The Natural Cell-Penetrating Peptide Crotamine Targets Tumor Tissue in Vivo and Triggers a Lethal Calcium-Dependent Pathway in Cultured Cells

Our goal was to demonstrate the in vivo tumor specific accumulation of crotamine, a natural peptide from the venom of the South American rattlesnake Crotalus durissus terrificus, which has been characterized by our group as a cell penetrating peptide with a high specificity for actively proliferating cells and with a concentration-dependent cytotoxic effect. Crotamine cytotoxicity has been shown to be dependent on the disruption of lysosomes and subsequent activation of intracellular proteases. In this work, we show that the cytotoxic effect of crotamine also involves rapid intracellular calcium release and loss of mitochondrial membrane potential as observed in real time by confocal microscopy. The intracellular calcium overload induced by crotamine was almost completely blocked by thapsigargin. Microfluorimetry assays confirmed the importance of internal organelles, such as lysosomes and the endoplasmic reticulum, as contributors for the intracellular calcium increase, as well as the extracellular medium. Finally, we demonstrate here that crotamine injected intraperitoneally can efficiently target remote subcutaneous tumors engrafted in nude mice, as demonstrated by a noninvasive optical imaging procedure that permits in vivo real-time monitoring of crotamine uptake into tumor tissue. Taken together, our data indicate that the cytotoxic peptide crotamine can be used potentially for a dual purpose: to target and detect growing tumor tissues and to selectively trigger tumor cell death.

N-glycome profiling of Bothrops jararaca newborn and adult venoms

Glycosylation is an important post-translational modification of snake venom proteins and contributes to venom proteome complexity. Many snake venom components are known to be glycosylated, however, very little is known about the carbohydrate structures present in venom glycoproteins. Previous studies showed that the ontogenetic shift in diet, from ectothermic prey in early life to endothermic prey in adulthood, and shift in animal size are associated with changes in the venom proteome of the snake Bothrops jararaca. In this study we explored the composition of the N-glycome released from newborn and adult B. jararaca venom proteins. We used an ion trap mass spectrometer (IT-MS) to disassemble glycan structures based on the use of several pathways of MS (MSn) and demonstrate the presence of some structural isomers in both newborn and adult venom B. jararaca N-glycans. The main N-glycans identified in both venoms are of the hybrid/complex type however some mannose-rich type structures were also detected. The N-glycan composition of newborn and adult venoms did not vary indicating that differences in the utilization of the N-glycosylation motif could be the explanation for the differences in the glycosylation levels indicated by the differential electrophoretic profiles previously reported for B. jararaca newborn and adult venoms. (C) 2011 Elsevier B.V. All rights reserved.

Crotamine Pharmacology Revisited: Novel Insights Based on the Inhibition of K-V Channels

Crotamine, a 5-kDa peptide, possesses a unique biological versatility. Not only has its cell-penetrating activity become of clinical interest but, moreover, its potential selective antitumor activity is of great pharmacological importance. In the past, several studies have attempted to elucidate the exact molecular target responsible for the crotamine-induced skeletal muscle spasm. The aim of this study was to investigate whether crotamine affects voltage-gated potassium (K-V) channels in an effort to explain its in vivo effects. Crotamine was studied on ion channel function using the two-electrode voltage clamp technique on 16 cloned ion channels (12 K-V channels and 4 Na-V channels), expressed in Xenopus laevis oocytes. Crotamine selectively inhibits K-V 1.1, K-V 1.2, and K-V 1.3 channels with an IC50 of similar to 300 nM, and the key amino acids responsible for this molecular interaction are suggested. Our results demonstrate for the first time that the symptoms, which are observed in the typical crotamine syndrome, may result from the inhibition of K-V channels. The ability of crotamine to inhibit the potassium current through K-V channels unravels it as the first snake peptide with the unique multifunctionality of cell-penetrating and antitumoral activity combined with K-V channel-inhibiting properties. This new property of crotamine might explain some experimental observations and opens new perspectives on pharmacological uses.

