Breeding for Virus Resistance and Its Effects on Deformed Wing Virus Infection Patterns in Honey Bee Queens

Abstract

Viruses, and in particular the deformed wing virus (DWV), are considered as one of the main antagonists of honey bee health. The ‘suppressed in ovo virus infection’ trait (SOV) described for the first time that control of a virus infection can be achieved from genetically inherited traits and that the virus state of the eggs is indicative for this. This research aims to explore the effect of the SOV trait on DWV infections in queens descending from both SOV-positive (QDS+) and SOV-negative (QDS–) queens. Twenty QDS+ and QDS– were reared from each time four queens in the same starter–finisher colony. From each queen the head, thorax, ovaries, spermatheca, guts and eviscerated abdomen were dissected and screened for the presence of the DWV-A and DWV-B genotype using qRT-PCR. Queens descending from SOV-positive queens showed significant lower infection loads for DWV-A and DWV-B as well as a lower number of infected tissues for DWV-A. Surprisingly, differences were less expressed in the reproductive tissues, the ovaries and spermatheca. These results confirm that selection on the SOV trait is associated with increased virus resistance across viral genotypes and that this selection drives DWV towards an increased tissue specificity for the reproductive tissues. Further research is needed to explore the mechanisms underlying the interaction between the antiviral response and DWV.

Honey Bee Genetic Stock Determines Deformed Wing Virus Symptom Severity but not Viral Load or Dissemination Following Pupal Exposure

“…Resistance is the ability of the bee to prevent an infection from establishing or increasing after exposure, while tolerance is the ability of the individual to maintain health and functionality (i.e., reduced symptoms), even while having an infection (Locke et al, 2014;Mordecai et al, 2016a;Burgan et al, 2018). Host genotype × virus interactions may be direct through individual host immune responses to the virus or indirect via colony-level miteremoval traits (Chen and Siede, 2007;Khongphinitbunjong et al, 2015;de Guzman et al, 2019;Bouuaert et al, 2021;Weaver et al, 2021). For instance, genotype may mediate the bee's ability to detect signals such as mite-related cuticular hydrocarbons; then, these detection differences can translate into differential hygienic responses resulting in cascading differences in mite and vectored virus levels (Mondet et al, 2021;Wagoner et al, 2019).…”

Virus Prevalence in Egg Samples Collected from Naturally Selected and Traditionally Managed Honey Bee Colonies across Europe

“…However, transmission between generations by either eggs or semen is defined as vertical transmission [27]. Virus infections of queens, or their eggs, have been shown to interfere with normal egg development, to elicit a stress response in eggs [46] and to cause important health risks for the queen herself [47][48][49][50]. The importance of the honey bee queen in the viral dynamics of the colony was recently highlighted with the discovery of the 'suppressed in ovo virus infection' trait (SOV) [49].…”

“…Colonies headed by a queen laying virus-free eggs have been found to show fewer and less severe DWV infections in almost all developmental stages of both drones and workers [49]. In addition, this potential to suppress viral infections is heritable [49] and alters the tissue specificity of DWV [50]. Drone eggs are unfertilized and therefore only reflect the vertical virus transmission of the queen to her offspring [51].…”

Dynamics in vertical transmission of viruses in naturally selected and traditionally managed honey bee colonies across Europe

“…First, the detection of viral pathogens by RT-qPCR instead of gel-based RT-PCR allows for a quantification of the viral load of the eggs and lowers the detection threshold. Second, as the SOV trait is associated with increased virus resistance across DWV genotypes [63], a shift was made from screening for DWV-A only to a generic screening for the DWV complex. Overall, this research improves our understanding of how patterns of vertical transmission of viruses differ across Europe and in different evolutionary settings.…”

“…Colonies headed by a queen laying virus-free eggs showed fewer and less severe DWV infections in almost all developmental stages of both drones and workers. In addition, this potential to suppress viral infections is heritable [62] and alters the tissue specificity of DWV [63]. The aim of this study is to screen for the presence of the SOV trait in naturally surviving (NSC) and traditionally managed colonies (TMC) across Europe, along with the analysis of the effect that queen age and the time during the bee season have on the SOV trait.…”