A Bispecific Monoclonal Antibody Targeting Psl and PcrV Enhances Neutrophil-Mediated Killing of Pseudomonas aeruginosa in Patients with Bronchiectasis

RATIONALE AND OBJECTIVES

Pseudomonas aeruginosa infection is associated with worse outcomes in bronchiectasis. Impaired neutrophil antimicrobial responses contribute to bacterial persistence. Gremubamab is a bivalent, bispecific monoclonal antibody targeting Psl exopolysaccharide and the type 3 secretion system component PcrV. This study evaluated the efficacy of gremubamab to enhance killing of P.aeruginosa by neutrophils from bronchiectasis patients and to prevent P.aeruginosa-associated cytotoxicity.

METHODS

P.aeruginosa isolates from a global bronchiectasis cohort (n=100) underwent whole-genome sequencing to determine target prevalence. Functional activity of gremubamab against selected isolates was tested in-vitro and in-vivo. Patients with bronchiectasis (n=11) and controls (n=10) were enrolled and the effect of gremubamab in peripheral-blood neutrophil opsonophagocytic killing (OPK) assays against P.aeruginosa was evaluated. Serum antibody titers to Psl and PcrV were determined (n=30; 19: chronic P.aeruginosa infection, 11: no-known P.aeruginosa infection), as was the effect of gremubamab treatment in OPK and anti-cytotoxic activity assays.

MEASUREMENTS AND RESULTS

Psl and PcrV were conserved in isolates from chronically-infected bronchiectasis patients. 73/100 isolates had a full psl locus and 99/100 contained the pcrV gene, with 20 distinct full-length PcrV protein subtypes identified. PcrV subtypes were successfully bound by gremubamab and the mAb mediated potent protective activity against tested isolates. Gremubamab increased bronchiectasis patient neutrophil-mediated OPK (+34.6±8.1%) and phagocytosis (+70.0±48.8%), similar to effects observed in neutrophils from controls (OPK:+30.1±7.6%). No evidence of competition between gremubamab and endogenous antibodies was found, with protection against P.aeruginosa-induced cytotoxicity and enhanced OPK demonstrated with and without addition of patient serum.

CONCLUSION

Gremubamab enhanced bronchiectasis patient neutrophil phagocytosis and killing of P.aeruginosa and reduced virulence.

Increased innate immune activation induces protective RSV-specific lung-resident memory T cells in neonatal mice

Young infants frequently experience respiratory tract infections, yet vaccines designed to provide mucosal protection are lacking. Localizing pathogen-specific cellular and humoral immune responses to the lung could provide improved immune protection. We used a well-characterized murine model of respiratory syncytial virus (RSV) to study the development of lung-resident memory T cells (TRM) in neonatal compared to adult mice. We demonstrated that priming with RSV during the neonatal period failed to retain RSV-specific clusters of differentiation (CD8) TRM 6 weeks post infection, in contrast to priming during adulthood. The reduced development of RSV-specific TRM was associated with poor acquisition of two key markers of tissue residence: CD69 and CD103. However, by augmenting both innate immune activation and antigen exposure, neonatal RSV-specific CD8 T cells increased expression of tissue-residence markers and were maintained in the lung at memory time points. Establishment of TRM correlated with more rapid control of the virus in the lungs upon reinfection. This is the first strategy to effectively establish RSV-specific TRM in neonates providing new insight into neonatal memory T cell development and vaccine strategies.

Evaluation of community readiness for change prior to a participatory physical activity intervention in Germany

