ELISA FOR VEGF

Abstract: The vascular endothelial growth factor (VEGF) activity in a patient's bloodstream or other biological sample can serve as a diagnostic and prognostic index for cancer, diabetes, heart conditions, and other pathologies. Antibody-sandwich ELISA method and kits for VEGF as an antigen were developed to detect VEGF levels in biological samples from animal models and human patients and are used as a diagnostic/prognostic index.

Description: ELISA FOR VEGF Background ot the Invention Field ol the Invention This invention relates to immunoassays for detecting VEGF that can be used as diagnostic and prognostic methods for patients with cancer, cardiovascular, or other pathologies Description ot Related Art It is now well established that angiogenesis is implicated in the pathogenesis ot a variety ot disorders These include solid tumors, intra-ocular neovascular syndromes such as pro terative retinopathies or age-related macular degeneration (AMD), rheumatoid arthritis, and psoriasis (Folkman et al J Biol Chem 267 10931 -10934 ( 1992), Klagsbrun etal Annu Rev Ph\sιol 53 217-239 ( 1991 ), and Garner A. Vascular diseases In Pathobiologi of ocular disease A dynamic approach Garner A, Klintworth GK, Eds 2nd Edition (Marcel Dekker, NY, 1994), pp 1625- 1710) In the case ot solid tumors, the ncovasculaπzation allows the tumor cells to acquire a growth advantage and prohterative autonomy compared to the normal cells Accordingly, a correlation has been observed between density of microvessels in tumor sections and patient survival in breast cancer as well as in several other tumors (Weidner et al N EnglJ Med 324 1 -6 ( 1991 ), Horak et al Lancet 40 1 120- 1 124 ( 1992), and Macchiaπni et al Lancet 340 145-146 (1992)) The search tor positive regulators of angiogenesis has yielded many candidates, including aFGF, bFGF, TGF-α, TGF-β, HGF, TNF-α, angiogenin, IL-8, etc (Folkman et al , supra, and Klagsbrun et al , supra) The negative regulators so tar identilied include thrombospondin (Good et al Proc Natl Acad Set USA 87 6624- 6628 ( 1990)), the 16-kιlodalton N-terminal fragment of prolactm (Clapp et al Endocrinolog y ,, 133 1292- 1299 ( 1993)), angiostatin (O'Reilly et al Cell 79 315-328 (1994)), and endostatin (O'Reilly et al Cell 88 277-285 ( 1996)) Work done over the last several years has established the key role ol vascular endothehal growth tactor (VEGF) in the regulation ol normal and abnormal angiogenesis (Ferrara et al Endocr Rev 18 4-25 ( 1997)) The finding that the loss of even a single VEGF allele results in embryonic lethality points to an irreplaceable role played by this factor in the development and differentiation of the vascular system (Ferrara et al , supra) Furthermore, VEGF has been shown to be a key mediator ot neovasculaπzation associated with tumors and intra-ocular disorders (Ferrara et al , supra) The VEGF mRNA is overexpressed by the majority ot human tumors examined (Berkman er a/ J Clin Invest 91 153-159 ( 1993), Brown et ! Human Pat ol 26 86-91 ( 1995), Brown et l Cancer Res 53 4727-4735 ( 1993), Mattern et al Brit J Cancer 73 931 -934 ( 1996), and Dvorak et al Am J Pathol 146 1029-1039 ( 1995)) Also, the concentration of VEGF in eye fluids is highly correlated to the presence of active proliferation of blood vessels in patients with diabetic and other ischemia-related retinopathies (Aiello e. al N Engl J Med 331 1480-1487 ( 1994)) Furthermore, studies have demonstrated the localization of VEGF in choroidal neovascular membranes in patients affected by acute macular degeneration (AMD) (Lopez et al Invest Ophtalmo Vis Set 37 855-868 ( 1996)) VEGF is a hepaπn binding growth factor with a molecular weight ot 45 kD (Plouet e/α/ EMBOJ 8 3801 ( 1989), Neufeld et al Prog Growth Factor Res 5 89 ( 1994)) It is a dimeπc glycoprotein consisting of two identical subumts Although VEGF is encoded from a single gene, at least five isoforms exist in vivo due to alternative mRNA splicing These isoforms, VEGF121 , VEGF145, VEGFl 65, VEGFl 89. and VEGF206, contain 121 , 145, 165, 189, and 206 ammo acids, respectively (Leung et al Science 246 1306 ( 1989), Houck et al Mol Endocnnol 5 1806 ( 1991 ), Tιscher efα J Biol Chem 266 1 1947 ( 1991 ), Neufeld etal The FASEB Journal 13 9- 22 (1999)) The VEGF isoforms show differing affinities for hepaπn, VEGF121 binds hepaπn weakly, while VEGF165, VEGF 189. and VEGF206 bind hepaπn with increasing affinity VEGF121 and VEGF 165 are secreted and both isotorms are found in the circulation In contrast, VEGFl 89 and VEGF206 are found mostly associated with hepaπn sulfate containing proteoglycans in the extracellular matrix (Houck et al J Biol C em 267 26031 ( 1992), Park et al Mol Biol Cell 4 1317 ( 1993)) Of the five isoforms, VEGFl 65 is the most abundantly expressed variant in the majority of cells and tissues Five receptors for VEGFhave been identified VEGFR-1 (FLT- 1 ), VEGFR-2 (KDR/FLK- l ), and VEGFR- 3, which are all signaling tyrosine kinases. and Neuropιlιn- 1 and Neuropιhn-2, which are both accessory-isoform- specific receptors that bind selectively to VEGF165 (de Vπes et al Science 255 989 ( 1992), Terman et al . Biochem Bioplns Res Conimun 187 1579 ( 1992), Millauer et αl Cell 72 835 ( 1993), Neufeld et αl , supra) The various roles of these receptors in VEGF biology are under active investigation by numerous groups VEGF is produced by tissues and does not have to enter the circulation to exert its biological effect, but rather acts locally as a paracπne regulator This raises the question of the significance of circulating VEGF and what role it plays in normal biology or pathology A recent study by Yang et al J Pharm E\p Tlier 284 103 ( 1998) found the clearance ot rhVEGF165 from the circulation to be very rapid, suggesting endogenous VEGF in the circulation is most likely the result of continual synthesis of VEGF In addition, several studies have tried to correlate levels of circulating VEGF with tumor burden and have suggested VEGF levels as a potential prognostic marker (Ferrari and Scaghottι £..r J Cancer32A 2368 ( 1996), Gaspaπni etal J Natl Cancerlnst 89 139 ( 1997), Kohn Cancer 80 2219 ( 1997), Baccala e. α/ Urology 51 327 ( 1998), Fujisaki et al Am J Gastroenterol 93 249 ( 1998)) Clearly the ability to accurately measure VEGF will be important to understand its potential role(s) in many biological processes, such as maintenance ot vascular patency menstrual cycle, ischemia, diabetes, and cancer The literature reports widely varying concentrations of endogenous VEGF in normal and diseased patients, ranging from undetectable to high levels It has been reported that VEGF 165/165 can be proteolytically cleaved into three other forms a 165/1 10 heterodimer, a 1 10/1 10 homodimer, and a 55-amιno-acιd C-terminal fragment (Keyt et al J Biol Chem 271 7788-7795 ( 1996), Keck et al Arch Biochem Bioplns 344 103- 1 13 ( 1997)) The ability to measure endogenous VEGF levels depends on the availability of sensitive and specific assays Coloπmetπc. chemiluminescence, and fluorometπc based enzyme-linked lmmunosorbent assays (ELISAs) for VEGF have been reported Houck et al , supra, ( 1992), Yeo et al Clin Chem 38 71 ( 1992), Kondo et al Biochim Bioplns Ada 1221 21 1 ( 1994), Baker et al Obstet G necol 86 815 ( 1995), Hanatani et al Btosci Btotechnol Biochem 59 1958 ( 1995), Leith and Michelson Cell Prolif 28 415 ( 1995), Shifren et al J Clin Endocrinol Metab 81 31 12 ( 1996), Takano ef α/ Cancer Res 56 2185 ( 1996), Toi et al Cancer 11 1 101 ( 1996), Brekken ef α. Cancer Res 58 1952 (1998), Obermair e/α/ Br J Cancer 11 1870- 1874 ( 1998), Webb et al Clin Sci 94 395-404 ( 1998) Similar ELISAs have been successfully applied in the determination ot low amounts of drugs and other antigenic components in plasma and urine samples, involve no extraction steps, and are simple to carry out The Houck et al , supra ( 1992) describe a coloπmetπc ELISA that appears to have ng/ml sensitivity, clearly not sensitive enough to detect endogenous VEGF levels Yeo et al , supra ( 1992) describe a two-site time-resolved immunoHuorometnc assay, however, no VEGF was detected in normal sera (Yeo etal Cancer Res 53 2912 ( 1993)) Baker et al , supra ( 1995), using a modified version ot this lmmunofluorometπc assay, reported detectable levels of VEGF in plasma from pregnant women with higher levels observed in women with preeclampsia Similar data in pregnant women were reported by Anthony etal Ann Clin Biochem 34 276 ( 1997) using a radioimmunoassay Hanatani et al , supra ( 1995) developed a chemiluminescent ELISA capable of measuring circulating VEGF and report VEGF levels in sera trom 30 normal individuals (male and female) from 8-36 pg/ml Brekken et al, supra ( 1998) described ELISA assays using antibodies having binding preference to either the VEGF alone or the VEGF Flk- 1 complex An ELISA kit tor VEGF detection is commercially available trom R&D Systems (Abingdon. U K ) The R&D VEGF ELISA kit has been used in sandwich assays wherein a monoclonal antibody is used to capture the target VEGF antigen and a polyclonal antibody is used to detect the VEGF Webb et al sttpru ( 1998) It is not clear whether the detection results using the R&D ELISA kit are influenced by the presence of proteolytical processes or degradation ot VEGF, or by interference of other serum proteins Obermair et al , supra ( 1998) Keyt erα/ J Biol Chem 271 7788-7795 ( 1996), Keyt etal J Biol Chem 111 5638 ( 1996), and Shifren etal , supra ( 1996) also developed a coloπmetπc ELISA based on a dual monoclonal antibody pair Although this ELISA was able to detect elevated VEGF levels in cancer patients, it lacked the sensitivity needed to measure endogenous levels of VEGF in normal individuals Rodriguez etal J Immunol Methods 219 45 ( 1998) described a two-site fluoπmetπc VEGF ELISA that yields a sensitivity of 10 pg/ml VEGF in neat plasma or serum However, this fluoπmetπc assay can only detect fully intact 165/165 and 165/1 10 species ot VEGF Thus, there is a need to develop a diagnostic and prognostic assay that detects higher measurable levels of VEGF in a biological sample ot an animal model or patient than existing ELISAs, and can measure all the isoforms ot VEGF Summary of the Invention A multi-site antibody-sandwich ELISA method and kits for VEGF as antigen were developed to detect VEGF in biological samples and used as a diagnostic/prognostic index Compared to the currently used VEGF ELISAs, the present assay has high sensitivity and is capable of detecting most of the isoforms of endogenous VEGF in circulation Specifically, the invention provides a method for detecting VEGF in a biological sample, preferably from vascular, diabetic, or cancer patients, comprising the steps of (a) contacting and incubating the biological sample with pre-mixed capture