Differential localization of dengue virus protease affects cell homeostasis and triggers to thrombocytopenia

Thrombocytopenia is one of the symptoms of many virus infections which is the "hallmark" in the case of dengue virus. In this study, we show the differential localization of existing two forms of dengue virus protease, i.e., NS2BNS3 to the nucleus and NS3 to the nucleus and mitochondria. We also report a nuclear transcription factor, erythroid differentiation regulatory factor 1 (EDRF1), as the substrate for this protease. EDRF1 regulates the expression and activity of GATA1, which in turn controls spectrin synthesis. Both GATA1 and spectrins are required for platelet formation. On the other hand, we found that the mitochondrial activities will be damaged by NS3 localization which cleaves GrpEL1, a co-chaperone of mitochondrial Hsp70. Levels of both EDRF1 and GrpEL1 were found to deteriorate in dengue virus-infected clinical samples. Hence, we conclude that NS2BNS3-mediated EDRF1 cleavage and the NS3-led mitochondrial dysfunction account for thrombocytopenia.

Response Surface Methodology Analysis of Energy Harvesting System over Pathway Tiles

This paper presents an experimental analysis of the optimization of PZT-based tiles for energy harvesting. The hardware (actual experiment), PZT-based tiles, were developed using 6 × 6 piezoelectric (PZT-lead zirconate titanate) sensors of 40 mm in diameter on a hard cardboard sheet (300 × 300 mm²). Our experimental analysis of the designed tiles obtained an optimized power of 3.626 mW (85 kg or 0.83 kN using 36 sensors) for one footstep and 0.9 mW for 30 footsteps at high tapping frequency. Theoretical analysis was conducted with software (Design-Expert) using the response surface methodology (RSM) for optimized PZT tiles, obtaining a power of 6784.155 mW at 150 kg or 1.47 kN weight using 34 sensors. This software helped to formulate the mathematical equation for the most suitable PZT tile model for power optimization. It used the quadratic model to provide adjusted and predicted R2 values of 0.9916 and 0.9650, respectively. The values were less than 0.2 apart, which indicates a high correlation between the actual and predicted values. The outcome of the various experiments can help with the selection of input factors for optimized power during pavement design.

Respiratory illness virus infections with special emphasis on COVID-19

Viruses that emerge pose challenges for treatment options as their uniqueness would not know completely. Hence, many viruses are causing high morbidity and mortality for a long time. Despite large diversity, viruses share common characteristics for infection. At least 12 different respiratory-borne viruses are reported belonging to various virus taxonomic families. Many of these viruses multiply and cause damage to the upper and lower respiratory tracts. The description of these viruses in comparison with each other concerning their epidemiology, molecular characteristics, disease manifestations, diagnosis and treatment is lacking. Such information helps diagnose, differentiate, and formulate the control measures faster. The leading cause of acute illness worldwide is acute respiratory infections (ARIs) and are responsible for nearly 4 million deaths every year, mostly in young children and infants. Lower respiratory tract infections are the fourth most common cause of death globally, after non-infectious chronic conditions. This review aims to present the characteristics of different viruses causing respiratory infections, highlighting the uniqueness of SARS-CoV-2. We expect this review to help understand the similarities and differences among the closely related viruses causing respiratory infections and formulate specific preventive or control measures.

Assessment of white matter damage in subacute sclerosing panencephalitis using quantitative diffusion tensor MR imaging

BACKGROUND AND PURPOSE

Subacute sclerosing panencephalitis (SSPE), a rare progressive degenerative disease, is caused by persistent infection with a defective measles virus. The correlation between the clinical staging and MR imaging is usually poor. The aim of the study was to investigate the role of diffusion tensor imaging (DTI) in the early detection of white matter damage in SSPE in the presence of normal findings on conventional imaging.

METHODS

DTI was performed in 21 patients in stage II SSPE and 10 age/sex-matched healthy controls. Fractional anisotropy (FA) and mean diffusivity (MD) values were calculated in the periventricular white matter, corpus callosum, and posterior limb of the internal capsule in patients with normal and abnormal findings on conventional imaging as well as healthy controls.

RESULTS

The patients were grouped into those with normal (n = 11) and abnormal (n = 10) findings on conventional imaging for the purpose of quantitative DTI analysis. Abnormal- and normal-appearing white matter on T2-weighted images showed significantly decreased FA values in all the regions compared with those in healthy controls. MD values were significantly increased in the periventricular white matter region of the frontal and parietooccipital lobe in patients with normal as well as abnormal findings on conventional imaging compared with those in healthy controls.

