Structure-function studies of an anti-asialo GM1 antibody obtained from a phage display library

Although gangliosides elicit human autoantibodies, they are extremely weak immunogens in mice. We obtained a monoclonal antibody Fab fragment (clone 10) that is specific for asialo GM1 (GA1), from a phage display library. The Vkappa domain of clone 10 could be replaced by two different Vkappa domains without changing the specificity of the antibody. Mutagenesis of the third hypervariable regions of the heavy and light chains of clone 10 yielded three mutants that exhibited a 3 to 4 times increase in avidity for GA1. A molecular model of clone 10 indicated that the putative antigen-binding site contained a shallow surface pocket. These data illustrate the use of recombinant DNA techniques to obtain anti-ganglioside antibodies, and to explore the molecular basis of their antigen-binding activity.