The In-vitro Antiviral Activity of Lactobacillus casei MCJ Protein-based Metabolites on Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is a ubiquitous immunosuppressive etiological agent that is economically important for a wide host range in the livestock industry. Lactobacillus spp. has widely been using in the field of management and treatment of gastro-enteric disease for both human and animal. The ability of Lactobacillus casei MCJ (L. casei) protein-based metabolized (LPM) to suppress BVDV infection in Madin-Darby Bovine Kidney (MDBK) cell line was demonstrated in this study. The protein-based metabolites were extracted from the cultured L. casei to obtain the safest and beneficial form of the probiotic bacteria. The results of cytotoxicity test reveal that LPM has no cytotoxic effect and the cell viability remains more than 80% even after the cells are treated with 3000 μg/mL of LPM. In comparing positive control, 3000 μg/mL concentration of LPM reduced plaque formation by 73.45% whereas 1000, 100 and 10 μg/mL reduced 65.95%, 39.67% and 4.02% consecutively. The results of plaque formation unit (pfu) assay showed that LPM can reduce the viral infection rate. To know the mechanism of LPM for anti-BVDV activity, MDBK cells were exposed to LPM before, after and co-incubation of virus infection. The co-treatment of LPM with BVDV revealed the best results for the decreased viral protein expression by Western blot, RNA copy number by Quantitative real-time PCR and fewer BVDV infected cells by Immunofluorescences assay. The results suggest that the LPM has a potential anti-BVDV activity which could be a prospective application for the prevention and control of BVDV infection in animal.