NIST Interlaboratory Study on Glycosylation Analysis of Monoclonal Antibodies: Comparison of Results from Diverse Analytical Methods

Glycosylation is a topic of intense current interest in the development of biopharmaceuticals because it is related to drug safety and efficacy. This work describes results of an interlaboratory study on the glycosylation of the Primary Sample (PS) of NISTmAb, a monoclonal antibody reference material. Seventy-six laboratories from industry, university, research, government, and hospital sectors in Europe, North America, Asia, and Australia submitted a total of 103 reports on glycan distributions. The principal objective of this study was to report and compare results for the full range of analytical methods presently used in the glycosylation analysis of mAbs. Therefore, participation was unrestricted, with laboratories choosing their own measurement techniques. Protein glycosylation was determined in various ways, including at the level of intact mAb, protein fragments, glycopeptides, or released glycans, using a wide variety of methods for derivatization, separation, identification, and quantification. Consequently, the diversity of results was enormous, with the number of glycan compositions identified by each laboratory ranging from 4 to 48. In total, one hundred sixteen glycan compositions were reported, of which 57 compositions could be assigned consensus abundance values. These consensus medians provide community-derived values for NISTmAb PS. Agreement with the consensus medians did not depend on the specific method or laboratory type. The study provides a view of the current state-of-the-art for biologic glycosylation measurement and suggests a clear need for harmonization of glycosylation analysis methods.

Topological N-glycosylation and site-specific N-glycan sulfation of influenza proteins in the highly expressed H1N1 candidate vaccines

The outbreak of a pandemic influenza H1N1 in 2009 required the rapid generation of high-yielding vaccines against the A/California/7/2009 virus, which were achieved by either addition or deletion of a glycosylation site in the influenza proteins hemagglutinin and neuraminidase. In this report, we have systematically evaluated the glycan composition, structural distribution and topology of glycosylation for two high-yield candidate reassortant vaccines (NIBRG-121xp and NYMC-X181A) by combining various enzymatic digestions with high performance liquid chromatography and multiple-stage mass spectrometry. Proteomic data analyses of the full-length protein sequences determined 9 N-glycosylation sites of hemagglutinin, and defined 6 N-glycosylation sites and the glycan structures of low abundance neuraminidase, which were occupied by high-mannose, hybrid and complex-type N-glycans. A total of ~300 glycopeptides were analyzed and manually validated by tandem mass spectrometry. The specific N-glycan structure and topological location of these N-glycans are highly correlated to the spatial protein structure and the residential ligand binding. Interestingly, sulfation, fucosylation and bisecting N-acetylglucosamine of N-glycans were also reliably identified at the specific glycosylation sites of the two influenza proteins that may serve a crucial role in regulating the protein structure and increasing the protein abundance of the influenza virus reassortants.

Cellular immune responses of older adults to four influenza vaccines: Results of a randomized, controlled comparison

Cellular immunity is important for protection against the serious complications of influenza in older adults. As it is unclear if newer influenza vaccines elicit greater cellular responses than standard vaccines, we compared responses to 2 standard and 2 newer licensed trivalent inactivated vaccines (TIVs) in a randomized trial in older adults. Non-frail adults ≥ 65 y old were randomly assigned to receive standard subunit, MF59-adjuvanted subunit, standard split-virus or intradermal split-virus TIV. Peripheral blood mononuclear cells (PBMC) harvested pre- and 3-weeks post-vaccination were stimulated with live A/H3N2 virus. PBMC supernatants were tested for interleukin 10 (IL-10) and interferon gamma (IFN-γ), and lysates for granzyme B (GrB). Flow cytometry identified CD4⁺ and CD8⁺ T- cells expressing intracellular IL-2, IL-10, IFN-γ, GrB, or perforin. Differences following immunization were assessed for paired subject samples and among vaccines. 120 seniors participated, 29-31 per group, which were well matched demographically. Virus-stimulated PBMCs were GrB-rich before and after vaccination, with minimal increases evident. Immunization did not increase secretion of IFN-γ or IL-10. However, cytolytic effector T-cells (CD8⁺GrB⁺perforin⁺) increased significantly in percentage post-vaccination in all groups, to similar mean values across groups. CD4⁺GrB⁺perforin⁺ T-cells also increased significantly after each vaccine, to similar mean values among vaccines. Vaccination did not increase the low baseline percentages of CD4⁺ or CD8⁺ T-cells expressing IFN-γ, IL-2 or IL-10 . In conclusion, participants had pre-existing cellular immunity to H3N2 virus. All 4 vaccines boosted cellular responses to a similar but limited extent, particularly cytolytic effector CD8⁺ T-cells associated with clinical protection against influenza.

Data generated from three quantitative mass spectral methods for the analysis of trivalent influenza vaccine antigens are compared

Herein we present the data necessary for generation of alternative means to produce equimolar mixtures of peptides (“Design and Expression of a QconCAT Protein to Validate Hi3 Protein Quantification of Influenza Vaccine Antigens” (D.G.S. Smith, G. Gingras, Y. Aubin, T.D. Cyr, 2016) [1]), such as QConCAT (“Trends in QconCATs for targeted proteomics” (J. Chen, I.V. Turko, 2014) [2] , “Natural flanking sequences for peptides included in a quantification concatamer internal standard” (C.S. Cheung, K.W. Anderson, M. Wang, I.V. Turko, 2015) [3]) and SpikeTides versus the label free Hi3 approach. The experimental design and the interpretation of results are discussed in the original article [1].

