Drosophila melanogaster as a function-based high-throughput screening model for antinephrolithiasis agents in kidney stone patients

Kidney stone disease involves the aggregation of stone-forming salts consequent to solute supersaturation in urine. The development of novel therapeutic agents for this predominantly metabolic and biochemical disorder have been hampered by the lack of a practical pre-clinical model amenable to drug screening. Here, Drosophila melanogaster, an emerging model for kidney stone disease research, was adapted as a high-throughput functional drug screening platform independent of the multifactorial nature of mammalian nephrolithiasis. Through functional screening, the therapeutic potential of a novel compound commonly known as arbutin that specifically binds to oxalate, a key component of kidney calculi, was identified. Through isothermal titration calorimetry, high-performance liquid chromatography and atomic force microscopy, arbutin was determined to interact with calcium and oxalate in both free and bound states, disrupting crystal lattice structure, growth and crystallization. When used to treat patient urine samples, arbutin significantly abrogated calculus formation in vivo and outperformed potassium citrate in low pH urine conditions, owing to its oxalate-centric mode of action. The discovery of this novel antilithogenic compound via D. melanogaster, independent of a mammalian model, brings greater recognition to this platform, for which metabolic features are primary outcomes, underscoring the power of D. melanogaster as a high-throughput drug screening platform in similar disorders. This is the first description of the use of D. melanogaster as the model system for a high-throughput chemical library screen. This article has an associated First Person interview with the first authors of the paper.

The economic cost of stroke-associated pneumonia in a UK setting

Introduction Stroke-associated pneumonia (SAP) is common, however, data on the economic impact of SAP are scarce. This study aimed to prospectively evaluate the impact of SAP on acute stroke care costs in a UK setting. Methods Prospective cohort study of 213 consecutive patients with stroke (196 ischemic, 17 hemorrhagic) was admitted to a UK hospital over 1 year. Socio demographic and clinical characteristics were recorded along with all treatments and rehabilitation activity. Patients were classified as having SAP if they fulfilled criteria for "probable" or "definite" respiratory tract infection according to the Centres for Disease Control and Prevention definition, within the first seven days following stroke. Resource use was calculated using a "bottom up" approach of cumulative unit costs. Univariate and multivariate regression analyses were used to establish independent predictors of direct costs. Results Probable or definite SAP occurred in 13.2% (28/213) of patients. Patients with SAP experienced greater inpatient stays (31 days vs. 9 days, p ≤ 0.001) and higher in-hospital mortality (29.2% vs. 10.2%, p = 0.007). Mean (SD) acute care costs per patient was £7035 (6767), but costs were significantly greater for patients with SAP than without [£14,371 (9484) versus £6,103 (5,735); p ≤ 0.001]. SAP was an independent predictor of costs along with increasing stroke severity (NIHSS) and age. Occurrence of SAP resulted in an adjusted incremental additional cost of £5817 (95% CI 4945-6689; p = 0.001) per patient. Conclusions SAP increased acute care costs for stroke by approximately 80%. This provides further impetus for research aimed at reducing SAP, and will inform cost-effectiveness analyses of potential therapeutic strategies.

The multiple inhibitory mechanisms of GEM 91, a gag antisense phosphorothioate oligonucleotide, for human immunodeficiency virus type 1

GEM 91 (gene expression modulator) is a 25-mer oligonucleotide phosphorothioate complementary to the gag initiation site of HIV-1. GEM 91 has been studied in various in vitro cell culture models to examine inhibitory effects on different stages of HIV-1 replication. Experiments were focused on the binding of virions to the cell surface, inhibition of virus entry, reverse transcription (HIV DNA production), inhibition of steady state viral mRNA levels, inhibition of virus production from chronically infected cells, and inhibition of HIV genome packaging within virions. Experiments were also performed in vitro in an attempt to generate strains of HIV with reduced sensitivity to GEM 91. We observed sequence-dependent inhibition of virus entry/reverse transcription and a reduction in steady state viral RNA levels. We also observed sequence-independent inhibition of virion binding to cells and inhibition of virus production by chronically infected cells. Using in vitro methods that were successful in generating HIV strains with reduced sensitivity to AZT, we were unable to generate strains with reduced sensitivity to GEM 91.