A lack of communities' readiness for change is reported as a major barrier toward an effective implementation of health promoting interventions in community settings. Adding an alternative readiness assessment approach to existing research practice, this study aimed to investigate how a selected community could be evaluated in-depth regarding its readiness for change based on multiple key informant perspectives, with the intention of using this knowledge for the preparation of improved local physical activity (PA) interventions for men above 50 years of age. We conducted semi-structured face-to-face key informant interviews with stakeholders and relevant persons from a local German community (N = 15). The interview guide was based on a comprehensive summary of community readiness dimensions. After verbatim transcription, we conducted thematic analysis to synthesize the complex results regarding community readiness related to PA. The data supported that the community disposed of a variety of resources regarding PA and showed signs of readiness for change. However, a certain degree of saturation regarding PA programs existed. The need for health enhancing PA interventions for men was only partly recognized. The local authority considered PA to be particularly important in the context of mobility and traffic safety. Including multiple stakeholders contributed to a balanced and in-depth assessment of community readiness and was helpful for determining starting points for tailored PA interventions due to the detection of complex relationships and structures. The study delivers preliminary evidence that a qualitative multi-perspective community readiness assessment adds value to quantified single-perspective readiness assessment research practice.

First modern human settlement recorded in the Iberian hinterland occurred during Heinrich Stadial 2 within harsh environmental conditions

As the south-westernmost region of Europe, the Iberian Peninsula stands as a key area for understanding the process of modern human dispersal into Eurasia. However, the precise timing, ecological setting and cultural context of this process remains controversial concerning its spatiotemporal distribution within the different regions of the peninsula. While traditional models assumed that the whole Iberian hinterland was avoided by modern humans due to ecological factors until the retreat of the Last Glacial Maximum, recent research has demonstrated that hunter-gatherers entered the Iberian interior at least during Solutrean times. We provide a multi-proxy geoarchaeological, chronometric and paleoecological study on human–environment interactions based on the key site of Peña Capón (Guadalajara, Spain). Results show (1) that this site hosts the oldest modern human presence recorded to date in central Iberia, associated to pre-Solutrean cultural traditions around 26,000 years ago, and (2) that this presence occurred during Heinrich Stadial 2 within harsh environmental conditions. These findings demonstrate that this area of the Iberian hinterland was recurrently occupied regardless of climate and environmental variability, thus challenging the widely accepted hypothesis that ecological risk hampered the human settlement of the Iberian interior highlands since the first arrival of modern humans to Southwest Europe.

Local Respiratory Viral Surveillance Can Focus Public Health Interventions to Decrease Influenza Disease Burden

BACKGROUND

Respiratory viruses are an important cause of nonbattle injury disease and contribute to the top seven reasons for medical encounters. In the absence of vaccines that provide complete protection against these viruses, viral surveillance can identify disease burden and target virus-specific preventative measures. Influenza infection, in particular, has significant adverse effects on force readiness.

METHODS

We tracked the frequency of 16 respiratory viruses at Walter Reed National Military Medical Center tested for during routine patient care using multiplex polymerase chain reaction and rapid antigen testing. We collected data on the date and location of the testing, as well as the age of the individual tested from two consecutive respiratory viral seasons.

RESULTS

During the first year of data compilation (2017-2018), 2556 tests were performed; 342 (13.4%) were positive for influenza A and 119 (4.7%) were positive for influenza B. After influenza, the most common families of viruses identified were rhino/enterovirus (490 [19.2%]). During the second year (2018-2019), 4,458 tests were run; 564 (12.7%) were positive for influenza A and 35 (0.79%) were positive for influenza B, while rhino/enterovirus was identified in 690 (15.4%). Influenza peaked early during the 2017-2018 season and later during the 2018-2019 season. Importantly, during the 2017-2018 season, the vaccine was less effective for the H3N2 strain circulating that year and viral surveillance quickly identified a hospital-specific outbreak and a larger disease burden. This was in contrast to the 2018-2019 vaccine which exhibited higher effectiveness for circulating strains.

CONCLUSION

Our data highlight the seasonality of respiratory viruses with a focus on influenza. By tracking respiratory viruses in Department of Defense communities, we may be able to predict when influenza may cause the greatest burden for distinct organizational regions and prescribe with greater precision preventative protocols by location, as well as rapidly determine vaccine efficacy. Our current data suggest that when vaccine strains are mismatched, rapid upfront targeting of antivirals may be warranted, but when the vaccine strains are better matched, late season peaks of disease may indicate waning immunity and should be monitored.

