Porcine epidemic diarrhea virus (PEDV) is an infectious and highly contagious swine virus. Recently, outbreaks of severe PED disease have been reported in the USA and Canada. A severe PEDV epizootic has been affecting pigs of all ages and is characterized by high mortality rates among suckling piglets. A significant economic loss attributed to the disease is estimated as $125,000 for a 1000 sow herd. Our goal is to develop a live virus vaccine specifically directed towards sows to protect suckling piglets against disease. Despite long-term efforts, effective vaccines to prevent other enteric coronavirus infections of animals remain elusive, although modified live, but not killed vaccines, have induced the most consistent protection. Attenuated virus strains for these vaccines were obtained by serial passages of the virus on cultured monkey cells and as such it takes a long time to develop these types of vaccines. Another disadvantage of these vaccines is lack of a mechanism to “Differentiate Infected from Vaccinated Animals” (i.e. DIVA potential). New genomic approaches such as Reverse Genetics can help to overcome these drawbacks. Rapid response and control of emerging pathogens requires an approach to quickly generate full-length cDNA from which the virus can be cloned, allowing for genetic manipulation of the viral genome. Therefore, the proposed project has the following objectives: (1) to construct a full-length infectious cDNA clone of a highly virulent North American PEDV strain; (2) to introduce attenuating mutations into the viral genome; (3) to characterize humoral immune response to PEDV in order to introduce strategic DIVA mutations into the viral genome.