The venom gland transcriptome of the parasitoid wasp Nasonia vitripennis highlights the importance of novel genes in venom function

Host size overrides maternal effects on the development of a secondary hyperparasitoid wasp

Unraveling the numerous factors that drive phenotypic variation in trait expression among animals has long presented a significant challenge. Whereas traits like growth and adult size are often heritable and are passed on from one generation to the next, these can be significantly affected by the quality and quantity of resources provided by one or both parents to their offspring. In many vertebrates, such as birds and mammals, parents raise their young until adult, providing food, shelter, and protection. On the other hand, in insects, there is often little or no parental care, and the young are left to fend for themselves. Despite that, some insects can enhance the growth of their offspring. In parasitoid wasps, for example, mothers inject biochemical factors, including venoms, teratocytes, and virus-like particles into the host that increase host quality by regulating the nutritional milieu. However, it is not known whether maternal size is positively correlated with host regulation. Here, we evaluate maternal and host size-related effects on the development of an asexually reproducing (= female only) secondary idiobiont ectoparasitoid, Gelis agilis on pre-pupae in cocoons of its host, the primary parasitoid, Cotesia glomerata. Females G. agilis from 2 adult size classes, "small" (mean 0.7 mg) or "large" (mean 1.2 mg), were allowed to parasitize cocoons of differing size along a continuum from ~1.2 mg to ~4.0 mg, and the body size and development time of their offspring were measured. In both body size classes of G. agilis mothers, there was a strong correlation between host size and offspring size. However, there was no effect of adult G. agilis size on this parameter: for a given host size, the size of G. agilis offspring did not differ between small and large mothers. Our results reveal that host quality is mostly pre-determined, irrespective of maternal size.

Lipid Metabolism in Parasitoids and Parasitized Hosts

Parasitoids have an exceptional lifestyle where juvenile development is spent on or in a single host insect, but the adults are free-living. Unlike parasites, parasitoids kill the host. How parasitoids use such a limiting resource, particularly lipids, can affect chances to survive and reproduce. In part 1, we describe the parasitoid lifestyle, including typical developmental strategies. Lipid metabolism in parasitoids has been of interest to researchers since the 1960s and continues to fascinate ecologists, evolutionists, physiologists, and entomologists alike. One reason of this interest is that the majority of parasitoids do not accumulate triacylglycerols as adults. Early research revealed that some parasitoid larvae mimic the fatty acid composition of the host, which may result from a lack of de novo triacylglycerol synthesis. More recent work has focused on the evolution of lack of adult triacylglycerol accumulation and consequences for life history traits. In part 2 of this chapter, we discuss research efforts on lipid metabolism in parasitoids from the 1960s onwards. Parasitoids are also master manipulators of host physiology, including lipid metabolism, having evolved a range of mechanisms to affect the release, synthesis, transport, and take-up of lipids from the host. We lay out the effects of parasitism on host physiology in part 3 of this chapter.

Aphidius ervi venom regulates Buchnera contribution to host nutritional suitability

The association between the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), and the endophagous parasitoid wasp Aphidius ervi Haliday (Hymenoptera: Braconidae) offers a unique model system for studying the molecular mechanisms underlying the complex interactions between the parasitoid, its host and the associated primary symbiont. Here, we investigate in vivo the functional role of the most abundant component of A. ervi venom, Ae-γ-glutamyl transpeptidase (Ae-γ-GT), which is known to induce host castration. Microinjections of double-stranded RNA into A. ervi pupae stably knocked down Ae-γ-GT1 and Ae-γ-GT2 paralogue genes in newly emerged females. These females were used to score the phenotypic changes both in parasitized hosts and in the parasitoid's progeny, as affected by a venom blend lacking Ae-γ-GT. Ae-γ-GT gene silencing enhanced growth both of host and parasitoid, supported by a higher load of the primary bacterial symbiont Buchnera aphidicola. Emerging adults showed a reduced survival and fecundity, suggesting a trade-off with body size. This demonstrates in vivo the primary role of Ae-γ-GT in host ovary degeneration and suggests that this protein counterbalances the proliferation of Buchnera likely triggered by other venom components. Our study provides a new approach to unravelling the complexity of aphid parasitoid venom in vivo, and sheds light on a novel role for Ae-γ-GT in host regulation.