reagents immobilized to a solid support wherein the capture reagents are polyclonal and monoclonal antibodies against human VEGF, said monoclonal antibody binding specifically to the C-terminal (residues 1 1 1 - 165) of human VEGF, (b) separating the biological sample trom the immobilized capture reagents, (c) contacting the immobilized capture reagents with a detectable antibody that binds to the KDR and FLT1 receptor binding domains ot VEGF, and (d) measuring the level of VEGF bound to the capture reagents using a detection means tor the detectable antibody Preferably, the capture reagents are immobilized in a weight ratio of about 0 8 1 to 1 2 1 ot monoclonal to polyclonal antibody More preferably, the weight ratio is about I 1 of monoclonal to polyclonal antibody In another aspect, the invention provides an immunoassay kit tor detecting VEGF in a biological sample, the kit comprising (a) as capture reagents, polyclonal and monoclonal antibodies against human VEGF premixed in a weight ratio ol about 0 8 1 to 1 2 1 of monoclonal to polyclonal antibody, wherein the monoclonal antibody binds specif ically to the C-tcrminal (residues 1 1 1 - 165) of human VEGF. and (b) as detection reagent, a detectable antibody that binds to the KDR and FLT1 receptor binding domains ot VEGF The assay herein is unique in that it uses a polyclonal/monoclonal antibody mixture as the capture reagents, and the capture monoclonal antibody binds to the C-tcrminal portion ol VEGF Most of the previously disclosed VEGF ELISAs arc based on either a dual monoclonal antibody pair for capture/detection, or a monoclonal antibody as capture reagent and a polyclonal antibody for detection If a polyclonal antibody is used alone as the capture antibody, all sensitivity of the assay is lost The ability ot the monoclonal capture antibody to bind the VEGF C-tcrminus ensures that all the endogenous VEGF molecules, including 165/165, 165/1 10 and 1 10/1 10 can be detected by the assay described herein Furthermore, the detection antibody of the invention binds to the biologically active regions ol VEGF, I e , the binding domains for the KDR and FLT1 receptors ol VEGF, which ensures that the detected VEGF molecules arc free trom being blocked by, lor example, soluble VEGF receptors in the circulation As such, the assay described herein provides a more accurate measurement of circulating VEGF molecules that arc most likely biologically active Description ol the Drawings FIG 1 shows a comparison of two dif ferent preparations of affinity-purified rabbit polyclonal antibody against rhVEGF, with the squares depicting the preferred antibody and the circles representing the same antibody from a different bleed FIG 2 shows acompaπson of ELISAs herein using guanidine versus glycine elution of the af f lnity-puπfied rabbit polyclonal antibody against VEGF FIG 3 shows a comparison of typical standard curves for, and possible hook effect of, three different VEGF ELISAs, wherein the circles show the one-site assay with MAb 3 5F8 alone as coat and detection agent, the squares show the two-site assay with MAb 3 5F8 as coat and MAb A4 6 1 as detection agent, and the diamonds show the multi-site assay herein with MAb 3 5F8 and an af finity-puπfied polyclonal antibody as coat and MAb A4 6 1 as detection agent FIG 4 shows monoclonal antibody MAb 3 5F8 coat maximization wherein the ELISA uses 04 (circles), 1 (squares), 2 (diamonds), or 4 (triangles) μg/ml monoclonal antibody and 1 μg/ml affinity-purified polyclonal antibody FIG 5 shows rabbit polyclonal antibody coat maximization wherein the ELISA uses 0 (circles), 0 1 (squares), 0 4 (diamonds), 1 (triangles), 2 (reverse triangles with dotted lines), or 4 (reverse triangles with solid lines) μg ml affinity-purified polyclonal antibody and 0 4 μg/ml MAb 3 5F8 FIG 6 shows the effect of pH on the multi-site VEGF ELISA herein, wherein the circles represent the ELISA at pH 4 the squares, pH 5, the diamonds, pH 6, the triangles, pH 7, the half-line diamonds. pH 8. and the reverse diamonds, pH 9 FIG 7 shows dilution linearity of six normal human EDTA plasma samples spiked with rhVEGF in the multi-site VEGF ELISA FIGS 8A-8C show linearity ot normal rat EDTA plasma samples spiked with rhVEGF, wherein Fig 8A shows high spike, Fig 8B shows mid-spike, and Fig 8C shows low spike, and wherein the circles are rat pool 1 , the squares are rat pool 2 and the diamonds are rat 1 FIGS 9A-9B show linearity of. respectively, tour female and four male Yorkshire pig EDTA plasma samples spiked with rhVEGF FIGS 10A-10C show the specificity ot three dittercnt ELISA assays for VEGF forms 165/165 (circles), 165/1 10 (squares), 121/121 (diamonds), and 1 10/1 10 (triangles) Fig 10A shows the specificity ot the single-site ELISA using MAb 3 5F8 as coat and detection antibody (Fig 10A), Fig 10B shows the specificity of the two-site fluorimetπc VEGF ELISA assay using MAb 3 5F8 as coat and MAb A4 6 1 as detection antibody, and Fig 10C shows the specificity ot the multi-site VEGF ELISA herein using MAb 3 5F8 and PAb as coat antibodies and MAb A4 6 1 as detection antibody FIGS 1 1 A and 1 I B show, respectively, normal human plasma and serum VEGF detected by a two-site ELISA using only MAb 3 5F8 as coat reagent and by the multi-site ELISA herein using both the PAb and MAb 3 5F8 as coat reagents FIG 12 shows the amounts of plasma VEGF in cardiac patients using all three assays described in the legend to FIG 10, where the circles represent the single-site assay, the squares represent the two-site assay, and the triangles represent the multi-site assay FIG 13 shows plasma VEGF levels in normal donors and cardiovascular patients using the two-site assay with MAb 3 5F8 as coat and MAb A4 6 1 as detection antibody or the multi-site assay herein using MAb 3 5F8 and affinity-purified polyclonal antibody as coat and MAb A4 6 1 as detection antibody, where N is the number of patients FIG 14 shows serum VEGF from lung cancer patients detected by a two-site ELISA using only MAb 3 5F8 as coat reagent and by the multi-site ELISA herein using both the PAb and MAb 3 5F8 as coat reagents FIG 15 shows serum VEGF levels in normal donors and diabetic patients (non-insu n-dependent diabetes melhtus (NIDDM) and insulin-dependent diabetes melhtus (IDDM)) using the two-site ELISA with MAb 3.5F8 as coat and MAb A4 6 1 as detection antibody FIGS 16A and 16B show graphs comparing an attinity-puπfied polyclonal antibody to DNase and an affinity-purified polyclonal antibody to VEGF as one ot the coat reagents in the multi-site assay herein, as compared to the two-site assay using MAb 3 5F8 as coat reagent tor human plasma Fig 16A shows correlation ot plasma VEGF measured by the two-site ELISA using MAb 3 5F8 as the coat reagent (x-axis) with plasma VEGF measured by a multi-site assay with MAb 3 5F8 and a polyclonal antibody to DNase as the coat reagents (tilled circles), and with plasma VEGF measured by a multi-site assay as set torth herein using MAb 3 5F8 and the PAb to VEGF as the coat reagents (open circles) Fig 16B shows the standard curves of the two-site ELISA (tilled circles), the multi-site ELISA with MAb 3 5F8 and a polyclonal antibody to DNase as the coat reagents (tilled diamonds), and a multi-site assay as set forth herein using MAb 3 5F8 and the PAb to VEGF as the coat reagents (filled squares) Detailed Description of the Preferred Embodiments A Definitions The term "VEGF' as used herein refers to the 165-amιno acid vascular endothehal cell growth factor, and related 121-, 145-, 189-, and 206-amιno acid vascular endothehal cell growth factors, as described by Leung etal Scιence 246 1306 ( 1989), Houck etal Mol Endocrm 5 1806 ( 1991 ), and Neufeld etal sup ra, together with the naturally occurring allelic and processed forms ot those growth factors The term "detecting" is used in the broadest sense to include both qualitative and quantitative measurements of a target molecule In one aspect, the detecting method as described herein is used to identify the mere presence of VEGF in a biological sample In another aspect, the method is used to test whether VEGF in a sample is at a detectable level In yet another aspect, the method can be used to quantify the amount of VEGF in a sample and further to compare the VEGF levels from dif erent samples The term 'biological sample" refers to a body sample lrom any animal, but preferably is from a mammal, more preterably from a human Most preferably, such biological sample is from vascular, diabetic, or cancer patients Such samples include biological fluids such as scrum, plasma, vitreous fluid, lymph fluid, synovial fluid, tolhcular fluid, seminal fluid, amniotic fluid, milk, whole blood, urine, cerebro-spinal fluid, saliva, sputum, tears perspiration, mucus, and tissue culture medium, as well as tissue extracts such as homogenized tissue, and cellular extracts The preferred biological sample herein is serum, plasma or urine The term "capture reagent" refers to a reagent capable ot binding and capturing a target molecule in a sample such that under suitable condition, the capture reagent-target molecule complex can be separated from the rest of the sample Typically, the capture reagent is immobilized or immobilizable In a sandwich immunoassay, the capture reagent is preferably an antibody or a mixture of different antibodies against a target antigen The term "detectable antibody" refers to an antibody that is capable ot being detected either directly through a label amplified by a detection means, or indirectly through, e g , another antibody that is labeled For direct labeling, the antibody is typically conjugated to a moiety that is detectable by some means The preferred detectable antibody is biotinylated antibody The term "detection means" refers to a moiety or technique used to detect the presence of the detectable antibody in the ELISA herein and includes detection agents that amplify the immobilized label such as label captured onto a microtiter plate Preferably, the detection means is a fluoπmetπc detection agent such as avidin or streptavidm The term "antibody" is used in the broadest sense and includes monoclonal antibodies (including agonist, antagonist, and neutralizing antibodies), polyclonal antibodies, multivalent antibodies, multispecif ic antibodies, and antibody fragments so long as they exhibit the desired binding specificity The term "monoclonal antibody" as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i e , the individual antibodies comprising the population are identical except for possible naturally-occurring mutations that may be present in minor amounts Monoclonal antibodies are highly specific, being directed against a single antigenic site Furthermore, in contrast to conventional (polyclonal) antibody preparations that typically include different