5' Coding and regulatory region sequence divergence with conserved function of the Epstein-Barr virus LMP2A homolog in herpesvirus papio

B-lymphotropic herpesviruses naturally infecting Old World primates share biologic, epidemiologic, pathogenic, and molecular features with the human pathogen Epstein-Barr virus (EBV). These related gammaherpesviruses have colinear genomes with considerable nucleotide homology. The replicative cycle genes share a high degree of homology across species, whereas the transformation-associated EBV latent genes appear to be much more divergent. For example, the EBV BamHI Nhet fragment, which encodes all or part of the EBV latent infection membrane proteins, cross-hybridizes poorly to DNA from nonhuman primate B-lymphotropic herpesviruses. A viral DNA fragment corresponding to this region of the EBV genome was isolated from the baboon B-lymphotropic herpesvirus, herpesvirus papio, and used to clone a herpesvirus papio cDNA corresponding to EBV LMP2A. At least three tyrosine kinase interaction motifs are conserved despite significant amino acid divergence of the herpesvirus papio LMP2A first exon from the EBV homolog. Functionally, the herpesvirus papio LMP2A is tyrosine phosphorylated and induces tyrosine phosphorylation of cell proteins similar to EBV LMP2A. The 12 hydrophobic LMP2 transmembrane domains are well conserved. Two CBP (Jk) binding sites important for EBNA-2-induced transactivation of the LMP2A promoter are also present in the herpesvirus papio LMP2A promoter, and the simian LMP2A promoter is also responsive to EBV EBNA-2-induced transactivation in human B cells. Thus, transcriptional regulation, splicing, kinase interaction sites, and tyrosine phosphorylation of the LMP2A homologs have been conserved despite significant sequences heterogeneity in the preterminal repeat regions of these human and nonhuman primate EBVs. The conservation of the LMP2 gene, despite its apparent nonessential role for in vitro EBV infection, suggests an important role for LMP2A in vivo. The similarities between these human and simian B-lymphotropic herpesviruses, and the LMP2 genes in particular, suggest that the function of LMP2 in vivo could be addressed by using recombinant LMP2A-mutant simian viruses and experimental infection of Old World primates.

A rabbitpox virus serpin gene controls host range by inhibiting apoptosis in restrictive cells

Poxviruses are unique among viruses in encoding members of the serine proteinase inhibitor (serpin) superfamily. Orthopoxviruses contain three serpins, designated SPI-1, SPI-2, and SPI-3. SPI-1 encodes a 40-kDa protein that is required for the replication of rabbitpox virus (RPV) in PK-15 or A549 cells in culture (A. N. Ali, P. C. Turner, M. A. Brooks, and R. W. Moyer, Virology 202:305-314, 1994). Examination of nonpermissive human A549 cells infected with an RPV mutant disrupted in the SPI-1 gene (RPV delta SPI-1) suggests there are no gross defects in protein or DNA synthesis. The proteolytic processing of late viral structural proteins, a feature of orthopoxvirus infections associated with the maturation of virus particles, also appears relatively normal. However, very few mature virus particles of any kind are produced compared with the level found in infections with wild-type RPV. Morphological examination of RPV delta SPI-1-infected A549 cells, together with an observed fragmentation of cellular DNA, suggests that the host range defect is associated with the onset of apoptosis. Apoptosis is seen only in RPV delta SPI-1 infection of nonpermissive (A549 or PK-15) cells and is absent in all wild-type RPV infections and RPV delta SPI-2 mutant infections examined to date. Although the SPI-1 gene is expressed early, before DNA replication, the triggering apoptotic event occurs late in the infection, as RPV delta SPI-1-infected A549 cells do not undergo apoptosis when infections are carried out in the presence of cytosine arabinoside. While the SPI-2 (crmA) gene, when transfected into cells, has been shown to inhibit apoptosis, our experiments provide the first indication that a poxvirus serpin protein can inhibit apoptosis during a poxvirus infection.

The SPI-1 gene of rabbitpox virus determines host range and is required for hemorrhagic pock formation

Wild-type rabbitpox virus (RPV) and cowpox virus (CPV) produce red hemorrhagic lesions or pocks upon infection of the chicken chorioallantoic membrane (CAM) of 11-day-old embryonated chicken eggs. However, white, nonhemorrhagic pock variants arise spontaneously within wild-type (wt) populations of either virus at a frequency of about 1%, reflective of complex deletions/rearrangements in the termini of the viral DNA. A subpopulation of the RPV white-pock mutants fail to plaque on pig kidney (PK-15) cells and are referred to as host-range (hr) mutants. In the case of CPV, white-pock formation has been linked to mutations in the SPI-2 (crmA) gene. We show that five spontaneous RPV white-pock host-range mutants (RPV mu hr8sm, RPV mu hr23, RPV mu hr28, RPV mu hr30, and RPV mu hr31) each contain a SPI-2 (crmA) gene and express the crmA protein but lack instead a functional SPI-1 gene. Two other spontaneous RPV white-pock mutants, RPV mu 9 and RPV mu 12, which plaque on PK-15 cells (nonhost-range mutants) contain and express a SPI-1 gene but lack instead a functional SPI-2 gene. Targeted disruption of either the SPI-1 or SPI-2 genes of wtRPV, but only the SPI-2 gene of wtCPV, generates mutants which produce white pocks. The RPV delta SPI-1 mutant fails to plaque on PK-15 or human A549 cells, whereas the RPV delta SPI-2 mutant has a normal host range. No changes in host range compared to wtCPV for either the CPV delta SPI-1 or CPV delta SPI-2 mutants were noted. These differences in phenotypes observed between the two viruses may be reflective of either small sequence variations between the highly conserved SPI-1 or SPI-2 genes or the aggregate phenotypes provided by the other remaining genes.

