Recombinant baculoviruses for insect control

Agricultural Pest Management: The Role of Microorganisms in Biopesticides and Soil Bioremediation

Pesticide use in crops is a severe problem in some countries. Each country has its legislation for use, but they differ in the degree of tolerance for these broadly toxic products. Several synthetic pesticides can cause air, soil, and water pollution, contaminating the human food chain and other living beings. In addition, some of them can accumulate in the environment for an indeterminate amount of time. The agriculture sector must guarantee healthy food with sustainable production using environmentally friendly methods. In this context, biological biopesticides from microbes and plants are a growing green solution for this segment. Several pests attack crops worldwide, including weeds, insects, nematodes, and microorganisms such as fungi, bacteria, and viruses, causing diseases and economic losses. The use of bioproducts from microorganisms, such as microbial biopesticides (MBPs) or microorganisms alone, is a practice and is growing due to the intense research in the world. Mainly, bacteria, fungi, and baculoviruses have been used as sources of biomolecules and secondary metabolites for biopesticide use. Different methods, such as direct soil application, spraying techniques with microorganisms, endotherapy, and seed treatment, are used. Adjuvants like surfactants, protective agents, and carriers improve the system in different formulations. In addition, microorganisms are a tool for the bioremediation of pesticides in the environment. This review summarizes these topics, focusing on the biopesticides of microbial origin.

Morphological, Biological, and Molecular Characterization of Type I Granuloviruses of Spodoptera frugiperda

Granuloviruses (GVs) Betabaculovirus associated with the fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), especially those of the type I, have scarcely been studied. These GVs might be an effective alternative for the biocontrol of this insect. In this study, the native GVs SfGV-CH13 and SfGV-CH28 were isolated from FAW larvae and characterized for morphology, molecular traits, and insecticidal activity. The elapsed time between symptomatic infection of larvae and stop feeding as well as the weight of larvae before death or prior to pupation were also evaluated. Both GVs had ovoid shape and a length of 0.4 µm. They had the same DNA restriction profiles and their genome sizes were about 126 kb. The symptomatic infection with the tested GVs mainly caused flaccidity of larva body and discoloration of integument. The integument lysis was only observed in 8% of infected larvae. Infected larvae gradually stopped feeding. Overall, these symptoms are characteristic of infections caused by type I GVs, which are known as monoorganotropic or slow-killing GVs. The median lethal dose (LD50) values for SfGV-CH13 and SfGV-CH28 isolates were 5.4 × 102 and 1.1 × 103 OBs/larva, respectively. The median lethal time (LT50) ranged from 17 to 24 days. LT50 values decreased as the viral dose was increased. The elapsed time from symptomatic infection until pupation and body weight of larvae (third instar) were higher with SfGV-CH28 than SfGV-CH13. Both granulovirus isolates were able to kill the FAW larvae from the 12th day.

Biopesticides: a Green Approach Towards Agricultural Pests

Biopesticides are biological products or organisms which are potential candidates for eco-friendly pest management and crop protection over the chemical pesticides. The so-called biopesticides include viruses, bacteria, fungi, predators, parasites, and pheromones exhibiting a variety of modes of actions. They are less toxic, rapidly degradable, and more targeted to specific pests. However, it is noted that the formulation of biopesticides plays a crucial link between production and application, and the former dictates economy, longer shelf life, ease of application, and enhanced field efficacy. Moreover, there is an urgent need for organic farmers to gain more proficiency in using biopesticides. Even though biopesticides have more advantages, the main challenge is the marketing of biopesticides. Advances in biopesticide research and development significantly reduce the environmental damage caused by the residues of synthetic insecticides and support sustainable agriculture. Numerous products have been developed since the introduction of biopesticides, some of which have taken the lead in the agro-market after being registered and released. The types of biopesticides; their mode of action; formulation strategies; recent advancements of biopesticides focusing mainly on improvement of its action spectra, to thereby replace chemical pesticides; and finally, the future aspects of biopesticides have been discussed in this review.

Drosophila X virus-like particles as delivery carriers for improved oral insecticidal efficacy of scorpion Androctonus australis peptide against the invasive fruit fly, Drosophila suzukii

Insect-specific neurotoxic peptides derived from the venoms of scorpions and spiders can cause acute paralysis and death when injected into insects, offering a promising insecticidal component for insect pest control. However, effective delivery systems are required to help neurotoxic peptides pass through the gut barrier into the hemolymph, where they can act. Here, we investigated the potential of a novel nanocarrier, Drosophila X virus-like particle (DXV-VLP), for delivering a neurotoxin from the scorpion Androctonus australis Hector (AaIT) against the invasive pest fruit fly, Drosophila suzukii. Our results show that the fusion proteins of DXV polyproteins with AaIT peptide at their C-termini could be sufficiently produced in Lepidoptera Hi5 cells in a soluble form using the recombinant baculovirus expression system, and could self-assemble into VLPs with similar particle morphology and size to authentic DXV virions. In addition, the AaIT peptides displayed on DXV-VLPs retained their toxicity, as demonstrated in injection bioassays that resulted in severe mortality (72%) in adults after 72 h. When fed to adults, mild mortality was observed in the group treated with DXV-AaIT (38%), while no mortality occurred in the group treated with AaIT peptide, thus indicating the significant role of DXV-VLPs in delivering AaIT peptides. Overall, this proof-of-concept study demonstrates for the first time that VLPs can be exploited to enhance oral delivery of insect-specific neurotoxic peptides in the context of pest control. Moreover, it provides insights for further improvements and potentially the development of neurotoxin-based bioinsecticides and/or transgenic crops for insect pest control.

Leveraging insect viruses and genetic manipulation for sustainable agricultural pest control

The potential of insect viruses in the biological control of agricultural pests is well-recognized, yet their practical application faces obstacles such as host specificity, variable virulence, and resource scarcity. High-throughput sequencing (HTS) technologies have significantly advanced our capabilities in discovering and identifying new insect viruses, thereby enriching the arsenal for pest management. Concurrently, progress in reverse genetics has facilitated the development of versatile viral expression vectors. These vectors have enhanced the specificity and effectiveness of insect viruses in targeting specific pests, offering a more precise approach to pest control. This review provides a comprehensive examination of the methodologies employed in the identification of insect viruses using HTS. Additionally, it explores the domain of genetically modified insect viruses and their associated challenges in pest management. The adoption of these cutting-edge approaches holds great promise for developing environmentally sustainable and effective pest control solutions. © 2023 Society of Chemical Industry.

