Natural infection of Delta mutant of SARS-CoV-2 in Asiatic lions of India

The current pandemic caused by a novel coronavirus (SARS‐CoV‐2) has underlined the importance of emerging diseases of zoonotic importance. Along with human beings, several species of wild and pet animals have been demonstrated to be infected by SARS‐CoV‐2, both naturally and experimentally. In addition, with constant emergence of new variants, the species susceptibility might further change which warrants intensified screening efforts. India is a vast and second most populated country, with a habitat of a very diverse range of animal species. In this study we place on record of SARS‐CoV‐2 infections in three captive Asiatic lions. Detailed genomic characterization revealed involvement of Delta mutant (Pango lineage B.1.617.2) of SARS‐CoV‐2 at two different locations. Interestingly, no other feline species enclosed in the zoo/park were found infected. The epidemiological and molecular analysis will contribute to the understanding of the emerging mutants of SARS‐CoV‐2 in wild and domestic animals.

Identification of mycobacterium spp. and nocardia spp. from solid and liquid cultures by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)

Identification of microorganisms by MALDI-TOF MS has been widely accepted in clinical microbiology. However, for Mycobacterium spp. and Nocardia spp. such identification has not yet reached the optimal level of routine testing. Here we describe the development of an identification tool for 49 and 15 species of Mycobacterium spp. and Nocardia spp., respectively. During database construction, a number of ambiguous reference identifications were revealed and corrected via molecular analyses. Eventually, more than 2000 individual mass spectra acquired from 494 strains were included in a reference database and subjected to bio-statistical analyses. This led to correct species identification and correct combination of species into several complexes or groups, such as the Mycobacterium tuberculosis complex. With the Advanced Spectrum Classifier algorithm, class-specific bin weights were determined and tested by cross-validation experiments with good results. When challenged with independent isolates, overall identification performance was 90% for identification of Mycobacterium spp. and 88% for Nocardia spp. However, for a number of Mycobacterium sp. isolates, no identification could be achieved and in most cases, this could be attributed to the production of polymers that masked the species-specific protein peak patterns. For the species where >20 isolates were tested, correct identification reached 95% or higher. With the current spectral database, the identification of Mycobacterium spp. and Nocardia spp. by MALDI-TOF MS can be performed in routine clinical diagnostics although in some complicated cases verification by sequencing remains mandatory.

Rates of processing determine the immunogenicity of immunoproteasome-generated epitopes

CD8 T cells resolve intracellular pathogens by responding to pathogen-derived peptides that are presented on the cell surface by MHC class I molecules. Although most pathogens encode a large variety of antigenic peptides, protective CD8 T cell responses target usually only a few of these. To determine the mechanism by which the IFN-gamma-inducible proteasome (immuno) subunits enhance the ability of specific pathogen-derived peptides to elicit CD8 T cell responses, we generated a recombinant Listeria monocytogenes strain (rLM-E1) that secretes a model Ag encompassing the immunoproteasome-dependent E1B(192-200) and immunoproteasome-independent E1A(234-243) epitope. Analyses of Ag presentation showed that infected gene-deficient professional APCs, lacking the immunosubunits LMP7/ibeta5 and MECL-1/ibeta2, processed and presented the rLM-E1-derived E1B(192-200) epitope but with delayed kinetics. E1A epitope processing proceeded normally in these cells. Accordingly, infected gene-deficient mice failed to respond to the otherwise immunodominant E1B(192-200) epitope but mounted normal CD8 T cell responses to E1A(234-243) which was processed by the same professional APCs, from the same rLM-E1 Ag. The inability of gene-deficient mice to respond to E1B(192-200) was not explained by insufficient quantities of antigenic peptide, as splenic APC of 36-h-infected gene-deficient mice that presented the two E1 epitopes at steady state levels elicited responses to both E1B(192-200) and E1A(234-243) when transferred into LMP7+MECL-1-deficient mice. Taken together, our findings indicate that not absolute epitope quantities but early Ag-processing kinetics determine the ability of pathogen-derived peptides to elicit CD8 T cell responses, which is of importance for rational T cell vaccine design.

Role of Mycobacterium tuberculosis Ser/Thr kinase PknF: implications in glucose transport and cell division

Protein kinases have a diverse array of functions in bacterial physiology, with a distinct role in the regulation of development, stress responses, and pathogenicity. pknF, one of the 11 kinases of Mycobacterium tuberculosis, encodes an autophosphorylating, transmembrane serine/threonine protein kinase, which is absent in the fast-growing, nonpathogenic Mycobacterium smegmatis. Herein, we investigate the physiological role of PknF using an antisense strategy with M. tuberculosis and expressing PknF and its kinase mutant (K41M) in M. smegmatis. Expression of PknF in M. smegmatis led to reduction in the growth rate and shortening and swelling of cells with constrictions. Interestingly, an antisense strain of M. tuberculosis expressing a low level of PknF displayed fast growth and a deformed cell morphology compared to the wild-type strain. Electron microscopy showed that most of the cells of the antisense strain were of a smaller size with an aberrant septum. Furthermore, nutrient transport analysis of these strains was conducted using 3H-labeled and 14C-labeled substrates. A significant increase in the uptake of D-glucose but not of glycerol, leucine, or oleic acid was observed in the antisense strain compared to the wild-type strain. The results suggest that PknF plays a direct/indirect role in the regulation of glucose transport, cell growth, and septum formation in M. tuberculosis.

