Loxoscelism

Standardization of lipid sample preparation for monitoring phospholipase activity

Phospholipase enzymes, such as A1, A2, B, and D, are found in the venom of venomous animals, including brown spiders. Phospholipase D (PLD) isoforms from brown spider venom can cause dermonecrosis, hemolysis, and nephrotoxicity. New methods to monitor PLD activity are essential for understanding its mechanisms and molecular characteristics. One effective approach is using 31P nuclear magnetic resonance (31P NMR) spectroscopy to track PLD enzymatic activity by identifying the 31P signals of phosphorylated substrates and products. However, sample preparation for 31P NMR is challenging, as the lipid substrates' carbon chain length and unsaturation degree can affect solubilization, oxidation, and enzyme interaction, impacting the reaction kinetics. This study standardizes a phospholipid sample preparation method with fatty acids of different chain lengths for monitoring PLD activity. The addition of CHAPS detergent is essential for solubilizing lipids with long-chain fatty acids, but its concentration needs optimization, as higher amounts can inhibit PLD activity. Storing lipids in ethanol, forming lipid films, and injecting nitrogen into stock solutions improved lipid quantification and assay reproducibility. These standardized conditions can be adapted to other experimental approaches for monitoring phospholipase activity.

Conservative Reconstruction of the Lower Limb with a Bilayer Porous Collagen Matrix after a Spider Bite

ABSTRACT

Brown recluse spider bites may cause symptoms ranging from local cutaneous reactions to systemic visceral loxoscelism. Most bites are self-limiting, but some can lead to necrotic ulcerations with severe complications and soft tissue defects. Necrotizing ulcers are uncommon and have various clinical presentations, so no standard treatment exists. A 68-year-old man required medical attention after getting a spider bite while traveling in Tanzania. After returning to Italy, the patient presented with a posterior lower limb black papule, local edema, and fever. The lesion quickly ulcerated with an eschar. Medical history and symptoms suggested a brown recluse spider bite. Ulcer management was conservative, with careful surgical debridement and a two-step reconstruction using a split-thickness skin graft and a bilayer porous collagen matrix. Treatment resulted in functional recovery and acceptable aesthetics.

Differential Cellular Responses to Class I and II Sphingomyelinase D: Unraveling the Mechanisms of Loxosceles Venom-Induced Dermonecrosis and Potential Therapeutic Targets

Dermonecrosis resulting from Loxosceles spider envenomation, primarily driven by the enzyme sphingomyelinase D (SMase D), is characterized by severe inflammation and nonhealing wounds. SMases can be classified as Class I or II based on their structural characteristics. Class I exhibits greater dermonecrotic activity than Class II; however, the intracellular mechanisms responsible for this difference remain poorly understood. The differential transcriptomics analysis of human keratinocytes treated with each toxin revealed that Class I primarily activates pathways associated with proteolytic activity and apoptosis. In contrast, Class II uniquely upregulates key genes, including PIM-1, MCL-1, PAI-1, p21, and c-FOS, which support cell survival and inhibit apoptosis. These pathways also facilitate tissue repair and keratinocyte proliferation during wound healing, particularly through signaling mechanisms involving Substance P and VEGF-A. RT-qPCR confirmed these findings, with protein level evaluations indicating the sustained upregulation of VEGF-A exclusively in keratinocytes treated with Class II. We identified Substance P and VEGF-A as potential therapeutic targets for managing cutaneous loxoscelism, providing valuable insights into the cellular mechanisms underlying the distinct toxic effects of the two SMase D isoforms. By elucidating these pathways, this study enhances our understanding of loxoscelism's pathophysiology and highlights strategies for therapeutic intervention in dermonecrotic injuries caused by spider venom.

Venom from Loxosceles Spiders Collected in Southeastern and Northeastern Brazilian Regions Cause Hemotoxic Effects on Human Blood Components

Spiders of the genus Loxosceles represent a public health problem in Brazil due to the severity of the cutaneous and systemic effects that may result from their bite. In the systemic form of loxoscelism, hemolytic anemia, thrombocytopenia, and disseminated intravascular coagulation can occur. Despite the seriousness of Loxosceles accidents, the venom of some species has not yet been properly characterized considering these hemotoxic effects, such as that of Loxosceles amazonica, Loxosceles aff. Variegata, and Loxosceles similis. To better understand their toxic potential, this study aimed to characterize the hematotoxic properties of these Loxosceles venoms. The crude venom was obtained from specimens of L. amazonica, L. aff. Variegata, and L. similis available from Funed's arachnidary. In washed platelets, L. aff. variegata inhibited platelet aggregation induced by collagen and convulxin, whereas L. amazonica and L. similis venoms were able to induce platelet aggregation. In the in vitro hemolysis assays, all venoms experimentally induced direct hemolysis of human erythrocytes in a concentration-dependent manner, with different intensities. Furthermore, evidence suggest that the ABO and Rh systems may influence hemolytic activity. Finally, the studied Loxosceles venoms degraded fibrinogen, suggesting possible alterations in the coagulation cascade. Based in the here-presented preliminary study, in vivo assays in model animals are needed to verify the real toxic potential of these species' venom, building up knowledge to elucidate the action of Loxosceles venoms in blood.

The combined treatment of gold nanoparticles associated with photobiomodulation accelerate the healing of dermonecrotic lesion

Introduction: The search for fast and efficient treatment for dermonecrotic lesions caused by the venom of the spider from the Loxosceles simillis, is a demand in health. Prednisolone is one of the most used drugs, however it has side effects. In this context, addictionally gold nanoparticles (GNPs) have anti-inflammatory, antioxidant, and antibacterial properties. The use of photobiomodulation has show to be efficient in the process of tissue repair. Therefore, the purpose of this study was to investigate the anti-inflammatory effect of photobiomodulation and GNPs associated or not with a low concentration of prednisolone in animal models of dermonecrotic lesion.Methodology: For this, rabbits with venon-induced dermonecrotic lesion were subjected to topical treatment with prednisolone + laser or GNPs + laser or Pred-GNPs + laser. The area of edema, necrosis and erythema were measured. On the last day of treatment, the animals were euthanized to remove the organs for histopathological and biochemical analysis.Results: All treatments combinations were effective in promoting the reduction of necrotic tissue and erythema.Conclusion: With this results, we suggest that the use of laser and nanoparticles, associated or not with prednisolone, should be considered for the treatment of dermonecrotic injury.

Loxosceles amazonica Brown Spider venom: Insights into enzymatic activities, immunorecognition, and novel phospholipase D isoforms

The Loxosceles genus represents one of the main arachnid genera of medical importance in Brazil. Despite the gravity of Loxosceles-related accidents, just a handful of species are deemed medically important and only a few have undergone comprehensive venom characterization. Loxosceles amazonica is a notable example of a potentially dangerous yet understudied Loxosceles species. While there have been limited reports of accidents involving L. amazonica to date, accidents related to Loxosceles are increasing in the North and Northeast regions of Brazil, where L. amazonica has been reported. In this work, we provide a complementary biochemical and immunological characterization of L. amazonica venom, considering its most relevant enzymatic activities and its immunorecognition and neutralization by current therapeutic antivenoms. Additionally, a cDNA library enriched with phospholipase D (PLD) sequences from L. amazonica venom glands was built and subsequently sequenced. The results showed that L. amazonica venom is well immunorecognised by all the tested antibodies. Its venom also displayed proteolytic, hyaluronidase, and sphingomyelinase activities. These activities were at least partially inhibited by available antivenoms. With cDNA sequencing of PLDs, seven new putative isoforms were identified in the venom of L. amazonica. These results contribute to a better knowledge of the venom content and activities of a synanthropic, yet understudied, Loxosceles species. In vivo assays are essential to confirm the medical relevance of L. amazonica, as well as to assess its true toxic potential and elucidate its related pathophysiology.

