Bovine rotavirus nonstructural protein 4 produced by Lactococcus lactis isantigenic and immunogenic

Rotavirus nonstructural protein 4 (NSP4) can induce diarrhea in mice. To ge t insight into the biological effects of NSP4, production of large quantiti es of this protein is necessary. We first tried to produce the protein in E scherichia coli, but the nsp4 gene proved to be unstable. The capacity of t he generally regarded as safe organism Lactococcus lactis to produce NSP4 e ither intra- or extracellularly was then investigated by using the nisin-co ntrolled expression system. Production of recombinant NSP4 (rNSP4) was obse rved in L, lactis for both locations. In spite of a very low secretion effi ciency, the highest level of production was obtained with the fusion betwee n a lactococcal signal peptide and rNSP4. Cultures of the rNSP4-secreting s train were injected into rabbits, and a specific immune response was elicit ed. The anti-rNSP4 antibodies produced in these rabbits recognized NSP4 in MA104 cells infected by rotavirus. We showed that L, lactis is able to prod uce antigenic and immunogenic rNSP4 and thus is a good organism for produci ng viral antigens.