Patent Application
20210293828
The present invention relates to antibodies which are reactive with fragments of collagen type VII alpha 1 comprising an N- or C-terminal neo-epitope, the use of said antibodies in an assay for detecting and quantifying said fragments of collagen type VII alpha 1, and the use of said assay for evaluating chronic obstructive pulmonary disease (COPD) or systemic sclerosis.
Collagen type VII is the main component of the anchoring fibrils that connects the basement membrane to the underlying interstitial matrix. It consists of three identical alpha-1 chains with two non-collagenous (NC) domains and a central collagenous triple helical domain. It has been identified in the basement membranes of skin and mucous membranes [1].
Collagen type VII has mainly been investigated for its role in dystrophic epidermolysis bullosa, a severe skin disease. Mutations in the collagen type VII alpha-1 chain leads to the formation of abnormal, diminished or absent anchoring fibrils which causes separation of epidermis from dermis and thus skin blistering [1]. Collagen type VII has also been identified as the protein at fault in epidermolysis bullosa acquisita, an autoimmune disease causing blistering of the skin and mucous membranes. It is caused by IgG autoantibodies directed at the collagen type VII NC1 domain [2].
Autoimmunity to collagen type VII has also been associated with inflammatory bowel disease and bullous systemic lupus erythematosus [3-4].
An up-regulation of collagen type VII level in the skin of patients suffering from systemic sclerosis has been identified [5]. Patients with systemic sclerosis have skin fibrosis and may present with fibrosis of internal organs including the lungs. One study has also identified a reduced level of collagen type VII protein in the anchoring fibrils in the airways in a monkey model of asthma [6].
In order to evaluate a pathogenic condition linked to collagen type VII it is necessary to produce assays capable of detecting and quantifying species related to the pathogenic condition.
Chen et al., Saleh et al. and Kim et al. independently developed ELISAs for detecting autoantibodies against the NC1 or NC2 domain of collagen type VII [7-9]. The methods comprise coating a microtiter plate with recombinant NC1 and/or NC2 domain of collagen type VII alpha-1, adding serum samples of interest, and using anti-human IgG antibody to detect autoantibodies present in the serum sample.
Recke et al. describes the generation of autoantibodies against the collagen type VII NC1 domain and investigated the pathogenic potential in human ex vivo models of epidermolysis bullosa acquisita [10]. They proposed the use of this as a diagnostic tool.
Sakai et al. raised a monoclonal antibody against collagen type VII [11]. The mAb was reactive only with intact collagen type VII.
Monoclonal and polyclonal antibodies targeting collagen type VII can be obtained commercially from several vendors.
It has now been found that fragments of collagen type VII alpha 1 are detectable in circulation and could serve as potential biomarkers for evaluating pathological conditions linked to collagen type VII. Specifically, a link between collagen type VII alpha 1 fragments and the pathological conditions COPD and systemic sclerosis has been identified.
Accordingly, in a first aspect the present invention relates to an antibody reactive with a fragment of collagen type VII alpha 1 comprising an N- or C-terminal neo-epitope, wherein said antibody binds to the N- or C-terminal neo-epitope.
The antibody is preferably a monoclonal antibody, but may also be a polyclonal antibody or an antibody fragment exhibiting the desired biological activity.
Preferably, the antibody does not recognise or bind intact collagen type VII alpha 1.
In a preferred embodiment, the antibody may bind to an N- or C-terminal neo-epitope comprised in a non-collagenous amino-terminal domain of collagen type VII alpha 1 (NC1) or comprised in a central collagenous domain of collagen type VII alpha 1.
In another preferred embodiment, the antibody may bind to a C-terminal neo-epitope comprised in the central collagenous domain of collagen type VII alpha 1. Preferably, the antibody binds to a C-terminal neo-epitope comprised in the amino acid sequence GPPGPPGRLV-COOH (SEQ ID NO: 1). Preferably, the antibody binds to a C-terminal neo-epitope comprising or consisting of the amino acid sequence PPGRLV-COOH (SEQ ID NO: 2). This C-terminal neo-epitope may be formed by cleavage of human collagen type VII alpha 1 at the Val-Asp bond between amino acids V1709-D1710 in the central collagenous domain of collagen type VII alpha 1. Preferably, the antibody does not recognise or bind elongated amino acid sequence GPPGPPGRLVX-COOH (SEQ ID NO: 3), wherein X is one or more amino acids of the sequence of collagen type VII alpha 1.