antibodies directed against ditterent determinants (cpitopes), each monoclonal antibody is directed against a single determinant on the antigen The modifier ' monoclonal" indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybπdoma method first described by Kohler et al Nature 256 495 ( 1975), or may be made by recombinant DNA methods (see, e g , U S Patent No 4,816,567) The "monoclonal antibodies" may also be isolated trom phage antibody libraries using the techniques described in Clackson erα/ Nature 352 624-628 ( 1991 ) and Marks et al J Mol Biol 222 581-597 ( 1991 ), for example The monoclonal antibodies herein specifically include "chimeπc" antibodies (immunoglobulins) in which a portion ot the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived trom a particular species or belonging to a particular antibody class or subclass, while the remainder of the chaιn(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments ot such antibodies, so long as they exhibit the desired biological activity (U S Patcnt No 4,816,567, and Morrison etal Proc Natl Acad Set USA cW 6851 -6855 ( 1984)) "Humanized" forms ot non-human (e g , muπne) antibodies are chimcπc antibodies that contain minimal sequence derived from non-human immunoglobulin For the most part, humanized antibodies are human immunoglobulins (recipient antibody) in which hypervaπable region residues ol the recipient are replaced by hypervaπable region residues from a non-human species (donor antibody) such as mouse, rat, rabbit or nonhuman primate having the desired specificity, affinity, and capacity In some instances, framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues Furthermore, humanized antibodies may comprise residues that are not found in the recipient antibody or in the donor antibody These modifications are made to further refine antibody performance. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervaπable regions correspond to those of a non-human immunoglobulin and all or substantially all of the FRs are those of a human immunoglobulin sequence The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin For further details see Jones et al Nature 321 522-525 ( 1986), Reichmann et al Nature 332 323-329 ( 1988), and Presta Curr Op Struct Biol 2 593-596 ( 1992) "Mammal" for purposes of treatment refers to any animal classified as a mammal, including humans, domestic, and farm animals, and zoo, sports, or pet animais, such as dogs, horses, cats, sheep, pigs, cows, etc Preterably, the mammal is human The terms cancer ', "cancerous , and "malignant ' reter to or describe the physiological condition in mammals that is typically characteπ/ed by unregulated cell growth Examples ot cancer include but are not limited to, carcinoma including adenocarcinoma, lymphoma, blastoma melanoma, sarcoma, and leukemia More particular examples of such cancers include squamous cell cancer, small-cell lung cancer, non-small cell lung cancer, gastrointestinal cancer, Hodgkin's and non-Hodgkin's lymphoma, pancreatic cancer, ghoblastoma, cervical cancer, ovarian cancer, liver cancer such as hepatic carcinoma and hepatoma, bladder cancer, breast cancer, colon cancer, colorcctal cancer, endometπa! carcinoma, salivary gland carcinoma, kidney cancer such as renal cell carcinoma and Wilms tumors, basal cell carcinoma, melanoma, prostate cancer, vulval cancer, thyroid cancer, testicular cancer, esophagcal cancer, and various types ol head and neck cancer The preferred cancers tor treatment herein are breast, colon, lung, and melanoma The phrases 'vascular" and cardiovascular ' are used interchangeably and describe patients with indications that stimulate angiogenesis and or cardiovasculaπ/ation, and those that inhibit angiogenesis and/or cardiovjsculaπ/ation Such disorders include, tor example, arterial disease, such as atherosclerosis, hypertension, inflammatory vasculitis, Reynaud's disease and Reynaud's phenomenon, aneurysms, and arterial restenosis, venous and lymphatic disorders such as thrombophlebitis, lymphangitis, and lymphcdema, and other vascular disorders such as peripheral vascular disease, cancer such as vascular tumors, e g , hemangioma (capillary and cavernous), glomus tumors, telangiectasia, bacillary angiomatosis, hcmangioendothclioma, angiosarcoma, haemangiopcπcytoma, Kaposi s sarcoma, lymphangioma and lymphangiosarcoma, tumor angiogenesis, trauma such as wounds, burns, and other injured tissue, implant f ixation, scarring, ischemia reperlusion injury, rheumatoid arthritis, ccrebrovascular disease renal diseases such as acute renal lailure. and osteoporosis This would also include angina, myocardial infarctions such as acute myocardial infarctions, cardiac hypertrophy, and heart failure such as congestive heart failure (CHF) The term "diabetes ' refers to a progressive disease ot carbohydrate metabolism involving inadequate production or utilization of insulin and is characterized by hyperglycemia and glycosuπa This term includes all forms of diabetes, such as type I and type II diabetes and insulin-resistant diabetes, such as Mendenhall's Syndrome, Werner Syndrome, leprechaunism, hpoatrophic diabetes, and other hpoatrophies The term "affinity purified" refers to purifying a substance by eluting it through an affinity chromatography column B Modes tor Carrying Out the Invention The assay described herein is a multi-site immunoassay utilizing the following steps First Step In the tirst step of the assay herein, the biological sample is contacted and incubated with the immobilized capture (or coat) reagents, which are an anti-VEGF monoclonal antibody and a polyclonal antibody directed against VEGF These antibodies may be from any species, but preferably the monoclonal antibody is a muπne or rat monoclonal antibody, more preferably uπne, and most preferably MAb 3 5F8 (Rodriguez et al supra ( 1998)), and the polyclonal antibody is an anti-rabbit or anti-goat antibody, more preferably anti-rabbit Furthermore, the polyclonal antibody is preferably affinity purified, to decrease background Hence, in a specific preferred embodiment, the immobilized monoclonal antibody is a muπne monoclonal antibody, most preferably MAb 3 5F8, and the immobilized polyclonal antibody is an aftinity-puπfied rabbit antibody The immobilized capture reagents are mixed together before they are immobilized Immobilization conventionally is accomplished by insolubihzing the capture reagents either before the assay procedure, as by adsorption to a water-insoluble matrix or surface (U S Pat No 3,720,760) or non-covalent or covalent coupling (for example, using glutaraldehyde or carbodumide cross- linking, with or without prior activation of the support with, e g , nitric acid and a reducing agent as described in U S Pat No 3,645,852 or in Rotmans et al J Immunol Methods 57 87-98 ( 1983)), or atterward, e g , by lmmunoprecipitation The solid phase used for immobilization may be any inert support or carrier that is essentially water insoluble and useful in lmmunometπc assays, including supports in the form of, e g , surfaces, particles, porous matrices, etc Examples ot commonly used supports include small sheets, Sephadex, polyvinyl chloride, plastic beads, and assay plates or test tubes manufactured trom polyethylene, polypropylene, polystyrene, and the like including 96-well microtiter plates, as well as paniculate materials such as filter paper, agarose, cross-linked dextran, and other polysacchaπdcs Alternatively, reactive water-insoluble matrices such as cyanogen bromide-activated carbohydrates and the reactive substrates described in U S Pat Nos 3,969,287, 3,691 ,016, 4, 195, 128, 4,247,642, 4,229,537, and 4,330,440 are suitably employed for capture reagent immobilization In a preferred embodiment the immobilized capture reagents are coated on a microtiter plate, and in particular the preferred solid phase used is a multi-well microtiter plate that can be used to analyze several samples at one time The most prelerred is a microtest 96-well ELISA plate such as that sold as Nune Maxisorb or Immulon The solid phase is coated with the pre-mixcd capture reagents as defined above, which may be linked by a non-covalent or covalent interaction or physical linkage as desired Techniques for attachment include those described in U S Pat No 4,376, 1 10 and the references cited therein If covalent, the plate or other solid phase is incubated with a cross-linking agent together with the capture reagent under conditions well known in the art such as for 1 hour at room temperature Commonly used cross-linking agents for attaching the pre-mixed capture reagents to the solid phase substrate include, e g , l , l-bιs(dιazoacetyl)-2-phenylethane, glutaraldehyde, N-hydroxysuccinimide esters, for example, esters with 4-azιdosalιcylιc acid, homobifunctional lmidoesters, including disuccinimidyl esters such as 3,3'-dιthιobιs(succιnιmιdylpropιonate), and bifunctional maleimides such as bιs-N-maleιmιdo- 1.8-octane Deπvatizing agents such as methyl-3-[(p-azιdophenyl)dιthιo]propιoιmιdate yield photoactivatable intermediates capable of forming cross-links in the presence of light If 96-well plates are utilized, they are preferably coated with the mixture of capture reagents (typically diluted in a butter such as 0 05 M sodium carbonate by incubation for at least about 10 hours, more preferably at least overnight, at temperatures of about 4-20°C, more preferably about 4-8°C, and at a pH of about 8-12, more preferably about 9- 10, and most preterably about 9 6 If shorter coating times ( 1 -2 hours) are desired, one can use 96-well plates with nitrocellulose filter bottoms (Millipore MULTISCREEN™) or coat at 37°C The plates may be stacked and coated long in advance ot the assay itself, and then the assay can be carried out simultaneously on several samples in a manual, semi-automatic, or automatic fashion, such as by using robotics The coated plates are then typically treated with a blocking agent that binds non-speciiically to and saturates the binding sites to prevent unwanted binding ot the free ligand to the excess sites on the wells of the plate Examples ot appropπate blocking agents for this purpose include, e g , gelatin, bovine serum albumin, egg albumin, casein, and non-fat milk The blocking treatment typically takes place under conditions of ambient temperatures for about 1 -4 hours, preterably about 1 5 to 3 hours After coating and blocking, the VEGF standard (purified VEGF) or the biological sample to be analyzed, appropriately diluted, is added to the immobilized phase The preferred dilution rate is about 5- 15%, preferably about 10%, by volume Butters that may be used for dilution for this purpose include (a) PBS containing 0 5% BSA. 005% TWEEN 20™ detergent (P20), 0 05% PROCLIN™ 300 antibiotic, 5 mM EDTA, 0 25% Chaps surfactant, 