Diagnosis of abdominal tuberculosis: Detection of mycobacterial CFP-10 and HspX proteins by gold nanoparticle-PCR amplified immunoassay

Attempts were made to improve the efficacy of PCR amplified immunoassay (I-PCR) for diagnosing abdominal TB cases by utilizing the gold nanoparticle (AuNP)-based I-PCR, where AuNPs were functionalized with detection antibodies/oligonucleotides that exhibited 84.3% sensitivity and 95.1% specificity. This assay would improve the ongoing algorithms used in abdominal TB diagnosis.

Multiple integrations of a sense transgene, including a tandem inverted repeat confer stable RNA-silencing mediated virus resistance under different abiotic and biotic conditions

In a previous study, tobacco plants, transformed with a sense construct of the 57K domain of the replicase gene of tobacco rattle virus (TRV), provided resistance against genetically distant isolates of the virus. In this work, 57K-specific siRNAs were detected with RT-qPCR solely in the resistant line verifying the RNA-silencing base of the resistance. The integration sites of the transgene into the plant genome were identified with inverse-PCR. Moreover, the resistance against TRV was practically unaffected by low temperature conditions and the presence of heterologous viruses. The mechanism of the resistance was further examined by a gene expression analysis that showed increased transcript levels of genes with a key-role in the RNA silencing pathway and the basal antiviral defence. This work provides a comprehensive characterization of the robust virus resistance obtained by a sense transgene and underlines the usefulness of transgenic plants obtained by such a strategy.

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.

Recent updates in diagnosis of abdominal tuberculosis with emphasis on nucleic acid amplification tests

INTRODUCTION

Abdominal tuberculosis (TB) is a common epitome of extrapulmonary TB (EPTB), wherein peritoneal and intestinal TB are the most prevalent forms. Diagnosis of abdominal TB is a daunting challenge owing to variable anatomical locations, paucibacillary nature of specimens and atypical clinical presentations that mimic other abdominal diseases, such as Crohn's disease and malignancies. In this review, we made a comprehensive study on the diagnosis of abdominal TB.

AREA COVERED

Various modalities employed for abdominal TB diagnosis include clinical features, imaging, bacteriological tests (smear/culture), histopathological/cytological observations, interferon-gamma release assays and nucleic acid amplification tests (NAATs). Among NAATs, loop-mediated isothermal amplification assay, PCR, multiplex-PCR, nested PCR, real-time PCR and GeneXpert® MTB/RIF were discussed. Identification of circulating Mycobacterium tuberculosis cell-free DNA by real-time PCR within ascitic fluids is another useful approach.

EXPERT OPINION

Several novel molecular/immunological methods, such as GeneXpert Ultra, aptamer-linked immobilized sorbent assay, immuno-PCR (I-PCR) and nanoparticle-based I-PCR have recently been developed for detecting pulmonary TB and several EPTB types, which may also be explored for abdominal TB diagnosis. Precise and prompt diagnosis of abdominal TB may initiate an early therapy so as to reduce the complications, i.e. abdominal pain, ascites, abdominal distension, intestinal obstruction/perforation, etc., and avoid surgical involvement.Plain Language SummaryAbdominal tuberculosis (TB) is a manifestation of extrapulmonary TB (EPTB), where peritoneal and intestinal TB are two major forms. Diagnosis of abdominal TB is difficult owing to low bacterial load present in clinical samples and non-specific clinical presentations as it mimics other diseases such as inflammatory bowel diseases, abdominal malignancies, etc. Bacteriological tests (smear/culture) almost fail owing to poor sensitivities and it is not always possible to get representative tissue samples for histopathological and cytological observations. In recent years, molecular tests i.e. nucleic acid amplification tests (NAATs), such as PCR/multiplex-PCR (M-PCR), nested PCR and GeneXpert are widely employed. Markedly, PCR/M-PCR and nested PCR exhibited reasonable good sensitivities/specificities, while GeneXpert revealed low sensitivity in most of the studies but high specificity, thus it could assist in differential diagnosis of intestinal TB and Crohn's disease. Further, novel molecular/immunological tests employed for pulmonary TB and other EPTB types were described and those tests can also be utilized to diagnose abdominal TB. Reliable and rapid diagnosis of abdominal TB would initiate an early start of anti-tubercular therapy and reduce the severe complications.

T-DNA Insertional Mutagenesis and Activation Tagging in Medicago truncatula

The development of plant genetic transformation techniques has greatly enhanced our capacity to investigate and understand gene function. Since T-DNA constructs insert randomly in genomes, in principle, it is possible to construct a population of individuals harboring one or more T-DNA inserted in any region of the genome. Such populations can be screened following two approaches: (1) given a mutant phenotype, one could find the gene subtending the phenotypic alteration (forward approach), or (2) given a gene of interest, one could identify the phenotypic effect of its expression perturbation (reverse approach).Activation tagging is an application of T-DNA mutagenesis aimed at obtaining gain-of-function mutations. This can be achieved by introducing enhancer sequences randomly in the target genome via a T-DNA shuttle and then analyzing the genomic regions flanking the insertion sites in individuals showing phenotypic alterations. In this chapter, we describe the detailed procedure to obtain and screen an activation-tagged population in Medicago truncatula.

A novel method for detection of H9N2 influenza viruses by an aptamer-real time-PCR

H9N2 Influenza subtype has emerged in Tunisia causing epidemics in poultry and resulting in major economic losses. New mutations in their hemagglutinin and neuraminidase proteins were acquired, suggesting their potential to directly infect humans. Effective surveillance tools should be implemented to help prevent potential spillover of the virus across species. We have developed a highly sensitive real time immuno-polymerase chain reaction (RT-I-PCR) method for detecting H9N2 virus. The assay applies aptamers as ligands to capture and detect the virus. First, a panel of specific ssDNA aptamers was selected via a one step high stringency protocol. Next, the panel of selected aptamers was characterized for their affinities and their specificity to H9N2 virus. The aptamer showing the highest binding affinity to the virus was used as ligand to develop a highly sensitive sandwich Aptamer I-PCR. A 3-log increase in analytical sensitivity was achieved as compared to a routinely used ELISA antigen test, highlighting the potential of this approach to detect very low levels of virus particles. The test was validated using clinical samples and constitutes a rapid and a label-free platform, opening a new venue for the development of aptamer -based viability sensing for a variety of microorganisms of economic importance in Tunisia and surrounding regions.