Effects of wasp (Vespa crabro) nest extracts on virus replication of Autographa californica nuclear polyhedrosis virus on Spodoptera frugiperda cell culture

The antiviral properties of the extracts of Vespa crabro nests collected from the Black Sea, Turkey have been investigated on Spodoptera frugiperda (Sf) cell cultures of Autographa californica multicapsid nuclear polyhedrosis virus (AcMNPV). The effect of nests on cell viability and cytotoxicity analysis and the antiviral assay was studied, and the cytopathic effects of the virus were detected. The nest's viral content was identified. The impact of nest extracts on the protein synthesis of the virus was investigated. Also interaction with pUC18 plasmid DNA was investigated, to analyse the protective effects of the Vespa crabro nest extract againist to hydroxyl radical-mediated DNA damage. 50 µg/ml concentration of ethanol, acetone, and petroleum ether extracts of the nests reduced the cytopathic effects of baculovirus on Sf cells. The extracts delayed infection above 25 µg/ml concentration. When the effects of nest extracts on virus titer were evaluated; the 50 µg/ml concentration of the acetone extract of the nest showed the highest effect (75%) reducing the virus titer. 25 µg/ml concentration of the ethanol extract of the nest showed the lowest effect (33.33%) with a reduction. The presence of polyhedrin protein was observed at 25 µg/ml concentrations of acetone and petroleum ether extracts. When the potential of the nest extracts to repair DNA damage, the nest extracts were found to have a concentration-dependent repair feature in different applications. As a result of bioactive component analysis, (Z) 9-Tricosane and (cis)-2-nonadecene (1.65%) were found to have the highest % areas. In other respects, 1H-Purine-6-amine, 2-dodecanol and hexadecanoic acid compaunds were Additionally, 1H-Purine-6-amine, 2-dodecanol and hexadecanoic acid compounds, which are associated with antiviral activity, also determined in the biocomponent analysis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-023-00603-0.

Enhancing the insecticidal potential of a baculovirus by overexpressing the mammalian β-galactosyl binding protein galectin-1

BACKGROUND

Bio-pesticide development is an important area of research in agriculture, in which viruses are an essential tool. Infection by entomological pathogenic viruses kills agricultural pests, and viral progenies are disseminated to infect more pests, eventually achieving long-term pest control in the field. Of the current virus-based pest control models, Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is the most studied. AcMNPV belongs to the Baculoviridae family and can infect many lepidopterans. Although AcMNPV has been previously demonstrated to be a potential pest-control tool, its long virus infection cycle has made field applications challenging. To overcome this, we generated a recombinant baculovirus that can express mammalian galectin-1, which is a galactoside-binding protein that binds to the peritrophic matrix in the midgut of lepidopteran pests and induces perforation of the membrane.

RESULTS

Hosts infected with a recombinant virus that expressed mammalian galectin-1 exhibited reduced appetite and died sooner in both laboratory and small-scale field studies, suggesting that the overexpression of galectin-1 can more efficiently eliminate pest hosts. In addition to disrupting the integrity of the peritrophic matrix, the immune system of hosts infected with recombinant baculovirus carrying the galectin-1 gene was suppressed, making hosts more vulnerable to secondary infection.

CONCLUSION

Galectin-1 has been shown to affect immune responses in mammals, including humans, but to our knowledge, the effect of galectin-1 on insect immune systems had not been previously reported. Our results demonstrated that the pest-control potential of baculoviruses can be improved by using a recombinant baculovirus that overexpresses mammalian galectin-1 in hosts. © 2022 Society of Chemical Industry.

High temperature exposure reduces the susceptibility of Helicoverpa armigera to its nucleopolyhedrovirus (HearNPV) by enhancing expression of heat shock proteins

BACKGROUND

High temperatures will occur more frequently with global warming, with potential impacts on the efficacy of biological control agents. Heat shock proteins (HSPs) are induced by high temperature, but their possible roles in pest resistance to entomopathogens remain unexplored. We investigated the effects of high temperature (35 °C) on Helicoverpa armigera resistance to H. armigera nucleopolyhedrovirus (HearNPV) and the putative roles of HSPs in this process.

RESULTS

Even short periods (24 h) of high temperature (35 °C) reduced mortality in HearNPV-infected H. armigera larvae. Sustained 35 °C exposure significantly shortened developmental time, and increased fresh weight and locomotor activity in infected larvae. Moreover, high temperature inhibited virus replication and thickened the epidermis of H. armigera, resulting in reduced spread of infection from cadavers. Real-time polymerase chain reaction (PCR) analysis showed that expression of 11 HSP genes was altered by the 35 °C treatment, and that mostly small heat shock protein (sHSP) genes were up-regulated, the same sHSPs were induced when larvae were infected with HearNPV. Finally, RNA interference (RNAi) suppression of these sHSPs showed that only Hsp24.91 and Hsp21.8 diminished H. armigera defensive responses to HearNPV infection.

CONCLUSION

Even short periods of exposure to high temperature can significantly reduce susceptibility of H. armigera larvae to HearNPV by stimulating the production of sHSPs which enhance immune responses, with important implications for the use of entomopathogens as biological control agents under global warming scenarios. © 2022 Society of Chemical Industry.

Surface modification of nucleopolyhedrovirus with polydopamine to improve its properties

BACKGROUND

Baculoviruses have been developed as promising biopesticides to control pests due to their high host specificity and virulence, and nontoxicity to humans and nontarget animals. However, their sensitivity to ultraviolet (UV) radiation and instability in the natural environment are major constraints to its large-scale application. In this study, polydopamine-nucleopolyhedrovirus microcapsules were established to improve the instability of baculoviruses in sunlight.

RESULTS

The optimal conditions for the preparation of polydopamine-nucleopolyhedrovirus microcapsules were as follows:  Spodoptera exigua nucleopolyhedrovirus (SeMNPV)concentration of 2 × 10⁸  polyhedral inclusion body（PIB） mL^-1 , reaction time of 6 h, and pH of 9.0. The particle size of the obtained microcapsules was about 1 μm. The microencapsulated baculovirus improved its thermal stability and wettability, and enhanced its insecticidal activity against Spodoptera exigua. Moreover, under the same UV treatment, the insecticidal effect against S. exigua larvae of microencapsulated baculovirus was only reduced by 8.89%, whereas that of the nonmicroencapsulated baculovirus was reduced by 27.27%.

CONCLUSION

Polydopamine-nucleopolyhedrovirus microcapsules provided better UV resistance and preparation stability compared with unmodified SeMNPV, and demonstrate an idea for the development of a baculovirus-based stabilized product. © 2021 Society of Chemical Industry.

