Mapping of the antigenic regions of streptokinase in humans after streptokinase therapy

Evaluation of clinical efficacy of streptokinase by comparison with the thrombolytic agent on animal model

Cardiovascular disorders, including acute myocardial infarction (AMI), often lead to blood clot formation, impacting blood circulation. Streptokinase, a cost-effective and widely available thrombolytic agent, is crucial in treating thrombosis. This study aimed to produce streptokinase from Streptococcus pyogenes EBL-48 and compare its efficacy with heparin in an animal model. We evaluated the clot-lysing effectiveness of streptokinase produced from Streptococcus pyogenes EBL-48, emphasizing its low cost and ease of production. Streptokinase was produced using pre-optimized fermentation media and purified through ion exchange and gel-filtration chromatography. In vivo analysis involved inducing clots in a trial animal model using ferric chloride, comparing streptokinase with heparin. Ultrasonography assessed the clot-lysing activity of streptokinase. Streptokinase (47 kDa) effectively lysed clots, proving its low cost, easy production, and minimal adverse effects. Ultrasonography confirmed its fibrinolytic efficacy. These findings highlight potential as an affordable and easily produced thrombolytic agent, particularly relevant in resource-limited settings. Streptokinase efficacy and minimal adverse effects make it a promising option for thrombolytic therapy, especially in economically constrained regions. Future studies could optimize production techniques, explore different strains, and conduct clinical trials for human validation. Comparative studies with other thrombolytic agents would enhance understanding of their advantages and limitations.

Scoping review of the applications of peptide microarrays on the fight against human infections

INTRODUCTION

This scoping review explores the use of peptide microarrays in the fight against infectious diseases. The research domains explored included the use of peptide microarrays in the mapping of linear B-cell and T cell epitopes, antimicrobial peptide discovery, immunosignature characterisation and disease immunodiagnostics. This review also provides a short overview of peptide microarray synthesis.

METHODS

Electronic databases were systematically searched to identify relevant studies. The review was conducted using the Joanna Briggs Institute methodology for scoping reviews and data charting was performed using a predefined form. The results were reported by narrative synthesis in line with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines.

RESULTS

Ninety-five articles from 103 studies were included in the final data charting process. The majority (92. 0%) of the articles were published during 2010-2020 and were mostly from Europe (44.2%) and North America (34.7%). The findings were from the investigation of viral (45.6%), bacterial (32. 0%), parasitic (23.3%) and fungal (2. 0%) infections. Out of the serological studies, IgG was the most reported antibody type followed by IgM. The largest portion of the studies (77.7%) were related to mapping B-cell linear epitopes, 5.8% were on diagnostics, 5.8% reported on immunosignature characterisation and 8.7% reported on viral and bacterial cell binding assays. Two studies reported on T-cell epitope profiling.

CONCLUSION

The most important application of peptide microarrays was found to be B-cell epitope mapping or antibody profiling to identify diagnostic and vaccine targets. Immunosignatures identified by random peptide microarrays were found to be applied in the diagnosis of infections and interrogation of vaccine responses. The analysis of the interactions of random peptide microarrays with bacterial and viral cells using binding assays enabled the identification of antimicrobial peptides. Peptide microarray arrays were also used for T-cell linear epitope mapping which may provide more information for the design of peptide-based vaccines and for the development of diagnostic reagents.

Engineering, expression and purification of a chimeric fibrin-specific streptokinase

Streptokinase is a valuable fibrinolytic agent used to cope with myocardial infarction and brain stroke. Despite its high efficiency in dissolving blood clots, streptokinase (SK) has no specificity in binding fibrin, causing some problems such as internal bleedings following its administration. To make streptokinase fibrin specific and limit the fibrinolytic process to the clot location, we engineered a chimeric streptokinase by fusing the fibrin binding Kringle 2 domain of tissue plasminogen activator (TPA) to the streptokinase N-terminal end. The chimeric SK construct (KSK) with inserted Kringle 2 domain was cloned into pET28a expression vector. The expression of recombinant protein was carried out in Escherichia coli origami (DE3) and confirmed by SDS-PAGE and Western blotting analyses. We used the chromogenic substrate S-2251 method to assess the specific activities of the chimeric and control wild-type proteins. Then, the two proteins were added in amounts with equal activity to fibrin clots of identical size. Finally, the supernatant above the fibrin clots was collected and subjected to the chromogenic assay to analyze the specificity of the chimeric protein. The specific activities of the chimeric and wild-type proteins were found to be 0.06 U/mg and 0.07 U/mg, respectively. Because of the binding of the chimeric protein to fibrin, the mean specific activity was significantly lower in the KSK supernatant (0.01) compared with the control (approximately 0.06) (p < 0.05). Our in vitro results indicate that the chimeric streptokinase protein has strong fibrin-specific activity compared to the wild-type protein. However, further in vivo studies are needed to evaluate its potential fibrinolytic effects.