Fibrinogen Haifa: Fibrinogen Variant with Absence of Protective Effect of Calcium on Plasmin Degradation of Gamma Chains

The abnormal fibrinogen Haifa is characterized by the fact that calcium present during enzymatic digestion by plasmin does not protect the Haifa D gamma chain against further plasmin attack as it does in normal molecules.

Since calcium binding to fibrinogen, ADP - platelet aggregation cofactor activity and gamma dimerization process induced by factor XIIIa are normal for fibrinogen Haifa, the corresponding sequences in the gamma chain are not involved. It seems rather that the anomaly resides near the gamma 302 plasmin cleavage site that is protected when calcium is bound to the gamma chain and that this affects the availability of the polymerization site located in the C terminal part of the chain.

Distinct innate signaling and activation of dendritic cells during the neonatal period determines their functional response to respiratory syncytial virus infection

Dendritic cells (DCs) are among the first to respond to infection, providing the critical link between innate and adaptive immunity. Neonates often have weak innate immune responses that can limit adaptive immunity and contribute to increased susceptibility and more severe infection with intracellular pathogens, such as respiratory syncytial virus (RSV). We have previously shown differential migration and defective activation of neonatal murine respiratory CD103+ DCs, which is associated with diminished RSV-specific CD8 T cell responses in neonatal mice. In order to define the age-dependent regulation of respiratory DC function, we have developed a neonatal mouse model of RSV to track antigen presentation via infection with an ovalbumin-expressing RSV and an antibody against H2kb-OVA257–264. We found adequate transfer of RSV-derived OVA257–264 by neonatal CD103+ DCs to the dLN, suggesting poor CD8 T cell responses are not due to limited antigen presentation. However, neonatal CD103+ DCs expressing H2kb-OVA257–264 failed to upregulate CD80/86, which is critical to T cell stimulation. RNA-seq analysis of H2kb-OVA257–264+ CD103+ DCs implicated defective type I IFN signaling in neonates that may influence reduced activation. In support of this, while we find type I IFN to be diminished in the neonatal lung, treatment of neonates with IFN-α failed to restore the activation of neonatal H2kb-OVA257–264+ CD103+DCs.

Our data demonstrate a distinct developmental regulation of innate immunity in early life and identify type I IFN signaling as contributing to defective DC activation during RSV infection in neonates. Defining age-dependent mechanisms controlling immunity may lead to intelligently designed vaccines for this age group.

Differential antigen presentation and transport by neonatal and adult dendritic cell subsets during Respiratory Syncytial Virus (RSV) infection

Dendritic cells (DCs) are critical for the induction of anti-viral CD8+ T cells. Young infants mount poor antiviral responses contributing to increased disease susceptibility and severity compared with acquisition later in life. Using a mouse model of respiratory syncytial virus (RSV), we have previously shown differences in the number of DCs that can carry antigen from the lung to the lung-draining lymph node (dLN) during infection between adults and neonates, and this is associated with age-dependent differences in RSV-specific CD8+ T cell responses. However whether adult or neonatal DCs more readily present antigen for T cell engagement is unknown.

In this study, we used an ovalbumin-expressing RSV (RSV-OVA) to track antigen presentation through early infection. In the lung, expression of MHCI-bound OVA (MHCI-OVA) was highest on adult CD103+ DCs; while in the dLN a greater number of neonatal CD103+ DCs expressed MHCI-OVA. Quantification of the migration-associated chemokine receptor 7 identified increased expression on neonatal MHCI-OVA-expressing CD103+ DCs compared to adults, suggesting adults may more readily present antigen but neonatal CD103+ DCs were more apt to migrate upon antigen acquisition. However, neonates failed to induce an OVA-specific T cell response in the lung in contrast to adults.

Together our data indicate that in neonates MHCI-OVA+ CD103+ DCs were more proficient at migration resulting in a greater number of MHCI-OVA-presenting CD103+ DCs in the dLN;- however, they failed to induce an OVA-specific T cell response. Thus antigen abundance was not the primary determinant of CD8+ T cell induction during RSV infection in neonates, suggesting that alternate mechanism(s) limit their DC-mediated T cell responses.