Nucleopolyhedrovirus Coocclusion Technology: A New Concept in the Development of Biological Insecticides

Nucleopolyhedroviruses (NPV, Baculoviridae) that infect lepidopteran pests have an established record as safe and effective biological insecticides. Here, we describe a new approach for the development of NPV-based insecticides. This technology takes advantage of the unique way in which these viruses are transmitted as collective infectious units, and the genotypic diversity present in natural virus populations. A ten-step procedure is described involving genotypic variant selection, mixing, coinfection and intraspecific coocclusion of variants within viral occlusion bodies. Using two examples, we demonstrate how this approach can be used to produce highly pathogenic virus preparations for pest control. As restricted host range limits the uptake of NPV-based insecticides, this technology has recently been adapted to produce custom-designed interspecific mixtures of viruses that can be applied to control complexes of lepidopteran pests on particular crops, as long as a shared host species is available for virus production. This approach to the development of NPV-based insecticides has the potential to be applied across a broad range of NPV-pest pathosystems.

Survival of the Sawfly Athalia rosae Upon Infection by an Entomopathogenic Fungus and in Relation to Clerodanoid Uptake

Larvae of the turnip sawfly Athalia rosae are a pest of Brassicacae plants, as their feeding can cause defoliation of various crops of economic importance. The larvae and the adults of this sawfly species are known to take up different classes of chemical compounds from their respective host plants, with potentially deterrent functions against predators. In addition, compounds taken up by the adults, the clerodanoids, are known for their antimicrobial activity. These features could be a challenge to biocontrol strategies. Several natural enemies of A. rosae have been identified, targeting larval and pupal stages of A. rosae, which could potentially be used as biocontrol agents. However, targeting the adult stage of a larval pest in addition to targeting the juvenile stages may improve population control. In this study, we ask whether a strain of the entomopathogenic fungus Beauveria bassiana shows biological activity against A. rosae adults. We also investigate whether the behavior of clerodanoid uptake by the adults, which is commonly found, affects their survival in response to a B. bassiana exposure. We found a clear dose-response relationship, i.e., with increasing fungal conidia concentrations survival of A. rosae decreased. However, there was only a low incidence of mycelial growth and sporulation from A. rosae cadavers, indicating that either the fungus is not successfully developing inside this host, or it is not able to re-emerge from it. Clerodanoid uptake decreased the survival of healthy adults; however, it did not increase their survival to B. bassiana. Our results revealed that this strain of B. bassiana if applied alone is probably not suitable for biocontrol of this sawfly species, because A. rosae showed a high baseline resistance against this fungus. The behavior of clerodanoid uptake is unlikely to have evolved as a defense against this entomopathogenic fungus.

Displaying enhancing factors on the surface of occlusion bodies improves the insecticidal efficacy of a baculovirus

BACKGROUND

Baculoviruses provide long-lasting control of crop pests and are harmless to humans and non-target animals, making them attractive bioinsecticides. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) has a wide-host range and is one such commercial bioinsecticide, but its low infectivity to older larvae and less-sensitive species precludes its large-scale application. We sought to improve the infectivity of AcMNPV.

RESULTS

Two enhancing factors, the truncated enhancin from Agrotis segetum granulovirus and GP37 from Cydia pomonella granulovirus, were expressed in fusion with the N-terminal and middle domain of the polyhedrin envelope protein of AcMNPV. Western blotting and immunoelectron microscopy analysis indicated that the enhancing factors were expressed on the occlusion bodies of the resulting AcMNPV variants. Bioassays showed that the median lethal doses of the recombinant viruses were 3.9-fold to 7.4-fold lower than those of the wild-type virus against the second and fourth instar of Spodoptera exigua larvae. The yields of occlusion bodies from the two recombinants in S. exigua larvae were comparable with those of the wild-type virus both in vitro and in vivo. Further bioassays showed that the AcMNPV variants fusing the enhancing factors were incapable of infecting the second instar larvae of S. litura, Helicoverpa armigera, and Pyrausta nubilalis, which were not sensitive to the wild-type AcMNPV.

CONCLUSION

These genetically modified AcMNPV variants exhibited an enhanced infectivity and may offer better baculovirus control of crop pests. © 2019 Society of Chemical Industry.

An insight into the sialome, mialome and virome of the horn fly, Haematobia irritans

BACKGROUND

The horn fly (Haematobia irritans) is an obligate blood feeder that causes considerable economic losses in livestock industries worldwide. The control of this cattle pest is mainly based on insecticides; unfortunately, in many regions, horn flies have developed resistance. Vaccines or biological control have been proposed as alternative control methods, but the available information about the biology or physiology of this parasite is rather scarce.

RESULTS

We present a comprehensive description of the salivary and midgut transcriptomes of the horn fly (Haematobia irritans), using deep sequencing achieved by the Illumina protocol, as well as exploring the virome of this fly. Comparison of the two transcriptomes allow for identification of uniquely salivary or uniquely midgut transcripts, as identified by statistically differential transcript expression at a level of 16 x or more. In addition, we provide genomic highlights and phylogenetic insights of Haematobia irritans Nora virus and present evidence of a novel densovirus, both associated to midgut libraries of H. irritans.

CONCLUSIONS

We provide a catalog of protein sequences associated with the salivary glands and midgut of the horn fly that will be useful for vaccine design. Additionally, we discover two midgut-associated viruses that infect these flies in nature. Future studies should address the prevalence, biological effects and life cycles of these viruses, which could eventually lead to translational work oriented to the control of this economically important cattle pest.

Identification of Multiple Replication Stages and Origins in the Nucleopolyhedrovirus of Anticarsia gemmatalis

To understand the mechanism of replication used by baculoviruses, it is essential to describe all the factors involved, including virus and host proteins and the sequences where DNA synthesis starts. A lot of work on this topic has been done, but there is still confusion in defining what sequence/s act in such functions, and the mechanism of replication is not very well understood. In this work, we performed an AgMNPV replication kinetics into the susceptible UFL-Ag-286 cells to estimate viral genome synthesis rates. We found that the viral DNA exponentially increases in two different phases that are temporally separated by an interval of 5 h, probably suggesting the occurrence of two different mechanisms of replication. Then, we prepared a plasmid library containing virus fragments (0.5-2 kbp), which were transfected and infected with AgMNPV in UFL-Ag-286 cells. We identified 12 virus fragments which acted as origins of replication (ORI). Those fragments are in close proximity to core genes. This association to the core genome would ensure vertical transmission of ORIs. We also predict the presence of common structures on those fragments that probably recruit the replication machinery, a structure also present in previously reported ORIs in baculoviruses.