The effects of serpin gene mutations on the distinctive pathobiology of cowpox and rabbitpox virus following intranasal inoculation of Balb/c mice

Intranasal infection of Balb/c mice with 106 plaque forming units (PFU) of wild-type cowpox virus (CPV) and rabbitpox virus (RPV) induced strikingly different pulmonary pathology despite nearly identical clinical signs of illness and LD50. Intranasal infection with CPV induced severe peribronchial, peribronchiolar, and perivascular hemorrhage with a mixed inflammatory cell infiltrate, bronchial and bronchiolar epithelial cell hyperplasia with intracytoplasmic acidophilic inclusion bodies, and alveolar hemorrhage and edema. In contrast, infection with RPV induced a mixed peribronchial and peribronchiolar inflammatory cell infiltrate, multifocal areas of bronchiolar epithelial cell coagulation necrosis, alveolar edema, and a conspicuous absence of pulmonary hemorrhage. Viremia was not detected following CPV infection and only 1 of 11 mice had brain-associated virus at death. Mice infected with RPV exhibited a viremia 2-3 days after infection and all mice had virus associated with the brain at death. Mice infected with viruses containing certain serine protease inhibitor (SPI) gene mutations (CPV delta SPI-1, CPV delta SPI-3, and RPV SPI-1-) exhibited no difference in clinical disease manifestation when compared with those infected with wild-type viruses. However, inactivation of the SPI-2 genes in either CPV or RPV resulted in disease attenuation and alteration of pulmonary pathology. Mice infected with the CPV delta SPI-2 mutant showed decreased pulmonary hemorrhage, reduced inflammation, and an absence of alveolar edema, while mice infected with the RPV delta SPI-2 mutant had a marked increase in intrapulmonary inflammatory cells and only a transient viremia.

Bacterial metabolism of carbofuran

Fifteen bacteria capable of degrading carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) were isolated from soil samples with a history of pesticide application. All isolates were gram negative and were oxidase- and catalase-positive rods; they occurred singly or as short chains. All of the identified isolates belonged to one of two genera, Pseudomonas and Flavobacterium. They were separated into three groups based on their mode of utilization of carbofuran. Six isolates were placed in group I; these isolates utilized carbofuran as a sole source of nitrogen. Seven isolates were placed in group II; these isolates utilized the pesticide as a sole source of carbon. Isolates of both groups I and II hydrolyzed carbofuran to carbofuran phenol. Two isolates, designated group III, also utilized carbofuran as a sole source of carbon. They degraded the pesticide more rapidly, however, so up to 40% of [14C]carbofuran was lost as 14CO2 in 1 h. The results suggest that these isolates degrade carbofuran by utilizing an oxidative pathway.

Isolation of a methyl parathion-degrading Pseudomonas sp. that possesses DNA homologous to the opd gene from a Flavobacterium sp

Two mixed bacterial cultures isolated by soil enrichment were capable of utilizing methyl parathion (O,O-dimethyl O-p-nitrophenylphosphorothioate) and parathion (O,O-diethyl O-p-nitrophenylphosphorothioate) as a sole source of carbon. Four isolates from these mixed cultures lost their ability to utilize the pesticides independently in transfers subsequent to the initial isolation. One member of the mixed cultures, a Pseudomonas sp., however, hydrolyzed the pesticides to p-nitrophenol but required glucose or another carbon source for growth. The crude cell extracts prepared from this bacterium showed an optimum pH range from 7.5 to 9.5 for the enzymatic hydrolysis. Maximum enzymatic activity occurred between 35 and 40 degrees C. The enzyme activity was not inhibited by heavy metals, EDTA, or NaN3. Another isolate from the mixed cultures, a Flavobacterium sp., used p-nitrophenol for growth and degraded it to nitrite. Nitrite was assimilated into the cells under conditions during which the nitrogen source was excluded from the minimal growth medium. The hybridization data showed that the DNAs from a Pseudomonas sp. and from the mixed culture had homology with the opd (organophosphate degradation) gene from a previously reported parathion-hydrolyzing bacterium, Flavobacterium sp. The use of the opd gene as a probe may accelerate progress toward understanding the complex interactions of soil microorganisms with parathions.