Patent Application
20130295099
The invention relates to an N-linked glycan compound of Formula 1, which optionally may be fused or attached to an amino acid, peptide, protein or lipid. The invention further relates to antibodies and antisera against such compound, and the use thereof to diagnose an infection caused by a Campylobacter pathogen. The invention further relates to the use of the compound as a vaccine to treat or prevent infection by a Campylobacter pathogen.
Campylobacter jejuni and Campylobacter coli are the two most commonly isolated species of campylobacter that cause human infection. These organisms cause high rates of gastroenteritis worldwide, with the number of cases often exceeding that for Salmonella, Shigella and Enterotoxigenic E. coli combined (Butzler J P, Clinical Microbiology and Infection 2004). Furthermore, C. jejuni infection has been linked to the development of Guillain-Barré Syndrome, the most common cause of pathogen-caused paralysis since the eradication of polio (for reviews see: Kaida K, Glycobiology, 2009; Bereswill S & Kist M, Current Opinion in Infectious Diseases, 2003). Other Campylobacter species have been recognized as emerging pathogens in human gastroenteritis (C. upsaliensis) were associated with inflammatory bowel disease in children and with gingivitis and periodontitis (C. concisus) (Zhang L S et al., Journal of Clinical Microbiology, 2009), like C. jejuni and C. coli) associated with diarrheal disease (C. hyointestinalis) and in causing venereal disease and infertility in livestock (especially cattle; C. fetus venerealis), and sheep abortions (C. fetus fetus) (Butzler J P, Clinical Microbiology and Infection, 2004 and references therein).
Since the publication of the first C. jejuni genome sequence in 2000 (Parkhill J et al., Nature, 2000), several other campylobacter genome sequences have been reported. Unlike the majority of bacteria that have been described to date, all campylobacters contain conserved pgl genes required for N-linked protein glycosylation (Szymanski C M & Wren B W, Nature Reviews Microbiology 2005; Nothaft H & Szymanski C M, Nature Reviews Microbiology, 2010).
In eukaryotes, glycosylated proteins are ubiquitous components of extracellular matrices and cellular surfaces. Their oligosaccharide moieties are implicated in a wide range of cell-cell and cell-matrix recognition events that are vital in biological processes ranging from immune recognition to cancer development. Glycosylation was previously considered to be restricted to eukaryotes, however through advances in analytical methods and genome sequencing, there have been increasing reports of both O-linked and N-linked protein glycosylation pathways in bacteria (Nothaft H & Szymanski C M, Nature Reviews Microbiology, 2010). Since the discovery of the first general protein glycosylation pathway in bacteria (Szymanski C M et al., Molecular Microbiology 1999), the demonstration that the C. jejuni glycans are attached through an N-linkage en bloc (Kelly J H et al., Journal of Bacteriology 2006, Wacker M et al., Science 2002, Young N M et al., Journal of Biological Chemistry, 2002) and that the pathway not only can be functionally transferred into Escherichia coli (Wacker M et al., Science, 2002), but that the oligosaccharyltransferase enzyme (PglB) is capable of adding foreign sugars to protein (Feldman M et al., PNAS 2005), a surge of research activities has resulted in further characterization and exploitation of this system.
The detailed structure of the unique C. jejuni N-linked heptasaccharide has been described (Young N M et al., Journal of Biological Chemistry, 2002). Using methods such as high resolution magic angle spinning (HR-MAS) NMR (Szymanski C M et al., Journal of Biological Chemistry, 2003), it has been shown that this heptasaccharide is conserved in structure in both C. jejuni and Campylobacter coli.
An intermediate in the C. jejuni N-linked glycosylation pathway has been described, namely a free (oligo-) heptasaccharide (fOS)—a soluble component of the C. jejuni periplasmic space (Liu X et al., Analytical Chemistry, 2006). This fOS has the identical structure as the N-linked oligosaccharide added onto proteins (Nothaft H et al., PNAS 2009). Under laboratory growth conditions, the ratio of fOS versus heptasaccharide N-linked to protein is approximately 9:1. The fOS in C. jejuni plays a role in osmoregulation similar to bacterial periplasmic glucans and this pathway can be manipulated by altering the environmental osmolyte concentration (Nothaft H et al., PNAS 2009).
