[Preparation of high-affinity monclonal antibody against hemoglobin delta globin chain and beta globin chain].

AIM: To prepare monclonal antibody (mAb) against both hemoglobin A2 (HbA2) and hemglobin A (HbA), this antiboy can bind to delta globin chain and beta globin chain, but not to gamma globin chain. METHODS: Mice was immunized with recombinant Hb delta fusion protein, and hybridoma cells were generated by cell fusion techniques followed by screening with natural HbA2 and HbA separated by ion exchange chromatography. The purified monclonal antibody was identified by indirect ELISA, Western blot based on native PAGE and SDS-PAGE, surface plasmon resonance (SPR), flow cytometry and immunohistochemistry. RESULTS: The monoclonal antibody against both HbA2 and HbA was obtained and designated as 2C9 that shows no binding to fetal hemoglobin (HbF), alpha globin chain and recombinant zetaglobin chain. CONCLUSION: The mAb 2C9 was defined as specificity to hemoglobin delta globin chain and beta globin chain, which suggests that mAb 2C9 recognizes a common epitope on bothdeltaglobin chain and beta globin chain. This antibody would be expected to be an effective tool in research and clinical practice in hemoglobinopathies.

Sandwich ELISA for hemoglobin A2 quantification and identification of beta-thalassemia carriers.

Hemoglobin (Hb) A2 (alpha2delta2) is a minor hemoglobin in human red blood cells. An abnormal increase in the level of HbA2 is the most significant parameter in the diagnosis of beta-thalassemia carriers. In this study, we produced two monoclonal antibodies (mAbs) that specifically react to the delta-globin chain of HbA2. A sandwich type ELISA was developed employing the produced anti-HbA2 mAbs. HbA2 levels quantified by the developed sandwich ELISA were highly correlated with those obtained from the standard HPLC method (r = 0.934, p < 0.001). HbA2 levels determined by the ELISA were 4.4 +/- 1.9% in beta-thalassemia heterozygotes compared to 1.4 +/- 0.8, 1.9 +/- 0.8, 1.5 +/- 0.8 and 1.5 +/- 0.6% in normal subjects, HbE heterozygotes, suspected alpha-thalassemia heterozygotes and HbE homozygotes, respectively. Using a cut-off value of 2.5%, beta-thalassemia heterozygotes could be separated from non-beta-thalassemia heterozygotes with the same accuracy as obtained using the standard HPLC method. More importantly, the developed ELISA was able to determine HbA2 levels in HbE-bearing individuals which could not be done by the HPLC method. Our results suggest that this sandwich ELISA can be applied for mass screening for beta-thalassemia heterozygotes, especially in resource-limited countries, where beta-thalassemia is highly prevalent.

Generation and characterization of human delta-globin-specific monoclonal antibodies.

The human delta-globin chain, unique to the hemoglobin A2 (HbA2) heterotetramer, is important for the evaluation of hemoglobinopathy. However, there are no well-defined antibodies specific for the delta-globin chain, a fact that is attributed a striking similarity (93%) in amino acid sequence between delta-globin and beta-globin of the hemoglobin A (HbA). In this study, two monoclonal antibodies (mAbs) against the delta-globin chain were generated and designated as 2H4 and 1H11. These antibodies were specific to HbA2 and do not cross-react with HbA and HbF (fetal hemoglobin). Moreover, the expression of HbA2 in fetal liver and mature erythrocytes was determined using these two mAbs. In addition to being useful tools for research or diagnosis, these antibodies could be valuable for development of rapid and effective antibody-based immunoassays of HbA2 expression in erythroid cells and non-erythroid tissue.

[Preparation and identification of monoclonal antibody against Homo sapiens hemoglobin alpha 2 (HBA2)].

This study was purposed to prepare and identify monoclonal antibodies (McAbs) against Homo sapiens hemoglobin alpha 2 (HBA2). Normal human fetal liver tissues were homogenized, and human liver nuclear proteins were isolated by centrifugation. The total human fetal liver nuclear proteins were used to immunize BALB/c mice for preparing McAbs by hybridoma technique. The McAbs specificity was identified by ELISA, Western blot, and immunohistochemistry. The antigen was identified by Uni-ZAP expression library screening. The results showed that one hybridoma cell line, AEE091, secreting specific McAb against HBA2 was established. The Ig subclass of this McAb was IgG1 (kappa). Data from immunohistochemistry assay showed that AEE091 could recognize human liver nuclear protein. Using AEE091 McAb, isolation of the protein antigen by IP revealed that AEE091 McAb could recognize 15 kD protein. Screening the Uni-ZAP XR pre-made liver cDNA library with AEE091 hybridoma cell supernatants demonstrated that AEE091 McAb specially reacted with HBA2. It is concluded that a hybridoma cell line stably secreting specific McAb against HBA2 is established. The specific McAb against HBA2 would be very useful for studying HBA2 function and screening thalassemia.

Development and validation of an ELISA for hemoglobin-A2: a novel method for beta-thalassemia screening in developing countries.

Hemoglobin-A2 (HbA2) measurement in human hemolysates has great significance, since its level can indicate beta-thalassemia carrier status in otherwise healthy individuals. An ELISA for HbA2 using antiserum monospecific to the delta chain of HbA2 and affinity purified antirabbit gamma globulins (ARGG) conjugated to horseradish peroxidase (HRP) have been developed. The monospecific antiserum used does not cross react with other hemoglobins. Hemolysates from volunteers are used for measurement of HbA2. In a limited trial for beta-thalassemia carrier screening (n = 350), the results obtained with the developed ELISA are comparable with those obtained with a micro-column chromatography method (r > or = 0.89). The developed ELISA is simple, accurate, precise, inexpensive, and several samples can be processed simultaneously with ease, making this system a suitable candidate for transforming into a user friendly kit.

Application of a monoclonal antibody specific for the delta chain of hemoglobin A2 in the diagnosis of beta thalassemia.

We have developed a murine monoclonal antibody (mAb) specific for the delta chain of hemoglobin (Hb) A2 that does not cross-react with alpha, beta, or gamma chains. The mAb reacted with Hb P-Nilotic (beta delta hybrid), but not with Hb Lepore-Boston (delta beta hybrid), indicating an epitope consisting of positions 116 (Arg) and 117 (Asn) or 125 (Gln) and 126 (Met) of the delta chain. By using this antibody, we have established a simple and rapid enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of Hb A2 in adult, cord, and fetal hemolysates. We analyzed 70 adult, 8 newborn, and 19 fetal hemolysates from normal subjects and those with various hemoglobinopathies. The mean percentage of Hb A2 was 2.5 for normal adults, 5.4 for beta thalassemic (beta thal) heterozygotes, and less than 0.1% in beta thal fetal samples. We were able to distinguish and characterize certain phenotypes of beta thal patients such as beta thal heterozygotes, beta 0 thal homozygotes, and C beta 0 thal, and C beta + thal double heterozygotes with the aid of this and other mAbs we have generated. This technique is a valuable addition to current methods for the diagnosis of beta thal based on quantification of Hb A2.