Trans-generational immune priming involves the transfer of immunological experience,
acquired by the parents after exposure to pathogens, to protect their progeny against infections
by these pathogens. Such natural mechanisms could be exploited to prevent disease
expression in economically important insects, such as the honey bee. This mechanism
occurs when honey bee queens are exposed to the pathogenic bacterium Paenibacillus
larvae. Here, we tested whether natural or experimental exposure to Melissococcus plutonius—
another bacterium triggering a disease in honey bee larvae—reduced the susceptibility
of the queen’s progeny to infection by this pathogen. Because the immunological
response upon pathogen exposure can lead to fitness costs, we also determined whether
experimental exposure of the queens affected them or their colony negatively. Neither natural
nor experimental exposure induced protection in the honey bee larvae against the deleterious
effects of M. plutonius. Our results provided no evidence for the occurrence of transgenerational
immune priming upon exposure of the queen to M. plutonius. Whether this lack
was due to confounding genetic resistance, to unsuitable exposure procedure or to the
absence of trans-generational immune priming against this pathogen in honey bees remains
to be determined.