What can neutralizing antibodies tell us about the quality of immunity in COVID-19 convalescents and vaccinees?

During the SARS-CoV-2 pandemic, the lack of standardized measurements of the immune response after vaccination or recovery from COVID-19 resulted in incomparable results and hindered correlation establishment. Prioritizing reliable and standardized methods to monitor pathogen-specific immunity is crucial, not only during the COVID-19 pandemic but also for future outbreaks. During our study of the humoral immune response, we used a SARS-CoV-2 wild-type neutralization assay, ensuring the measurement of the immune response directed to all SARS-CoV-2 antigens in their proper conformation. A head-to-head comparison of the neutralizing antibody (NAb) responses elicited by four vaccines used in Europe during 2021 (BNT162b2, mRNA-1273, ChAdOx nCoV-19, and Ad26.COV2.S) and their comparison to NAb responses in convalescents showed that while the amount was comparable, NAbs induced by natural infection were of higher quality. Namely, NAbs produced by disease were better activators of the complement system than NAbs induced by vaccination. Furthermore, the contribution of spike protein-specific IgGs to the SARS-CoV-2 neutralization was lower in convalescents compared to vaccinees, indicating that those who recovered from COVID-19 were armed with antibodies of additional specificities and/or classes that contributed to virus neutralization. These findings suggest that a higher stringency of public policy measures targeting individuals who have recovered from COVID-19, in comparison to those who have been vaccinated, may not have been fully justified.

Snake Antivenoms-Toward Better Understanding of the Administration Route

Envenomations induced by animal bites and stings constitute a significant public health burden. Even though a standardized protocol does not exist, parenterally administered polyclonal antivenoms remain the mainstay in snakebite therapy. There is a prevailing opinion that their application by the i.m. route has poor efficacy and that i.v. administration should preferentially be chosen in order to achieve better accomplishment of the antivenom therapeutic activity. Recently, it has been demonstrated that neutralization not only in the systemic circulation but also in the lymphatic system might be of great importance for the clinical outcome since it represents another relevant body compartment through which the absorption of the venom components occurs. In this review, the present-day and summarized knowledge of the laboratory and clinical findings on the i.v. and i.m. routes of antivenom administration is provided, with a special emphasis on the contribution of the lymphatic system to the process of venom elimination. Until now, antivenom-mediated neutralization has not yet been discussed in the context of the synergistic action of both blood and lymph. A current viewpoint might help to improve the comprehension of the venom/antivenom pharmacokinetics and the optimal approach for drug application. There is a great need for additional dependable, practical, well-designed studies, as well as more practice-related experience reports. As a result, opportunities for resolving long-standing disputes over choosing one therapeutic principle over another might be created, improving the safety and effectiveness of snakebite management.

Multi-Detection Size Exclusion Chromatography as an Advanced Tool for Monitoring Enzyme-Antibody Conjugation Reaction and Quality Control of a Final Product

The multi-detection size exclusion chromatography (SEC) has been recognized as an advanced analytical technique for the characterization of macromolecules and process control, as well as the manufacturing and formulation of biotechnology products. It reveals reproducible molecular characterization data, such as molecular weight and its distribution, and the size, shape, and composition of the sample peaks. The aim of this work was to investigate the potential and suitability of the multi-detection SEC as a tool for surveillance over the molecular processes during the conjugation reaction between the antibody (IgG) and horseradish peroxidase (HRP), and demonstrate the plausibility of its application in the quality control of the final product, the IgG-HRP conjugate. Guinea pig anti-Vero IgG-HRP conjugate was prepared using a modified periodate oxidation method, based on periodate oxidation of the carbohydrate side chains of HRP, followed by the formation of Schiff bases between the activated HRP and amino groups of the IgG. The quantitative molecular characterization data of the starting samples, intermediates, and final product were obtained by multi-detection SEC. Titration of the prepared conjugate was performed by the ELISA and its optimal working dilution was determined. This methodology proved to be a promising and powerful technology for the IgG-HRP conjugate process control and development, as well as for the quality control of the final product, as verified by the analysis of several commercially available reagents.

Evaluation of the Interactions between Mumps Virus and Guinea Pig

Mumps is a highly contagious viral disease that can be prevented by vaccination. In the last decade, we have encountered repeated outbreaks of mumps in highly vaccinated populations, which call into question the effectiveness of available vaccines. Animal models are crucial for understanding virus-host interactions, and viruses such as mumps virus (MuV), whose only natural host is the human, pose a particular challenge. In our study, we examined the interaction between MuV and the guinea pig. Our results present the first evidence that guinea pigs of the Hartley strain can be infected in vivo after intranasal and intratesticular inoculation. We observed a significant viral replication in infected tissues up to 5 days following infection and induction of cellular and humoral immune responses as well as histopathological changes in infected lungs and testicles, without clinical signs of disease. Transmission of the infection through direct contact between animals was not possible. Our results demonstrate that guinea pigs and guinea pig primary cell cultures represent a promising model for immunological and pathogenetic studies of the complex MuV infection. IMPORTANCE Understanding of mumps virus (MuV) pathogenesis and the immune responses against MuV infection is limited. One of the reasons is the lack of relevant animal models. This study explores the interaction between MuV and the guinea pig. We demonstrated that all tested guinea pig tissue homogenates and primary cell cultures are highly susceptible to MuV infection and that α2,3-sialylated glycans (MuV cellular receptors) are being abundantly expressed at their surface. The virus remains in the guinea pig lungs and trachea for up to 4 days following intranasal infection. Although asymptomatic, MuV infection strongly activates both humoral and cellular immune response in infected animals and provides protection against virus challenge. Infection of the lungs and testicles after intranasal and intratesticular inoculation, respectively, is also supported by histopathological changes in these organs. Our findings give perspective for application of guinea pigs in research on MuV pathogenesis, antiviral response, and vaccine development and testing.

Roughness of Production Conditions: Does It Really Affect Stability of IgG-Based Antivenoms?

Antivenoms contain either pure animal IgGs or their fragments as an active substance, and are the only specific therapeutics against envenomation arising from snakebites. Although they are highly needed, the low sustainability of such preparations’ manufacture causes constant global shortages. One reason for this is the stability of the product, which contributes not only to the manufacture sustainability, but the product safety as well. It has been hypothesized that the roughness of conditions to which IgGs are exposed during downstream purification disturbs their conformation, making them prone to aggregation, particularly after exposure to secondary stress. The aim of this research was to investigate how the roughness of the downstream purification conditions influences the stability properties of purified IgGs. For this purpose, equine IgGs were extracted from unique hyperimmune plasma by two mild condition-based operational procedures (anion-exchange chromatography and caprylic acid precipitation) and three rougher ones (ammonium sulphate precipitation, cation-exchange chromatography and protein A affinity chromatography). The stability of the refined preparations was studied under non-optimal storage conditions (37 °C, 42 °C, and a transiently lower pH) by monitoring changes in the aggregate content and thermal stability of the pure IgGs. Mild purification protocols generated IgG samples with a lower aggregate share in comparison to the rougher ones. Their tendency for further aggregation was significantly associated with the initial aggregate share. The thermal stability of IgG molecules and the aggregate content in refined samples were inversely correlated. Since the initial proportion of aggregates in the samples was influenced by the operating conditions, we have shown a strong indication that each of them also indirectly affected the stability of the final preparations. This suggests that mild condition-based refinement protocols indeed generate more stable IgGs.

