DWV 3C Protease Uncovers the Diverse Catalytic Triad in Insect RNA Viruses

Ryabov²,

Markowitz³

et al. 2022

Preprint

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’.

Section: Discussionsupporting

confidence: 82%

Section: Temperature Dependence Of Bee Infectionmentioning

confidence: 99%

Section: Temperature Dependence Of Bee Infectionmentioning

confidence: 99%

See 1 more Smart Citation

Host-driven temperature dependence of viral infection in honey bees

Ryabov²,

Markowitz³

et al. 2022

Preprint

“…We tested the function of a recombinant DWV 3C protease (see Supplementary information: protease amino acid sequence ) [43]in a fluorescence resonance energy transfer (FRET) assay across vtemperatures from 5 to 50 °C. The protease (100 nM) was incubated with 80 μM of a fluorogenic DABCYL-VQAKPEMDNPNPG-EDANS-peptide substrate corresponding to the identified target peptide at the interface between the leader protein and VP2 proteins of DWV [44] ( Supplementary information: peptide amino acid sequence ) with a buffer consisting of 50 mM Tris [pH 7.0], 150 mM NaCl, 1 mM EDTA, 2 mM DTT, and 10% glycerol ( Supplementary information: reaction buffer composition) .…”

Section: Methodsmentioning

confidence: 99%

Host-driven temperature dependence of viral infection in honey bees

Ryabov²,

Markowitz

et al. 2022

Preprint

The temperature dependence of infection reflects changes in the performance of parasites and hosts. High temperatures (i.e., fever) often mitigate infection by favoring heat–tolerant hosts over heat–sensitive parasites. Honey bees exhibit an endothermic, colony-level temperature regulation that is exceptional among insects and favors resistance to several parasites. However, proliferation of viruses is heavily host–dependent, suggesting that viral infection could be linked to—not threatened by—optimum host function. To understand how temperature-driven changes in performance of viruses and hosts shape virus proliferation, we compared the temperature dependence of isolated viral enzyme activity, three honey bee traits, and infection of honey bee pupae. Viral enzyme activity varied by <2-fold over a >30°C interval that spanned the temperatures typical of ectothermic insects and honey bees. In contrast, metrics of honey bee performance peaked at high (≥35°C) temperatures and were highly temperature-sensitive, with respiration varying 8-fold over a 20°C interval and successful development requiring a narrow 8°C temperature range. Although these results suggested that hosts would gain a relative advantage over viruses with increasing temperature, 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 virus proliferation, suggesting that infection is accelerated—not curtailed—by optimum host function, contradicting predictions of infection based on the relative performance of parasites and hosts, and suggesting tradeoffs between infection resistance and host survival. Despite a 98% reduction in infection at the upper end of the colony temperature range, the narrow thermal safety margin for honey bee development might preclude the effectiveness of `fever` for controlling viruses.

“…The characterization of isolated parasite enzymes offers an opportunity to understand the intrinsic traits of unculturable viruses outside of hosts, while the use of reporter-tagged virus clones allows for controlled inoculations with traceable parasites that can be distinguished from preexisting infections. Both approaches have recently been applied to DWV 42 , 43 . Initial evaluation of the first cloned virus enzyme—a protease that cleaves the whole-genome viral polyprotein into individual proteins—showed less than 20% variation in rates of activity across a > 20 °C temperature range 43 , suggesting that the virus itself is relatively temperature-insensitive.…”

Section: Introductionmentioning

confidence: 99%

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

Ryabov

Markowitz

et al. 2023

Commun Biol

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’.