Characterisation of a recent virulent transmissible gastroenteritis virus from Britain with a deleted ORF 3a

Analyses of transmissible gastroenteritis virus (TGEV) and porcine respirat ory coronavirus (PRCV) isolates have suggested that tropism and pathogenici ty are influenced by the spike protein and ORF 3. In general, enteric virus es (TGEV) have been shown to contain intact spike and ORF 3 genes, whilst r espiratory isolates (PRCV) have major deletions within both regions. Virule nce has been correlated to a functional ORF 3. Here, sequence analysis of a recent isolate of virulent TGEV, revealed a variant with an intact spike g ene, but a large deletion in ORF 3a. This suggests that ORF 3a is not essen tial for enteric virulence.