Modern venomics-Current insights, novel methods, and future perspectives in biological and applied animal venom research

Venoms have evolved >100 times in all major animal groups, and their components, known as toxins, have been fine-tuned over millions of years into highly effective biochemical weapons. There are many outstanding questions on the evolution of toxin arsenals, such as how venom genes originate, how venom contributes to the fitness of venomous species, and which modifications at the genomic, transcriptomic, and protein level drive their evolution. These questions have received particularly little attention outside of snakes, cone snails, spiders, and scorpions. Venom compounds have further become a source of inspiration for translational research using their diverse bioactivities for various applications. We highlight here recent advances and new strategies in modern venomics and discuss how recent technological innovations and multi-omic methods dramatically improve research on venomous animals. The study of genomes and their modifications through CRISPR and knockdown technologies will increase our understanding of how toxins evolve and which functions they have in the different ontogenetic stages during the development of venomous animals. Mass spectrometry imaging combined with spatial transcriptomics, in situ hybridization techniques, and modern computer tomography gives us further insights into the spatial distribution of toxins in the venom system and the function of the venom apparatus. All these evolutionary and biological insights contribute to more efficiently identify venom compounds, which can then be synthesized or produced in adapted expression systems to test their bioactivity. Finally, we critically discuss recent agrochemical, pharmaceutical, therapeutic, and diagnostic (so-called translational) aspects of venoms from which humans benefit.

Efficient and Sustainable Platform for Preparation of a High-Quality Immunoglobulin G as an Urgent Treatment Option During Emerging Virus Outbreaks

During the pre-vaccine era of the COVID-19 pandemic convalescent plasma has once again emerged as a major potential therapeutic form of passive immunization that in specific cases still represents irreplaceable treatment option. There is a growing concern that variable concentration of neutralizing antibodies, present in convalescent plasma which originates from different donors, apparently affects its effectiveness. The drawback can be overcome through the downstream process of immunoglobulin fraction purification into a standardized product of improved safety and efficacy. All modern procedures are quite lengthy processes. They are also based on fractionation of large plasma quantities whose collection is not attainable during an epidemic. When outbreaks of infectious diseases are occurring more frequently, there is a great need for a more sustainable production approach that would be goal-oriented towards assuring easily and readily available immunoglobulin of therapeutic relevance. We propose a refinement strategy for the IgG preparation achieved through simplification and reduction of the processing steps. It was designed as a small but scalable process to offer an immediately available treatment option that would simultaneously be harmonized with an increased availability of convalescent plasma over the viral outbreak time-course. Concerning the ongoing pandemic status of the COVID-19, the proof of concept was demonstrated on anti-SARS-CoV-2 convalescent plasma but is likely applicable to any other type depending on the current needs. It was guided by the idea of persistent keeping of IgG molecules in the solution, so that protection of their native structure could be assured. Our manufacturing procedure provided a high-quality IgG product of above the average recovery whose composition profile was analyzed by mass spectrometry as quality control check. It was proved free from IgA and IgM as mediators of adverse transfusion reactions, as well as of any other residual impurities, since only IgG fragments were identified. The proportion of S protein-specific IgGs remained unchanged relative to the convalescent plasma. Undisturbed IgG subclass composition was accomplished as well. However, the fractionation principle affected the final product's capacity to neutralize wild-type SARS-CoV-2 infectivity, reducing it by half. Decrease in neutralization potency significantly correlated with the amount of IgM in the starting material.

ChAdOx1-S adenoviral vector vaccine applied intranasally elicits superior mucosal immunity compared to the intramuscular route of vaccination

COVID-19 vaccines prevent severe forms of the disease, but do not warrant complete protection against breakthrough infections. This could be due to suboptimal mucosal immunity at the site of virus entry, given that all currently approved vaccines are administered via the intramuscular route. In this study we assessed humoral and cellular immune responses in BALB/c mice after intranasal and intramuscular immunization with adenoviral vector ChAdOx1-S expressing full-length Spike protein of SARS-CoV-2. We showed that both routes of vaccination induced a potent IgG antibody response, as well as robust neutralizing capacity, but intranasal vaccination elicited a superior IgA antibody titer in the sera and in the respiratory mucosa. Bronchoalveolar lavage from intranasally immunized mice efficiently neutralized SARS-CoV-2, which has not been the case in intramuscularly immunized group. Moreover, substantially higher percentages of epitope-specific CD8 T cells exhibiting a tissue resident phenotype were found in the lungs of intranasally immunized animals. Finally, both intranasal and intramuscular vaccination with ChAdOx1-S efficiently protected the mice after the challenge with recombinant herpesvirus expressing the Spike protein. Our results demonstrate that intranasal application of adenoviral vector ChAdOx1-S induces superior mucosal immunity and therefore could be a promising strategy for putting the COVID-19 pandemic under control. This article is protected by copyright. All rights reserved.

Is Better Standardization of Therapeutic Antibody Quality in Emerging Diseases Epidemics Possible?

During the ongoing COVID-19 epidemic many efforts have gone into the investigation of the SARS-CoV-2–specific antibodies as possible therapeutics. Currently, conclusions cannot be drawn due to the lack of standardization in antibody assessments. Here we describe an approach of establishing antibody characterisation in emergent times which would, if followed, enable comparison of results from different studies. The key component is a reliable and reproducible assay of wild-type SARS-CoV-2 neutralisation based on a banking system of its biological components - a challenge virus, cells and an anti-SARS-CoV-2 antibody in-house standard, calibrated to the First WHO International Standard immediately upon its availability. Consequently, all collected serological data were retrospectively expressed in an internationally comparable way. The neutralising antibodies (NAbs) among convalescents ranged from 4 to 2869 IU mL^-1 in a significant positive correlation to the disease severity. Their decline in convalescents was on average 1.4-fold in a one-month period. Heat-inactivation resulted in 2.3-fold decrease of NAb titres in comparison to the native sera, implying significant complement activating properties of SARS-CoV-2 specific antibodies. The monitoring of NAb titres in the sera of immunocompromised COVID-19 patients that lacked their own antibodies evidenced the successful transfusion of antibodies by the COVID-19 convalescent plasma units with NAb titres of 35 IU mL^-1 or higher.

Development of Improved High-Performance Liquid Chromatography Method for the Determination of Residual Caprylic Acid in Formulations of Human Immunoglobulins

Quality control of human immunoglobulin formulations produced by caprylic acid precipitation necessitates a simple, rapid, and accurate method for determination of residual caprylic acid. A high-performance liquid chromatography method for that purpose was developed and validated. The method involves depletion of immunoglobulins, the major interfering components that produce high background noise, by precipitation with acetonitrile (1:1, v/v). Chromatographic analysis of caprylic acid, preserved in supernatant with no loss, was performed using a reverse-phase C18 column (2.1 × 150 mm, 3 μm) as a stationary phase and water with 0.05% TFA–acetonitrile (50:50, v/v) as a mobile phase at a flow rate of 0.2 mL/min and run time of 10 min. The developed method was successfully validated according to the ICH guidelines. The validation parameters confirmed that method was linear, accurate, precise, specific, and able to provide excellent separation of peaks corresponding to caprylic acid and the fraction of remaining immunoglobulins. Furthermore, a 24−1 fractional factorial design was applied in order to test the robustness of developed method. As such, the method is highly suitable for the quantification of residual caprylic acid in formulations of human immunoglobulins for therapeutic use, as demonstrated on samples produced by fractionation of convalescent anti-SARS-CoV-2 human plasma at a laboratory scale. The obtained results confirmed that the method is convenient for routine quality control.