CONCLUSION

DTI detects early white matter abnormalities that may have significant therapeutic implication, even in the presence of normal findings on conventional imaging, in patients with SSPE.

Disruption of disulfide linkages of the Plasmodium falciparum circumsporozoite protein: effects on cytotoxic and antibody responses in mice

The circumsporozoite protein is a predominant surface antigen present on Plasmodium sporozoites. In Plasmodium falciparum circumsporozoite protein (PfCSP), two cysteine residues (396 and 401) are present adjacent to two overlapping cytotoxic T-lymphocyte epitopes of the protein and are involved in the formation of disulfide bridges. We investigated the role of these cysteines on the cellular and antibody responses towards the CS protein because disruption of disulfide linkages and the presence of cysteine residues in the flanking region of an epitope has been shown to significantly alter the immune responses to various proteins. Mice were immunized with variant forms of PfCSP DNA vaccine plasmids where these cysteine residues were individually mutated to alanine. The plasmid vaccines induced antigen specific antibody and cytotoxic T lymphocyte responses. While no alterations of cysteine influenced the CTL responses to P. falciparum CS protein, vaccine pVRCS4, containing an altered cysteine at position 401, dramatically improved the antibody response to the carboxyl-terminal region of the protein. This work indicates that sequence alterations of genes in an anti-malarial vaccine could enhance the response towards the native protein. Given the fact that long term natural immunity to the pathogen has not been documented, it may be important to challenge the immune system with non-native proteins.

A phylogenetic comparison of gene trees constructed from plastid, mitochondrial and genomic DNA of Plasmodium species

Gene trees of Plasmodium species have been reported for the nuclear encoded genes (e.g. the Small Subunit rRNA) and a mitochondrial encoded gene, cytochrome b. Here, we have analyzed a plastid gene coding for caseinolytic protease ClpC, whose structure, function and evolutionary history have been studied in various organisms. This protein possesses a 220-250 amino acid long AAA domain (ATPases associated with a variety of cellular activities) that belongs to the Walker super family of ATPases and GTPases. We have sequenced the AAA motif of this gene, encoding the protein from nine different species of Plasmodium infecting rodents, birds, monkeys, and humans. The codon usage and GC content of each gene were nearly identical in contrast to the widely varying nucleotide composition of genomic DNAs. Phylogenetic trees derived from both DNA and inferred protein sequences have consistent topologies. We have used the ClpC sequence to analyze the phylogenetic relationship among Plasmodium species and compared it with those derived from mitochondrial and genomic sequences. The results corroborate well with the trees constructed using the mitochondrially encoded cytochrome b. However, an important element distinguishes the trees: the placement of Plasmodium elongatum near the base of the plastid tree, indicating an ancient lineage of parasites in birds that branches from the tree prior to other lineages of avian malaria and the human parasite, P. falciparum.

Direct measurement of the interactions of glycosaminoglycans and a heparin decasaccharide with the malaria circumsporozoite protein

Circumsporozoite (CS) protein is a predominant surface antigen of malaria sporozoites, the infective form of the parasite, and has been used for making anti-malaria vaccines. For the first time we have examined the interaction of CS protein with various glycosaminoglycans in real time using surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). Heparin was the best binder among the glycosaminoglycans tested and bound to CS protein with nanomolar affinity. Using purified and structurally defined small heparin oligosaccharides, we identified a decasaccharide to be the minimum sized CS protein-binding sequence. In an indirect competition assay, this decasaccharide blocked the CS protein interaction with HepG2 cells with an ID(50) of less than 60 nM. The decasaccharide has a structure commonly found in hepatic heparan sulfate, and the same sequence has recently been shown to bind specifically to apolipoprotein E. Examination of porcine liver heparan sulfate in this indirect competition assay showed that it and heparin were the only glycosaminoglycans that could effectively block CS protein interaction with HepG2 cells in culture. These data support the hypothesis that the invasion of liver cells by the parasite shares a common mechanism with the hepatic uptake of lipoprotein remnants from the blood.

Long-term effects of topiramate on bipolar mood instability, weight change and glycemic control: a case-series

Topiramate is an antiepileptic agent, which is being investigated as a mood-stabilizer. Three obese individuals with DSM-IV bipolar I disorder and type II diabetes mellitus received topiramate treatment in combination with antipsychotics and valproate or carbamazepine. In addition to improved mood stability, these individuals lost between 16 to 20.5% of their pre-topiramate body weight and also achieved significant glycemic control.

