The present invention provides a method of classifying an epitope displayed by a polypeptide; a method of determining the presence of an epitope on a polypeptide encoded by a test nucleotide sequence; and a method of generating a nucleotide sequence encoding a polypeptide that exhibits a selected epitope. The present invention provides antigenic polypeptides that display selected epitope(s); chimeric macromolecules comprising such polypeptides; and compositions comprising the antigenic polypeptides or chimeric macromolecules. The present invention further provides methods of inducing an immune response to a Chlamydia. The present invention further provides arrays of nucleic acids, arrays of polypeptides, and arrays of antibodies, which arrays are useful in identification and/or classification of a Chlamydia.