Compassionate mesenchymal stem cell treatment in a severe COVID-19 patient: a case report

COVID-19 presentations range from cold-like symptoms to severe symptoms with the development of acute respiratory distress syndrome (ARDS). We report on a severe COVID-19 patient who was mechanically ventilated and who developed ARDS and bacterial infection. Because of rapid clinical deterioration and the exhaustion of other treatment options, the family and attending physicians requested a compassionate use of adult allogeneic bone marrow-derived mesenchymal stem cells (MSC) in addition to commonly used immunosuppressive, antiviral, and supportive therapy. The clinical course is discussed thoroughly, with a special emphasis on the safety and effect of MSC therapy. Compassionate MSC treatment, given in three rounds, affected ARDS regression. The patient was discharged from the intensive care unit after 31 days and from hospital after 49 days in a good general condition. MSC treatment was not associated with any side effects and was well tolerated in a three-week period; therefore, it should be studied in larger trials and considered for compassionate use.

Compassionate mesenchymal stem cell treatment in a severe COVID-19 patient: a case report

COVID-19 presentations range from cold-like symptoms to severe symptoms with the development of acute respiratory distress syndrome (ARDS). We report on a severe COVID-19 patient who was mechanically ventilated and who developed ARDS and bacterial infection. Because of rapid clinical deterioration and the exhaustion of other treatment options, the family and attending physicians requested a compassionate use of adult allogeneic bone marrow-derived mesenchymal stem cells (MSC) in addition to commonly used immunosuppressive, antiviral, and supportive therapy. The clinical course is discussed thoroughly, with a special emphasis on the safety and effect of MSC therapy. Compassionate MSC treatment, given in three rounds, affected ARDS regression. The patient was discharged from the intensive care unit after 31 days and from hospital after 49 days in a good general condition. MSC treatment was not associated with any side effects and was well tolerated in a three-week period; therefore, it should be studied in larger trials and considered for compassionate use.

COVID-19 convalescent plasma as long-term therapy in immunodeficient patients?

Objectives

The patients with hematological malignancies are a vulnerable group to COVID-19, due to the immunodeficiency resulting from the underlying disease and oncological treatment that significantly impair cellular and humoral immunity. Here we report on a beneficial impact of a passive immunotherapy with convalescent plasma to treat a prolonged, active COVID-19 infection in a patient with a history of nasopharyngeal diffuse large B-cell lymphoma treated with the therapy inducing substantial impairment of particularly humoral arm of immune system. The specific aim was to quantify SARS-CoV2 neutralizing antibodies in a patient plasma during the course of therapy.

Materials and methods

Besides the standard of care treatment and monitoring, neutralizing antibody titers in patient's serum samples, calibrated according to the First WHO International Standard for anti-SARS-CoV-2 immunoglobulin (human), were quantified in a time-dependent manner. During the immunotherapy period peripheral blood flow cytometry immunophenotyping was conducted to characterize lymphocyte subpopulations.

Results

The waves of clinical improvements and worsening coincided with transfused neutralizing antibodies rises and drops in the patient's systemic circulation, proving their contribution in controlling the disease progress. Besides the patient's lack of own humoral immune system, immunophenotyping analysis revealed also the reduced level of helper T-lymphocytes and immune exhaustion of monocytes.

Conclusion

Therapeutic approach based on convalescent plasma transfusion transformed a prolonged, active COVID-19 infection into a manageable chronic disease.

Intravenous Vipera berus Venom-Specific Fab Fragments and Intramuscular Vipera ammodytes Venom-Specific F(ab')2 Fragments in Vipera ammodytes-Envenomed Patients

Vipera ammodytes (V. ammodytes) is the most venomous European viper. The aim of this study was to compare the clinical efficacy and pharmacokinetic values of intravenous Vipera berus venom-specific (paraspecific) Fab fragments (ViperaTAb) and intramuscular V. ammodytes venom-specific F(ab’)₂ fragments (European viper venom antiserum, also called “Zagreb” antivenom) in V.ammodytes-envenomed patients. This was a prospective study of V.ammodytes-envenomed patients that were treated intravenously with ViperaTAb or intramuscularly with European viper venom antiserum that was feasible only due to the unique situation of an antivenom shortage. The highest venom concentration, survival, length of hospital stay and adverse reactions did not differ between the groups. Patients treated with intravenous Fab fragments were sicker, with significantly more rhabdomyolysis and neurotoxicity. The kinetics of Fab fragments after one or more intravenous applications matched better with the venom concentration in the early phase of envenomation compared to F(ab’)₂ fragments that were given intramuscularly only on admission. F(ab’)₂ fragments given intramuscularly had 25-fold longer apparent total body clearance and 14-fold longer elimination half-time compared to Fab fragments given intravenously (2 weeks vs. 24 h, respectively). In V.ammodytes-envenomed patients, the intramuscular use of specific F(ab’)₂ fragments resulted in a slow rise of antivenom serum concentration that demanded their early administration but without the need for additional doses for complete resolution of all clinical signs of envenomation. Intravenous use of paraspecific Fab fragments resulted in the immediate rise of antivenom serum concentration that enabled their use according to the clinical progress, but multiple doses might be needed for efficient therapy of thrombocytopenia due to venom recurrence, while the progression of rhabdomyolysis and neurotoxic effects of the venom could not be prevented.

Comparison of Preclinical Properties of Several Available Antivenoms in the Search for Effective Treatment of Vipera ammodytes and Vipera berus Envenoming

Snakebites are a relatively rare medical emergency in Europe. In more than half of the annual cases caused by Vipera ammodytes, Vipera berus, and Vipera aspis, immunotherapy with animal-derived antivenom is indicated. Among eight products recently identified as available against European medically relevant species, only Zagreb antivenom, Viperfav, and ViperaTAb have been used almost exclusively for decades. Zagreb antivenom comprises V. ammodytes-specific F(ab')₂ fragments. Viperfav is a polyspecific preparation based on F(ab')₂ fragments against V. aspis, V. berus, and V. ammodytes venoms. ViperaTAb contains Fab fragments against the venom of V. berus. In 2014 the production of Zagreb antivenom was discontinued. Additionally, in the period of 2017 to 2018 a shortage of Viperfav occurred. Due to a lack of the product indicated for the treatment of V. ammodytes bites, other antivenoms were implemented into clinical practice without comparative assessment of their eligibility. The aim of our work was to identify a high-quality antivenom that might ensure the successful treatment of V. ammodytes and V. berus bites at the preclinical level. Differentiation between bites from these two species is difficult and unreliable in clinical practice, so the availability of a unique antivenom applicable in the treatment of envenoming caused by both species would be the most advantageous for Southeastern Europe. Zagreb antivenom, Viperfav, and ViperaTAb, as well as Viper venom antitoxin for V. berus envenoming and the in-development Inoserp Europe, which was designed to treat envenoming caused by all medically important European snakes, were comparatively tested for the first time. Emphasis was placed on their physicochemical properties, primarily purity and aggregate content, as well as their in vivo protective efficacies. As Zagreb antivenom is no longer available on the European market, Viperfav is the highest-quality product currently available and the only antivenom whose neutralisation potency against V. ammodytes and V. berus venoms was above regulatory requirements.

