Genetic control of antibody response to bovine rhodopsin in mice: epitope mapping of rhodopsin structure.

Inbred strains of mice of independent haplotype were immunized with bovine rhodopsin. All mice tested except SJL developed significant titers of specific antibodies 21 days after a single immunization. Anti-rhodopsin antibody level differed among conventional inbred strains. Comparison of the immune response to rhodopsin of congenic mice on two different genetic backgrounds showed that animals with an A background typically produced higher levels of specific antibody than mice with a B10 background. Titer of specific antibodies in antisera of mice of the same H-2 haplotype but different Igh haplotype differed; e.g. for H-2d haplotype, NZB (Ighn) generated the highest level of antibody with BALB/c (Igha), DBA/2 (Ighc), and B10.D2 (Ighb) strains giving successively lower responses. The location of immunodominant regions of bovine rhodopsin was investigated in primary sera among strains of mice. Sera were tested for their binding of anti-rhodopsin antibodies to synthetic peptides covering the entire primary structure of rhodopsin. From direct binding studies with hydrophilic rhodopsin peptides, the majority of the antigenic binding sites were localized in the sequence of the amino terminus, the II-III loop and the carboxyl terminus. Binding to these antigenic peptides was not strain restricted. Application of the overlapping synthetic peptide strategy of Geysen enabled refinement of these epitopes and determination of an additional major epitope in the hydrophobic sequence 304-310.