0 2% beta-gamma globulin, and 0 35M NaCl, (b) PBS containing 0 5% BSA, 0 05% P20, and 0 05% PROCLIN™ 300, pH 7, (c) PBS containing 0 5% BSA, 0 05% P20, 0 05% PROCLIN™ 300, 5 mM EDTA, and 0 35 M NaCl, pH 6 35, (d) PBS containing 0 5% BSA, 0 05% P20, 0 05% PROCLIN™ 300, 5 M EDTA, 0 2% beta-gamma globulin, and 0 35 M NaCl, and (e) PBS containing 0 5% BSA, 0 05% P20, 0 05%> PROCLIN™ 300, 5 mM EDTA, 0 25% Chaps, and 0 35 M NaCl Buffer (c) is the preferred buffer tor the assay herein since it has the best differentiation between each standard as well as the biggest signal-to-noise ratio PROCLIN™ 300 acts as a preservative, and TWEEN 20™ acts as a detergent to eliminate non-specific binding The added EDTA and salt ot buffer (c) act to decrease the background over the other buffers, including buffer (b) The weight ratio ot the capture reagents (monoclonal antibody to polyclonal antibody) is preferably about 0 8 I to about 1 2 1 , more preterably about I I The amount ot capture reagents employed is suf ficiently large to give a good signal in comparison with the VEGF standards, but not in molar excess compared to the maximum expected endogenous VEGF level in the sample For suf ficient sensitivity, it is preferred that the amount of biological sample added be such that the immobilized capture reagents are in molar excess of the maximum molar concentration of free VEGF anticipated in the biological sample alter appropriate dilution of the sample This anticipated level depends mainly on any known correlation between the concentration levels of the tree VEGF in the particular biological sample being analyzed with the clinical condition of the patient Thus, for example, cancer patients may have a maximum expected concentration of free VEGF in their serum that is quite high, whereas a normal child or adult will be expected to have a much lower level of free VEGF in their serum based on what is known in the literature If too much of the capture reagents are present, however, the capture reagents will compete with the anti- VEGF present in the biological sample for the bound VEGF, yielding inaccurate results Thus, while the concentration ot the capture reagents will generally be determined by the concentration range of interest of the VEGF taking any necessary dilution of the biological sample into account, the tinal concentration of the capture reagents will normally be determined empirically to maximize the sensitivity of the assay over the range ot interest However, as a general guideline, the molar excess is suitably less than about ten-fold ot the maximum expected molar concentration of tree VEGF in the biological sample after any appropriate dilution ot the sample Most preterably, the amount of monoclonal antibodies immobilized is about 04 μg/ml and the amount of polyclonal antibodies immobilized is about 0 4 μg/ml The conditions tor incubation of sample and immobilized capture reagent are selected to maximize sensitivity ot the assay and to minimize dissociation Preferably, the incubation is accomplished at fairly constant temperatures, ranging trom about 0°C to about 40°C, preferably trom about 36 to 38°C to obtain a less variable, lower coefficient ol variant (CV) than at, e g, room temperature The time for incubation depends primarily on the temperature, being generally no greater than about 10 hours to avoid an insensitive assay Preferably, the incubation time is from about 0 5 to 3 hours, and more preferably 1 5-3 hours at 36-38 °C to maximize binding ot free VEGF to capture reagents The duration of incubation may be longer if a protease inhibitor is added to prevent proteases in the biological fluid from degrading the VEGF At this stage, the pH of the incubation mixture will ordinarily be in the range of about 6-9 5, preterably in the range of about 6-7, more preferably about 6 0 to 6 5, and most preferably the pH of the assay (ELISA) diluent is 6 35 + 0 1 Acidic pH such as pH 4-5 decreased recovery of VEGF The pH of the incubation buffer is chosen to maintain a significant level of specific binding ot the capture reagents to the VEGF being captured Various buffers may be employed to achieve and maintain the desired pH during this step, including borate, phosphate, carbonate, Tπs-HCI or Tπs-phosphate, acetate, barbital, and the like The particular buf er employed is not critical to the invention, but in individual assays one buffer may be preferred over another Second Step In the second step of the assay method herein, the biological sample is separated (preferably by washing) from the immobilized capture reagents to remove uncaptured VEGF The solution used for washing is generally a buffer ("washing buffer' ) with a pH determined using the considerations and buffers described above for the incubation step, with a preferable pH range of about 6-9 The washing may be done three or more times The temperature ot washing is generally from refrigerator to moderate temperatures, with a constant temperature maintained during the assay period, typically trom about 0-40°C, more preferably about 4-30°C For example, the wash buffer can be placed in ice at 4 °C in a reservoir before the washing, and a plate washer can be utilized for this step A cross-linking agent or other suitable agent may also be added at this stage to allow the now-bound VEGF to be covalently attached to the capture reagents if there is any concern that the captured VEGF may dissociate to some extent in the subsequent steps Third Step In the next step, the immobilized capture reagents are contacted with detectable antibodies, preferably at a temperature of about 20-40°C, more preferably about 36-38 °C, with the exact temperature and time tor contacting the two being dependent primarily on the detection means employed For example, when 4-methylumbelhteryl-β-galactosιde (MUG) and streptavidin-β-galactosidase are used as the means tor detection, preterably the contacting is carried out overnight (e g , about 15- 17 hours or more) to amplify the signal to the maximum While the detectable antibody may be a polyclonal or monoclonal antibody, preterably it is a monoclonal antibody, more preferably murine, and most preferably MAb A4 6 1 Also, the preferred detectable antibody is directly detectable, and preferably has a fluoπmetπc label The fluoπmetπc label has greater sensitivity to the assay compared to the conventional coloπmetπc label More preterably, the detectable antibody is biotinylated and the detection means is avidin or streptavidin-β-galactosidase and MUG Preferably a molar excess of an antibody with respect to the maximum concentration of tree VEGF expected (as described above) is added to the plate alter it is washed This antibody (which is directly or indirectly detectable) is preterably a polyclonal antibody, although any antibody can be employed The at I mity of the antibody must be suf ficiently high that small amounts ot the tree VEGF can be detected, but not so high that it causes the VEGF to be pulled trom the capture reagents Fourth Step In the last step of the assay method, the level of free VEGF that is now bound to the capture reagents is measured using a detection means for the detectable antibody II the biological sample is Irom a vascular, diabetic, or cancer patient, the measuring step preterably comprises comparing the reaction that occurs as a result of the above three steps with a standard curve to determine the level of VEGF compared to a normal individual Antibody Production Polyclonal antibodies to the VEGF generally arc raised in animals by multiple subcutaneous (sc) or intrapcπloneal (φ) injections ot the VEGF and an adjuvant It may be useful to conjugate the VEGF or a fragment containing the target amino acid sequence to a protein that is lmmunogemc in the species to be immunized, e.g , keyhole limpet hcmocyanin, serum albumin, bovine thyroglobuhn, or soybean trypsin inhibitor using a bitunctionai or dcπvatizing agent, for example, maleimidoben/oyl sullosuccinimide ester (conjugation through cystcine residues), N-hydroxysuccinimide (through lysine residues), glutaraldehyde, succinic anhydride, SOCI : . or R'N = C = NR, where R and R are different alkyl groups The antibodies used as the coat or detectable antibodies may be obtained irom any convenient vertebrate source, such as murine, primate, lagomorpha, goat, rabbit, rat. chicken, bovine, ovine, equine, canine, feline, or porcine Chimcπc or humanized antibodies may also be employed, as described, e g , in U S Pat No 4,816,567, Morrison et al. Proc Natl Acad Sci USA X \ 6851 ( 1984), Neuberger et al Nature 3 X 2 604 ( 1984), Takeda e/ ../ Nature 314 452 ( 1985), and WO 98/45331 published October 15, 1998, as well as in those additional references set torth above Animals may be immunized against the lmmunogemc conjugates or derivatives by combining 1 mg or 1 μg of conjugate (for rabbits or mice, respectively) with 3 volumes of Freund's complete adjuvant and injecting the solution intradermally at multiple sites One month later the animals are boosted with 1/5 to 1/10 the original amount ot conjugate in Freund's incomplete adjuvant by subcutaneous injection at multiple sites 7 to 14 days later animals are bled and the serum is assayed for anti-VEGF titer Animals are boosted until the titer plateaus Preferably, the animal is boosted with the conjugate of VEGF, but conjugated to a different protein and/or through a different cross-linking agent Conjugates also can be made in recombinant cell culture as protein fusions Also aggregating agents such as alum are used to enhance the immune response Methods for the production ot polyclonal antibodies are described in numerous immunology textbooks, such as Davis et al Microbiology, 3rd Edition, (Harper & Row, New York, New York. 1980) Monoclonal antibodies are prepared by recovering spleen cells from immunized animals and immortalizing the cells in conventional fashion, e g by fusion with myeloma cells or by Epstein-Barr virus transformation, and screening tor clones expressing the desired antibody See, e g , Kohler and Milstein Eur J Immunol 6 51 1 ( 1976) Monoclonal antibodies, or the antigen-binding region of a monoclonal antibody, such as Fab or (Fab) 2 fragments, may alternatively be produced by recombinant methods Examples of suitable antibodies include those already utilized in known RIAs for the protein in question, e g , those antibodies directed against VEGF as described in the references given in the introduction herein Detection The antibody added to the immobilized capture reagents will be either directly labeled, or detected indirectly by addition, after washing off of excess first antibody, ot a molar excess ot a second, labeled antibody directed against IgG of the animal species of the first antibody In the latter indirect assay, labeled antisera against