Robert Allen | Creighton University (original) (raw)

Papers by Robert Allen

Journal of Antimicrobial Agents, 2021

E-101 solution is a first-in-class myeloperoxidase containing antimicrobial solution developed fo... more E-101 solution is a first-in-class myeloperoxidase containing antimicrobial solution developed for topical application. The active ingredients in E-101 solution are two enzymes, porcine myeloperoxidase (pMPO) and glucose oxidase (GO) in an aqueous solution and activated by the addition of a glucose solution. Once activated, the reactive species hydrogen peroxide, hypochlorous acid/hypochlorite (HOCl/OCl-), and singlet oxygen (1 O 2) are generated. We evaluated the effect of whole human blood on the performance of E-101 solution compared to commercially available wound antiseptics and commonly used biocides. The wound cleansers NeutroPhase, Microcyn, and Vashe with the active HOCl/OClcomponent were tested according to the USP-51 effectiveness test in the presence of 0, 1, 2 and 5% blood. Comparative time-kill studies against chlorhexidine, povidone-iodine, sodium oxychlorosene were tested in the presence of 0, 2, 5 10, and 20% blood. In the USP-51 test, E-101 solution demonstrated >2 log10 reduction against bacterial and fungal isolates in the presence of 5% blood at days 14 and 28. With the exception of NeutroPhase activity against S. aureus, all comparable wound antiseptics demonstrated <2 log10 reduction in the presence of 5% blood at days 14 and 28. Time-kill microbicidal data observed in the presence of blood demonstrated that E-101 solution was the most active biocide, followed by chlorhexidine and povidone-iodine. The presence of 2% blood completely inhibited the activity of sodium oxychlorosene. In summary, E-101 solution remained active in the presence of blood containing catalase and other substances that competitively react with 1 O 2 and HOCl/OClas a safe and effective wound antiseptic.

Journal of Medical Microbiology and Diagnosis, Nov 6, 2017

Infection and Immunity, 2011

Myeloperoxidase (MPO) is reported to selectively bind to bacteria. The present study provides dir... more Myeloperoxidase (MPO) is reported to selectively bind to bacteria. The present study provides direct evidence of MPO binding selectivity and tests the relationship of selective binding to selective killing. The microbicidal effectiveness of H 2 O 2 and of OCl ؊ was compared to that of MPO plus H 2 O 2. Synergistic microbicidal action was investigated by combining Streptococcus sanguinis, a H 2 O 2-producing microbe showing low MPO binding, with high-MPO-binding Escherichia coli, Staphylococcus aureus, or Pseudomonas aeruginosa without exogenous H 2 O 2 , with and without MPO, and with and without erythrocytes (red blood cells [RBCs]). Selectivity of MPO microbicidal action was conventionally measured as the MPO MIC and minimal bactericidal concentration (MBC) for 82 bacteria including E. coli, P. aeruginosa, S. aureus, Enterococcus faecalis, Streptococcus pyogenes, Streptococcus agalactiae, and viridans streptococci. Both H 2 O 2 and OCl ؊ destroyed RBCs at submicrobicidal concentrations. Nanomolar concentrations of MPO increased H 2 O 2 microbicidal action 1,000-fold. Streptococci plus MPO produced potent synergistic microbicidal action against all microbes tested, and RBCs caused only a small decrease in potency without erythrocyte damage. MPO directly killed H 2 O 2producing S. pyogenes but was ineffective against non-H 2 O 2-producing E. faecalis. The MPO MICs and MBCs for E. coli, P. aeruginosa, and S. aureus were significantly lower than those for E. faecalis. The streptococcal studies showed much higher MIC/MBC results, but such testing required lysed horse blood-supplemented medium, thus preventing valid comparison of these results to those for the other microbes. E. faecalis MPO binding is reportedly weak compared to binding of E. coli, P. aeruginosa, and S. aureus but strong compared to binding of streptococci. Selective MPO binding results in selective killing.