Novel insights into the application of recombinant mutated phospholipases D as antigens for developing new strategies against Loxoscelism

Loxoscelism is the pathological condition triggered by a brown spider bite. The venom of these spiders is rich in phospholipases D (PLDs), which can induce virtually all local and systemic manifestations. Recombinant mutated PLDs from clinically relevant Loxosceles species in South America have been investigated as potential antigens to develop novel therapeutic strategies for loxoscelism. However, certain gaps need to be addressed before a clinical approach can be implemented. In this study, we examined the potential of these recombinant mutated PLDs as antigens by testing some variations in the immunization scheme. Furthermore, we evaluated the efficacy of the produced antibodies in neutralizing the nephrotoxicity and sphingomyelinase activity of brown spider venoms. Our findings indicate that the number of immunizations has a greater impact on the effectiveness of neutralization compared to the amount of antigen. Specifically, two or three doses were equally effective in reducing dermonecrosis and edema. Additionally, three immunizations proved to be more effective in neutralizing mice lethality than one or two. Moreover, immunizations mitigated the signs of kidney injury, a crucial aspect given that acute renal failure is a serious systemic complication. In vitro inhibition of the sphingomyelinase activity of Loxosceles venoms, a key factor in vivo toxicity, was nearly complete after incubation with antibodies raised against these antigens. These findings underscore the importance of implementing an effective immunization scheme with multiple immunizations, without the need for high antigen doses, and enhances the spectrum of neutralization exhibited by antibodies generated with these antigens. In summary, these results highlight the strong potential of these antigens for the development of new therapeutic strategies against cutaneous and systemic manifestations of loxoscelism.

Enlightening the toxinological dark matter of spider venom enzymes

Spiders produce highly adapted venoms featuring a complex mixture of biomolecules used mainly for hunting and defense. The most prominent components are peptidic neurotoxins, a major focus of research and drug development, whereas venom enzymes have been largely neglected. Nevertheless, investigation of venom enzymes not only reveals insights into their biological functions, but also provides templates for future industrial applications. Here we compared spider venom enzymes validated at protein level contained in the VenomZone database and from all publicly available proteo-transcriptomic spider venom datasets. We assigned reported enzymes to cellular processes and known venom functions, including toxicity, prey pre-digestion, venom preservation, venom component activation, and spreading factors. Our study unveiled extensive discrepancy between public databases and publications with regard to enzyme coverage, which impedes the development of novel spider venom enzyme-based applications. Uncovering the previously unrecognized abundance and diversity of venom enzymes will open new avenues for spider venom biodiscovery.

Role of ErbB and IL-1 signaling pathways in the dermonecrotic lesion induced by Loxosceles sphingomyelinases D

Sphingomyelinase D (SMase D), the main toxic component of Loxosceles venom, has a well-documented role on dermonecrotic lesion triggered by envenomation with these species; however, the intracellular mechanisms involved in this event are still poorly known. Through differential transcriptomics of human keratinocytes treated with L. laeta or L. intermedia SMases D, we identified 323 DEGs, common to both treatments, as well as upregulation of molecules involved in the IL-1 and ErbB signaling. Since these pathways are related to inflammation and wound healing, respectively, we investigated the relative expression of some molecules related to these pathways by RT-qPCR and observed different expression profiles over time. Although, after 24 h of treatment, both SMases D induced similar modulation of these pathways in keratinocytes, L. intermedia SMase D induced earlier modulation compared to L. laeta SMase D treatment. Positive expression correlations of the molecules involved in the IL-1 signaling were also observed after SMases D treatment, confirming their inflammatory action. In addition, we detected higher relative expression of the inhibitor of the ErbB signaling pathway, ERRFI1, and positive correlations between this molecule and pro-inflammatory mediators after SMases D treatment. Thus, herein, we describe the cell pathways related to the exacerbation of inflammation and to the failure of the wound healing, highlighting the contribution of the IL-1 signaling pathway and the ERRFI1 for the development of cutaneous loxoscelism.

Comparative Biochemical, Structural, and Functional Analysis of Recombinant Phospholipases D from Three Loxosceles Spider Venoms

Spiders of Loxosceles genus are widely distributed and their venoms contain phospholipases D (PLDs), which degrade phospholipids and trigger inflammatory responses, dermonecrosis, hematological changes, and renal injuries. Biochemical, functional, and structural properties of three recombinant PLDs from L. intermedia, L. laeta, and L. gaucho, the principal species clinically relevant in South America, were analyzed. Sera against L. gaucho and L. laeta PLDs strongly cross-reacted with other PLDs, but sera against L. intermedia PLD mostly reacted with homologous molecules, suggesting underlying structural and functional differences. PLDs presented a similar secondary structure profile but distinct melting temperatures. Different methods demonstrated that all PLDs cleave sphingomyelin and lysophosphatidylcholine, but L. gaucho and L. laeta PLDs excelled. L. gaucho PLD showed greater "in vitro" hemolytic activity. L. gaucho and L. laeta PLDs were more lethal in assays with mice and crickets. Molecular dynamics simulations correlated their biochemical activities with differences in sequences and conformations of specific surface loops, which play roles in protein stability and in modulating interactions with the membrane. Despite the high similarity, PLDs from L. gaucho and L. laeta venoms are more active than L. intermedia PLD, requiring special attention from physicians when these two species prevail in endemic regions.

The C-terminal mutation beyond the catalytic site of brown spider phospholipase D significantly impacts its biological activities

Loxosceles spider envenomation results in dermonecrosis, principally due to phospholipases D (PLDs) present in the venom. These enzymes have a strongly conserved sequence, ₂₇₃ATXXDNPW₂₈₀, in the C-terminal region (SMD-tail) that make contact with β-sheets of the TIM barrel, in which the amino acids Asp277 and Trp280 establish the energetically strongest contacts. The SMD-tail is conserved in PLDs from different species but absent in the non-toxic PLD ancestral glycerophosphodiester phosphodiesterases (GDPDs). This work aims to understand the role of the C-terminal region in the structural stability and/or function of phospholipases D. Through site-directed mutagenesis of the rLiD1 protein (recombinant Loxosceles intermedia dermonecrotic protein 1), we produced two mutants: rLiD1D277A and rLiD1W280A (both with sphingomyelinase activity), in which Asp277 and Trp280 were replaced by alanine. rLiD1D277A showed similar sphingomyelinase activity but at least 2 times more dermonecrotic activity than rLiD1 (wild-type protein). Conversely, while the rLiD1W280A displayed a slight increase in sphingomyelinase activity, its biological activity was similar or lower compared to rLiD1, potentially due to its decreased thermostability and formation of amyloid aggregates. In conclusion, these new findings provide evidence that SMD-tail mutants impact the structure and function of these proteins and point out that residues outside the active site can even increase the function of these enzymes.

Brown Spider Venom Phospholipase-D Activity upon Different Lipid Substrates

Brown spider envenomation results in dermonecrosis, characterized by an intense inflammatory reaction. The principal toxins of brown spider venoms are phospholipase-D isoforms, which interact with different cellular membrane components, degrade phospholipids, and generate bioactive mediators leading to harmful effects. The Loxosceles intermedia phospholipase D, LiRecDT1, possesses a loop that modulates the accessibility to the active site and plays a crucial role in substrate. In vitro and in silico analyses were performed to determine aspects of this enzyme's substrate preference. Sphingomyelin d18:1/6:0 was the preferred substrate of LiRecDT1 compared to other Sphingomyelins. Lysophosphatidylcholine 16:0/0:0 was preferred among other lysophosphatidylcholines, but much less than Sphingomyelin d18:1/6:0. In contrast, phosphatidylcholine d18:1/16:0 was not cleaved. Thus, the number of carbon atoms in the substrate plays a vital role in determining the optimal activity of this phospholipase-D. The presence of an amide group at C2 plays a key role in recognition and activity. In silico analyses indicated that a subsite containing the aromatic residues Y228 and W230 appears essential for choline recognition by cation-π interactions. These findings may help to explain why different cells, with different phospholipid fatty acid compositions exhibit distinct susceptibilities to brown spider venoms.