Phosphoprotein phosphatase of Mycobacterium tuberculosis dephosphorylates serine-threonine kinases PknA and PknB

The regulation of cellular processes by the modulation of protein phosphorylation/dephosphorylation is fundamental to a large number of processes in living organisms. These processes are carried out by specific protein kinases and phosphatases. In this study, a previously uncharacterized gene (Rv0018c) of Mycobacterium tuberculosis, designated as mycobacterial Ser/Thr phosphatase (mstp), was cloned, expressed in Escherichia coli, and purified as a histidine-tagged protein. Purified protein (Mstp) dephosphorylated the phosphorylated Ser/Thr residues of myelin basic protein (MBP), histone, and casein but failed to dephosphorylate phospho-tyrosine residue of these substrates, suggesting that this phosphatase is specific for Ser/Thr residues. It has been suggested that mstp is a part of a gene cluster that also includes two Ser/Thr kinases pknA and pknB. We show that Mstp is a trans-membrane protein that dephosphorylates phosphorylated PknA and PknB. Southern blot analysis revealed that mstp is absent in the fast growing saprophytes Mycobacterium smegmatis and Mycobacterium fortuitum. PknA has been shown, whereas PknB has been proposed to play a role in cell division. The presence of mstp in slow growing mycobacterial species, its trans-membrane localization, and ability to dephosphorylate phosphorylated PknA and PknB implicates that Mstp may play a role in regulating cell division in M. tuberculosis.

Isolated central canal rupture of spinal dermoid: report of two cases

We report two cases of lumbar spinal dermoid cysts with asymptomatic rupture and migration of free fat droplets into the central canal. No fatty droplets were seen within the lumbar subarachnoid space. The presence of fat droplets within the central canal is unusual because the central canal is rudimentary in adults. We suggest that hydromyelia secondary to tumour and specific tumour morphology might facilitate the selective rupture of dermoids into the central canal. We recommend a follow up of these patients to detect any possible intracranial migration of fat droplets and resultant complications.

Spinal angiolipoma: report of three cases and review of MRI features

We report three cases of spinal angiolipoma, two intramedullary and one epidural, and review their MRI features. Diagnoses were established preoperatively in all cases. Specific MRI features including the importance of postgadolinium fat-saturated T1-weighted images and presence of vascular flow-voids are discussed with histopathological correlation. A characteristic morphological appearance of intramedullary angiolipoma has been suggested.

Spinal angiolipoma: report of three cases and review of MRI features

We report three cases of spinal angiolipoma, two intramedullary and one epidural, and review their MRI features. Diagnoses were established preoperatively in all cases. Specific MRI features including the importance of postgadolinium fat-saturated T1-weighted images and presence of vascular flow-voids are discussed with histopathological correlation. A characteristic morphological appearance of intramedullary angiolipoma has been suggested.

Epithelioid sarcoma of the sciatic nerve perineural sheath: a mimic of nerve sheath tumor

We report herein a rare case of epithelioid sarcoma, in a 39-year old lady involving the sciatic nerve. Clinically and radiologically it stimulated a nerve sheath tumor. Involvement of a nerve by an epithelioid sarcoma is extremely uncommon. To the best of our knowledge, this is the first case of an epithelioid sarcoma involving the sciatic nerve and needs documentation.

Therapeutic efficacies of isoniazid and rifampin encapsulated in lung-specific stealth liposomes against Mycobacterium tuberculosis infection induced in mice

One recent promising development in the modification of drug formulations to improve chemotherapy is the use of a liposome-mediated drug delivery system. The efficacies of isoniazid and rifampin encapsulated in lung-specific stealth liposomes were evaluated by injecting liposomal drugs and free drugs into tuberculous mice twice a week for 6 weeks. Liposome-encapsulated drugs at and below therapeutic concentrations were more effective than free drugs against tuberculosis, as evaluated on the basis of CFUs detected, organomegaly, and histopathology. Furthermore, liposomal drugs had marginal hepatotoxicities as determined from the levels of total bilirubin and hepatic enzymes in serum. The elimination of mycobacteria from the liver and spleen was also higher with liposomal drugs than with free drugs. The encapsulation of antitubercular drugs in lung-specific stealth liposomes seems to be a promising therapeutic approach for the chemotherapy of tuberculosis.

Lung specific stealth liposomes: stability, biodistribution and toxicity of liposomal antitubercular drugs in mice

Liposomes with enhanced affinity towards lung tissue were prepared for the development of more effective chemotherapy against tuberculosis. Modification of surface of stealth liposomes by tagging O-stearylamylopectin (O-SAP) resulted in the increased affinity of these liposomes towards lung tissue of mice. Liposomes containing egg phosphatidylcholine (ePC), cholesterol (CH), dicetylphosphate (DCP), O-SAP and monosialogangliosides (GM1)/distearylphosphatidylethanolamine-poly(ethylene glycol) 2000 (DSPE-PEG 2000) were found to be most stable in serum. Tissue distribution of these liposomes showed more accumulation in lungs than in reticuloendothelial systems (RES) of normal and tuberculous mice. Pre administration of PC and CH (2:1.5) liposomes before the injection of lung specific stealth liposomes further enhanced their uptake in lungs. In vivo stability of these liposomes demonstrated the slow and controlled release of their encapsulated contents. Isoniazid and rifampicin encapsulated in liposomes were less toxic to peritoneal macrophages as compared to free drugs. Further, encapsulated drugs also demonstrated reduced in vivo toxicity in comparison to free drug(s). These findings suggest liposomes to be better drug delivery vehicles for experimental tuberculosis.