Monoclonal antibodies recognizing single amino acid substitutions in hemoglobin

Abstract

Four monoclonal antibodies (mAb) to non-human primate hemoglobin referred to as Cap-4, Cap-5, Rh-2, and Rh-4, and two mAb to human hemoglobin, referred to as H-1 and H-3 were isolated and were partially characterized. Binding studies with these mAb on a panel of hemoglobins and isolated alpha and beta globin chains revealed a unique reactivity pattern for each mAb. Amino acid sequence analysis of the antigens used to generate the binding data suggests that the specific recognition of certain hemoglobin antigens by each mAb is controlled by the presence of a particular amino acid at a specific position within the epitope. The use of synthetic peptides as antigens confirmed this observation for five of the mAb. No synthetic peptides were tested with the sixth mAb, Rh-2. The amino acids required for binding of mAb Cap-4, Cap-5, Rh-4, and Rh-2 to hemoglobin are alanine at beta 5, threonine at beta 13, glutamine at beta 125, and leucine at alpha 68. The non-human primate hemoglobin antibodies require a specific amino acid that is not present in human hemoglobin. The amino acid required for binding of Cap-4, Cap-5, and Rh-4 could arise by a single base change in the beta globin gene, whereas the amino acid required for Rh-2 binding would only occur if two base changes occurred. Thus these mAb are candidate probes for a somatic cell mutation assay on the basis of the detection of peripheral blood red cells that possess single amino acid substituted hemoglobin as a result of single base substitutions in the globin genes of precursor cells.