Increased membrane cholesterol in lymphocytes diverts T-cells toward an inflammatory response

Cell signaling for T-cell growth, differentiation, and apoptosis is initiated in the cholesterol-rich microdomains of the plasma membrane known as lipid rafts. Herein, we investigated whether enrichment of membrane cholesterol in lipid rafts affects antigen-specific CD4 T-helper cell functions. Enrichment of membrane cholesterol by 40–50% following squalene administration in mice was paralleled by an increased number of resting CD4 T helper cells in periphery. We also observed sensitization of the Th1 differentiation machinery through co-localization of IL-2Rα, IL-4Rα, and IL-12Rβ2 subunits with GM1 positive lipid rafts, and increased STAT-4 and STAT-5 phosphorylation following membrane cholesterol enrichment. Antigen stimulation or CD3/CD28 polyclonal stimulation of membrane cholesterol-enriched, resting CD4 T-cells followed a path of Th1 differentiation, which was more vigorous in the presence of increased IL-12 secretion by APCs enriched in membrane cholesterol. Enrichment of membrane cholesterol in antigen-specific, autoimmune Th1 cells fostered their organ-specific reactivity, as confirmed in an autoimmune mouse model for diabetes. However, membrane cholesterol enrichment in CD4⁺Foxp3⁺ T-reg cells did not alter their suppressogenic function. These findings revealed a differential regulatory effect of membrane cholesterol on the function of CD4 T-cell subsets. This first suggests that membrane cholesterol could be a new therapeutic target to modulate the immune functions, and second that increased membrane cholesterol in various physiopathological conditions may bias the immune system toward an inflammatory Th1 type response.

Double negative (CD3+ 4- 8-) TCR alphabeta splenic cells from young NOD mice provide long-lasting protection against type 1 diabetes

BACKGROUND

Double negative CD3(+)4(-)8(-) TCR alphabeta splenic cells (DNCD3) can suppress the immune responses to allo and xenografts, infectious agents, tumors, and some autoimmune disorders. However, little is known about their role in autoimmune diabetes, a disease characterized by the reduction of insulin production subsequent to destruction of pancreatic beta-cells by a polyclonal population of self-reactive T-cells. Herein, we analyzed the function and phenotype of DNCD3 splenic cells in young NOD mice predisposed to several autoimmune disorders among which, the human-like autoimmune diabetes.

METHODOLOGY/PRINCIPAL FINDINGS

DNCD3 splenic cells from young NOD mice (1) provided long-lasting protection against diabetes transfer in NOD/Scid immunodeficient mice, (2) proliferated and differentiated in the spleen and pancreas of NOD/Scid mice and pre-diabetic NOD mice into IL-10-secreting T(R)-1 like cells in a Th2-like environment, and (3) their anti-diabetogenic phenotype is CD3(+)(CD4(-)CD8(-))CD28(+)CD69(+)CD25(low) Foxp3(-) iCTLA-4(-)TCR alphabeta(+) with a predominant Vbeta13 gene usage.

CONCLUSIONS/SIGNIFICANCE

These findings delineate a new T regulatory component in autoimmune diabetes apart from that of NKT and CD4(+)CD25(high) Foxp3(+)T-regulatory cells. DNCD3 splenic cells could be potentially manipulated towards the development of autologous cell therapies in autoimmune diabetes.

Genotoxicity of 10 cigarette smoke condensates in four test systems: comparisons between assays and condensates