We have determined the N-glycan and fOS structures from a number of Campylobacter species, all of which possess N-linked glycans and fOS. In addition, we demonstrated that campylobacter N-glycans and fOS can be divided into two structural groups. The first group produces a similar structure to that published for C. jejuni and C. coli (Young N M et al., Journal of Biological Chemistry, 2002; Szymanski C M et al., Journal of Biological Chemistry, 2003). The second group produces a unique glycan structure which differs from that determined for C. jejuni and C. coli and that have never been described before. Campylobacter species that fall into this group include Campylobacter fetus venerealis (cause of venereal disease and infertility in cattle), Campylobacter fetus fetus (cause of sheep abortions), Campylobacter concisus (associated with gingivitis and periodontitis, and has been isolated from the feces of patients with gastroenteritis), Campylobacter hyointestinalis (like C. jejuni and C. coli, is associated with diarrheal disease), Campylobacter hyointestinalis subspecies, Campylobacter sputorum and Campylobacter sputorum subspecies, Campylobacter lanienae, Campylobacter ureolyticus (an emerging enteric pathogen suggested to be involved in gastroenteritis, Bullman S et al., FEMS Immunology & Medical Microbiology, 2010).
Campylobacter hominis, Campylobacter gracilis, Campylobacter rectus, Campylobacter showae, Campylobacter mucosalis and Campylobacter curvus are believed to be within the second group.
According to one aspect, the invention relates to a novel N-linked glycan (referred to as N-glycan) compound of Formula 1: A-GlcNAc[GlcNAc]-GalNAc-GalNAc-QuiNAc4NAc, wherein A is GlcNAc or Glc. This compound in its native form is common to several Campylobacter species. In its native form, the compound is soluble in the periplasm as well as attached to inner membrane and periplasmic proteins and most notably surface outer membrane proteins of many Campylobacter species, including pathogens. In the present invention, the compound of Formula 1 is provided in isolated and/or purified form. The compound comprises two hexasaccharides which differ from each other in a terminal sugar, which comprises either Glc or GlcNAc. The first of said compounds is: GlcNAc-GlcNAc[GlcNAc]-GalNAc-GalNAc-QuiNAc4NAc (herein Formula 1A). The second of said compounds is: Glc-GlcNAc[GlcNAc]-GalNAc-GalNAc-QuiNAc4NAc (herein Formula 1B).
In the above Formula 1, QuiNAc4NAc represents an alternative signifier of the saccharide Bac, which constitutes an abbreviation of bacillosamine.
In one aspect the invention relates to an isolated or purified compound comprising the compound of Formula 1 connected or linked to a single amino acid, an oligopeptide, a peptide, a protein, or a lipid. In one aspect, the oligopeptide or peptide comprises between 2 and 40 amino acids, or between 2 and 30 amino acids, or between 2 and 20 amino acids, or between 2 and 10 amino acids.
The invention further relates to a method of producing an antibody or antiserum comprising the steps of providing the compound of Formula 1, inoculating an animal or humans with said compound to stimulate an immune response to said compound, withdrawing serum from said animal and optionally purifying said serum to obtain the antibody or antiserum. The resulting antibody or antiserum binds to Campylobacter species wherein the glycan described herein is native thereto, including Campylobacter fetus venerealis, Campylobacter fetus fetus, Campylobacter concisus, Campylobacter hyointestinalis and Campylobacter hyointestinalis subspecies, Campylobacter sputorum and Campylobacter sputorum subspecies, Campylobacter lanienae, Campylobacter ureolyticus, Campylobacter hominis, Campylobacter gracilis, Campylobacter rectus, Campylobacter showae, Campylobacter mucosalis and Campylobacter curvus.
The antibody or antiserum can be used for diagnostic purposes, to detect the presence of said organisms in an animal or in a human.
Compounds of the present invention may be used in a vaccine formulation, with or without an adjuvant, against Campylobacter fetus venerealis, which is a major cause of reproductive failure in cattle and for which the current vaccine is of limited use, or against other Campylobacter species wherein the glycan of Formula 1 is native to such organism, including the species listed above. Compounds of the present invention have possible uses in protein glycoengineering, therapeutic and diagnostic applications. The invention thus relates to a vaccine comprising the compound of Formula 1, optionally connected or linked to a single amino acid, an oligopeptide, a peptide, a protein, or a lipid. The single amino acid may comprise asparagine.
The invention further relates to the use of said vaccine to treat or prevent an infection caused by a Campylobacter organism, wherein the compound of Formula 1 comprises a native glycan within said organism, and a method of treatment comprising said use, within a human or animal.