Streamlined downstream process for efficient and sustainable (Fab')2 antivenom preparation

BACKGROUND

Antivenoms are the only validated treatment against snakebite envenoming. Numerous drawbacks pertaining to their availability, safety and efficacy are becoming increasingly evident due to low sustainability of current productions. Technological innovation of procedures generating therapeutics of higher purity and better physicochemical characteristics at acceptable cost is necessary. The objective was to develop at laboratory scale a compact, feasible and economically viable platform for preparation of equine F(ab')2 antivenom against Vipera ammodytes ammodytes venom and to support it with efficiency data, to enable estimation of the process cost-effectiveness.

METHODS

The principle of simultaneous caprylic acid precipitation and pepsin digestion has been implemented into plasma downstream processing. Balance between incomplete IgG breakdown, F(ab')2 over-digestion and loss of the active drug's protective efficacy was achieved by adjusting pepsin to a 1:30 substrate ratio (w/w) and setting pH at 3.2. Precipitation and digestion co-performance required 2 h-long incubation at 21 °C. Final polishing was accomplished by a combination of diafiltration and flow-through chromatography. In vivo neutralization potency of the F(ab')2 product against the venom's lethal toxicity was determined.

RESULTS

Only three consecutive steps, performed under finely tuned conditions, were sufficient for preservation of the highest process recovery with the overall yield of 74%, comparing favorably to others. At the same time, regulatory requirements were met. Final product was aggregate- and pepsin-free. Its composition profile was analyzed by mass spectrometry as a quality control check. Impurities, present in minor traces, were identified mostly as IgG/IgM fragments, contributing to active drug. Specific activity of the F(ab')2 preparation with respect to the plasma was increased 3.9-fold.

CONCLUSION

A highly streamlined mode for production of equine F(ab')2 antivenom was engineered. In addition to preservation of the highest process yield and fulfillment of the regulatory demands, performance simplicity and rapidity in the laboratory setting were demonstrated. Suitability for large-scale manufacturing appears promising.

Refinement strategy for antivenom preparation of high yield and quality

Antivenoms from hyperimmune animal plasma are the only specific pharmaceuticals against snakebites. The improvement of downstream processing strategies is of great interest, not only in terms of purity profile, but also from yield-to-cost perspective and rational use of plasma of animal origin. We report on development of an efficient refinement strategy for F(ab')2-based antivenom preparation. Process design was driven by the imperative to keep the active principle constantly in solution as a precautionary measure to preserve stability of its conformation (precipitation of active principle or its adsorption to chromatographic stationary phase has been completely avoided). IgG was extracted from hyperimmune horse plasma by 2% (V/V) caprylic acid, depleted from traces of precipitating agent and digested by pepsin. Balance between incomplete IgG fraction breakdown, F(ab')2 over-digestion and loss of the active principle's protective efficacy was achieved by adjusting pepsin to substrate ratio at the value of 4:300 (w/w), setting pH to 3.2 and incubation period to 1.5 h. Final polishing was accomplished by a combination of diafiltration and flow-through chromatography. Developed manufacturing strategy gave 100% pure and aggregate-free F(ab')2 preparation, as shown by size-exclusion HPLC and confirmed by MS/MS. The overall yield of 75% or higher compares favorably to others so far reported. This optimised procedure looks also promising for large-scale production of therapeutic antivenoms, since high yield of the active drug and fulfillment of the regulatory demand considering purity was achieved. The recovery of the active substance was precisely determined in each purification step enabling accurate estimation of the process cost-effectiveness.

Concept of sample-specific correction of immunoassay results for precise and accurate IgG quantification in horse plasma

The hyperimmune horse plasma (HHP), prepared through active immunisation of horses with an antigen of interest, is the most common starting material for antitoxin (animal antibody-based therapeutics) production. Precise IgG quantification in plasma is a prerequisite for accurate estimation of the purification process efficiency. Although immunoglobulins from HHP have been purified for over a century, there is still no in vitro method for precise and accurate determination of IgG content in HHP. For this reason, the purification process efficiency has been assessed by antibody activity measurements, mostly performed in vivo. Here we describe the development of a precise and accurate in vitro immunoassay for IgG quantification in HHP. We showed and highlighted that any difference in composition of IgG population between the standard and the sample, with respect to both IgG subclass distribution and antigen-specific IgG content, leads to inaccurate IgG quantification. We demonstrated that caprylic acid precipitation as the method for IgG isolation from horse plasma renders the composition of IgG population unchanged. This very efficient, fast, simple and inexpensive method was used to prepare internal, sample-specific reference IgG for each plasma sample, which was tested simultaneously to a respective plasma sample. Deviation of IgG quantity determined by ELISA for each sample-specific reference from its nominal value was used for correction of the results of respective plasma sample, which led to accurate and precise IgG quantification as shown by method validation. The here presented novel concept of sample-specific correction of immunoassay results could be widely applicable and easily introduced in different immunoassays for more accurate and precise plasma IgG quantification.

Mass spectrometry-based investigation of measles and mumps virus proteome

Background

Measles (MEV) and mumps virus (MUV) are enveloped, non-segmented, negative single stranded RNA viruses of the family Paramyxoviridae, and are the cause of measles and mumps, respectively, both preventable by vaccination. Aside from proteins coded by the viral genome, viruses are considered to contain host cell proteins (HCPs). The presence of extracellular vesicles (ECVs), which are often co-purified with viruses due to their similarity in size, density and composition, also contributes to HCPs detected in virus preparations, and this has often been neglected. The aim was to identify which virus-coded proteins are present in MEV and MUV virions, and to try to detect which HCPs, if any, are incorporated inside the virions or adsorbed on their outer surface, and which are more likely to be a contamination from co-purified ECVs.

Methods

MUV, MEV and ECVs were purified by ultracentrifugation, hydrophobic interaction chromatography and immunoaffinity chromatography, proteins in the samples were resolved by SDS-PAGE and subjected to identification by MALDI-TOF/TOF-MS. A comparative analysis of HCPs present in all samples was carried out.

Results

By proteomics approach, it was verified that almost all virus-coded proteins are present in MEV and MUV particles. Protein C in MEV which was until now considered to be non-structural viral protein, was found to be present inside the MeV virions. Results on the presence of HCPs in differently purified virus preparations imply that actin, annexins, cyclophilin A, moesin and integrin β1 are part of the virions.