the first antibody are added to the sample so as to produce the labeled antibody in situ The label used tor either the first or second antibody is any detectable functionality that does not intertere with the binding ot free VEGF to the antibody Examples ot suitable labels are those numerous labels known for use in immunoassay, including moieties that may be detected directly, such as fluorochrome. chemiluminscent, and radioactive labels, as well as moieties, such as enzymes, that must be reacted or derivatized to be detected Examples 32 14 P5 3 131 ot such labels include the radioisotopes P, C, ~ I, H, and I, fluorophores such as rare earth chelates or fluorescein and its derivatives, rhodamine and its derivatives, dansyl, umbelhferone, luceπferascs, e g , firefly luciferase and bacterial luciterase (U S Pat No 4,737,456), lucifcπn, 2,3-dιhydrophthalazιncdιones. horseradish peroxidase (HRP), alkaline phosphatase, β-galactosidasc, glucoamylase, lysozyme, saccharide oxidascs, e g , glucose oxidasc galactose oxidase, and glucose-6-phosphate dehydrogenase, heterocychc oxidascs such as uncase and xanthinc oxidase. coupled with an enzyme that employs hydrogen peroxide to oxidize a dye precursor such as HRP, lactoperoxidase, or microperoxidase, biotin/avidin, biotin/streptavidin biotin/Streptavidin-β-galactosidase with MUG, spin labels, bactcπophage labels, stable free radicals, and the like As noted above the fluoπmetπc detection is preferred Conventional methods are available to bind these labels covalently to proteins or polypeptides For instance, coupling agents such as dialdehydes, carbodumides, dimaleimides, bis-imidates, bis-diazotized benzidine, and the like may be used to tag the antibodies with the above-described fluorescent, chemiluminescent, and enzyme labels See, for example, U S Pat Nos 3,940,475 (fluoπmetry) and 3,645,090 (enzymes), Hunter et al Nature 144 945 ( 1962), David et al Biochemistry 13 1014-1021 ( 1974), Pain et al J Immunol Methods 40 219-230 ( 1981 ), and Nygren J Histochem and Cytochem 30 407-412 ( 1982) Prefened labels herein are fluorescent to increase amplification and sensitivity to 8 pg/ml, more preferably biotin with streptavidin-β-galactosidase and MUG for amplifying the signal The conjugation ot such label, including the enzymes, to the antibody is a standard manipulative procedure tor one ot ordinary skill in immunoassay techniques See, tor example, O'Sulhvan et al "Methods tor the Preparation of Enzyme-antibody Conjugates for Use in Enzyme Immunoassay," in Methods in Enzymology , ed J J Langone and H Van Vunakis, Vol 73 (Academic Press, New York, New York, 1981 ), pp 147-166 Following the addition of last labeled antibody, the amount of bound antibody is determined by removing excess unbound labeled antibody through washing and then measuring the amount ot the attached label using a detection method appropriate to the label, and correlating the measured amount with the amount of free VEGF in the biological sample For example, in the case ot enzymes, the amount ot color developed and measured will be a direct measurement of the amount of VEGF present Specifically, if HRP is the label, the color is detected using the substrate OPD at 490 nm absorbance In one example, after an enzyme-labeled second antibody directed against the first unlabeled antibody is washed trom the immobilized phase, color or chemiluminiscence is developed and measured by incubating the immobilized capture reagent with a substrate of the enzyme Then the amount of free VEGF concentration is calculated by comparing with the color or chemiluminescence generated by the standard VEGF run in parallel As a matter ot convenience, the assay method ot this invention can be provided in the form ot a kit Such a kit is a packaged combination including the basic elements ot (a) capture reagents comprised ot polyclonal and monoclonal antibodies against human VEGF molecule, wherein the monoclonal antibody binds specifically to the C-terminal of the VEGF molecule, in a weight ratio ot about 0 8 1 to I 2 1 ot monoclonal to polyclonal antibody, and (b) detection reagents comprised of detectable (labeled or unlabeled) antibodies that bind to the KDR and FLT1 receptor binding domains ot VEGF These basic elements are defined heremabove Preferably, the kit further comprises a solid support for the capture reagents, which may be provided as a separate clement or on which the capture reagents are already immobilized Hence, the capture antibodies in the kit may be immobilized on a solid support, or they may be immobilized on such support that is included with the kit or provided separately from the kit Preferably, the capture reagents are coated on a microtiter plate The detection reagent may be labeled antibodies detected directly or unlabeled antibodies that are detected by labeled antibodies directed against the unlabeled antibodies raised in a different species Where the label is an enzyme, the kit will ordinarily include substrates and cofactors required by the enzyme, and where the label is a fluorophore, a dye precursor that provides the detectable chromophore Where the detection reagent is unlabeled, the kit may further comprise a detection means for the detectable antibodies, such as the labeled antibodies directed to the unlabeled antibodies, preterably in a fluoπmetπc-detected format In a prefened specific embodiment, the weight ratio of monoclonal antibody to polyclonal antibody in the kit is about 1 1 , the detectable antibody is a biotinylated murine monoclonal antibody, the monoclonal antibody is murine or rat, more preferably murine, and most preferably MAb 3 5F8, the polyclonal antibody is affinity purified, and more preferably from goat or rabbit, most preferably rabbit, and the amount of murine monoclonal antibodies is 0 4 μg/ml and the amount ot rabbit polyclonal antibodies is 0 4 μg/ml Preferably, the capture reagents are immobilized in this kit Also, preterably the detectable antibody is MAb A4 6 1 The kit also typically contains instructions for carrying out the assay, and/or VEGF as an antigen standard (e g , purified VEGF, preferably recombinantly produced VEGF), as well as other additives such as stabilizers, washing and incubation buffers, and the like Examples of standards for VEGF are recombinant human VEGF produced in mammalian cells available trom Genentech, Inc , South San Francisco California The components of the kit will be provided in predetermined ratios, with the relative amounts of the various reagents suitably varied to provide for concentrations in solution of the reagents that substantially maximize the sensitivity ot the assay Particularly, the reagents may be provided as dry powders, usually lyophilized. including excipients, which on dissolution will provide for a reagent solution having the appropriate concentration for combining with the sample to be tested The following examples are intended to illustrate one embodiment now known tor practicing the invention, but the invention is not to be considered limited to these examples All open and patented literature citations herein are expressly incorporated by reference EXAMPLE 1 2 Materials and Methods 2 I Reagents Purified recombinant human VEGF165 (rhVEGF) expressed in Escheπchia coh (Genentech, South San Francisco, CA) was used as the standard and for the controls (prepared in ELISA diluent as defined below and stored at -70°C) Streptavidin-β-galactosidase (Strep-β-gal) was purchased from Boehπnger Mannheim, W Germany, MUG was purchased from Sigma, St Louis, MO Dimethylsultoxide (DMSO) was purchased from Sigma 2 2 Antibodies to VEGF Antibodies against rhVEGF 165 were prepared as described in Kim et al , Growth Factors, 7 53 ( 1992) Briefly, BALB/c mice were hypeπmmunizcd intrapeπtoneally with a 10 mg dose ot rhVEGF165 conjugated to keyhole limpet hemocyanin Spleen cells were fused with a mouse myeloma line and culture supernatants from wells containing hybndomas were screened for the presence of MAbs to rh VEGFl 65 by an ELISA Positive hybndomas were cloned twice using the limiting dilution technique The monoclonal antibodies used in this ELISA have been characterized in Kim et al , supra ( 1992) One of the capture antibodies, MAb 3 5F8, is thought to bind near the hepaπn binding domain, amino acid residues 1 1 1 -165, with a K j of 13 pM Rodriguez etal , supra ( \99%) The rabbit polyclonal antibody (PAb) used as the other coat antibody was generated by injecting VEGF into a rabbit using a standard protocol, and purified by passing it through an affinity column to which VEGF was coupled to capture the polyclonal antibody, thus removing the immunoglobulins from the sample The molecules that are not the desired antibody were washed off and the bound antibody was eluted with 0 2 M glycine, pH 2, then the pH was brought to neutral prior to dialysis overnight in PBS at 4 C, and the elutent containing the antibody was used for the multi-site assay The detection antibody, MAb A4 6 1 binds rhVEGF 165 with a Kd ot 86 pM Several lines ot evidence suggest that this MAb binds rhVEGF near the KDR receptor binding region (Kim et al , supra ( 1992)) 2 3 Biotinylation of MAb A4 6 1 The MAb A4 6 1 was biotinylated with biotinylamidocaproic acid-N-hydroxysuccinimide ester (Biotin-X-NHS) (Research Organics. Cleveland. OH) according to the following protocol The MAb A4 6 1 was dialyzed against 100 mM NaHC0 3 , pH 8 5 overnight at 2-8°C A total of 60 μl ot a 5-mg/ml solution of Biotin-X-NHS in DMSO was added to the MAb (adjusted after dialysis to a concentration ot 2-10 mg/ml) using a 1 10 (w/w) ratio of Biotin MAb This mixture was allowed to incubate tor two hours at ambient temperature with gentle agitation, and the reaction was stopped by the addition of 5 μl of ethanolamine Alter conjugation, the antibody was extensively dialyzed against PBS at 2-8 c C with gentle agitation and PBS changed every two hours for a total ot three times 2 4 Multi-Site VEGF ELISA Two MAbs, 3 5F8 (coat) and biotinylated A4 6 1 (detection), and one PAb (coat) as described above were used to develop a specific and sensitive VEGF ELISA In this ELISA, 100 μl/well each ol MAb 3 5F8 and the atf lnity-puπf led PAb were mixed together and then added to MaxiSorp™ 96-well microtiter plates (Nunc Roskilde. Denmark) at 0 4 μg/ml each in 0 05 M sodium carbonate, pH 9 6 Following 24-74-hour incubation at 2-8°C, the coated plates were washed 3 times with 400 μl ELISA wash buffer (PBS containing 0 05% TWEEN-20™detergent) using a BIOTEK EL304 r platewasher (Biotek Instruments, Winooski, VT), and blocked with ELISA blocking diluent at 200 μl/wcll (PBS containing 0 5% BSA, 0 05% TWEEN-20™, and 0 05% PROCLIN™ 300 antibiotic, pH 7 2) tor 1 -3 hours at ambient temperature with agitation After blocking, the plates were washed again 3 times