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Biomedical subjects

Richard Malley

Publications and source records attributed to Richard Malley.

At least 19 recordsLinked to original sources
PubMed2007

Clinical prediction rule for identifying children with cerebrospinal fluid pleocytosis at very low risk of bacterial meningitis.

CONTEXT: Children with cerebrospinal fluid (CSF) pleocytosis are routinely admitted to the hospital and treated with parenteral antibiotics, although few have bacterial meningitis. We previously developed a clinical prediction rule, the Bacterial Meningitis Score, that classifies patients at very low risk of bacterial meningitis if they lack all of the following criteria: positive CSF Gram stain, CSF absolute neutrophil count (ANC) of at least 1000 cells/microL, CSF protein of at least 80 mg/dL, peripheral blood ANC of at least 10,000 cells/microL, and a history of seizure before or at the time of presentation. OBJECTIVE: To validate the Bacterial Meningitis Score in the era of widespread pneumococcal conjugate vaccination. DESIGN, SETTING, AND PATIENTS: A multicenter, retrospective cohort study conducted in emergency departments of 20 US academic medical centers through the Pediatric Emergency Medicine Collaborative Research Committee of the American Academy of Pediatrics. All children aged 29 days to 19 years who presented at participating emergency departments between January 1, 2001, and June 30, 2004, with CSF pleocytosis (CSF white blood cells > or =10 cells/microL) and who had not received antibiotic treatment before lumbar puncture. MAIN OUTCOME MEASURE: The sensitivity and negative predictive value of the Bacterial Meningitis Score. RESULTS: Among 3295 patients with CSF pleocytosis, 121 (3.7%; 95% confidence interval [CI], 3.1%-4.4%) had bacterial meningitis and 3174 (96.3%; 95% CI, 95.5%-96.9%) had aseptic meningitis. Of the 1714 patients categorized as very low risk for bacterial meningitis by the Bacterial Meningitis Score, only 2 had bacterial meningitis (sensitivity, 98.3%; 95% CI, 94.2%-99.8%; negative predictive value, 99.9%; 95% CI, 99.6%-100%), and both were younger than 2 months old. A total of 2518 patients (80%) with aseptic meningitis were hospitalized. CONCLUSIONS: This large multicenter study validates the Bacterial Meningitis Score prediction rule in the era of conjugate pneumococcal vaccine as an accurate decision support tool. The risk of bacterial meningitis is very low (0.1%) in patients with none of the criteria. The Bacterial Meningitis Score may be helpful to guide clinical decision making for the management of children presenting to emergency departments with CSF pleocytosis.

Adolescent↗
PubMed2006

Recombinant bactericidal/permeability-increasing protein rBPI21 protects against pneumococcal disease.

Bactericidal/permeability-increasing (BPI) protein has been shown to play an important role in innate immunity to gram-negative bacteria, by direct microbicidal as well as endotoxin-neutralizing action. Here we examined potential interactions between a recombinant 21-kDa bioactive fragment of BPI, rBPI21, and the gram-positive pathogen Streptococcus pneumoniae. rBPI21 bound to pneumococci and pneumolysin (Ply) in a direct and specific fashion. We observed an enhanced inflammatory response in mouse macrophages when rBPI21 was combined with killed pneumococci or supernatant from overnight growth of pneumococci. In addition, rBPI21 augmented the proapoptotic activity of Ply+ (but not Ply-) pneumococci in TLR4-defective murine macrophages (known to be defective also in their apoptotic response to pneumolysin) in a tumor necrosis factor alpha-dependent manner. rBPI21 also enhanced the association of pneumococci with murine macrophages. In a model of invasive pneumococcal disease in TLR4-defective mice, the intranasal administration of rBPI21 following intranasal inoculation of Ply+ pneumococci both enhanced upper respiratory tract cell apoptosis and prolonged survival. We have thus discovered a novel interaction between pneumococcus and rBPI21, a potent antimicrobial peptide previously considered to target only gram-negative bacteria.

Animals↗
PubMed2006

c-Jun kinase is a critical signaling molecule in a neonatal model of group B streptococcal sepsis.

