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Daniel Nelson

Publications and source records attributed to Daniel Nelson.

14 recordsLinked to original sources
PubMed2006

The 1.6 A crystal structure of the catalytic domain of PlyB, a bacteriophage lysin active against Bacillus anthracis.

Lysins are peptidoglycan hydrolases that are produced by bacteriophage and act to lyse the bacterial host cell wall during progeny phage release. Here, we describe the structure and function of a novel bacteriophage-derived lysin, PlyB, which displays potent lytic activity against the Bacillus anthracis-like strain ATCC 4342. This molecule comprises an N-terminal catalytic domain (PlyB(cat)) and a C-terminal bacterial SH3-like domain, SH3b. It is shown that both domains are required for effective catalytic activity against ATCC 4342. Further, PlyB has specific activity comparable to the phage lysin PlyG, an amidase being developed as a therapeutic against anthrax. In contrast to PlyG, however, the 1.6 A X-ray crystal structure of PlyB(cat) reveals that the catalytic domain adopts the glycosyl hydrolase (GH)-25, rather than phage T7 lysozyme-like fold. PlyB therefore represents a new class of anthrax lysin and a new defensive tool in the armament against anthrax-mediated bioterrorism.

Amino Acid Sequence↗
PubMed2006

PlyC: a multimeric bacteriophage lysin.

Lysins are murein hydrolases produced by bacteriophage that act on the bacterial host cell wall to release progeny phage. When added extrinsically in their purified form, these enzymes produce total lysis of susceptible Gram-positive bacteria within seconds, suggesting a unique antimicrobial strategy. All known Gram-positive lysins are produced as a single polypeptide containing a catalytic activity domain, which cleaves one of the four major peptidoglycan bonds, and a cell-wall-binding domain, which may bind a species-specific carbohydrate epitope in the cell wall. Here, we have cloned and expressed a unique lysin from the streptococcal bacteriophage C(1), termed PlyC. Molecular characterization of the plyC operon reveals that PlyC is, surprisingly, composed of two separate gene products, PlyCA and PlyCB. Based on biochemical and biophysical studies, the catalytically active PlyC holoenzyme is composed of eight PlyCB subunits for each PlyCA. Inhibitor studies predicted the presence of an active-site cysteine, and bioinformatic analysis revealed a cysteine, histidine-dependent amidohydrolase/peptidase domain within PlyCA. Point mutagenesis confirmed that PlyCA is responsible for the observed catalytic activity, and Cys-333 and His-420 are the active-site residues. PlyCB was found to self-assemble into an octamer, and this complex alone was able to direct streptococcal cell-wall-specific binding. Similar to no other proteins in sequence databases, PlyC defines a previously uncharacterized structural family of cell-wall hydrolases.

Cell Wall↗
PubMed2005

Group A streptococcus (GAS) carbohydrate as an immunogen for protection against GAS infection.

Previous studies have shown that human serum containing anti-group A streptococcus carbohydrate (GAS CHO) antibodies were opsonic for different M protein-carrying serotypes. To investigate the role that anti-GAS CHO antibodies play in passive and active protection, mice were immunized subcutaneously or intranasally with GAS CHO conjugated to tetanus toxoid, and mortality and oral colonization were monitored after challenge with live GAS. Compared with control mice, immunized mice were significantly protected against systemic or nasal challenge with GAS. Furthermore, studies of serum samples and throat cultures from Mexican children revealed an inverse relationship between high serum titers of anti-GAS CHO antibodies and the presence of GAS in the throat. Anti-GAS CHO antibodies were also tested for cross-reactivity with human tissues and cytoskeletal proteins. No cross-reactivity was observed in either assay. The present study demonstrates that GAS CHO is both immunogenic and protective against GAS infections.

Adolescent↗
PubMed2005

Impulsive aggression with irritability and responsive to divalproex: a pediatric bipolar spectrum disorder phenotype?