The venom composition and parthenogenesis mechanism of the parasitoid wasp Microctonus hyperodae, a declining biocontrol agent

A biocontrol system in New Zealand using the endoparasitoid Microctonus hyperodae is failing, despite once being one of the most successful examples of classical biocontrol worldwide. Though it is of significant economic importance as a control agent, little is known about the genetics of M. hyperodae. In this study, RNA-seq was used to characterise two key traits of M. hyperodae in this system, the venom, critical for the initial success of biocontrol, and the asexual reproduction mode, which influenced biocontrol decline. Expanded characterisation of M. hyperodae venom revealed candidates involved in manipulating the host environment to source nutrition for the parasitoid egg, preventing a host immune response against the egg, as well as two components that may stimulate the host's innate immune system. Notably lacking from the venom-specific expression list was calreticulin, as it also had high expression in the ovaries. In-situ hybridisation revealed this ovarian expression was localised to the follicle cells, which may result in the deposition of calreticulin into the egg exochorion. Investigating the asexual reproduction of M. hyperodae revealed core meiosis-specific genes had conserved expression patterns with the highest expression in the ovaries, suggesting M. hyperodae parthenogenesis involves meiosis and that the potential for sexual reproduction may have been retained. Upregulation of genes involved in endoreduplication provides a potential mechanism for the restoration of diploidy in eggs after meiosis.

Mining Amphibian and Insect Transcriptomes for Antimicrobial Peptide Sequences with rAMPage

Antibiotic resistance is a global health crisis increasing in prevalence every day. To combat this crisis, alternative antimicrobial therapeutics are urgently needed. Antimicrobial peptides (AMPs), a family of short defense proteins, are produced naturally by all organisms and hold great potential as effective alternatives to small molecule antibiotics. Here, we present rAMPage, a scalable bioinformatics discovery platform for identifying AMP sequences from RNA sequencing (RNA-seq) datasets. In our study, we demonstrate the utility and scalability of rAMPage, running it on 84 publicly available RNA-seq datasets from 75 amphibian and insect species—species known to have rich AMP repertoires. Across these datasets, we identified 1137 putative AMPs, 1024 of which were deemed novel by a homology search in cataloged AMPs in public databases. We selected 21 peptide sequences from this set for antimicrobial susceptibility testing against Escherichia coli and Staphylococcus aureus and observed that seven of them have high antimicrobial activity. Our study illustrates how in silico methods such as rAMPage can enable the fast and efficient discovery of novel antimicrobial peptides as an effective first step in the strenuous process of antimicrobial drug development.

Identification and Functional Characterization of Toxoneuron nigriceps Ovarian Proteins Involved in the Early Suppression of Host Immune Response

The endophagous parasitoid Toxoneuron nigriceps (Viereck) (Hymenoptera, Braconidae) of the larval stages of the tobacco budworm Heliothis virescens (Fabricius) (Lepidoptera, Noctuidae) injects the egg, the venom, the calyx fluid, which includes a Polydnavirus (T. nigriceps BracoVirus: TnBV) and the Ovarian Proteins (OPs) into the host body during oviposition. The host metabolism and immune system are disrupted prematurely shortly after parasitization by the combined action of the TnBV, venom, and OPs. OPs are involved in the early suppression of host immune response, before TnBV infects and expresses its genes in the host tissues. In this work, we evaluated the effect of HPLC fractions deriving from in toto OPs. Two fractions caused a reduction in hemocyte viability and were subsequently tested to detect changes in hemocyte morphology and functionality. The two fractions provoked severe oxidative stress and actin cytoskeleton disruption, which might explain the high rate of hemocyte mortality, loss of hemocyte functioning, and hence the host’s reduced hemocyte encapsulation ability. Moreover, through a transcriptome and proteomic approach we identify the proteins of the two fractions: eight proteins were identified that might be involved in the observed host hemocyte changes. Our findings will contribute to a better understanding of the secreted ovarian components and their role in parasitoid wasp strategy for evading host immune responses.