Group B streptococcus (GBS) is the major cause of sepsis in newborn infants. In vitro, inactivated GBS stimulates macrophages to produce inflammatory proteins via the TLR adapter protein MyD88. Furthermore, inflammatory cytokine release in response to GBS greatly exceeds that following stimulation with pneumococci. In this study, we attempted to unravel signaling events that are involved in GBS-, but not Streptococcus pneumoniae-stimulated phagocytes to identify molecular targets for adjunctive sepsis therapy. We found that inactivated GBS and S. pneumoniae differed in the activation of the MAPK JNK, but not IkappaB kinase. Furthermore, JNK was essential for the transcriptional activation of inflammatory cytokine genes in response to GBS. Inhibition of JNK by the anthrapyrazolone SP600125 abrogated GBS-induced cytokine formation via an AP-1- and NF-kappaB-dependent mechanism without impairing antibacterial properties such as phagocytosis of GBS and the formation of intracellular oxidative species. In contrast, inhibition of the MAPK p38 impaired both antibacterial processes. In a neonatal mouse model of GBS sepsis SP600125 inhibited the inflammatory response and improved survival. In conclusion, JNK plays a major role in the inflammatory, but not in the direct antibacterial response to inactivated GBS, and may thus serve as a rational target for an adjunctive GBS sepsis therapy.

Animals↗
PubMed2006

Antibody-independent, interleukin-17A-mediated, cross-serotype immunity to pneumococci in mice immunized intranasally with the cell wall polysaccharide.

Serotype-specific immunity to Streptococcus pneumoniae is conferred by antibodies to the capsular polysaccharides, which define the 90 known serotypes. Whether antibody to the species-common cell wall polysaccharide (C-Ps) is protective has been a matter of controversy. Here we show that C-Ps given intranasally with mucosal adjuvant increased the resistance of mice to experimental nasopharyngeal colonization by capsulated S. pneumoniae of serotype 6B. This immunity could be induced in mice congenitally lacking immunoglobulin but was dependent upon CD4+ T cells. Elimination of the charged amino group on the polymer backbone by N acetylation of C-Ps reduced the immunity, as did treatment of the mice with antibody to the cytokine interleukin-17A at the time of challenge, both consistent with the hypothesis of T-cell activation due to the zwitterionic motif of the polymer. C-Ps also protected in a model of fatal aspiration pneumonia by heavily capsulated serotype 3. These findings suggest a novel immunization strategy against S. pneumoniae.

Administration, Intranasal↗
PubMed2006

Interference between Streptococcus pneumoniae and Staphylococcus aureus: In vitro hydrogen peroxide-mediated killing by Streptococcus pneumoniae.

The bactericidal activity of Streptococcus pneumoniae toward Staphylococcus aureus is mediated by hydrogen peroxide. Catalase eliminated this activity. Pneumococci grown anaerobically or genetically lacking pyruvate oxidase (SpxB) were not bactericidal, nor were nonpneumococcal streptococci. These results provide a possible mechanistic explanation for the interspecies interference observed in epidemiologic studies.

Antibiosis↗
PubMed2005

CD4+ T cells mediate antibody-independent acquired immunity to pneumococcal colonization.

Acquired immunity to Streptococcus pneumoniae (pneumococcus) has long been assumed to depend on the presence of anticapsular antibodies. We found, however, that colonization with live pneumococci of serotypes 6B, 7F, or 14 protected mice against recolonization by any of the serotypes and that protection from acquisition of a heterologous or homologous strain did not depend on anticapsular antibody. Further, intranasal immunization by live pneumococcal colonization or by a killed, nonencapsulated whole-cell vaccine protected antibody-deficient mice against colonization, suggesting independence of antibodies to any pneumococcal antigens. Protection by intranasal immunization with whole-cell vaccine was completely abrogated in T cell-deficient mice, and in mice that were congenitally deficient in CD4(+) T cells or depleted of these cells at the time of challenge. In contrast, mice congenitally deficient in, or depleted of, CD8(+) T cells were fully protected. Protection in this model was observed beyond 2 months after immunization, arguing against innate or nonspecific immune mechanisms. Thus, we find that immunity to pneumococcal colonization can be induced in the absence of antibody, independent of the capsular type, and this protection requires the presence of CD4(+) T cells at the time of challenge.

Administration, Intranasal↗
PubMed2005

Are anticapsular antibodies the primary mechanism of protection against invasive pneumococcal disease?