BACKGROUND: The objective of this retrospective chart review was to evaluate the phenomenology and response to divalproex in a sub-population of children admitted to an inpatient setting with severe impairing symptoms of irritability and aggression. In addition, we examined whether the symptomatology of this group was consistent with a pediatric divalproex-responsive bipolar spectrum disorder. METHODS: The charts of 46 child and adolescent patients with prominent impulsive aggression with irritability admitted to a crisis stabilization center were assessed retrospectively. Impulsive aggressive symptoms were assessed for admission and discharge severity by two clinicians using the Overt Aggression Scale (OAS) and the Anger-Hostility Subscale of the SCL-90 (SCL-A), with overall functioning changes assessed using the Children's Global Assessment Scale (C-GAS). RESULTS: Statistically significant improvements were obtained for the group in the C-GAS, with significant decreases in the OAS and the SCL-A scores at discharge, following a maximal 14-day stay. No severe side effects were reported. All patients met the criteria for a potential pediatric bipolar phenotype. LIMITATIONS: This was a retrospective study without randomization or a control group. Additionally, the non-blinded design may have biased the raters concerning the effectiveness of divalproex for impulsive aggression. CONCLUSIONS: Our data are in line with divalproex response in children and adolescents with target symptoms of explosive temper and mood instability. Our data further suggest that such symptoms, coupled with impulsive aggression and irritability, as well as related manic symptoms, constitute a pediatric divalproex-responsive bipolar spectrum disorder.

Adolescent↗
PubMed2005

Removal of group B streptococci colonizing the vagina and oropharynx of mice with a bacteriophage lytic enzyme.

Group B streptococci (GBS) are the leading cause of neonatal meningitis and sepsis worldwide. The current treatment strategy is limited to intrapartum antibiotic prophylaxis in pregnant women to prevent early-onset neonatal diseases, but considering the potential for antibiotic resistance, the risk of losing control over the disease is high. To approach this problem, we have developed a bacteriophage (phage) lytic enzyme to remove colonizing GBS. Bacteriophage muralytic enzymes, termed lysins, are highly evolved molecules designed to degrade the cell wall of host bacteria to release phage particles from the bacterial cytoplasm. Several different lysins have been developed to specifically kill bacterial pathogens both on mucosal surfaces and in blood and represent a novel approach to control infection. A lysin cloned from a phage infecting GBS was found to contain two putative catalytic domains and one putative binding domain, which is similar to the domain organization of some staphylococcal phage lysins. The lysin (named PlyGBS) was recombinantly expressed in Escherichia coli, and purified PlyGBS efficiently killed all tested GBS serotypes in vitro. In a mouse model, a single dose of PlyGBS significantly reduced bacterial colonization in both the vagina and oropharynx. As an alternative strategy for intrapartum antibiotic prophylaxis, this approach may be used to reduce vaginal GBS colonization in pregnant women before delivery or to decontaminate newborns, thus reducing the incidence of GBS-associated neonatal meningitis and sepsis.

Animals↗
PubMed2004

XBP1 is essential for survival under hypoxic conditions and is required for tumor growth.

Hypoxia within solid tumors is a major determinant of outcome after anticancer therapy. Analysis of gene expression changes during hypoxia indicated that unfolded protein response genes were one of the most robustly induced groups of genes. In this study, we investigated the hypoxic regulation of X-box binding protein (XBP1), a major transcriptional regulator of the unfolded protein response. Hypoxia induced XBP1 at the transcriptional level and activated splicing of its mRNA, resulting in increased levels of activated XBP1 protein. After exposure to hypoxia, apoptosis increased and clonogenic survival decreased in XBP1-deficient cells. Loss of XBP1 severely inhibited tumor growth due to a reduced capacity for these transplanted tumor cells to survive in a hypoxic microenvironment. Taken together, these studies directly implicate XBP1 as an essential survival factor for hypoxic stress and tumor growth.

Alternative Splicing↗
PubMed2004

Identification of a broadly active phage lytic enzyme with lethal activity against antibiotic-resistant Enterococcus faecalis and Enterococcus faecium.

Enterococcus faecalis and Enterococcus faecium infections are increasingly difficult to treat due to high levels of resistance to antibiotics. PlyV12, a bacteriophage lytic enzyme, was isolated and shown to effectively kill both E. faecalis and E. faecium (including vancomycin-resistant strains), as well as other human pathogens. We propose its development and use as an alternative therapeutic tool.

Amino Acid Sequence↗
PubMed2003

Genomic sequence of C1, the first streptococcal phage.