Production and Functional Evaluation of Anti-Loxosceles Sera Raised by Immunizations of Rabbits with Mutated Recombinant Phospholipases-D

Loxoscelism is the clinical condition triggered after the bite of spiders of the genus Loxosceles. The main species involved in accidents in South America are L. intermedia, L. laeta, and L. gaucho. The only specific treatment is the anti-Loxosceles serum produced with crude venoms. As phospholipases D (PLDs) trigger most of the effects observed in accidents, we developed and evaluated second-generation sera using mutated PLDs as antigens. Three isoforms of PLDs with site-directed mutations without biological activities were used for rabbit immunizations: D32A-E34A (L. gaucho), W230A (L. intermedia), and H12A-H47A (L. laeta). Sera were produced using crude venoms of three species of Loxosceles enriched with mutated recombinant PLDs (MIX) or using only mutated PLDs (REC). Immunizations stimulated the immune system from the second immunization with higher antibody production in the REC group. In vivo neutralization assays demonstrated that both sera reduced edema and dermonecrosis caused by Loxosceles intermedia crude venom. Follow-up of animals during the immunization protocols and in the neutralization assays demonstrated that the mutated proteins and the sera are safe. Results demonstrate the potential of using mutated recombinant PLDs in total or partial replacement of Loxosceles venoms in animal immunizations to produce anti-Loxosceles sera for treatments of Loxoscelism.

Systemic Loxoscelism, Less Frequent but More Deadly: The Involvement of Phospholipases D in the Pathophysiology of Envenomation

Bites of Loxosceles spiders can lead to a set of clinical manifestations called loxoscelism, and are considered a public health problem in many regions. The signs and symptoms of loxoscelism are divided into cutaneous and systemic forms. The former is more frequent and includes signs of envenoming at the bite site or neighboring regions. Systemic loxoscelism, although much less frequent, is associated with complications, and can even lead to death. It may include intravascular hemolysis, acute renal failure, and thrombocytopenia. Loxosceles venoms are enriched with phospholipases D (PLDs), which are a family of isoforms found at intra-species and inter-species levels. Under experimental conditions, these enzymes reproduce the main clinical signs of loxoscelism, including an exacerbated inflammatory response at the bite site and dermonecrosis, as well as thrombocytopenia, intravascular hemolysis, and acute renal failure. The role of PLDs in cutaneous loxoscelism was described over forty years ago, when studies identified and purified toxins featured as sphingomyelinase D. More recently, the production of recombinant PLDs and discoveries about their structure and mechanism has enabled a deeper characterization of these enzymes. In this review, we describe these biochemical and functional features of Loxosceles PLDs that determine their involvement in systemic loxoscelism.

Suspected Brown Recluse Spider Envenomation: Missed Diagnosis and Delayed Treatment of Loxoscelism: A Case Report

CASE

We report the case of a previously healthy 51-year-old man who presented to our hospital after worsening clinical appearance of his left ring finger, despite antibiotics and previous surgical drainage for suspected abscess at an outside institution 3 weeks ago. He was admitted to our hospital for surgical debridement and decompression. After suspicion of cutaneous loxoscelism based on the clinical record and corticosteroid administration, the patient presented a favorable evolution.

CONCLUSION

Cutaneous loxoscelism caused by a spider bite is present in Europe, mainly in the Mediterranean area, and should be considered in cases of skin infections which do not respond to antibiotics.

Validation of a colorimetric LAMP to detect Loxosceles experimental envenomation

Diagnostic tests for brown spider accidents are unavailable and impact treatment decisions, increasing costs and patient risks. In this work, we used for the first time a fast, simple, and visual method based on the loop-mediated isothermal amplification assay (LAMP) to detect Loxosceles envenomation. Using the DNA from L. similis legs, we observed a high sensitivity using this test since as low as 0.32 pg of DNA could be detected. This pH-dependent colorimetric assay was 64 times more sensitive than PCR to detect spider DNA. The test was specific for Loxosceles once no cross-reaction was observed when testing DNA from different agents that cause similar dermonecrotic injuries. The test allowed the detection of Loxosceles intermedia DNA from hair, serum, and exudate samples obtained from experimentally-envenomed rabbit within 72 h. The method sensitivity varied according to the sample and the collection time, reaching 100% sensitivity in serum and hair, respectively, 1 h and 24 h after the experimental envenomation. Due to its ease of execution, speed, sensitivity, and specificity, LAMP presents an excellent potential for identifying Loxosceles spp. Envenomation. This can reduce the burden on the Health System and the morbidity for the patient by implementing the appropriate therapy immediately.In addition, this work opens up the perspective to other venomous animal accident identification using LAMP.

Protective Effectiveness of an Immunization Protocol Against the Toxic Effects of Loxosceles intermedia Venom in Rabbits

Loxosceles spp. (brown spiders) bites are responsible for the development of a syndrome consisting mainly of dermonecrotic lesions, and also systemic effects. Rabbits are one of the main experimental models used for better understanding the systemic and local effects of Loxosceles venom. The aim of this study is to evaluate the toxic and protective effects of rabbits immunized with Loxosceles spp. venom. Male New Zealand rabbits were allocated as a control group (CG; n = 5) that received adjuvant (Montanide) and phosphate-buffer saline (PBS), or as venom group (VG; n = 5) that received 21 μg of Loxosceles venom using Montanide as adjuvant. After five immunization cycles, a trial with 7 μg of Loxosceles intermedia (L. intermedia) venom was performed, and dermonecrotic lesions were measured. The rabbits were then euthanized, and their organs were collected for histopathology analysis. Rabbits that had undergone Loxosceles venom immunization protocol showed minor clinical disturbances during the experimental period. The used immunization protocol protected the rabbits against the toxic effect of the Loxosceles venom because they showed minor clinical disturbances during the experimental period.

Systemic loxoscelism induced warm autoimmune hemolytic anemia: clinical series and review

OBJECTIVES

Describe the development of warm autoimmune hemolytic anemia warm (AIHA) secondary to a brown recluse spider (Loxosceles reclusa) bite is known as systemic loxoscelism; and review epidemiology, clinical manifestations, diagnostic work-up, pathophysiology, and treatment options associated with warm AIHA secondary to systemic loxoscelism.

METHODS

Cases series of two cases of warm AIHA due to systemic loxoscelism and a review of the current literature: epidemiology, clinical manifestations, diagnostic work-up, pathophysiology, and treatment options associated with warm AIHA secondary to systemic loxoscelism.

RESULTS

Presented here are two cases of warm AIHA due to systemic loxoscelism. Each patient was generally healthy appearing and presented with symptomatic anemia in the setting of brown recluse spider bites. Both patients were eventually found to have warm AIHA. Upon recognition of the diagnosis, the patients were started on corticosteroids and aggressive intravenous fluid hydration. In addition, they received transfusions of packed red blood cells. Their clinical courses improved, and they recovered to eventually be discharged home.

CONCLUSION

Envenomation by a brown recluse spider, Loxosceles reclusa, can result in systemic loxoscelism which can cause warm AIHA. The diagnosis of warm AIHA is confirmed by the direct antiglobulin/Coomb's test. Warm AIHA can be a life-threatening disease process. Hemodynamic support with intravenous fluids and RBC transfusion is the initial step in the management of these patients. Corticosteroids are the mainstay of current management. Second line treatments include rituximab. Rarely patients require splenectomy for refractory disease. Corticosteroids should be tapered over a three-month period.