Crotoxin and phospholipases A(2) from Crotalus durissus terrificus showed antiviral activity against dengue and yellow fever viruses

Dengue is the most important arbovirus in the world with an estimated of 50 million dengue infections occurring annually and approximately 2.5 billion people living in dengue endemic countries. Yellow fever is a viral hemorrhagic fever with high mortality that is transmitted by mosquitoes. Effective vaccines against yellow fever have been available for almost 70 years and are responsible for a significant reduction of occurrences of the disease worldwide; however, approximately 200,000 cases of yellow fever still occur annually, principally in Africa. Therefore, it is a public health priority to develop antiviral agents for treatment of these virus infections. Crotalus durissus terrificus snake, a South American rattlesnake, presents venom with several biologically actives molecules. In this study, we evaluated the antiviral activity of crude venom and isolated toxins from Crotalus durissus terrificus and found that phospholipases A(2) showed a high inhibition of Yellow fever and dengue viruses in VERO E6 cells. (C) 2011 Elsevier Ltd. All rights reserved.

Crotoxin, a rattlesnake toxin, induces a long-lasting inhibitory effect on phagocytosis by neutrophils

Crotalus durissus terrificus snake venom (CdtV) has long-lasting anti-inflammatory properties and inhibits the spreading and phagocytic activity of macrophages. Crotoxin (CTX), the main component of CdtV, is responsible for these effects. Considering the role of neutrophils in the inflammatory response and the lack of information about the effect of CdtV on neutrophils, the aim of this study was to investigate the effect of CdtV and CTX on two functions of neutrophils, namely phagocytosis and production of reactive oxygen species, and on the intracellular signaling involved in phagocytosis, particularly on tyrosine phosphorylation and rearrangements of the actin cytoskeleton. Our results showed that the incubation of neutrophils with CdtV or CTX, at different concentrations, or the subcutaneous injection of CdtV or CTX in rats two hours or one, four or 14 days before or one hour after the induction of inflammation inhibited the phagocytic activity of neutrophils. Furthermore, these in vitro and in vivo effects were associated with CdtV and CTX inhibition of tyrosine phosphorylation and consequently actin polymerization. Despite the inhibitory effect on phagocytosis, this study demonstrated that CdtV and CTX did not alter the production of the main reactive oxygen species. Therefore, this study characterized, for the first time, the actions of CdtV on neutrophils and demonstrated that CTX induces a long-lasting inhibition of tyrosine phosphorylation and consequently phagocytosis. We suggest that CTX represents a potential natural product in controlling inflammatory diseases, since a single dose exerts a long-lasting effect on intracellular signaling involved in phagocytosis by neutrophils.

IL-5 and IL-17A are critical for the chronic IgE response and differentiation of long-lived antibody-secreting cells in inflamed tissues

Prolonged survival of long-lived antibody-secreting cells in the BM has been implicated as a key component of long-term humoral immunity. The current study was designed to uncover the extrinsic signals required for the generation and maintenance of ASC in several niches (peritoneum, spleen and bone-marrow). Our results show that protein mixture of the Thalassophryne nattereri venom induced a chronic Th2 humoral response that is characterized by splenic hyperplasia with GC formation and venom retention by follicular DCs. Retention of B1a in the BM were observed. In the late phase (120 d) of chronic venom-response the largest pool of ASC into the peritoneal cavity consisted of B220(neg)CD43(high) phenotype; the largest pool of ASC into spleen was constituted by B220 positive cells (B220(high) and B220(low)), whereas the largest pool of ASC into in the BM was constituted by the B220(high)CD43(low) phenotype; and finally, terminally differentiated cells (B220(neg)CD43(high)) were only maintained in the inflamed peritoneal cavity in late phase. After 120 d a sustained production of cytokines (KC, IL-5, TNF-alpha, IL-6, IL-17A and IL-23) and leukocytes recruitment (eosinophils, mast cells, and neutrophils) were induced. IL-5- and IL-17A-producing CD4+ CD44+ CD40L+ Ly6C+ effector memory T cells were also observed in peritoneal cavity. Finally, treatment of venom-mice with anti-IL-5- and anti-IL17A-neutralizing mAbs abolished the synthesis of specific IgE, without modifying the splenic hyperplasia or GC formation. In addition, IL-5 and IL-17A negatively regulated the expansion of B1a in peritoneal cavity and BM, and promoted the differentiation of these cells in spleen. And more, IL-5 and IL-17A are sufficient for the generation of ASC B220(neg) in the peritoneal cavity and negatively regulate the number of ASC B220(Pos), confirming that the hierarchical process of ASC differentiation triggered by venom needs the signal derived from IL-5 and IL-17A. (C) 2012 Elsevier Ltd. All rights reserved.

