Melatonin as Immune Potentiator for Enhancing Subunit Vaccine Efficacy against Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is a pathogen associated with substantial economic losses in the dairy cattle industry. Currently, there are no effective vaccines against BVDV. Melatonin (MT) has been shown to have anti-inflammatory and anti-viral properties, and the use of MF59 in vaccines significantly enhances vaccine efficiency. Here, MT and MF59 were added into the E(rns)-LTB vaccine. Subsequently, their inhibitory activity on the NF-κB signaling pathway in Mardin-Darby Bovine Kidney cells and the hippocampus was assessed using western blot and quantitative reverse transcription PCR. The findings revealed that MT in the E(rns)-LTB vaccine decreases the phosphorylation of p65 proteins caused by BVDV infection. In addition, MT decreased the mRNA levels of IL-1β and IL-6 in vitro, but increased the production of IFN-α, IFN-β, Mx1 in vitro, brain-derived neurotrophic factor, cyclic amp response element-binding protein, and the stem cell factor in vivo. Furthermore, treatment with E(rns)-LTB + MF59 + MT stimulated the production of T lymphocytes, alleviated pathological damage, decreased expressions of BVDV antigen, and tight junction proteins in mice. These findings imply that MT has potential for use in the E(rns)-LTB vaccine to inhibit BVDV infection and regulate the immune responses of T-cells by inhibiting the NF-κB signaling pathway.