Alignment of OspA221–240 epitope variants. The B. burgdorferi B31 OspA sequence corresponding to residues 221 through 240 served as the query sequence for a BLAST search. The major variants of the epitope identified through BLAST are presented as a standard amino acid alignment. Note that since species-specific variants were not evident, the OspA221–240 and OspB244–260 variants were assigned letter/number designations (“a” for OspA and “b” for OspB followed by a number; a # 1, a # 2, b # 1, b # 2, etc.). Residues that are identical to the B. burgdorferi B31 OspA221–240 reference sequence are indicated by (.).