Influence of the Bilayer Composition on the Binding and Membrane Disrupting Effect of Polybia-MP1, an Antimicrobial Mastoparan Peptide with Leukemic T-Lymphocyte Cell Selectivity

This study shows that MP-1, a peptide from the venom of the Polybia paulista wasp, is more toxic to human leukemic T-lymphocytes than to human primary lymphocytes. By using model membranes and electrophysiology measurements to investigate the molecular mechanisms underlying this selective action, the porelike activity of MP-1 was identified with several bilayer compositions. The highest average conductance was found in bilayers formed by phosphatidylcholine or a mixture of phosphatidylcholine and phosphatidylserine (70:30). The presence of cholesterol or cardiolipin substantially decreases the MP-1 pore activity, suggesting that the membrane fluidity influences the mechanism of selective toxicity. The determination of partition coefficients from the anisotropy of Tip indicated higher coefficients for the anionic bilayers. The partition coefficients were found to be 1 order of magnitude smaller when the bilayers contain cholesterol or a mixture of cholesterol and sphingomyelin. The blue shift fluorescence, anisotropy values, and Stern-Volmer constants are indications of a deeper penetration of MP-1 into anionic bilayers than into zwitterionic bilayers. Our results indicate that MP-1 prefers to target leukemic cell membranes, and its toxicity is probably related to the induction of necrosis and not to DNA fragmentation. This mode of action can be interpreted considering a number of bilayer properties like fluidity, lipid charge, and domain formation. Cholesterol-containing bilayers are less fluid and less charged and have a tendency to form domains. In comparison to healthy cells, leukemic T-lymphocyte membranes are deprived of this lipid, resulting in decreased peptide binding and lower conductance. We showed that the higher content of anionic lipids increases the level of binding of the peptide to bilayers. Additionally, the absence of cholesterol resulted in enhanced pore activity. These findings may drive the selective toxicity of MP-1 to Jurkat cells.

A bradykinin-potentiating peptide (BPP-10c) from Bothrops jararaca induces changes in seminiferous tubules

Abstract: Background: The testis-specific isoform of angiotensin-converting enzyme (tACE) is exclusively expressed in germ cells during spermatogenesis. Although the exact role of tACE in male fertility is unknown, it clearly plays a critical function in spermatogenesis. The dipeptidase domain of tACE is identical to the C-terminal catalytic domain of somatic ACE (sACE). Bradykinin potentiating peptides (BPPs) from snake venoms are the first natural sACE inhibitors described and their structure–activity relationship studies were the basis for the development of antihypertensive drugs such as captopril. In recent years, it has been showed that a number of BPPs – including BPP-10c – are able to distinguish between the N- and C-active sites of sACE, what is not applicable to captopril. Considering the similarity between tACE and sACE (and since BPPs are able to distinguish between the two active sites of sACE), the effects of the BPP-10c and captopril on the structure and function of the seminiferous epithelium were characterized in the present study. BPP-10c and captopril were administered in male Swiss mice by intraperitoneal injection (4.7 μmol/kg for 15 days) and histological sections of testes were analyzed. Classification of seminiferous tubules and stage analysis were carried out for quantitative evaluation of germ cells of the seminiferous epithelium. The blood-testis barrier (BTB) permeability and distribution of claudin-1 in the seminiferous epithelium were analyzed by hypertonic fixative method and immunohistochemical analyses of testes, respectively. Results: The morphology of seminiferous tubules from animals treated with BPP-10c showed an intense disruption of the epithelium, presence of atypical multinucleated cells in the lumen and degenerated germ cells in the adluminal compartment. BPP-10c led to an increase in the number of round spermatids and total support capacity of Sertoli cell in stages I, V, VII/VIII of the seminiferous epithelium cycle, without affecting BTB permeability and the distribution of claudin-1 in the seminiferous epithelium. Interestingly, no morphological or morphometric alterations were observed in animals treated with captopril. Conclusions: The major finding of the present study was that BPP-10c, and not captopril, modifies spermatogenesis by causing hyperplasia of round spermatids in stages I, V, and VII/VIII of the spermatogenic cycle.

