Food-Borne Biotoxin Neutralization in Vivo by Nanobodies: Current Status and Prospects

Food-borne biotoxins from microbes, plants, or animals contaminate unclean, spoiled, and rotten foods, posing significant health risks. Neutralizing such toxins is vital for human health, especially after food poisoning. Nanobodies (Nbs), a type of single-domain antibodies derived from the genetic cloning of a variable domain of heavy chain antibodies (VHHs) in camels, offer unique advantages in toxin neutralization. Their small size, high stability, and precise binding enable effective neutralization. The use of Nbs in neutralizing food-borne biotoxins offers numerous benefits, and their genetic malleability allows tailored optimization for diverse toxins. As nanotechnology continues to evolve and improve, Nbs are poised to become increasingly efficient and safer tools for toxin neutralization, playing a pivotal role in safeguarding human health and environmental safety. This review not only highlights the efficacy of these agents in neutralizing toxins but also proposes innovative solutions to address their current challenges. It lays a solid foundation for their further development in this crucial field and propels their commercial application, thereby contributing significantly to advancements in this domain.

Viperin, an IFN-Stimulated Protein, Delays Rotavirus Release by Inhibiting Non-Structural Protein 4 (NSP4)-Induced Intrinsic Apoptosis

Viral infections lead to expeditious activation of the host's innate immune responses, most importantly the interferon (IFN) response, which manifests a network of interferon-stimulated genes (ISGs) that constrain escalating virus replication by fashioning an ill-disposed environment. Interestingly, most viruses, including rotavirus, have evolved numerous strategies to evade or subvert host immune responses to establish successful infection. Several studies have documented the induction of ISGs during rotavirus infection. In this study, we evaluated the induction and antiviral potential of viperin, an ISG, during rotavirus infection. We observed that rotavirus infection, in a stain independent manner, resulted in progressive upregulation of viperin at increasing time points post-infection. Knockdown of viperin had no significant consequence on the production of total infectious virus particles. Interestingly, substantial escalation in progeny virus release was observed upon viperin knockdown, suggesting the antagonistic role of viperin in rotavirus release. Subsequent studies unveiled that RV-NSP4 triggered relocalization of viperin from the ER, the normal residence of viperin, to mitochondria during infection. Furthermore, mitochondrial translocation of NSP4 was found to be impeded by viperin, leading to abridged cytosolic release of Cyt c and subsequent inhibition of intrinsic apoptosis. Additionally, co-immunoprecipitation studies revealed that viperin associated with NSP4 through regions including both its radical SAM domain and its C-terminal domain. Collectively, the present study demonstrated the role of viperin in restricting rotavirus egress from infected host cells by modulating NSP4 mediated apoptosis, highlighting a novel mechanism behind viperin's antiviral action in addition to the intricacy of viperin-virus interaction.

Sites of vulnerability on ricin B chain revealed through epitope mapping of toxin-neutralizing monoclonal antibodies

Ricin toxin's B subunit (RTB) is a multifunctional galactose (Gal)-/N-acetylgalactosamine (GalNac)-specific lectin that promotes uptake and intracellular trafficking of ricin's ribosome-inactivating subunit (RTA) into mammalian cells. Structurally, RTB consists of two globular domains (RTB-D1, RTB-D2), each divided into three homologous sub-domains (α, β, γ). The two carbohydrate recognition domains (CRDs) are situated on opposite sides of RTB (sub-domains 1α and 2γ) and function non-cooperatively. Previous studies have revealed two distinct classes of toxin-neutralizing, anti-RTB monoclonal antibodies (mAbs). Type I mAbs, exemplified by SylH3, inhibit (~90%) toxin attachment to cell surfaces, while type II mAbs, epitomized by 24B11, interfere with intracellular toxin transport between the plasma membrane and the trans-Golgi network (TGN). Localizing the epitopes recognized by these two classes of mAbs has proven difficult, in part because of RTB's duplicative structure. To circumvent this problem, RTB-D1 and RTB-D2 were expressed as pIII fusion proteins on the surface of filamentous phage M13 and subsequently used as "bait" in mAb capture assays. We found that SylH3 captured RTB-D1 (but not RTB-D2) in a dose-dependent manner, while 24B11 captured RTB-D2 (but not RTB-D1) in a dose-dependent manner. We confirmed these domain assignments by competition studies with an additional 8 RTB-specific mAbs along with a dozen a single chain antibodies (VHHs). Collectively, these results demonstrate that type I and type II mAbs segregate on the basis of domain specificity and suggest that RTB's two domains may contribute to distinct steps in the intoxication pathway.

An Electrochemical Fiveplex Biochip Assay Based on Anti-Idiotypic Antibodies for Fast On-Site Detection of Bioterrorism Relevant Low Molecular Weight Toxins

Modern threats of bioterrorism force the need for multiple detection of biothreat agents to determine the presence or absence of such agents in suspicious samples. Here, we present a rapid electrochemical fiveplex biochip screening assay for detection of the bioterrorism relevant low molecular weight toxins saxitoxin, microcystin-LR, T-2 toxin, roridin A and aflatoxin B1 relying on anti-idiotypic antibodies as epitope-mimicking reagents. The proposed method avoids the use of potentially harmful toxin-protein conjugates usually mandatory for competitive immunoassays. The biochip is processed and analyzed on the automated and portable detection platform pBDi within 13.4 min. The fiveplex biochip assay revealed toxin group specificity to multiple congeners. Limits of detection were 1.2 ng/mL, 1.5 ng/mL, 0.4 ng/mL, 0.5 ng/mL and 0.6 ng/mL for saxitoxin, microcystin-LR, T-2 toxin, roridin A or aflatoxin B1, respectively. The robustness of the fiveplex biochip for real samples was demonstrated by detecting saxitoxin, microcystin-LR, HT-2 toxin, roridin A and aflatoxin B1 in contaminated human blood serum without elaborate sample preparation. Recovery rates were between 52–115% covering a wide concentration range. Thus, the developed robust fiveplex biochip assay can be used on-site to quickly detect one or multiple low molecular weight toxins in a single run.

The Role of Functional Amyloids in Bacterial Virulence

Amyloid fibrils are best known as a product of human and animal protein misfolding disorders, where amyloid formation is associated with cytotoxicity and disease. It is now evident that for some proteins, the amyloid state constitutes the native structure and serves a functional role. These functional amyloids are proving widespread in bacteria and fungi, fulfilling diverse functions as structural components in biofilms or spore coats, as toxins and surface-active fibers, as epigenetic material, peptide reservoirs or adhesins mediating binding to and internalization into host cells. In this review, we will focus on the role of functional amyloids in bacterial pathogenesis. The role of functional amyloids as virulence factor is diverse but mostly indirect. Nevertheless, functional amyloid pathways deserve consideration for the acute and long-term effects of the infectious disease process and may form valid antimicrobial targets.

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Functional amyloids are widespread in bacteria, pathogenic and non-pathogenic.

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Bacterial biofilms most commonly function as structural support in the extracellular matrix of biofilms or spore coats, and in cell–cell and cell-surface adherence.

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The amyloid state can be the sole structured and functional state, or can be facultative, as a secondary state to folded monomeric subunits.

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Bacterial amyloids can enhance virulence by increasing persistence, cell adherence and invasion, intracellular survival, and pathogen spread by increased environmental survival.

