Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K7/00—Peptides having 5 to 20 amino acids in a fully defined sequence; Derivatives thereof
  • C07K7/04—Linear peptides containing only normal peptide links
  • C07K7/06—Linear peptides containing only normal peptide links having 5 to 11 amino acids
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
  • C07K14/46—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates
  • C07K14/47—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates from mammals
  • C07K14/4701—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates from mammals not used
  • C07K14/4715—Pregnancy proteins, e.g. placenta proteins, alpha-feto-protein, pregnancy specific beta glycoprotein
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/68—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids
  • G01N33/689—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids related to pregnancy or the gonads
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
  • G01N2333/435—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans
  • G01N2333/705—Assays involving receptors, cell surface antigens or cell surface determinants
  • G01N2333/70503—Immunoglobulin superfamily, e.g. VCAMs, PECAM, LFA-3
  • G01N2333/70507—C2D

Definitions

• the present invention relates to preimplantation factor ("PIF") a very early marker of fertilization and embryo viability, to new methods for detecting PIF activity and to PIF peptides.
• PIF preimplantation factor
• In vitro fertilization is a technology which has been developed to address the problem of infertility.
• maintaining embryo viability is even more problematic under the artificial conditions used for culturing embryos in vitro for implantation.
• the embryo development rate is lower than in vivo and only 25-65 % of embryos typically develop to the blastocyst stage (Gardner DK, Lane M, KOuridakis K, Schoolvcraft WB.
• Complex physiologically based serum-free culture media increase mammalian embryo development.
• the state of the art is not yet able to identifying embryos likely to implant and survive.
• hCG Human chorionic gonadotrophin
• Another factor involved in determining whether a pregnancy is successful or not is the interaction between the conceptus and the mother's immune system. Shortly after fertilization a systemic maternal recognition of pregnancy should occur. The mother's immune system modulation triggered by specific early embryo signals could be the key of this process. Once the oocyte is fertilized, the zygote up to hatching blastocyst is surrounded by the zona pellucida, a hard semi permeable membrane. Therefore the embryo-maternal communication must occur simultaneously while the embryo is developing in the oviduct and uterine cavity through compounds that are secreted by the embryo.
• PIF Preimplantation Factor
• PIF has been found to be (i) secreted by viable early human and mouse embryos from the two- cell stage onward; detectable in the peripheral circulation 3-4 days after embryo transfer following IVF; (iii) associated with 73% take home babies vs 3 % in early negative PIF results; (iv) detectable 5-6 days after intrauterine insemination; (v) absent in non- pregnant serum, or non- viable embryos; and (vi) present in various pregnant mammals in addition to humans, including mice, horses, cows and pigs. In addition, PIF has been observed to disappear from the circulation two weeks before hCG secretion declines in cases of spontaneous abortion.
• CD2 lymphocyte associated antigen
• CD2 is present on about 80-90% of human peripheral blood lymphocytes, greater than 95% of thymocytes, all T lymphocytes that form erythrocyte rosettes and a subset of NK cells.
• Various roles for CD2 in T cell activation have been proposed, including function as an adhesion molecule which reduces the amount of antigen required for T cell activation and as a costimulatory molecule or direct promoter of T cell activation .
• CD2 has been implicated in the induction of anergy, the modulation of cytokine production and the regulation of positive selection of T-cells .
• CD2 The natural ligand for CD2 is the structurally related IgSF CAMs CD58 (LFA-3), a cell-surface adhesive ligand with broad tissue distribution, i addition, CD2 can interact with CD48, CD59 and CD 15 (Lewis x)-associated carbohydrate structure.
• CD2 binds CD58 with very low affinity and an extremely fast dissociation constant
• the lateral redistribution of CD2 and its ligand CD58 also affect cellular adhesion strength .
• Regulation of CD2 adhesiveness affects the ability of CD2 to enhance antigen responsiveness.
• CD2-cell lines incapable of avidity regulation exhibit a marked deficiency in an antigen-specific response. Strength of adhesion resulting from increased CD2 avidity contributes directly to T-cell responsiveness independently of CD2-mediated signal transduction.
• the present invention relates to assay methods used for detecting the presence of PIF, and to PIF peptides identified using this assay.
