Comparison of immune reactivity to polyvalent monomeric and polymeric ragweed antigens

The proteins of an aqueous extract of ragweed pollen (RW) were precipitated at 90% saturation with (NH4)2SO4, solubilized, and sieved through Sephadex G-15. The excluded fraction, termed the monomeric form (MRW), was cross-linked with glutaraldehyde to form polymerized ragweed (PRW). As compared with MRW, PRW is more immunogenic in rabbits in the production of antibody against RW antigen E (AgE). MRW and PRW resulted in equal peak reaginic responses in rabbits but the duration of reagin production was longer after immunization with MRW than with PRW. Both MRW and PRW have exposed antigenic determinants of AgE but PRW had approximately 1/3 the number as shown by neutralization of human antibody against RW AgE. PRW had 100-to 1,000-fold less human cutaneous reactivity than MRW. PRW may be a more easily effective therapeutic agent for human RW immunotherapy than currently used aqueous extracts and may be more readily obtainable than polymerized AgE.