Profiling the immune responses of human patients treated with recombinant streptokinase after myocardial infarct

The SPOT synthesis of peptide arrays on continuous cellulose membranes should be generally applicable in the analysis of sequential antibody binding sites using the enzyme-substrate or other standard detection protocols. The use of total serum is limited by the occurrence of high background levels. This may be overcome if affinity purified antibodies or sera with high antibody titers are used, which allows work at high dilutions and a consequent reduction of background level. Here we demonstrate the mapping of antigenic regions located on recombinant streptokinase SK-2 (Heberkinase) using cellulose-bound peptide scans and human total sera from patients treated with SK-2 (Heberkinase). Streptokinase (SK) is a 47 kDa protein produced by various strains of hemolytic streptococci and is a potent activator of the fibrinolytic enzyme system in humans. SK is in widespread clinical use to treat acute infarction because of its function as an activator of vascular fibrinolysis. Since streptococcal infections are common, normal individuals are immunized with SK and antibodies (Abs) to SK can be detected in most of them. This therapy generates significant T-cell responses to SK and the neutralizing capacity of the Abs rises significantly. Neutralizing Abs reduces the efficiency of thrombolytic therapy and may cause allergic reactions. The widespread use of SK in humans makes its antigenicity an important clinical problem. In this regard the study of the immunodominant regions of SK becomes an important aspect for the improvement of this thrombolytic agent.

New antigenic regions of streptokinase are identified by affinity-directed mass spectrometry

Streptokinase (SK) is a bacterial protein used for the treatment of myocardial infarction, which is immunogenic in humans. Here we report the use of an affinity-directed MS approach to determine the minimal epitopes involved in the binding between SK and patient antibodies. Using this method we have identified two novel epitopes and mapped these to the minimal recognition regions formed by the amino acids D96-E99 and F323-D328. We have also located three previously identified antigenic regions and have now mapped them and shown that they can be defined more precisely as residues P4-L8, P171-P177 and K334-N338.

A mutant streptokinase lacking the C-terminal 42 amino acids is less reactive with preexisting antibodies in patient sera

Streptokinase (SK) is an efficacious thrombolytic drug for the treatment of myocardial infarction. Because of its immunogenicity, patients receiving SK therapy develop high anti-SK antibody (Ab) titers, which might provoke severe allergic reactions and neutralize SK activity. In this report we studied the reactivity of a synthetic 42-residue peptide resembling SKC-2 C-terminus with patient sera. SKC-2(373-414) peptide was recognized by 39 and 64% of patients, before and after SKC-2 therapy, respectively. An SKC-2 deletion mutant (mut-C42), lacking the same 42 C-terminal residues, was constructed and expressed in Escherichia coli. Recognition of mut-C42 by preexisting Abs from patient sera was 51 and 68% of reactivity to SKC-2, as assessed by direct binding and competition assays, respectively. For most of the patients, mut-C42-neutralizing activity titer (NAT) significantly decreased with respect to SKC-2-NAT. This study opens the possibility of producing a less immunogenic variant of SK, which could constitute a preferred alternative for thrombolytic therapy.

A mutant streptokinase lacking the C-terminal 42 amino acids is less immunogenic

Streptokinase (SK) is the most widely used compound for the treatment of myocardial infarction and the least expensive thrombolytic agent, but a drawback to its use is the widespread presence of anti-SK antibodies (Abs). Clinical failure of the activation of the fibrinolytic system by SK has been reported due to the presence of a high titer of anti-SK neutralizing Abs. Patients receiving SK therapy develop high anti-SK antibody titers, which might provoke severe allergic reactions. These Abs are sufficient to neutralize a standard dose of SK up to four years after initial SK administration. This is a clinical problem because of the increasing number of patients who have been treated once with SK for acute myocardial infarction (AMI) and are likely to require plasminogen activator treatment in the future. In previous in vitro studies, we have shown that a deletion mutant (mut-C42), lacking the 42 C-terminal residues, was significantly less antigenic when compared with the native molecule (SKC-2). In this study, 14 monkeys were subjected to treatment with SKC-2 and mut-C42 in order to compare their humoral response by determining SK neutralizing activity in monkey's sera. All monkeys developed anti-SKC-2 Ab titers, but in the case where treatment induced Abs directed against the C-terminus of SKC-2, neutralizing activity against the native protein was significantly higher than that developed against mutant SK mut-C42.

Crystal structure of streptokinase beta-domain

Streptokinase, a 47 kDa secreted protein of hemolytic strains of streptococci, is a human plasminogen activator and contains three structural domains linked by flexible loops. We describe here the crystal structure of the isolated streptokinase middle (SKbeta) domain determined at 2.4 A resolution. Among the functionally important structural features is a putative binding site for a kringle domain of plasminogen located at the tip of a fully exposed hairpin loop. The distribution of genetically conserved residues of SKbeta is strongly correlated with their functions. The extensive interface of the SKbeta dimer suggests that such dimers may also exist in solution for free SKbeta.

Prevalence of circulating antibodies against a streptokinase C-terminal peptide in normal blood donors

Streptokinase (SK) is a streptococcal protein widely used as a thrombolytic agent. Anti-SK antibodies (Abs) are found in most individuals due to common streptococcal infections. The presence of these Abs increases the possibility of allergic reactions and may reduce the thrombolytic efficacy of SK upon a first therapy. Previous studies report on the immunodominance of the SK C-terminus and the role of this region in plasminogen (Plg) activation. The aim of this study was to assess the prevalence of circulating Abs to the SK C-terminus in normal blood donors. Sera from 1008 subjects aged 30 to 60 years were tested by Ultra-Micro-ELISA using a synthetic peptide resembling the SKC-2 C-terminus. An overall prevalence of 30. 4% was found. Prevalence was significantly higher among male than among female donors (RR = 1.70, 1.13 < CI < 2.55). No age effect was observed. This is the first extensive study about Abs directed against a particular region of SK in normal subjects.