An integrated transcriptomic and proteomic approach to identify the main Torymus sinensis venom components

During oviposition, ectoparasitoid wasps not only inject their eggs but also a complex mixture of proteins and peptides (venom) in order to regulate the host physiology to benefit their progeny. Although several endoparasitoid venom proteins have been identified, little is known about the components of ectoparasitoid venom. To characterize the protein composition of Torymus sinensis Kamijo (Hymenoptera: Torymidae) venom, we used an integrated transcriptomic and proteomic approach and identified 143 venom proteins. Moreover, focusing on venom gland transcriptome, we selected additional 52 transcripts encoding putative venom proteins. As in other parasitoid venoms, hydrolases, including proteases, phosphatases, esterases, and nucleases, constitute the most abundant families in T. sinensis venom, followed by protease inhibitors. These proteins are potentially involved in the complex parasitic syndrome, with different effects on the immune system, physiological processes and development of the host, and contribute to provide nutrients to the parasitoid progeny. Although additional in vivo studies are needed, initial findings offer important information about venom factors and their putative host effects, which are essential to ensure the success of parasitism.

Quantitative trait loci involved in the reproductive success of a parasitoid wasp

Dissecting the genetic basis of intraspecific variations in life history traits is essential to understand their evolution, notably for potential biocontrol agents. Such variations are observed in the endoparasitoid Cotesia typhae (Hymenoptera: Braconidae), specialized on the pest Sesamia nonagrioides (Lepidoptera: Noctuidae). Previously, we identified two strains of C. typhae that differed significantly for life history traits on an allopatric host population. To investigate the genetic basis underlying these phenotypic differences, we used a quantitative trait locus (QTL) approach based on restriction site-associated DNA markers. The characteristic of C. typhae reproduction allowed us generating sisters sharing almost the same genetic content, named clonal sibship. Crosses between individuals from the two strains were performed to generate F2 and F8 recombinant CSS. The genotypes of 181 clonal sibships were determined as well as the phenotypes of the corresponding 4,000 females. Informative markers were then used to build a high-quality genetic map. These 465 markers spanned a total length of 1,300 cM and were organized in 10 linkage groups which corresponded to the number of C. typhae chromosomes. Three QTLs were detected for parasitism success and two for offspring number, while none were identified for sex ratio. The QTLs explained, respectively, 27.7% and 24.5% of the phenotypic variation observed. The gene content of the genomic intervals was investigated based on the genome of C. congregata and revealed 67 interesting candidates, as potentially involved in the studied traits, including components of the venom and of the symbiotic virus (bracovirus) shown to be necessary for parasitism success in related wasps.

Insight into the Functional Diversification of Lipases in the Endoparasitoid Pteromalus puparum (Hymenoptera: Pteromalidae) by Genome-scale Annotation and Expression Analysis

Lipases play essential roles in digestion, transport, and processing of dietary lipids in insects. For parasitoid wasps with a unique life cycle, lipase functions could be multitudinous in particular. Pteromalus puparum is a pupal endoparasitoid of butterflies. The female adult deposits eggs into its host, along with multifunctional venom, and the developing larvae consume host as its main nutrition source. Parasitoid lipases are known to participate in the food digestion process, but the mechanism remains unclear. P. puparum genome and transcriptome data were interrogated. Multiple alignments and phylogenetic trees were constructed. We annotated a total of 64 predicted lipase genes belonging to five lipase families and suggested that eight venom and four salivary lipases could determine host nutrition environment post-parasitization. Many putative venom lipases were found with incomplete catalytic triads, relatively long β9 loops, and short lids. Data analysis reveals the loss of catalytic activities and weak triacylglycerol (TAG) hydrolytic activities of lipases in venom. Phylogenetic trees indicate various predicted functions of lipases in P. puparum. Our information enriches the database of parasitoid lipases and the knowledge of their functional diversification, providing novel insight into how parasitoid wasps manipulate host lipid storage by using venom lipases.

Venomics of the ectoparasitoid wasp Bracon nigricans

BACKGROUND

Venom is one of the most important sources of regulation factors used by parasitic Hymenoptera to redirect host physiology in favour of the developing offspring. This has stimulated a number of studies, both at functional and "omics" level, which, however, are still quite limited for ectophagous parasitoids that permanently paralyze and suppress their victims (i.e., idiobiont parasitoids).