Conclusions

All HCPs detected in the viruses are present in ECVs as well, indicating their possible function in vesicle formation, or that most of them are only present in ECVs. Only five HCPs were constantly present in purified virus preparations, regardless of the purification method used, implying they are likely the integral part of the virions. The approach described here is helpful for further investigation of HCPs in other virus preparations.

Electronic supplementary material

The online version of this article (10.1186/s12985-018-1073-9) contains supplementary material, which is available to authorized users.

Recovery of infective virus particles in ion-exchange and hydrophobic interaction monolith chromatography is influenced by particle charge and total-to-infective particle ratio

Viral particles are used in medical applications as vaccines or gene therapy vectors. In order to obtain product of high purity, potency and safety for medical use purification of virus particles is a prerequisite, and chromatography is gaining increased attention to meet this aim. Here, we report on the use of ion-exchange and hydrophobic interaction chromatography on monolithic columns for purification of mumps virus (MuV) and measles virus (MeV). Efficiency of the process was monitored by quantification of infective virus particles (by 50% cell culture infective dose assay) and total virus particles, and monitoring of their size (by Nanoparticle Tracking Analysis). Ion-exchange chromatography was shown to be inefficient for MuV and best results for MeV were obtained on QA column with recovery around 17%. Purification of MuV and MeV by hydrophobic interaction chromatography resulted in recoveries around 60%. Results showed that columns with small channels (d=1.4μm) are not suitable for MuV and MeV, although their size is below 400nm, whereas columns with large channels (6μm) showed to be efficient and recoveries independent on the flow rate up to 10mL/min. Heterogeneity of the virus suspension and its interday variability mostly regarding total-to-infective particle ratio was observed. Interestingly, a trend in recovery depending on the day of the harvest was also observed for both viruses, and it correlated with the total-to-infective particle ratio, indicating influence of the virus sample composition on the chromatography results.

Optimization of tetanus toxoid ammonium sulfate precipitation process using response surface methodology

Tetanus toxoid (TTd) is a highly immunogenic, detoxified form of tetanus toxin, a causative agent of tetanus disease, produced by Clostridium tetani. Since tetanus disease cannot be eradicated but is easily prevented by vaccination, the need for the tetanus vaccine is permanent. The aim of this work was to investigate the possibility of optimizing TTd purification, i.e., ammonium sulfate precipitation process. The influence of the percentage of ammonium sulfate, starting amount of TTd, buffer type, pH, temperature, and starting purity of TTd on the purification process were investigated using optimal design for response surface models. Responses measured for evaluation of the ammonium sulfate precipitation process were TTd amount (Lf/mL) and total protein content. These two parameters were used to calculate purity (Lf/mgPN) and the yield of the process. Results indicate that citrate buffer, lower temperature, and lower starting amount of TTd result in higher purities of precipitates. Gel electrophoresis combined with matrix-assisted laser desorption ionization-mass spectrometric analysis of precipitates revealed that there are no inter-protein cross-links and that all contaminating proteins have pIs similar to TTd, so this is most probably the reason for the limited success of purification by precipitation.

Vipera ammodytes bites treated with antivenom ViperaTAb: a case series with pharmacokinetic evaluation

CONTEXT

In clinical practice it is difficult to differentiate between V. berus and V. ammodytes venomous bites. In the past this was not a concern, but due to the current shortage in Viperfav™ and European viper venom antiserum availability, V. a. ammodytes venomous bites have recently been treated with ViperaTAb^®, which is a pharmaceutical formulation containing a monospecific ovine Fab fragments against the venom of V. berus.

OBJECTIVE

To evaluate ViperaTAb^® in V. a. ammodytes envenomations.

MATERIALS AND METHODS

This is a prospective case series of three consecutive patients envenomed by V. a. ammodytes snakebite treated with ViperaTAb^®. V. ammodytes venom, neurotoxic ammodytoxins, and Fab fragment levels were determined in serum samples and a pharmacokinetic analysis of the antivenom Fab fragments was carried out.

RESULTS

Three patients bitten by V. a. ammodytes with extensive local swelling, neurological symptoms and recurrent thrombocytopenia were treated with ViperaTAb^®. V. ammodytes venom was detected in serum of all three patients. Ammodytoxins were detected in the serum of only the most severely envenomed patient who developed neurological symptoms. In the presented moderate cases, a dose of 8 mL of ViperaTAb^® reduced swelling and improved systemic effects, such as thrombocytopenia. However, this dose of ViperaTAb^® was not effective in the most severely envenomed patient with the highest serum values of V. ammodytes venom. In this case ViperaTAb^® did not stop local swelling and it had no effect on neurological signs. ViperaTAb^®'s systemic clearance, distribution and elimination half-lives were 4.3-13.4 mL/h/kg, 1.2-3.2 h and 14.1-55.4 h, respectively.

CONCLUSIONS

In patients envenomed by V. a. ammodytes venom, ViperaTAb^® reduces moderate swelling and temporarily improves systemic effects, except neurological symptoms. ViperaTAb^® application induces a decrement of V. ammodytes venom level in the blood, but did not affect serum concentration of neurotoxic ammodytoxins in the one patient with measurable concentrations.

A Single Dose of Viperfav(TM) May Be Inadequate for Vipera ammodytes Snake Bite: A Case Report and Pharmacokinetic Evaluation

Viperfav^TM is a commercial F(ab’)₂ antivenom prepared against European vipers venom. It is safe and effective for treating envenomation caused by Vipera aspis and Vipera berus. Therapeutic efficacy for treating Vipera ammodytes ammodytes (V. a. ammodytes) envenoming has not been yet described, although protective efficacy has been demonstrated in preclinical studies. We report on a 32-year-old man bitten by V. a. ammodytes who was treated with Viperfav™. Viperfav™ promptly reduced local extension and improved systemic pathological signs, but 24 h after the incident a recurrence of thrombocytopenia occurred despite a favorable pharmacokinetic profile with systemic clearance (1.64 (mL·h⁻¹)·kg⁻¹) and elimination half-life (97 h) among the highest ever reported. The recommended dose of Viperfav™ for V. aspis and V. berus bites may be inadequate for serious V. a. ammodytes envenomations. Following V. a. ammodytes bite, serial blood counts and coagulation profiles should be performed to help guide Viperfav™ treatment, along with supplemental administration as indicated.

Factors influencing preclinical in vivo evaluation of mumps vaccine strain immunogenicity

Immunogenicity testing in animals is a necessary preclinical assay for demonstration of vaccine efficacy the results of which are often the basis for the decision whether to proceed or withdraw the further development of the novel vaccine candidate. However, in vivo assays are rarely, if at all, optimized and validated. Here we clearly demonstrate the importance of in vivo assay (mumps virus immunogenicity testing in guinea pigs) optimization for gaining reliable results and the suitability of Fractional factorial design of experiments (DoE) for such a purpose. By the use of DoE with resolution IV (2IV((4-1))) we clearly revealed that the parameters significantly increasing assay sensitivity were interval between animal immunizations followed by the body weight of experimental animals. The quantity (0 versus 2%) of the stabilizer (fetal bovine serum, FBS) in the sample was shown as non-influencing parameter in DoE setup. However, the separate experiment investigating only the FBS influence, and performed under other parameters optimally set, showed that FBS also influences the results of immunogenicity assay. Such finding indicated that (a) factors with strong influence on the measured outcome can hide the effects of parameters with modest/low influence and (b) the matrix of mumps virus samples to be compared for immunogenicity must be identical for reliable virus immunogenicity comparison. Finally the 3 mumps vaccine strains widely used for decades in the licensed vaccines were for the first time compared in an animal model, and results obtained were in line with their reported immunogenicity in human population supporting the predictive power of the optimized in vivo assay.