Involvement of formyl peptide receptors in the stimulatory effect of crotoxin on macrophages co-cultivated with tumour cells

Crotoxin (CTX) is the main neurotoxic component of Crotalus durissus terrificus snake venom. It inhibits tumour growth and modulates the function of macrophages, which are essential cells in the tumour microenvironment. The present study investigated the effect of CTX on the secretory activity of monocultured macrophages and macrophages co-cultivated with LLC-WRC 256 cells. The effect of the macrophage secretory activities on tumour cell proliferation was also evaluated. Macrophages pre-treated with CTX (0.3 μg/mL) for 2 h were co-cultivated with LLC-WRC 256 cells, and the secretory activity of the macrophages was determined after 12, 24 and 48 h. The co-cultivation of CTX-treated macrophages with the tumour cells caused a 20% reduction in tumour cell proliferation. The production of both H2O2 and NO was increased by 41% and 29% after 24 or 48 h of co-cultivation, respectively, compared to the values for the co-cultures of macrophages of control. The level of secreted IL-1β increased by 3.7- and 3.2-fold after 12 h and 24 h of co-cultivation, respectively. Moreover, an increased level of LXA4 (25%) was observed after 24 h of co-cultivation, and a 2.3- and 2.1-fold increased level of 15-epi-LXA4 was observed after 24 h and 48 h, respectively. Boc-2, a selective antagonist of formyl peptide receptors, blocked both the stimulatory effect of CTX on the macrophage secretory activity and the inhibitory effect of these cells on tumour cell proliferation. Taken together, these results indicate that CTX enhanced the secretory activity of macrophages, which may contribute to the antitumour activity of these cells, and that activation of formyl peptide receptors appears to play a major role in this effect.

Investigations on the G-protein involved in Cnidarian phototransduction

This study aimed to investigate which genes Cnidaria use for photoreception and test whether Gi alpha subunit protein is involved in the phototransduction cascade, giving additional tools to investigate light-mediated behaviors, as nematocyte firing. Here, I engineered an opsin gene promoter construct useful to test whether nematocyte sensory cells express opsin gene. By determining the expression of one of the unique EST opsin genes of the eyeless hydrozoan Hydra magnipapillata genome in nematocyte sensory cells, we will be able to investigate whether light modulation is an ancestral feature in Cnidaria, and whether regulation of nematocyte discharge by opsin-mediated phototransduction predated this pathway’s function in cnidarian eyes. Nematocytes, the cnidarians stinging cells, discharge nematocysts to capture prey. As nematocysts are energetically expensive, the discharge is tightly regulated and occurs after proper chemical and mechanical stimulation. Cnidarians are also known to display a rich corpus of photobehaviors, which are often associated with activities that involve nematocytes. Previous experiments on nematocyst firing modulation show that light decreases nematocyte firing. This study contributed to confirm that bright light decreases the tendency for nematocytes to discharge in Haliplanella luciae. Similar findings in cubozoan and hydrozoan lead us to believe that light modulation of cnidocytes may be an ancestral feature of Cnidaria. Experimentally, I found no evidence that pertussis toxin, a Gi alpha subunit protein inhibitor, ablates Hydra magnipapillata photobehaviour, preliminary suggesting that Gi alpha subunit protein is not involved in photoresponse. I found no significant association between pertussis toxin and nematocyte firing in Haliplanella luciae both in conditions of dim and bright light, suggesting that Gi alpha subunit protein is not involved in photoresponse. We have preliminary evidence for a prevalence of photoreception over chemoreception, tending toward conditions of bright light. This finding may suggest the involvement of a Gs alpha subunit protein in Haliplanella luciae phototransduction pathway. While nematocyte chemo- and mechano-sensitivity have been extensively studied, further research is necessary to better understand what an ancestral phototransduction cascade looked like, and how opsin-based phototransduction acts to regulate nematocyte discharge.

Drosophila melanogaster as a model to study host-parasitoid interactions: the case of the polydnaviral protein TnBVANK1

Parasitic wasps attack a number of insect species on which they feed, either externally or internally. This requires very effective strategies for suppressing the immune response and a finely tuned interference with the host physiology that is co-opted for the developing parasitoid progeny. The wealth of physiological host alterations is mediated by virulence factors encoded by the wasp or, in some cases, by polydnaviruses (PDVs), unique viral symbionts injected into the host at oviposition along with the egg, venom and ovarian secretions. PDVs are among the most powerful immunosuppressors in nature, targeting insect defense barriers at different levels. During my PhD research program I have used Drosophila melanogaster as a model to expand the functional analysis of virulence factors encoded by PDV focusing on the molecular processes underlying the disruption of the host endocrine system. I focused my research on a member of the ankyrin (ank) gene family, an immunosuppressant found in bracovirus, which associates with the parasitic wasp Toxoneuron nigriceps. I found that ankyrin disrupts ecdysone biosynthesis by impairing the vesicular traffic of ecdysteroid precursors in the cells of the prothoracic gland and results in developmental arrest.