Design and expression of a QconCAT protein to validate Hi3 protein quantification of influenza vaccine antigens

Quantification of the antigens hemagglutinin and neuraminidase in influenza vaccines has been reported using an antibody-free liquid chromatography-mass spectrometry (LC-MS) based method known as MS(E) "Hi3". This approach is based on the average signal intensity of the three most intense tryptic peptides relative to a primary standard. This strategy assumes that the Hi3 signal responses are consistent for all proteins, and therefore comparable to a spiked reference for absolute quantification. This method is much faster than the current standard methods; however, the results can vary significantly which brought the method's accuracy into question. To address this question we generated synthetic proteins comprising a concatenation of the peptides used to quantify the proteins of interest (QconCAT). Complete tryptic digestion of a QconCAT protein produces equal molar peptide amounts, allowing verification of equal signal response of Hi3 peptides for the proteins of interest. The generation of an intact, stable, QconCAT protein that digest completely is challenging. We have designed and analyzed five QconCAT proteins with unique design elements to address these challenges. We conclude that a suitable QconCAT protein can be produced and that the results obtained reinforce the validity of the Hi3 approach for quantifying proteins in annual influenza vaccine formulations.

SIGNIFICANCE

The advances in quantitative proteomics have allowed the adaptation and application of these methods to numerous fields. In this paper we have validated a Hi3 approach to augment the antigen quantification for influenza vaccines injected into many millions annually. This methodology allows analysis of multiple antigens simultaneously without the need to generate antibodies. Key circumstances where this is advantageous are for quantitation of very similar antigens, such as the new quadravalent products and when time is critical such as in a flu pandemic.

Data set for mass spectrometric analysis of recombinant human serum albumin from various expression systems

Human serum albumin (HSA) is a versatile and important protein for the pharmaceutical industry (Fanali et al., Mol. Aspects Med. 33(3) (2012) 209–290). Due to the potential transmission of pathogens from plasma sourced albumin, numerous expression systems have been developed to produce recombinant HSA (rHSA) (Chen et al., Biochim. Biophys. Acta (BBA)—Gen. Subj. 1830(12) (2013) 5515–5525; Kobayashi, Biologicals 34(1) (2006) 55–59). Based on our previous study showing increased glycation of rHSA expressed in Asian rice (Frahm et al., J. Phys. Chem. B 116(15) (2012) 4661–4670), both supplier-to-supplier and lot-to-lot variability of rHSAs from a number of expression systems were evaluated using reversed phase liquid chromatography linked with MS and MS/MS analyses. The data are associated with the research article ‘Determination of Supplier-to-Supplier and Lot-to-Lot Variability in Glycation of Recombinant Human Serum Albumin Expressed in Oryza sativa’ where further analysis of rHSA samples with additional biophysical methods can be found (Frahm et al., PLoS ONE 10(9) (2014) e109893). We determined that all rHSA samples expressed in rice showed elevated levels of arginine and lysine hexose glycation compared to rHSA expressed in yeast, suggesting that the extensive glycation of the recombinant proteins is a by-product of either the expression system or purification process and not a random occurrence.

Determination of supplier-to-supplier and lot-to-lot variability in glycation of recombinant human serum albumin expressed in Oryza sativa

The use of different expression systems to produce the same recombinant human protein can result in expression-dependent chemical modifications (CMs) leading to variability of structure, stability and immunogenicity. Of particular interest are recombinant human proteins expressed in plant-based systems, which have shown particularly high CM variability. In studies presented here, recombinant human serum albumins (rHSA) produced in Oryza sativa (Asian rice) (OsrHSA) from a number of suppliers have been extensively characterized and compared to plasma-derived HSA (pHSA) and rHSA expressed in yeast (Pichia pastoris and Saccharomyces cerevisiae). The heterogeneity of each sample was evaluated using size exclusion chromatography (SEC), reversed-phase high-performance liquid chromatography (RP-HPLC) and capillary electrophoresis (CE). Modifications of the samples were identified by liquid chromatography-mass spectrometry (LC-MS). The secondary and tertiary structure of the albumin samples were assessed with far U/V circular dichroism spectropolarimetry (far U/V CD) and fluorescence spectroscopy, respectively. Far U/V CD and fluorescence analyses were also used to assess thermal stability and drug binding. High molecular weight aggregates in OsrHSA samples were detected with SEC and supplier-to-supplier variability and, more critically, lot-to-lot variability in one manufactures supplied products were identified. LC-MS analysis identified a greater number of hexose-glycated arginine and lysine residues on OsrHSA compared to pHSA or rHSA expressed in yeast. This analysis also showed supplier-to-supplier and lot-to-lot variability in the degree of glycation at specific lysine and arginine residues for OsrHSA. Both the number of glycated residues and the degree of glycation correlated positively with the quantity of non-monomeric species and the chromatographic profiles of the samples. Tertiary structural changes were observed for most OsrHSA samples which correlated well with the degree of arginine/lysine glycation. The extensive glycation of OsrHSA from multiple suppliers may have further implications for the use of OsrHSA as a therapeutic product.

Surface modifications of influenza proteins upon virus inactivation by β-propiolactone

Inactivation of intact influenza viruses using formaldehyde or β-propiolactone (BPL) is essential for vaccine production and safety. The extent of chemical modifications of such reagents on viral proteins needs to be extensively investigated to better control the reactions and quality of vaccines. We have evaluated the effect of BPL inactivation on two candidate re-assortant vaccines (NIBRG-121xp and NYMC-X181A) derived from A/California/07/2009 pandemic influenza viruses using high-resolution FT-ICR MS-based proteomic approaches. We report here an ultra performance LC MS/MS method for determining full-length protein sequences of hemagglutinin and neuraminidase through protein delipidation, various enzymatic digestions, and subsequent mass spectrometric analyses of the proteolytic peptides. We also demonstrate the ability to reliably identify hundreds of unique sites modified by propiolactone on the surface of glycoprotein antigens. The location of these modifications correlated with changes to protein folding, conformation, and stability, but demonstrated no effect on protein disulfide linkages. In some cases, these modifications resulted in suppression of protein function, an effect that correlated with the degree of change of the modified amino acids' side chain length and polarity.