Brown spider (Loxosceles sp.) bite and COVID-19: A case report

We present the case of a 32-year-old male patient hospitalized during the COVID-19 pandemic because of a Brown spider bite on his lower lip. The Brown spider accident occurred in southern Brazil; at hospital admission, the patient presented on his lip: edema, pustules, necrotic regions, and ulcerations. The patient complained of lower back pain, fever and dyspnea. Laboratory tests showed monocytosis, leukocytosis, neutrophilia, increased D-dimer levels, C-reactive protein, glutamate-pyruvate transaminase, delta bilirubin, creatine phosphokinase, procalcitonin, and fibrinogen. The patient was hospitalized and a multi-professional team carried out the treatment. The medical team diagnosed loxoscelism with moderate changes. The dentist treated the oral cavity. The patient began to develop nausea, vomiting, and desaturation episodes during hospitalization. A computed tomography of the chest was performed, which showed signs of viral infection. The RT-PCR test for COVID-19 was positive. The systemic conditions worsened (renal dysfunction, systemic inflammatory response, pulmonary complications). This condition may have resulted from the association of the two diseases (loxoscelism and COVID-19), leading to the patient's death. This case illustrates the difficulties and risks in treating patients with venomous animal accidents during the pandemic, and the importance of a multi-professional team in treating such cases.

A protective vaccine against the toxic activities following Brown spider accidents based on recombinant mutated phospholipases D as antigens

Accidents involving Brown spiders are reported throughout the world. In the venom, the major toxins involved in the deleterious effects are phospholipases D (PLDs). In this work, recombinant mutated phospholipases D from three endemic species medically relevant in South America (Loxosceles intermedia, L. laeta and L. gaucho) were tested as antigens in a vaccination protocol. In such isoforms, key amino acid residues involved in catalysis, magnesium-ion coordination, and binding to substrates were replaced by Alanine (H12A-H47A, E32A-D34A and W230A). These mutations eliminated the phospholipase activity and reduced the generation of skin necrosis and edema to residual levels. Molecular modeling of mutated isoforms indicated that the three-dimensional structures, topologies, and surface charges did not undergo significant changes. Mutated isoforms were recognized by sera against the crude venoms. Vaccination protocols in rabbits using mutated isoforms generated a serum that recognized the native PLDs of crude venoms and neutralized dermonecrosis and edema induced by L. intermedia venom. Vaccination of mice prevented the lethal effects of L. intermedia crude venom. Furthermore, vaccination of rabbits prevented the cutaneous lesion triggered by the three venoms. These results indicate a great potential for mutated recombinant PLDs to be employed as antigens in developing protective vaccines for Loxoscelism.

A prokaryote system optimization for rMEPLox expression: A promising non-toxic antigen for Loxosceles antivenom production

Loxoscelism is the most dangerous araneism form in Brazil and antivenom therapy is the recommended treatment. Antivenom is produced by horse immunization with Loxosceles spider venom, which is toxic for the producer animal. Moreover, due to the high amount of venom required for horse hyperimmunization, new strategies for antigens obtention have been proposed. In this sense, our research group has previously produced a non-toxic recombinant multiepitopic protein derived from Loxosceles toxins (rMEPLox). rMEPLox was a successful immunogen, being able to induce the production of neutralizing antibodies, which could be used in the Loxoscelism treatment. However, rMEPLox obtention procedure requires optimization, as its production needs to be scaled up to suit antivenom manufacture. Therefore, an effective protocol development for rMEPlox production would be advantageous. To achieve this objective, we evaluated the influence of different cultivation conditions for rMEPLox optimum expression. The optimum conditions to obtain large amounts of rMEPlox were defined as the use of C43(DE3)pLysS as a host strain, 2xTY medium, 0.6 mM IPTG, biomass pre induction of OD600nm = 0.4 and incubation at 30 °C for 16 h. Following the optimized protocol, 39.84 mg/L of soluble rMEPLox was obtained and tested as immunogen. The results show that the obtained rMEPLox preserved the previously described immunogenicity, and it was able to generate antibodies that recognize different epitopes of the main Loxosceles venom toxins, which makes it a promising candidate for the antivenom production for loxoscelism treatment.

Brown spider venom toxins: what are the functions of astacins, serine proteases, hyaluronidases, allergens, TCTP, serpins and knottins?

Accidents caused by the bites of brown spiders (Loxosceles) generate a clinical condition that often includes a threatening necrotic skin lesion near the bite site along with a remarkable inflammatory response. Systemic disorders such as hemolysis, thrombocytopenia, and acute renal failure may occur, but are much less frequent than the local damage. It is already known that phospholipases D, highly expressed toxins in Loxosceles venom, can induce most of these injuries. However, this spider venom has a great range of toxins that probably act synergistically to enhance toxicity. The other protein classes remain poorly explored due to the difficulty in obtaining sufficient amounts of them for a thorough investigation. They include astacins (metalloproteases), serine proteases, knottins, translationally controlled tumor proteins (TCTP), hyaluronidases, allergens and serpins. It has already been shown that some of them, according to their characteristics, may participate to some extent in the development of loxoscelism. In addition, all of these toxins present potential application in several areas. The present review article summarizes information regarding some functional aspects of the protein classes listed above, discusses the directions that could be taken to materialize a comprehensive investigation on each of these toxins as well as highlights the importance of exploring the full venom repertoire.

Prospective Use of Brown Spider Venom Toxins as Therapeutic and Biotechnological Inputs

Brown spider (genus Loxosceles) venoms are mainly composed of protein toxins used for predation and defense. Bites of these spiders most commonly produce a local dermonecrotic lesion with gravitational spread, edema and hemorrhage, which together are defined as cutaneous loxoscelism. Systemic loxoscelism, such as hematological abnormalities and renal injury, are less frequent but more lethal. Some Loxosceles venom toxins have already been isolated and extensively studied, such as phospholipases D (PLDs), which have been recombinantly expressed and were proven to reproduce toxic activities associated to the whole venom. PLDs have a notable potential to be engineered and converted in non-toxic antigens to produce a new generation of antivenoms or vaccines. PLDs also can serve as tools to discover inhibitors to be used as therapeutic agents. Other Loxosceles toxins have been identified and functionally characterized, such as hyaluronidases, allergen factor, serpin, TCTP and knottins (ICK peptides). All these toxins were produced as recombinant molecules and are biologically active molecules that can be used as tools for the potential development of chemical candidates to tackle many medical and biological threats, acting, for instance, as antitumoral, insecticides, analgesic, antigens for allergy tests and biochemical reagents for cell studies. In addition, these recombinant toxins may be useful to develop a rational therapy for loxoscelism. This review summarizes the main candidates for the development of drugs and biotechnological inputs that have been described in Brown spider venoms.

Description of a serpin toxin in Loxosceles (Brown spider) venoms: Cloning, expression in baculovirus-infected insect cells and functional characterization

Several classes of toxins are present in the venom of Brown spiders (Loxosceles genus), some of them are highly expressed and others are less expressed. In this work, we aimed to clone the sequence of a little expressed novel toxin from Loxosceles venom identified as a serine protease inhibitor (serpin), as well as to express and characterize its biochemical and biological properties. It was named LSPILT, derived from Loxoscelesserine protease inhibitor-like toxin. Multiple alignment analysis revealed high identity between LSPILT and other serpin molecules from spiders and crab. LSPILT was produced in baculovirus-infected insect cells, resulting in a 46-kDa protein fused to a His-tag. Immunological assays showed epitopes in LSPILT that resemble native venom toxins of Loxosceles spiders. The inhibitory activity of LSPILT on trypsin was found both by reverse zymography and fluorescent gelatin-degradation assay. Additionally, LSPILT inhibited the complement-dependent lysis of Trypanosoma cruzi epimastigotes, reduced thrombin-dependent clotting and suppressed B16-F10 melanoma cells migration. Results described herein prove the existence of conserved serpin-like toxins in Loxosceles venoms. The availability of a recombinant serpin enabled the determination of its biological and biochemical properties and indicates potential applications in future studies regarding the pathophysiology of the envenoming or for biotechnological purposes.