with 400 μl ELISA wash buffer Then, 100 μl/wcll of standards, samples, or controls were added to duplicate wells and incubated for 1 5-2 hours at 37°C with agitation For quantitation of rhVEGFl 65 in human plasma, the standard curve was prepared in ELISA diluent (PBS containing 0 5% BSA, 005% TWEEN-20™, 0 05% PROCLIN™ 300, 5 mM EDTA, and 0 35 M NaCl, pH 6 3 + 0 1 ) The standard curve was 128 pg/ml diluted serially 1 2 to 2 pg ml After the sample/standard incubation, the plates were washed six times with 400 μl ELISA wash butter, and 100 μl/well of MAb A4 6 1 -Bιotιn, freshly diluted 1 200 to its optimal concentration in ELISA diluent, was added to the plates Alter a 1 5-2-hour incubation at 37°C with agitation, the plates were washed six times as described above and 100 μl/well of strep-β-gal, diluted 1 40K in ELISA diluent, was added to the plates After a 45-60-mιnute incubation at 37°C with agitation, the plates were washed 6 times as described above and 100 μl/well of MUG/DMSO ( 1/100), freshly diluted to 340 μg ml in a solution of 0 1 M NaP0 , containing 1 mM MgCl 2 at pH 7 3 +0 1 , was added to the plates The substrate reaction incubated for 15- 17 hours at 37°C with agitation in the dark (plate was wrapped with foil) The reaction was stopped by adding 150 μl/well ot 0 15 M glycine, pH 10 5 + 0 1 The fluorescent unit (FSU) of the well contents was read on a CYTOFLUOR 4000™ fluorescent plate reader (PerSeptive Biosystems, Framingham, MA) using 360 nm excitation and 460 nm emission filters A four-parameter curve fit program was used to generate a standard curve, from which sample and control concentrations were interpolated FSU readings were stable for at least 30 minutes at room temperature after 150 μl glycine was added 2 5 Human plasma samples The ability to accurately measure VEGF in human plasma was assessed using several approaches The effect of plasma on the assay sensitivity and performance was evaluated using rhVEGF 165 Known amounts ot rhVEGF165 were added to individual human plasma samples and the percent recovery determined as follows ( 1 ) the amount ot endogenous VEGF in the sample determined trom a parallel sample, was subtracted trom the total amount of VEGF measured in the sample, (2) the "recovered' VEGF value was then divided by the amount of VEGF added to the sample and multiplied by 100 The dilution linearity ot rhVEGF165 added into individual human plasmas was also evaluated In these studies, following rhVEGFl 65 addition, each plasma sample was diluted 1 10 in ELISA diluent followed by serial 1 2 dilutions in ELISA diluent High and low matrix (standard) controls were prepared in neat human EDTA plasma (frozen) They were diluted 1/10 in ELISA diluent tor a tinal concentration of 10% plasma Endogenous VEGF levels were measured in individual human plasma samples Blood trom normal healthy individuals was drawn into 15% K3 EDTA Vacutainer tubes (Becton Dickenson, San Jose, CA) The tubes were centπfuged at 2000xg tor 20 mm and the plasma was collected Plasma samples were diluted 1 10 in ELISA diluent for use in the assay T e dilution linearity ot endogenous VEGF in selected samples was also evaluated as described above 3 Results 3 1 Sample Stability The stability ot neat human EDTA plasma was examined for three freeze-and thaw cycles The plasma received a dry ice treatment followed by a gentle mixing in warm water in order to thaw The data in Table 1 below demonstrate that there is no significant effect of quantitation of VEGF following freeze-and thaw treatments Therefore, human EDTA plasma is stable for three freeze-and thaw cycles TABLE 1 Net Freezc-Thaw Stabil ty of Normal Human EDTA Plasma hu EDTA Plasma Two-Site Multi-Site 32 22 1 1 78 84 Fresh 25 4 75 16 1 freeze-thaw 14 85 75 16 2 freeze-thaw 18 88 72 08 3 freeze-thaw mean 20 31 75 31 stddev 4 51 2 77 %CV 2 2 4 33 35 44 100 24 Fresh 35 87 101 71 1 freeze-thaw 35 44 101 71 2 freeze-thaw 39 19 101 71 3 freeze-thaw mean 36 49 101 34 stddev 1 81 0 73 %CV 5 1 34 17.51 78.18 Fresh 25.03 94.6 1 freeze-thaw 22.1 1 94.6 2 freeze-thaw 24.72 83.95 3 freeze-thaw mean 22.34 87.83 stddev 3.48 8.16 %CV 16 9 39 29.35 84.62 Fresh 31.1 1 81.39 1 freeze-thaw 28.02 75.16 2 freeze-thaw 31.1 1 71.51 3 freeze-thaw mean 29.90 78.17 stddev 1.50 5.93 %CV 5 8 38 23.43 83.95 Fresh 29.94 80.07 1 freeze-thaw 21.8 83.95 2 freeze-thaw 24.72 66.84 3 freeze-thaw mean 24.97 78.70 stddev 3.52 8.12 %CV 14 10 Mean 12 6 stddev = standard deviation CV = coefficients of variation 3.2 Limit of Detection Approximately 20 replicates of the blank, 1 , 2, 4 and 8 pg/ml standard, were assayed in the multi-site VEGF ELISA herein. The limit of detection was determined by the analytc (VEGF) concentration for which the measured mean FSU response minus two standard deviations was greater than the mean FSU response plus two standard deviations of the blank fluorescence emission (460 nm). Results in Table 2 show that the limit of detection is 8 pg/ml in ELISA diluent. Since plasma samples are typically diluted 1 : 10 to minimize matrix interference, as little as 80 pg/ml, or 1.6 pM VEGF can be measured in the original sample. TABLE 2: Limit of " Detection (0.4 μg/ml, 0.4 μg/ml) std std std std std replicates 0 pg/ml 1 pg/ml 2 pg/ml 4 pg/ml 8 pg/ml FSUs FSUs FSUs FSUs FSUs 1 1 103 1277 1351 1546 2216 2 1091 1382 1359 1617 2292 3 1 103 1336 1413 1745 2241 4 1 180 1328 1986 1770 2266 5 1235 1321 1382 1654 2216 6 1 135 1382 1631 1735 2216 7 1180 1306 1328 1692 2266 8 1154 1125 1512 1654 2241 9 1079 1351 1366 1682 2279 10 1129 1559 1529 1678 2384 11 1129 1314 1445 1654 2266 12 1263 1413 1299 1617 2228 13 1079 1382 1336 1631 2216 14 1235 1284 1851 1716 2565 15 1135 — 1711 1780 2266 16 1129 — 1590 2077 2266 17 1017 — 1445 1654 2279 18 1351 — 1445 1740 2371 19 1079 — 1546 1599 2318 20 2025 — 1626 1663 2228 mean 1192 1340 1508 1695 2281 std dev 211 94 183 108 82 + 1 SD 1402 1434 1690 1803 2363 + 2SD 1613 1528 1873 1911 2445 1 SD 981 1246 1325 1587 2199 2SD 770 1152 1142 1479 2117 3 3 Testing and Preparation ot Anti-VEGF PAb Two dif ferent preparations ol rabbit polyclonal antibody against rhVEGF purified Irom the same rabbit but a dif ferent bleed were compared in the assay, using MAb 3 5F8 as the monoclonal antibody, and using 0 4 μg/ml of each type ot antibody The results, indicated in Fig 1 , show that both antibodies are suitable for use Rabbit polyclonal antibody elution was performed with glycine followed by guanidine and the resulting antibodies were used in the assay with the preferred conditions herein Results in Figure 2 and Table 3 show that there is no significant difference between the two elution methods However, the glycine elution seems to be slightly more sensitive Comparison of normal human EDTA plasma samples as well as the High and Low Matrix controls show similar quantitation in both preparations The guanidine peak is more tightly bound to the VEGF than the glycine peak TABLE 3 Comparison ol glycine and guanidine as eluents 3 4 Robusincss/Ruggedness Inter-assay and intra-assay precision was evaluated tor the low and high matrix controls by ANOVA statistical analysis Matrix controls were prepared by spiking rhVEGF into neat human EDTA plasma at low and high concentrations to lall within the assay range Results show that the inter-assay variability (CV) ranges from 1 1 - 17% while the intra-assay variability ranges Irom 8- 14%. The data is summarized in Table 4. TABLE 4 Reproducibilitv of the Matr x Controls Assay Name High (pg ml) Low (pg/ml ) kn324p2 107.5 6.8 kn324p2 1 1 1.2 1 1.6 kn324P3 93.8 10.4 kn324p3 96 7 1 1.2 kn320p7 103 6 13.7 kn320p7 103 6 13.7 kn320p8 99.7 14.3 kn320p8 102 0 14.7 kn322p2 1 10 6 13.3 kn322p2 102.0 — kn322p3 97 0 14.4 kn322p3 103.9 13.9 kn322p l 99.0 12.0 kn322pl 95.2 12 3 kn320p3 101.1 15.3 kn320p3 98.0 14.5 kn320p2 105.1 14.9 kn320p2 100.5 14.2 kn320pl 106.0 14.1 kn320pl 103.4 13.9 kn319p2 87.1 10.2 kn319p2 100.2 9.3 kn319pl 97.6 9.4 kn319pl 99.6 9.1 kn316pl 92.4 11.7 kn3I6pl 97.9 11.3 kn313pl 117.8 18.8 kn313pl 111.4 16.2 kn212p2 92.4 14.6 kn212p2 92.4 15.7 kn311pl 123.9 14.2 kn212pl 103.8 13.9 kn212pl 93.2 13.7 kn33Ipl 106.2 12.9 kn331pl 109.2 13.3 kn331p2 99.8 11.9 Matrix Controls Intra-assay (% CV) Inter-assay (% CV) Low 14.0 11.0 High 8.0 17.0 3.5 Hook Effect Several samples in the past have shown non-linearity of increasing VEGF measured with increasing sample dilution. Therefore, the multi-site ELISA herein was tested for a hook effect (side-by-side comparison with the one- and two-site ELISAs). rhVEGF was diluted from 16 ng/ml to 1 pg/ml in assay buffer. Results (depicted in Figure 3) show that there is no significant drop in VEGF quantitation. However, a slight drop and plateauing effect can be seen from 512 pg/ml onward. Since the sample dilutions used in the multi-site ELISA assay herein give rise to concentrations less than 128 pg/ml, the hook effect is not a concern. 3.6 Coat Maximization The procedures for determining coat maximization were the same as described above in the Methods section except that the concentration of either the PAb or the MAb 3.5F8 coat was varied. Specifically, for Fig. 4 the concentration of MAb 3.5F8 was varied from 0.4 to 4 μg/ml while keeping constant the concentration of polyclonal antibody (at 1 μg/ml), and for Fig. 5 and Table 5 the concentration of polyclonal antibody was varied from 0.4 to 4 μg ml while keeping constant the concentration of MAb 3.5F8 (at 0.4 μg/ml). While the 0.1 and 0.4 μg/ml concentrations of MAb 3.5F8 and of the PAb at the constant concentration of the other coat antibody were essentially the same in VEGF quantitation for the low and high control, the upper limit of coat concentration (e.g., 0.4 μg/ml) is prefened to better the chances that the VEGF is captured. While the concentration of 1 μg/ml of MAb 3.5F8 and PAb increased the amount of VEGF measured in each case, such a concentration also gave higher background. Hence, the results show that the preferred concentrations for both capture reagents is about 0.4 ug/ml. TABLE 5: Coat Maximization of the Polyclonal Antibody plus MAb 3.5F8 MAb 3.5F8 0.4 μg/ml 0.4 μg/ml 0.4 μg/ml 0.4 μg/ml PAb 1 μg/ml 0.4 μg/ml 0.1 μg/ml 0 High matrix 100.4 89.3 94.0 97.3 (pg/ml): Low matrix 22.4 9.7 10.1 5.4 (pg/ml): Eight separate 97.3 33.5 42.5 10.7 normal human 202.5 106.5 77.0 19.7 plasma donors 162.3 52.9 59.0 26.8 (pg ml): 92.0 27.5 29.8 1 1.1 1 15.6 41.4 42.5 1 1.0 202.5 70.8 69.7 15.8 409.9 196.6 207.9 94.9 512.1 25.7 275.0 1 13.0 3.7 pH Profile of the Multi-site VEGF ELISA A pH profile was performed to determine whether changing pH of the assay buffer would increase or decrease recovery of VEGF in normal human EDTA plasma. Changing the pH could dissociate binding proteins or other complexes, if any, which would interfere with the MAb A4.6.1 detection. The procedure for examining