The protective effects of lactoferrin against murine norovirus infection through inhibition of both viral attachment and replication

•This is the first report that lactoferrin has protective effects against MNV.•Lactoferrin inhibits both viral attachment and the replication.•Lactoferrin enhances anti-viral immunity via induction of IFN-α and IFN-β.•IFN-α and IFN-β induced by lactoferrin is responsible for protective effects. The purpose of this study was to evaluate the effects of bovine lactoferrin against norovirus infection using mouse norovirus (MNV) and Raw264.7 cell in vitro. When Raw264.7 cells were infected with MNV in the presence or absence of lactoferrin, the cytotoxic damage to the infected Raw264.7 cells significantly and dose-dependently decreased and completely inhibited in the presence of 15 or 20μg/well of lactoferrin as compared with the absence of lactoferrin. Correspondingly, the MNV titers in the culture medium and intracellularly were significantly decreased in infected Raw264.7 cells treated with lactoferrin compared to control infected Raw264.7 cells. The mechanisms responsible for the protective effects of lactoferrin against MNV infection were attributed to both its inhibition of the initial MNV attachment to cells and the subsequent interference with MNV replication. Moreover, it was revealed that lactoferrin could rapidly induce the expression of anti-viral cytokine mRNA, such as IFN-α and IFN-β which involved in inhibition of MNV replication in infected Raw264.7 cells, in the early phase of infection. It was concluded that lactoferrin exerts protective effects against MNV infection through inhibition of both viral attachment and replication. The present results provide evidence that lactoferrin may be useful as a preventive and/or therapeutic anti-norovirus agent.