Bovine lactoferrin modulates the in vitro activity of bovine peripheral blood leukocytes infected with Enterovirus eibovi

Enterovirus eibovi (EV-E) is a bovine RNA virus with debated pathogenic potential. The aim of this study was to evaluate the in vitro effects of bovine lactoferrin (bLF), an antimicrobial and immunomodulatory glycoprotein, on EV-E-infected bovine peripheral blood mononuclear cells (PBMC). The PBMC viability, phagocytic function, and lymphocyte proliferation were examined using spectrophotometric assays. Flow cytometry was used for immunophenotyping of lymphocytes, and real-time quantitative PCR for evaluation of immune-related gene expression. The safe concentration range of bLF (1-25 µg/mL) was determined on the basis of the viability and proliferation of uninfected PBMC. Bovine lactoferrin significantly influences the activity of enterovirus-infected cells, with high (10 and 25 µg/mL) and low (1, 2.5, and 5 µg/mL) protein concentrations exerting different effects. Low concentrations of bLF primarily affected unstimulated cells, increasing the expression of IFNα, IFNβ, IL2, and NFκB genes. In contrast, high concentrations of lactoferrin predominantly modulated the activity of infected cells that were additionally stimulated with a mitogen or antigen: They increased T lymphocyte proliferation; reduced phagocyte activity; increased the expression of IFNα, IL10, and NFκB; and decreased the expression of IFNγ. The increased expression of IL10 in response to high protein concentrations was also observed in unstimulated cells. The only common effect of both high and low concentrations of bLF was a decrease in the percentage of WC1+ γδ T cells following concanavalin A stimulation. Thus, bLF modulated the immune response of EV-E-infected PBMC in a concentration-dependent manner: Lower concentrations promoted early antiviral responses by inducing type I interferons and IL-2, whereas higher concentrations upregulated the anti-inflammatory cytokine IL-10, suggesting a protective effect against immune overstimulation. These findings indicate that bLF may serve as an immunomodulatory agent during enteroviral infections in cattle, with promising implications for both therapeutic and prophylactic applications.