Research features, 2024

O xygen is essential to the survival of many organisms on Earth, including humans. In our bodies,... more O xygen is essential to the survival of many organisms on Earth, including humans. In our bodies, however, oxygen also acts as a powerful defence weapon against microbial invaders. In the blood, red cells known as erythrocytes carry oxygen molecules throughout the body as required for metabolism, and the white cells, known as neutrophils, respond to microbe infections by migrating to the site of infection, contacting and phagocytosing the microbe, and converting oxygen to reactants responsible for combustive microbicidal oxygenations. Neutrophil oxygenating activity is fast and focused on killing microbial pathogens.

Antioxidants, Mar 8, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

ABSTRACTE-101 Solution is a first in class myeloperoxidase-mediated antimicrobial developed for t... more ABSTRACTE-101 Solution is a first in class myeloperoxidase-mediated antimicrobial developed for topical application. It is composed of porcine myeloperoxidase (pMPO), glucose oxidase (GO), glucose, sodium chloride, and specific amino acids in an aqueous vehicle. Once activated, the reactive species hydrogen peroxide (H2O2), hypochlorous acid and singlet oxygen are generated. We evaluated the treatment effects of E-101 solution and its oxidative products on ultrastucture changes and microbicidal activity against methicillin-resistantStaphylococcus aureus(MRSA) andEscherichia coli. Time kill and transmission electron microscopy studies were performed using formulations with pMPO or GO omitted. The glutathione membrane protection assay was used to study the neutralization of reactive oxygen species. The potency of E-101 solution was also measured in the presence of serum and whole blood by MIC and MBC determinations. E-101 solution demonstrated rapid bactericidal activity and ultracell...

Journal of Leukocyte Biology, 1997

Priming of polymorphonuclear neutrophils (PMN) in whole blood (by tumor necrosis factor α and int... more Priming of polymorphonuclear neutrophils (PMN) in whole blood (by tumor necrosis factor α and interleukin-8 for enhancement of luminoldependent chemiluminescence induced by human complement-opsonized zymosan) was stable for 120 min. In contrast, priming of isolated PMN in plasma-free suspension for responses to opsonized zymosan, formyl-methionyl-leucyl-phenylalanine, and phorbol myristate acetate was markedly less stable. Decay of priming was not due to irreversible inactivation of the terminal CL production machinery because PMN could be reprimed by platelet-activating factor or leukotriene B4. The tumor necrosis factor-α-primed state of isolated PMN was stabilized by host plasma in a concentration-dependent fashion. We conclude that PMN priming results in a dynamic state that is reversible. Our findings suggest the existence of blood-borne components that may act to stabilize or modify PMN priming.

The Journal of Immunology

The present study addresses the question of a possible linkage between the cystic fibrosis (CF) g... more The present study addresses the question of a possible linkage between the cystic fibrosis (CF) genetic autosomal recessive disorder and disturbance in neutrophil function. Neutrophil-dominated chronic airway inflammation is present at an early age in children with CF, even in the absence of detectable infection. As evidenced by extracellular superoxide anion release (measured by lucigenin luminescence) or intracellular hydrogen peroxide production (measured by 2',7'-dichlorofluorescein (DCF) fluorescence), no significant difference in the nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase activity of isolated neutrophils was observed in noninfected CF children (homozygotes), their mothers or fathers (CF heterozygotes), and controls. In contrast, both myeloperoxidase (MPO)-dependent oxygenation activity (measured by luminol luminescence) and chloramine release were increased significantly in both CF homozygotes and heterozygotes as compared with controls. In the pre...

Annals of allergy, 1981

A 16-year-old male presented with a history of asthma and recurrent pneumonia. A diagnosis of ABP... more A 16-year-old male presented with a history of asthma and recurrent pneumonia. A diagnosis of ABPA was based upon the typical clinical presentation, peripheral eosinophilia, elevated IgE and positive immediate skin tests to Aspergillus. Sputum cultures grew A. terreus, a rare cause of human disease. Soluble and particulate antigens were prepared from this organism. Precipitins against A. terreus, but not against A. fumigatus, were detected in the patient's serum. His lymphocytes proliferated markedly in vitro when exposed to soluble A. terreus but not A. fumigatus antigen. The lymphocyte responses correlated with disease activity. Functional serum opsonic activity was measured using the technique of stimulated polymorphonuclear leucocyte chemiluminescence. The nonspecific opsonic activity of the patient's serum was within high normal range when zymosan was employed as an alternative pathway activator. Specific opsonic activity against particulate Aspergillus antigen was sign...