• the present invention relates to flow cytometry assays for detecting PIF. It is based, at least in part, on the observation that flow cytometry using fluorescently labeled anti- lymphocyte and anti-platelet antibodies demonstrated an increase in rosette formation in the presence of PIF. It is further based on the observation that flow cytometry demonstrated that monoclonal antibody binding to CD2 decreased in the presence of PIF.
• the present invention further relates to PIF peptides which, when added to Jurkat cell cultures, have been observed to either (i) decrease binding of anti- CD2 antibody to Jurkat cells; (ii) increase expression of CD2 in Jurkat cells; or (iii) decrease Jurkat cell viability.
• the present invention provides for ELISA assays which detect PIF by determining the effect of a test sample on the binding of anti-CD2 antibody to a CD2 substrate.
• FIGURE 1 A-B PIF purification from mouse embryo culture conditioned medium (MECCM);
• A shows a high performance liquid chromatography ("HPLC") profile of MECCM-3kDA ultra-filtrate previously purified by MabCD2 affinity chromatography;
• B shows the profile following additional HPLC purification of a PIF-active fraction from (A).
• HPLC high performance liquid chromatography
• FIGURE 2A-C Western blot analysis of different PIF peptides purified from MECCM; MabCD2 was used as a primary antibody and anti-sense mouse horseradish peroxidase (HRP)-biotin streptavidin complex was used as secondary antibody. Specific PIF bands were identified by the ECL detection reagents (Amersham Pharmacia Biotech).
• FIGURE 3A-C shows flow cytometric determination of lymphocyte-platelet rosette formation (L-P) in the presence of fresh culture medium (CM) and mouse embryo culture conditioned medium (MECCM) and MabCD2. Fluorescent labeled specific antibodies to L (MabCD45-PE) and to P (MabCD42a- FITC) were used to detect the L-P complex. MECCM gave 30-40 percent higher formation of L-P compared to culture medium (CM).
• B shows FC of MECCM effect on MabCD2 binding to Jurkat cells (JC). JC were incubated with samples and further with MabCD2 Cy5. Antibody binding to CD2 decreased by PIF present in MECCM. Arrows indicate PIF activity.
• FIGURE 4A-C Mass spectrum from PIF peptides purified from MECCM.
• Molecular weight (MW) of PIF-active fractions from MECCM purified by ultrafiltration, diafiltration, HPLC, MabCD2-affmity chromatography and by additional HPLC was determined by mass spectroscopy. MW of PIF peptides were A) 610-995 Da; B) 963-1848 Da; and C) 1807-1846 Da.
• FIGURE 5A-F Flow cytometric analysis of PIF negative effects on MabCD2 binding (A), fluorescence (B) and viability (C) in Jurkat cells, and of PIF positive effects on MabCD2 binding (D), fluorescence (E) and viability (F). PIF in positive samples competes with CD2 (arrows indicate PIF activity).
• FIGURE 6 Effect of Synthetic PIF peptides on CD2 expression on Jurkat cells.
• the present invention provides for a method for determining the presence of preimplantation factor in a sample, comprising the step of detecting whether the sample contains a component which inhibits the binding of an anti-CD2 antibody to CD2 antigen; wherein the ability to inhibit the binding of anti-CD2 antibody to CD2 has a positive correlation with the presence of preimplantation factor.
• Such a method may, for example, be employed in a flow cytometry method or in an enzyme-linked immunosorbent assay method, using techniques otherwise known in the art.
• a non-limiting example of a flow cytometry method for detecting anti-CD2 antibody binding to CD2 is presented in Section 7, below.
• An anti-CD2 antibody may be a monoclonal or polyclonal antibody which specifically binds to CD2.
• a monoclonal antibody is sold by Pharmigen (see below).
• CD2 antigen may be in the form of purified CD2 antigen or may be carried by a cell.
• the cell is a Jurkat cell.
• Other CD2-expressing cell lines are known in the art.
• the sample may be a serum sample (for example, serum from a subject to be tested for fertilization/implantation/persistence of embryo), maybe a sample of culture fluid (for example, to determine the viability of embryos prior to transfer for IVF), or may be a solution to be tested for the presence of a PIF peptide (for example, during the purification of PIF acting agents; see Section 6, below).
• a serum sample for example, serum from a subject to be tested for fertilization/implantation/persistence of embryo
• a sample of culture fluid for example, to determine the viability of embryos prior to transfer for IVF
• a PIF peptide for example, during the purification of PIF acting agents; see Section 6, below.
• the subject maybe a human subject (for example, a human suspected of being pregnant) or a non-human subject (for example an agricultural animal or a zoo animal).
