Proinflammatory responses to many viruses are important for clearance of the viral infection by the immune system. The importance of key proinflammatory molecules, IL-12 and IL-18, in mediating an immune response to adenovirus infection has been documented in mice. Release of these cytokines by macrophages at the site of viral infection recruits additional phagocytes and directs the quality and quantity of the adaptive immune response. Too much of these cytokines can, however, contribute to the pathogenesis of viral infection by enhancing the damage to infected tissues. The importance of the precise control of IL-12 and IL-18 release in response to various pathogens and danger signals is evidenced by the complex transcriptional and post- transcriptional control of IL-12 and IL-18 release from cells in response to infection. Ultimately, the secretion of IL-12 and IL-18 depends upon the activity of a multiprotein complex known as the inflammasome. This complex activates the interleukin-1 convertase, caspase-1, resulting in cleavage of proIL-12 and proIL-18 to secretion competent `mature'forms. Adenovirus was recently shown to activate the NALP3 inflammasome but the mechanism remains poorly defined. Given the important antiviral function of IL-12 and IL-18 in responding to adenovirus infections, we will examine the mechanisms of adenovirus mediated release of IL-12 from macrophages and examine the mechanisms of adenovirus induced macrophage cell death. We will determine the role of adenovirus capsid proteins in activating the inflammasome via NALP3 and the adaptor protein ASC. We will explore potential mechanisms used by adenoviruses with respiratory tropism to attenuate inflammasome activation. Finally, the dependence of adenovirus induced death of macrophages on specific inflammasome components and the contribution of this death process to the proinflammatory response will be elucidated. Results from these studies will provide novel information regarding molecular mechanisms for sensing viral infection which strongly influence the immune response to the virus. Given the importance of adenovirus vectors for gene therapy and genetic vaccination, results from these studies could aid in the design of improved gene therapy vectors which are no longer limited by the immune response to the vector. Alternatively, these studies may provide information which will result in the development of Ad-based genetic vaccines possessing more precise control of the immune response to achieve maximal protective immunity against pathogens such as HIV, hepatitis C or influenza.
A better description of the initiation of immune responses to viral infection will greatly aid in our understanding of viral pathogenesis and allow for the development of more effective antiviral treatments and vaccination strategies. Using the respiratory pathogen, adenovirus, as a model we will define the mechanisms involved in recognition of viral infection by the innate immune system. Additionally, since adenovirus is currently being explored as viral vector for genetic vaccines against HIV and influenza, a better understanding of how adenovirus is recognized by the immune system will allow us to more carefully tailor the immune response to adenovirus-based genetic vaccines.
