Bifidobacterium Animalis Subsp. Lactis BB-12 Primes Epithelial Antiviral Defenses and Restricts Influenza A Virus Replication in Human Intestinal Organoid-Derived Monolayers

Viral infections with gastrointestinal involvement remain a significant global health burden with limited therapeutic options. While probiotics show antiviral potential, their impact on primary human intestinal epithelial defenses is poorly defined. This study utilized human intestinal organoid-derived monolayers (ODMs), generated from the non-inflamed mucosa of patients with inflammatory bowel disease, to examine how Bifidobacterium animalis ssp. lactis BB-12 (BB-12) and Lacticaseibacillus rhamnosus GG (LGG) modulate mucosal antiviral pathways. Unlike conventional Caco-2 cells, ODMs preserved physiological cellular diversity and intact innate signaling. Expression of viral receptors and interferon (IFN)-stimulated genes (ISGs) was quantified by RT-qPCR, while the effector 2'-5'-oligoadenylate synthetase 1 (OAS1) was also assessed by immunofluorescence and flow cytometry. Both probiotic strains modulated IFN-associated pathways; however, BB-12 induced a markedly stronger antiviral transcriptional response than LGG. Notably, OAS1 exhibited cell type-specific regulation; while goblet cells showed high basal levels, both probiotics enhanced OAS1 expression selectively in ileal enterocytes. Despite this shared effect, only BB-12 pretreatment significantly restricted Influenza A (H1N1) replication in ileal ODMs, whereas LGG did not significantly affect viral replication. These findings establish human ODMs as a superior platform for probiotic immunology, suggesting that BB-12 more effectively shapes epithelial antiviral "set-points" and highlighting OAS1 as a sensitive component of a broader antiviral program.