BACKGROUND: Antibody to capsular polysaccharide has been the basis of several vaccines that offer protection against invasive disease from Streptococcus pneumoniae. The success of such vaccines has led to the inference that natural protection against invasive pneumococcal disease is largely conferred by anticapsular antibody. If this is so, one would expect that the decline in disease from different serotypes would vary significantly, and that the appearance of substantial concentrations of anticapsular antibodies would coincide temporally with the decline in age-specific incidence. METHODS AND FINDINGS: Using incidence data from the United States, we show that, on the contrary, the decline in incidence with age is quite similar for the seven most important serogroups, despite large differences in exposure in the population. Moreover, only modest increases in antibody concentration occur over the second and third years of life, a period in which serotype-specific incidence declines to less than 25% of its peak. We also present detailed data on the distribution of antibody concentrations in Israeli toddlers, which are consistent with the United States findings. The same conclusion is supported by new data on age-specific incidence in Finland, which is compared with published data on antibody acquisition in Finnish toddlers. CONCLUSION: We suggest some additional studies of the mechanisms of protection that could distinguish among potential alternative mechanisms, including acquired immunity to noncapsular antigens, maturation of nonspecific immune responses, or changes in anatomy or exposure.

Age Factors↗
PubMed2005

The apoptotic response to pneumolysin is Toll-like receptor 4 dependent and protects against pneumococcal disease.

Pneumolysin, the cholesterol-dependent cytolysin of Streptococcus pneumoniae, induces inflammatory and apoptotic events in mammalian cells. Toll-like receptor 4 (TLR4) confers resistance to pneumococcal infection via its interaction with pneumolysin, but the underlying mechanisms remain to be identified. In the present study, we found that pneumolysin-induced apoptosis is also mediated by TLR4 and confers protection against invasive disease. The interaction between TLR4 and pneumolysin is direct and specific; ligand-binding studies demonstrated that pneumolysin binds to TLR4 but not to TLR2. Involvement of TLR4 in pneumolysin-induced apoptosis was demonstrated in several complementary experiments. First, macrophages from wild-type mice were significantly more prone to pneumolysin-induced apoptosis than cells from TLR4-defective mice. In gain-of-function experiments, we found that epithelial cells expressing TLR4 and stimulated with pneumolysin were more likely to undergo apoptosis than cells expressing TLR2. A specific TLR4 antagonist, B1287, reduced pneumolysin-mediated apoptosis in wild-type cells. This apoptotic response was also partially caspase dependent as preincubation of cells with the pan-caspase inhibitor zVAD-fmk reduced pneumolysin-induced apoptosis. Finally, in a mouse model of pneumococcal infection, pneumolysin-producing pneumococci elicited significantly more upper respiratory tract cell apoptosis in wild-type mice than in TLR4-defective mice, and blocking apoptosis by administration of zVAD-fmk to wild-type mice resulted in a significant increase in mortality following nasopharyngeal pneumococcal exposure. Overall, our results strongly suggest that protection against pneumococcal disease is dependent on the TLR4-mediated enhancement of pneumolysin-induced apoptosis.

Amino Acid Chloromethyl Ketones↗
PubMed2005

Antibodies to conserved pneumococcal antigens correlate with, but are not required for, protection against pneumococcal colonization induced by prior exposure in a mouse model.

In mice following intranasal exposure to Streptococcus pneumoniae, protection against pneumococcal colonization was independent of antibody but dependent on CD4(+) T cells. Nonetheless, concentrations of antibodies to three conserved pneumococcal antigens correlated with protection against colonization. Concentrations of antibodies to conserved pneumococcal antigens may be correlates of protection without being effectors of protection.

Animals↗
PubMed2004

Development of a model of focal pneumococcal pneumonia in young rats.

BACKGROUND: A recently licensed pneumococcal conjugate vaccine has been shown to be highly effective in the prevention of bacteremia in immunized children but the degree of protection against pneumonia has been difficult to determine. METHODS: We sought to develop a model of Streptococcus pneumoniae pneumonia in Sprague-Dawley rats. We challenged three-week old Sprague-Dawley pups via intrapulmonary injection of S. pneumoniae serotypes 3 and 6B. Outcomes included bacteremia, mortality as well histologic sections of the lungs. RESULTS: Pneumonia was reliably produced in animals receiving either 10 or 100 cfu of type 3 pneumococci, with 30% and 50% mortality respectively. Similarly, with type 6B, the likelihood of pneumonia increased with the inoculum, as did the mortality rate. Prophylactic administration of a preparation of high-titered anticapsular antibody prevented the development of type 3 pneumonia and death. CONCLUSION: We propose that this model may be useful for the evaluation of vaccines for the prevention of pneumococcal pneumonia.

