Cerebrospinal fluid lysozyme level for the diagnosis of tuberculous meningitis in children

FRET-Based Aptasensor for the Selective and Sensitive Detection of Lysozyme

Lysozyme is a conserved antimicrobial enzyme and has been cited for its role in immune modulation. Increase in lysozyme concentration in body fluids is also regarded as an early warning of some diseases such as Alzheimer’s, sarcoidosis, Crohn’s disease, and breast cancer. Therefore, a method for a sensitive and selective detection of lysozyme can benefit many different areas of research. In this regard, several aptamers that are specific to lysozyme have been developed, but there is still a lack of a detection method that is sensitive, specific, and quantitative. In this work, we demonstrated a single-molecule fluorescence resonance energy transfer (smFRET)-based detection of lysozyme using an aptamer sensor (also called aptasensor) in which the binding of lysozyme triggers its conformational switch from a low-FRET to high-FRET state. Using this strategy, we demonstrated that the aptasensor is sensitive down to 2.3 picomoles (30 nM) of lysozyme with a dynamic range extending to ~2 µM and has little to no interference from similar biomolecules. The smFRET approach used here requires a dramatically small amount of aptasensor (~3000-fold less as compared to typical bulk fluorescence methods), and it is cost effective compared to enzymatic and antibody-based approaches. Additionally, the aptasensor can be readily regenerated in situ via a process called toehold mediated strand displacement (TMSD). The FRET-based aptasensing of lysozyme that we developed here could be implemented to detect other protein biomarkers by incorporating protein-specific aptamers without the need for changing fluorophore-labeled DNA strands.

Emerging mass spectrometry-based approaches to probe protein-receptor interactions: focus on overcoming physiological barriers

Physiological barriers, such as the blood-brain barrier and intestinal epithelial barrier, remain significant obstacles towards wider utilization of biopharmaceutical products. Receptor-mediated transcytosis has long been viewed as an attractive means of crossing such barriers, but successful exploitation of this route requires better understanding of the interactions between the receptors and protein-based therapeutics. Detailed characterization of such processes at the molecular level is challenging due to the very large physical size and heterogeneity of these species, which makes use of many state-of-the art analytical techniques, such as high-resolution NMR and X-ray crystallography impractical. Mass spectrometry has emerged in the past decade as a powerful tool to study protein-receptor interactions, although its applications to investigate interaction of biopharmaceuticals with their physiological partners are still limited. We highlight the potential of this technique by considering several recent examples where it had been instrumental for understanding molecular mechanisms critical for receptor-mediated transcytosis of transferrin-based therapeutics.

Mass spectrometry-guided optimization and characterization of a biologically active transferrin-lysozyme model drug conjugate

Transferrin is a promising drug carrier that has the potential to deliver metals, small organic molecules and therapeutic proteins to cancer cells and/or across physiological barriers (such as the blood-brain barrier). Despite this promise, very few transferrin-based therapeutics have been developed and reached clinical trials. This modest success record can be explained by the complexity and heterogeneity of protein conjugation products, which also pose great challenges to their analytical characterization. In this work, we use lysozyme conjugated to transferrin as a model therapeutic that targets the central nervous system (where its bacteriostatic properties may be exploited to control infection) and develop analytical protocols based on electrospray ionization mass spectrometry to characterize its structure and interactions with therapeutic targets and physiological partners critical for its successful delivery. Mass spectrometry has already become an indispensable tool facilitating all stages of the protein drug development process, and this work demonstrates the enormous potential of this technique in facilitating the development of a range of therapeutically effective protein-drug conjugates.

Endothelialization of chitosan porous conduits via immobilization of a recombinant fibronectin fragment (rhFNIII7-10)

The present study aimed to develop a pre-endothelialized chitosan (CH) porous hollowed scaffold for application in spinal cord regenerative therapies. CH conduits with different degrees of acetylation (DA; 4% and 15%) were prepared, characterized (microstructure, porosity and water uptake) and functionalized with a recombinant fragment of human fibronectin (rhFNIII(7-10)). Immobilized rhFNIII(7-10) was characterized in terms of amount ((125)I-radiolabelling), exposure of cell-binding domains (immunofluorescence) and ability to mediate endothelial cell (EC) adhesion and cytoskeletal rearrangement. Functionalized conduits revealed a linear increase in immobilized rhFNIII(7-10) with rhFNIII(7-10) concentration, and, for the same concentration, higher amounts of rhFNIII(7-10) on DA 4% compared with DA 15%. Moreover, rhFNIII(7-10) concentrations as low as 5 and 20μg ml(-1) in the coupling reaction were shown to provide DA 4% and 15% scaffolds, respectively, with levels of exposed cell-binding domains exceeding those observed on the control (DA 4% scaffolds incubated in a 20μg ml(-1) human fibronectin solution). These grafting conditions proved to be effective in mediating EC adhesion/cytoskeletal organization on CH with DA 4% and 15%, without affecting the endothelial angiogenic potential. rhFNIII(7-10) grafting to CH could be a strategy of particular interest in tissue engineering applications requiring the use of endothelialized porous matrices with tunable degradation rates.

Clinical practice: diagnosis of childhood tuberculosis

Childhood tuberculosis (TB) represents an important part of the disease burden, yet its diagnosis remains challenging. This review summarizes the clinical, radiological, and bacteriological approaches to diagnose TB infection and disease in children. Fever (possibly intermittent or low grade), weight loss or failure to thrive, and a persistent cough for >2 weeks are the most important clinical signs for pulmonary tuberculosis. Extra-pulmonary TB, which might occur in over 40% of the patients, can have in addition some specific clinical symptoms or signs. Chest radiographs provide important information in many patients and advanced imaging can be applied in case of (and should be restricted to) inconclusive diagnosis. The Mantoux test is positive in up to 70% of non-immunocompromised TB patients, whereas HIV co-infection or malnourishment results in a lower reactivity. Evidence of an adult TB index case is clue for diagnosis of childhood TB in low-endemic countries. Bacteriological confirmation remains difficult and is useful for doubtful cases or when drug resistance is suspected.

Biopsy-proven tuberculous meningitis mimicking CNS sarcoidosis

We report a 31-year-old man with tuberculous meningitis (TM) mimicking CNS sarcoidosis. Although Mycobacterium tuberculosis (MTB) was not detected in CSF, the level of adenosine deaminase (ADA) in CSF was significantly raised. Brain biopsy showed caseous granuloma and a diagnosis of TM was made. The diagnosis of TM is often difficult and brain biopsy should be considered if MTB is not detected in the CSF. Evaluation of CSF ADA level could also strongly contribute to distinguishing TM from other meningitis. In addition to antituberculosis drugs, corticosteroid therapy was effective in our patient but careful reduction of its dosage was required.