The particulate fraction of cigarette smoke, cigarette smoke condensate (CSC), is genotoxic in many short-term in vitro tests and is carcinogenic in rodents. However, no study has evaluated a series of CSCs prepared from a diverse set of cigarettes and produced with different smoking machine regimens in several short-term genotoxicity tests. Here we report on the genotoxicity of 10 CSCs prepared from commercial cigarettes that ranged from ultra-low tar per cigarette (< or =6.5 mg) to full flavor (>14.5 mg) as determined by the Federal Trade Commission (FTC) smoking regimen, a reference cigarette blended to be representative of a U.S. FTC-regimen low-tar cigarette, and experimental cigarettes constructed of single tobacco types. CSCs were tested in the presence of rat liver S9 in the Salmonella plate-incorporation assay using frameshift strains TA98 and YG1041; in micronucleus and comet assays in L5178Y/Tk(+/-) 7.3.2C mouse lymphoma cells, and in CHO-K(1) cells for chromosome aberrations. All 10 CSCs were mutagenic in both strains of Salmonella, and the rank order of their mutagenic potencies was similar. Their mutagenic potencies in Salmonella spanned 7-fold when expressed as rev/mug CSC but 158-fold when expressed as rev/mg nicotine; the range of genotoxic potencies of the CSCs in the other assays was similar regardless of how the data were expressed. All 10 CSCs induced micronuclei with a 3-fold range in their potency. All but one CSC induced DNA damage over a 20-fold range, and all but one CSC induced chromosome aberrations over a 4-fold range. There was no relation among the genotoxic potencies of the CSCs across the assays, and a qualitative advantage of the addition of the other assays to the Salmonella assay was not supported by our findings. Although consideration of nicotine levels may improve the relevance of the quantitative data obtained in the Salmonella and possibly comet assays, compensatory smoking habits and other factors may make the data from the assays used here have qualitative but not quantitative value in assessing risk of cigarette types and cigarette smoking to human health.

In Vivo and in Vitro Evidence for Extracellular Caspase Activity Released from Apoptotic Cells

While caspases play an established role as intracellular executors of apoptosis, little is known about extracellular activities of this ubiquitously expressed family of proteases. We demonstrate here that recombinant caspase-3 retained enzymatic activity in various extracellular fluids. Experiments with cell lines, primary cells, and mice with fulminant CD95-triggered hepatitis showed that significant amounts of DEVD-aminofluoromethylcoumarine-cleaving activity, indicative of active effector caspases, were released into the medium/plasma during apoptosis. Furthermore, caspase activities were detected in liquor samples from human head trauma patients. These findings warrant closer investigation of DEVDase activity as a diagnostic marker, and of potential extracellular substrates for caspases.

Proteasomes from Dictyostelium discoideum: characterization of structure and function

We have isolated and purified 20 S proteasomes from Dictyostelium discoideum and characterized their proteolytic activities. Two-dimensional electrophoresis revealed 13 distinct spots. Affinity purification with a subunit-specific monoclonal antibody indicated that the preparation was homogeneous, i.e., each individual proteasome appeared to have the full set of subunits. We have not obtained any evidence for changes in subunit composition at different developmental stages. The cDNA clones coding for two subunits (4 and 5), both of the alpha-type, have been cloned and sequenced. It has been shown by immunoelectron microscopy that each proteasome is composed of two identical halves, related to each other by C2 symmetry. The resulting model implies that the alpha- and beta-subunits have a fixed pattern of relationships. D. discoideum proteasomes are found both in the cytosol and, in higher concentrations, in the nucleus.

Topology of the anion-selective porin Omp32 from Comamonas acidovorans

Limited proteolysis experiments were performed with outer membranes from Comamonas acidovorans to probe the topology of its major protein component, the anion-selective porin Omp32. Proteinase K treatment above a critical temperature of 42 degrees C cleaved the surface-exposed regions of the porin, yielding membrane-embedded fragments which were separated by SDS polyacrylamide gel electrophoresis or reversed phase chromatography. The identification of the proteinase K-sensitive sites was performed by microsequencing. This allowed us to determine six surface-exposed sites of the porin, all located in nonconserved primary structure regions. These results along with the previously determined amino acid sequence and in conjunction with some structural constraints applicable to porins allowed us to propose a chain-folding model of the Omp32 porin. The features of our model are compared with the structure of the Rhodobacter capsulatus porin, recently established by X-ray crystallography (Weiss et al., 1991) and they are used to elucidate the structural basis of the anion selectivity.