According to another aspect, the invention relates to a method of improving the productivity and health of an animal herd by administering to said herd the vaccine as described above.
The vaccines, antibodies and antisera described herein may also be used to for prevention, treatment and diagnosis in humans.
The present invention relates to the glycan compound A-GlcNAc[GlcNAc]-GalNAc-GalNAc-QuiNAc4NAc, wherein A is GlcNAc or Glc. The above compound encompasses the two glycan compounds GlcNAc-GlcNAc[GlcNAc]-GalNAc-GalNAc-QuiNAc4NAc (herein Formula 1A) and Glc-GlcNAc[GlcNAc]-GalNAc-GalNAc-QuiNAc4NAc (herein Formula 1B).
In the above Formulae, QuiNAc4NAc represents an alternative signifier of the saccharide Bac, which constitutes an abbreviation of bacillosamine. The compound of Formula 1 is optionally connected or linked to a single amino acid, an oligopeptide, a peptide, a protein, or a lipid.
Said lipid can be isolated and purified from a bacterial, archaeal or eukaryotic source or can be chemically synthesized. Said linkage of the glycan compound to the lipid can be mediated by a phosphate, a pyrophosphate linker or by a glycosidic linkage. Examples of lipids (with various chain lengths, saturation grade and configuration) linked to N-glycans were described (Faridmoayer et al., Journal of Biological Chemistry, 2009; Chen M M et al., Biochemistry, 2007). Lipid-linked N-glycan compounds produced in the native host or in a heterologous expression system include undecaprenyl-phosphate-linked N-glycan compounds as shown for the C. jejuni N-glycan (Reid C W et al., Analytical Chemistry, 2008, Reid C W et al., Analytical Chemistry, 2009) and proposed for the C. lari N-glycan (Schwarz F et al., Glycobiology 2011)) and N-glycan-LipidA conjugates (shown for the N-glycan of C. jejuni (van Sorge N M et al., Cellular Microbiology, 2009)).
It has been determined that the above compound is substantially conserved across multiple species of Campylobacter.
Campylobacter
C. jejuni
C. coli
C. upsaliensis
C. fetus fetus
C. fetus
venerealis
C. concisus
C. hyointestinalis
Table 1. fOS and N-glycan structure masses determined by mass spectrometry in select Campylobacter strains. Numbers indicate the mass(es) of Formula 1A and Formula 1B either as free oligosaccharide (fOS) or Asn-linked. Masses were obtained in positive ion mode from whole cell lysates of the indicated strain. The structures of Formula 1A and Formula 1B were determined by NMR as shown in
Campylobacter jejuni 11168, C. concisus, C. hyointestinalis, C. fetus fetus and C. fetus venerealis were grown under microaerophilic conditions. Whole cells obtained after centrifugation were digested with large excess of proteinase K at pH 8 (adjusted by addition of ammonia) at 37° C. for 48 hours. Products of digestion or free oligosaccharides were separated on Sephadex G-15 column (1.5×60 cm) and each fraction eluted before the salt peak was dried and analyzed by 1H NMR. Fractions containing desired products were separated by anion exchange chromatography on a Hitrap Q column (5 mL size, Amersham) and the glycans were eluted with a linear gradient of NaCl-(0-1 M, 1 h) that resulted in the isolation of a mixture of both glycan compounds (Formula 1A and Formula 1B). Desalting was performed on Sephadex G15 prior to analysis by NMR.
NMR experiments on the glycans obtained in example 1 were carried out on a Varian INOVA 500 MHz (1H) spectrometer with 3 mm gradient probe at 25° C. with acetone internal reference (2.225 ppm for 1H and 31.45 ppm for 13C) using standard pulse sequences DQCOSY, TOCSY (mixing time 120 ms), ROESY (mixing time 500 ms), HSQC and HMBC (100 ms long range transfer delay). AQ time was kept at 0.8-1 sec for H—H correlations and 0.25 sec for HSQC, 256 increments was acquired for t1. The Results are shown in
The campylobacter glycans that are either added to protein or appear in a free form (fOS) can be divided into two structural groups. The first group produces a unique glycan structure that was previously determined for C. jejuni and C. coli and herein for C. upsaliensis. Campylobacters which fall into the second group consist of Campylobacter fetus venerealis (cause of venereal disease and infertility in cattle), Campylobacter fetus fetus (cause of sheep abortions), Campylobacter concisus and Campylobacter hyointestinalis.