YAP-induced resistance of cancer cells to antitubulin drugs is modulated by a Hippo-independent pathway

Although antitubulin drugs are used widely to treat human cancer, many patients display intrinsic or acquired drug resistance that imposes major obstacles to successful therapy. Mounting evidence argues that cancer cell apoptosis triggered by antitubulin drugs relies upon activation of the cell-cycle kinase Cdk1; however, mechanistic connections of this event to apoptosis remain obscure. In this study, we identified the antiapoptotic protein YAP, a core component of the Hippo signaling pathway implicated in tumorigenesis, as a critical linker coupling Cdk1 activation to apoptosis in the antitubulin drug response. Antitubulin drugs activated Cdk1, which directly phosphorylated YAP on five sites independent of the Hippo pathway. Mutations in these phosphorylation sites on YAP relieved its ability to block antitubulin drug-induced apoptosis, further suggesting that YAP was inactivated by Cdk1 phosphorylation. Notably, we found that YAP was not phosphorylated and inactivated after antitubulin drug treatment in taxol-resistant cancer cells. Our findings suggest YAP and its phosphorylation status as candidate prognostic markers in predicting antitubulin drug response in patients.

Proteomic identification of Listeria monocytogenes surface-associated proteins

This study aimed to identify proteins exposed on the surface of Listeria monocytogenes cells for diagnostic reagent development. Brief trypsin treatment of L. monocytogenes cells followed by peptide separation and identification by nano-LC and online-MS/MS was performed. In parallel, as a negative control, proteins secreted into the digest buffer as well as proteins from cell lysis were identified. One hundred and seventy-four proteins were identified in at least two of three trials in either the negative control or during cell digest. Nineteen surface, 21 extracellularly secreted, 132 cytoplasmic, and two phage proteins were identified. Immunofluorescence microscopy of L. monocytogenes cells revealed the surface localization of two potential candidates for L. monocytogenes isolation and detection: lipoprotein LMOf2365_0546 and PBPD1 (LMOf2365_2742). In this report, we present the first data set of surface-exposed L. monocytogenes proteins currently available. The data have been deposited to the ProteomeXchange Consortium with identifier PXD000035.

Identification of a candidate proteomic signature to discriminate multipotent and non-multipotent stromal cells

Bone marrow stromal cell cultures contain multipotent cells that may have therapeutic utility for tissue restoration; however, the identity of the cell that maintains this function remains poorly characterized. We have utilized a unique model of murine bone marrow stroma in combination with liquid chromatography mass spectrometry to compare the nuclear, cytoplasmic and membrane associated proteomes of multipotent (MSC) (CD105+) and non-multipotent (CD105-) stromal cells. Among the 25 most reliably identified proteins, 10 were verified by both real-time PCR and Western Blot to be highly enriched, in CD105+ cells and were members of distinct biological pathways and functional networks. Five of these proteins were also identified as potentially expressed in human MSC derived from both standard and serum free human stromal cultures. The quantitative amount of each protein identified in human stromal cells was only minimally affected by media conditions but varied highly between bone marrow donors. This study provides further evidence of heterogeneity among cultured bone marrow stromal cells and identifies potential candidate proteins that may prove useful for identifying and quantifying both murine and human MSC in vitro.

Simultaneous quantification of the viral antigens hemagglutinin and neuraminidase in influenza vaccines by LC-MSE

Current methods for quality control of inactivated influenza vaccines prior to regulatory approval include determining the hemagglutinin (HA) content by single radial immunodiffusion (SRID), verifying neuraminidase (NA) enzymatic activity, and demonstrating that the levels of the contaminant protein ovalbumin are below a set threshold of 1 μg/dose. The SRID assays require the availability of strain-specific reference HA antigens and antibodies, the production of which is a potential rate-limiting step in vaccine development and release, particularly during a pandemic. Immune responses induced by neuraminidase also contribute to protection from infection; however, the amounts of NA antigen in influenza vaccines are currently not quantified or standardized. Here, we report a method for vaccine analysis that yields simultaneous quantification of HA and NA levels much more rapidly than conventional HA quantification techniques, while providing additional valuable information on the total protein content. Enzymatically digested vaccine proteins were analyzed by LC-MS(E), a mass spectrometric technology that allows absolute quantification of analytes, including the HA and NA antigens, other structural influenza proteins and chicken egg proteins associated with the manufacturing process. This method has potential application for increasing the accuracy of reference antigen standards and for validating label claims for HA content in formulated vaccines. It can also be used to monitor NA and chicken egg protein content in order to monitor manufacturing consistency. While this is a useful methodology with potential for broad application, we also discuss herein some of the inherent limitations of this approach and the care and caution that must be taken in its use as a tool for absolute protein quantification. The variations in HA, NA and chicken egg protein concentrations in the vaccines analyzed in this study are indicative of the challenges associated with the current manufacturing and quality control testing procedures.

Quantification of protein isoforms in mesenchymal stem cells by reductive dimethylation of lysines in intact proteins

Mass spectrometry (MS)-based quantification of highly homologous proteins in complex samples has proven difficult due to subtle sequence variations and the wide dynamic range of protein isoforms present. Herein, we report the use of reductive dimethylation on intact proteins to quantitatively compare protein isoform expression in the nucleus and cytoplasm of mesenchymal stem cells (MSC) and normal stroma. By coupling fixed-charge MS/MS scanning, high-resolution UPLC FT-MS data-dependent acquisition and MASCOT-based data mining, hydrogen/deuterium-labeled dimethyl-lysine peptides were simultaneously captured allowing the accurate comparison of 123 protein isoforms in parallel LC MS/MS runs. Thirty-four isoforms were identified that had expression levels specific to MSC. Where possible, proteomic analyses were verified by Western blotting and were demonstrated to be divergent from the level of gene transcription detected for certain proteins. Our analysis provides a protein isoform signature specific to MSC and demonstrates the suitability of dimethyl-lysine labeling on intact proteins for quantifying highly homologous proteins on a proteome-wide scale.

