Expression of bovine rotavirus VP8 and preparation of IgY antibodies against recombinant VP8.

Group A rotavirus is the leading cause of acute gastroenteritis in cattle and swine. Although, vaccination against this virus is an effective strategy for prevention, additional strategy to control disease is necessary. Egg yolk immunoglobulin (IgY)-based passive immunization could be a better option in preventing this disease. Bovine rotavirus (BRV) is group A rotavirus and possesses a genome of 11 segments of double-stranded RNA. The outer layer of capsid is composed of two proteins (VP7 and VP4), which induce virus neutralizing antibodies. Trypsin cleavage of VP4 produces VP8 (28 kDa) and VP5 (60 kDa) fragments. Since a number of studies have demonstrated the induction of neutralizing antibodies using VP8 subunit vaccines, we have produced IgY against the recombinant VP8. The cDNA spanning the VP8 subunit was amplified from bovine rotavirus-infected cells and cloned into pET21d(+) expression vector to generate recombinant VP8. The resulting carboxy-terminal His-tagged VP8 proteins were expressed in Escherichia coli strain BL21(DE3) by isopropyl β-D-1-thiogalactopyranoside (IPTG) induction. The recombinant proteins were purified using Ni-NTA agarose beads, and the purified protein was used as the immunizing agent to produce polyclonal antibodies in chicken. The resulting polyclonal antisera specifically recognized VP8 in Western blot assay and were able to neutralize BRV replication in cell cultures. These results demonstrate that IgY can be used in immunological assays and, in addition, in passive immunization of newborn calves against BRV.