RESULTS

Here we present a combined transcriptomic and proteomic study of the venom of the generalist idiobiont wasp Bracon nigricans, an ectophagous larval parasitoid of different lepidopteran species, for which we recently described the host regulation strategy and the functional role of the venom in the induction of physiological changes in parasitized hosts. The experimental approach used led to the identification of the main components of B. nigricans venom involved in host regulation. Enzymes degrading lipids, proteins and carbohydrates are likely involved in the mobilization of storage nutrients from the fat body and may concurrently be responsible for the release of neurotoxic fatty acids inducing paralysis, and for the modulation of host immune responses.

CONCLUSION

The present work contributes to fill the gap of knowledge on venom composition in ectoparasitoid wasps, and, along with our previous physiological study on this species, provides the foundation on which to develop a functional model of host regulation, based both on physiological and molecular data. This paves the way towards a better understanding of parasitism evolution in the basal lineages of Hymenoptera and to the possible exploitation of venom as source of bioinsecticidal molecules.

Evaluating the evolution and function of the dynamic Venom Y protein in ectoparasitoid wasps

Venom of the parasitoid wasp Nasonia vitripennis changes the metabolism and gene expression in its fly host Sarcophaga bullata to induce developmental arrest, suppression of the immune response and various other venom effects. Yet, the venom of ectoparasitoid wasps has not been fully characterized. A major component of N. vitripennis venom is an uncharacterized, high-expressing protein referred to as Venom Y. Here we describe the evolutionary history and possible functions of this venom protein. We found that Venom Y is a relatively young gene that has duplicated to form two distinct paralogue groups. A copy of Venom Y has been recruited as a venom protein in at least five wasp species. Functional analysis found that Venom Y affects detoxification and immunity genes in envenomated fly hosts. Many of these genes are fat-body specific, suggesting that Venom Y may have a targeted effect on fat body tissue. We also show that Venom Y may mitigate negative effects of other venom proteins. Finally, protein sequencing indicates that Venom Y is post-translationally modified. This study contributes to elucidating parasitoid venom by using RNA interference knockdown to investigate venom protein function in the context of the whole venom cocktail.

An Ovarian Protein Involved in Passive Avoidance of an Endoparasitoid To Evade Its Host Immune Response

Through a combination of transcriptomic and proteomic analyses, we identified 817 secreted ovarian proteins from an endoparasitoid wasp, Cotesia chilonis, of which five proteins are probably involved in passive evasion. The results of an encapsulation assay revealed that one of these passive evasion-associated proteins (Crp32B), a homologue of a 32-kDa protein (Crp32) from C. rubecula, could protect resin beads from being encapsulated by host hemocytes in a dose-dependent manner. Crp32B is transcribed in ovarian cells, nurse cells, follicular cells, and oocytes, and the protein is located throughout the ovary and on the egg surface. Moreover, Crp32B has antigenic similarity to several host components. These results indicate that C. chilonis may use molecular mimicry as a mechanism to avoid host cellular immune response.

Parasitoid Jewel Wasp Mounts Multipronged Neurochemical Attack to Hijack a Host Brain

The parasitoid emerald jewel wasp Ampulex compressa induces a compliant state of hypokinesia in its host, the American cockroach Periplaneta americana through direct envenomation of the central nervous system (CNS). To elucidate the biochemical strategy underlying venom-induced hypokinesia, we subjected the venom apparatus and milked venom to RNAseq and proteomics analyses to construct a comprehensive "venome," consisting of 264 proteins. Abundant in the venome are enzymes endogenous to the host brain, including M13 family metalloproteases, phospholipases, adenosine deaminase, hyaluronidase, and neuropeptide precursors. The amphipathic, alpha-helical ampulexins are among the most abundant venom components. Also prominent are members of the Toll/NF-κB signaling pathway, including proteases Persephone, Snake, Easter, and the Toll receptor ligand Spätzle. We find evidence that venom components are processed following envenomation. The acidic (pH∼4) venom contains unprocessed neuropeptide tachykinin and corazonin precursors and is conspicuously devoid of the corresponding processed, biologically active peptides. Neutralization of venom leads to appearance of mature tachykinin and corazonin, suggesting that the wasp employs precursors as a prolonged time-release strategy within the host brain post-envenomation. Injection of fully processed tachykinin into host cephalic ganglia elicits short-term hypokinesia. Ion channel modifiers and cytolytic toxins are absent in A. compressa venom, which appears to hijack control of the host brain by introducing a "storm" of its own neurochemicals. Our findings deepen understanding of the chemical warfare underlying host-parasitoid interactions and in particular neuromodulatory mechanisms that enable manipulation of host behavior to suit the nutritional needs of opportunistic parasitoid progeny.

