Topical exposure of honey bee queens to heat-inactivated Israeli acute paralysis virus does not protect their offspring against active infection

Honey bees (Apis mellifera) confront a multitude of challenges to their health throughout their lifespan and have naturally evolved protective mechanisms to defend against biological stressors. Transgenerational immune priming (TGIP) is one such defense mechanism that confers protection against bacterial infections from parents to offspring. However, it is unclear whether TGIP in honey bees also protects against viral infections, which may offer a promising pathway to decrease the honey bees’ susceptibility to viral infections. We studied our hypothesis that honey bees can prime their offspring against Israeli acute paralysis virus (IAPV). We tested the prediction that the offspring of queens exposed to thermally inactivated IAPV would exhibit higher survival of an acute IAPV infection than the offspring of sham-treated queens. Based on pilot studies that compared the effects of different inoculation methods, we topically inoculated experimental queens with heat-inactivated IAPV and compared survival of an infection with active IAPV between their offspring and offspring of sham-treated control queens. IAPV infection significantly decreased offspring survival but maternal exposure to the inactive virus did not affect this outcome. Our results fail to support the notion that maternal exposure confers the same level of protection against virus infections as observed against bacterial infections, at least in this specific instant, underscoring the intricate nature of the honey bees’ transgenerational immune response. Further development of effective strategies against viral threats to improve honey bee health is needed.