Pore-Forming Proteins from Cnidarians and Arachnids as Potential Biotechnological Tools

Animal venoms are complex mixtures of highly specialized toxic molecules. Cnidarians and arachnids produce pore-forming proteins (PFPs) directed against the plasma membrane of their target cells. Among PFPs from cnidarians, actinoporins stand out for their small size and molecular simplicity. While native actinoporins require only sphingomyelin for membrane binding, engineered chimeras containing a recognition antibody-derived domain fused to an actinoporin isoform can nonetheless serve as highly specific immunotoxins. Examples of such constructs targeted against malignant cells have been already reported. However, PFPs from arachnid venoms are less well-studied from a structural and functional point of view. Spiders from the Latrodectus genus are professional insect hunters that, as part of their toxic arsenal, produce large PFPs known as latrotoxins. Interestingly, some latrotoxins have been identified as potent and highly-specific insecticides. Given the proteinaceous nature of these toxins, their promising future use as efficient bioinsecticides is discussed throughout this Perspective. Protein engineering and large-scale recombinant production are critical steps for the use of these PFPs as tools to control agriculturally important insect pests. In summary, both families of PFPs, from Cnidaria and Arachnida, appear to be molecules with promising biotechnological applications.

Baculoviral infection reduces the expression of four allergen proteins of silkworm pupa

Silkworm (Bombyx mori) larvae are widely used to express exogenous proteins. Moreover, some silkworm pupal proteins can be used as drug-loading materials for selfexpressed oral tolerance drugs. However, several proteins expressed in silkworm pupae cause severe allergic reactions in humans and animals. Interestingly, some baculovirus vectors have been shown to alter the host gene and its expression in insect cells, but this has not been confirmed in silkworm. Here, we analyzed the effects of infection with an empty B. mori baculovirus (BmNPV) vector on silkworm pupal protein expression. Using a proteomics approach, the allergens thiol peroxiredoxin (Jafrac1), 27-kDa glycoprotein (p27k), arginine kinase, and paramyosin as well as 32 additional differentially expressed proteins were identified. Downregulation of the messenger RNA expression of the four known allergens was observed after BmNPV infection; subsequent changes in protein expression were confirmed by the western blot analysis using polyclonal antibodies prepared with recombinant proteins of the four allergens. Collectively, these data indicate that the four known allergens of silkworm pupae can be reduced by infection ith an empty BmNPV vector to increase the safety of silkworm pupa-based exogenous protein expression and drug delivery of oral pharmaceuticals. In addition, the four recombinant allergen proteins may contribute to the diagnosis of allergic diseases of silkworm pupa.

The Journey of in vivo Virus Engineered Dendritic Cells From Bench to Bedside: A Bumpy Road

Dendritic cells (DCs) are recognized as highly potent antigen-presenting cells that are able to stimulate cytotoxic T lymphocyte (CTL) responses with antitumor activity. Consequently, DCs have been explored as cellular vaccines in cancer immunotherapy. To that end, DCs are modified with tumor antigens to enable presentation of antigen-derived peptides to CTLs. In this review we discuss the use of viral vectors for in situ modification of DCs, focusing on their clinical applications as anticancer vaccines. Among the viral vectors discussed are those derived from viruses belonging to the families of the Poxviridae, Adenoviridae, Retroviridae, Togaviridae, Paramyxoviridae, and Rhabdoviridae. We will further shed light on how the combination of viral vector-based vaccination with T-cell supporting strategies will bring this strategy to the next level.

Improving Baculovirus Infectivity by Efficiently Embedding Enhancing Factors into Occlusion Bodies

The relatively low infectivity of baculoviruses to their host larvae limits their use as insecticidal agents on a larger scale. In the present study, a novel strategy was developed to efficiently embed foreign proteins into Autographa californica multiple nucleopolyhedrovirus (AcMNPV) occlusion bodies (OBs) to achieve stable expression of foreign proteins and to improve viral infectivity. A recombinant AcMNPV bacmid was constructed by expressing the 150-amino-acid (aa) N-terminal segment of polyhedrin under the control of the p10 promoter and the remaining C-terminal 95-aa segment under the control of the polyhedrin promoter. The recombinant virus formed OBs in Spodoptera frugiperda 9 cells, in which the occlusion-derived viruses were embedded in a manner similar to that for wild-type AcMNPV. Next, the 95-aa polyhedrin C terminus was fused to enhanced green fluorescent protein, and the recombinant AcMNPV formed fluorescent green OBs and was stably passaged in vitro and in vivo The AcMNPV recombinants were further modified by fusing truncated Agrotis segetum granulovirus enhancin or truncated Cydia pomonella granulovirus ORF13 (GP37) to the C-terminal 95 aa of polyhedrin, and both recombinants were able to form normal OBs. Bioactivity assays indicated that the median lethal concentrations of these two AcMNPV recombinants were 3- to 5-fold lower than that of the control virus. These results suggest that embedding enhancing factors in baculovirus OBs by use of this novel technique may promote efficient and stable foreign protein expression and significantly improve baculovirus infectivity.IMPORTANCE Baculoviruses have been used as bioinsecticides for over 40 years, but their relatively low infectivity to their host larvae limits their use on a larger scale. It has been reported that it is possible to improve baculovirus infectivity by packaging enhancing factors within baculovirus occlusion bodies (OBs); however, so far, the packaging efficiency has been low. In this article, we describe a novel strategy for efficiently embedding foreign proteins into AcMNPV OBs by expressing N- and C-terminal (dimidiate) polyhedrin fragments (150 and 95 amino acids, respectively) as fusions to foreign proteins under the control of the p10 and polyhedrin promoters, respectively. When this strategy was used to embed an enhancing factor (enhancin or GP37) into the baculovirus OBs, 3- to 5-fold increases in baculoviral infectivity were observed. This novel strategy has the potential to create an efficient protein expression system and a highly efficient virus-based system for insecticide production in the future.

Fungal Ribotoxins: A Review of Potential Biotechnological Applications

Fungi establish a complex network of biological interactions with other organisms in nature. In many cases, these involve the production of toxins for survival or colonization purposes. Among these toxins, ribotoxins stand out as promising candidates for their use in biotechnological applications. They constitute a group of highly specific extracellular ribonucleases that target a universally conserved sequence of RNA in the ribosome, the sarcin-ricin loop. The detailed molecular study of this family of toxic proteins over the past decades has highlighted their potential in applied research. Remarkable examples would be the recent studies in the field of cancer research with promising results involving ribotoxin-based immunotoxins. On the other hand, some ribotoxin-producer fungi have already been studied in the control of insect pests. The recent role of ribotoxins as insecticides could allow their employment in formulas and even as baculovirus-based biopesticides. Moreover, considering the important role of their target in the ribosome, they can be used as tools to study how ribosome biogenesis is regulated and, eventually, may contribute to a better understanding of some ribosomopathies.