Venomics of Vipera berus berus to explain differences in pathology elicited by Vipera ammodytes ammodytes envenomation: Therapeutic implications

Vipera berus berus (Vbb) is the most widely distributed and Vipera ammodytes ammodytes (Vaa) the most venomous viper in Europe. In particular areas of the Old continent their toxic bites constitute a considerable public health problem. To make the current envenomation therapy more effective we have analysed the proteome of Vbb venom and compared it with that of Vaa. We found the proteome of Vbb to be much less complex and to contain smaller levels of particularly snaclecs and sPLA2s. Snaclecs are probably responsible for thrombocytopenia. The neurotoxic sPLA2s, ammodytoxins, are responsible for the most specific feature of the Vaa venom poisoning - induction of signs of neurotoxicity in patients. These molecules were not found in Vbb venom. Both venoms induce haemorrhage and coagulopathy in man. As Vaa and Vbb venoms possess homologous P-III snake venom metalloproteinases, the main haemorrhagic factors, the severity of the haemorrhage is dictated by concentration and specific activity of these molecules. The much greater anticoagulant effect of Vaa venom than that of Vbb venom lies in its higher extrinsic pathway coagulation factor-proteolysing activity and content of ammodytoxins which block the prothrombinase complex formation.

BIOLOGICAL SIGNIFICANCE

Envenomations by venomous snakes constitute a considerable public health problem worldwide, and also in Europe. In the submitted work we analysed the venom proteome of Vipera berus berus (Vbb), the most widely distributed venomous snake in Europe and compared it with the venom proteome of the most venomous viper in Europe, Vipera ammodytes ammodytes (Vaa). We have offered a possible explanation, at the molecular level, for the differences in clinical pictures inflicted by the Vbb and Vaa venoms. We have provided an explanation for the effectiveness of treatment of Vbb envenomation by Vaa antiserum and explained why full protection of Vaa venom poisoning by Vbb antiserum should not be always expected, especially not in cases of severe poisoning. The latter makes a strong case for Vaa antiserum production as we are faced with its shortage due to ceasing of production of two most frequently used products.

Nonspecific native elution of proteins and mumps virus in immunoaffinity chromatography

Immunoaffinity chromatography, based on the antigen-antibody recognition, enables specific purification of any antigen (protein, virus) by its antibody. The problem with immunoaffinity chromatography is the harsh elution conditions required for disrupting strong antigen-antibody interactions, such as low pH buffers, which are often deleterious for the immobilized protein and the protein to be isolated since they can also disrupt the intramolecular forces. Therefore, immunoaffinity chromatography can only be partially used for protein and virus purification. Here we report on a nonspecific elution in immunoaffinity chromatography using native conditions by elution with amino acid solution at physiological pH for which we suppose possible competing mechanism of action. Elution potential of various amino acid solutions was tested using immunoaffinity columns specific for ovalbumin and mumps virus, and protein G affinity column. Results have shown that the most successful elution solutions were those containing imidazole and arginine of high molarity. Imidazole represents aromatic residues readily found at the antigen-antibody interaction surface and arginine is most frequently found on protein surface in general. Therefore, results on their eluting power in immunoaffinity chromatography, which increases with increasing molarity, are in line with the competing mechanism of action. Virus immunoaffinity chromatography resulted in removal on nonviable virus particles, which is important for research and biotechnology purposes. In addition, amino acids are proven stabilizers for proteins and viruses making approach presented in this work a very convenient purification method.

Identification of mumps virus protein and lipid composition by mass spectrometry

Background

Mumps virus is a negative-sense, single stranded RNA virus consisting of a ribonucleocapsid core enveloped by a lipid membrane derived from host cell, which causes mumps disease preventable by vaccination. Since virus lipid envelope and glycosylation pattern are not encoded by the virus but dependent on the host cell at least to some extent, the aim of this work was to analyse L-Zagreb (L-Zg) mumps virus lipids and proteins derived from two cell types; Vero and chicken embryo fibroblasts (CEF). Jeryl Lynn 5 (JL5) mumps strain lipids were also analysed.

Methods

Virus lipids were isolated by organic phase extraction and subjected to 2D-high performance thin layer chromatography followed by lipid extraction and identification by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Virus samples were also subjected to gel electrophoresis under denaturating conditions and protein bands were excised, in-gel trypsinized and identified by MS as well as tandem MS.

Results

Results showed that lipids of both mumps virus strains derived from Vero cells contained complex glycolipids with up to five monosaccharide units whereas the lipid pattern of mumps virus derived from CEF was less complex. Mumps virus was found to contain expected structural proteins with exception of fusion (F) protein which was not detected but on the other hand, V protein was detected. Most interesting finding related to the mumps proteins is the detection of several forms of nucleoprotein (NP), some of which appear to be C-terminally truncated.

Conclusions

Differences found in lipid and protein content of mumps virus demonstrated the importance of detailed biochemical characterization of mumps virus and the methodology described here could provide a means for a more comprehensive quality control in vaccine production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0463-0) contains supplementary material, which is available to authorized users.

Stability of Minimum Essential Medium functionality despite L-glutamine decomposition

L-Glutamine (L-Gln) instability in liquid media is a well-known fact. Also, negative effect of ammonia, one of the L-Gln degradation products, on viability of many cell cultures and on replication of different viruses has been described. However, negative effects of ammonia have been reported in doses excessively exceeding those that could be generated in regularly used liquid culture media due to spontaneous L-Gln breakdown (below 2 mM). Traditional virus vaccine production processes have been established and registered involving L-Gln containing media use. Eventual culture media replacement in the regular production process belongs to the major regulative changes that require substantial financial expenses. The aim of this study was to evaluate the effect of storage of Minimum Essential Media with Hanks salts on their relevant biological functions during virus vaccine production process in relation to L-Gln decrease. Our results show a cell type dependent effect of spontaneous L-Gln degradation during medium storage. They also suggest that for cell cultures used in measles, mumps, and rubella virus production the media retain their functionality in respect to cell viability or virus growth over a certain time window despite L-Gln degradation.

