Propolis consumption ramps up the immune response in honey bees infected with bacteria

Abstract

Among their natural defenses against pathogens and parasites, honey bees coat nest cavity surfaces with propolis. Consequently, they are able to economize on immune system activation, lowering energetic costs and improving longevity. However, the mechanisms through which propolis acts to protect bees are unknown. Here we show that 0.1% propolis fed in a pollen substitute diet greatly increases activation of antimicrobial peptide genes (defensin-1, abaecin, hymenoptaecin, and apidaecin) in bees injected with Escherichia coli, compared to infected bees fed the same diets without propolis. This increase was not seen in uninfected bees fed propolis. In addition to its protective role in the hive, propolis stimulates high-level expression of the immune system response in bees challenged with microorganisms. Whether this increase translates into improved disease control will require laboratory and field tests with pathogens.