2008 Annual Report 1a.Objectives (from AD-416) 1. Determine the ontogeny of innate immune activity by alveolar macrophages/dendritic cells. 2. Determine the severity of respiratory syncytial virus (RSV) infection and the extent of alterations in alveolar macrophage/dendritic cell innate immune responses in pre-term and full-term lambs. 1b.Approach (from AD-416) 1. The extent of alveolar macrophage/dendritic cell expression of toll-like receptors and cytokines will be determined in pre-term and full-term lambs using real-time polymerase chain reaction (PCR) assays. 2. The extent to which RSV alters the expression of toll-like receptors and cytokine gene expression will be determined by real-time PCR assays. 3.Progress Report We determined that bovine respiratory syncytial virus (BRSV) can productively infect neonatal ovine alveolar macrophages. Next, we determined whether there was a modulation of proinflammatory or immunomodulatory cytokines during in vitro BRSV infection of alveolar macrophages. Real-time PCR assays were developed for ovine cytokine mRNAs and ELISAs for measuring cytokine secretion. The data indicate that BRSV induces both immunomodulatory and proinflammatory cytokine mRNA production, but the infected neonatal alveolar macrophages fail to secrete the corresponding cytokine protein. Inability to secrete the appropriate cytokines in response to infection would result in a failure to clear BRSV and leave the host susceptible to secondary infections. Two manuscripts are to be submitted detailing the results of experiments with BRSV-infection of neonatal alveolar macrophages. Monitoring activities included weekly teleconferences, email, monthly meetings, and annual reports. This work relates to the Action Plan for National Program 103 Animal Health under Component 4: Prevention and Control of Respiratory Diseases; Problem Statement 4A: Ruminant Respiratory Diseases; and the Output for this research is Characterize Mechanisms of Immune Evasion and Protective Immunity.