Brown Spiders' Phospholipases-D with Potential Therapeutic Applications: Functional Assessment of Mutant Isoforms

Phospholipases-D (PLDs) found in Loxosceles spiders' venoms are responsible for the dermonecrosis triggered by envenomation. PLDs can also induce other local and systemic effects, such as massive inflammatory response, edema, and hemolysis. Recombinant PLDs reproduce all of the deleterious effects induced by Loxosceles whole venoms. Herein, wild type and mutant PLDs of two species involved in accidents-L. gaucho and L. laeta-were recombinantly expressed and characterized. The mutations are related to amino acid residues relevant for catalysis (H12-H47), magnesium ion coordination (E32-D34) and binding to phospholipid substrates (Y228 and Y228-Y229-W230). Circular dichroism and structural data demonstrated that the mutant isoforms did not undergo significant structural changes. Immunoassays showed that mutant PLDs exhibit conserved epitopes and kept their antigenic properties despite the mutations. Both in vitro (sphingomyelinase activity and hemolysis) and in vivo (capillary permeability, dermonecrotic activity, and histopathological analysis) assays showed that the PLDs with mutations H12-H47, E32-D34, and Y228-Y229-W230 displayed only residual activities. Results indicate that these mutant toxins are suitable for use as antigens to obtain neutralizing antisera with enhanced properties since they will be based on the most deleterious toxins in the venom and without causing severe harmful effects to the animals in which these sera are produced.

History, challenges and perspectives on Loxosceles (brown spiders) antivenom production in Brazil

Antivenom is the only effective therapy for treating any envenomation. Despite its obvious public health importance, the laborious process of procuring, distributing and controlling the quality of such immunobiologicals is being neglected. Brazil is fully self-sufficient in the production of antivenoms. Since the 1950s, Loxoscelism, a syndrome with an onset after a spider bite from specimens of the Loxosceles genus occurs, is considered a public health issue. The Brazilian history in developing antivenom therapy, its production hindrances, and other challenges are discussed in this paper, as well as some promising novelties that can improve production and processing of Loxosceles antivenom.

Engineered antigen containing epitopes from Loxosceles spp. spider toxins induces a monoclonal antibody (Lox-mAb3) against astacin-like metalloproteases

Loxoscelism pose a health issue in the South America. The treatment for these accidents is based on the administration of antivenom produced in animals immunized with Loxosceles venom. In this work, a previously produced non-toxic multiepitopic chimeric protein (rMEPlox), composed of epitopes derived from the main toxins families (sphyngomielinase-D, metalloproteases, and hyaluronidases) of Loxosceles spider venoms, was used as antigen to produce monoclonal antibodies (mAbs). A selected anti-rMEPlox mAb (Lox-mAb3) reacted with metalloprotease from L. intermedia venom and showed cross-reactivity with metalloproteses from Brazilian and Peruvian Loxosceles laeta and Loxosceles gaucho venoms in immunoassays. The sequence recognized by Lox-mAb3 (₁₈₄ENNTRTIGPFDYDSIMLYGAY₂₀₅) corresponds to the C-terminal region of Astacin-like metalloprotease 1 and the amino acid sequence IGPFDYDSI, conserved among the homologs metalloproteases sequences, is important for antibody recognition. Lox-mAb3 neutralizes the fibrinogenolytic activity caused by metalloprotease from L. intermedia spider venom in vitro, which may lead to a decrease in hemorrhagic disturbances caused by Loxosceles envenomation. Our results show, for the first time, the use of a non-toxic multiepitopic protein for the production of a neutralizing monoclonal antibody against a metalloprotease of medically important Loxosceles venoms. These results contribute for the production improvement of therapeutic antivenom against loxoscelism.

Complete neutralization of the lethality of Hemiscorpius lepturus crude venom by a novel anti-recombinant phospholipase D1 IgGs

Treatment of scorpion envenomation is a challenging issue since serotherapy is implemented by administration of polyvalent equine antisera. In our previous study we discovered that recombinant phospholipase D1 (Hl-RecPLD1) is responsible for the lethality of Hemiscorpius lepturus (H. lepturus) venom in mice. Accordingly, this study was aimed to investigate the protectivity of purified anti-Hl-RecPLD1 IgG against the lethality or major complications of H. lepturus venom. The neutralization efficiency of purified anti-Hl-RecPLD1 IgGs against sphingomyelinase activities of the crude venom and Hl-RecPLD1 was also assessed. Anti-Hl-RecPLD1 IgGs at optimum amount of 3.7 mg completely neutralized one Lethal Dose 100 (LD₁₀₀) of crude venom in mice. The anti-Hl-RecPLD1 IgGs remarkably reduced the necrosis area from 6.5 to 1 cm² in rabbit derma, induced by the crude venom. The anti-Hl-RecPLD1 IgGs remarkably reduced the sphingomyelinase and hemolytic activities of crude venom as well. In conclusion, a novel rabbit monovalent IgG against Hl-RecPLD1 was able to completely protect the mice against the lethality of H. lepturus crude venom and reduced its toxicity as well. Such monovalent anti-Hl-RecPLD1 IgGs may have potential applications in serotherapy of H. lepturus envenomation.

Local Dermonecrosis with Generalized Urticaria Probably Due to Loxosceles rufescens Bite

BACKGROUND: The spiders of the Loxosceles genus, commonly denoted as “brown spiders” or “Mediterranean recluse” or “brown recluse,” belong to the spider family Sicariidae, suborder Labidognatha, order Araneida, class Arachnida, and phylum Arthropoda. This spider is widespread in Africa and South/Central America, but it is also distributed in North America, in the West Indies, in the Mediterranean Europe, and in China. CASE REPORT: Here, we report the case of a severe dermonecrotic loxoscelism identified in Southern Italy, probably due to the bite of Loxosceles rufescens. The patient was a women admitted at hospital ER because of a little skin erythema that evolved toward a severe necrosis and ulceration within 20 days. After clinical and laboratory data excluded other local and systemic diseases, she was treated with a systemic and local therapy using corticosteroids and antibiotics with the diagnosis of loxoscelism. The healing from the local skin lesion occurred within 2 months, but the local pain, weakness, and discomfort lasted for a long time. CONCLUSION: It is the fisrt time that a possible case of systemic loxoscelism with skin generalized urticaria is reported in Italy.

Sajedi R, Pooshang Bagheri K, Sabatier JM, Shahbazzadeh D. Novel Mutant Phospholipase D from Hemiscorpius lepturus Acts as A Highly Immunogen in BALB/c Mice Against the Lethality of Scorpion Venom

Hemiscorpius lepturus (H. lepturus) which belongs to the Scorpionidae family, is the deadliest scorpion in Iran. It causes pathological manifestations like dermonecrosis, hemolysis, renal failure, necrotic ulcers, and in some cases, even death. The venom of this scorpion is well-known for its cytotoxic effects in comparison with the other venomous scorpions which show significant neurotoxic effects. Due to the painless nature of the sting of this scorpion, the clinical symptoms occur in victims 24 to 72 h post-sting. In our previous studies during the last decade, we demonstrated that the medical complications are attributable to the presence of phospholipase D (PLD) as a major toxin in the venom. With the purpose of designing and constructing a vaccine against H. lepturus for humans, animal model experiments were performed. To achieve this goal, non-toxic PLD was developed by mutation of two critical catalytic residues-His12 and His48-into alanines and the product was then denominated mut-rPLD1. The in-vivo tests showed that the mice immunized with interval doses of 10 µg of mut-rPLD1, were completely protected against 10× the LD100 of the venom. In conclusion, this mutant may be an effective vaccine candidate against scorpion envenomation by H. lepturus in future clinical studies.

