Abstract/Summary

Coronaviruses (CoV) primarily infect the upper respiratory and gastrointestinal tract of birds and mammals making them an important class of infections for agriculture, industry and human health. In 2003 an endemic of severe acute respiratory syndrome (SARS) resulted in approximately 8000 infections with a 10% mortality rate. This discovery added to four coronaviruses previously documented as being able to infect and cause disease in humans; OC43- CoV, KHU1-CoV, 229E-CoV and NL63-CoV. In 2012 Middle East respiratory syndrome coronavirus (MERS-CoV) emerged. Both SARS-CoV and MERS-CoV are thought to have originated from coronaviruses found in bats which were transmitted to man through different intermediate vectors. More recently, SARS-CoV-2 (commonly referred to as CoVid-19) emerged in December 2019 resulting in a world-wide pandemic. The coronavirus N protein is a ~45kDa protein found associated with the genome of the virus. Despite a common function in RNA binding CoV N proteins are antigenically distinct making them useful as diagnostic antigens for tests of seroconversion. To assess the MERS-CoV N protein as a diagnostic antigen a soluble full length His-tagged N protein was expressed using E. coli. Recombinant N protein was purified to homogeneity by IMAC chromatography and was observed as a single species of the predicted molecular weight with minimum breakdown. When used as a capture antigen in ELISA tests with a number of human CoV positive sera, recombinant MERS-CoV N protein was shown to react strongly with MERS-CoV positive sera but not with sera from other CoV infections. Similar data was obtained by western blot. These data suggest recombinant MERS-CoV N protein is a suitable antigen for serosurveillance. The expression of a number of other CoVN proteins to provide a mini array of N proteins for tests of a variety of human sera for their history of coronavirus infection will be described.