Interaction of Bovine Seminal Proteins with Neutrophils

Abstract

Neutrophils ordinarily infiltrate the female reproductive tract subsequent to mating or artificial insemination, resulting in reduced fertility. Recently, it was demonstrated that equine neutrophil extracellular traps (NETs) entangled sperm in these DNA-rich structures, interfering with their normal transport through the female reproductive tract. Seminal plasma (SP) or proteinaceous extracts from SP inhibited sperm-neutrophil binding and specifically degraded sperm-activated NETs, without suppressing bactericidal activity of neutrophils. Fertility-associated antigen (FAA), a 31 kDa naturally occurring heparin-binding protein (HBP) produced by the accessory sex glands, has been shown to bind to sperm and potentiate heparin-induced capacitation. FAA shares 87% identity with DNase I-like family members, and contains two internal DNase-I-like peptide motifs. The purpose of this study was to determine if a recombinant form of FAA displayed capacitating effects associated with the native protein and to determine whether rFAA displayed DNase activity similar to SP or SP protein extracts to inhibit sperm-neutrophil binding.