C(1), a lytic bacteriophage infecting group C streptococci, is one of the earliest-isolated phages, and the method of bacterial classification known as phage typing was defined by using this bacteriophage. We present for the first time a detailed analysis of this phage by use of electron microscopy, protein profiling, and complete nucleotide sequencing. This virus belongs to the Podoviridae family of phages, all of which are characterized by short, noncontractile tails. The C(1) genome consists of a linear double-stranded DNA molecule of 16,687 nucleotides with 143-bp inverted terminal repeats. We have assigned functions to 9 of 20 putative open reading frames based on experimental substantiation or bioinformatic analysis. Their products include DNA polymerase, holin, lysin, major capsid, head-tail connector, neck appendage, and major tail proteins. Additionally, we found one intron belonging to the HNH endonuclease family interrupting the apparent lysin gene, suggesting a potential splicing event yielding a functional lytic enzyme. Examination of the C(1) DNA polymerase suggests that this phage utilizes a protein-primed mechanism of replication, which is prominent in the phi29-like members of Podoviridae. Consistent with this evidence, we experimentally determined that terminal proteins are covalently attached to both 5' termini, despite the fact that no homology to known terminal proteins could be elucidated in any of our open reading frames. Likewise, comparative genomics revealed no close evolutionary matches, suggesting that the C(1) bacteriophage is a unique member of the Podoviridae.

Animals↗
PubMed2003

The relationship between habitual patient-reported symptoms and clinical signs among patients with dry eye of varying severity.

PURPOSE: To investigate symptom profiles and clinical signs in subjects with dry eye and normal subjects in a cross-sectional multicenter study. METHODS: Subjects aged 35 to 65 were recruited according to dry eye diagnostic codes and telephone interview and completed the Dry Eye Questionnaire 2001, among others, and underwent dry eye clinical tests. RESULTS: Subjects (122) included 28 control subjects (C), 73 with non-Sjögren's keratoconjunctivitis sicca (non-SS KCS) and 21 with Sjögren's syndrome (SS). Subjects with SS or non-SS KCS reported discomfort and dryness most frequently and that many symptoms worsened over the day and were quite bothersome. Groups were significantly different in corneal fluorescein staining, conjunctival lissamine green staining, Schirmer 1 tear test, and tear break-up time (TBUT; chi2 and Kruskal-Wallis, P<0.0001). Statistically significant, but moderate, correlations were found between the frequency and evening intensity of dryness and discomfort and TBUT, Schirmer's tear test, overall corneal fluorescein staining, and temporal lissamine green conjunctival staining (Spearman r=0.31-0.45, P<0.01). Symptoms were moderately to highly correlated with the clinician's global grading of severity and highly correlated to patient's self-assessment of severity (r=0.46-0.86, P<0.0001), whereas signs showed lower correlations (r=0.22-0.46, P<0.0001). CONCLUSIONS: Subjects with SS or non-SS KCS reported frequent and intense ocular surface symptoms in the evening, some of which correlated moderately with clinical test results. The global clinician grade of dry eye correlated more highly with patient symptoms than did clinical signs, suggesting that patient symptoms influence dry eye diagnosis and grading of dry eye more than clinical test results.

Adult↗
PubMed2002

A bacteriolytic agent that detects and kills Bacillus anthracis.

The dormant and durable spore form of Bacillus anthracis is an ideal biological weapon of mass destruction. Once inhaled, spores are transported by alveolar macrophages to lymph nodes surrounding the lungs, where they germinate; subsequent vegetative expansion causes an overwhelming flood of bacteria and toxins into the blood, killing up to 99% of untreated victims. Natural and genetically engineered antibiotic-resistant bacilli amplify the threat of spores being used as weapons, and heighten the need for improved treatments and spore-detection methods after an intentional release. We exploited the inherent binding specificity and lytic action of bacteriophage enzymes called lysins for the rapid detection and killing of B. anthracis. Here we show that the PlyG lysin, isolated from the gamma phage of B. anthracis, specifically kills B. anthracis isolates and other members of the B. anthracis 'cluster' of bacilli in vitro and in vivo. Both vegetative cells and germinating spores are susceptible. The lytic specificity of PlyG was also exploited as part of a rapid method for the identification of B. anthracis. We conclude that PlyG is a tool for the treatment and detection of B. anthracis.

Amino Acid Sequence↗