Specific point mutations in Lactobacillus casei ATCC 27139 cause a phenotype switch from Lac- to Lac+

Expression of bioactive porcine interferon-alpha in Lactobacillus casei

In this study, we constructed an expression cassette containing the inducible lac promoter and the secretion signal from an S-layer protein of Lactobacillus brevis for the expression of porcine interferon-alpha (IFN-α) in Lactobacillus casei (Lb. casei). Reverse-transcriptase PCR verified the presence of porcine IFN-α mRNA in the recombinant Lb. casei. The porcine IFN-α protein expressed in the recombinant Lb. casei was identified by both Western blot analysis and ELISA. We used various pH values and induction times to optimize the yield of IFN-α, and found that induction with 0.8% lactose for 16 h under anaerobic conditions produced the highest concentrations of IFN-α. Furthermore, the activity of porcine IFN-α in the cultural supernatant was evaluated on ST cells infected with pseudorabies virus. The results revealed that porcine IFN-α inhibited virus replication in vitro. The findings of our study indicate that recombinant Lb. casei producing porcine IFN-α has great potential for use as a novel oral antiviral agent in animal healthcare.