In another preferred embodiment, the antibody may bind to an N-terminal neo-epitope comprised in the non-collagenous amino-terminal domain of collagen type VII alpha 1 (NC1). Preferably, the antibody may bind to an N-terminal neo-epitope comprised in the amino acid sequence H2N-EAPRVRAQHR (SEQ ID NO: 4). Preferably, the antibody binds to an N-terminal neo-epitope comprising or consisting of the amino acid sequence H2N-EAPRVR (SEQ ID NO: 5). This N-terminal neo-epitope may be formed by cleavage of human collagen type VII alpha 1 at the Ala-Glu bond between amino acids A16-E17 in the non-collagenous amino-terminal domain of collagen type VII alpha 1. Preferably, the antibody does not recognise or bind elongated amino acid sequence H2N-XEAPRVRAQHR (SEQ ID NO: 6), wherein X is one or more amino acids of the sequence of collagen type VII alpha 1.
Antibodies described herein may be raised against a synthetic peptide corresponding to the N- or C-terminal neo-epitope amino acid sequence.
In a second aspect the present invention relates to a method of immunoassay for detecting in a biological sample a fragment of collagen type VII alpha 1 comprising an N- or C-terminal neo-epitope, said method comprising contacting said biological sample comprising said fragment of collagen type VII alpha 1 comprising said N- or C-terminal neo-epitope with an antibody as described herein, and determining the amount of binding of said antibody.
The method may be used to quantify the amount of the fragment of collagen type VII alpha 1 comprising said N- or C-terminal neo-epitope in biofluids. The biofluid may be, but is not limited to, serum, plasma, bronchoalveolar lavage fluid, sputum, saliva, exhaled breath or urine.
The immunoassay may be, but is not limited to, a competition assay or a sandwich assay. The immunoassay may be, but is not limited to, a radioimmunoassay or an enzyme-linked immunosorbent assay.
The method may further comprise the step of correlating the quantity of the fragment of collagen type VII alpha 1 comprising an N- or C-terminal neo-epitope determined by said method with standard collagen type VII related disease samples of known disease severity to evaluate the severity of a collagen type VII related disease.
Such collagen type VII related diseases may be, but are not limited to, chronic obstructive pulmonary disease (COPD) or systemic sclerosis.
It is envisaged that the method of the invention may be utilised in the quantitation, diagnosis and/or prognosis of such collagen type VII related diseases.
In a third aspect the present invention relates to a peptide, wherein the peptide has an N-terminal amino acid sequence corresponding to an amino acid sequence of an N-terminal neo-epitope of a fragment of collagen type VII alpha 1 comprising said N-terminal neo-epitope, or wherein the peptide has a C-terminal amino acid sequence corresponding to an amino acid sequence of an C-terminal neo-epitope of a fragment of collagen type VII alpha 1 comprising said C-terminal neo-epitope. Preferably, the peptide is ten amino acid residues in length, more preferably nine amino acid residues, more preferably eight amino acid residues, more preferably seven amino acid residues, and most preferably six amino acid residues in length. The peptide may be biotinylated.
In a preferred embodiment, the peptide has the amino acid sequence EAPRVRAQHR (SEQ ID NO: 4) or EAPRVR (SEQ ID NO: 5).
In another preferred embodiment, the peptide has the amino acid sequence GPPGPPGRLV (SEQ ID NO: 1) or PPGRLV (SEQ ID NO: 2).
In a fourth aspect the present invention relates to an assay kit for determining the quantity of a fragment of collagen type VII alpha 1 comprising an N- or C-terminal neo-epitope in a biological sample, the kit comprising an antibody as described herein and at least one of:
Preferably, the assay kit comprises a biotinylated peptide Biotin-L-GPPGPPGRLV (SEQ ID NO: 7), wherein L is an optional linker, and a calibrator peptide comprising the C-terminal sequence GPPGPPGRLV-COOH (SEQ ID NO: 1).
Preferably, the assay kit comprises a biotinylated peptide EAPRVRAQHR-L-Biotin (SEQ ID NO: 8), wherein L is an optional linker, and a calibrator peptide comprising the N-terminal sequence H2N-EAPRVRAQHR (SEQ ID NO: 4).