the pH profile of the assay was the same as described in the Methods section above except that for the sample incubation and biotin incubation, the assay buffer was adjusted using NaOH or HC1, resulting in assay buffers ranging from pH 4 to 9. A standard curve, a low and high matrix, and four normal human EDTA plasma samples were evaluated from dilutions performed using these varying-pH assay buffers. Results in Fig. 6 and Table 6 show that there was no recovery of VEGF at pH 4 and 5. However, pH 6-9 revealed good VEGF plasma recovery with the assay control within an acceptable range. There was no significant difference in VEGF quantitation as a consequence of varying the pH of the assay buffer from 6 to 9. However, the preferred assay buffer is one with a pH of about 6.35 + 0.1 , which results in maximal VEGF binding and is appropriate for all dilution steps of the assay. TABLE 6: VEGF Recovery Normal Human EDTA Plasma at varying pH PH 4 5 6 7 8 9 Normal Human EDTA Plasma pg/ml pg/ml pg/ml pg/ml 1 — — 198.9 122.0 173.3 204.0 2 — — 141.4 81.7 138.7 138.6 3 — — 240.7 150.3 220.9 243.5 4 — — 1 12.2 1 13.2 176.7 190.3 Controls pg/ml pg ml pg/ml pg ml High Matrix — — 104.5 105.0 93.8 124.0 Low Matrix — — 25.7 25.1 19.7 16.9 3.8 Dilution Linearity Approximately 85 pg/ml rhVEGF was spiked into neat human EDTA plasma and serially diluted to 1/10, 1/20, 1/40, and 1/80 and analyzed. The results, in Table 7 and Fig. 7, show that rhVEGF spiked in EDTA plasma showed linear correlation to expected concentration, with a coefficient correlation of 0.996. The percent difference between dilution-corrected concentration values determined for successive serial dilutions did not exceed a mean of 19% + 7.5, as shown in Table 7. TABLE 7: Dilution Linearity of Normal Human EDTA Plasma Normal Human [Measured] Dilution Corrected % EDTA Plasma pg/ml Concentration Difference (samples) S I 103 10 1026 — 62 20 1237 21 35 40 1416 14 20 80 1599 13 S2 109 10 1088 — 59 20 1 176 8 35 40 1416 20 22 80 1788 26 S3 104 10 1039 — 60 20 1202 16 32 40 1278 6 21 80 1677 31 S4 88 10 878 — 52 20 1036 18 32 40 1278 23 19 80 1528 20 S5 93 10 926 — 57 20 1 136 23 32 40 1278 12 18 80 1433 12 S6 1 19 10 1 192 — 81 20 1612 35 47 40 1893 17 29 80 2298 21 3.9 Accuracy - Quantitation ot VEGF in Human Plasma Endogenous VEGF levels were measured in freshly-collected plasma from several normal healthy individuals The individual human EDTA plasma samples were spiked with lowest, low. mid, and high concentrations ot rhVEGF so as to fall within the assay range of the standard curve. Endogenous VEGF concentrations were determined and subtracted trom the measured concentration to obtain comparison to the targeted spike. Results in Table 8 show that mean % recoveries were 99%, 1 13%, 106%, and 1 18% lor the high, mid. low, and lower spikes, respectively. TABLE 8. Spike Recovery ot rhVEGF in Human EDTA Plasma [Endogenous] [Measured] [Measured-Endogenous] [Targeted] % pg/ml pg/ml pg/ml pg/ml Recovery 18.6 100.5 81.9 85.3 96 22.5 1 14 8 92.3 85.3 108 High 30.3 1 1 1.0 80.8 85.3 95 Spike 22.8 96.2 73.4 85 3 86 18.4 103.2 84.9 85.3 100 34 1 121.1 87 0 85.3 102 Mean % Recovery 99 21.0 98 3 47.1 49.3 96 9.1 89.1 80 I 49.3 162 Mid 10.8 66 8 55.9 49.3 1 13 Spike 21.0 59.5 38.5 49.3 78 9.1 66 8 57 8 49.3 1 17 Mean % Recovery 1 13 4.5 32.9 28.4 22.9 124 10.0 32.9 22.9 22.9 100 Low 14.9 38.3 23.4 22.9 102 Spike 8.6 31.2 22.6 22.9 99 9 3 33.7 24.4 22.9 107 15.9 40 9 25.0 23.5 106 36 2 58.8 22.6 23.5 96 38 9 66 4 27.5 23.5 1 17 Mean % Recovery 106 4 3 24.9 20.2 17.8 1 14 4.6 26.1 21.5 17.8 120 7.4 27.9 20.4 17.8 1 14 Lower 6.6 26.4 19.9 17.8 1 1 1 Spike 10.8 33.1 22.2 17.8 124 * 5.5 29.6 24.0 17.8 135 3.9 22 7 18.6 17.8 105 Mean % Recovery 1 18 *0.4 μg/ml MAb 3.5F8 + 0.4 μg/ml PAb coat 3 10 Accuracy - Quantitation ot VEGF in Normal Rat EDTA Plasma An individual and two pooled male rat EDTA plasma samples were spiked with low, mid and high concentration of rhVEGF so as to fall within the assay range of the standard curve. Endogenous VEGF concentrations were determined and subtracted trom the measured concentration in order to obtain comparison to the targeted spike (dilution control) Spikes were then diluted 1 2 in ELISA diluent to determine dilution linearity Results in Table 9 show that mean percent recoveries range from 84-103% for the high, mid and low spikes that were greater than 6 25 pg/ml TABLE 9 VEGF Spike Recovery in Normal Rat EDTA Plasma 3 1 1 Linearity ot Normal Rat EDTA Plasma in ELISA Diluent Rat EDTA plasma (2 male pools, 1 individual) was tested for linearity of dilution Neat plasma samples were spiked with low (20 pg/ml) mid (44 pg ml), and high (98 pg ml) concentrations of rhVEGF and were serially diluted 1/10, 1/20, 1/40, 1/80 in ELISA diluent Results in Table 10 and Figs 8A-8C show that normal rat plasma samples dilute linearly following a minimum 1/20 dilution in the assay range of 8-128 pg/ml TABLE 10 Summary of Linearity for Rat Plasma Samples (in units of coefficient of correlation (R)) 3.12 Accuracy - Quantitation of VEGF in Normal Yorkshire Pig EDTA Plasma Eight Yorkshire pig EDTA plasma samples (four males and four females) were spiked with low, mid. and high concentrations of rhVEGF so as to fall within the assay range of the standard curve. Endogenous VEGF concentrations were determined and subtracted from the measured concentration in order to obtain comparison to the targeted spike (dilution control). Spikes were then diluted 1/10, 1/20, 1/40, 1/80 in ELISA diluent to determine dilution linearity. Results, shown in Figure 9A (females) and Figure 9B (males), and in Table 1 1 , show that normal rat plasma samples dilute linearly following a minimum 1/20 dilution in the assay range of 8-128 pg/ml. TABLE 1 1 : Summary of Linearity for Yorkshire Pig Samples 3.13 Detection of Various Forms of VEGF Using Three ELISAs This experiment was designed to determine if the multi-site ELISA herein could measure all the variants of VEGF. Figures 10A. 10B, and 10C show a comparison of the single-site, two-site, and multi-site ELISAs for VEGF, respectively. It can be seen by comparing these graphs that the multi-site assay herein is capable of capturing more VEGF variants. 3.14 Detection Using Two-Site, Multi-Site, or PAb as Coat The multi-site ELISA herein using PAb and MAb 3.5F8 as coat antibodies was compared to an ELISA using only MAb 3.5F8 or PAb as coat antibody for evaluating the amount of VEGF in normal human samples. The results, set forth in Table 12, show that the amount of VEGF detected in pg/ml was much higher for the multi-site assay than for the assay with PAb alone or MAb 3.5F8 alone. TABLE 12: Amount of VEGF in Normal Human Plasma Samples Using PAb Alone, MAb alone, or PAb and MAb LTS = not detectable 3.15 Comparison of VEGF Levels in Normal Human Plasma and Normal Human Serum using Two-site and Multi-site ELISAs Plasma and serum samples from normal human donors were analyzed by the two-site ELISA with MAb 3.5F8 as capture antibody and PAb A4.6.1 as detection antibody and by the multi-site assay herein using the PAb and MAbs and procedures noted in the Methods. The results, summarized in Figures 1 lA and 1 IB for plasma and serum respectively, indicate that the multi-site assay herein detects more VEGF in both types of samples than the two-site assay. 3.16 Comparison of VEGF Levels in Normal and Cardiopathological Patients using Single-site, Two-site, and Multi-site ELISAs Samples from normal human donors and from donors with cardiac disease who were enrolled in clinical trials sponsored by Genentech, Inc. to evaluate efficacy of TNK, a t-PA variant, were analyzed by the single-site ELISA with MAb 3.5F8 as coat and detection agent, by the two-site ELISA with MAb 3.5F8 as capture antibody and MAb A4.6.1 as detection antibody, and by the multi-site assay herein using the PAb and MAbs and procedures noted in the Methods. Figure 12 shows the amounts of plasma VEGF in cardiac patients using all three assays, and Figure 13 and Table 13 summarize the amounts of VEGF in normal and cardiac patients using the two-site and multi-site assays by the mean amount of VEGF, standard deviation, % CV and s.e.m. The results indicate that the multi-site assay herein detects more VEGF in both types of samples than the two-site assay. TABLE 13: Sensitivity of Two-Site and Multi-Site Assays to VEGF in Normal and Cardiac Patients 3.17 Comparison of Serum VEGF Levels in Lung Cancer Patients using Two-site and Multi-site ELISAs Serum samples from non-small cell lung carcinoma patients were analyzed by the two-site ELISA with MAb 3.5F8 as capture antibody and MAb A4.6.1 as detection antibody and by the multi-site assay herein using the PAb and MAbs and procedures noted in the Methods. The results, shown in Figure 14, indicate that the multi-site assay herein detects more VEGF in lung cancer samples than the two-site assay. 3.18 Levels of Serum VEGF in Diabetic Patients Serum VEGF levels in normal humans and in patients with NIDDM (Type I diabetes) and IDDM (Type II diabetes) were measured using the two-site ELISA (MAb 3.5F8 as coat and MAb A4.6.1 as detection agent) described above. Figure 15 shows that the levels of scrum VEGF in NIDDM and IDDM patients were higher than in normal patients using this assay. Since the multi-site assay detects more VEGF than the two-site assay in other diseased patients, it would be expected that the multi-site assay herein would be suitable for detecting elevated levels of VEGF in diabetic patients. 