Rotaviruses and noroviruses are the primary causes of acute potentially life-threatening gastroenteritis in infants and young children throughout the world. In countries, like the US, where effective rotavirus vaccines have been introduced, noroviruses have emerged as the major cause of pediatric gastroenteritis. The impact of norovirus disease is significant, causing an estimated 14,000 hospitalizations, 281,000 emergency department visits, and 627,000 outpatient visits, at a treatment cost of $273 million among US children under 5 years of age in 2009. Globally, norovirus infections in children lead to more than 200,000 deaths each year. To prevent norovirus disease, it is our long-term objective to develop a combined rotavirus-norovirus vaccine that can induce immunological protective responses against both viruses in vaccinated children. Our principal approach for developing the combined vaccine is to genetically engineer attenuated human strains of rotaviruses such that they serve as expression vectors for the self-assembling norovirus (NoV) capsid protein. The Specific Aims of this grant application stem from extensive proof-of-principle experiments, where we showed using 2A translation stop-restart elements that it is possible to make recombinant simian rotaviruses that encode not only the expected 12 viral proteins but also an additional foreign protein, such as the UnaG epifluorescent protein. The Specific Aims of the project are as follows: (1) To generate and characterize recombinant simian rotaviruses expressing norovirus capsid protein. In this Specific Aim, we will determine the best site for inserting a 2A element and open-reading-frame (ORF) for NoV capsid protein into the rotavirus genome required for producing maximal levels of assembled NoV particles. (2) To establish a reverse genetics system for producing recombinant human rotaviruses expressing NoV capsid protein. The recently- developed all-plasmid rotavirus reverse genetics system was designed specifically for engineering simian virus strains. In this Specific Aim, we will re-build the reverse genetics system such that it supports the formation of human G1P[8] rotaviruses, the genotype associated with most human disease. Information gained from Specific Aim 1 will when be used to generate combined rotavirus-norovirus vaccine candidate strains that can be evaluated using animal model systems.