Structure determination by NMR using large scale purified free oligosaccharides (fOS) from C. fetus fetus, C. fetus venerealis, and C. concisus demonstrated that this second group of campylobacters produced a structure different from that originally described for C. jejuni and C. coli (
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
Table 2: Chemical shifts δ (ppm) for the purified free oligosaccharides (Formula 1A and Formula 1B) from C. fetus fetus (for the spectrum shown in
A Pronase E digest of whole cell extracts obtained after lysis of intact cells followed by mass spectrometry as described by Liu X. et al., Anal Chem, 2005 and Nothaft H. et al., Methods Mol Biol, 2010 identified the C. jejuni heptasaccharide (structure 1) attached to a single asparagine and Formula 1A linked to a single asparagine in C. fetus fetus.
The protein glycosylation operon encoding all the genes necessary for the production and transfer of Formula 1A and Formula 1B compounds can be cloned and expressed from an E. coli plasmid(s). Alternatively, the glycosyltransferases on a plasmid described by Wacker et al, Science 2002 that contains the C. jejuni protein glycosylation (pgl) operon can be exchanged by Formula 1A and Formula 1B producing glycosyltransferases. Expression of Formula 1A and Formula 1B compounds can be done in a heterologous system in the presence of an affinity-tagged acceptor peptide for N-linked protein glycosylation (already shown for the C. jejuni N-glycan and for the C. lari N-glycan Wacker et al., Science 2002, Schwarz et al., Glycobiology 2011). The glycan containing protein/peptide can be purified by affinity-tag purification, if necessary in combination with lectin or glycan-recognizing agent affinity chromatography to separate the glycosylated and the non-glycosylated peptides.
Purified Formula 1A and Formula 1B fOS were separated by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC/PAD).
Purified and neutralized Formula 1A and 1B compounds prepared in Example 5 were conjugated to BSA by reductive amination (see Gildersleeve J C., Bioconjug Chem. 2008). A mixture of Bovine serum albumin (BSA; 2 μL of a 150 mg/mL solution; fraction V), sodium borate (5.5 μL of a 400 mM solution, pH 8.5), sodium sulfate (3.7 μL of a 3 M solution, 50° C.), oligosaccharide (Formula 1A or Formula 1B) (7.0 μL of 20 mM solution for 15 eq), H2O (1.4 μL) and sodium cyanoborohydride (2.2 μL of a 3 M solution) was incubated in a 200 μL PCR tube in a PCR thermal cycler at 56° C. for 96 h with a heated lid. The reaction was diluted with H2O to a final volume of 100 μL, transferred to a 500 μl dialysis tube (MWCO 10,000) and dialyzed three times against H2O (2.51).
New Zealand White Rabbits were immunized with 2 mg of each of the glyco-conjugate compounds prepared in Example 6, using a 6 week immunization protocol (according to the animal care committee protocol No. 717). After an initial subcutaneous injection (at 3 sites, 0.5 ml were injected at each site) of 2.0 mg using Freund's complete adjuvant (in a 1:1 ratio with the antigen), a booster dose with 2.0 mg mg of each Formula 1A and Formula 1B-BSA conjugates mixed with Freund's incomplete adjuvant (in a 1:1 ratio with the antigen) was given subcutaneously (at 3 sites 0.5 ml were injected at each site) after 4 weeks. After 6 weeks serum from a 5 ml blood sample from each animal was prepared by cooling the blood sample for 60 min on ice followed by centrifugation for 20 min at 10.000×g. Individual sera were analyzed for the production of Formula 1A and Formula 1B-specific antibodies by Western Blotting with Campylobacter whole cell lysates (
Cells were grown in MH broth under microaerobic conditions, harvested by centrifugation and washed twice in 50 mM Tris-HCl, pH 7.2. Pellets were freeze dried and placed in 1.5 ml Lobind tubes (Eppendorf). Pellets (10 mg) were resuspended in 1 ml ice-cold Tris-HCl (pH 7.5) in the presence of 150 units of Benozanase, vortexed to resuspend and kept on ice. After sonication (6 times 30 seconds with 1 minute on ice between) the cellular debris was removed by centrifugation at 20,000×g for 30 minutes at 4° C. The supernatant was collected in LoBind (Eppendorf) tubes and freeze dried. Sample processing, glycopeptide enrichment and mass spectrometry were applied as described (Scott N E, et al Molecular and Cellular Proteomics, 2010). Formula 1A and Formula 1B N-linked to asparagines located in polypeptides derived from proteolytic digested cell lysates were identified for C. fetus fetus, C. fetus venerealis and C. concisus (Table 3).