Evidence for different mechanisms of chloroquine resistance in 2 Plasmodium species that cause human malaria

Chloroquine (CQ)-resistant Plasmodium vivax malaria was first reported 12 years ago, nearly 30 years after the recognition of CQ-resistant P. falciparum. Loss of CQ efficacy now poses a severe problem for the prevention and treatment of both diseases. Mutations in a digestive vacuole protein encoded by a 13-exon gene, pfcrt, were shown recently to have a central role in the CQ resistance (CQR) of P. falciparum. Whether mutations in pfcrt orthologues of other Plasmodium species are involved in CQR remains an open question. This report describes pfcrt homologues from P. vivax, P. knowlesi, P. berghei, and Dictyostelium discoideum. Synteny between the P. falciparum and P. vivax genes is demonstrated. However, a survey of patient isolates and monkey-adapted lines has shown no association between in vivo CQR and codon mutations in the P. vivax gene. This is evidence that the molecular events underlying P. vivax CQR differ from those in P. falciparum.

Geographic subdivision of the range of the malaria parasite Plasmodium vivax

We examined geographically distinct isolates of Plasmodium vivax and categorized them according to developmental success in Anopheles albimanus. We found that parasites from Central America and Colombia form a group distinct from those of Asia. New World isolates have a distinct chromosomal translocation and an episomal variation in the open reading frame (ORF) 470 DNA sequence that distinguishes them from the other isolates tested. Old World types of P. vivax were introduced into the Americas, and a remnant of this lineage remains in P. simium. It is indistinguishable from Old World P. vivax to the extent determinable by using our encoded markers and the examination of its developmental pattern in mosquitoes. The cohesive characteristics that separate types of P. vivax are predictors of range and potential for transmission and hence require taxonomic distinction.

Role of cysteines in Plasmodium falciparum circumsporozoite protein: interactions with heparin can rejuvenate inactive protein mutants

Various pathogenic bacteria, viruses, and protozoan bind to glycosaminoglycan-based receptors on host cells and initiate an infection. Sporozoites of Plasmodium predominantly express circumsporozoite (CS) protein on their surface, which binds to heparan sulfate proteoglycans on liver cell surface that subsequently leads to malaria. Here we show that the interaction of free heparin with this parasite ligand has the potential to be a critical component of invasion. CS protein of P. falciparum contains four cysteines at positions 361, 365, 396, and 401. In this study, all four cysteine residues were mutagenized to alanine both individually and in different combinations. Conversion of cysteine 396 to alanine (protein CS3) led to a 10-fold increase in the binding activity of the protein to HepG2 cells. Replacement of cysteines at positions 361, 365, and 401 either alone or in different combinations led to a near total loss of binding. Surprisingly, activity in these inactive mutants could be effectively restored in the presence of submolar concentrations of heparin. Heparin also up-regulated binding of CS3 at submolar concentrations with respect to the protein but down-regulated binding when present in excess. Given the significantly different concentrations of heparin in different organs of the host and the in vitro results described here one can consider in vivo ramifications of this phenomenon for pathogen targeting of specific organs and for the functional effects of antigenic variation on receptor ligand interaction.

The cytotoxic T-lymphocyte epitope of the Plasmodium falciparum circumsporozoite protein also modulates the efficiency of receptor-ligand interaction with hepatocytes

Malaria sporozoites are transmitted from the mosquito salivary gland to host hepatocytes within minutes of an infectious bite. The circumsporozoite protein (CS), which covers the surface of Plasmodium sporozoites, functions during these minutes in the targeting of host liver cells. The protein's potentially important role in an antimalaria vaccine has spawned interest in both the host immune responses to the parasite's presence and the actual functional role of the protein in the targeting of host liver cells. Here we show that the region of CS known to elicit a cytotoxic T-lymphocyte (CTL) response to irradiated sporozoites also, somewhat ironically, mediates the receptor-ligand interaction essential to parasite invasion of the host. Hence, the structure of CS represents a balance of potentially counterdirectional forces. Polymorphism in the CTL epitope appears to be a product of this balanced state as opposed to an "arms race" as it is so often portrayed. The conceptual difference between the theories regarding the maintainance of polymorphism in CTL epitopes may have significant implication for vaccine design.

