FIG. 6.

Conservation of MSP-2 CD4⁺-T-cell epitopes between A. marginale and the A. centrale vaccine strain. MSP-2-specific cell lines from each of three calves (A, animal 59; B, animal 60; and C, animal 61) were stimulated with a 30-mer peptide representing A. marginale MSP-2 amino acids 312 to 341 (Am P12) previously shown to contain a CD4⁺-T-cell epitopes (3), an 18-mer peptide representing A. marginale MSP-2 amino acids 324 to 341 (Am P12₁₈), an 18-mer peptide representing the same region but with a single amino acid substitution in A. centrale MSP-2 (Ac P12₁₈), or a 30-mer peptide representing an A. marginale sequence that does not contain a T-cell epitope (P1 [3]). All peptides were tested over a concentration range of 0.4 to 10 μg per ml. The results are presented as mean counts per minute of replicate cultures ± 1 standard deviation.