Analysis of cerebrospinal fluid from patients with psychiatric and neurological disorders by two-dimensional electrophoresis: identification of disease-associated polypeptides as fibrin fragments

Two-dimensional electrophoresis (2-DE) of cerebrospinal fluid (CSF) samples--from 347 patients with various psychiatric and neurological disorders--and subsequent silver staining revealed two additional polypeptides (Mr 40,000) in 49% of 111 schizophrenics, 46% of 43 schizoaffective patients, 36% of 41 patients with affective disorders, 43% of 28 patients with multiple sclerosis, but not in 25 patients without neurological symptomatology, nor in 9 patients with Lues, and in only 2 of 25 patients with AIDS. The two polypeptides, as detected by 2-DE, eluted after size exclusion chromatography in fractions containing proteins with Mr greater than 200,000. After 2-DE of CSF samples, enriched by gel chromatography, the polypeptides were immobilized by blotting onto glass-fiber membranes and subjected to N-terminal sequencing. Polypeptide A was identified as beta-chain remnant (beta 2), derived from plasmin cleavage of fibrin(ogen). After size exclusion chromatography, 2-DE, and Western blotting, polypeptide A and B, as well as several other spots, reacted with fibrinogen antibodies, suggesting that the polypeptides are subunits of a fibrin degradation complex.

Fibrinogen Stony Brook, a heterozygous A alpha 16Arg----Cys dysfibrinogenemia. Evaluation of diminished platelet aggregation support and of enhanced inhibition of fibrin assembly

Assessed by high performance liquid chromatographic and amino acid sequence determinations, approximately one half (n = 4) of A peptide in fibrinogen Stony Brook (phi SB) contained the A alpha 16Arg----Cys substitution. To examine its functional behavior, mutant molecule-rich soluble subfractions that partly or fully lacked their normal A peptide were obtained from cryoprecipitates or from incoagulable material, respectively. Such subfractions consistently induced a more pronounced decrease (n = 3) in the turbidity of normal polymerizing fibrin than that induced by normal fibrinogen, by whole phi SB (n = 4) or by fibrinogen from an unrelated homozygous proband. These subfractions also exhibited decreased (12-50% of normal controls, fibrinogen 30-590 nM, n = 5) ADP-induced aggregation support of gel-sieved platelets, a decrease not demonstrable by whole phi SB, by fibrinogen from the homozygous proband, or by enrichment of the latter with normal soluble fibrin. A single isolate displaying diminished platelet aggregation support was 125I-labeled and examined further. It exhibited decreased binding to platelets, and Scatchard analysis indicated decreased binding affinity but normal maximum binding. We infer that phi SB contained heterodimers that exhibited these distinct functional properties when their normal A peptide had been cleaved.

The complete primary structure of the human snRNP E protein

The snRNP E protein is one of four "core" proteins associated with the snRNAs of the U family (U1,U2,U4,U5, and U6). Screening of a human teratoma cDNA library with a partial cDNA for a human autoimmune antigen resulted in the isolation of a cDNA clone containing the entire coding region of this snRNP core protein. Comparison of the 5' end of this cDNA with the sequences of two processed pseudogenes and primer extension data suggest that the cDNA is nearly full length. The longest open reading frame in this clone codes for a basic 92 amino acid protein which is in perfect agreement with amino acid sequence data obtained from purified E protein. The predicted sequence of this protein reveals no extensive similarity to other snRNP proteins, but contains regions of similarity to a eukaryotic ribosomal protein.

Fibrinogen Haifa: fibrinogen variant with absence of protective effect of calcium on plasmin degradation of gamma chains

The abnormal fibrinogen Haifa is characterized by the fact that calcium present during enzymatic digestion by plasmin does not protect the Haifa D gamma chain against further plasmin attack as it does in normal molecules. Since calcium binding to fibrinogen, ADP--platelet aggregation cofactor activity and gamma dimerization process induced by factor XIIIa are normal for fibrinogen Haifa, the corresponding sequences in the gamma chain are not involved. It seems rather that the anomaly resides near the gamma 302 plasmin cleavage site that is protected when calcium is bound to the gamma chain and that this affects the availability of the polymerization site located in the C terminal part of the chain.