Clinical aspects, diagnosis and management of Loxosceles spider envenomation: literature and case review

The genus Loxosceles comprises 140 species widely distributed around the world. These spiders are nocturnal, sedentary and remarkably nonaggressive, although they cause accidents in humans with wide degrees of severity, generating signs and symptoms that define the clinical condition known as loxoscelism. Its local signs and symptoms were first reported in 1872, and over the years, a large medical literature has been accumulated; unfortunately, it is not always trustworthy. Assessing the reliability of such information, we reviewed 120 case reports of loxoscelism published in 84 articles over the past 20 years. This search allowed us to gather information on the clinical aspects, diagnosis and treatment of loxoscelism, showing that the severity of these accidents has multiple degrees and that it is influenced by many factors. Thus, coupled with epidemiological and species occurrence information, this study can be a useful tool for the clinical practice of loxoscelism. It may support and provide a multidisciplinary view that should be taken into consideration when establishing the therapeutic approach in cases of Loxosceles envenomation.

Forty Years of the Description of Brown Spider Venom Phospholipases-D

Spiders of the genus Loxosceles, popularly known as Brown spiders, are considered a serious public health issue, especially in regions of hot or temperate climates, such as parts of North and South America. Although the venoms of these arachnids are complex in molecular composition, often containing proteins with distinct biochemical characteristics, the literature has primarily described a family of toxins, the Phospholipases-D (PLDs), which are highly conserved in all Loxosceles species. PLDs trigger most of the major clinical symptoms of loxoscelism i.e., dermonecrosis, thrombocytopenia, hemolysis, and acute renal failure. The key role played by PLDs in the symptomatology of loxoscelism was first described 40 years ago, when researches purified a hemolytic toxin that cleaved sphingomyelin and generated choline, and was referred to as a Sphingomyelinase-D, which was subsequently changed to Phospholipase-D when it was demonstrated that the enzyme also cleaved other cellular phospholipids. In this review, we present the information gleaned over the last 40 years about PLDs from Loxosceles venoms especially with regard to the production and characterization of recombinant isoforms. The history of obtaining these toxins is discussed, as well as their molecular organization and mechanisms of interaction with their substrates. We will address cellular biology aspects of these toxins and how they can be used in the development of drugs to address inflammatory processes and loxoscelism. Present and future aspects of loxoscelism diagnosis will be discussed, as well as their biotechnological applications and actions expected for the future in this field.

Brown recluse (L. rufescens) can bite in Northern Italy, too: first case report and review of the literature

The brown recluse, or fiddleback (violin) spider, is a poisonous spider of the Loxosceles genus that resides in warmer regions and old structures making the warm Mediterranean climate a natural habitat for the European species, L. rufescens Even in infested households, however, bites are rare, as they are nocturnal and unaggressive. In 2015, the first supposed death by L. rufescens occurred in Italy, but before and even after such bite, the literature on these spiders has been under-represented. This case report documents a confirmed bite by a violin spider on a medical student in Pavia, Italy. The presentation in this case was initially with general systemic, flu-like symptoms, then as cellulitis with lymphangitis that persisted for nearly 2 weeks until resolving without prolonged or complicated pathology. We present the first documented case of a L. rufescens bite in Northern Italy, to the best of our knowledge.

Effects of copaiba oil on dermonecrosis induced by Loxosceles intermedia venom

Background:

Accidents caused by spiders of the genus Loxosceles constitute an important public health problem in Brazil. The venom of Loxosceles sp induces dermonecrosis at the bite site and systemic disease in severe cases. Traditional medicine based on plant-derived products has been proven to reduce the local effects of envenomation. The present study verified the healing effects of copaiba oil on lesions induced by the venom of L. intermedia.

Methods:

Cutaneous lesions were induced on the backs of rabbits by intradermal injection of L. intermedia venom. Copaiba oil was applied topically 6 hours after injection; the treatment was repeated for 30 days, after which animal skins were removed and processed for histopathological analysis. Blood samples were also collected before and 24 hours after venom inoculation to measure the hematological parameters.

Results:

Compared to the control group, the platelet count was reduced significantly in all groups inoculated with venom, accompanied by a decreased number of heterophils in the blood. The minimum necrotic dose (MND) was defined as 2.4 μg/kg. Topical treatment with copaiba oil demonstrated a differentiated healing profile: large skin lesions were observed 10 days after venom inoculation, whereas formation of a thick crust, without scarring was observed 30 days after venom inoculation. Histopathological analysis showed no significant difference after treatment. Nevertheless, the copaiba oil treatment induced a collagen distribution similar to control skin, in marked contrast to the group that received only the spider venom injection.

Conclusions:

We conclude that copaiba oil may interfere in the healing process and thus propose it as a possible topical treatment for cutaneous lesions induced by L. intermedia venom.

Design and Production of a Recombinant Hybrid Toxin to Raise Protective Antibodies Against Loxosceles Spider Venom

Human accidents with spiders of the genus Loxosceles are an important health problem affecting thousands of people worldwide. Patients evolve to severe local injuries and, in many cases, to systemic disturbances as acute renal failure, in which cases antivenoms are considered to be the most effective treatment. However, for antivenom production, the extraction of the venom used in the immunization process is laborious and the yield is very low. Thus, many groups have been exploring the use of recombinant Loxosceles toxins, particularly phospholipases D (PLDs), to produce the antivenom. Nonetheless, some important venom activities are not neutralized by anti-PLD antibodies. Astacin-like metalloproteases (ALMPs) are the second most expressed toxin acting on the extracellular matrix, indicating the importance of its inclusion in the antigen’s formulation to provide a better antivenom. Here we show the construction of a hybrid recombinant immunogen, called LgRec1ALP1, composed of hydrophilic regions of the PLD and the ALMP toxins from Loxosceles gaucho. Although the LgRec1ALP1 was expressed as inclusion bodies, it resulted in good yields and it was effective to produce neutralizing antibodies in mice. The antiserum neutralized fibrinogenolytic, platelet aggregation and dermonecrotic activities elicited by L. gaucho, L. laeta, and L. intermedia venoms, indicating that the hybrid recombinant antigen may be a valuable source for the production of protective antibodies against Loxosceles ssp. venoms. In addition, the hybrid recombinant toxin approach may enrich and expand the alternative antigens for antisera production for other venoms.

Brown Recluse Spider Bites in Patients With Neutropenia: A Single-institution Experience

Brown recluse spider bites can cause local and systemic signs, including rash, dermonecrosis, edema, hemolysis, and acute kidney failure. These are mostly attributed to sphingomyelinase D, the main toxin. To evaluate the severity of the disease in pediatric patients with and without neutropenia, we retrospectively reviewed records of patients treated at St. Jude Children's Research Hospital between 1970 and 2015 and identified 19 patients who met the inclusion criteria. Variables of interest included the type of underlying illness, presence of neutropenia, number of days of hospitalization, disease signs and outcome of the bite, and treatments administered. We used descriptive statistics to summarize the manifestations and severity of spider bites in patients with and without neutropenia. Six patients experienced pain from the bite, 11 had erythema, 7 developed edema, and 5 had fever. The response to spider bites in neutropenic patients was no milder than that in non-neutropenic individuals. Six patients developed systemic complications. Compared with non-neutropenic patients, neutropenic patients had antibiotics prescribed more often and experienced longer hospital stays. Spider bites do not seem to have a different clinical course in neutropenic patients. Therefore, a conservative approach may be best for these patients, with close monitoring and local wound care.