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Bacterial amyloids may indirectly inflict disease by triggering inflammation, contact phase activation and possibly induce or aggravate human pathological aggregation disorders.

Environmental risk factors for type 1 diabetes

The incidence of type 1 diabetes has risen considerably in the past 30 years due to changes in the environment that have been only partially identified. In this Series paper, we critically discuss candidate triggers of islet autoimmunity and factors thought to promote progression from autoimmunity to overt type 1 diabetes. We revisit previously proposed hypotheses to explain the growth in the incidence of type 1 diabetes in light of current data. Finally, we suggest a unified model in which immune tolerance to β cells can be broken by several environmental exposures that induce generation of hybrid peptides acting as neoautoantigens.

BclA and toxin antigens augment each other to protect NMRI mice from lethal Bacillus anthracis challenge

While proving highly effective in controlling Anthrax in farm animals all over the world currently attenuated live anthrax vaccines employed in a veterinary context suffer from drawbacks such as residual virulence, short term protection, variation in quality and, most importantly, lack of efficacy if administered simultaneously with antibiotics. These limitations have stimulated the development of non-living component vaccines which induce a broad spectrum immune response capable of targeting both toxaemia (as in the case of PA based vaccines) and bacteraemia. To contribute to this several new approaches were tested in outbred NMRI mice for antibody titres and protectiveness. Plasmids encoding a recombinant toxin derived fusion peptide and a spore surface derived peptide were tested as DNA-vaccines in comparison to their protein counterparts utilising two adjuvant approaches and two DNA-vector backbones. The combination of two plasmids encoding LFD1PAD4-mIPS1 and TPA-BclAD1D3-LAMP1, when delivered by GeneGun, protected 90% of the animals against a lethal challenge with 25LD50 spores of the Ames strain of Bacillus anthracis. Single applications of either antigen component showed significantly lower protection rates, indicating the beneficial interaction between anti-spore and anti-toxin components for an acellular vaccine formulation.

Mechanistic insights into the neutralization of cytotoxic abrin by the monoclonal antibody D6F10

Abrin, an A/B toxin obtained from the Abrus precatorius plant is extremely toxic and a potential bio-warfare agent. Till date there is no antidote or vaccine available against this toxin. The only known neutralizing monoclonal antibody against abrin, namely D6F10, has been shown to rescue the toxicity of abrin in cells as well as in mice. The present study focuses on mapping the epitopic region to understand the mechanism of neutralization of abrin by the antibody D6F10. Truncation and mutational analysis of abrin A chain revealed that the amino acids 74-123 of abrin A chain contain the core epitope and the residues Thr112, Gly114 and Arg118 are crucial for binding of the antibody. In silico analysis of the position of the mapped epitope indicated that it is present close to the active site cleft of abrin A chain. Thus, binding of the antibody near the active site blocks the enzymatic activity of abrin A chain, thereby rescuing inhibition of protein synthesis by the toxin in vitro. At 1∶10 molar concentration of abrin:antibody, the antibody D6F10 rescued cells from abrin-mediated inhibition of protein synthesis but did not prevent cell attachment of abrin. Further, internalization of the antibody bound to abrin was observed in cells by confocal microscopy. This is a novel finding which suggests that the antibody might function intracellularly and possibly explains the rescue of abrin's toxicity by the antibody in whole cells and animals. To our knowledge, this study is the first report on a neutralizing epitope for abrin and provides mechanistic insights into the poorly understood mode of action of anti-A chain antibodies against several toxins including ricin.

Antibody to ricin a chain hinders intracellular routing of toxin and protects cells even after toxin has been internalized

Background

Mechanisms of antibody-mediated neutralization are of much interest. For plant and bacterial A-B toxins, A chain mediates toxicity and B chain binds target cells. It is generally accepted and taught that antibody (Ab) neutralizes by preventing toxin binding to cells. Yet for some toxins, ricin included, anti-A chain Abs afford greater protection than anti-B. The mechanism(s) whereby Abs to the A chain neutralize toxins are not understood.

Methodology/Principal Findings

We use quantitative confocal imaging, neutralization assays, and other techniques to study how anti-A chain Abs function to protect cells. Without Ab, ricin enters cells and penetrates to the endoplasmic reticulum within 15 min. Within 45–60 min, ricin entering and being expelled from cells reaches equilibrium. These results are consistent with previous observations, and support the validity of our novel methodology. The addition of neutralizing Ab causes ricin accumulation at the cell surface, delays internalization, and postpones retrograde transport of ricin. Ab binds ricin for >6hr as they traffic together through the cell. Ab protects cells even when administered hours after exposure.

Conclusions/Key Findings

We demonstrate the dynamic nature of the interaction between the host cell and toxin, and how Ab can alter the balance in favor of the cell. Ab blocks ricin’s entry into cells, hinders its intracellular routing, and can protect even after ricin is present in the target organelle, providing evidence that the major site of neutralization is intracellular. These data add toxins to the list of pathogenic agents that can be neutralized intracellularly and explain the in vivo efficacy of delayed administration of anti-toxin Abs. The results encourage the use of post-exposure passive Ab therapy, and show the importance of the A chain as a target of Abs.

Increased immunogenicity and protective efficacy of influenza M2e fused to a tetramerizing protein

The ectodomain of the matrix 2 protein (M2e) of influenza A virus represents an attractive target for developing a universal influenza A vaccine, with its sequence being highly conserved amongst human variants of this virus. With the aim of targeting conformational epitopes presumably shared by diverse influenza A viruses, a vaccine (M2e-NSP4) was constructed linking M2e (in its consensus sequence) to the rotavirus fragment NSP4_98–135; due to its coiled-coil region this fragment is known to form tetramers in aqueous solution and in this manner we hoped to mimick the natural configuration of M2e as presented in membranes. M2e-NSP4 was then evaluated side-by-side with synthetic M2e peptide for its immunogenicity and protective efficacy in a murine influenza challenge model. Here we demonstrate that M2e fused to the tetramerizing protein induces an accelerated, augmented and more broadly reactive antibody response than does M2e peptide as measured in two different assays. Most importantly, vaccination with M2e-NSP4 caused a significant decrease in lung virus load early after challenge with influenza A virus and maintained its efficacy against a lethal challenge even at very low vaccine doses. Based on the results presented in this study M2e-NSP4 merits further investigation as a candidate for or as a component of a universal influenza A vaccine.

Monoclonal antibodies and toxins--a perspective on function and isotype

Antibody therapy remains the only effective treatment for toxin-mediated diseases. The development of hybridoma technology has allowed the isolation of monoclonal antibodies (mAbs) with high specificity and defined properties, and numerous mAbs have been purified and characterized for their protective efficacy against different toxins. This review summarizes the mAb studies for 6 toxins—Shiga toxin, pertussis toxin, anthrax toxin, ricin toxin, botulinum toxin, and Staphylococcal enterotoxin B (SEB)—and analyzes the prevalence of mAb functions and their isotypes. Here we show that most toxin-binding mAbs resulted from immunization are non-protective and that mAbs with potential therapeutic use are preferably characterized. Various common practices and caveats of protection studies are discussed, with the goal of providing insights for the design of future research on antibody-toxin interactions.