Glycopeptides were isolated and identified from Campylobacter fetus fetus, Campylobacter fetus venerealis, and Campylobacter concisus with the results shown in Table 3. The glycan portions there of all comprised the compound of Formula 1A or 1B.
C. fetus
venerealis
List of proteins identified to be N-linked with Formula 1A and Formula 1B. The single peak areas for Formula 1A and Formula 1B were determined by multiple reaction monitoring (MRM) mass spectrometry.
9A) MS spectrum (precursor ion scan) of tryptic digested, HILIC-LC enriched peptides; (9B) Quantification of relative peak areas of the corresponding ions; (9C) MS/MS of the carbohydrate portion, (9D) MS/MS of the peptide portion of the m/z ion 968.44545; 9E) MS/MS of the carbohydrate portion, and 9F) MS/MS of the peptide portion of the m/z ion 982.12069.
Cells of C. fetus fetus, C. fetus venerealis, C. concisus, C. hyointestinalis, and C. jejuni were grown on MH plates for 18-24 hours under microaerophilic conditions. Cells were harvested from the plate with 2 ml MH broth, cooled on ice for 10 min, centrifuged for 5 min at 6,000×g. Cells were kept on ice for all further labeling and washing steps using pre-cooled (4° C.) solutions. Cells were washed twice with 2 ml washing buffer (50 mM potassium phosphate, 100 mM NaCl). To prevent unspecific binding cells were blocked with 1% Skim Milk in washing buffer for 30 min. Primary antibody (1:1,000 dilution in washing buffer with 0.5% Skim) was applied for 30 min. Cells were washed 3 times with 2 ml Washing buffer. Fluorescent labeled secondary antibody (anti-Rabbit-IgG-Alexa-Flour546, diluted 1:100 in washing buffer with 0.5% Skim Milk) was applied for 30 min and cells were washed 4-times in washing buffer. Cell surface labeling was monitored using a Leica DMRXA Upright Microscope equipped with an Optronics MacroFire Digital Camera (LM-MFCCD). Each picture was taken under identical software settings. C. jejuni that produces structure 1 served as a negative control.
The glycan compounds (Formula 1A and Formula 1B) can be attached to various glycan carriers (peptides, lipids). The resulting compounds can be used to stimulate an immune-response against the respective structure that will be protective against infection with Formula 1A and Formula 1B presenting bacterial species.
Generated antisera/antibodies can be used (when i.e immobilized on a surface) as a diagnostic to detect e.g. C. fetus venerealis or C. fetus fetus in infected livestock (especially C. fetus venerealis cattle) or to detect human pathogenic Campylobacter strains (e.g C. concisus, C. hyointestinalis, C. ureolyticus).
The compounds of the present invention can be used to immunize animals, in particular livestock, against C. fetus venerealis, C. fetus fetus, and other Campylobacter species in which the glycan described herein is native to the organism. Immunization can take the form of treating or preventing disease in individual animals or on a herd-wide basis for improved productivity and health of the herd.
To the extent that Campylobacter species in which the glycan of Formula 1 is native to the organism, the compounds described herein can be used in a similar fashion to the above for preparing vaccines to treat or prevent infection by such organisms within humans. As well, a similar diagnostic function can be obtained in humans, using the antibodies or antisera raised against such compounds.
The present invention has been described by way of various embodiments thereof. It will be understood by persons skilled in the art that the invention is not limited in scope to such embodiments. Rather, the full scope of the invention encompasses and may be appreciated by reference to this patent specification in its entirety, including the claims thereof, and including modifications, variations, and alternative embodiments that would be understood to the skilled person based on said specification.
This application is the U.S. National Stage filing under 35 U.S.C. §371 of International Application No. PCT/CA2011/050084, filed on Feb. 11, 2011, which claims benefit of U.S. Provisional Application No. 61/303,411, filed on Feb. 11, 2010, each of which is hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2011/050084 | 2/11/2011 | WO | 00 | 10/19/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 20130034556 A1 | Feb 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61303411 | Feb 2010 | US |