Flagellin:allergen fusion proteins as novel vaccines for the treatment of severe type I allergies

Over the last decades the prevalence of food allergies has continually increased on a world wide scale. While there are effective treatments available for bee and wasp venom allergic patients, there is currently no established therapy for the treatment of severe food allergies. Aim of the project was to genetically fuse different food allergens with the immune modulating Toll-like receptor 5 (TLR5)-ligand flagellin and to test these constructs for their immune modulatory capacities both in vitro and in vivo. Chicken ovalbumin (Ova) as model antigen, Pru p 3, and Ara h 2 the respective major allergens from peach and peanut were used as allergens. The potential vaccine candidates were characterized by protein biochemical methods (purity, folding, endotoxin contaminations). Moreover, their immune modulating effects on cell culture lines (TLR5-receptor activation) and primary mouse immune cells (myeloid and plasmacytoid dendritic cells) were investigated. Additionally, the prophylactic and therapeutic use of the flagellin Ova fusion protein (rflaA:Ova) were investigated in a mouse model of intestinal allergy. In myeloid dendritic cells (mDC) stimulation with the fusion proteins led to a strong cell activation and cytokine secretion. Here, the fusion proteins proved to be a much stronger stimulus than the equimolar amount of both proteins provided alone or as a mixture. Noteworthy, stimulation with rflaA:Ova induced the secretion of the anti-inflammatory cytokine IL-10 from mDC. In co-culture experiments this IL-10 secretion suppressed the Ova-induced secretion of Th1 and Th2 cytokines from Ova-specific CD4 T cells. Using MyD88-deficient mDC this repression of cytokine secretion was shown to be TLR-dependent. Finally, the potency of the rflaA:Ova construct was investigated in a mouse model of Ova-induced intestinal allergy. In a prophylactic vaccination approach rflaA:Ova was shown to prevent the establishment of the intestinal allergy and all associated symptoms (weight loss, temperature drop, soft faeces). This fusion protein-mediated protection was accompanied by a reduced T cell activation, and reduced Th2 cytokines in intestinal homogenates. These effects were paralleled by a strong induction of Ova-specific IgG2a antibodies in rflaA:Ova-vaccinated sera, while Ova-specific IgE antibody production was significantly reduced. Therapeutic vaccination with rflaA:Ova reduced allergic symptoms and T cell activation but did not influence weight loss and antibody production. In all in vivo experiments vaccination with both proteins either provided alone or as a mixture did not have comparable effects. Future experiments aim at elucidating the mechanism and further optimization of the therapeutic vaccination approach. The results presented in this thesis demonstrate, that fusion proteins containing flagellin have strong immune modulatory capacities both in vitro and in vivo. Therefore, such constructs are promising vaccine candidates for the therapy of type I allergies.

Über den Einfluss von Melittin auf die Funktion membranständiger Proteasen der ADAM-Familie

