Antiviral effects of cell-free supernatants derived from probiotic bacteria of various origins against selected bovine viruses: bovine viral diarrhoea virus 1, bovine herpesvirus 1 and Enterovirus E

Despite the significant economic impact of viral diseases on the cattle industry, there are currently no antiviral drugs licensed for use in cattle in the European Union. Furthermore, pursuant to a decision of the European Commission, the use of eighteen antiviral agents approved for the treatment of human infectious diseases has been prohibited in food-producing animals since 2023. This has created a need to identify novel, safe, and biologically compatible alternatives to currently available antiviral drugs. The aim of the present study was to evaluate the antiviral properties of cell-free supernatants (CFSs) derived from probiotic bacteria of various origins against selected bovine viruses: bovine viral diarrhoea virus 1 (BVDV-1), bovine herpesvirus 1 (BHV-1) and Enterovirus E (EV-E). Cell-free supernatants derived from Levilactobacillus brevis and Lacticaseibacillus casei , characterised by a low pH (4.1–4.8), exhibited virucidal activity against the enveloped viruses: BVDV-1 and BHV-1. Anti-replicative activity against BVDV-1 was demonstrated for supernatants derived from Levilactobacillus brevis , Lactiplantibacillus plantarum AMT14, and Bifidobacterium animalis AMT30, with the greatest inhibitory effect observed during the post-adsorption stage of infection. All supernatants derived from isolates originating from the gastrointestinal tract of animals inhibited viral replication, with the highest anti-replicative potency against BVDV-1 observed for CFS from B. animalis AMT30, with a selectivity index (SI) above 51.7. However, only CFS from Levilactobacillus brevis isolated from fish gut exhibited both virucidal and anti-replicative activities against BVDV-1. None of the tested supernatants significantly affected the non-enveloped EV-E. The results of the present in vitro study on the antiviral properties of probiotic cell-free supernatants are promising. However, further comprehensive studies are required to identify specific antiviral metabolites of the tested probiotic strains and to elucidate the mechanisms of their action. The potential future use of probiotic metabolites in bovine viral disease management would be fully aligned with the One Health approach and would not conflict with regulations restricting the use of antiviral drugs in food-producing animals.