Premolis semirufa (Walker, 1856) envenomation, disease affecting rubber tappers of the Amazon: searching for caterpillar-bristles toxic components

BACKGROUND

The caterpillar of the moth Premolis semirufa (Lepidoptera: Arctiidae), commonly named Pararama, is endemic of the Amazon basin. Accidental contact with these caterpillar bristles causes local symptoms such as intense heat, pain, edema and itching which last for three to seven days; however, after multiples contacts, it may induce joint-space narrowing and bone alteration, as well as degeneration of the articular cartilage and immobilization of the affected joints. Specific treatment for this disease does not exist, but corticosteroids are frequently administered. Despite of the public health hazard of Premolis semirufa caterpillar poisoning, little is known about the nature of the toxic components involved in the induction of the pathology.

METHODOLOGY/PRINCIPAL FINDINGS

Here we have investigated the biological and immunochemical characteristics of the caterpillar's bristles components. Analysis of the bristles extract in in vitro assays revealed the presence of proteolytic and hyaluronidase activities but no phospholipase A(2) activity. In vivo, it was observed that the bristles extract is not lethal but can induce an intense inflammatory process, characterized by the presence of neutrophils in the paw tissues of injected mice. Furthermore, the bristles components stimulated an intense and specific antibody response but autoantibodies such as anti-DNA or anti-collagen type II were not detected.

CONCLUSION

The results suggest that Premolis semirufa caterpillar bristles secretion contains a mixture of different enzymes that may act together in the generation and development of the clinical manifestations of the Pararama envenomation. Moreover, the high immunogenicity of the caterpillar bristles components, as shown by the generation of high antibody titers, may also contribute to the induction and establishment of the inflammatory disease.

Biotechnological applications of recombinant single-domain antibody fragments

BACKGROUND

Single-domain antibody fragments possess structural features, such as a small dimension, an elevated stability, and the singularity of recognizing epitopes non-accessible for conventional antibodies that make them interesting for several research and biotechnological applications.

RESULTS

The discovery of the single-domain antibody's potentials has stimulated their use in an increasing variety of fields. The rapid accumulation of articles describing new applications and further developments of established approaches has made it, therefore, necessary to update the previous reviews with a new and more complete summary of the topic.

CONCLUSIONS

Beside the necessary task of updating, this work analyses in detail some applicative aspects of the single-domain antibodies that have been overseen in the past, such as their efficacy in affinity chromatography, as co-crystallization chaperones, protein aggregation controllers, enzyme activity tuners, and the specificities of the unconventional single-domain fragments.

Direct detection of the biological toxin in acidic environment by electrochemical impedimetric immunosensor

This study describes the direct detection of the biological toxin (Ricin) in acidic environment without pH adjustment by hydrophobically modified electrochemical impedance immunosensor (EII). The nano-porous aluminum substrate for EII was hydrophobically modified via self-assembled monolayer (SAM) of APTES. Biosensor for the detection of the Ricin was fabricated by the covalent cross-linking of antibody (Ab) with APTES-SAM. The immunoreactions between the immobilized Ab and the biological toxin in several diagnostic solutions were monitored by the electrochemical impedance spectroscopy (EIS) under the polarization of EII versus reference electrode. EII could detect the presence of the biological toxin in acidic foods in 20 mins without pH adjustment. The negatively charged ions including hydroxides would be adsorbed on the hydrophobic body of APTES-SAMs by the polarization during EIS analysis, and offset the effect of acids on the immunological activity of the immobilized Ab. It suggested that the adsorption of negatively charged ions helped to keep the immunological activities of the immobilized Ab on EII in acidic environment. Proposed mechanism of the localized pH adjustment that makes possible immunoreaction occurrence in low pH sample matrix is briefly discussed.

Analysis of rotavirus NSP4 genotypes and age-dependent antibody response against NSP4 in Shanghai, China

This study aimed to determine the genotypes of NSP4 in children with acute rotavirus diarrhea and evaluate serum antibody titers to NSP4 in different age groups in Shanghai, China. A total of 171 stool specimens were collected from hospitalized patients < or =5 years of age who had acute rotavirus diarrhea between January 2003 and December 2006. Serum samples were collected from healthy individuals, including 200 for 0-60 months of age and 30 for over 5 years of age. NSP4-B type was the single predominant genotype during 2003-2006 in Shanghai. The titers of NSP4 specific IgG antibody increased with age after birth and peaked during 12-23 months of age, thereafter dropping to a level as low as that in the first 5 months of age. However, high levels of antibody against whole rotavirus were maintained in older children over 5 years of age and in adults. Information on prevalence of NSP4 genotypes in this area of China provides useful data for formulating vaccine policy. Short antibody immune memory compared with that induced mainly by rotavirus structural proteins indicated the protective effect against rotavirus may not persist long term if a single NSP4 protein is applied as the rotavirus vaccine.

Immunological Implications of the use of Plant Lectins for Drug and Vaccine Targeting to the Gastrointestinal Tract

Plant lectins are under consideration as targeting agents to enhance the efficacy of orally administered drugs and vaccines. A significant issue that must be considered is the immunogenicity of these molecules since an immune response to the targeting agent may interfere with its ability to interact with the epithelium. In contrast, the ability of certain lectins to activate the immune system may be exploited in the delivery of vaccines. We previously demonstrated that plant lectins vary widely in their immunogenicity and in particular that mistletoe lectins (ML) I, II and II (MLI, MLII, MLIII) are potent immunogens when administered nasotracheally. Here, we measured immune responses following oral delivery of the MLs and assessed their ability to enhance responses to a co-administered antigen to determine if the molecules possess adjuvant activity. Oral administration of the lectins induced potent lectin-specific systemic and mucosal antibody responses. In addition, each of the three lectins possessed adjuvant activity when delivered orally together with ovalbumin (OVA). The lectins enhanced both serum and mucosal antibody responses to the co-delivered antigen. This shows for the first time that MLI, MLII and MLIII possess adjuvant activity when administered orally and may provide a platform for the generation of effective mucosal adjuvants.

Epitope mapping and use of epitope-specific antisera to characterize the VP5* binding site in rotavirus SA11 NSP4

Rotavirus (RV) is the leading cause of infantile gastroenteritis worldwide. RV nonstructural protein 4 (NSP4), the first characterized viral enterotoxin, is a 28-kDa glycoprotein that has pleiotropic functions in RV infection and pathogenesis. NSP4 has multiple forms enabling it to perform its different functions. Dissecting such functions could be facilitated by use of epitope-specific antibodies. This work mapped the epitopes for the monoclonal antibody B4-2/55 and three polyclonal antisera generated against synthetic SA11 NSP4 peptides corresponding to residues 114-135, 120-147, and 150-175. The epitope for B4-2/55 mapped to residues 100-118, wherein residues E105, R108 and E111 are critical for antibody binding. Antiserum generated to two peptides (aa114-135 and aa120-147) with enterotoxin activity each recognize a single but distinct epitope. The epitope for the peptide antiserum to aa114-135 was mapped to residues 114-125 with highly conserved residues T117/T118, E120, and E122 being critical for antibody binding. The peptide antiserum to aa120-147 binds to NSP4 at residues 130-140 and residues Q137-T138 are critical for this epitope. Finally, the epitope for the antiserum to peptide aa150-175 mapped to residues 155-170, wherein residues E160 and E170 are critical for antibody binding. Knowledge of the binding sites of domain-specific antibodies can aid in further characterizing different functions of NSP4. To demonstrate this, we characterized the interaction between NSP4 and VP5() [K(D)=0.47 microM] and show that binding of NSP4 to VP5* is blocked by antibody to NSP4 aa114-135 and aa120-147, but not aa150-175. The use of single epitope-specific antibodies to differentially block functions of NSP4 is a feasible approach to determine the functional domain structure of this important RV virulence factor.