Infection and Immunity, 1981

The synthesis of the lipopolysaccharide O-specific repeat polymer by Shigella sonnei phase I is a... more The synthesis of the lipopolysaccharide O-specific repeat polymer by Shigella sonnei phase I is a clearly defined bacterial virulence factor necessary for penetrating epithelial cells; S. sonnei phase II does not synthesize this antigen and is uniformly avirulent. The serum opsonic requirements, relative to differences in gross lipopolysaccharide structure, were investigated by quantification and comparison of polymorphonuclear leukocyte (PMNL) metabolism and PMNL-mediated microbicidal action to phase I and phase II organisms, using normal and immune serum. The stimulation of PMNL O2-redox metabolism, as required for oxidative killing, was quantified by a chemiluminescent technique, using luminol as a chemilumigenic substrate. Susceptibility to direct serum or serum PMNL-mediated killing was evaluated by serum and serum-phagocytic killing assays. Stimulation of PMNL metabolism and phagocytic killing of S. sonnei phase I required opsonification by specific phase I antibody plus the c...

Mediators of Inflammation, 1998

Rheumatoid arthritis (RA) is characterized by an abnormal cellular and cytokine infiltration of i... more Rheumatoid arthritis (RA) is characterized by an abnormal cellular and cytokine infiltration of inflamed joints. This study addresses a previously unrecognized interaction between neutrophilic-myeloperoxidase (MPO) and macrophages (MΦ) which could explain the perpetuation of inflammation associated with RA. A monoarticular arthritis was induced in female Lewis rats by injection of streptococcal cell wall extracts (PG-APS). After swelling and erythema subsided, joints were re-injected with one of the following: porcine MPO or partially inactivated MPO (iMPO). Injection with either MPO or iMPO induced a 'flare' of experimental RA. Blocking the MΦ-mannose receptor by mannans, ablated exacerbation of disease. These results indicate that MPO or iMPO can play a pivotal role inthe perpetuation but not initiationof this RA model.

The Journal of Infectious Diseases, 1999

Informed consent was obtained from patients or their parents if children were less than 12 years ... more Informed consent was obtained from patients or their parents if children were less than 12 years old. The study followed French and US Department of Health and Human Services human experimentation guidelines. R.C.A. is the inventor of and has a royalty interest in the patent that covers the CORE/MORE luminescence system but is not otherwise associated with EOE, Inc. (Little Rock, AR). Financial support: Association Française de Lutte contre la Mucoviscidose and the Association pour l'Aide la Recherche contre la Mucoviscidose et l'Assistance aux Malades (V.W.S., B.D.L.

Environmental Health Perspectives, 1994

Immune information in the form of inflammatory mediators directs phagocyte locomotion and increas... more Immune information in the form of inflammatory mediators directs phagocyte locomotion and increases expression of opsonin receptors such that contact with an opsonized microbe results in receptor ligation and activation of microbicidal metabolism. Carbohydrate dehydrogenation and 02 consumption feed reactions that effectively lower the spin quantum number (S) of 02 from 1 to 1/2 and finally to 0. Oxidase-catalyzed univalent reduction of 02 (S = 1; triplet multiplicity) yields hydrodioxylic acid (HO2) and its conjugate base superoxide, 0°(S = 1/2; doublet multiplicity). Acid or enzymatic disproportionation of superoxide yields H202 (S = 0; singlet multiplicity). Haloperoxidase catalyzes H202-dependent oxidation of Clyielding HOCI (S = 0), and reaction of HOCI with H202 yields singlet molecular oxygen, 102 (S = 0; singlet multiplicity). The Wigner spin conservation rule restricts direct reaction of S = 1 02 with S = 0 organic molecules. Lowering the S of 02 overcomes this spin restriction and allows microbicidal combustion. High exergonicity dioxygenation reactions yield electronically excited carbonyl products that relax by photon emission, i.e., phagocyte luminescence. Addition of high quantum yield substrates susceptible to spin allowed dioxygenation, i.e., chemiluminigenic substrates, greatly increases detection sensitivity and defines the nature of the oxygenating agent. Measurement of luminescence allows high sensitivity, real-time, and substrate-specific differential analysis of phagocyte dioxygenating activities. Under assay conditions where immune mediator and opsonin exposure are controlled, luminescence analysis of the initial phase of opsonin-stimulated oxygenation activity allows functional assessment of the opsonin receptor expression per circulating phagocyte and can be used to gauge the in vivo state of immune activation.