The term “antibody” is used according to the invention in the broadest sense and specifically covers intact monoclonal antibodies, polyclonal antibodies, and antibody fragments, so long as they exhibit the desired biological activity.
“Antibody fragments” according to the invention comprise a portion of an intact antibody, preferably comprising the antigen-binding or variable region thereof. Examples of antibody fragments include Fab, Fab′, F(ab′)2, Fv and Fc fragments.
“A fragment of Collagen type VII alpha 1” according to the invention means a peptide fragment produced by protease cleavage of collagen type VII.
“N- or C-terminal neo-epitope” according to the invention means an N- or C-terminal epitope formed at a protease cleavage site of Collagen type VII alpha 1. For example, the following sequence of Collagen type VII alpha 1
“C7” as used herein refers to fragments of collagen type VII alpha 1 comprising the C-terminal neo-epitope GPPGPPGRLV-COOH (SEQ ID NO: 1).
“NB677” as used herein refers to fragments of collagen type VII alpha 1 comprising the N-terminal neo-epitope H2N-EAPRVRAQHR (SEQ ID NO: 4).
Mass spectrometry was performed on serum samples from a patient with COPD, a patient with idiopathic pulmonary fibrosis (IPF), and a healthy donor.
The initial mass spectrometry analyses identified peptides derived from collagen type VII in serum. Peptides were isolated from serum using IMAC Cu beads. Identity significance threshold for individual peptides were 51. Serum samples were analyzed using an orbitrap (OrbiB) instrument.
Fragments of collagen type VII alpha 1 comprising the C-terminal neo-epitope GPPGPPGRLV-COOH (“C7”) (SEQ ID NO: 1) were found in the COPD sample but not in the IPF or healthy donor samples. The neo-epitope corresponds to the cleavage site located between amino acids Val-Asp at positions 1709-1710 of human collagen type VII. The protease responsible for this cleavage is as yet unknown. The sequence was analyzed using BLAST and was found to be unique for the collagen type VII alpha-1 chain.
A monoclonal antibody was raised against the C-terminal neo-epitope amino acid sequence GPPGPPGRLV-COOH (SEQ ID NO: 1).
Briefly, four to six-week-old Balb/C mice were immunized subcutaneously with 200 μL emulsified antigen and 50 μg of a C7 synthetic peptide (KLH-CGG-GPPGPPGRLV, SEQ ID NO: 9) using Freund's incomplete adjuvant. Immunizations were performed every 2nd week until stable sera titer levels were reached. The mouse with highest serum titer was selected for fusion. The mouse was rested for one month and then boosted intravenously with 50 μg C7 peptide in 100 μL 0.9% sodium chloride solution three days before isolation of the spleen for cell fusion. Mouse spleen cells were fused with SP2/0 myeloma fusion partner cells. The resulting hybridoma cells were cloned using a semi-solid medium method, transferred into 96-well microtiter plates for further growth and incubated in a CO2 incubator. Standard limited dilution was used to promote monoclonal growth.
A competitive ELISA using the monoclonal antibody raised against C7 was performed using the following procedure:
Streptavidin-coated plates were coated with 100 μL/well of 2.5 ng/mL biotin-labeled peptide (Biotin-KKGPPGPPGRLV, SEQ ID NO: 10) diluted in assay buffer (50 mM TBS-BTB, 2 g/L NaCl, pH 8.0) and incubated at 20° C., 300 rpm shaking for 30 minutes. Plates were washed five times in washing buffer (20 nM TRIS, 50 mM NaCl, pH 7.2). Sample or standard peptide (20 μL) was added in double determinations and followed immediately by addition of 100 μL/well of 200 ng/mL HRP-labeled monoclonal antibody diluted in assay buffer and plates were incubated at 20° C., 300 rpm shaking for 3 hours. The standard peptide was a synthetic peptide (GPPGPPGRLV, SEQ ID NO: 1) with a starting concentration of 125 ng/mL and diluted 2-fold to create an 11 points calibration curve (
The technical characteristics of the C7 ELISA are as follows:
The ELISA was shown to be specific for the cleavage site as reactivity was seen towards the standard peptide but not to an elongated peptide (GPPGPPGRLVD, SEQ ID NO: 11), indicating that the assay does not recognize intact collagen type VII protein (
Serum levels of C7 were significantly elevated in a cohort of 68 patients with COPD when compared to healthy donors (
These results show the utility of the C7 assay in identifying COPD, and may prove useful in evaluating COPD, for example as a diagnostic or prognostic tool.