Journal Article↗
PubMed2004

Cerebrospinal latex agglutination fails to contribute to the microbiologic diagnosis of pretreated children with meningitis.

We conducted a 10-year retrospective study of all children who had cerebrospinal fluid latex agglutination testing for bacterial antigens performed at 1 tertiary care urban children's hospital. Of the 176 patients with culture-negative meningitis who were pretreated with antibiotics before lumbar puncture, none had a positive latex agglutination study (0 of 176; 95% confidence interval, 0-2%). Latex agglutination studies identified no additional cases of bacterial meningitis beyond those identified by culture in pretreated patients. Clinical decision-making algorithms for the management of pretreated patients at risk for bacterial meningitis should not include latex agglutination testing.

Adolescent↗
PubMed2004

Multiserotype protection of mice against pneumococcal colonization of the nasopharynx and middle ear by killed nonencapsulated cells given intranasally with a nontoxic adjuvant.

Intranasal challenge of C57BL/6 mice with Streptococcus pneumoniae serotypes 6B, 14, and 23F produced colonization of the middle ear and NP. Intranasal vaccination with ethanol-killed nonencapsulated cells with adjuvant protected both sites. Of four nontoxic adjuvants tested, the cholera toxin B subunit was most effective and least nonspecifically protective.

Adjuvants, Immunologic↗
PubMed2003

Recognition of pneumolysin by Toll-like receptor 4 confers resistance to pneumococcal infection.

Streptococcus pneumoniae is one of the leading causes of invasive bacterial disease worldwide. Fragments of the cell wall and the cytolytic toxin pneumolysin have been shown to contribute substantially to inflammatory damage, although the interactions between pneumococcal components and host-cell structures have not been elucidated completely. Results of a previous study indicated that cell-wall components of pneumococci are recognized by Toll-like receptor (TLR)2 but suggested that pneumolysin induces inflammatory events independently of this receptor. In this study we tested the hypothesis that pneumolysin interacts with surface proteins of the TLR family other than TLR2. We found that pneumolysin stimulates tumor necrosis factor-alpha and IL-6 release in wild-type macrophages but not in macrophages from mice with a targeted deletion of the cytoplasmic TLR-adapter molecule myeloid differentiation factor 88, suggesting the involvement of the TLRs in pneumolysin recognition. Purified pneumolysin synergistically activated macrophage responses together with preparations of pneumococcal cell walls or staphylococcal peptidoglycan, which are known to activate TLR2. Furthermore, when compared with wild-type macrophages, macrophages from mice that carry a spontaneous mutation in TLR4 (P712H) were hyporesponsive to both pneumolysin alone and the combination of pneumolysin with pneumococcal cell walls. Finally, these TLR4-mutant mice were significantly more susceptible to lethal infection after intranasal colonization with pneumolysin-positive pneumococci than were control mice. We conclude that the interaction of pneumolysin with TLR4 is critically involved in the innate immune response to pneumococcus.

Animals↗
PubMed2002

Cellular activation, phagocytosis, and bactericidal activity against group B streptococcus involve parallel myeloid differentiation factor 88-dependent and independent signaling pathways.

Group B streptococci (GBS) vigorously activate inflammatory responses. We reported previously that a secreted GBS "factor" activates phagocytes via Toll-like receptor (TLR)2 and TLR6, but that GBS cell walls activate cells independently of these receptors. We hypothesized that the phagocytic immune functions in response to GBS, such as inflammation, uptake, and elimination of bacteria, occur through a coordinated engagement of TLRs, along with the coreceptors CD14 and CD11b/CD18. Using various knockout mice we show that GBS-induced activation of p38 and NF-kappaB depends upon the expression of the cytoplasmic TLR adapter protein, myeloid differentiation factor 88 (MyD88), but not TLR2 and/or TLR4. Macrophages with deletions of CD14 and complement receptor 3 had a normal cytokine response to whole bacteria, although the response to GBS factor was abrogated in CD14-null cells. The intracellular formation of bactericidal oxygen species proved to be MyD88 dependent; however, uptake of GBS, a prerequisite for intracellular killing by O(2) radicals, occurred independently of MyD88. While deletion of complement receptor 3 greatly diminished the uptake of opsonized GBS, it did not affect the formation of bactericidal O(2) radicals or inflammatory signaling intermediates. We conclude that the inflammatory, bactericidal, and phagocytic responses to GBS occur via parallel but independent processes.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Donor immunization with pneumococcal conjugate vaccine and early protective antibody responses following allogeneic hematopoietic cell transplantation.