Determinant Factors in the Production of a Co-Occluded Binary Mixture of Helicoverpa armigera Alphabaculovirus (HearNPV) Genotypes with Desirable Insecticidal Characteristics

A co-occluded binary mixture of Helicoverpa armigera nucleopolyhedrovirus genotypes HearSP1B and HearLB6 at a 1:1 ratio (HearSP1B+HearLB6) was selected for the development of a virus-based biological insecticide, which requires an efficient large-scale production system. In vivo production systems require optimization studies in each host-virus pathosystem. In the present study, the effects of larval instar, rearing density, timing of inoculation, inoculum concentration and temperature on the production of HearSP1B+HearLB6 in its homologous host were evaluated. The high prevalence of cannibalism in infected larvae (40-87%) indicated that insects require individual rearing to avoid major losses in OB production. The OB production of recently molted fifth instars (7.0 x 109 OBs/larva), combined with a high prevalence of mortality (85.7%), resulted in the highest overall OB yield (6.0 x 1011 OBs/100 inoculated larvae), compared to those of third or fourth instars. However, as inoculum concentration did not influence final OB yield, the lowest concentration, LC80 (5.5 x 106 OBs/ml), was selected. Incubation temperature did not significantly influence OB yield, although larvae maintained at 30°C died 13 and 34 hours earlier than those incubated at 26°C and 23°C, respectively. We conclude that the efficient production of HearSP1B+HearLB6 OBs involves inoculation of recently molted fifth instars with a LC80 concentration of OBs followed by individual rearing at 30°C.

The Host Specificities of Baculovirus per os Infectivity Factors

Baculoviruses are insect-specific pathogens with a generally narrow host ranges. Successful primary infection is initiated by the proper interaction of at least 8 conserved per os infectivity factors (PIFs) with the host's midgut cells, a process that remains largely a mystery. In this study, we investigated the host specificities of the four core components of the PIF complex, P74, PIF1, PIF2 and PIF3 by using Helicoverpa armigera nucleopolyhedrovirus (HearNPV) backbone. The four pifs of HearNPV were replaced by their counterparts from a group I Autographa californica multiple nucleopolyhedrovirus (AcMNPV) or a group II Spodoptera litura nucleopolyhedrovirus (SpltNPV). Transfection and infection assays showed that all the recombinant viruses were able to produce infectious budded viruses (BVs) and were lethal to H. armigera larvae via intrahaemocoelic injection. However, feeding experiments using very high concentration of occlusion bodies demonstrated that all the recombinant viruses completely lost oral infectivity except SpltNPV pif3 substituted pif3-null HearNPV (vHaBacΔpif3-Sppif3-ph). Furthermore, bioassay result showed that the median lethal concentration (LC50) value of vHaBacΔpif3-Sppif3-ph was 23-fold higher than that of the control virus vHaBacΔpif3-Hapif3-ph, indicating that SpltNPV pif3 can only partially substitute the function of HearNPV pif3. These results suggested that most of PIFs tested have strict host specificities, which may account, at least in part, for the limited host ranges of baculoviruses.

Comparative proteomics analysis of Spodoptera frugiperda cells during Autographa californica multiple nucleopolyhedrovirus infection

Background

Increasing evidence sugggest that in addition of balculovirus controling insect host, host cells also responds to balculovirus infection. However, compared to existing knowledge on virus gene, host cell responses are relatively poorly understood.

Methods

In this study, Spodoptera frugiperda (Sf9) cells were infected with Autographa californica multiple nucleopolyhedrovirus (AcMNPV). The protein composition and protein changes of Spodoptera frugiperda (Sf9) cells of different infection stages were analysed by isobaric tag for relative and absolute quantification (iTRAQ) techniques.

Results

A total of 4004 Sf9 proteins were identified by iTRAQ and 413 proteins were found as more than 1.5-fold changes in abundance. The 413 proteins were categorised according to GO classification for insects and were categorised into: biological process, molecular function and cellular component.

Conclusions

The determination of the protein changes in infected Sf9 cells would help to better understanding of host cell responses and facilitate better design of this virus-host cell interaction in pest insect control and other related fields.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0346-9) contains supplementary material, which is available to authorized users.

Proteomic analysis of the occlusion-derived virus of Clostera anachoreta granulovirus

To date, proteomic studies have been performed on occlusion-derived viruses (ODVs) from five members of the family Baculoviridae, genus Alphabaculovirus, but only a single member of the genus Betabaculovirus (Pieris rapae granulovirus). In this study, LC-MS/MS was used to analyse the ODV proteins of Clostera anachoreta granulovirus (ClanGV), another member of the genus Betabaculovirus. The results indicated that 73 proteins, including the products of 27 baculovirus core genes, were present in ClanGV ODVs. This is the largest number of ODV proteins identified in baculoviruses to date. To the best of our knowledge, 24 of these proteins were newly identified as ODV-associated proteins. Twelve of the proteins were shared by all seven of the other baculoviruses that have been analysed by proteomic techniques, including P49, PIF-2, ODV-EC43, P74, P6.9, P33, VP39, ODV-EC27, VP91, GP41, VLF-1 and VP1054. ClanGV shared between 20 and 36 ODV proteins with each of the other six baculoviruses that have been analysed by proteomics. Ten proteins were identified only as ODV components of ClanGV and PrGV: Clan22, Clan27, Clan69, Clan83, Clan84, Clan90, Clan116, Clan94, FGF-3 and ME53, the first seven of which were encoded by betabaculovirus-specific genes. These findings may provide novel insights into baculovirus structure as well as reveal similarities and differences between alphabaculoviruses and betabaculoviruses.

Viral biocontrol: grand experiments in disease emergence and evolution

Although viral emergence is commonly associated with cross-species transmission, the processes and determinants of viral evolution in a novel host environment are poorly understood. We address key questions in virus emergence and evolution using data generated from two unique natural experiments: the deliberate release of myxoma virus (MYXV) and rabbit hemorrhagic disease virus (RHDV) as biological control (biocontrol) agents against the European rabbit in Australia, and which have been of enormous benefit to Australia's ecosystem and agricultural industries. Notably, although virulence evolution in MYXV and RHDV followed different trajectories, a strongly parallel evolutionary process was observed in Australia and Europe. These biocontrol agents were also characterized by a lack of transmission to nontarget host species, suggesting that there are major barriers to successful emergence.