Rational approaches to developing an anti-disease vaccine against malaria

Vaccination against pathogen toxins provides a rational approach to prevent morbidity and mortality, and is widely validated in the context of bacterial infections. A saccharide-conjugate vaccine targeting the malaria glycosylphosphatidylinositol toxin glycan could therefore prevent severe disease. This strategy could also reduce the risk posed by 'rebound' infections or immunopathology associated with other interventions.

The innate immune response to infection, toxins and trauma evolved into networks of interactive, defensive, reparative, regulatory, injurious and pathogenic pathways

It is hypothesized that, under selective pressure from infections, trauma and toxins, multicellular organisms evolved an innate immune response (IIR): (1) comprising neural, endocrine, biochemical and cellular pathways that restore homeostasis through pathogen clearance, repair of injury and regulation of inflammation, but also mediate injury and disease; (2) that functions independently of as well as in concert with the adaptive immune response (AIR); (3) whose functions in health and disease depend upon cross-talk and networking among these pathways. A critical review of the literature provides strong evidence to support the evolution of the IIR, Propositions 1 and 2 and partial support for Proposition 3: there are numerous interactions among the mammalian IIR pathways, but there is no direct evidence for more complex functioning networks in vivo. Some implications and questions raised by the hypothesis are presented.

Ricin toxin B subunit enhancement of rotavirus NSP4 immunogenicity in mice

A 90-amino acid peptide from the simian rotavirus SA-11 nonstructural protein, NSP4 was linked to the N-terminus of the Ricinus communis A-B toxin B subunit protein (RTB) and synthesized in Escherichia coli. Recombinant RTB and the NSP4(90)::RTB fusion protein bound artificial receptor glycoprotein asialofetuin in an in vitro enzyme-linked immunosorbent assay (ELISA), demonstrating biological activity of the recombinant protein. Mice co-inoculated with purified recombinant RTB plus NSP4(90) peptide proteins or heat denatured NSP4(90)::RTB fusion protein generated higher titers of serum anti-NSP4(90) IgG antibodies than mice immunized with NSP4(90) peptide alone, indicating the presence of adjuvant functions for N-terminal linked RTB. Serum anti-NSP4(90) IgG titers were highest in mice immunized with native recombinant NSP4(90)::RTB fusion protein, confirming the immunostimulatory function of RTB. Results of experiments described here demonstrate the feasibility of using RTB mediated adjuvant functions for stimulation of the antigenicity of a rotavirus nonstructural protein. The ability of recombinant NSP4(90)::RTB fusion protein synthesized in E. coli to bind glycoprotein receptor molecules effectively indicates that protein linkage to the RTB N-terminus and synthesis of the recombinant NSP4(90)::RTB fusion protein in bacteria do not interfere with the immunostimulatory properties of the RTB subunit.

Evaluation of serum antibody responses against the rotavirus nonstructural protein NSP4 in children after rhesus rotavirus tetravalent vaccination or natural infection

The immune response elicited by the rotavirus nonstructural protein NSP4 and its potential role in protection against rotavirus disease are not well understood. We investigated the serological response to NSP4 and its correlation with disease protection in sera from 110 children suffering acute diarrhea, associated or not with rotavirus, and from 26 children who were recipients of the rhesus rotavirus tetravalent (RRV-TV) vaccine. We used, as antigens in an enzyme-linked immunosorbent assay (ELISA), affinity-purified recombinant NSP4 (residues 85 to 175) from strains SA11, Wa, and RRV (genotypes A, B, and C, respectively) fused to glutathione S-transferase. Seroconversion to NSP4 was observed in 54% (42/78) of the children who suffered from natural rotavirus infection and in 8% (2/26) of the RRV-TV vaccine recipients. Our findings indicate that NSP4 evokes significantly (P < 0.05) higher seroconversion rates after natural infection than after RRV-TV vaccination. The serum antibody levels to NSP4 were modest (titers of < or = 200) in most of the infected and vaccinated children. A heterotypic NSP4 response was detected in 48% of the naturally rotavirus-infected children with a detectable response to NSP4. Following natural infection or RRV-TV vaccination, NSP4 was significantly less immunogenic than the VP6 protein when these responses were independently measured by ELISA. A significant (P < 0.05) proportion of children who did not develop diarrhea associated with rotavirus had antibodies to NSP4 in acute-phase serum, suggesting that serum antibodies against NSP4 might correlate with protection from rotavirus diarrhea. In addition, previous exposures to rotavirus did not affect the NSP4 seroconversion rate.

Oral immunization with a shiga toxin B subunit::rotavirus NSP490 fusion protein protects mice against gastroenteritis

A fusion protein containing the shiga toxin-1 B subunit (STB) linked to a 90 amino acid peptide (aa residues 86--175) from simian rotavirus (SA--11) nonstructural protein NSP4 was synthesized in Escherichia coli. Mice orally inoculated with 60 microg of STB::NSP4(90) fusion protein per dose generated higher humoral and intestinal antibody titers than mice inoculated with 30 microg of NSP4 alone. Serum anti-NSP4 IgG2a isotype titers were substantially greater than IgG1 titers, suggesting a dominant Th1 immune response. ELISA measurement of cytokines secreted from splenocytes isolated from immunized mice confirmed the STB::NSP4(90) fusion protein stimulation of a strong Th1 cell mediated immune response. Diarrhea in SA-11 rotavirus challenged neonates suckling from STB::NSP4 immunized dams was significantly reduced in severity and duration in comparison with virus challenged neonates from unimmunized mice. Together, our experiments demonstrate for the first time that the shiga toxin B subunit provides ligand mediated delivery of virus antigens to the gut-associated lymphoid tissues for enhanced stimulation of humoral and cellular responses against rotavirus gastroenteritis.

Mucosal immunization with a ricin toxin B subunit-rotavirus NSP4 fusion protein stimulates a Th1 lymphocyte response

The castor-oil plant Ricinus communis A-B dimeric toxin B subunit (RTB) was genetically linked at its N-terminus with a 90 amino acid peptide from simian rotavirus SA-11 non-structural protein NSP4(90) and produced in Escherichia coli BL21 cells. Biologically active recombinant NSP4(90)-RTB fusion protein was shown to bind glycoprotein asialofetuin receptor molecules in an in vitro enzyme-linked immunosorbent assay (ELISA). Oral inoculation of the purified NSP4(90)-RTB ligand-antigen fusion protein delivered the chimeric protein to intestinal epidermal cells for mucosal immunization against rotavirus infection. Mice fed the NSP4(90)-RTB fusion protein generated higher humoral and intestinal antibody titers than mice inoculated with NSP4(90) alone. Titers of serum IgG2a antibodies were significantly higher than IgG1 titers suggesting a dominant Th1 lymphocyte immune response. ELISA measurement of cytokines secreted from splenocyte isolated from immunized mice confirmed NSP4(90)-RTB fusion protein stimulates a strong Th1 cell-mediated immune response. The experimental results demonstrate that the ricin toxin B subunit N-terminus can be used as a site for delivery of virus antigens to the gut associated lymphoid tissues for RTB-mediated immune stimulation of antiviral mucosal immune responses.

