Ultrasensitive detection of protease activity of anthrax and botulinum toxins by a new PCR-based assay

New approach to generating of human monoclonal antibodies specific to the proteolytic domain of botulinum neurotoxin A

Introduction

Botulinum neurotoxins (BoNTs) cause botulism and are the most potent natural toxins known. Immunotherapy with neutralizing monoclonal antibodies (MAbs) is considered to be the most effective immediate response to BoNT exposure. Hybridoma technology remains the preferred method for producing MAbs with naturally paired immunoglobulin genes and with preserved innate functions of immune cells. The affinity-matured human antibody repertoire may be ideal as a source for antibody therapeutics against BoNTs. In an effort to develop novel BoNT type A (BoNT/A) immunotherapeutics, sorted by flow cytometry plasmablasts and activated memory B cells from a donor repeatedly injected with BoNT/A for aesthetic botulinum therapy could be used due to obtain hybridomas producing native antibodies.

Methods

Plasmablasts and activated memory B-cells were isolated from whole blood collected 7 days after BoNT/A injection and sorted by flow cytometry. The sorted cells were then electrofused with the K6H6/B5 cell line, resulting in a producer of native human monoclonal antibodies (huMAbs). The 3 antibodies obtained were then purified by affinity chromatography, analyzed for binding by Western blot assay and neutralization by FRET assay.

Results

We have succeeded in creating 3 hybridomas that secrete huMAbs specific to native BoNT/A and the proteolytic domain (LC) of BoNT/A. The 1B9 antibody also directly inhibited BoNT/A catalytic activity in vitro.

Conclusion

The use activated plasmablasts and memory B-cells isolated at the peak of the immune response (at day 7 of immunogenesis) that have not yet completed the terminal stage of differentiation but have undergone somatic hypermutation for hybridization allows us to obtain specific huMAbs even when the immune response of the donor is weak (with low levels of specific antibodies and specific B-cells in blood). A BoNT/A LC-specific antibody is capable of effectively inhibiting BoNT/A by mechanisms not previously associated with antibodies that neutralize BoNT. Antibodies specific to BoNT LC can be valuable components of a mixture of antibodies against BoNT exposure.

Identification of mycobacterial MPT-64 and ESAT-6 proteins in urogenital tuberculosis patients by real-time immuno-PCR

Aim: Diagnosis of urogenital tuberculosis (UGTB) is difficult and there is an immediate need to develop a reliable diagnostic test. Methods: A real-time immuno-PCR (RT-I-PCR) was developed to identify a cocktail of MPT-64 + ESAT-6 in both male/female UGTB patients comprising five confirmed cases, 40 clinically suspected cases and 37 non-TB controls, from whom mid-stream urine specimens were collected, while endometrial biopsies of female patients were obtained on day 1 of their menstrual cycle. Results obtained by RT-I-PCR were compared with I-PCR/ELISA and GeneXpert. Results: A wide range (500 fg/ml-10 ng/ml) of MPT-64 + ESAT-6 was detected in UGTB specimens by RT-I-PCR, although ELISA showed a narrow range (2.5-11 ng/ml). Sensitivities of 80% and 82.2% were obtained by RT-I-PCR in clinically suspected and total UGTB cases, respectively, whereas 94.6% specificity was obtained. Concurrently, RT-I-PCR revealed significantly higher (p < 0.05-0.001) sensitivity than I-PCR/ELISA and GeneXpert. Conclusion: After improving the specificity, the authors may develop RT-I-PCR into a diagnostic kit.

Diagnosis of peritoneal tuberculosis by real-time immuno-PCR assay based on detection of a cocktail of Mycobacterium tuberculosis CFP-10 and HspX proteins

BACKGROUND

Diagnosis of peritoneal TB is difficult owing to unusual clinical manifestations and low sensitivities obtained with most of the available diagnostic modalities. Hence, there is an urgent need to design a reliable diagnostic test so that an early therapy is initiated.

RESEARCH DESIGN AND METHODS

We designed a quantitative real-time immuno-PCR (RT-I-PCR) assay to detect a cocktail of Mycobacterium tuberculosis CFP-10 (Rv3874) and HspX (Rv2031c) proteins in clinical samples (ascitic fluids and peritoneal biopsies) of peritoneal TB patients, and results were compared with I-PCR/ELISA.

RESULTS

A wide range of CFP-10+ HspX (0.6 pg/mL to 9.9 ng/mL) was detected in clinical samples of peritoneal TB patients by RT-I-PCR, whereas ELISA exhibited a narrow range (3 ng/mL to 11.5 ng/mL). Sensitivities of 81.5% and 65.7% and specificities of 92.5% and 90% were obtained in a total of 78 cases (comprising 38 peritoneal TB and 40 non-TB controls) by RT-I-PCR and I-PCR, respectively. Markedly, sensitivity obtained by RT-I-PCR was significantly higher than I-PCR (p = 0.0143) and ELISA (p = 0.0005).