Baculovirus nuclear import: open, nuclear pore complex (NPC) sesame

Baculoviruses are one of the largest viruses that replicate in the nucleus of their host cells. During infection, the rod-shape, 250-nm long nucleocapsid delivers its genome into the nucleus. Electron microscopy evidence suggests that baculoviruses, specifically the Alphabaculoviruses (nucleopolyhedroviruses) and the Betabaculoviruses (granuloviruses), have evolved two very distinct modes for doing this. Here we review historical and current experimental results of baculovirus nuclear import studies, with an emphasis on electron microscopy studies employing the prototypical baculovirus Autographa californica multiple nucleopolyhedrovirus infecting cultured cells. We also discuss the implications of recent studies towards theories of nuclear transport mechanisms.

Use of bacterial artificial chromosomes in baculovirus research and recombinant protein expression: current trends and future perspectives

The baculovirus expression system is one of the most successful and widely used eukaryotic protein expression methods. This short review will summarise the role of bacterial artificial chromosomes (BACS) as an enabling technology for the modification of the virus genome. For many years baculovirus genomes have been maintained in E. coli as bacterial artificial chromosomes, and foreign genes have been inserted using a transposition-based system. However, with recent advances in molecular biology techniques, particularly targeting reverse engineering of the baculovirus genome by recombineering, new frontiers in protein expression are being addressed. In particular, BACs have facilitated the propagation of disabled virus genomes that allow high throughput protein expression. Furthermore, improvement in the selection of recombinant viral genomes inserted into BACS has enabled the expression of multiprotein complexes by iterative recombineering of the baculovirus genome.

The ac53, ac78, ac101, and ac103 genes are newly discovered core genes in the family Baculoviridae

The family Baculoviridae is a large group of insect viruses containing circular double-stranded DNA genomes of 80 to 180 kbp, which have broad biotechnological applications. A key feature to understand and manipulate them is the recognition of orthology. However, the differences in gene contents and evolutionary distances among the known members of this family make it difficult to assign sequence orthology. In this study, the genome sequences of 58 baculoviruses were analyzed, with the aim to detect previously undescribed core genes because of their remote homology. A routine based on Multi PSI-Blast/tBlastN and Multi HaMStR allowed us to detect 31 of 33 accepted core genes and 4 orthologous sequences in the Baculoviridae which were not described previously. Our results show that the ac53, ac78, ac101 (p40), and ac103 (p48) genes have orthologs in all genomes and should be considered core genes. Accordingly, there are 37 orthologous genes in the family Baculoviridae.

Baculovirus: molecular insights on their diversity and conservation

The Baculoviridae is a large group of insect viruses containing circular double-stranded DNA genomes of 80 to 180 kbp. In this study, genome sequences from 57 baculoviruses were analyzed to reevaluate the number and identity of core genes and to understand the distribution of the remaining coding sequences. Thirty one core genes with orthologs in all genomes were identified along with other 895 genes differing in their degrees of representation among reported genomes. Many of these latter genes are common to well-defined lineages, whereas others are unique to one or a few of the viruses. Phylogenetic analyses based on core gene sequences and the gene composition of the genomes supported the current division of the Baculoviridae into 4 genera: Alphabaculovirus, Betabaculovirus, Gammabaculovirus, and Deltabaculovirus.

Competition between wild-type and a marked recombinant baculovirus (Spodoptera exigua nucleopolyhedrovirus) with enhanced speed of action in insect larvae

Competition between virus genotypes in insect hosts is a key element of virus fitness, affecting their long-term persistence in agro-ecosystems. Little information is available on virus competition in insect hosts or during serial passages from one cohort of hosts to the next. Here we report on the competition between two genotypes of Spodoptera exigua nucleopolyhedrovirus (SeMNPV), when serially passaged as mixtures in cohorts of 4th instar S. exigua larvae. One of the genotypes was a SeMNPV wild-type isolate, SeUS1, while the other was a SeMNPV recombinant (SeMNPV-XD1) having a greater speed of kill than SeUS1. SeXD1 lacks a suite of genes, including the ecdysteroid UDP-glucosyl transferase (egt) gene. SeXD1 expresses the green fluorescent protein (GFP) gene, enabling the identification of SeXD1 in cell culture and in insects. The relative proportion of SeUS1 and SeXD1 in successive passages of mixed infections in various ratios was determined by plaque assays of budded virus from infected larvae and by polymerase chain reactions and restriction enzyme analyses. The SeUS1 genotype outcompeted recombinant SeXD1 over successive passages. Depending on the initial virus genotype ratio, the recombinant SeXD1 was no longer detected after 6-12 passages. A mathematical model was developed to characterize the competition dynamics. Overall, the ratio SeUS1/XD1 increased by a factor 1.9 per passage. The findingssuggest that under the experimental conditions recombinant SeXD1 is displaced by the wild-type strain SeUS1, but further studies are needed to ascertain that this is also the case when the same baculoviruses would be used in agro-ecosystems.

Effects of fetal bovine serum deprivation in cell cultures on the production of Anticarsia gemmatalis multinucleopolyhedrovirus

BACKGROUND

Anticarsia gemmatalis is a pest in South America's soybean crops, which could be controlled by the Multinucleopolyhedrovirus of A. gemmatalis (AgMNPV). Currently, its commercial production is based on infected larvae. However, the possibility of using modified baculoviruses in Integrated Pest Management programs has stimulated an interest to develop alternative multiplication processes. This study evaluated the AgMNPV production in UFL-Ag-286 cells previously deprived Fetal Bovine Serum.

RESULTS

Culture media containing 1% FBS during the previous 48 hours achieved a synchronized condition where 90% of cells were found in G0/G1 stage, showing the presence of non-filamentous actin. All characteristics were estimated from cellular viability tests, cell actin detection trials and flow cytometer cell cycle analysis. AgMNPV production was tested by transcript studies and budded viruses (BVs) and occlusion bodies (OBs) yield quantitation. Results showed that the productivity in FBS deprived cells was 9.8 times more in BVs and 3.8 times more in OBs with respect to non-treated cells.

CONCLUSIONS

UFL-Ag-286 cells previously deprived in FBS shown to be a better host for AgMNPV propagation, increasing the useful for both in vitro bioinsecticide production and applications such as recombinant protein expression or gene delivery.