3.19 Specificity of PAb to VEGF versus PAb to DNase in Multi-site Assay The two-site and multi-site ELISAs were carried out as described above for normal human plasma samples. In addition, a multi-site was carried out using PAb to DNase rather than PAb to VEGF as coat reagent. All were at the 0.4 μg/ml concentration. Figure 16 and Table 14 show that the VEGF detected by multi-site VEGF assay is specific. Results from the ELISA using PAb to DNase plus MAb 3.5F8 show almost identical results as the ELISA using MAb 3.5F8 alone as capture reagent, with a slope of 1.04 (Fig. 16A). TABLE 14: Human EDTA Plasma Evaluated for VEGF Amounts Human EDTA plasma MAb 3.5F8 PAb to VEGF (0.4 PAb to DNase (0.4 (0.4 μg/ml) μg/ml) and MAb μg/ml) and MAb 3.5F8 (0.4 μg/ml) 3.5F8 (0.4 μg/ml) High matrix (pg/ml): 147.9 147.4 1 19.2 Low matrix (pg/ml): 12.8 18.3 12.5 Seven separate normal 61.1 164.0 59.5 human plasma donors 33.8 120.4 48.5 (pg/ml): 34.6 174.3 64.5 47.4 104.5 102.1 28.3 70.4 79.6 67.6 1 13.0 71.8 61.1 105.9 65.4 3.20 Summary of Prcfencd Assay and Results INTER-ASSAY Low 1 1 % High 8% PRECISION in Human EDTA Plasma ACCURACY 6 normal human EDTA plasma samples were spiked with high, mid and low concentrations of rhVEGF. Mean % recoveries were: Low Mid High 106% 1 13% 99% 4 normal human serum samples were spiked with a high concentration of rhVEGF. Mean % recovery: High 1 13% 3 rat EDTA plasma samples were spiked with high, mid and low concentrations of rhVEGF. Mean % recoveries in the quantitative range were: Low Mid High 82% 91 % 99% 4 female and 4 male Yorkshire pig EDTA Plasmas were spiked with high, mid and low concentrations of rhVEGF. rhVEGF quantitation below 12 pg/ml (endogenous VEGF measured) will be reported for information only (mean % recovery below 12 pg/ml is approximately 60%). Mean % recoveries in the quantitative range were: Low Mid High n/a 86% 107% LINEARITY AND rhVEGF was spiked into 6 different normal human EDTA plasma INTERFERENCE samples Samples were serially diluted V to cover the range ot the standard curve 4 dilutions were made trom each sample rhVEGF values obtained were plotted against 1/dιlutιon and the correlation coefficient (R ) ot a linear regression analysis was calculated Samples were linear across the range ot the standard curve Mean R 2^ 0996 0005 rhVEGF was spiked in 3 rat EDTA plasma samples at high, mid and low concentration Samples were linear across the high and mid quantitative range n Mean R 2 SD Spike 3 0 998 0 002 High 3 0 967 0 034 Low rhVEGF was spiked into 8 EDTA pig plasma samples and serially diluted '/_ to cover the range ot the standard curve 4 dilutions were made trom each sample Samples were linear across the range of the standard curve n Mean R 2 SD 8 1 0 001 SAMPLE STABILITY 5 normal EDTA plasma samples were tested for treeze-and-thaw stability Human EDTA plasma is stable tor 3 freeze-and-thaw cycles Mean % recoveries I X 101 % 2X 101 % 3X 93% RUGGEDNESS/ pH profile indicates that the multi-site assay can tolerate pH's ranging ROBUSTNESS from 6 9 No quantitation of rhVEGF at pH 4 and 5 No ef fect on sample quantitation between a 1 5 and 16 hour sample incubation (% dif ference in control recover H Ctrl 19%, L ctrl 16%) Assay performed at room temperature No effect on temperature incubation ( 1 hour vs overnight at 37°C) in VEGF quantitation of human plasma and serum samples Mean % recoveries 1 hour overnight serum 1 13% 121 % plasma 1 15% 1 13% 4. Discussion Little is known about the levels or the circulating forms of VEGF in normal individuals during growth, pregnancy, and old age or in pathophysiological disease states. Herein is described the development and characterization of a sensitive, high-throughput assay capable of measuring various isoforms of VEGF and their levels in human plasma. This assay represents an important tool for measuring VEGF levels in both normal individuals and in various disease states. The multi-site VEGF ELISA herein can measure 165/165, 165/1 10, 121/121 , and 1 10/1 10 VEGF variants equally well. With this assay, higher plasma VEGF was detected in normal donors ( 192 + 68 pg/ml, n=50). For the same 18 cardiovascular patients, a significantly higher plasma VEGF above normal donors was detected (279 + 157 pg/ml, n= 18, p <0.001 ). See Fig. 13. Indeed, monoclonal antibody MAb 3.5F8 plus affinity-purified polyclonal antibody against an irrelevant protein did not generate any additional signal above that of MAb 3.5F8 alone. It is concluded that besides intact VEGF, other VEGF variants and isoforms are present in the circulation of both normal donors and cardiovascular patients. Ability to demonstrate that the receptor binding domain of VEGF is accessible for binding may be an important feature for any assay intended to understand the biological activity of VEGF in the circulation. The fluorometric substrate, strep-β-gal/MUG, is preferred for use in the detection system so that the ELISA can detect endogenous VEGF levels in normal individuals. The use of this substrate and the determination of the best ELISA diluent resulted in much lower background absorbance, which was preferred to achieve the increase in the assay sensitivity. The multi-site ELISA described herein is highly specific due to the choice of antibodies used for capture and detection. One of the coat antibodies, MAb 3.5F8, binds near the heparin binding region of VEGF (residues 1 1 1- 165) and the other coat antibody, the rabbit polyclonal antibody binds VEGF. The detection antibody, MAb A4.6.1 , binds in the KDR receptor binding region (residues 1-1 10) of the molecule, yielding a specific ELISA for VEGF. The specificity of this multi-site ELISA will be important as the biology of VEGF is better understood. Keyt et al., supra (p.7788) have demonstrated that the different VEGF variants examined in this study have varying bioactivities in vitro. Knowledge of assay specificity will also be extremely important in evaluating clinical data and comparing data between laboratories. Published reports (Kondo et al. , supra ( 1994); Takano et al. , supra ( 1996); Rodriguez et al. , supra) have noted that serum VEGF levels were elevated in cancer patients. Considering that angiogenesis is a general phenomenon in solid tumor progression, and that expression of VEGF, a tumor angiogenesis factor, is observed in a wide variety of tumor cells of various origins, measurement of circulating VEGF levels has potential as a non- invasive diagnostic marker for a wide spectrum of solid tumors. In conclusion, a sensitive ELISA that measures most molecular forms of VEGF has been developed. In accordance with the present invention, antibodies are raised in animals against human VEGF, with the C-terminal specific antibody being a monoclonal antibody and the whole-VEGF-specific antibody being a polyclonal antibody, preferably affinity purified. These two antibodies are used as coat antibodies (immobilized capture reagents) on a solid support such as microtiter plates. The antibody used for detection can be either polyclonal antibodies or monoclonal antibodies provided they are specific for the KDR and FLT1 binding domain regions of human VEGF. Accurate and sensitive ELISAs like the one described herein are deemed important in helping to understand VEGF levels in various disease states. A better understanding of both VEGF levels and the dominant isoforms present in both normal individuals and in pathophysiological disease states will enhance knowledge of the role of VEGF in normal and pathologic angiogenesis. While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as follows in the scope of the appended claims.

Claims: WHAT IS CLAIMED IS: 1. A method for detecting vascular endothehal growth factor (VEGF) in a biological sample comprising the steps of: (a) contacting and incubating the biological sample with pre-mixed capture reagents immobilized to a solid support, wherein the capture reagents are polyclonal and monoclonal antibodies against human VEGF, said monoclonal antibody binding specifically to the C-terminal (residues 1 1 1- 165) of human VEGF; (b) separating the biological sample from the immobilized capture reagents; (c) contacting the immobilized capture reagents with a detectable antibody that binds to the KDR and FLT1 receptor binding domains of VEGF; and (d) measuring the level of VEGF bound to the capture reagents using a detection means for the detectable antibody. 2. The method of claim 1 , wherein the biological sample is isolated from a human subject. 3. The method of claim 2, wherein the human subject is a vascular, diabetic, or cancer patient and the measuring step (d) further comprises a comparison with a standard curve to determine the level of VEGF compared to a normal individual. 4. The method of claim 1 , wherein the biological sample is plasma, serum or urine. 5. The method of claim 1 , wherein the capture reagents are immobilized in a weight ratio of about 0.8: 1 to 1.2: 1 of monoclonal to polyclonal antibody. 6. The method of claim 5, wherein the weight ratio is about 1 : 1 of monoclonal to polyclonal antibody. 7. The method of claim 6, wherein the amount of monoclonal antibodies immobilized is about 0.4 μg/ml and the amount of polyclonal antibodies immobilized is about 0.4 μg/ml. 8. The method of claim 1 , wherein the immobilized capture reagents are coated on a microtiter plate. 9. The method of claim 1 , wherein the detectable antibody is directly detectable. 10. The method of claim 9, wherein the detectable antibody is amplified by a fluorimetric reagent. 1 1. The method of claim 10, wherein the detectable antibody is biotinylated and the detection means is avidin or streptavidin-β-galactosidase and 4-methylumbelliferyl-β-galactoside. 12 The method of claim 1 wherein the immobilized monoclonal antibody is murine and the immobilized polyclonal antibody is rabbit or goat 13 The method of claim 1 , wherein the immobilized polyclonal antibody is affinity purified 14 The method of claim 1 , wherein the detectable antibody is a monoclonal antibody 15 The method of claim 14, wherein the detectable antibody is a murine monoclonal antibody 16 The method of claim 15, wherein the immobilized monoclonal antibody is MAb 3 5F8 and the detectable antibody is MAb A4 6 1 17 An immunoassay kit for detecting vascular endothehal growth factor (VEGF) in a biological sample, the kit comprising (a) as capture reagents, polyclonal and monoclonal antibodies against human VEGF premixed in a weight ratio of about 0 8 1 to 1 2 1 of monoclonal to polyclonal antibody wherein the monoclonal antibody binds specifically to the C-tcrminal (residues 1 1 1- 165) of human VEGF, and (b) as detection reagent, a detectable antibody that binds to the KDR and FLT1 receptor binding domains of VEGF 18 The kit ot claim 17, further comprising a solid support tor the capture reagents 19 The kit ot claim 18, wherein the capture reagents are immobilized on the solid support 20 The kit ol claim 19, wherein the capture reagents arc coated on a microtiter plate 21 The kit of claim 17, further comprising a detection means tor the detectable antibodies 22 The kit of claim 21 , wherein the detection means is fluorimetric 23 The kit ot claim 17, further comprising purified VEGF as an antigen standard 24 The kit of claim 17, wherein the weight ratio of monoclonal antibody to polyclonal antibody is about 1 1 , the monoclonal antibody is murine, the polyclonal antibody is affinity purified, and the amount of monoclonal antibodies is 04 μg/ml and the amount of polyclonal antibodies is 04 μg/ml 25 The kit of claim 24, wherein the capture reagents are immobilized and the polyclonal antibody is a rabbit or goat antibody 26. The kit of claim 25, wherein the detectable antibody is murine monoclonal antibody MAb A4.6.1 and the capture reagent monoclonal antibody is MAb 3.5F8.

Inventors: FEI DAVID TAI WAI, TOMITA KRISTEN K, FEI, DAVID, TAI, WAI, TOMITA, KRISTEN, K.
Applicants: FEI DAVID TAI WAI, GENENTECH INC, TOMITA KRISTEN K, FEI, DAVID, TAI, WAI, GENENTECH, INC., TOMITA, KRISTEN, K.
Application year: 2000
Main classification: G01N33
IPC codes: G01N21, G01N33