Reproductive and vertical transmission consequences of deformed wing virus type B (DWV-B) in naturally infected honey bee queens

DWV-B is an economically significant pathogen in honey bees and has been rapidly replacing the previously dominant DWV-A. In association with Varroa mite, DWV-B is considered a major contributor to honey bee colony mortality. While DWV-B infects all life stages and castes of honey bees, its impact on queen reproductive performance and transgenerational transmission remains poorly understood. To address this gap, we investigated the impacts of DWV-B on queen reproductive traits and its consequences on produced eggs. Two groups of queens of similar age were categorized based on DWV-B titers in their eggs into high- and low-infected groups. We compared the number and size of eggs laid by each group. Queens were then sacrificed and dissected into different body parts to assess viral load and immune gene expression across different tissues. Using RT-qPCR, we quantified DWV-B titer and expression of twelve immune-related genes in dissected tissues, including worker- and drone-destined eggs. Our results showed that ovaries from highly infected queens weighed significantly less than those from low-infected queens. However, no significant differences were observed in the number and size of worker-destined eggs between the groups. Molecular analysis revealed that the ovaries had significantly lower viral loads compared to other tissues. While immune gene expression varied across most tissues, it was not significantly different in the ovaries or the produced eggs, leading to poor transgenerational effects. These findings provide valuable insights for developing effective breeding strategies aimed at enhancing virus resistance in honey bees.