Universal antibodies against the highly conserved influenza fusion peptide cross-neutralize several subtypes of influenza A virus

The fusion peptide of influenza viral hemagglutinin plays a critical role in virus entry by facilitating membrane fusion between the virus and target cells. As the fusion peptide is the only universally conserved epitope in all influenza A and B viruses, it could be an attractive target for vaccine-induced immune responses. We previously reported that antibodies targeting the first 14 amino acids of the N-terminus of the fusion peptide could bind to virtually all influenza virus strains and quantify hemagglutinins in vaccines produced in embryonated eggs. Here we demonstrate that these universal antibodies bind to the viral hemagglutinins in native conformation presented in infected mammalian cell cultures and neutralize multiple subtypes of virus by inhibiting the pH-dependant fusion of viral and cellular membranes. These results suggest that this unique, highly-conserved linear sequence in viral hemagglutinin is exposed sufficiently to be attacked by the antibodies during the course of infection and merits further investigation because of potential importance in the protection against diverse strains of influenza viruses.

Strain identification of commercial influenza vaccines by mass spectrometry

Current influenza vaccine manufacturing and testing timelines require that the constituent hemagglutinin (HA) and neuraminidase (NA) strains be selected each year approximately 10 months before the vaccine becomes available. The threat of a pandemic influenza outbreak requires that more rapid testing methods be found. We have developed a specialized on-filter sample preparation method that uses both trypsin and chymotrypsin to enzymatically digest peptide-N-glycosidase F (PNGase F)-deglycosylated proteins in vaccines. In tandem with replicate liquid chromatography-mass spectrometry (LC-MS) analyses, this approach yields sufficient protein sequencing data (>85% sequence coverage on average) for strain identification of HA and NA components. This has allowed the confirmation, and in some cases the correction, of the identity of the influenza strains in recent commercial vaccines as well as the correction of some ambiguous HA sequence annotations in available databases. This method also allows the identification of low-level contaminant egg proteins produced during the manufacturing process.

Application of deglycosylation and electrophoresis to the quantification of influenza viral hemagglutinins facilitating the production of 2009 pandemic influenza (H1N1) vaccines at multiple manufacturing sites in China

The single radial immunodiffusion (SRID) method currently used to determine the hemagglutinin (HA) content of the inactivated influenza vaccines depends on the availability of reference HA antigen and corresponding anti-serum, updated and provided annually by World Health Organization (WHO) collaborative centers. Particularly early in a pandemic outbreak, reference reagents could be the bottleneck in vaccine development and release. Therefore, other reliable tests capable of quantifying HA content could substantially shorten the time needed for vaccine formulation. Here electrophoretic separation of deglycosylated samples in conjunction with densitometry was used to quantify HA contents of H1N1 vaccine at multiple manufacturing sites. We found the overall consistency between the alternative method and traditional SRID was 88-122% in seven lots of vaccine bulks from four subtypes (types) of influenza vaccine, confirming its suitability to quantify HA content. Moreover, we used the alternative method to prepare a national HA antigen reference in China for quality control of 2009 pandemic influenza A (H1N1) vaccines prior to the arrival of the WHO SRID reference standards, subsequently confirming good agreement between both methods. The alternative method for vaccine quantification enabled the Chinese health authority to approve H1N1 vaccine 1 month earlier than otherwise possible.

Physical and genetic characterization of an outer-membrane protein (OmpM1) containing an N-terminal S-layer-like homology domain from the phylogenetically Gram-positive gut anaerobe Mitsuokella multacida

Thin sectioning and freeze-fracture-etch of the ovine ruminal isolate Mitsuokella multacida strain 46/5(2) revealed a Gram-negative envelope ultra-structure consisting of a peptidoglycan wall overlaid by an outer membrane. Sodium-dodecyl-sulfate-polyacrylamide gel electrophoretic (SDS-PAGE) analysis of whole cells, cell envelopes and Triton X-100 extracted envelopes in combination with thin-section and N-terminal sequence analyses demonstrated that the outer membrane contained two major proteins (45 and 43 kDa) sharing identical N-termini (A-A-N-P-F-S-D-V-P-A-D-H-W-A-Y-D). A gene encoding a protein with a predicted N-terminus identical to those of the 43 and 45 kDa outer-membrane proteins was cloned. The 1290 bp open reading frame encoded a 430 amino acid polypeptide with a predicted molecular mass of 47,492 Da. Cleavage of a predicted 23 amino acid leader sequence would yield a protein with a molecular mass of 45,232 Da. Mass spectroscopic analysis confirmed that the cloned gene (ompM1) encoded the 45 kDa outer-membrane protein. The N-terminus of the mature OmpM1 protein (residues 24-70) shared homology with surface-layer homology (SLH) domains found in a wide variety of regularly structured surface-layers (S-layers). However, the outer-membrane locale, resistance to denaturation by SDS and high temperatures and the finding that the C-terminal residue was a phenylalanine suggested that ompM1 encoded a porin. Threading analysis in combination with the identification of membrane spanning domains indicated that the C-terminal region of OmpM1 (residues 250-430) likely forms a 16-strand beta-barrel and appears to be related to the unusual N-terminal SLH-domain-containing beta-barrel-porins previously described in the cyanobacterium Synechococcus PCC6301.

The value of proteomics for the diagnosis of a platelet-related bleeding disorder

Familial bleeding problems are frequently difficult to diagnose because currently used clinical tests cannot identify intracellular molecular defects of platelets. Using platelet proteomics, a comprehensive analytical tool, we diagnosed a family with severe bleeding problems of unknown origin with Quebec Platelet Disorder. Prior to proteomic analysis, we determined platelet counts, presence of glycoprotein (GP) Ib and GPIIb/IIIa, platelet aggregation, dense granule content and release, plasma levels of fibrinogen, Factor XIII and fibrin degradation products in four family members. Abnormalities were detected in platelet aggregation studies, which revealed variably reduced responses to ADP, collagen and epinephrine with concomitantly decreased ATP/serotonin secretion. In addition, D-dimer levels were significantly elevated 72 hours after in vitro thrombin stimulation of platelet-rich plasma. Together with the autosomal dominant inheritance and the delayed onset of bleeding in two of the four patients these results did not support any known platelet disorder. Therefore, the proteome of platelet lysates separated by one-dimensional SDS-PAGE was analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Platelet proteomics showed reduced amounts of alpha-granule proteins multimerin, fibrinogen and thrombospondin-1 in patient compared to control samples suggestive of Quebec Platelet Disorder. The diagnosis of Quebec Platelet Disorder was confirmed by urokinase-specific Western blots. Urokinase causes the degradation of alpha-granule proteins in this disorder. Diagnosis of rare bleeding disorders has important implications for prophylactic and acute treatment of bleeding patients. This is the first report using proteomics to identify a familial platelet defect.

