Transmissible gastroenteritis virus

Transmissible gastroenteritis virus or Transmissible gastroenteritis coronavirus (TGEV) is a virus subspecies belonging to the family Coronaviridae, genus Alphacoronavirus, species Alphacoronavirus 1. TGEV are enveloped viruses with a positive-sense single-stranded RNA genome and a helical symmetry. The genomic size of coronaviruses ranges from approximately 28.6 kilobases.TGEV belongs to the family Coronaviridae, genus Alphacoronavirus, species Alphacoronavirus 1. It is an enveloped virus with a positive single stranded RNA genome. TGEV has three major structural proteins, which are phosphoprotein (N), integral membrane protein (E1), and large glycoprotein (E2). The N protein encapsulates the genomic RNA, and the S protein forms viral projections.The morphology of TGEV was mostly determined by electron microscopy techniques. The morphology is similar to myxovirus and oncogenic virus in that they have surface projections and an envelop. The viruses are mainly circular in shape with a diameter ranging from 100 to 150 nm including the surface projections. The projections were mainly petal-shaped attached by a very narrow stalk. The projections seemed to be very easily detached from the virus and were only found on select areas.TGEV infects pigs. In piglets less than 1 week old, the mortality rate is close to 100%. The pathology of TGEV is similar to that of other coronaviruses. Once the virus infects the host, it multiplies in the cell lining of the small intestine resulting in the loss of absorptive cells that in turn leads to shortening of villi. The infected swine then have reduced capability for digesting food and die from dehydration.The Transmissible Gastroenteritis Virus has been engineered as an expression vector. The vector was constructed by replacing the nonessential 3a and 3b ORF, which is driven by the transcription-regulating sequences (TRS) with green fluorescent protein. The resulting construct was still enteropathogenic, but with reduced growth. The infection of cells with this altered virus elicits a specific lactogenic immune response against the heterologous protein. The application of this vector is in the development of a vaccine or even gene therapy. The motivation for engineering the TGEV genome is that coronaviruses have large genomes, so they have room for insertion of foreign genes. Coronaviruses also infect the respiratory tract, and they can be used to target antigens to that area and generate some immune response.