Host Genotype and Tissue Type Determine DWV Infection Intensity.

Area of Science:

• Apiculture and Pollinator Health
• Virology and Molecular Biology
• Insect Genetics and Genomics

Background:

• Varroa mite-vectored viruses, particularly Deformed wing virus (DWV), pose a significant threat to honey bee (Apis mellifera) health, leading to increased colony losses.
• Two prevalent DWV genotypes, DWV-A and DWV-B, exhibit differential virulence and pathogenicity, complicating disease management strategies.
• Honey bee genetic stocks selected for Varroa mite resistance display varied responses to mite-vectored viruses, suggesting a complex interplay between host genetics and viral infection.

Purpose of the Study:

• To investigate the influence of honey bee host genotype on the infection levels and dissemination of Deformed wing virus (DWV) genotypes A and B.
• To determine if host genetic background affects the tissue-specific distribution of DWV genotypes within honey bees.

Main Methods:

• Newly emerged, mite-free adult honey bees from five distinct genetic stocks with varying Varroa mite resistance levels were injected with DWV isolates (genotypes A and B).
• Viral RNA levels of DWV-A and DWV-B were quantified in selected tissues over a 10-day period post-injection.
• Sham injections were used as a control to assess the impact of injury on viral loads.

Main Results:

• DWV injection significantly increased viral loads of both DWV-A and DWV-B over time, with notable interactions observed across different host genetic stocks.
• Sham injections did not affect DWV-A levels but led to increased DWV-B infections, indicating a potential stress-induced susceptibility.
• While no significant differences in overall viral dissemination were found among host stocks, distinct patterns of DWV genotype distribution were observed across body parts, with DWV-A initially higher in heads and legs, and DWV-B in heads and abdomens.

Conclusions:

• Honey bee host genotype plays a crucial role in modulating Deformed wing virus infection dynamics and influencing the tissue-specific tropism of different DWV genotypes.
• The differential dissemination of DWV-A and DWV-B to specific tissues highlights the importance of considering viral genotype and tissue tropism in conjunction with host genetics.
• These findings underscore the need for comprehensive evaluations of host-virus-vector interactions, especially in honey bee populations selected for resistance traits, to improve disease management and pollinator health.