CONCLUSIONS

Our RT-I-PCR revealed good accuracy for the rapid diagnosis of peritoneal TB cases. After further improving the specificity and reducing the cost, this assay may develop into a diagnostic kit.

Novel Method for the Quantitative Analysis of Protease Activity: The Casein Plate Method and Its Applications

No simple methods are used for the quantitative analysis of the protease activity in colored food up till now. Thus, this study aims to establish a new and simple method for the quantitative detection of protease activity, especially in colored food. The detection accuracy, detection limit, and repeatability of the casein plate method were analyzed. Then, the application of the casein plate method in sample detection and recovery was further evaluated. The results showed that the casein plate method for the quantitative detection of protease activity has high accuracy, high precision, and low detection limit. The recoveries of eight kinds of colored samples were in the range of 92.26-97.84%, and the relative standard deviation (RSD) was in the range of 3.56-10.88%. The results of the casein plate method exhibited high accuracy. This indicated that the method was suitable for the detection of colored samples. The casein plate method for the quantitative detection of protease activity is simple. The newly constructed casein plate method has broad potential application value in food industry, especially for the detection of dark food.

Anthrax Toxin Detection: From In Vivo Studies to Diagnostic Applications

Anthrax toxins are produced by Bacillus anthracis throughout infection and shape the physiopathogenesis of the disease. They are produced in low quantities but are highly efficient. They have thus been long ignored, but recent biochemical methods have improved our knowledge in animal models. This article reviews the various methods that have been used and how they could be applied to clinical diagnosis.

Detection of Mycobacterium tuberculosis lipoarabinomannan and CFP-10 (Rv3874) from urinary extracellular vesicles of tuberculosis patients by immuno-PCR

Extracellular vesicles (EVs), the small circulating vesicles released from urine samples of tuberculosis (TB) patients, contain a pool of biomarkers. We recently detected Mycobacterium tuberculosis lipoarabinomannan (LAM) and CFP-10 (Rv3874) biomarkers from the urinary EVs of pulmonary TB (PTB) and extrapulmonary TB (EPTB) patients by immuno-polymerase chain reaction (I-PCR) assay and the results were compared with the analogous enzyme-linked immunosorbent assay (ELISA). The detection limits of both purified LAM and CFP-10 were determined to be 1 fg/mL with I-PCR, which was 106 times lower than ELISA. Detection of LAM and CFP-10 biomarkers in urinary EVs of TB patients by I-PCR showed superiority over ELISA. Notably, LAM I-PCR revealed sensitivities of 74.3 and 67.9% in PTB (n = 74) and EPTB (n = 53) patients, respectively, with specificities of 91.5-92.8% (n = 116). Moreover, the sensitivities attained with LAM I-PCR were significantly higher (P < 0.01) than with CFP-10 I-PCR. After further improving the sensitivity and specificity of the assay, our I-PCR based on LAM detection in urinary EVs may be used as an adjunct test for rapid diagnosis of TB.

Integration of a peptide–DNA conjugate with multiple cyclic signal amplification for the ultrasensitive detection of cathepsin B activity

We integrate a peptide–DNA conjugate with multiple cyclic signal amplification for the sensitive detection of cathepsin B activity.

Immunoproteomics Methods and Techniques

The varied landscape of the adaptive immune response is determined by the peptides presented by immune cells, derived from viral or microbial pathogens or cancerous cells. The study of immune biomarkers or antigens is not new, and classical methods such as agglutination, enzyme-linked immunosorbent assay, or Western blotting have been used for many years to study the immune response to vaccination or disease. However, in many of these traditional techniques, protein or peptide identification has often been the bottleneck. Recent progress in genomics and mass spectrometry have led to many of the rapid advances in proteomics approaches. Immunoproteomics describes a rapidly growing collection of approaches that have the common goal of identifying and measuring antigenic peptides or proteins. This includes gel-based, array-based, mass spectrometry-based, DNA-based, or in silico approaches. Immunoproteomics is yielding an understanding of disease and disease progression, vaccine candidates, and biomarkers. This review gives an overview of immunoproteomics and closely related technologies that are used to define the full set of protein antigens targeted by the immune system during disease.

Immuno-PCR, a new technique for the serodiagnosis of tuberculosis

Rapid and accurate diagnosis of tuberculosis (TB) is essential to control the disease. The conventional microbiological tests have limitations and there is an urgent need to devise a simple, rapid and reliable point-of-care (POC) test. The failure of TB diagnostic tests based on antibody detection due to inconsistent and imprecise results has stimulated renewed interest in the development of rapid antigen detection methods. However, the World Health Organization (WHO) has emphasized to continue research for designing new antibody-based detection tests with improved accuracy. Immuno-polymerase chain reaction (I-PCR) combines the simplicity and versatility of enzyme-linked immunosorbent assay (ELISA) with the exponential amplification capacity and sensitivity of PCR thus leading to several-fold increase in sensitivity in comparison to analogous ELISA. In this review, we have described the serodiagnostic potential of I-PCR assays for an early diagnosis of TB based on the detection of potential mycobacterial antigens and circulating antibodies in body fluids of TB patients.