Transgenesis approaches for functional analysis of peptidergic cells in the silkworm Bombyx mori

The domestic silkworm, Bombyx mori represents an insect model of great scientific and economic importance. Besides the establishment of a stable germline transformation using the PiggyBac vector, technically feasible methods for in vivo gene delivery and transient gene expression were developed using viral based vectors, especially Sindbis viruses and baculoviruses. The recombinant baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV), commonly used for large-scale protein production in permissive cell lines or insects, has been used for foreign gene transfer into specific peptidergic cells of B. mori in vivo. Since targeted gene expression is essential for functional analysis of neuropeptide genes and their receptors, the baculovirus-mediated gene transfer can serve as a reliable approach in reverse genetic studies in the silkworm. We review various strategies employing the baculovirus vector system for transient expression of molecular markers and transcription factors in specific peptidergic cells to investigate their roles in B. mori. We also use this system for functional analysis of neuropeptide signaling in the ecdysis behavioral sequence. Our data indicate that the AcMNPV vector is suitable for efficient delivery of foreign genes and their expression directed into specific peptidergic neurons and endocrine cells of B. mori larvae and pupae. However, some modifications of the vector and steps for optimization are necessary to minimize negative effects of viral infection on the host development. The transient gene expression using the AcMNPV and other virus vectors are promising tools for analysis of molecular mechanisms underlying various neuroendocrine processes during development of B. mori.

Persistence of naturally occurring and genetically modified Choristoneura fumiferana nucleopolyhedroviruses in outdoor aquatic microcosms

BACKGROUND

To assess the persistence of genetically modified and naturally occurring baculoviruses in an aquatic environment, replicate (three) outdoor, aquatic microcosms were spiked with spruce budworm viruses [Ireland strain of Choristoneura fumiferana multiple nucleopolyhedrovirus (CfMNPV) and the recombinant CfMNPVegt(-)/lacZ(+)] at a rate of 1.86 x 10(10) occlusion bodies (OBs) m(-2) of surface area. The presence of virus in water samples collected at various times after inoculation was determined by PCR amplification of baculoviral DNA extracted from OBs.

RESULTS

Although UV radiation rapidly degrades baculoviruses under natural conditions, both viruses persisted above the level of detection (>100 OBs 450 microL(-1) of natural pond water) for at least 1 year post-inoculation, with little difference between the viruses in their patterns of persistence.

CONCLUSION

The present microcosm study suggests that occlusion bodies of baculoviruses can persist in the flocculent layer of natural ponds. On disturbance, OBs could re-enter the main water column and thus be available for transport to new locations. Implications for environmental risk assessment are discussed.

Peptides of arachnid venoms with insecticidal activity targeting sodium channels

Arachnids have a venom apparatus and secrete a complex chemical mixture of low molecular mass organic molecules, enzymes and polypeptide neurotoxins designed to paralyze or kill their prey. Most of these toxins are specific for membrane voltage-gated sodium channels, although some may also target calcium or potassium channels and other membrane receptors. Scorpions and spiders have provided the greatest number of the neurotoxins studied so far, for which, a good number of primary and 3D structures have been obtained. Structural features, comprising a folding that determines a similar spatial distribution of charged and hydrophobic side chains of specific amino acids, are strikingly common among the toxins from spider and scorpion venoms. Such similarities are, in turn, the key feature to target and bind these proteins to ionic channels. The search for new insecticidal compounds, as well as the study of their modes of action, constitutes a current approach to rationally design novel insecticides. This goal tends to be more relevant if the resistance to the conventional chemical products is considered. A promising alternative seems to be the biotechnological approach using toxin-expressing recombinant baculovirus. Spider and scorpion toxins having insecticidal activity are reviewed here considering their structures, toxicities and action mechanisms in sodium channels of excitable membranes.

Characterization of peptide components in the venom of the scorpion Liocheles australasiae (Hemiscorpiidae)

Scorpion venoms are composed of a number of neurotoxic peptides. A variety of toxins have been isolated from the venoms of scorpions of the family Buthidae, however, little interest has been paid to non-Buthidae scorpions. In this study, we examined the toxicity of the venom of Liocheles australasiae (Hemiscorpiidae) to mice and crickets, and characterized the peptide components by HPLC and mass spectrometry. Over 200 components were detected in the L. australasiae venom by LC/MS analysis, with components of molecular masses ranging from 500 to 5000 Da being particularly abundant. A number of peptides contained two to four disulfide bridges, which was estimated based on the mass difference after derivatization of Cys residues. A peptide having a monoisotopic molecular mass of 7781.6 Da and four disulfide bridges was isolated from the venom. The peptide has a primary structure similar in terms of the position of eight Cys residues to those observed in several peptides found from scorpions, ticks and insects, although biological roles of these peptides are unknown.

Sea anemone venom as a source of insecticidal peptides acting on voltage-gated Na+ channels

Sea anemones produce a myriad of toxic peptides and proteins of which a large group acts on voltage-gated Na+ channels. However, in comparison to other organisms, their venoms and toxins are poorly studied. Most of the known voltage-gated Na+ channel toxins isolated from sea anemone venoms act on neurotoxin receptor site 3 and inhibit the inactivation of these channels. Furthermore, it seems that most of these toxins have a distinct preference for crustaceans. Given the close evolutionary relationship between crustaceans and insects, it is not surprising that sea anemone toxins also profoundly affect insect voltage-gated Na+ channels, which constitutes the scope of this review. For this reason, these peptides can be considered as insecticidal lead compounds in the development of insecticides.

Modulation of insect Cav channels by peptidic spider toxins

Insects have a much smaller repertoire of voltage-gated calcium (Ca(V)) channels than vertebrates. Drosophila melanogaster harbors only a single ortholog of each of the vertebrate Ca(V)1, Ca(V)2, and Ca(V)3 subtypes, although its basal inventory is expanded by alternative splicing and editing of Ca(V) channel transcripts. Nevertheless, there appears to be little functional plasticity within this limited panel of insect Ca(V) channels, since severe loss-of-function mutations in genes encoding the pore-forming alpha1 subunits in Drosophila are embryonic lethal. Since the primary role of spider venom is to paralyze or kill insect prey, it is not surprising that most, if not all, spider venoms contain peptides that potently modify the activity of these functionally critical insect Ca(V) channels. Unfortunately, it has proven difficult to determine the precise ion channel subtypes recognized by these peptide toxins since insect Ca(V) channels have significantly different pharmacology to their vertebrate counterparts, and cloned insect Ca(V) channels are not available for electrophysiological studies. However, biochemical and genetic studies indicate that some of these spider toxins might ultimately become the defining pharmacology for certain subtypes of insect Ca(V) channels. This review focuses on peptidic spider toxins that specifically target insect Ca(V) channels. In addition to providing novel molecular tools for ion channel characterization, some of these toxins are being used as leads to develop new methods for controlling insect pests.