Characterization of fibrinogen Milano I: amino acid exchange gamma 330 Asp----Val impairs fibrin polymerization

An abnormal fibrinogen was found in two asymptomatic members (father and daughter) of the same family, originating from northern Italy. Routine coagulation studies revealed prolonged thrombin and reptilase clotting times. Plasma fibrinogen levels, as determined by a functional assay, were markedly diminished, whereas the heat precipitation method indicated normal fibrinogen values. On the basis of these findings, a tentative diagnosis of dysfibrinogenemia was made, and according to the accepted nomenclature, this fibrinogen variant was called "fibrinogen Milano l." The time course of fibrinopeptide A and B release from fibrinogen Milano l was normal, but the aggregation of fibrin monomers was delayed. Two-dimensional electrophoresis of reduced variant fibrinogen chains showed a defective gamma-chain with increased cathodic mobility. An abnormal electrophoretic mobility was observed also for the gamma-chain remnants of fibrinogen fragments D1 and D2 derived from fibrinogen Milano l, whereas the charge anomaly was lost after a further digestion by plasmin to D3, suggesting that the structure abnormality of this variant is situated in the region gamma 303-356. An abnormal peptide was isolated after cyanogen bromide cleavage of intact fibrinogen Milano l. This fragment spans from position gamma 311 to gamma 336. Amino acid analysis of the abnormal peptide showed the presence of valine and a diminished content of aspartic acid. Sequence analysis demonstrated an amino acid exchange Asp----Val in the gamma-chain at position 330.

Novel structure elucidation strategy for genetically abnormal fibrinogens with incomplete fibrinopeptide release as applied to fibrinogen Schwarzach

A novel and simple strategy was developed for the structure elucidation of those genetically abnormal fibrinogens in which thrombin is unable to release fibrinopeptide A from the abnormal molecules. The method provides evidence for the Arg leads to Cys exchange at the C-terminus of the fibrinopeptide A sequence. The abnormal fibrinogen was mercaptolysed and then S-amino-ethylated. Upon thrombin digestion, the modified fibrinogen released new peptides, as shown by high-performance liquid chromatography. The amino-acid analysis proved that these peptides correspond to the expected fibrinopeptide A variants. It was therefore concluded that the analysed case of dysfibrinogenemia, designated Fibrinogen Schwarzach, contains an A alpha 16 Arg leads to Cys exchange in the heterozygous form.

Fibrinogen Manchester: identification of an abnormal fibrinopeptide A with a C-terminal arginine leads to histidine substitution

Purified samples of fibrinogen Manchester, a congenital dysfibrinogenaemia with impaired fibrinopeptide A (FPA) release, were digested with thrombin. Amino acid sequencing of the fibrin showed that FPA had been completely released. High performance liquid chromatographic (HPLC) analysis of the clot supernatant showed the presence of a new peptide eluting ahead of the normal FPA. The amino acid composition and sequence of the new peptide established its identity as a variant of FPA containing histidine in position 16 instead of the usual arginine. The chromatograms from both siblings with the defect demonstrated that they were heterozygous for this clotting defect.

Delayed release of an abnormal fibrinopeptide A from fibrinogen Manchester: effect of the A alpha 16 Arg leads to His substitution upon fibrin monomer polymerization and the immunological crossreactivity of the peptide

