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Human norovirus infection is the most common cause of viral gastroenteritis worldwide. Development of effective vaccines will be beneficial in reducing norovirus outbreaks and preventing the significant morbidity and potential mortality. However, vaccine development against norovirus infection has been hindered due to lack of cell culture and small animal model systems. Furthermore, existence of multiple genogroups and genotypes with the complex antigenic diversity and rapid evolution of these viruses have made it difficult to formulate broadly protective norovirus vaccines. Although use of norovirus-like particles (VLPs) has provided promising results for vaccine development, effective delivery and large-scale manufacture of VLP vaccines have been challenging.<P> To overcome these obstacles, live vectored vaccine can be an attractive approach. Newcastle disease virus (NDV), an avian paramyxovirus, vectored vaccines have shown encouraging results for vaccinations against many human pathogens. In this project, we propose to engineer recombinant NDVs individually expressing the capsid proteins of human and murine noroviruses and to evaluate their protective immunity against murine norovirus in mice. <P>We plan to express the capsid protein of genogroup II, genotype 4 (GII.4) norovirus, which is currently responsible for 70-80% of norovirus outbreaks worldwide. To enhance the immunogenicity and protective efficacy of our NDV vectored vaccine, we aim to optimize expression level of the capsid protein (VP1) by flanking its gene with untranslated regions (UTRs) of NDV or internal ribosome entry site (IRES) elements in the transcriptional unit.<P> The characterization of the level of VP1 expression and theirassembly into VLPs by different recombinant NDVs will enable us to identify the best construct in generating a NDV vectored norovirus vaccine. VLPs expressed by NDV will also be purified from infected allantoic fluids and Vero cells. Additionally, NDV expressing murine norovirus capsid protein and its purified VLPs from infected allantoic fluids will be included as homologous antigens for murine norovirus challenge in mice. VLPs purified from recombinant baculovirus will also be included for comparison purpose. Humoral, mucosal, and cellular immunity of live NDV vectored norovirus vaccines and of VLPs will be evaluated to identify the most effective antigen. The protective efficacy of these antigens will be evaluated in a mouse model with a murine norovirus. <P>Determination of virus load in tissue samples, virus shedding, and clinical signs will be used as the criteria to evaluate the protective efficacy of our antigens. We expect that this study will allow us to evaluate whether live NDV vectored vaccines and purified VLPs expressed by NDVs can be a novel strategy in providing immunity and protection against human norovirus infection.
Public Health Relevance: <br/> Noroviruses are the primary cause of viral gastroenteritis worldwide, and effective vaccine development can be helpful in reducing norovirus outbreaks in group settings, such as schools, restaurants, military units, and hospitals. Our study is aiming to develop an effective and safe norovirus vaccine using a live vectored vaccine approach. This approach can also be beneficial for cost-effective and large-scale manufacture of norovirus vaccines.