Host-driven temperature dependence of Deformed wing virus infection in honey bee pupae

Abstract

The temperature dependence of infection reflects changes in performance of parasites and hosts. High temperatures often mitigate infection by favoring heat-tolerant hosts over heat-sensitive parasites. Honey bees exhibit endothermic thermoregulation—rare among insects—that can favor resistance to parasites. However, viruses are heavily host-dependent, suggesting that viral infection could be supported—not threatened—by optimum host function. To understand how temperature-driven changes in performance of viruses and hosts shape infection, we compared the temperature dependence of isolated viral enzyme activity, three honey bee traits, and infection of honey bee pupae. Viral enzyme activity varied <2-fold over a > 30 °C interval spanning temperatures typical of ectothermic insects and honey bees. In contrast, honey bee performance peaked at high (≥ 35 °C) temperatures and was highly temperature-sensitive. Although these results suggested that increasing temperature would favor hosts over viruses, the temperature dependence of pupal infection matched that of pupal development, falling only near pupae’s upper thermal limits. Our results reflect the host-dependent nature of viruses, suggesting that infection is accelerated—not curtailed—by optimum host function, contradicting predictions based on relative performance of parasites and hosts, and suggesting tradeoffs between infection resistance and host survival that limit the viability of bee ‘fever’.

Processing of the 3C/D Region of the Deformed Wing Virus (DWV)

“…Recently, the first enzymatic properties have been reported for recombinant DWV's 3CL protease (position 2119-2409 of the DWV polyprotein), which specifically cleaved the peptide linking the DWV leader protein-VP2 interface [40]. The N-terminus of DWV 3CL protease, which was already predicted in 2006 [26], was confirmed experimentally using a bacterial expression system approach [40,41]. After the Q 2118 of the potential N-terminal cleavage site was replaced with an alanine, no maturation at the site was observed.…”

“…Furthermore, they generated a 3CL-specific rabbit antiserum, which showed a 42 kDa 3CL protease together with the 97 kDa 3CDL precursor. In another very recent publication, Palmer-Young and colleagues used a similar system to investigate the temperature sensitivity of DVW 3CL protease in relation to the honey bee's life and honey bee's temperature tolerance [41].…”

“…Alanine substitution experiments indicated that the identity of amino acids H 2170 , C 2307 , and N 2227 is pivotal for enzyme activity, while D 2225 is of minor importance. Another study used a very similar system with a short recombinant DWV 3CL protease fragment and a fluorogenic substrate to further determine the optimum temperature of the enzyme [41].…”

A simulated natural heatwave perturbs bumblebee immunity and resistance to infection

“…Furthermore, work in other bee genera has shown variable changes in infection outcomes upon exposure to higher temperatures (e.g. Martín-Hernández et al, 2009;Palmer-Young et al, 2023;Xu & James, 2012). In addition to the differences in thermal physiology of bumblebees and other bees, varied outcomes such as these could stem from differences in how temperature affects the colonisation by the parasite on one hand, and the ability of the host to defend itself on the other.…”