The mouse antibody response to Trichinella spiralis defines a single, immunodominant epitope shared by multiple antigens.

Immunoblot analysis was used to characterize the Trichinella spiralis L1 larval Ag recognized by antisera from T. spiralis-infected AKR/J mice. Antisera were analyzed for reactivity with crude worm extract, excretory/secretory proteins and cuticle proteins from L1 larvae. The response was biphasic; antibodies against one set of Ag were detected 13 days after infection (group I Ag), and antibodies against a different set of Ag were detected 35 days after infection (group II Ag). Excretory/secretory and cuticle proteins were recognized only by antibodies produced late in infection. The predominant isotype in day 42 antiserum was IgG1, and 80% of these IgG1 antibodies reacted with a stage-specific determinant shared by virtually all group II Ag. A mAb reactive with the shared determinant was used to purify the group II Ag from L1 larval extract. Such affinity-purified Ag were protective when used to immunize mice against subsequent infection, and T cells from infected mice proliferated when cultured with these Ag in vitro. Other mouse strains also made a strong serum antibody response to the group II Ag. We hypothesize that immune responses to the shared epitope play an important role in determining the outcome of the host-parasite interaction during infection.