Cardiol. 51: 1653C1662. to assay apoAI and apoB-100 lipoproteins that have one or more OxCE epitopes. OxCE-apoA or OxCE-apoB did not correlate with the well-established oxidized phospholipid-apoB biomarker. In a cohort of subjects treated with atorvastatin, OxCE-apoA was significantly lower than in the placebo group, independent of the apoAI levels. These results suggest the potential diagnostic power of a new biomarker Raf265 derivative assay to measure OxCE-modified lipoproteins in patients with CVD. 0.05 were considered statistically significant. RESULTS Generation and characterization of OxCE mAb Four mice were immunized with OxCE-KLH Raf265 derivative and screened for Ab production by binding to OxCE-BSA (Fig. 1B). Hybridomas were generated from the spleens of the two mice with the highest IgG titers and supernatants screened for IgG binding to OxCE-BSA. Clone 23 was selected for its strong IgG binding to OxCE-BSA, but not BSA (Fig. 1C). To ensure the monoclonality of the Ab, it was subjected to a single cell dilution, and all daughter clones Raf265 derivative were positive for OxCE-BSA binding (Fig. 1D). The Ab, dubbed AG23, was sequenced (supplemental Fig. S1), expanded, and purified by contract research businesses as detailed in the Materials and Methods. The AG23 Ab stained OxCE-BSA, but not BSA, on a Western blot, while a control nonspecific IgG1 stained neither (Fig. 2A). AG23 binding to two other common oxidation-specific epitopes (OSEs), malondialdehyde (MDA)-altered LDL and oxidized phospholipid (OxPL) enriched in copper-oxidized LDL (CuOxLDL), was negligible (Fig. 2B). OxCE-KLH, but not KLH, competed with OxCE-BSA for AG23 binding (Fig. 2C), validating the specificity of the Ab to the OxCE epitope irrespective of the carrier protein. To further confirm the specificity of AG23 to the OxCE covalent modification of a protein, we altered the G6K peptide with OxCE, using the protocol utilized for the OxCE-BSA and OxCE-KLH modifications, and observed a strong AG23 binding to G6K-OxCE, but not unmodified G6K-OH (Fig. 2D). The OxCE modification procedure for the G6A peptide, in which alanine replaces the C-terminal lysine, was not expected to result in a covalent bond between OxCE and the peptide, and indeed AG23 did not bind to the G6A/OxCE reaction product (Fig. 2D). In a cross-competition assay, both OxCE-BSA and G6K-OxCE competed with each other for AG23 binding in a dose-dependent manner (Fig. 2E, F). Open in a separate windows Fig. 2. AG23 specificity to OxCE epitope. A: OxCE-BSA (a) and unmodified BSA (b) were loaded on a 4C12% Bis-Tris SDS gel at 0.5 g/well. The gel was stained with Coomassie Blue (CB) or blotted and probed with OxCE-specific AG23 mAb or a mouse anti-KLH IgG1. Representative gel and blots from 20 repeats. B: Representative results of AG23 (0.125 g/ml) binding to BSA, OxCE-BSA, MDA-LDL, and CuOx-LDL (5 g/ml). Four different OxCE-BSA preparations were tested in 12 impartial experiments with AG23 concentrations ranging from 0.125 to 1 1 mg/ml. The graph shows the mean Rabbit Polyclonal to HTR2B of three repeats, each in three technical replicates. Mean SD; one-way ANOVA with multiple comparisons; **** 0.0001. C: Competition ELISA: AG23 (0.01 g/ml) was preincubated in the absence or presence of increasing concentrations of nonmodified KLH or OxCE-KLH. Immune complexes were spun down, and supernatants were tested for binding to OxCE-BSA (5 g/ml). Each data point is the mean of two impartial assays in technical triplicates. D: AG23 (1 g/ml) binding to 10 g/ml of nonmodified G6K-OH and G6A-OH peptides, and the peptides subjected to the OxCE covalent modification. G6K-OxCE designates covalent Raf265 derivative modification of Lys, and G6A/OxCE designates the reaction that did not result in covalent modification of Ala. Mean SD; n = 6 for G6K and n = 2 for G6A, each in technical duplicates; one-way ANOVA with multiple comparisons; ** 0.01. E, F: AG23 (0.15 g/ml) was preincubated overnight with nonmodified (250 g/ml) or OxCE-modified (10C250 g/ml) BSA or G6K-OH peptide. Following spin down of immune complexes, supernatants were tested for binding with OxCE-BSA (E) or G6K-OxCE (F). Graphs show the results of a representative experiment performed in triplicate (E) or duplicate (F). G: OxCE plated at 1.25 g/well in a 96-well plate was incubated with or without cholesterol esterase (10 u/well) for 3 h at 37C. The solution was collected and pooled for free cholesterol measurements. After washes, AG23 binding to the wells was measured. Mean SD, n = 5; **** 0.05; ** 0.01. Unpaired = 0.293 between OxCE-apoB and OxCE-apoA suggests their limited covariation. OxCE-apoA did not correlate with HDL cholesterol (HDL-C). Remarkably, there was no correlation between OxPL-apoB [decided using the previously described assay (28)] and OxCE-apoB or OxCE-apoA. TABLE 1. Correlation matrix for OxCE-apoB and OxCE-apoA versus.