PS5-15. The Antiviral Potential of Lactococcus Lactis A1-2 In-vitro.

Abstract Viral diseases such as influenza continue to challenge swine health, productivity and are a risk for zoonoses. High mutation rates can limit vaccine effectiveness, creating a need for complementary strategies that help reduce viral spread. Probiotics are known to support gut health, enhance epithelial function, and influence immune activity, and emerging work suggests some strains may also interfere directly with viral infections. In this study, the antiviral properties of Lactococcus lactis A1-2, a fruit originated isolate, were evaluated using porcine intestinal epithelial (IPEC-J2) cells and avian erythrocytes as model systems. A series of time-of-addition assays showed that the A1-2 culture supernatant consistently reduced H1N1 infectivity. The reduction was strongest when the virus and supernatant were applied to host cells at the same time, suggesting that its antiviral activity is most effective during early infection. Hemagglutination assays further demonstrated that A1-2 supernatant sharply reduced HA titers, including after pH neutralization, indicating activity beyond acidity alone. We also assessed how A1-2 affected epithelial responses during infection. The culture supernatant had little influence on gene expression, but live A1-2 increased CLDN1, a tight-junction protein important for maintaining epithelial barriers, and lowered IL-6, an inflammatory marker. Together, these shifts point toward improved epithelial stability during infection. To investigate potential metabolite involvement, preliminary untargeted metabolomics analysis was performed on the supernatant, revealing a few metabolites previously reported to have antiviral activity. Further confirmation and qualification of these secreted compounds are underway. Probiotic validation assays showed that A1-2 tolerates acidic environments but has reduced metabolic activity under bile exposure, indicating partial resilience through the gastrointestinal tract. A1-2 demonstrates consistent antiviral activity, driven primarily by direct disruption of viral infectivity and supported by enhanced epithelial barrier function. Our study provides insights into A1-2 as a probiotic with antiviral potential for improving swine intestine health.