Antibody microarrays for native toxin detection

We have developed antibody-based microarray techniques for the multiplexed detection of cholera toxin beta-subunit, diphtheria toxin, anthrax lethal factor and protective antigen, Staphylococcus aureus enterotoxin B, and tetanus toxin C fragment in spiked samples. Two detection schemes were investigated: (i) a direct assay in which fluorescently labeled toxins were captured directly by the antibody array and (ii) a competition assay that employed unlabeled toxins as reporters for the quantification of native toxin in solution. In the direct assay, fluorescence measured at each array element is correlated with labeled toxin concentration to yield baseline binding information (Langmuir isotherms and affinity constants). Extending from the direct assay, the competition assay yields information on the presence, identity, and concentration of toxins. A significant advantage of the competition assay over reported profiling assays is the minimal sample preparation required prior to analysis because the competition assay obviates the need to fluorescently label native proteins in the sample of interest. Sigmoidal calibration curves and detection limits were established for both assay formats. Although the sensitivity of the direct assay is superior to that of the competition assay, detection limits for unmodified toxins in the competition assay are comparable to values reported previously for sandwich-format immunoassays of antibodies arrayed on planar substrates. As a demonstration of the potential of the competition assay for unlabeled toxin detection, we conclude with a straightforward multiplexed assay for the differentiation and identification of both native S. aureus enterotoxin B and tetanus toxin C fragment in spiked dilute serum samples.

Production of vaccines against leading biowarfare toxins can utilize DNA scientific technology

There are a significant number of different natural toxins that are potential biological warfare agents against which a vaccine is needed. DNA science has been a key to the development of potential vaccines against the top threat toxin and should contribute such effects for other toxin's vaccines. Several different DNA technological scientific techniques have been used to accomplish the general goals of (1) cloning of the toxin or large toxin fragments, (2) altering the specific gene sequence to obtain high level expression of vaccine candidate production in alternate species (3) placement of the vaccine gene in very different presentation types of species.

Cloning and expression of mistletoe lectin III B-subunit

Aqueous extracts of mistletoe (Viscum album L.) contain toxic proteins (lectins) MLI (viscumin), MLII, and MLIII. We previously cloned the gene encoding MLIII precursor. In the present study, a gene fragment encoding the carbohydrate-binding subunit of mistletoe toxic lectin MLIII was cloned and expressed in Escherichia coli cells. The structure and immunochemical properties of recombinant MLIII B-subunit were investigated using a panel of monoclonal antibodies against ML-toxins. Sugar-binding activity of recombinant MLIII B-subunit was determined by ELISA. Amino acid sequence analysis of the cloned MLIII compared with known mistletoe toxins and other ribosome-inactivating type II proteins (ricin, abrin a, and nigrin b B-subunits) revealed essential features of the recombinant MLIIIB primary structure that could determine sugar specificity of the lectin as well as immunomodulating and anti-tumor properties of mistletoe extracts.

Structure-based preliminary analysis of immunity and virulence of SARS coronavirus

The research on SARS-associated coronavirus (SARS-CoV) has not stopped since its discovery, but the pathogenesis of SARS is still unclear. To explore the possible molecular mechanisms of the invasion and virulence of SARS-CoV, we investigated the structural basis of the viral proteins using computational biology. Forty-five motifs relating to superantigens, toxins and other bioactive molecules were detected in the proteins of SARS-CoV. The results showed that the distribution of the motifs varied in different proteins. Enzyme-like motifs were located in the R protein, while ICAM- 1-like and toxin-like molecules were located in the spike, envelop, nucleocapsid, PUP1, PUP 2 and PUP 4 proteins. Comparison of SARS-CoV with other viruses (OC43, PEDV, HRSV, HHerpV and HAdenoV) showed that each group of motifs was different for each type of virus. Data suggest that the proteins of SARS-CoV with toxic motifs might play crucial roles in targeting host cells and interfering with the immune system. This study provides new information for drug and vaccine design, as well as therapeutic strategies against SARS.

From toxin to adjuvant: basic mechanisms for the control of mucosal IgA immunity and tolerance

We provide compelling evidence that delivery of Ag in the absence of ADP-ribosylation can promote tolerance, whereas ADP-ribosyltransferase activity induces IgA immunity and prevents tolerance. By linking Ag to the ADP-ribosylating enzyme, cholera toxin subunit A1 (CTA1), we could show that the combination of targeting to antigen-presenting cells (APC) and enzymatic activity is a highly effective means of controlling the induction of tolerance or immunity. Firstly, we demonstrated that cholera toxin (CT), although potentially binding to all nucleated cells, in fact, bound preferentially to dendritic cells (DC) in vivo. Following injection of CT-conjugated Ag, we found that DC in the marginal zone (MZ) of the spleen accumulated Ag, a process that was GM1-ganglioside receptor dependent. Contrary to CTB, which also delivered Ag to the MZ DC, CT matured and activated co-stimulatory functions in the targeted DC and greatly augmented immune responses to Ag. Secondly, when Ag was incorporated into the CTA1-DD fusion protein, which equals the CT in adjuvant function but lacks GM1-ganglioside-binding ability, we greatly augmented specific responses to Ag. The DD-bound Ag was distinctly targeted to B cells and probably also to follicular dendritic cells (FDC) in vivo. Thus, in both constructs Ag was targeted to APC and associated with an ADP-ribosylating enzyme, which resulted in greatly enhanced immunogenicity. When the enzymatic activity was absent, as in CT B-subunit (CTB) or in the inactive CTA1R7K-DD mutant, Ag largely failed to stimulate an active immune response. Rather, this type of Ag exposure resulted in Ag-specific tolerance, especially when mucosal delivery of Ag was attempted. Therefore, targeting to APC in the absence or presence of the CTA1-enzyme appears to be an effective means to control tolerance and active protective IgA immunity.

Humoral immune response to rotavirus NSP4 enterotoxin in Spanish children

The rotavirus non-structural protein 4 (NSP4) has been shown to play a crucial role in rotavirus-induced diarrhea, acting as a viral enterotoxin. It has also been demonstrated that antibody to NSP4 can reduce the severity of rotavirus-induced diarrhea in newborn mice. Two recombinant baculoviruses, expressing the NSP4 protein from the SA11 and Wa rotavirus strains, genotypes A and B, respectively, were used to produce and purify these glycoproteins, which were applied as antigen in an enzyme-linked immunosorbent assay (ELISA) to test the specific antibody response to NSP4 in human sera. Serum samples from 30 children convalescing from a rotavirus infection, from 54 healthy children under 5-years-old, and from 49 adults were tested to determine the presence of antibodies to the viral enterotoxin and to rotavirus structural proteins. Seventy percent of the sera from rotavirus-infected children showed an IgG antibody response to either one or both NSP4 proteins used in this study, although the response was weak. However, IgG antibodies towards either one or both NSP4 proteins were only detected in 26% of the non-convalescent healthy children and in only 18% of the adults. No serum IgA antibodies towards NSP4 were found in this study. IgG antibody recognition of the NSP4 protein from the SA11 and Wa rotavirus strains was not always heterotypic.