Probable cutaneous loxoscelism with mild systemic symptoms: A case report from Spain

We present a case from Valencia, Spain, of a 25-year-old woman who presented with a painful erythematous skin lesion, initially diagnosed as cellulitis. The lesion was unresponsive to antibiotic treatments and progressed into a hemorrhagic blister with necrotic ulcer formation. Posterior collection of a spider from the patient's home and expert identification of the spider as Loxosceles rufescens was achieved, establishing the diagnosis of probable cutaneous loxoscelism. Symptomatic treatment, general wound care and ultimately surgery, resulted in complete recovery with minor residual scarring. This case illustrates some of the difficulties encountered in the diagnosis and treatment of loxoscelism and adds to the increasing reports of loxoscelism in the Mediterranean Basin.

Developing recombinant phospholipase D1 (rPLD1) toxoid from Iranian Hemiscorpius lepturus scorpion and its protective effects in BALB/c mice

Hemiscorpius lepturus (H. lepturus) is one of the most dangerous scorpions and the most medically important scorpion in Iran. The clinical signs of H. lepturus envenomation, including dermonecrosis, hematuria, renal failure and early death, are attributed to phospholipase D activity. This study was conducted to develop a novel recombinant phospholipase D1 (rPLD1) toxoid and investigate its immunogenicity and protective effects against the lethality of H. lepturus venom. The lethal protein recombinant phospholipase D1 was expressed from PLD H. lepturus venom gland. The rPLD1 toxin was converted into toxoid (the first toxoid of H. lepturus PLD) with a 0.25% concentration of formalin and stored for ten days at room temperature. In the toxicity test, the lethal activity of recombinant phospholipase D1 was fully inhibited. When it reached up to 3 times higher than the maximal effective concentration of the purified toxin (11.1 μg), rPLD1 toxoid was used. The sphingomyelinase activity was inhibited when up to 5.4 times of the LD100 of the purified toxin (20 μg), toxoid was used. It was then used to produce an antibody in BALB/c as an antigen and the mice were then challenged with rPLD1 toxin and the whole venom. The immunogenicity of rPLD1 toxoid was evaluated and the maximum titer of the raised antibodies was determined by ELISA assay. The optimum titer for anti-rPLD1 toxoid sera was obtained at the third intraperitoneal injection of rPLD1 toxoid, and a high titer was reached at the fourth injection in the mice. This toxoid increased the amount of antibodies and produced a protective antiserum against the whole venom of H. lepturus and rPLD1 toxin. The in-vivo test results showed that the mice were completely resistant against 200 times the LD100 of recombinant phospholipase D1 and the whole venom of H. lepturus. To conclude, rPLD1 can be used in toxoid form as an immunogen in the production of a new generation of neutralizing antibodies against the lethality and toxicity of H. lepturus whole venom.

Heterophilic antibodies in sera from individuals without loxoscelism cross-react with phospholipase D from the venom of Loxosceles and Sicarius spiders

Background

Loxoscelism is a severe human envenomation caused by Loxosceles spider venom. To the best of our knowledge, no study has evaluated the presence of antibodies against Loxosceles venom in loxoscelism patients without treatment with antivenom immunotherapy. We perform a comparative analysis for the presence of antibodies capable of recognizing Loxosceles venom in a group of patients diagnosed with loxoscelism and in a group of people without loxoscelism.

Methods

The detection of L. laeta venom, Sicarius venom and recombinant phospholipases D from Loxosceles (PLDs) in sera from people with loxoscelism (Group 1) and from healthy people with no history of loxoscelism (Group 2) was evaluated using immuno-dot blot, indirect ELISA, and Western blot.

Results

We found naturally heterophilic antibodies (IgG-type) in people without contact with Loxosceles spiders or any clinical history of loxoscelism. Either serum pools or single sera from Group 1 and Group 2 analyzed by dot blot tested positive for L. laeta venom. Indirect ELISA for venom recognition showed titles of 1:320 for Group 1 sera and 1:160 for Group 2 sera. Total IgG quantification showed no difference in sera from both groups. Pooled sera and purified IgG from sera of both groups revealed venom proteins between 25 and 32 kDa and the recombinant phospholipase D isoform 1 (rLlPLD1), specifically. Moreover, heterophile antibodies cross-react with PLDs from other Loxosceles species and the venom of Sicarius spider.

Conclusions

People without contact with the spider venom produced heterophilic antibodies capable of generating a cross-reaction against the venom of L. laeta and Sicarius spiders. Their presence and possible interference should be considered in the development of immunoassays for Loxosceles venom detection.

Recombinant Protein Containing B-Cell Epitopes of Different Loxosceles Spider Toxins Generates Neutralizing Antibodies in Immunized Rabbits

Loxoscelism is the most important form of araneism in South America. The treatment of these accidents uses heterologous antivenoms obtained from immunization of production animals with crude loxoscelic venom. Due to the scarcity of this immunogen, new alternatives for its substitution in antivenom production are of medical interest. In the present work, three linear epitopes for Loxosceles astacin-like protease 1 (LALP-1) (SLGRGCTDFGTILHE, ENNTRTIGPFDYDSIMLYGAY, and KLYKCPPVNPYPGGIRPYVNV) and two for hyaluronidase (LiHYAL) (NGGIPQLGDLKAHLEKSAVDI and ILDKSATGLRIIDWEAWR) from Loxosceles intermedia spider venom were identified by SPOT-synthesis technique. One formerly characterized linear epitope (DFSGPYLPSLPTLDA) of sphingomyelinase D (SMase D) SMase-I from Loxosceles laeta was also chosen to constitute a new recombinant multiepitopic protein. These epitopes were combined with a previously produced chimeric multiepitopic protein (rCpLi) composed by linear and conformational B-cell epitopes from SMase D from L. intermedia venom, generating a new recombinant multiepitopic protein derived from loxoscelic toxins (rMEPLox). We demonstrated that rMEPLox is non-toxic and antibodies elicited in rabbits against this antigen present reactivity in ELISA and immunoblot assays with Brazilian L. intermedia, L. laeta, L. gaucho, and L. similis spider venoms. In vivo and in vitro neutralization assays showed that anti-rMEPLox antibodies can efficiently neutralize the sphingomyelinase, hyaluronidase, and metalloproteinase activity of L. intermedia venom. This study suggests that this multiepitopic protein can be a suitable candidate for experimental vaccination approaches or for antivenom production against Loxosceles spp. venoms.

Loxosceles venom Sphingomyelinase D activates human blood leukocytes: Role of the complement system

Envenomation by Loxosceles spiders can result in severe systemic and local reactions, which are mainly triggered by Sphingomyelinase D (SMase D), a toxic component of Loxosceles venom. SMase D induces a systemic inflammatory condition similar to the reaction observed during an endotoxic shock. Considering the potent pro-inflammatory potential of Loxosceles venom and the SMase D, in this study we have used the whole human blood model to study the endotoxic-like shock triggered by SMase D. Recombinant purified SMase D from L. intermedia venom, similarly to LPS, induced activation of blood leukocytes, as observed by the increase in the expression of CD11b and TLR4, production of reactive oxygen and nitrogen species (superoxide anion and peroxynitrite) and release of TNF-α. Complement consumption in the plasma was also detected, and complement inhibition by compstatin decreased the SMase D and LPS-induced leukocyte activation, as demonstrated by a reduction in the expression of CD11b and TLR4 and superoxide anion production. Similar results were found for the L. intermedia venom, except for the production of TNF-α. These findings indicate that SMase D present in Loxosceles venom is able to activate leukocytes in a partially complement-dependent manner, which can contribute to the systemic inflammation that follows envenomation by this spider. Thus, future therapeutic management of systemic Loxosceles envenomation could include the use of complement inhibitors as adjunct therapy.