Melittin, Hauptbestandteil des Bienengifts, ist ein kationisches Peptid, welches in der Lage ist, die biophysikalischen Eigenschaften der Zellmembran zu beeinflussen. Melittin werden unter anderem auch entzündungshemmende, schmerzlindernde, anti-rheumatische und anti-arthritische Wirkungen zugeschrieben. rnIn dieser Arbeit wurde nachgewiesen, dass Melittin die Proteolyse von ADAM10- und ADAM17-Substraten in verschiedenen Zellen stimuliert. Durch das Sheddingvon TGF-α wurde in HaCaT-Keratinozyten eine Transaktivierung des EGF-Rezeptors und eine daraus resultierende Phosphorylierung der Kinase ERK1/2 beobachtet. Die durch Melittin gesteigerte Aktivität der ADAMs ist calciumunabhängig und wird nicht durch Änderungen in der Membranfluidität verursacht. Eine Beteiligung der P2-Rezeptoren an der Melittin-induzierten ADAM-Aktivierung konnte sowohl durch Inhibition der Rezeptoren als auch durch Transfektion von HEK-Zellen mit dem P2X7-Rezeptor nachgewiesen werden. In diesen wurde nach der Behandlung mit Melittin eine Phosphorylierung von ERK1/2 beobachtet, welche durch ATPasen und P2-Rezeptor-Inhibitoren unterdrückt werden konnte. rnMit Hilfe des Kaninchenerythrozyten-Modells wurde nachgewiesen, dass eine Translokation von Phosphatidylserin von der Innen- zur Außenseite der Membran unmittelbar mit einer erhöhten ADAM-Aktivität korreliert. Sowohl durch Aktivierung des P2X7-Rezeptors als auch durch die Behandlung der Zellen mit dem Ionophor A23187 konnte ein Phosphatidylserin-Flip induziert werden. Dieser Flip führte zu einer erhöhten Aktivität von ADAM10, die durch eine gesteigerte Hämolyse und Spaltung von pVCC nachgewiesen werden konnte. Wurde der Phosphatidylserin-Flip durch Inhibitoren des P2X7-Rezeptors bzw. die Chelation von Ca2+ und Hemmung der Ionenfluxe unterdrückt, blieb auch die erhöhte ADAM-Aktivität aus. Wurde dagegen der Phosphatidylserin-Flip erst induziert und nachträglich die Inhibition des P2X7-Rezeptors bzw. die Chelation von Ca2+ und Hemmung der Ionenfluxe durchgeführt, zeigte dies keine Inhibition der ADAM-Aktivität.rnZusammenfassend zeigen diese Ergebnisse, dass eine Exposition von Phosphatidylserin auf der Außenseite der Membran in einem kausalen Zusammenhang mit einer gesteigerten ADAM-Aktivität steht.rn

Screening for lupus anticoagulant: improving the performance of the lupus-sensitive PTT-LA

Introduction: The aim of the present work was to verify whether calculating a ratio between clotting times obtained with the sensitive PTT-LA and a less sensitive activated partial thromboplastin time (aPTT)-reagent may represent a valuable aPTT-based screening strategy for lupus anticoagulants (LA). Methods: For the pilot study, plasma samples from normal subjects (n = 15) and from patients with LA (n = 10), therapeutic anticoagulation with vitamin K-antagonists (VKA) (n = 15) or unfractionated heparin (n = 15), coagulation factors deficiency (n = 16), and inhibitory antibodies against factor VIII or IX (n = 11) were studied. For the evaluation study, 1553 consecutive plasma samples from nonanticoagulated patients investigated for LA between January 2005 and December 2007 at our institution were studied. Following screening strategies were employed: Pathromtin-SL (aPTT-SL), PTT-LA (aPTT-LA), ratio aPTT-LA/aPTT-SL (aPTT-ratio), and Russell's viper venom (RVV) based LA-Check. LA positive samples were identified by mixing studies and diluted RVV confirmation test (LA-Check/LA-Sure). Results: Pilot study: All screening strategies had a 100% sensitivity, and the aPTT-ratio reached the highest specificity (82%; 95%CI: 74-90%). Within the evaluation study, following sensitivities for LA screening were observed: aPTT-SL 59.0% (95%CI: 57-61%), aPTT-LA 82.1% (95%CI: 80-84%), aPTT-ratio 92.3% (95%CI: 91-94), and LA-Check 83.3% (95%CI: 82-85%). Conclusion: Calculating a ratio between the LA-sensitive PTT-LA and the less sensitive Pathromtin-SL improves the performance of the PTT-LA itself and represents a simple and sensitive aPTT-based integrated strategy for LA screening.

Purification, cDNA structure and biological significance of a single insulin-like growth factor-binding domain protein (SIBD-1) identified in the hemocytes of the spider Cupiennius salei

Cupiennius salei single insulin-like growth factor-binding domain protein (SIBD-1), which exhibits an IGFBP N-terminal domain-like profile, was identified in the hemocytes of the spider C. salei. SIBD-1 was purified by RP-HPLC and the sequence determined by a combination of Edman degradation and 5'-3'- RACE PCR. The peptide (8676.08 Da) is composed of 78 amino acids, contains six intrachain disulphide bridges and carries a modified Thr residue at position 2. SIBD-1 mRNA expression was detected by quantitative real-time PCR mainly in hemocytes, but also in the subesophageal nerve mass and muscle. After infection, the SIBD-1 content in the hemocytes decreases and, simultaneously, the temporal SIBD-1 expression seems to be down-regulated. Two further peptides, SIBD-2 and IGFBP-rP1, also exhibiting IGFBP N-terminal domain variants with unknown functions, were identified on cDNA level in spider hemocytes and venom glands. We conclude that SIBD-1 may play an important role in the immune system of spiders.