Structural and biochemical characterisation of VaF1, a P-IIIa fibrinogenolytic metalloproteinase from Vipera ammodytes ammodytes venom

A high molecular mass metalloproteinase with α-fibrinogenolytic activity, termed VaF1, was purified from nose-horned viper (Vipera ammodytes ammodytes) venom. Subcutaneous injection of 9 μg of VaF1 did not induce bleeding in rats. Nevertheless, in vitro it degraded collagen IV, nidogen and fibronectin, components of the extracellular matrix, although with low efficacy and narrow specificity. VaF1 would be expected to exert anti-coagulant action, due to its hydrolysis of fibrinogen, factor X, prothrombin and plasminogen, plasma proteins involved in blood coagulation. The enzyme is a single-chain glycoprotein with a molecular mass of 49.7 kDa, as determined by mass spectrometry, and multiple isoelectric points centred at pH 5.8. The complete amino acid sequence of the precursor of VaF1 was deduced by cloning and sequencing its cDNA. Composed of metalloproteinase, disintegrin-like and cysteine-rich domains, VaF1 is a typical P-IIIa subclass snake venom metalloproteinase. Although it possesses a collagen-binding sequence in its disintegrin-like domain, VaF1 displayed no effect on collagen-induced platelet aggregation in vitro. Two consensus N-glycosylation sites are present in the sequence of VaF1, however, the extent of its glycosylation is low, only 5.2% of the total molecular mass. Interestingly, in standard experimental conditions VaF1 is not recognised by antiserum against the whole venom, so it can contribute to post-serotherapy complications, such as ineffective blood coagulation, in the envenomed patient.

Paraspecificity of Vipera a. ammodytes-specific antivenom towards Montivipera raddei and Macrovipera lebetina obtusa venoms

Antivenom raised against the venom of nose-horned viper, Vipera ammodytes (V. a.) ammodytes (European viper venom antiserum, Zagreb antivenom), contains neutralising equine F(ab')₂ fragments that are clinically successful against homologous venom, but also against the venoms of several others medically important European snakes due to its paraspecific action. In this work we demonstrated that Zagreb antivenom is preclinically effective in neutralising lethal toxicity and hemorrhagicity of venoms of Armenian mountain snakes--Montivipera raddei and Macrovipera lebetina obtusa as well. In order to better understand the biochemical basis of the observed paraspecificity, the ability of anti-V. a. ammodytes serum to recognise and neutralise proteinases of the two venoms was also investigated. Anti-V. a. ammodytes serum showed surprisingly low capacity to inhibit metalloproteinases of both venoms included in the study, probably due to weak immunorecognition of their P-I representatives. Also, it completely failed to abolish enzymatic action of serine proteinases from Macrovipera lebetina obtusa venom. Relevance of such finding is yet to be established.

Hemorrhagin VaH4, a covalent heterodimeric P-III metalloproteinase from Vipera ammodytes ammodytes with a potential antitumour activity

In the envenomation caused by a bite of Vipera ammodytes ammodytes, the most venomous snake in Europe, hemorrhage is usually the most severe consequence in man. Identifying and understanding the hemorrhagic components of its venom is therefore particularly important in optimizing medical treatment of patients. We describe a novel high molecular mass hemorrhagin, VaH4. The isolated molecule is a covalent dimer of two homologous subunits, VaH4-A and VaH4-B. Complete structural characterization of A and partial characterization of B revealed that both belong to the P-III class of snake venom metalloproteinases (SVMPs), comprising a metalloproteinase, a disintegrin-like domain and a cysteine-rich domain. However, neither VaH4-A nor VaH4-B possess the Cys174 involved in the inter-subunit disulphide bond of P-III SVMPs. A three-dimensional model of the VaH4 dimer suggests that Cys132 serves this function. This implies that dimers in the P-III class of SVMPs can be formed either between their Cys132 or Cys174 residues. The proteolytic activity and stability of VaH4 depend on Zn²⁺ and Ca²⁺ ions and the presence of glycosaminoglycans, which indicates physiological interaction of VaH4 with the latter element of the extracellular matrix (ECM). The molecular mass of VaH4, determined by MALDI/TOF mass spectrometry, is 110.2 kDa. N-deglycosylation reduced the mass of each monomer by 8.7 kDa. The two possible N-glycosylation sites in VaH4-A are located at completely different positions from those in homodimeric P-IIIc VaH3 from the same venom, however, without any evident functional implications. The hemorrhagic activity of this slightly acidic SVMP is ascribed to its hydrolysis of components of the ECM, particularly fibronectin and nidogen, and of some blood coagulation proteins, in particular the α-chain of fibrinogen. VaH4 is also significant medically as we found it cytotoxic against cancer cells and due to its substantial sequence similarity to ADAM/ADAMTS family of physiologically very important human proteins of therapeutic potential.

Influence of charge ratio of liposome/DNA complexes on their size after extrusion and transfection efficiency

BACKGROUND

Physicochemical characteristics of liposome/DNA complexes influence transfection efficiency and affect each other in a very intricate way. The result of this is discrepancies in conclusions drawn about the individual influence of each one.

METHODS

Aiming to elucidate the influence of liposome/DNA charge ratio and size on transfection efficiency and on each other, we used liposome/DNA complexes with charge ratio (+/-) in the range of 1-50 and extruded through membranes of 400, 200, and 100 nm. Plasmid DNA encoding green fluorescent protein was used to measure transfection efficiency by flow cytometry. Sizes of liposome/DNA complexes were measured by dynamic light scattering.

RESULTS

Liposome size was reduced after extrusion but this was mainly driven by the charge ratio and not by the size of the membrane pores. Reduction of complex size at each charge ratio positively correlated with transfection efficiency. When the size of the complexes was approximately constant, increasing the charge ratio was found to promote transfection efficiency. Cationic lipid N-(1-(2,3-dioleoyloxy)propyl)N,N,N trimethylammonium chloride was used for modulation of positive charge and a cytotoxicity test showed that increasing its amount increases cytotoxicity.

CONCLUSION

It can be concluded that charge ratio dictates the size of the complex whereas overall size reduction and higher charge ratios promote transfection efficiency in vitro.

Intraspecies variability in Vipera ammodytes ammodytes venom related to its toxicity and immunogenic potential

Vipera ammodytes is the most venomous European snake, whose venom has been used as antigen for immunization of antivenom-producing animals. Same as venom of any other snake, it is a complex mixture of proteins, peptides and other compounds which biochemical and pharmacological variability has been demonstrated at interspecies and intraspecies level. In this work we demonstrated intraspecific variability between 8 venom production batches using both the conventional and the new methodology. Moreover, in contrast to the literature on different venoms' variability, for the first time we were able to select those biochemical differences that are related to and give information on the venom's toxicity and immunogenicity. We have shown that methods quantifying ammodytoxin (the most toxic compound identified so far in the Vipera ammodytes ammodytes venom) content of the venom clearly distinguish between high and low immunogenic venoms.

Studying disulfide bond rearrangement by MALDI-RTOF PSD and MALDI-TOF/RTOF high-energy CID (20 keV) experiments of peptides derived from ammodytoxins

Ammodytoxins (Atxs) are presynaptically neurotoxic phospholipases present in Vipera ammodytes ammodytes snake venom. Atxs show a high sequence homology and contain 14 cysteines which form seven biologically relevant disulfide bridges-connecting non-neighboring cysteines. Formic acid cleavage was performed to confirm protein sequences by MALDI RTOF MS and resulted in 95.6% sequence coverage exhibiting only few formylations. Cysteine-containing peptides showed adjacent signals 2 and/or 4 Da lower (according to the number of cysteines present in the peptide) than the theoretical molecular weight indicating disulfide bridge rearrangement. Post-source decay (PSD) and high-energy collision-induced dissociation (CID) at 20 keV experiments showed fragmentation pattern unique for the reduced, thiol group containing and the oxidized, disulfide bridge harboring peptides. Besides typical low-energy fragment ions observed during PSD experiments (a-, b-, y-type ions), additional high-energy fragment ions (c-, x-, w-, d-type and internal fragments) of significant intensity were generated during fragmentation at 20 keV. In the case of charge directing N- and C-termini, x- and w-type ions were also observed during PSD. Good and up to complete sequence coverage was achieved for all studied peptides from Atxs in the case of high-energy CID, whereas PSD lacked information particularly for larger peptides.

