Porcine plasma ficolin binds and reduces infectivity of porcine reproductive and respiratory syndrome virus (PRRSV) in vitro

Ficolins are collagenous lectins that bind N-acetylated glycans and participate in innate immune responses, including phagocytosis and complement activation. Related collagenous lectins such as mannan binding lectin (MBL) and surfactant proteins A and D possess antiviral activity, but this activity has not been demonstrated for ficolins. In these studies, we used purified porcine plasma ficolin α and recombinant ficolin α to assess their ability to bind and neutralize porcine reproductive and respiratory virus (PRRSV) in various assays. Recombinant ficolin α was designed with a C-terminal 6-histidine tag using a pcDNA3.1 expression vector system in CHO K1 cells. Plasma-purified and recombinant ficolin α reduced cytopathic effect of PRRSV-infected Marc-145 cells in neutralization assays and inhibited replication of infectious viral particles in a GlcNAc-dependent manner. In vitro replication determined by plaque assay was inhibited in the presence of plasma-purified ficolin α and recombinant ficolin. Immunoreactive plasma ficolin α and recombinant ficolin α also bound PRRSV-coated wells in a GlcNAc-dependent manner. These studies indicate that porcine ficolin can bind and neutralize a common arterivirus that is a major pathogen of swine.