Antigenic and pathogenic relationships of three bovine rotaviruses and a porcine rotavirus

The antigenic relationships between three bovine rotaviruses, UK, CP-1 and PP-1, and a porcine rotavirus were investigated; their pathogenicity for piglets was also assessed. After propagation and cloning in cell culture, the four viruses were used to produce convalescent and hyperimmune antisera in gnotobiotic animals. For the UK and PP-1 viruses, reciprocal virus neutralization tests gave ratios of homologous to heterologous titres in the range 57 to greater than 2300. Taking a 20-fold difference in titre to be the criterion of heterogeneity, these two viruses could be regarded as separate serotypes. The third bovine virus, CP-1, was identical to PP-1 in reciprocal neutralization tests but gave a one-way cross-reaction with UK convalescent sera, i.e. it appeared to be intermediate between the two serotypes. UK and CP-1 differed antigenically from the porcine virus as shown by homologous: heterologous neutralization titre ratios of 30 to 12 600. The bovine virus, PP-1, however, had a closer relationship with the porcine virus, the homologous: heterologous ratios ranging from 4 to 110. Oral inoculation of piglets with the bovine viruses revealed differences in their pathogenicity. Isolates UK and CP-1 caused no clinical disease and could not be passaged. However, on the first and second passages in pigs, the bovine virus PP-1 and the porcine virus produced clinical disease, excretion of virus in the faeces and sero-conversion. The results suggest that PP-1 may be a natural hybrid between a bovine and a porcine rotavirus.