Serum levels of C7 were significantly elevated in 20 patients with early diffuse systemic sclerosis when compared to healthy control (p=0.022) (
The elevated level of C7 in early stage systemic sclerosis when compared to late stage systemic sclerosis suggests that the C7 assay may be capable of differentiating between early and late stages of systemic sclerosis, thereby providing a potentially useful diagnostic and/or prognostic tool for evaluating systemic sclerosis.
The signal peptide in collagen type VII alpha-1 is found at amino acids 1-16 [12]. The N-terminal neo-epitope sequence that is formed by cleavage of the signal peptide (17‘.EAPRVRAQHR’26) was analyzed using BLAST and was found to be unique for the collagen type VII alpha-1 chain.
Following the success of the “C7” assay for COPD, it is postulated that this unique collagen type VII alpha-1 neo-epitope may also be useful in the identification and/or evaluation of COPD and/or systemic sclerosis.
Accordingly, a monoclonal antibody was raised against the N-terminal neo-epitope amino acid sequence H2N-EAPRVRAQHR (SEQ ID NO: 4).
Briefly, four to six-week-old Balb/C mice were immunized subcutaneously with 200 μL emulsified antigen and 50 μg of a NB677 synthetic peptide (EAPRVRAQHR-GGC-KLH, SEQ ID NO: 12) using Freund's incomplete adjuvant. Immunizations were performed every 2nd week until stable sera titer levels were reached. The mouse with highest serum titer was selected for fusion. The mouse was rested for one month and then boosted intravenously with 50 μg NB677 peptide in 100 μL 0.9% sodium chloride solution three days before isolation of the spleen for cell fusion. Mouse spleen cells were fused with SP2/0 myeloma fusion partner cells. The resulting hybridoma cells were cloned using a semi-solid medium method, transferred into 96-well microtiter plates for further growth and incubated in a CO2 incubator. Standard limited dilution was used to promote monoclonal growth.
A competitive ELISA using the monoclonal antibody was performed using the following procedure:
Streptavidin-coated plates were coated with 100 μL/well of 2.0 ng/mL biotin-labeled peptide (EAPRVRAQHR-Lys-Biotin, SEQ ID NO: 13) diluted in coating buffer (50 mM PBS-BTE, 8 g/L NaCl, 10% sorbitol) and incubated at 20° C., 300 rpm shaking for 30 minutes. Plates were washed five times in washing buffer (20 nM TRIS, 50 mM NaCl, pH 7.2). Standard peptide (20 μL) was added in double determinations and followed immediately by addition of 100 μL/well of 120 ng/mL monoclonal antibody diluted in assay buffer (25 mM PBS-BTB, 8 g/L NaCl) and plates were incubated at 4° C., 300 rpm shaking for 20 hours. The standard peptide was a synthetic peptide (EAPRVRAQHR, SEQ ID NO: 4) with a starting concentration of 100 ng/mL and diluted 2-fold to create a calibration curve (
The C7 ELISA was evaluated in a second, larger cohort of patients with systemic sclerosis (SSc). The C7 ELISA was re-calibrated (compared to the previous example) to improve accuracy of the assessments in human serum.
Results:
The biological relevance of the C7 ELISA was evaluated by comparing serum levels in healthy donors (n=70) with patients with SSc (n=119). Data are shown in
The clinical data support that serum C7 levels are elevated in patients with SSc
In conclusion, the novel assays described herein utilise antibodies specific for an N- or C-terminal neo-epitope of collagen VII alpha 1. To the best of our knowledge, this is the first time that collagen type VII has been associated with COPD. Accordingly, it is envisaged that these assays may be used for assessing COPD as well as systemic sclerosis.
In this specification, unless expressly otherwise indicated, the word ‘or’ is used in the sense of an operator that returns a true value when either or both of the stated conditions is met, as opposed to the operator ‘exclusive or’ which requires that only one of the conditions is met. The word ‘comprising’ is used in the sense of ‘including’ rather than in to mean ‘consisting of’. All prior teachings acknowledged above are hereby incorporated by reference. No acknowledgement of any prior published document herein should be taken to be an admission or representation that the teaching thereof was common general knowledge in Australia or elsewhere at the date hereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1601571.1 | Jan 2016 | GB | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16072648 | Jul 2018 | US |
| Child | 17339317 | US |
