Program Project: SARS-CoV-host cell interactions and vaccine development

The emergence of the Severe Acute Respiratory Syndrome (SARS) in 2002-3 and the Middle East Respiratory Syndrome (MERS) in 2012 demonstrates that zoonotic coronaviruses (CoV) have and will likely continue to spread from zoonotic sources to infect human populations. MERS-CoV continues to circulate in camels and to spread to susceptible humans, highlighting the need to better understand the pathogenesis of diseases mediated by pathogenic human respiratory CoV. In this PPG, investigators with experience in coronavirus pathogenesis, molecular biology, immunology and vaccinology will work together to understand how virus and host factors and dysregulated innate and adaptive immune responses contribute to MERS and SARS in young and aged animals and in animals with co-morbidities. All of the projects will utilize newly developed mice expressing human MERS receptor (DPP4) in lieu of the mouse receptor (hDPP4-KI) and a mouse-virulent MERS-CoV, selected in these mice (MERSMA). Project 1 will use MERSMA to investigate the role of aging in infected mice. Project 1 is also based on published data showing that specific eicosanoids with anti-inflammatory properties and their upstream phospholipases increase during aging, contributing to a delayed immune response after SARS-CoV (and by extension, perhaps MERSMA) infection. Project 2 is based on preliminary data showing that MERS-CoV has a greater dependence on host cell proteases for virus entry than does SARS-CoV. This project will investigate unique mutations found in the surface (S) glycoprotein of MERSMA that appear to affect protease function. Project 3 will investigate how MERSMA causes more severe disease than the initial human EMC/2012 strain and will use MERSMA-infected hDPP4-KI mice to model co-morbidities, the most important risk factor for severe human MERS. This project will also investigate how hDPP4 abundance and function contribute to disease severity. Project 4 is based on published data showing that the CoV E protein has ion channel activity, is a virulence factor and contains a PDZ binding domain (PBM), which is critical for virus viability. This project will focus on how the E protein causes edema in MERSMA-infected lungs and on the role of the PBM in pathogenesis. A novel PBM in the C terminal of the ORF5 protein arose in MERSMA during passage and its role will be studied. This project will also continue to develop safe, live attenuated MERS and SARS vaccines.

Specific Goals

Project 1: To determine the mechanism of PLA2G2D upregulation and the role of PLA2G2D in vaccine responses in 12m old mice. To determine the role of PGD2-DP1 signaling in the immune response to SARS-CoV in 12 m mice. To determine whether PGD2 and PLA2G2D contribute to poorer outcomes in mice infected with MERS-CoV, another infection in which severity is age-dependent..

Project 2: Identify adaptive mutations responsible for MERS-CoV pathogenesis in mice. Determine how MA mutations affect spike structure and function. Identify the proteases activating MERS-CoV in vivo. Identify host cell factors controlling MERS spike protein evolution..

Project 3: To understand how an in vivo evolved MERS-CoV causes lethal lung disease. To investigate how DPP4 abundance and function influence MERS disease pathogenesis.

Project 4: To identify virus:host interactions that induce lung edema. To develop safe live-attenuated vaccines for MERS-CoV.