling and motility. With our established expertise in live fluorescent imaging and recently developed novel technology to analyze chemotaxis using microfluidics, we are uniquely positioned to test the following hypothesis. We propose that rhinovirus, by both indirect and direct interactions with neutrophils, modulates signaling pathways critical for neutrophil migration and chemotaxis, and thereby affects the recruitment and retention of neutrophils in the airway. We propose the following Specific Aims: I. Elucidate the mechanisms of neutrophil chemotaxis and recruitment to the airway in response to respiratory viral infection. Calpain inhibition blocks neutrophil chemotaxis to IL-8 in vitro. Using both in vitro and in vivo approaches with transgenic mouse models in collaboration with Project IV, we propose to characterize how calpains regulate neutrophil chemotaxis and inflammatory recruitment in response to respiratory viral infection in vivo. II. Dissect the molecular mechanisms by which rhinovirus modulates TNFalpha-mediated neutrophil function. TNFalpha promotes a stop signal that triggers neutrophil adhesion and inhibits cell migration. Our recent studies indicate that rhinovirus perturbs TNFalpha-mediated effects. In addition, preliminary data indicate that rhinovirus may affect neutrophil function directly via activation of ERK and p38 MARK pathways. In collaboration with Project II and V, we now propose to dissect the molecular mechanisms by which rhinovirus modulates TNFalpha-mediated neutrophil adhesion and signaling. III. Examine the effect of rhinovirus on neutrophil motility and chemotaxis. Preliminary findings indicate that rhinovirus directly induces neutrophil random motility and reduces chemotactic migration through an ICAM-1- dependent pathway.. Using time lapse microscopy, we now propose to dissect the mechanisms by which rhinovirus modulates neutrophil migration and chemotaxis, and in collaboration with Project I determine if these mechanisms are different in patients susceptible to rhinovirus-induced asthma exacerbation.