Arthropod venoms: Biochemistry, ecology and evolution

Comprising of over a million described species of highly diverse invertebrates, Arthropoda is amongst the most successful animal lineages to have colonized aerial, terrestrial, and aquatic domains. Venom, one of the many fascinating traits to have evolved in various members of this phylum, has underpinned their adaptation to diverse habitats. Over millions of years of evolution, arthropods have evolved ingenious ways of delivering venom in their targets for self-defence and predation. The morphological diversity of venom delivery apparatus in arthropods is astounding, and includes extensively modified pedipalps, tail (telson), mouth parts (hypostome), fangs, appendages (maxillulae), proboscis, ovipositor (stinger), and hair (urticating bristles). Recent investigations have also unravelled an astonishing venom biocomplexity with molecular scaffolds being recruited from a multitude of protein families. Venoms are a remarkable bioresource for discovering lead compounds in targeted therapeutics. Several components with prospective applications in the development of advanced lifesaving drugs and environment friendly bio-insecticides have been discovered from arthropod venoms. Despite these fascinating features, the composition, bioactivity, and molecular evolution of venom in several arthropod lineages remains largely understudied. This review highlights the prevalence of venom, its mode of toxic action, and the evolutionary dynamics of venom in Arthropoda, the most speciose phylum in the animal kingdom.

First extensive characterization of the venom gland from an egg parasitoid: structure, transcriptome and functional role

The venom gland is a ubiquitous organ in Hymenoptera. In insect parasitoids, the venom gland has been shown to have multiple functions including regulation of host immune response, host paralysis, host castration and developmental alteration. However, the role played by the venom gland has been mainly studied in parasitoids developing in larval or pupal hosts while little is known for parasitoids developing in insect eggs. We conducted the first extensive characterization of the venom of the endoparasitoid Ooencyrtus telenomicida (Vassiliev), a species that develops in eggs of the stink bug Nezara viridula (L.). In particular we investigated the structure of the venom apparatus, its functional role and conducted a transcriptomic analysis of the venom gland. We found that injection of O. telenomicida venom induces: 1) a melanized-like process in N. viridula host eggs (host-parasitoid interaction), 2) impairment of the larval development of the competitor Trissolcus basalis (Wollaston) (parasitoid-parasitoid interaction). The O. telenomicida venom gland transcriptome reveals a majority of digestive enzymes (peptidases and glycosylases) and oxidoreductases (laccases) among the most expressed genes. The former enzymes are likely to be involved in degradation of the host resources for the specific benefit of the O. telenomicida offspring. In turn, alteration of host resources caused by these enzymes may negatively affect the larval development of the competitor T. basalis. We hypothesize that the melanization process induced by venom injection could be related to the presence of laccases, which are multicopper oxidases that belong to the phenoloxidases group. This work contributed to a better understanding of the venom in insect parasitoids and allowed to identify candidate genes whose functional role can be investigated in future studies.

Differential gene expression is not required for facultative sex allocation: a transcriptome analysis of brain tissue in the parasitoid wasp Nasonia vitripennis

Whole-transcriptome technologies have been widely used in behavioural genetics to identify genes associated with the performance of a behaviour and provide clues to its mechanistic basis. Here, we consider the genetic basis of sex allocation behaviour in the parasitoid wasp Nasonia vitripennis. Female Nasonia facultatively vary their offspring sex ratio in line with Hamilton's theory of local mate competition (LMC). A single female or 'foundress' laying eggs on a patch will lay just enough sons to fertilize her daughters. As the number of 'foundresses' laying eggs on a patch increases (and LMC declines), females produce increasingly male-biased sex ratios. Phenotypic studies have revealed the cues females use to estimate the level of LMC their sons will experience, but our understanding of the genetics underlying sex allocation is limited. Here, we exposed females to three foundress number conditions, i.e. three LMC conditions, and allowed them to oviposit. mRNA was extracted from only the heads of these females to target the brain tissue. The subsequent RNA-seq experiment confirmed that differential gene expression is not associated with the response to sex allocation cues and that we must instead turn to the underlying neuroscience to reveal the underpinnings of this impressive behavioural plasticity.