Ammodytoxin content of Vipera ammodytes ammodytes venom as a prognostic factor for venom immunogenicity

Venoms are complex mixtures of proteins, peptides and other compounds whose biochemical and biological variability has been clearly demonstrated. These molecules have been used as antigens for immunization of anti-venom-producing animals (horses or sheep). Ammodytoxins (Atx) are potently neurotoxic compounds, and the most toxic compounds isolated so far from the Vipera ammodytes ammodytes (Vaa) venom. Recently we have shown that the level of antibodies specific to Vaa venom's most toxic component, ammodytoxin A (AtxA), (anti-AtxA IgG) in Vaa venom immunized rabbit sera highly correlated to the venom toxicity-neutralization potential of these sera. Here we investigated whether Atx content of Vaa venom could influence the outcome of immunization procedure. The novel ELISA was developed for precise determination of Atx content and Atx was quantified in venom samples used for immunization of rabbits. We clearly showed that animals immunized with the venom containing lower amount of Atx produced sera with significantly lower venom toxicity-neutralizing power and, vice versa, animals immunized with venoms containing higher amount of Atx produced sera with higher venom toxicity-neutralizing ability. Thus, the content of Atx in Vaa venom is a relevant parameter of its suitability in the production of highly protective Vaa anti-venom.

Comparative study of structurally related peptidoglycan monomer and muramyl dipeptide on humoral IgG immune response to ovalbumin in mouse

Structurally related peptidoglycan monomer (PGM) and muramyl dipeptide (MDP) differ in several aspects of biological activity but have in common immunostimulating properties. Comparative study of the effects of these adjuvants on humoral IgG immune response specific for protein antigen ovalbumin (OVA) was carried out in two inbred mouse strains, CBA and NIH/OlaHsd, and their ability to modulate the bias of immune response towards Th1/Th2 was evaluated. MDP had better adjuvant activity at some points than PGM, whereas both adjuvants stimulated Th2-biased immune response specific for OVA. In comparison to Complete Freund's adjuvant (CFA), as a golden standard of adjuvant action, both PGM and MDP exhibited considerably lower activity. Addition of PGM to Incomplete Freund's adjuvant (IFA) on humoral immune response was studied also, and the effect of such adjuvant formulation was compared to the effect of CFA. While CFA induced the switch towards Th1-biased immune response, the addition of PGM into IFA did have no impact on modulating the immune response towards more pronounced Th2-type of immune response, defined by IFA itself.

Effect of Liposomal Formulations and Immunostimulating Peptidoglycan Monomer (PGM) on the Immune Reaction to Ovalbumin in Mice

The adjuvant activity of liposomes and immunostimulating peptidoglycan monomer (PGM) in different formulations has been studied in mice model using ovalbumin (OVA) as an antigen. PGM is a natural compound of bacterial origin with well-defined chemical structure: GlcNAc-MurNAc-L-Ala-D-isoGln-mesoDpm(epsilonNH2)-D-Ala-D-Ala. It is a non-toxic, non-pyrogenic, and water-soluble immunostimulator. The aim of this study was to investigate the influence of different liposomal formulations of OVA, with or without PGM, on the production of total IgG, as well as of IgG1 and IgG2a subclasses of OVA-specific antibodies (as indicators of Th2 and Th1 type of immune response, respectively). CBA mice were immunized s.c. with OVA mixed with liposomes, OVA with PGM mixed with liposomes, OVA encapsulated into liposomes and OVA with PGM encapsulated into liposomes. Control groups were OVA in saline, OVA with PGM in saline, and OVA in CFA/IFA adjuvant formulation. The entrapment efficacy of OVA was monitored by HPLC method. The adjuvant activity of the mixture of OVA and empty liposomes, the mixture of OVA, PGM, and liposomes and PGM encapsulated with OVA into liposomes on production of total anti-OVA IgG was demonstrated. The mixture of PGM and liposomes exhibited additive immunostimulating effect on the production of antigen-specific IgGs. The analysis of IgG subclasses revealed that encapsulation of OVA into liposomes favors the stimulation of IgG2a antibodies, indicating the switch toward the Th1 type of immune response. When encapsulated into liposomes or mixed with liposomes, PGM induced a switch from Th1 to Th2 type of immune response. It could be concluded that appropriate formulations of antigen, PGM, and liposomes differently affect the humoral immune response and direct the switch in the type of immune response (Th1/Th2).

The role of antibodies specific for toxic sPLA2s and haemorrhagins in neutralizing potential of antisera raised against Vipera ammodytes ammodytes venom

The contribution of antibodies directed against the two main toxic groups of proteins in the Vipera ammodytes ammodytes venom, haemorrhagic metalloproteinases (H) and neurotoxic sPLA2s (Atxs), to the overall protective efficacy of the whole venom antisera was investigated. Using ELISA assays we established a high correlation between the protective efficacy of the whole venom antisera in mice and their anti-Atxs antibody content. As the haemorrhage is the prevailing toxic effect of the venom in human, the lack of correlation also with anti-H IgG content exposed that the mouse model might not be optimal to evaluate the neutralizing potential of the venom-specific antisera for human therapy. We further revealed that Atxs and structurally very similar but non-toxic AtnI2 from the venom are not immuno cross-reactive.

Dose dependent effects of standardized nose-horned viper (Vipera ammodytes ammodytes) venom on parameters of cardiac function in isolated rat heart

Direct, dose dependent effects of the nose-horned vipers (Vipera ammodytes ammodytes) venom on various parameters of cardiac action in isolated rat hearts were examined. Biochemical (protein content, SDS polyacrylamide gel electrophoresis) and biological (minimum haemorrhagic and necrotizing dose and lethal dose (LD(50))) characterization of the venom was performed before testing. The hearts were infused with venom doses of 30, 90 and 150 microg/mL for 10 min followed by 30 min of wash out period. Left ventricular pressure, coronary flow, heart rate, atrioventricular conduction, myocardial oxygen consumption, incidence and duration of arrhythmias were measured and relative cardiac efficiency was calculated. Cardiac CPK, LDH, AST and troponin I were measured as biochemical markers of myocardial damage. The venom caused dose dependent electrophysiological instability and depression of contractility and coronary flow. Effects on the heart rate were biphasic; transient increase followed by significant slowing of the frequency. Relative cardiac efficiency decreased as oxygen consumption remained high relative to the heart rate-contractility product, indicating purposeless expenditure of oxygen and energy. Effects by the dose of 30 microg/mL were highly reversible while the dose of 90 mug/mL caused damages that were mostly irreversible. The dose of 150 mug/mL induced irreversible asystolic cardiac arrest.