Anti-idiotypic antibodies have been successfully used to identify and isolate the receptor for several cell
ligands. To prepare an immunologic probe for identification of the polyomavirus receptor on mouse kidney cells, polyclonal
antisera against antipolyomavirus
antibodies were prepared in rabbits.
Fab fragments of the previously characterized
monoclonal antibody E7, which neutralizes
polyomavirus infection, were used for immunization (S. J. Marriott and R. A. Consigli, J. Virol. 56:365-372, 1985). Sera containing the greatest anti-idiotype activity were identified by
enzyme-linked
immunosorbent assay (ELISA) and purified by a series of affinity columns. The
anti-idiotypic antibodies recognized the E7 idiotope in an ELISA, and anti-idiotype binding could be inhibited by preincubation of E7
monoclonal antibody with polyomavirus virions. When mixed with anti-
idiotype immunoglobulin G (
IgG), E7 was no longer capable of binding or immunoprecipitating polyomavirus virions or neutralizing
polyomavirus infection. Direct immunofluorescence showed anti-idiotype
IgG reactivity with a cell surface component of mouse kidney cells. Anti-idiotype F(ab')2 effectively competed with polyomavirus for binding to mouse kidney cells and displayed binding kinetics similar to those of polyomavirus.
Virus infection of mouse kidney cells was blocked in a dose-dependent manner following treatment of the cells with anti-idiotype
IgG. The anti-idiotype identified several
proteins (95, 50, and 24 to 31 kilodaltons) in an immunoblot of mouse kidney
cell membrane proteins but reacted predominantly with a single 50-kilodalton
protein in a radioimmunoassay. The anti-idiotype failed to react with virus
proteins in three assays, including ELISA, immunoprecipitation, and immunoblotting. The implications of this work for future identification and characterization of the polyomavirus receptor on mouse kidney cells are discussed.