Delivery methods for peptide and protein toxins in insect control

Since the introduction of DDT in the 1940s, arthropod pest control has relied heavily upon chemical insecticides. However, the development of insect resistance, an increased awareness of the real and perceived environmental and health impacts of these chemicals, and the need for systems with a smaller environmental footprint has stimulated the search for new insecticidal compounds, novel molecular targets, and alternative control methods. In recent decades a variety of biocontrol methods employing peptidic or proteinaceous insect-specific toxins derived from microbes, plants and animals have been examined in the laboratory and field with varying results. Among the many interdependent factors involved with the production of a cost-effective pesticide--production expense, kill efficiency, environmental persistence, pest-specificity, pest resistance-development, public perception and ease of delivery--sprayable biopesticides have not yet found equal competitive footing with chemical counterparts. However, while protein/peptide-based biopesticides continue to have limitations, advances in the technology, particularly of genetically modified organisms as biopesticidal delivery systems, has continually progressed. This review highlights the varieties of delivery methods currently practiced, examining the strengths and weaknesses of each method.

Infection, transfection, and co-transfection of baculoviruses by microprojectile bombardment of larvae

The use of baculoviruses as expression vectors for heterologous proteins has been practically limited to the use of the Autographa californica multiple nucleopolyhedrovirus (AcMNPV). In this work, infection, transfection and co-transfection events with the baculoviruses AcMNPV and Trichoplusia ni granulovirus (TnGV) were accomplished by bombardment of T. ni first-instar larvae with microprojectiles coated with virions, viral DNA, and viral DNA and a transfer vector, respectively. A series of shooting conditions were tested until positive results were obtained. The use of 1.6 microm gold particles at 900 psi shooting pressure, 400 Torr vacuum, 7 cm distance to target, on sets of 20 first-instar larvae held in a 16 mm diameter container, proved to be the best shooting conditions. Typical infection symptoms were shown by larvae when shot with viruses or viral DNA from AcMNPV or TnGV. Co-transfected recombinant AcMNPV and TnGV were identified by the formation of occlusion bodies and GFP, respectively, in bombarded larvae. This technique opens a wide range of possibilities, not only to use an extensive number of baculoviruses as expression vectors for heterologous proteins, but also be used to infect, transfect or co-transfect a wide variety of viruses into animal cells.

Introduction to the use of baculoviruses as biological insecticides

Baculoviruses are widely used both as protein expression vectors and as insect pest control agents. This section provides an overview of the baculovirus lifecycle and use of baculoviruses as insecticidal agents. This chapter includes discussion of the pros and cons for use of baculoviruses as insecticides, and progress made in genetic enhancement of baculoviruses for improved insecticidal efficacy. Formulation and application of baculoviruses for pest control purposes are described elsewhere.

Fighting the global pest problem: preface to the special Toxicon issue on insecticidal toxins and their potential for insect pest control

Arthropod pests are responsible for major crop devastation and are vectors for the transmission of new and re-emerging diseases in humans and livestock. Despite many years of effective control by conventional agrochemical insecticides, a number of factors are threatening the effectiveness and continued use of these agents. These include the development of insecticide resistance and use-cancellation or de-registration of some insecticides due to human health and environmental concerns. Several approaches are being investigated for the design of new (bio)pesticides. These include the development of transgenic plants and recombinant baculoviruses as delivery systems for a variety of insect-selective toxins. Additional approaches for the development of foliar sprays include the rational design of peptidomimetics based on the key residues of these toxins that interact with the insect target. This special issue provides an overview of these phyletically selective animal, plant and microbial toxins and their diverse mechanisms of action to paralyze or kill arthropods. In addition, it reviews their potential for biopesticide discovery and validation of novel insecticide targets and provides an overview of the strengths and weaknesses of biopesticides in the global control of arthropod pests.

Arachnid toxinology in Australia: From clinical toxicology to potential applications

The unique geographic isolation of Australia has resulted in the evolution of a distinctive range of Australian arachnid fauna. Through the pioneering work of a number of Australian arachnologists, toxinologists, and clinicians, the taxonomy and distribution of new species, the effective clinical treatment of envenomation, and the isolation and characterisation of the many distinctive neurotoxins, has been achieved. In particular, work has focussed on several Australian arachnids, including red-back and funnel-web spiders, paralysis ticks, and buthid scorpions that contain neurotoxins capable of causing death or serious systemic envenomation. In the case of spiders, species-specific antivenoms have been developed to treat envenomed patients that show considerable cross-reactivity. Both in vitro and clinical case studies have shown they are particularly efficacious in the treatment of envenomation by spiders even from unrelated families. Despite their notorious reputation, the high selectivity and potency of a unique range of toxins from the venom of Australian arachnids will make them invaluable molecular tools for studies of neurotransmitter release and vesicle exocytosis as well as ion channel structure and function. The venoms of funnel-web spiders, and more recently Australian scorpions, have also provided a previously untapped rich source of insect-selective neurotoxins for the future development of biopesticides and the characterisation of previously unvalidated insecticide targets. This review provides a historical viewpoint of the work of many toxinologists to isolate and characterise just some of the toxins produced by such a unique group of arachnids and examines the potential applications of these novel peptides.

New measures of insecticidal efficacy and safety obtained with the 39K promoter of a recombinant baculovirus

Baculoviruses are orally infectious to insects and considered to be natural insecticides. To enhance their speed-of-kill these viruses were engineered to express arthropod neurotoxins under the control of various strong promoters. Although this strategy proved to be efficient, it raised recently concerns about safety. We analyzed the speed-of-kill and safety of Autographa californica multiple nucleopolyhedrovirus expressing the insecticidal scorpion neurotoxin AaIT and found that the mortality of Helicoverpa armigera larvae was enhanced significantly when the expression was controlled by the baculovirus delayed-early promoter 39K rather than the very late promoter p10. This improvement was also reflected in better protection of cotton leaves on which these insects were fed. Using lacZ as a sensitive reporter we also found that expression driven by the 39K promoter was detected in insect but not in mammalian cells. These results imply that by selection of an appropriate viral promoter, engineered baculoviruses may comply with the high standard biosafety requirements from a genetically modified organism (GMO). Our results provide further support for the potential use of engineered baculoviruses in insect pest control in a safely manner.