Previously, we developed a porcine bronchial epithelial cell line designated as PBE cells and demonstrated that this cell line possesses functional Toll-like receptor 3 (TLR3), triggering the expressions of interferons (IFNs), antiviral factors, and inflammatory cytokines after its stimulation with the synthetic double-stranded ARN poly(I:C). In this work, we aimed to further characterize the PBE cell line as a reliable in vitro model for investigating swine influenza virus (SIV) infection and immunity. We evaluated the capacity of two SIV subtypes, H1N1 and H3N2, to replicate and induce cytopathic effects in PBE cells and to modulate the expressions of IFNs, antiviral factors, inflammatory cytokines, and negative regulators of the TLR signaling. We demonstrated that PBE cells are susceptible to both H1N1 and H3N2. SIV infected PBE cells inducing notable cytopathic effects as shown by the alteration of transepithelial electrical resistance (TEER) and cilia. Both SIV subtypes replicated in PBE cells in similar proportion and altered TEER values in comparable magnitudes. However, SIV H3N2 induced higher alterations of cilia than H1N1. SIV infection induced changes in all the immune factors evaluated in PBE cells. We detected quantitative differences when the subtypes H1N1 and H3N2 were compared. The fold expression changes of IFN-β, Mx1, Mx2, IFITM1, OAS1, OAS2, and OASL were higher in PBE cells infected with H3N2 than in cells challenged with H1N1. In addition, although both subtypes stimulated IL-8 expression, only the H3N2 induced IL-6 in infected PBE cells. SIV H1N1 and H3N2 also upregulated the expressions of the negative regulators A20, BCL-3, and MKP-1, while only H1N1 increased SIGIRR and Tollip. Immortalized respiratory cell lines from pigs can be useful in vitro systems for the study of viral infections and immune responses. These studies are of importance in the context of influenza infections not only for the agricultural field because pigs are natural hosts of these viruses but also because these animals serve as intermediate reservoirs of viruses that can threaten humans’ health. We demonstrated here that the PBE cell line can be a useful in vitro model to study SIV infection and immunity.

Respiratory viral infections remain a major health concern, highlighting the need for strategies that enhance host antiviral defenses. Lacticaseibacillus rhamnosus CRL1505 has demonstrated beneficial immunomodulatory effects in the respiratory tract; however, its direct effects on distinct respiratory cell populations remain incompletely characterized. Here, we evaluated the capacity of live and HK 1505 to modulate antiviral immunity in porcine bronchial epithelial (PBE) cells challenged with SIV and porcine alveolar macrophage (PAM) cells infected with PRRSV. Pretreatment with either live or HK 1505 significantly reduced infectious SIV titers in PBE cells and decreased PRRSV ORF5 expression and viral antigen detection in PAM cells, accompanied by enhanced expression of interferons and antiviral factors in both models. CRL1505 also differentially modulated inflammatory responses according to the cell type. In PAM cells, both treatments enhanced proinflammatory and regulatory cytokines, whereas in PBE cells they selectively increased IL-1β and IL-6 while reducing TNF-α, IL-8, and MCP-1. Negative regulators of innate immune signaling were also differentially modulated in both cell types. Importantly, HK 1505 retained significant antiviral and immunomodulatory activities, inducing responses that were generally similar to those observed with the viable preparation under the experimental conditions evaluated. These findings demonstrate that L. rhamnosus CRL1505 enhances antiviral responses in two distinct respiratory cell models, with differences in immunomodulatory profiles that may reflect the combined influence of cellular and viral contexts.