Nonhealing Wounds Caused by Brown Spider Bites: Application of Hyperbaric Oxygen Therapy

BACKGROUND

Bites by Loxosceles spiders (also known as recluse spiders or brown spiders) can cause necrotic ulcerations of various sizes and dimensions. The current standard of care for brown spider bites includes analgesics, ice, compression, elevation, antihistamines, and surgical debridement. Hyperbaric oxygen therapy (HBOT) in the treatment of brown spider bites has been administered in the early stage of ulceration, or 2 to 6 days after the bite. Unfortunately, the diagnosis of spider bite-related ulcers is often delayed and weeks or months may elapse before HBOT is considered.

OBJECTIVE

To evaluate the effect of HBOT on nonhealing wounds caused by brown spider bites in the late, chronic, nonhealing stage.

METHODS

Analysis of 3 patients with brown spider-bite healing wounds treated at The Sagol Center for Hyperbaric Medicine and Research in Israel. Patients presented 2 to 3 months after failure of other therapies including topical dressings, antibiotics, and corticosteroids. All patients were treated with daily 2 ATA (atmospheres absolute) with 100% oxygen HBOT sessions.

RESULTS

All 3 patients were previously healthy without any chronic disease. Their ages were 30, 42, and 73 years. They were treated once daily for 13, 17, and 31 sessions, respectively. The wounds of all 3 patients healed, and there was no need for additional surgical intervention. There were no significant adverse events in any of the patients.

CONCLUSIONS

Microvascular injury related to brown spider bites may culminate in ischemic nonhealing wounds even in a relatively young, healthy population. Hyperbaric oxygen therapy should be considered as a valuable therapeutic tool even months after the bite.

A multi-protease, multi-dissociation, bottom-up-to-top-down proteomic view of the Loxosceles intermedia venom

Venoms are a rich source for the discovery of molecules with biotechnological applications, but their analysis is challenging even for state-of-the-art proteomics. Here we report on a large-scale proteomic assessment of the venom of Loxosceles intermedia, the so-called brown spider. Venom was extracted from 200 spiders and fractioned into two aliquots relative to a 10 kDa cutoff mass. Each of these was further fractioned and digested with trypsin (4 h), trypsin (18 h), pepsin (18 h), and chymotrypsin (18 h), then analyzed by MudPIT on an LTQ-Orbitrap XL ETD mass spectrometer fragmenting precursors by CID, HCD, and ETD. Aliquots of undigested samples were also analyzed. Our experimental design allowed us to apply spectral networks, thus enabling us to obtain meta-contig assemblies, and consequently de novo sequencing of practically complete proteins, culminating in a deep proteome assessment of the venom. Data are available via ProteomeXchange, with identifier PXD005523.

Defining the complex phenotype of severe systemic loxoscelism using a large electronic health record cohort

Objective

Systemic loxoscelism is a rare illness resulting from the bite of the recluse spider and, in its most severe form, can lead to widespread hemolysis, coagulopathy, and death. We aim to describe the clinical features and outcomes of the largest known cohort of individuals with moderate to severe loxoscelism.

Methods

We performed a retrospective, cross sectional study from January 1, 1995, to December 31, 2015, at a tertiary-care academic medical center, to determine individuals with clinical records consistent with moderate to severe loxoscelism. Age-, sex-, and race-matched controls were compared. Demographics, clinical characteristics, laboratory measures, and outcomes of individuals with loxoscelism are described. Case and control groups were compared with descriptive statistics and phenome-wide association study (PheWAS).

Results

During the time period, 57 individuals were identified as having moderate to severe loxoscelism. Of these, only 33% had an antecedent spider bite documented. Median age of individuals diagnosed with moderate to severe loxoscelism was 14 years old (IQR 9.0–24.0 years). PheWAS confirmed associations of systemic loxoscelism with 29 other phenotypes, e.g., rash, hemolytic anemia, and sepsis. Hemoglobin level dropped an average of 3.1 g/dL over an average of 2.0 days (IQR 2.0–6.0). Lactate dehydrogenase and total bilirubin levels were on average over two times their upper limit of normal values. Eighteen individuals of 32 tested had a positive direct antiglobulin (Coombs’) test. Mortality was 3.5% (2/57 individuals).

Conclusion

Systemic loxoscelism is a rare but devastating process with only a minority of patients recalling the toxic exposure; hemolysis reaches a peak at 2 days after admission, with some cases taking more than a week before recovery. In endemic areas, suspicion for systemic loxoscelism should be high in individuals, especially children and younger adults, presenting with a cutaneous ulcer and hemolysis or coagulopathy, even in the absence of a bite exposure history.

Phospholipase D from Loxosceles laeta Spider Venom Induces IL-6, IL-8, CXCL1/GRO-α, and CCL2/MCP-1 Production in Human Skin Fibroblasts and Stimulates Monocytes Migration

Cutaneous loxoscelism envenomation by Loxosceles spiders is characterized by the development of a dermonecrotic lesion, strong inflammatory response, the production of pro-inflammatory mediators, and leukocyte migration to the bite site. The role of phospholipase D (PLD) from Loxosceles in the recruitment and migration of monocytes to the envenomation site has not yet been described. This study reports on the expression and production profiles of cytokines and chemokines in human skin fibroblasts treated with catalytically active and inactive recombinant PLDs from Loxosceles laeta (rLlPLD) and lipid inflammatory mediators ceramide 1-phosphate (C1P) and lysophosphatidic acid (LPA), and the evaluation of their roles in monocyte migration. Recombinant rLlPLD1 (active) and rLlPLD2 (inactive) isoforms induce interleukin (IL)-6, IL-8, CXCL1/GRO-α, and CCL2/monocyte chemoattractant protein-1 (MCP-1) expression and secretion in fibroblasts. Meanwhile, C1P and LPA only exhibited a minor effect on the expression and secretion of these cytokines and chemokines. Moreover, neutralization of both enzymes with anti-rLlPLD1 antibodies completely inhibited the secretion of these cytokines and chemokines. Importantly, conditioned media from fibroblasts, treated with rLlPLDs, stimulated the transmigration of THP-1 monocytes. Our data demonstrate the direct role of PLDs in chemotactic mediator synthesis for monocytes in human skin fibroblasts and indicate that inflammatory processes play an important role during loxoscelism.

Characteristics and Lethality of a Novel Recombinant Dermonecrotic Venom Phospholipase D from Hemiscorpius lepturus

Hemoscorpius lepturus is the most medically important scorpion in Iran. The clinical signs of H. lepturus envenomation are remarkably similar to those reported for brown spiders, including dermonecrosis, hematuria, renal failure and even death. The lethality and toxicity of brown spiders’ venom have been attributed to its phospholipase D activity. This study aims to identify a phospholipase D with possible lethality and dermonecrotic activity in H. lepturus venom. In this study, a cDNA library of the venom glands was generated by Illumina RNA sequencing. Phospholipase D (PLD) from H. lepturus was characterized according to its significant similarity with PLDs from brown spiders. The main chain designated as Hl-RecPLD1 (the first recombinant isoform of H. lepturus PLD) was cloned, expressed and purified. Sphingomyelinase, dermonecrotic and lethal activities were examined. Hl-PLD1 showed remarkable sequence similarity and structural homology with PLDs of brown spiders. The conformation of Hl-PLD1 was predicted as a “TIM beta/alpha-barrel”. The lethal dose 50 (LD₅₀) and dermonecrotic activities of Hl-RecPLD1 were determined as 3.1 µg/mouse and 0.7 cm² at 1 µg respectively. It is the first report indicating that a similar molecular evolutionary mechanism has occurred in both American brown spiders and this Iranian scorpion. In conclusion, Hl-RecPLD1 is a highly active phospholipase D, which would be considered as the lethal dermonecrotic toxin in H. lepturus venom.