Selective and Quantitative Detection of Influenza Virus Proteins in Commercial Vaccines Using Two-Dimensional High-Performance Liquid Chromatography and Fluorescence Detection

In this work, we report on the applicability of two-dimensional high-performance liquid chromatography (2D-HPLC) for the comprehensive characterization of inactivated influenza vaccine proteins. This novel procedure features minimal sample treatment and combines the on-line coupling of size exclusion HPLC to reversed-phase HPLC. A comparative analysis of commercial vaccines from three different manufacturers showed the method to be highly selective by providing characteristic reproducible chromatographic profiles for each vaccine. In addition, the method provided enhanced sensitivity for most constituents as a result of the use of native fluorescence detection in the reversed-phase HPLC step. The limits of detection (at a signal-to-noise ratio of >3) for hemagglutinin (HA) antigens were 105 and 172 ng/mL for influenza A/New Caledonia/20/99 and B/Jiangsu/10/2003 strains, respectively. The potential of this 2D-HPLC procedure in terms of quantitative antigen analysis was assessed by determination of the HA content of commercial vaccines. Results provided very good correlation with nominal HA values. The reproducibility (RSD) of the whole procedure was also evaluated and was found to be better than 2 and 3% for calculated antigen concentrations expressed as micrograms of HA per milliliter in commercial vaccines for samples of the same lot (n = 5) or different lots (n = 3), respectively. In addition, it allowed the selective detection of several influenza constituents including nucleoproteins from type A and B viruses and the highly hydrophobic matrix protein 1 from both virus strains.

A novel surface autolysin of Listeria monocytogenes serotype 4b, IspC, contains a 23-residue N-terminal signal peptide being processed in E. coli

The 86-kDa protein IspC of 774 amino acids in Listeria monocytogenes serotype 4b has been recently identified as the target of humoral immune response to listerial infection and as a novel surface autolysin. A signal peptide is predicted at the N-terminal end of IspC, but no biochemical data has been shown to confirm the presence of the cleavage site of a signal peptidase. To address this and prepare sufficient amount of the protein for biochemical and structural characterization, we present a strategy for efficient expression and purification of IspC and analyze the purified protein by N-terminal sequencing and mass spectrometry. Expression of IspC in Escherichia coli using a pET30a-based expression construct was efficiently improved by incubating the culture at 37 degrees C for 2h followed by 4 degrees C for 16-18 h. The recombinant product rIspC remained as a soluble form in the cellular extract and was purified to electrophorectic homogeneity by the combination of metal chelate affinity chromatography with cation-exchange chromatography. The IspC was shown to contain a 23-residue N-terminal signal peptide being processed between Thr 23 and Thr 24 in E. coli, resulting in an 84-kDa mature protein. The highly purified form of rIspC from this study, exhibiting both peptidoglycan hydrolase activity and immunogenicity as previously reported, would facilitate further biochemical, structural, and functional studies of this autolysin.

Proteomic and microscopic analysis of biofilms formed by Listeria monocytogenes 568

Biofilm formation may be important in the colonization of the food-processing environment by the food-borne pathogen Listeria monocytogenes. Listeria monocytogenes 568 formed adherent multicellular layers on a variety of test surfaces following growth at 37 degrees C with multiple transfers of the test surface into fresh medium. Microscopic examination of these adherent layers suggest that the cells were surrounded by extracellular material. The presence of a carbohydrate containing extracellular polymeric matrix was confirmed by labelling hydrated adherent layers with fluorescein-conjugated concanavalin A, indicating that these adherent layers are biofilms. To gain insight into the physiological state of cells in these biofilms, the proteomes from biofilm- and planktonic-grown cells from the same cultures were compared using 2-dimensional polyacrylamide gel electrophoresis. Nineteen proteins, which exhibited higher levels of expression in biofilm-grown cells, were successfully identified from the 2-D gels using a combination of MALDI-TOF and MS/MS. Proteins that were found to be more highly expressed in biofilm-grown cells were involved in stress response, envelope and protein synthesis, biosynthesis, energy generation, and regulatory functions. In biofilm-grown cells, many proteins in the pH range 4-6 ran as multiple spots arranged horizontally across the 2-D gels.

Butyrivibriocin AR10, a new cyclic bacteriocin produced by the ruminal anaerobe Butyrivibrio fibrisolvens AR10: characterization of the gene and peptide

The gene (bviA) encoding the ruminal bacteriocin butyrivibriocin AR10 was cloned from an EcoRI library by using an oligonucleotide probe based on a partial peptide sequence of the previously isolated peptide. The gene encoded an 80 amino acid prebacteriocin that demonstrated significant identity with the cyclic bacteriocin gassericin A. Negative ion time of flight mass spectroscopic analysis (ESI/MS) indicated a mass of 5981.5 Da for the isolated bacteriocin, a molecular mass that could not be generated by removal of a leader peptide alone. However, an N- to C-terminal cyclization of the predicted mature bacteriocin resulted in a peptide that conformed to the determined mass and charge characteristics. Northern blotting confirmed that expression of bviA mirrored the production of the bacteriocin in both liquid and solid media.