Topiramate as add-on treatment for patients with bipolar mania

OBJECTIVE

Anticonvulsant agents such as carbamazepine and valproate are alternatives to lithium in treating subjects with bipolar disorder. Topiramate (Topamax), a new antiepileptic agent, is a candidate drug for bipolar disorder. We evaluated topiramate as adjunctive treatment for bipolar patients.

METHODS

Eighteen patients with DSM-IV bipolar I disorder [mania (n = 12), hypomania (n = 1), mixed episode (n = 5), and rapid cycling (n = 6)], and two subjects with schizoaffective disorder bipolar type, resistant to current mood-stabilizer treatment were initiated on topiramate, 25 mg/day, increasing by 25-50 mg every 3 7 days to a target dose between 100 and 300 mg/day, as other medications were held constant for 5 weeks. The Young Mania Rating Scale (Y-MRS), Hamilton Depression Rating Scale (Ham-D), and Clinical Global Impression-Bipolar Version Scale (CGI-BP) were used to rate subjects weekly.

RESULTS

By 5 weeks, 12 (60%) subjects were responders, i.e., 50% reduction in the Y-MRS scores and a CGI of 'much' or 'very much improved'. Three subjects were 'minimally improved', four showed no change, and one was 'minimally worse'. Six subjects had parasthesia, three experienced fatigue, and two had 'word-finding' difficulties; in all cases, side effects were transient. All patients lost weight with a mean of 9.4 lb in 5 weeks, and a significant reduction in body mass index (BMI) occurred too.

CONCLUSIONS

Topiramate appears to have efficacy for the manic and mixed phases of bipolar illness. Other preliminary data suggest antidepressant efficacy too. Among obese bipolar subjects, the weight loss potential of topiramate may be beneficial. If controlled trials confirm these initial results, topiramate may be a significant addition to the available treatments for bipolar disorder.

Role of individual cysteine residues and disulfide bonds in the structure and function of Aspergillus ribonucleolytic toxin restrictocin

Restrictocin, produced by the fungus Aspergillus restrictus, belongs to the group of ribonucleolytic toxins called ribotoxins. It specifically cleaves a single phosphodiester bond in a conserved stem and loop structure in the 28S rRNA of large ribosomal subunit and potently inhibits eukaryotic protein synthesis. Restrictocin contains 149 amino acid residues and includes four cysteines at positions 5, 75, 131, and 147. These cysteine residues are involved in the formation of two disulfide bonds, one between Cys 5 and Cys 147 and another between Cys 75 and Cys 131. In the current study, all four cysteine residues were changed to alanine individually and in different combinations by site-directed mutagenesis so as to remove one or both the disulfides. The mutants were expressed and purified from Escherichia coli. Removal of any cysteine or any one of the disulfide bonds individually did not affect the ability of the toxin to specifically cleave the 28S rRNA or to inhibit protein synthesis in vitro. However, the toxin without both disulfide bonds completely lost both ribonucleolytic and protein synthesis inhibition activities. The active mutants, containing only one disulfide bond, exhibited relatively high susceptibility to trypsin digestion. Thus, none of the four cysteine residues is directly involved in restrictocin catalysis; however, the presence of any one of the two disulfide bonds is absolutely essential and sufficient to maintain the enzymatically active conformation of restrictocin. For maintenance of the unique stability displayed by the native toxin, both disulfide bonds are required.

Construction, expression and characterization of chimaeric toxins containing the ribonucleolytic toxin restrictocin: intracellular mechanism of action

Restrictocin is a ribonucleolytic toxin produced by the fungus Aspergillus restrictus. Two chimaeric toxins containing restrictocin directed at the human transferrin receptor have been constructed. Anti-TFR(scFv)-restrictocin is encoded by a gene produced by fusing the DNA encoding a single-chain antigen-combining region (scFv) of a monoclonal antibody, directed at the human transferrin receptor, at the 5' end of that encoding restrictocin. The other chimaeric toxin, restrictocin-anti-TFR(scFv), is encoded by a gene fusion containing the DNA encoding the single-chain antigen-combining region of antibody to human transferrin receptor at the 3' end of the DNA encoding restrictocin. These gene fusions were expressed in Escherichia coli, and fusion proteins purified from the inclusion bodies by simple chromatography techniques to near-homogeneity. The two chimaeric toxins were found to be equally active in inhibiting protein synthesis in a cell-free in vitro translation assay system. The chimaeric toxins were selectively toxic to the target cells in culture with potent cytotoxic activities. However, restrictocin-anti-TFR(scFv) was more active than anti-TFR(scFv)-restrictocin on all cell lines studied. By using protease and metabolic inhibitors, it can be shown that, to manifest their cytotoxic activity, the restrictocin-containing chimaeric toxins need to be proteolytically processed intracellularly and the free toxin or a fragment thereof thus generated is translocated to the target via a route involving the Golgi apparatus.

