An inducible system to improve and stabilize the production of an extremely labile protein (E7 antigen of human papillomavirus type 16) was developed in the food-grade bacterium Lactococcus lactis. A protein carrier, the staphylococcal nuclease Nuc, was fused either to N- or C-termini of E7 protein, and the resulting hybrid proteins were rescued from intracellular proteolysis but poorly secreted by L. lactis. A synthetic propeptide (LEISSTCDA) was then fused and significantly improved the secretion efficiency of the hybrid protein Nuc-E7 by L. lactis.