Fenofibrate raw materials: HPLC methods for assay and purity and an NMR method for purity

HPLC methods for drug content and HPLC and NMR methods for related compounds in fenofibrate raw materials were developed. The HPLC methods resolved 11 known and six unknown impurities from the drug. The HPLC system was comprised of a Waters Symmetry ODS column (100 x 4.6 mm, 3.5 microm), a mobile phase consisting of acetonitrile water trifluoroacetic acid 700/300/l (v/v/v) at a flow rate of 1 ml min(-1). and a UV detector set at 280 nm. Minimum quantifiable amounts were about 0.1% for three of the compounds and less than 0.05% for the other eight. Individual impurities in 14 raw materials ranged from trace levels to 0.25%, and total impurities from 0.04 to 0.53% (w/w). Six unknown impurities were detected by HPLC, all at levels below 0.10%, assuming the same relative response as fenofibrate. An NMR method for related compounds was also developed and it was suitable for 12 known and several unknown impurities. It requires an NMR of 400 MHz, or greater, field strength. Individual impurities in the raw materials analyzed ranged from trace levels to 0.24%, and total impurities from trace levels to 0.59%. Several lots contained small amounts of unknown impurities at trace levels. Three lots, all from the same manufacturer, contained an unknown impurity, not detectable by HPLC, which was not present in the other raw materials. It was estimated to be present at a level greater than 0.2%. The results for related compounds by the two techniques were consistent. The main differences stem from the low sensitivity of the HPLC method for some of the related compounds at 280 nm, or from the higher limits of quantitation by the NMR method for several other impurities using the conditions specified. A fifteenth raw material was not homogeneous in its content of impurity VI, a synthetic intermediate and possible degradation product. The HPLC/MS results provided information on the peak purity (number of components) for minor HPLC peaks, as well as structural data such as the molecular ions and diagnostic fragment ions. The HPLC/MS results showed that there were five unknown drug related impurities, for which there were no standards available. Results for the assay of 15 raw materials by HPLC were within the range 98.5-101.5%.

Use of capillary electrophoresis for the characterization of human serum albumin heterogeneity

Human serum albumin (HSA) is used in large amounts as an excipient in many biopharmaceutical formulation to prevent loss of the active ingredient through adsorption and/or degradation. Traditionally, iso-electric focusing has been used to demonstrate charge heterogeneity in HSA preparations. In an effort to develop new methods for the analysis of formulation components, a capillary zone electrophoresis method was developed for the analysis of HSA. Under initial separation conditions using untreated silica capillaries and 20 mM sodium phosphate, pH 6.0 as electrophoretic buffer, HSA migrated as a single peak. Addition of 1,4-diaminobutane allowed separation of several components which could be further resolved by varying the buffer pH. Optimal separation conditions were attained at 5 mM 1,4-diaminobutane and pH 8.5. The reproducibility of the separation conditions was verified by using capillaries from a different manufacturer. A comparative analysis of HSA preparations from different manufacturers provided evidence that the method may be used to qualitatively differentiate individual preparations. The analysis of rhEPO formulations, composed largely of HSA, showed levels of heterogeneity comparable to that of HSA preparations. Electrospray ionisation mass spectrometry (ESA-MS) was used as an independent method to confirm the heterogeneous nature of HSA.

Metered dose inhalers III: Metaproterenol sulphate; particle size distribution and dose uniformity

Three American products and one Canadian product were examined for content uniformity and particle size distribution. The results showed that not all products performed equally well. Some of the products exhibited high sprays early in the canister lifetime and all products demonstrated loss of prime. The particle size distributions were determined using the Andersen cascade impactor (USP Induction Port) and the fine particle fraction was determined using the twin impinger. The results showed that three of the four products had similar particle size distribution profiles. Both the Andersen cascade impactor and the twin impinger yielded the same trends in the amount of drug substance delivered to the fine particle fraction.

Characterisation of human serum albumin heterogeneity by capillary zone electrophoresis and electrospray ionization mass spectrometry

Human serum albumin (HSA) preparations and HSA-containing recombinant human erythropoietin (rhEPO) formulations were analyzed by capillary zone electrophoresis. HSA was separated into several components by the addition of 1,4-diaminobutane to 20 mM sodium phosphate, pH 6.0 as electrophoretic buffer. Resolution was improved by increasing the buffer pH to 8.5. A comparative analysis of HSA preparations from three manufacturers provided evidence that this method can be used to differentiate individual preparations. The analysis of rhEPO formulations, composed largely of HSA, showed levels of heterogeneity comparable to that of HSA preparations. Electrospray ionisation mass spectrometry was used as an independent method to confirm the heterogeneous nature of HSA.

Spectral characterization of fluconazole

Reference 1H, 19F and 13C NMR, mass, IR and Raman spectra are provided to the open literature for the first time for the potent antifungal agent fluconazole, alpha-(2,4-difluorophenyl)-alpha-(1H-1,2,4-triazol-1-ylmethyl++ +)-1H-1,2, 4-triazole-1-ethanol. The 1H, 19F and 13C NMR spectra were analyzed in detail to attribute shifts, including 19F chemical shifts and C-F and F-F coupling constants. The EI mass spectrum, although rich in fragment ions, lacked a molecular ion. FAB and MS/MS experiments were undertaken in support of the structure in order to validate the EI spectrum as a reference mass spectrum. IR and Raman spectra are compared to show the complementary nature of their features and discussed in terms of principal group vibrations. NMR and vibrational data together with assignments are summarized in tabulated form for convenience of use. All these data are consistent with the structure of fluconazole.

Metabolism of methoxyphenamine and 2-methoxyamphetamine in P4502D6-transfected cells and cell preparations

1. Control and P4502D6-transfected human B-lymphoblastoid cell lines (cHol and h2D6v2 respectively) were used to study 2D6-mediated metabolism of methoxyphenamine (MPA) and 2-methoxyamphetamine (2MA). The main metabolites were products of O-dealkylation and aromatic hydroxylation at the 5-position. In addition, N-desmethyl-methoxyphenamine (NDMP) was also identified as a minor metabolite of MPA in extracts of these cells, confirming previous reports of 2D6-mediated N-demethylation of MPA. 2. An additional ring-hydroxylated metabolite of MPA and 2MA has been tentatively identified as the corresponding 3-hydroxy-2-methoxy derivative. 3. MPA metabolism in whole cells was time dependent, with approximately 30% of the MPA metabolized after 72 h. A 35% conversion of MPA was achieved on average with cell lysates. Only 18% 2MA was metabolized. By contrast, control cells (cHol) showed no evidence of any MPA or 2MA metabolites even after 96-h incubation. 4. Continuous presence of haemin/dimethylsulphoxide (DMSO) throughout the 4-day incubation with MPA resulted in a shift in the metabolite profile towards the production of NDMP at the expense of the other products. 5. In summary, h2D6v2 cells, lysates and microsomes can form all metabolites of MPA and can be used in drug interaction studies.