Cytotoxic activity of ribonucleolytic toxin restrictocin-based chimeric toxins targeted to epidermal growth factor receptor

Targeted toxins represent a new approach to specific cytocidal therapy. The ribonucleolytic protein toxin restrictocin is a potent protein synthesis inhibitor produced by the fungus Aspergillus restrictus. In the present study we have constructed two restrictocin based chimeric toxins where human transforming growth factor alpha (TGF alpha) has been used as a ligand. TGF alpha is a single chain polypeptide, which binds to epidermal growth factor receptor (EGFR) and causes proliferation in a large number of cancers. The ligand has been separately fused either at the amino terminus or carboxyl terminus of restrictocin, giving rise to TGF alpha-restrictocin and restrictocin-TGF alpha respectively. The fusion proteins were overexpressed in Escherichia coli and purified from inclusion bodies by a denaturation-renaturation protocol. Both the chimeric toxins actively inhibited eukaryotic protein synthesis in a cell free in vitro translation assay system. These chimeric toxins selectively killed human epidermal growth factor receptor positive target cells in culture. Among the two proteins, restrictocin-TGF alpha was more active than TGF alpha-restrictocin on all the cell lines studied.

Overproduction of fungal ribotoxin alpha-sarcin in Escherichia coli: generation of an active immunotoxin

alpha-Sarcin is a ribonucleolytic protein secreted by the mold Aspergillus giganteus. DNA encoding alpha-sarcin was isolated from the host and cloned into T7 promoter based E. coli expression vectors. Using bacterial outer membrane protein A (OmpA) signal sequence, properly processed recombinant (re-) protein was secreted into the culture medium while in the absence of a signal sequence protein remained insoluble in the bacterial inclusion bodies. The re-alpha-sarcin was purified to homogeneity by simple chromatographic techniques both from the insoluble and soluble sources with respective yields of 40-50 microg/ml and 2-3 microg/ml. The re-ribotoxin was functionally as active as the native toxin and preserved its specificity. The re-alpha-sarcin was used in the construction of an active immunotoxin targeted at the human cancer cells overexpressing transferrin receptor (TFR).

Expression of ribonucleolytic toxin restrictocin in Escherichia coli: purification and characterization

Restrictocin is a toxin produced by the fungus Aspergillus restritus. The DNA coding for restrictocin was isolated from the host by polymerase chain reaction and cloned into a T7 promoter-based expression vector. The protein was overproduced in Escherichia coli and remained insoluble in the cell in the form of inclusion bodies. Recombinant restrictocin was purified in large amounts, by a simple denaturation-renaturation protocol involving a redox system, with typical yields of 45 mg/l of original culture. Restrictocin could be secreted into the bacterial medium using ompA, pelB and LTB signal sequences. Among the three signal sequences, ompA was found to be the most efficient in secreting the recombinant protein. The protein secreted into the extracellular medium was properly processed as evident by the amino-terminal sequencing. Recombinant restrictocin was readily purified to homogeneity from either the medium or inclusion bodies by simple chromatographic techniques and was found to be functionally as active as the native fungal protein in inhibiting the eukaryotic translation.

Generation of active immunotoxins containing recombinant restrictocin

Restrictocin, a toxin produced by the fungus Aspergillus restrictus, is a potent inhibitor of eukaryotic protein synthesis. Recombinant restrictocin was made in Escherichia coli and purified to homogeneity in large amounts. The recombinant protein was found to be poorly immunogenic in mice with low toxicity, when injected intraperitoneally. Two immunotoxins were constructed by coupling the recombinant restrictocin to an antibody to the human transferrin receptor, using a cleavable and a stable linkage. The immunotoxins so generated showed specific cytotoxic activity toward receptor bearing cells in tissue culture. Immunotoxin with a cleavable linkage, however, was more active than that containing a stable linkage. Restrictocin appears to be a promising candidate to be developed as a chimeric toxin for targeted therapy.