Project 1

Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) arecoronavirus-induced human respiratory diseases with high case-fatality rates. Disease is especiallysevere in aged populations. In the previous funding period, we showed that age-dependent increasesin prostaglandin D2 (PGD2) and an upstream phospholipase A2, PLA2G2D contributed to poorimmune responses and decreased survival. The lung is in a state of chronic inflammation, resultingfrom continued exposure to environmental antigens. We postulated that PLA2G2D, which has anti-inflammatory properties, is upregulated to counter this low grade inflammation, resulting in delayedresponses to innocuous antigens but also to rapidly replicating viruses like MERS-CoV and SARS-CoV. In contrast, genetic absence of DP1, the PGD2 receptor on myeloid cells, appears to result inpoor respiratory dendritic cell activation suggesting that PGD2-DP1 signaling may have pro-inflammatory properties at early times after infection. Our central hypothesis is that small lipidmediators are major factors in the inflammatory milieu in the lung, affecting many aspects of theimmune response to MERS-CoV, SARS-CoV and other respiratory pathogens. This hypothesis will beapproached in the following specific aims: 1. To determine the mechanism of PLA2G2D upregulationand the role of PLA2G2D in vaccine responses in 12m old mice. CoV replication includes extensivecellular membrane rearrangements. The role between these rearrangements, the induction of oxidativestress and the upregulation of PLA2G2D will be investigated. 2. To determine the role of PGD2-DP1signaling in the immune response to SARS-CoV in 12 m mice. The absence of PGD2-DP1 signalingresults in diminished rDC activation and type I IFN (IFN-I) expression and increased inflammasomeactivation. Our goal is to determine whether changes in inflammasome activation are the majorpathogenic effect of absent PGD2-DP1 signaling or if other factors are also involved. 3. To determinewhether disease severity in murine MERS is age-dependent and whether PGD2 and PLA2G2Dcontribute to poorer outcomes. Using our newly developed hDPP4-KI mice and mouse-adaptedMERS-CoV, we will determine whether MERS-CoV in mice also causes an age-dependent disease.We will also assess whether changes in eicosanoid expression contribute to more severe disease.MERS-CoV, unlike SARS-CoV, productively infects macrophages. In this aim we will determinewhether productive infection of human and murine macrophages modulates PLA2G2D expression.