Host genotype and tissue type determine DWV infection intensity

Authors: Penn, Hannah; Simone-Finstrom, Michael; Lang, Sarah; Chen, Yanping - Judy; HEALY, KRISTEN - LSU Agcenter

Submitted to: Frontiers in Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2021
Publication Date: 11/4/2021
Citation: Penn, H., Simone-Finstrom, M., Lang, S.A., Chen, Y., Healy, K. 2021. Host genotype and tissue type determine DWV infection intensity. Frontiers in Insect Science. 1:1-12. Article: 756690. https://doi.org/10.3389/finsc.2021.756690.
DOI: https://doi.org/10.3389/finsc.2021.756690

Interpretive Summary: Varroa mites, common honey bee parasites, are known to transmit several strains of Deformed wing virus to honey bees. All strains of this virus can result in shriveled wings and individual bee and colony death if present in high enough levels. Prior work has shown that the different DWV strains may be more or less destructive than each other, with the more dangerous strain varying with the study. However, no prior work has documented if these strains infect different body parts or at different times from each other. Additionally, honey bees have been bred to be resistant to the virus-transmitting mites and, potentially, to the viruses that the mites vector. The goal of our study was to determine if two DWV strains (A & B) differ in how they spread throughout the bodies of different honey bees. To test this, we injected adult bees from five stocks of honey bees having different abilities to resist varroa mite infestation with DWV then monitored the levels of the two DWV strains in different bee body parts over 10 days. We found that body parts differed in their total amount of each virus strain and the time at which the strains peaked. While there were no bee breed-related differences in how the viruses impact the different body parts, we did find that the different bee breeds impacted the overall levels of both virus strains. Our work indicates that DWV strains impact bees differently and that bees bred to be resistant to the DWV vector (varroa mites) may also exhibit differences in their abilities to resist DWV.

Technical Abstract: Varroa mite-vectored viruses such as Deformed wing virus (DWV) are of great concern for honey bee health as they can cause disease in individuals and increase colony mortality. Two genotypes of DWV (A & B) are prevalent in the United States and may have differential virulence and pathogenicity. Honey bee genetic stocks bred to resist Varroa mites also exhibit differential infection responses to the Varroa mite-vectored viruses. The goal of this project was to determine if interactions between host genotype could influence the overall infection levels and dissemination of DWV within honey bees. To do this, we injected DWV isolated from symptomatic adult bees into mite-free, newly emerged adult bees from five genetic stocks with varying levels of resistance to Varroa mites. We measured DWV-A and DWV-B dissemination among tissues relevant to different routes of transmission or general health outcomes for ten days. Injury from sham injections did not increase DWV-A levels but did increase DWV-B infections. DWV injection increased both DWV-A and DWV-B levels over time with significant host stock interactions. While we did not observe any differences in viral dissemination among host stocks, we found differences in virus genotype dissemination to different body parts. DWV-A exhibited the highest initial levels in heads and legs while the highest initial levels of DWV-B were found in heads and abdomens. These interactions underscore the need to evaluate viral genotype and tissue specificity in conjunction with host genotype, particularly when the host has been selected for traits relative to virus-vector and virus resistance.