Patients undergoing hematopoietic cell transplantation (HCT) are at increased risk for infections with Streptococcus pneumoniae and have long-lasting, impaired antibody responses to pneumococcal polysaccharide vaccines. We examined whether donor immunization with a heptavalent pneumococcal conjugate vaccine (PCV7) would elicit protective antibody responses to additional doses of vaccine administered early after transplantation. Ninety-six patients scheduled to receive an allogeneic hematopoietic cell transplant were randomized with their donors to receive either a dose of PCV7 vaccine or no vaccine before transplantation. All patients received PCV7 at 3 months, 6 months, and 12 months following transplantation, and serotype-specific antibody concentrations were determined after each dose. Following HCT, geometric mean antibody concentrations of patients in the immunized donor group were significantly higher for 5 of the 7 vaccine serotypes after one dose (P <.05) and for 4 of the 7 serotypes after 2 doses of vaccine (P <.03). Sixty-seven percent of patients in the immunized donor group had presumed protective IgG concentrations more than or equal to 0.50 microg/mL to all 7 serotypes following the first dose of vaccine compared to 36% in the unimmunized donor group (P =.05). After the third dose of vaccine, both groups had more than 60% of patients with concentrations at least 0.50 microg/mL to all vaccine serotypes. Donor immunization enhances early antibody responses of patients undergoing HCT to pneumococcal conjugate vaccine. A 3-dose schedule of PCV7 vaccine at 3, 6, and 12 months is immunogenic in these patients regardless of donor immunization.

Adolescent↗
PubMed2002

Comparison of prediction models for adverse outcome in pediatric meningococcal disease using artificial neural network and logistic regression analyses.

The objective of this study was to compare artificial neural network (ANN) and multivariable logistic regression analyses for prediction modeling of adverse outcome in pediatric meningococcal disease. We analyzed a previously constructed database of children younger than 20 years of age with meningococcal disease at four pediatric referral hospitals from 1985-1996. Patients were randomly divided into derivation and validation datasets. Adverse outcome was defined as death or limb amputation. ANN and multivariable logistic regression models were developed using the derivation set, and were tested on the validation set. Eight variables associated with adverse outcome in previous studies of meningococcal disease were considered in both the ANN and logistic regression analyses. Accuracies of these models were then compared. There were 381 patients with meningococcal disease in the database, of whom 50 had adverse outcomes. When applied to the validation data set, the sensitivities for both the ANN and logistic regressions models were 75% and the specificities were both 91%. There were no significant differences in any of the performance parameters between the two models. ANN analysis is an effective tool for developing prediction models for adverse outcome of meningococcal disease in children, and has similar accuracy as logistic regression modeling. With larger, more complete databases, and with advanced ANN algorithms, this technology may become increasingly useful for real-time prediction of patient outcome.

Adolescent↗
PubMed2002

Factors associated with adverse outcomes in children with diabetic ketoacidosis-related cerebral edema.

OBJECTIVE: To investigate the relation between outcomes of children with diabetic ketoacidosis (DKA)-related cerebral edema and baseline clinical features and therapeutic interventions for treatment of cerebral edema. STUDY DESIGN: All children </=18 years old with DKA and cerebral edema (n = 61) were retrospectively identified from 10 pediatric centers between 1982 and 1997. Demographic, biochemical, and therapeutic data were collected. Ordinal logistic regression analysis was used to identify factors associated with the clinical outcome (death or persistent vegetative state; mild to moderate neurological disability; or normal) after adjusting for known risk factors for the development of cerebral edema as well as the degree of neurologic depression at the time of diagnosis of cerebral edema. RESULTS: Seventeen (28%) children died or survived in a vegetative state; 8 (13%) survived with mild to moderate neurologic disabilities; and 36 (59%) survived without sequelae. Factors associated with poor outcomes included greater neurologic depression at the time of diagnosis of cerebral edema, a high initial serum urea nitrogen concentration, and intubation with hyperventilation to a PCO (2) <22 mm Hg. CONCLUSIONS: After adjusting for potential confounding variables and the degree of neurologic compromise at the initiation of therapy, intubation with hyperventilation is associated with adverse outcomes of DKA-related cerebral edema. Greater neurologic depression at the time of diagnosis of cerebral edema and a higher initial serum urea nitrogen concentration are also associated with poor outcome.

Adolescent↗