• a human subject for example, a human suspected of being pregnant
• a non-human subject for example an agricultural animal or a zoo animal
• the present invention provides for a method for determining the presence of preimplantation factor in a sample, comprising the step of detecting, by flow cytometry, whether the sample contains a component which increases the formation of rosettes between lymphocytes, platelets, and anti-CD2 antibodies, where an increase in rosette formation has a positive correlation with the presence of preimplantation factor.
• a assay may be performed, for example, using fluorescently labeled antibodies directed toward lymphocytes and platelets, where preferably different labels are used for anti-platelet and anti-lymphocyte antibodies. The increase is relative to a known negative control.
• the present invention also provides for the following isolated peptides:
• EXAMPLE IDENTIFICATION OF PIF PEPTIDES
• PIF was isolated from a large volume of MECCM using ultra filtration, lyophilization, high performance chromatography (HPLC), affinity chromatography and western blot.
• HPLC high performance chromatography
• Two-cell-to blastocyst stage mouse embryos were cultured for several days in Ham's F-10 medium with penicillin, streptomycin, MgSO , NaHCO 3 , KHCO 3 , and Ca lactate supplemented with 0.1 % BSA.
• MECCM collected was stored at -80°C until used.
• MECCM One liter of MECCM was purified by ultra filtration through an Amicon membrane (3 kDa cut-off; YM- 3 Da, Amicon. Millipore Co, USA). Concentrated MECCM was further diafiltered using 300 ml of pure water. In addition, fresh culture media (CM, without embryos) was processed in the same way. Only MECCM-3kDa ultra filtrate and diafiltrated demonstrated PIF activity and then they were pooled and concentrated by lyophilization.
• MabCD2 (clone RPA- 2.10, Pharmigen, Becton Dickinson) was buffer exchanged with the coupling buffer pH 5.5 using the Econo-Pac 10DG desalting column provided and further oxidized with sodium periodate and coupled to 2 ml of agarose-hydrazide activated gel following the manufacturer's indications (Affi-gel Hidrazide immunoaffinity kit, BioRad Laboratories, CA, USA). Then, MECCM-3kDa ultra filtrate-diafiltrate lyophilized powder was further purified using the MabCD2-affinity chromatography column (10 x 20 mm).
• CM ultra filtrate- lyophilize fraction was used as negative control in WB.
• the WB conditions were as follows. For gels, SDS-PAGE pre-casting gels (BioRad) were used, having a 16.5% agarose resolving gel and a 4% agarose stacking gel. The gels were run in 100 mM Tris, lOOmM Tricine, 0.1 % SDS, pH 8.3 (Tris-tricine running buffer).
• Tricine sample buffer [200 mM Tris (hydroxymethyl) aminomethane (Tris-HCl) pH 6.8, 2 % sodium duodecyl sulphate (SDS), 40% glycerol, 0.04% Coomassie blue brilliant (CBB-G250)] (BioRad) were incubated at 95°C during 5 min. After cooling, the samples were loaded into the wells of the SDS-poryacrylamide gels (PAGE).
• MW polypeptides 10 microliters of a 1:20 water dilution of SDS- PAGE standards (BioRad) were loaded into a well of each gel. For electrophoresis, samples and standards were run at 175 v during 5min plus 60 v for 1 h.
• the resulting gels were then electro-blotted using, as transfer buffer, 100 mM CAPS [ 3-(cyclohexylamino)-l-propanesulfonic acid) buffer, pH 11. Electro- blotting was performed at 80 mA during lh onto a 0.22 ⁇ m nitrocellulose membrane (BioRad).
• nitrocellulose membranes were blocked with 5 % blocking solutions (Amersham, Pharmacia, Biotech, NJ, USA) at room temperature during 18 h., and then were washed-out 4 times during 20 min with PBS-T [phosphate saline buffer -0.05% polyoxyethylenesorbitan monolaurate (Tween 20)].
• PBS-T phosphate saline buffer -0.05% polyoxyethylenesorbitan monolaurate (Tween 20)
• blocked membranes were incubated with 2 ⁇ g/ml MabCD2 (Pharmigen) - PBS-T solutions at room temperature during 2h, and then washed as above.
• FC flow cytometric methodology
• MabCD58 lymphocyte function-associate antigen-3 or LFA-3) antibody to L-P did not prevent totally the rosette formation by effect of PIF-active samples in the assay.