Tumor-associated CD75s gangliosides and CD75s-bearing glycoproteins with Neu5Acalpha2-6Galbeta1-4GlcNAc-residues are receptors for the anticancer drug rViscumin

The anticancer drug rViscumin, currently under clinical development, has been shown in previous studies to be a sialic acid specific ribosome inactivating protein (RIP). Comparative binding assays with the CD75s-specific monoclonal antibodies HB6 and J3-89 revealed rViscumin to be a CD75s-specific RIP due to identical binding characteristics toward CD75s gangliosides. The receptor gangliosides are IV6nLc4Cer, VI6nLc6Cer, and the newly characterized ganglioside VIII6nLc8Cer, all three carrying the Neu5Acalpha2-6Galbeta1-4GlcNAc motif. To elucidate the clinical potential of the rViscumin targets, CD75s gangliosides were determined in several randomly collected gastrointestinal tumors. The majority of the tumors showed an enhanced expression of CD75s gangliosides compared with the unaffected tissues. The rViscumin binding specificity was further investigated with reference glycoproteins carrying sialylated and desialylated type II N-glycans. Comparative Western blots of rViscumin and ricin, an rViscumin homologous but galactoside-specific RIP, revealed specific recognition of type II N-glycans with CD75s determinants by rViscumin, whereas ricin failed to react with terminally sialylated oligosaccharides such as CD75s motifs and others. This strict binding specificity of rViscumin and the increased expression of CD75s gangliosides in various tumors suggest this anticancer drug as a promising candidate for an individualised adjuvant therapy of human tumors.

[Detection of immune complexes using atomic force microscopy]

Complex formation between immunoglobulins and ligands immobilized on mica was studied by atomic force microscopy in two different systems. In the first system, 60-kDa ligands possessing only one site for antibody recognition were used. In the other system, a more complex interaction of human immunoglobulin with immobilized polyclonal antibodies was studied. In both systems, specific complexes with proper ligand appeared, and unspecific interaction was not detected. The method of revealing immunocomplexes by image atomic force microscopy can be used in the development of modern diagnostic systems.

Mistletoe lectin I is a sialic acid-specific lectin with strict preference to gangliosides and glycoproteins with terminal Neu5Ac alpha 2-6Gal beta 1-4GlcNAc residues

Mistletoe lectin I (ML-I) is a type II ribosome-inactivating protein, which inhibits the protein biosynthesis at the ribosomal level. ML-I is composed of a catalytically active A-chain with rRNA N-glycosidase activity and a B-chain with carbohydrate binding specificities. Using comparative solid-phase binding assays along with electrospray ionization tandem mass spectrometry, ML-I was shown to preferentially bind to terminally alpha2-6-sialylated neolacto series gangliosides from human granulocytes. IV(6)Neu5Ac-nLc4Cer, VI(6)Neu5Ac-nLc6Cer, and VIII(6)Neu5Ac-nLc8Cer were identified as ML-I receptors, whereas the isomeric alpha2-3-sialylated neolacto series gangliosides were not recognized. Only marginal binding of ML-I to terminal galactose residues of neutral glycosphingolipids with a Galbeta1-4Glc or Galbeta1-4GlcNAc sequence was determined, whereas a distal Galalpha1-4Gal, GalNAcbeta1-3Gal, or GalNAcbeta1-4Gal disaccharide did not bind at all. Among the glycoproteins investigated in Western blot and microwell adsorption assays, only those carrying Neu5Acalpha2-6Galbeta1-4GlcNAc residues, exclusively, predominantly, or even as less abundant constituents in an assembly with Neu5Acalpha2-3Galbeta1-4GlcNAc-terminated glycans, displayed high ML-I binding capacity. From our data we conclude that (i) ML-I has to be considered as a sialic acid- and not a galactose-specific lectin and (ii) neolacto series gangliosides and sialoglycoproteins with type II glycans, which share the Neu5Acalpha2-6Galbeta1-4GlcNAc terminus, are true ML-I receptors. This strict preference might help to explain the immunostimulatory potential of ML-I toward certain leukocyte subpopulations and its therapeutic success as a cytotoxic anticancer drug.

Innate immunity and biodefence vaccines

Host defence in vertebrates is achieved by the integration of two distinct arms of the immune system: the innate and adaptive responses. The innate response acts early after infection (within minutes), detecting and responding to broad cues from invading pathogens. The adaptive response takes time (days to weeks) to become effective, but provides the fine antigenic specificity required for complete elimination of the pathogen and the generation of immunologic memory. Antigen-independent recognition of pathogens by the innate immune system leads to the rapid mobilization of immune effector and regulatory mechanisms that provide the host with three critical advantages: (i) initiating the immune response (both innate and adaptive) and providing the inflammatory and co-stimulatory context for antigen recognition; (ii) mounting a first line of defence, thereby holding the pathogen in check during the maturation of the adaptive response; and (iii) steering the adaptive immune system towards the cellular or humoral responses most effective against the particular infectious agent. The quest for safer and more effective vaccines and immune-based therapies has taken on a sudden urgency with the increased threat of bioterrorism. Only a handful of vaccines covering a small proportion of potential biowarfare agents are available for human use (e.g. anthrax and small pox) and these suffer from poor safety profiles. Therefore, next generation biodefence-related vaccines and therapies with improved safety and the capacity to induce more rapid, more potent and broader protection are needed. To this end, strategies to target both the innate and adaptive immune systems will be required.

Production of antibodies and antibody fragments in Escherichia coli and a comparison of their functions, uses and modification

Antibody-based drugs are now used in the clinic, and their importance as therapeutics is expected to increase in the coming decade, both in terms of diseases treated and market value. However, the proportion of patients that can be treated is to some extent affected by the availability and cost of the therapeutic. Therefore, the means of production and purification of the therapeutic entity, as well as the type of therapeutic entity, are of great concern. Escherichia coli represents a good production host in terms of scale and speed of production, but it also has technical and biological limitations. The aim of this review is to describe and discuss the relative benefits and limitations of E coli as a host for the production of antibodies and engineered antibody fragments.

A new antigenic epitope appears in the catalytic subunit of viscumin during intracellular transport

The plant toxin viscumin (60 kD) consists of B- ("binding") and A- ("active") subunits joined by a disulfide bond. The B-subunit is a lectin interacting with galactose-containing glycolipids and glycoproteins of the cell surface. The A-subunit possesses N-glycosidase activity which modifies 28S ribosomal RNA. This results in irreversible inhibition of protein synthesis. After binding and receptor-mediated endocytosis viscumin-containing vesicles are transported to endoplasmic reticulum where the A- (catalytic) subunit is subsequently translocated to cytosol. It is possible that translocation of A-subunit requires its unfolding. For identification of epitopes which might appear during such unfolding, we developed hybridomas producing monoclonal antibodies against denatured viscumin A-chain. Resistance of hybridoma cells to cytotoxic action of viscumin suggests antibody-toxin interaction inside these cells. TA7 hybridoma cells against an epitope which appears only in denatured viscumin are insensitive to the toxin. This suggests that antibody-toxin interaction occurs before transmembrane translocation of the catalytic A-chain into the cytoplasm. Consequently, toxin resistance of TA7 hybridoma cells implies the appearance of a new epitope in viscumin during its intracellular transportation inside of vesicles. Sixty five octapeptides have been synthesized and epitopes have been identified for monoclonal TA7 antibody and immune mouse serum by means of ELISA. Based on the epitopic mapping the peptide A96-ETHLFTGT-T105 was chemically synthesized and binding of this peptide to the monoclonal antibody TA7 and conformation of antigenic determinant (L100-FTGT-T105) was investigated by means of (1)H-NMR spectroscopy.