The influence of pregnancy on the biotransformation and urinary excretion of methoxyphenamine in mice

(i) The urinary elimination of methoxyphenamine (MPA) and its metabolites in underivatized samples was examined after single and multiple oral administration to pregnant and non-pregnant mice by GLC and GLC-MS. (ii) The major metabolite O-desmethylmethoxyphenamine (ODMP), along with lesser amounts of N-desmethylmethoxyphenamine (NDMP) and 2-hydroxyamphetamine (2OH), were the only metabolites detected in urine extracts of pregnant and non-pregnant mice. 5-Hydroxymethoxyphenamine (5HMP) was not detected. Enzyme hydrolysis did not increase the recovery of either substrate or metabolites in either the pregnant or non-pregnant animals. The results show that MPA metabolism in the Swiss-Webster mouse is distinctly different from that seen in man and other laboratory animals. (iii) The mean MPA:ODMP ratio in day-6 urine from pregnant mice after a single dose was 0.31 +/- 0.04. The NDMP:ODMP ratios were less than 0.10 in all samples. Non-pregnant mice urine had equivalent amounts of MPA, NDMP, ODMP, and 2OH after multiple dosing. (iv) While multiple dosing and pregnancy did not alter either the urinary recovery or profile of the metabolites detected, there was a linear decrease in the MPA:ODMP ratio during gestation. (v) MPA was extensively metabolized to ODMP in the male mice, and the MPA:ODMP ratio of 0.41 was slightly higher than that observed in the pregnant and non-pregnant females.

Mouse hepatic metabolites of ketoconazole: isolation and structure elucidation

Oxidation, cleavage and degradation of the imidazole and piperazine rings, O-dealkylation, and aromatic hydroxylation are the reported pathways of ketoconazole (KC) metabolism. Metabolites were examined in hepatic extracts from male Swiss Webster mice treated with KC (350 mg kg-1 po x 7 days) in a 0.25% gum tragacanth suspension at 10 ml kg-1. Livers were collected 24 h after the last dose and stored at -70 degrees C. A mixture of chloroform/methanol extracts of liver homogenates were dried under vacuum and methanol extracts of the residue were chromatographed by a series of preparative and analytical HPLC techniques. Structure assignments were made by NMR and MS/MS techniques. It was demonstrated that KC was biotransformed to a number of products. Nine were isolated and seven identified as exclusive products of the biotransformation of the 1-acetylpiperazine moiety of KC. This substituent was biotransformed to the following: piperazine (de-N-acetyl ketoconazole, DAKC), N-carbamylpiperazine, N-formylpiperazine, 2,3-piperazinedione, 2-formamidoethylamine, ethylenediamine and amine. The 1H-NMR and MS data suggested that the remaining two metabolites were products resulting from the oxidation of the imidazole ring.

Design of potent and selective dynorphin A related peptides devoid of supraspinal motor effects in mice

Dynorphin A-(1-13)-Tyr-Leu-Phe-Asn-Gly-Pro (Dyn Ia) was previously shown to be a highly potent and selective kappa opioid peptide. Four analogs of Dyn Ia are synthesized by the solid-phase procedure, introducing pseudo CH2NH linkage between positions 6 and 7 as follows: analog 1, [6 psi 7 (CH2NH)]Dyn Ia; analog 2, [6 psi 7 (CH2NH), D-Leu8]Dyn Ia; analog 3, [N(Me)-Tyr1, 6 psi 7 (CH2NH)]Dyn Ia; and analog 4, [N(Me)-Tyr1, 6 psi 7 (CH2NH), D-Leu8]Dyn Ia. The purified peptides are compared in vitro with Dyn Ia for their ability to compete with the binding of selective kappa, mu, and delta opioid ligands using membrane preparations of guinea pig cerebellum (kappa) and rat brain (mu and delta). The synthetic compounds are also compared in vivo in mice (intracerebroventricularly administered) for their analgesic activity against acetic acid induced writhing and their ability to produce motor dysfunction. All compounds display a high affinity (Ki = 0.5-1.8 nM) and a good selectivity for the kappa opioid receptor, and their rank order of potency on the kappa site (analog 2 > analog 1 > analog 3 > analog 4) closely parallels their potency (AD50 = 1.57-5 nmol/mouse) in inhibiting acetic acid induced writhing in mice (analog 2 > analog 1 > analog 4 > analog 3). On the other hand, all the synthetic analogs are less potent than Dyn Ia in producing motor effects, analog 2 being the least potent (CD50 = 15.4 nM as compared with 2.9 nM for Dyn Ia).(ABSTRACT TRUNCATED AT 250 WORDS)

Gas Chromatographic Methods for Doxepin Isomers, Related Compounds, and Organic Volatile Impurities in Raw Materials and Doxepin Isomers in Capsules

Gas chromatographic methods have been developed for the determination of doxepin as the sum of the resolved E and Z isomers, 4 doxepin-related compounds, and organic volatile impurities in drug raw material. Minimum quantifiable amounts of the related compounds in raw materials are less than 0.05%. A method for assay of doxepin, as the total of the E and Z isomers, in capsules was also developed; relative standard deviation is less than 1% for the drug assay. Eleven raw material and 18 capsule samples were examined. No drug-related compounds or U.S. Pharmacopeia- or European Pharmacopeia-limited organic volatile impurities were detected in any of the samples.