Fibrinogen Manchester is an abnormal fibrinogen with an impaired release of fibrinopeptide A (FPA) and a polymerization abnormality. In the accompanying article we have identified the amino acid substitution in fibrinogen Manchester as A alpha 16 Arg leads to His. When fibrinogen Manchester was digested with low thrombin concentrations approximately 40-50% of the total FPA content was release at a rate similar to FPA release from normal fibrinogen. The fibrin so formed exhibited an impaired polymerization of monomers. Digestion of fibrinogen Manchester with high concentrations of thrombin for prolonged times released the remaining FPA which had an abnormal retention time when studied by high performance liquid chromatography (HPLC). This fibrinopeptide has been shown previously to contain the A alpha 16 Arg leads to His substitution. fibrin resulting from this exhaustive digestion had normal polymerization of monomers. The normal and substituted FPAs were isolated by HPLC and compared in a double antibody competitive-binding assay for normal FPA. The immunological cross-reactivity of the abnormal peptide was reduced, so that approximately 5 times more abnormal peptide was required on a molar basis to displace labelled normal FPA. Normal intact fibrinogen was 10-fold less reactive (on a half molar basis) than free normal FPA and the crossreactivity of fibrinogen Manchester was measurably less than that of normal fibrinogen. It is concluded that immunological measurement alone of FPA released from abnormal fibrinogens may not give a complete description of the kinetics of peptide release if the amino acid substitution lies within the FPA sequence. The combination of radioimmunoassay and HPLC, however, provides a powerful analytical approach that should be useful in classifying and characterizing abnormal fibrinogens.

Analysis of human fibrinopeptides by high-performance liquid chromatography

During coagulation, fibrinogen is cleaved by thrombin, whereby fibrin and low molecular mass peptides, the so-called fibrinopeptides, are released. A novel method, employing high-performance liquid chromatography, has been developed for the separation and quantitation of these peptides. For the chromatography a reversed phase column was used. The fibrinopeptides were detected by their UV-absorption at 210 nm, peptides released from 0.1 mg of fibrinogen being easily detected. The procedure offers for the first time the possibility of determining all human fibrinopeptides and their degradation products in a single analysis. It is eminently suited for fibrinopeptide preparation and studies of fibrinopeptide release kinetics and genetically abnormal fibrinopeptides.

Studies on the mechanism of hepatic microsomal N-oxide formation. The role of cytochrome P-450 and mixed-function amine oxidase in the N-oxidation of NN-dimethylaniline

Evidence is established for the existence of alternative metabolic routes of N-oxidation of NN-dimethylaniline in rabbit liver microsomal fraction. One pathway involves the participation of two types of cytochrome P-450 with different sensitivities towards heat. Both types may represent distinct haemoprotein species or two physical forms of a single pigment. The other pathway is represented by the mixed-function amine oxidase. The enzyme lacks NADPH dehydrogenase activity and is insensitive to treatment with 2-bromo-4'-nitroacetophenone and steapsin: it catalyses N-oxidation of imipramine, trimethylamine and NN-dimethylaniline in molar proportions considerably different from those of the cytochrome P-450-supported reactions. Cytochrome P-450 is estimated to account for the formation of at least 50-60% of the total NN-dimethylaniline N-oxide formed in the intact rabbit liver microsomal fraction, the remainder arising from the action of the mixed-function amine oxidase.

Comparative studies on the N-oxidation of aniline and N,N-dimethylaniline by rabbit liver microsomes

1. Rate studies of N-oxidation of aniline and N,N-dimethylaniline by rabbit liver microsomal preparations were performed at different pH values. The apparent pKs of the free functional groups were 7-2 and 6-9, respectively, at 26 degrees. The apparent heats of ionization of these groups varied from 26-8 to 31-8 kJ mol-1. 2. Photo-oxidation of the microsomal mixed function oxidase resulted in rapid loss of N-oxygenating activity. The enzyme was markedly protected from inactivation by the presence of aniline or N,N-dimethylaniline. The apparent KD values for protection were close to the Km and KS values for the individual arylamines. The pH profiles of the initial rates of photo-inactivation resembled the titration curves of groups with an apparent pKa between 6-0 and 6-2. 3. The N-oxidase was strongly inhibited by diethyl pyrocarbonate at pH 6-2. 3. The N-oxidase was strongly inhibited by diethyl pyrocarbonate at pH 6-0. Catalytic capacity was partially restored by treatment with neutral hydroxylamine. Pyridine protected the enzyme from acylation. 4. A close relationship exists between the N-hydroxylation of aniline and the N-oxide formation from N,N-dimethylaniline with respect to sensitivity to photo-oxidation, reactivity to protective substrates and susceptibility to carbethoxylation.