• JC-PIF quantitative assay using Jurkat cells (JC) and MabCD2-Cy5 was developed (Fig 3B).
• the use of an immortalized leukemia cell line avoids the need for fresh donor blood to assess the PIF activity by the bioassay.
• the JC-FC assay was validated with human serum samples (see Table I) and was used to assess PIF activity of fractions during PIF purification.
• MW of purified PIF-active fractions was determined by mass spectral analysis on a Voyager-RP Biospectrometry MALDI-TOF Workstation from Perseptive Biosystems (Cambrigde, MA, USA). Samples were mixed with a matrix consisting in a 1:2 mixture of acetonitrile: water containing 1% trifluoroacetic acid. Spectra were averages of approximately 200 scans. PIF- peptides from MECCM have MW between 610 - 1845 Da (Fig 4).
• MEECM-PIF peptides have three different effects on CD2 expressed by T cells. These effects are related to: decreasing MabCD2 binding to the JC; up-regulating CD2 expression by JC; or decreasing JC viability.
• PIF active fractions from mouse embryos were sequenced by Edman degradation on an Applied Biosystems Pulsed Liquid Sequencer (model 477 A). Released amino acids were derivatized with phenylisothiocyanate to give the PTH-amino acids which were detected by reverse phase-HPLC on a HPLC system in line with the sequencer. Several of the PIF fractions yielded unique sequences. Several peptides gave sequences whose N-terminal nine and ten residues were identical indicating that the peptides were various truncated forms of common molecules (see Table 11). PIF peptides were identified as a least three unique families of embryo-derived and pregnancy-related small peptides.
• the amino acid sequence sequence of a family of three PIF peptides matches 100% with a region of Circumsporozoite protein (malaria parasite: Plasmodium falciparum). This family of PIF peptides up regulates the CD2 expression by JC.
• a PIF peptide (14 amino acids) that shares only the five first amino acid residues with the former described PIF- peptide's family and another PIF peptide (18 amino acids) that matches in 11 amino acids to the sequence of HJV-1 RNA directed DNA polymerase (reverse transcriptase, EC 2.7.7.49) also up regulate the CD2 expression by JC.
• PIF peptides were synthesized by solid-phase peptide synthesis (SPPS) on an Applied Biosystems Peptide Synthesizer employing Fmoc (9- fluorenylmethoxycarbonyl) chemistry in which the amino nitrogen of each amino acid is blocked with Fmoc. Coupling was performed by activation of the carboxyl groups of the N-protected amino acids using 3 mol/ml of 2-(lH-benzotriazol-l-yl)-l, 1,3,3- tetrametyluronium tetrafluoroborate/l-hydroxybenzotriazole on the presence of diisopropylethylamine. Activated amino acids were sequentially added to the nascent peptide.
• FLOW CYTOMETRY ASSAY FOR PIF 7.1 MATERIALS Materials included Jurkat leukemia cells (JC); cloning medium; Falcon tubes for flow cytometry measurements; Mab CD2-Cy5 (Cy-chrome conjugated antibody, clone RPA-2.10, Pharmigen, Becton Dickinson); the biological sample (which could be a human serum to be assayed for PJJ? activity, or could be a solution of a putative or synthetic PIF peptide); PBS- 2 % BSA (100 mM phosphate saline buffer -2% bovine serum albumin; a negative control); trypan-blue dye; a CO 2 - incubator for cell culture; and a flow cytometer.
• JC Jurkat leukemia cells
• cloning medium Falcon tubes for flow cytometry measurements
• Mab CD2-Cy5 Cy-chrome conjugated antibody, clone RPA-2.10, Pharmigen, Becton Dickinson
• JC suspension To prepare the JC suspension: . Check the viability of the JC culture using Trypan blue dye exclusion staining. Cell viability should be between 80-90%. . Wash twice the JC with 10 ml of PBS-2 %BSA.
• JC suspension in cloning medium or PBS-2 %BSA containing 5,000,000 cells/ml. .Dispense 50 ml of JC suspension into falcon tubes (250,000 cells/tube).
• sample incubation For the sample incubation: .Add 200 ul samples, serum from early pregnancy controls (3 positive controls) or PBS-2% BSA (negative control). Mix gently. .Incubate at room temperature for 20-30 min.
• PIF negative activity should be in the range of : 130-340 Positive PIF samples are out side of the negative reference range

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