"Venom" of the slow loris: sequence similarity of prosimian skin gland protein and Fel d 1 cat allergen

Bites inflicted on humans by the slow loris (Nycticebus coucang), a prosimian from Indonesia, are painful and elicit anaphylaxis. Toxins from N. coucang are thought to originate in the brachial organ, a naked, gland-laden area of skin situated on the flexor surface of the arm that is licked during grooming. We isolated a major component of the brachial organ secretions from N. coucang, an approximately 18 kDa protein composed of two 70-90 amino-acid chains linked by one or more disulfide bonds. The N-termini of these peptide chains exhibit nearly 70% sequence similarity (37% identity, chain 1; 54% identity, chain 2) with the two chains of Fel d 1, the major allergen from the domestic cat (Felis catus). The extensive sequence similarity between the brachial organ component of N. coucang and the cat allergen suggests that they exhibit immunogenic cross-reactivity. This work clarifies the chemical nature of the brachial organ exudate and suggests a possible mode of action underlying the noxious effects of slow loris bites.

Detection of rViscumin in plasma samples by immuno-PCR

To allow for pharmacokinetic studies in adjunction with the current clinical developments of the potent cytostatic anti-cancer drug rViscumin, a sandwich immuno-PCR (IPCR) assay was developed for the detection of rViscumin in blood plasma. The IPCR was carried out with a commercially available reagent kit, consisting of pre-assembled rViscumin-specific antibody-DNA conjugates as well as a specific competitor DNA fragment to be amplified by PCR. Various combinations of capture- and detection-antibodies were compared for performance in IPCR. Using the optimized assay, as few as 50 zeptomol (approx. 100 fg/ml) rViscumin (MW 57 kDa) was detectable in standardized human serum samples. The IPCR assay was very selective for rViscumin and in spiking experiments in proband plasma samples, signal recovery rates between 70% and 120% were obtained. The linear sensitivity range of the assay covered more than five orders of magnitude. Repeated measurements of rViscumin resulted in a mean standard deviation value of 14.2%.

Effects of a lectin- and a viscotoxin-rich mistletoe preparation on clinical and hematologic parameters: a placebo-controlled evaluation in healthy subjects

BACKGROUND AND OBJECTIVES

Mistletoe preparations, which are widely used among patients with cancer in Germany, have immunomodulating properties in vitro and in vivo. The aim of this evaluation was to determine and compare the effects of a lectin-rich (Iscador Qu [IQ] special, Weleda Company, Schwäbisch, Gmünd, Germany.) and a lectin-poor but viscotoxin-rich (Iscador Pini [IP] Weleda Company) mistletoe preparation on clinical and hematologic parameters in healthy subjects.

DESIGN

In a double-blinded study, 48 volunteers were randomized to one of three groups: 16 received IQ or IP in increasing doses or placebo twice per week subcutaneously for 12 weeks. The differential blood count and the acute phase markers haptoglobin and C-reactive protein were examined weekly and the symptoms were scored using standardized questionnaires.

RESULTS

IQ resulted in significant eosinophilia (315 +/- 109) beginning at week 5 (until week 12) compared to IP (183 +/- 120) or placebo (200 +/- 179). Furthermore, the acute phase marker haptoglobin was significantly increased in the IQ group during week 4. Dose-dependent local reactions (LRs) at the injection site occurred in all subjects who received mistletoe preparations but were stronger in the IQ-treated subjects than in the IP-treated group. The LRs observed in the IQ-treated group were characterized by stronger itching and longer latency than LRs in the IP-treated group (p < 0.05). Severe side-effects did not occur in any of the probands.

CONCLUSIONS

IQ but not IP can induce eosinophilia in healthy individuals, and this may be related to its content of mistletoe lectins. In contrast, exposure to the viscotoxin-enriched extract IP did not result in specific changes of hematologic parameters. Furthermore, intensity and time course of local reactions seemed to depend on the concentration of mistletoe lectins in those extracts.

1st class ticket to class I: protein toxins as pathfinders for antigen presentation

A number of bacterial toxins have evolved diverse strategies for crossing membrane barriers in order to reach their substrates in the mammalian cytosol. Recent studies show that this property can be exploited for the delivery of fused antigens into the major histocompatibility complex class I-restricted presentation pathway, with the goal of eliciting a specific immune response. Here we discuss the peculiarities of the trafficking pathways of a variety of toxins, and how these may allow the toxins to be used as delivery vehicles for therapeutic and diagnostic purposes.

Mistletoe lectins enhance immune responses to intranasally co-administered herpes simplex virus glycoprotein D2

The mucosal adjuvant properties of the three type 2 ribosome-inactivating proteins (RIPs) from the European mistletoe, Viscum album L., were investigated. Mistletoe lectins were compared with cholera toxin (CT) as adjuvants when delivered nasotracheally together with herpes simplex virus glycoprotein D2 (gD2). All three mistletoe lectins (MLI, MLII, MLIII) were potent mucosal adjuvants. Co-administration of MLI, MLII or MLIII with gD2 led to significantly higher levels of gD2-specific mucosal immunoglobulin A (IgA) and systemic immunoglobulin G (IgG) antibody than when the antigen was delivered alone. The levels of antibodies induced were similar to those generated in mice immunized with gD2 and the potent mucosal adjuvant CT. Administration of ML1 with gD2 enhanced the antigen-specific splenic T-cell proliferative response. Interleukin-5 (IL-5), but not interferon-gamma (IFN-gamma), was detected in supernatants from splenocytes stimulated in vitro with gD2. This indicates that MLI enhanced type 2 T-helper cell (Th2) responses to the bystander antigen, gD2. Analysis of the gD2- and lectin-specific IgG subclass titres in mice immunized with gD2 and MLI, MLII or MLIII revealed a high ratio of IgG1 : IgG2a, which is compatible with the selective induction of Th2-type immune responses.

Induction of antibodies to viscotoxins A1, A2, A3, and B in tumour patients during therapy with an aqueous mistletoe extract

Mistletoe extracts exert immunomodulatory properties on immunocompetent cells of the innate as well as the specific immune system. These effects have been mainly ascribed to mistletoe lectin 1 (ML-1) present in most of the extracts. However, it became evident that also other components of these extracts may induce immunological reactions, and especially viscotoxins (VT) may be of relevance. Aim of the study was, therefore, to evaluate whether VT like ML-1 could activate B-cells and lead to the production of VT-specific antibodies. Sera from 26 patients with different tumours who were treated with the mistletoe extract ABNOBAviscum Mali (AM) 4 for at least 18 weeks were analysed before therapy and after 3, 6, 9, 12, and 18 weeks. Sera were tested by ELISA against the four viscotoxins A1, A2, A3, B, as well as against ML-1. Within the observation period twenty-four (92%) of the 26 patients developed antibodies to at least one of the four VT and 25 (96%) to ML-1. In most instances, anti-VT antibodies appeared after 6-9 weeks of treatment. The antibodies were predominantly of the IgG type belonging preferentially to the IgG1 and IgG3 subclass. IgE antibodies were found only to VT-B and to ML-1. There was no relation between the development of antibodies to VT and ML-1, and also cross-reactivity could be excluded with high probability. These data indicate that not only ML-1 but also VT induce immunological responses in patients treated with mistletoe extracts. Whether there is any relationship to the postulated anti-tumour effect of mistletoe extracts has, however, still to be evaluated.