The influence of sampling chamber dimensions on aerosol particle size measurement by cascade impactor and twin impinger

The influence of the sampling chamber dimensions upon particle size estimation by cascade impaction has been investigated and compared with measurements by the twin impinger. Aerosols of salbutamol and disodium fluorescein (DF) were generated from pressurized metered dose inhalers. The mass median aerodynamic diameter (MMAD) by the Andersen Impactor for salbutamol ranged from 2.0 to 2.8 microns with geometric standard deviations (g.s.d.) of 1.7 to 2.4. These observations were independent of the distance travelled to the first impaction surface of the impactor and volume of the sampling chamber. The DF MMAD ranged from 5.0 to 6.9 microns with g.s.d. values of 1.7 to 1.8. Changes in droplet size within the sampling chamber may cause significant differences in particle size estimates as indicated by the cascade impaction data for DF. The respirable fraction of the salbutamol samples was similar whether determined by impaction or using the impinger. The latter device has previously been indicated to give clinically relevant estimates of respirable fraction for commercial inhalation aerosol devices.

Methods for Assay, Related Substances, and Organic Volatile Impurities in Triazolam Raw Materials and Formulations

Liquid chromatographic methods have been developed for determination of triazolam and related compounds in drug raw materials and tablets. The methods resolve 9 available related compounds from the drug with quantitation limits of 0.1 % or less. Eight raw materials and 16 formulations were examined for related compounds. Total impurities in raw materials ranged up to 0.6% and up to 1% in formulations, not including a compound in some tablets that is believed to be excipient related. Assay values were between 99.9 and 101.3% for raw materials and between 89.4 and 105.5% for tablets. A gas chromatographic method was developed for organic volatile Impurities in drug raw materials. The major solvents found were methyl ethyl ketone (100-750 ppm), ethyl acetate (510 ppm), and n-propanol (80-300 ppm), with a trace of benzene (<30 ppm) in several samples.

Liquid Chromatographic Method for Selegiline Hydrochloride and Related Compounds in Raw Materials and Tablets

A liquid chromatographic method has been developed for determination of selegiline hydrochloride and related substances in drug raw material and tablet formulations. The method resolves 3 known related compounds from the drug with a limit of quantitation of less than 0.05%. Drug raw material and tablet samples contained ca 0.2 and 0.6% impurities, respectively. These included some related compounds, the identities of which were confirmed by gas chromatography with a Fourier transform Infrared detector.

Liquid chromatographic methods for the determination of albuterol (salbutamol), albuterol sulphate and related compounds in drug raw materials, tablets and inhalers

Liquid chromatographic methods for the determination of albuterol (salbutamol), albuterol sulphate and related compounds in drug raw materials, tablets and inhalers are described. The methods resolve five known related compounds from the drug and, in the case of inhalers, several compounds not related to the drug. Two of these were identified as 2,6-di-t-butyl-4-methylphenol, a common antioxidant, and 2,2'-methylene bis(6-t-butyl-4-methylphenol). Related compounds are detectable at levels of about 0.03%. Eleven albuterol and 12 albuterol sulphate raw materials and eight tablet formulations were found to contain related compounds ranging from 0.03 to 0.54%, 0.09 to 0.50% and 0.32 to 0.95%, respectively. Non-drug compounds in three inhaler samples ranged from 4.6 to 12% of the drug delivered through the valve. Some of the non-drug compounds may be excipients.

Determination of Size Distribution of Fat Globules in Intravenous Fat Emulsions by Photon Correlation Spectroscopy

A photon correlation spectroscopy method has been developed to characterize the size distribution of fat globules in intravenous fat emulsions (IFE) in terms of mean diameter, standard deviation of the distribution, and percentage of large particles outside the distribution. Mean fat globule diameters of samples of all IFE products available in Canada were about 0.3 μm, similar to values reported in the literature. The methodology is sufficiently sensitive to detect the presence of 5% by weight of 2 μm polystyrene microspheres in an intravenous fat emulsion. The effect of changes in instrument settings and variables on the results has been evaluated.

Determination of size distribution of fat globules in intravenous fat emulsions by photon correlation spectroscopy

A photon correlation spectroscopy method has been developed to characterize the size distribution of fat globules in intravenous fat emulsions (IFE) in terms of mean diameter, standard deviation of the distribution, and percentage of large particles outside the distribution. Mean fat globule diameters of samples of all IFE products available in Canada were about 0.3 microns, similar to values reported in the literature. The methodology is sufficiently sensitive to detect the presence of 5% by weight of 2 microns polystyrene microspheres in an intravenous fat emulsion. The effect of changes in instrument settings and variables on the results has been evaluated.

High-performance liquid chromatography method for assay of diltiazem hydrochloride and its related compounds in bulk drug and finished tablets

The method provides for the resolution of trans-diltiazem and seven known and several unknown related compounds from diltiazem HCl. Minimum detectable amounts were less than 0.1%, except for an intermediate which originates early in the synthetic process, for which the sensitivity is approximately 2%. The relative standard deviation of the assay procedure is 0.15%. Total related compounds in four bulk drug and four tablet samples were less than 0.25%. The specific rotation of four samples of diltiazem HCl analyzed in duplicate was between +112 and +114 degrees. The UV absorption spectra of all compounds exhibited two maxima, one between 203 and 213 nm and the other between 230 and 244 nm.

Titrimetric Determination of Nonesterified Fatty Acids in Intravenous Fat Emulsions

A titrimetric method, suitable for use at a limit of 5 mEq/L, has been developed for the determination of total noncsterified fatty acids in intravenous fat emulsion preparations. The method differentiates titrant consumed by the nonesterified fatty acids from that consumed by egg yolk phospholipids, usually present as an emulsifying agent. The total nonesterified fatty acids in 8 products from 4 manufacturers were in the range from 0.4 to 3.8 mEq/L. The mean standard deviation of the method is 0.09 mEq/L.

Titrimetric determination of nonesterified fatty acids in intravenous fat emulsions

A titrimetric method, suitable for use at a limit of 5 mEq/L, has been developed for the determination of total nonesterified fatty acids in intravenous fat emulsion preparations. The method differentiates titrant consumed by the nonesterified fatty acids from that consumed by egg yolk phospholipids, usually present as an emulsifying agent. The total nonesterified fatty acids in 8 products from 4 manufacturers were in the range from 0.4 to 3.8 mEq/L. The mean standard deviation of the method is 0.09 mEq/L.