Infection and Immunity, 1977

Phagocytically activated polymorphonuclear leukocytes produced a chemiluminescence that could be ... more Phagocytically activated polymorphonuclear leukocytes produced a chemiluminescence that could be correlated metabolically with the stimulated oxidation of glucose via the hexose monophosphate shunt, The chemiluminescence observed was considered to originate from the relaxation of electronically excited carbonyl groups produced during singlet molecular oxygen-mediated microbicidal oxidation of the ingested microbe. With adequate adjustment of leukocyte and bacterial concentrations, the rate of chemiluminescence increase was nearly constant for the first minutes after initiation of phagocytosis. This rate was dependent on the quantity of bacteria phagocytized by the leukocytes. If both leukocytes and bacterial concentrations were held constant, this initial rate of chemiluminescence reflected the opsonic capacity of the sera used for opsonization. The prior absorption of opsonins from serum resulted in a decresed rate of chemiluminescence related to the quantity of bacteria used for a...

Journal of Endotoxin Research

A blood luminescence system (BLS) was employed to analyze blood phagocyte function in response to... more A blood luminescence system (BLS) was employed to analyze blood phagocyte function in response to infusion of endotoxin (4 ng Escherichia coli lipopolysaccharide (LPS)/kg body weight) into 7 healthy human subjects. The subjects were closely monitored clinically, and extensive chemical, hematological and coagulation measurements were taken during the pretreatment, early (symptomatic, 1—8 h post-LPS), and late (asymptomatic, 12—48 h post-LPS) phases of acute inflammation. BLS assessment included measurement of basal and PMA-stimulated phagocyte oxidase and myeloperoxidase (MPO) activities, and also included measurement of circulating (COR) and PAF-primed maximum (MOR) opsonin receptor-dependent phagocytic activities. Basal oxidase activity peaked at T+1 h and showed an additional peak at T+24 h post-LPS. The COR activity also peaked at 1—2 h, but remained elevated through T+24 h post-LPS, while the basal MPO activity peaked only once at T+1 h. We concluded that while MPO evidence of p...

Advances in Experimental Medicine and Biology

Food and Nutrition Sciences, 2013

Laboratory animal science, 1996

The redox metabolism of myeloperoxidase-deficient rooster (chicken) polymorphonuclear leukocytes ... more The redox metabolism of myeloperoxidase-deficient rooster (chicken) polymorphonuclear leukocytes (PMNL) was analyzed by differential chemiluminigenic probes. Chicken complement-opsonified zymosan, a phagocytosable particulate stimulus, and phorbol myristate acetate, a chemical stimulus, were used to activate the PMNL respiratory burst. The two probes used were luminol (5-amino-2,3-dihydro-1,4-phthalazinedione), a general probe of oxidase-peroxidase activities, and lucigenin (dimethylbiacridinium binitrate), a selective probe of oxidase activity. Rooster PMNLs yielded dimethylbiacridinum binitrate-dependent chemiluminescence (CL) comparable to those of myeloperoxidase-containing human PMNLs after stimulation with opsonified zymosan and to a lesser extent with phorbol myristate acetate. However, the luminol-dependent CL of opsonified zymosan or phorbol myristate acetate-stimulated rooster PMNLs were approximately two orders of magnitude lower than responses observed with human PMNLs. ...