[Role of the interchain interaction domain of chain a in viscumin cytotoxicity]

The sequence coding for the viscumin (mistletoe lectin I, MLI) A-chain (MLA) was cloned from Viscum album genomic DNA with the use of synthetic primers. This yielded three recombinant (r) MLA variants differing in number of amino acid substitutions. The rMLA structure and properties were probed using monoclonal antibodies against native MLA. Native MLI B-chain (MLB) was shown to facilitate the rMLA folding. Native MLI and chimeric proteins consisting of rMLA and native MLB did not differ in cytotoxic effect on 3T3 fibroblastoid cells. Residues were identified that are located in the MLB-contacting region and have a considerable effect on the immunochemical and cytotoxic properties of rMLA.

[Blood and tissue eosinophilia, mistletoe lectin antibodies and quality of life in a breast cancer patient undergoing intratumoral and subcutaneous mistletoe therapy]

BACKGROUND

Mistletoe therapy (MT) is a method of complementary medicine whose efficacy is controversially discussed. Until now there is a lack of data of high-dose intratumoral application.

PATIENT AND METHODS

We are presenting a 3-year follow-up of an 80-year-old woman with metastasized breast cancer (c(2)T3/N1/M1) receiving combined intra- and peritumoral and subcutaneous MT with ABNOBAviscum(r) and concomitant pamitron acid. At time of admission the patient had bone metastases (thoracic vertebra 11 fracture), a lymphangiosis carcinomatosa, bilateral pleural effusions, and a reduced quality of life (QoL).

RESULTS

Under MT we induced an eosinophilia and an elevation of eosinophil cationic protein (ECP). Simultaneously, we ascertained a reduction of 50% of Ca 15-3 and a sustained partial tumor remission. After 5 months the mistletoe-lectin-1 antibodies IgG-1 and -3 were maximally increased and we perceived a second Ca 15-3 reduction. After 3 months we observed a benefit in QoL. During the following 5 months the patient gained about 10 kg in weight. In the second year slow tumor progress was observed. After 19 months the patient had pneumonia which caused an MT pause. Subsequently, a combined intratumoral mistletoe and letrozol therapy brought a partial remission. The patient lived without chemo and radiation therapy more than 3 years with good QoL and died after 41 months, after a sepsis and a following stroke without signs of tumor progress.

CONCLUSION

In metastasized breast cancer a palliative high-dose local MT can make a contribution to a tumor reduction and a benefit in QoL.

In vivo-induction of antibodies to mistletoe lectin-1 and viscotoxin by exposure to aqueous mistletoe extracts: a randomised double-blinded placebo controlled phase I study in healthy individuals

BACKGROUND

Several studies have been performed in tumour patients to analyse the immunological response to mistletoe extracts. Considering the fact that these extracts are given subcutaneously in most instances, the kind of application resembles a typical immunization schedule. We therefore wanted to see how those extracts act on immunocompetent cells of healthy individuals hoping that this kind of provocation test may give new informations about a more specific application of these extracts in certain diseases.

SUBJECTS/METHODS

47 healthy individuals were exposed for twelve weeks either to Iscador Quercus special (IQ) known to be rich in mistletoe lectin (ML)-1 (n = 16), to Iscador Pini (IP) being poor in ML-1 but enriched in viscotoxins (n = 15), or to placebo (physiological saline) (n = 16) in a randomised, double-blinded placebo-controlled study. Humoral immunoreactivity was analysed by measuring antibodies towards the two compounds ML-1 and viscotoxin VA2 (VA2). Sera were collected in intervals of four weeks up to week 12 and again three months after last exposure.

RESULTS

None of the subjects had antibodies to ML-1 or VA2 before exposure. In week 12, anti-ML-1 antibodies of the IgG-type were found in all 16 IQ-treated individuals but only 6 of the 15 probands exposed to IP. In contrast, anti-VA2 IgG-antibodies could be detected in all individuals of both groups. The antibodies were preferentially of the IgG1 and IgG3 type while antibodies of the IgA and IgM type were produced only in a few probands. Antibodies of the IgE-type occurred only in the IQ-exposed individuals and were directed against ML-1 but not VA2. None of the probands receiving placebo developed antibodies to ML-1 or VA2. Severe side effects were not observed in any of the probands.

CONCLUSIONS

These data obtained in healthy individuals clearly indicate that IQ and IP-extracts can induce antigen-specific humoral responses. They may, therefore, provide, a solid basic for the evaluation of the humoral immune response in disease states.

Antibody reactivity of a standardized human serum protein solution against a spectrum of microbial pathogens and toxins: comparison with fresh frozen plasma

In this study, we compared a standardized solution of human serum protein (HSP) and fresh frozen plasma (FFP) with regard to the antibody specificity against a number of microbial pathogens and some important pathogenicity factors of bacterial pathogens. Due to the clinical use of HSP and FFP for therapeutical plasma exchange, we have chosen a spectrum of microbial pathogens for serological analysis that is critical in clinical settings. With the enzyme-linked immunosorbent assay technique, we could show that HSP contains marked IgG antibody reactivity against antigens of Escherichia coli, Campylobacter jejuni, Enterobacter sakazakii, Proteus mirabilis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, Chlamydia pneumoniae, and Candida albicans. Although no IgM antibodies against the pathogens tested could be detected in HSP, moderate IgA reactivity was found against 4 of 12 microbial antigens. Immunoblot analysis demonstrated specific IgA and IgG responses against the endoproteinase Glu-C and the superantigens enterotoxin A and B of S. aureus, the IgA-protease of Neisseria gonorrhoeae, and Shiga toxin 2 of enterohemorrhagic E. coli. By using 3 different HSP batches in parallel, we could demonstrate antibody reactivity against important microbial pathogens and toxins. This antibody profile is essentially more homogeneous than that of 3 batches of FFP.

Comparison between the mechanisms of action of plant toxins ricin and viscumin on the stage of intracellular dissociation

Pharmacological effects of mistletoe extracts are determined by the concentration of three toxic lectins: mistletoe lectin I (MLI, or viscumin), MLII, MLIII. These proteins, as well as ricin, belong to ribosome-inactivating proteins type 2 (RIP2). However, the extracts from the plant Ricinus communis, containing ricin, are highly toxic. Ricin is about 30 times more effective in cell culture than viscumin. The dissociation of subunits and the transmembrane transport of catalytic subunit into the cytoplasm are needed to obtain the cytotoxic effect of RIP2. In this paper, hybridomas producing monoclonal antibodies against catalytic subunits of ricin and viscumin are described. Monoclonal antibodies against different epitopes, including one localized in intra-subunit area of catalytic subunits of ricin and viscumin, do not inhibit the enzymatic activity of these proteins in cell-free system. These hybridomas are resistant to the cytotoxic action of native toxins. Protective effect of antibodies are about the same for both toxins, though the dissociation of the subunits of ricin is more effective. The causes of the differences in activity of plant toxins as pharmacological agents, and the importance of above mentioned epitopes for neutralizing antibodies at the clinical applications of mistletoe extracts are discussed.