De novo characterization of venom apparatus transcriptome of Pardosa pseudoannulata and analysis of its gene expression in response to Bt protein

Background

Pardosa pseudoannulata is a prevailing spider species, and has been regarded as an important bio-control agent of insect pests in farmland of China. However, the available genomic and transcriptomic databases of P. pseudoannulata and their venom are limited, which severely hampers functional genomic analysis of P. pseudoannulata. Recently high-throughput sequencing technology has been proved to be an efficient tool for profiling the transcriptome of relevant non-target organisms exposed to Bacillus thuringiensis (Bt) protein through food webs.

Results

In this study, the transcriptome of the venom apparatus was analyzed. A total of 113,358 non-redundant unigenes were yielded, among which 34,041 unigenes with complete or various length encoding regions were assigned biological function annotations and annotated with gene ontology and karyotic orthologous group terms. In addition, 3726 unigenes involved in response to stimulus and 720 unigenes associated with immune-response pathways were identified. Furthermore, we investigated transcriptomic changes in the venom apparatus using tag-based DGE technique. A total of 1724 differentially expressed genes (DEGs) were detected, while 75 and 372 DEGs were functionally annotated with KEGG pathways and GO terms, respectively. qPCR analyses were performed to verify the DEGs directly or indirectly related to immune and stress responses, including genes encoding heat shock protein, toll-like receptor, GST and NADH dehydrogenase.

Conclusion

This is the first study conducted to specifically investigate the venom apparatus of P. pseudoannulata in response to Bt protein exposure through tritrophic chain. A substantial fraction of transcript sequences was generated by high-throughput sequencing of the venom apparatus of P. pseudoannulata. Then a comparative transcriptome analysis showing a large number of candidate genes involved in immune response were identified by the tag-based DGE technology. This transcriptome dataset will provide a comprehensive sequence resource for furture molecular genetic research of the venom apparatus of P. pseudoannulata.

Electronic supplementary material

The online version of this article (10.1186/s12896-017-0392-z) contains supplementary material, which is available to authorized users.

Induction of stress- and immune-associated genes in the Indian meal moth Plodia interpunctella against envenomation by the ectoparasitoid Bracon hebetor

Envenomation is an important process in parasitism by parasitic wasps; it suppresses the immune and development of host insects. However, the molecular mechanisms of host responses to envenomation are not yet clear. This study aimed to determine the transcription-level responses of the Indian meal moth Plodia interpunctella against envenomation of the ectoparasitoid Bracon hebetor. Quantitative real-time reverse-transcription PCR was used to determine the transcriptional changes of 13 selected genes, which are associated with development, metabolism, stress, or immunity, in the feeding and wandering fifth instar larvae over a 4-day period after envenomation. The effects of envenomation on the feeding-stage larvae were compared with those of starvation in the transcriptional levels of the 13 genes. Most selected genes were altered in their expression by either envenomation or starvation. In particular, a heat shock protein, hsp70, was highly upregulated in envenomated larvae in both the feeding and wandering stages as well as in starved larvae. Further, some genes were upregulated by envenomation in a stage-specific manner. For example, hsp25 was upregulated after envenomation in the feeding larvae, but hsp90 and an immune-associated gene, hemolin, were upregulated in the wandering larvae. However, both envenomation and starvation resulted in the downregulation of genes associated with development and metabolism. Taken together, P. interpunctella upregulated stress- and immune-responsive genes, but downregulated genes associated with development and metabolism after envenomation. This study provides important information for understanding the molecular mechanisms of host responses to parasitism.

Identification of Venom Proteins of the Indigenous Endoparasitoid Chouioia cunea (Hymenoptera: Eulophidae)

Chouioia cunea (Yang) (Hymenoptera: Eulophidae) is an indigenous pupal endoparasitoid that effectively attacks the exotic fall webworm Hyphantria cunea (Drury) (Lepidoptera: Arctiidae) in China. In this novel association, the parasitoid's venom has played an important role in subduing the immune defense of the host although little is known about the composition and functions of the parasitoid's venom. We therefore first identified the parasitoid's major venom proteins using electrospray ionization-mass spectrometry (ESI-MS). Approximately 207 different proteins were identified from C. cunea's venom; among them 26 types widely existed in other endoparasitoids' venom, including calreticulin and arginine kinase, which inhibited the host immune system.