Abstract: The present invention relates to nucleic acid molecules, polypeptides encoded by the same, antibodies directed thereto and a method of preparing such polypeptides including: (a) inserting an isolated DNA molecule coding for a polypeptide which is immunoreactive with a 66 kDa polypeptide derived from Borrelia garinii IP90 into an expression vector; (b) transforming a host organism or cell with the vector; (c) culturing the transformed host cell under suitable conditions; and (d) harvesting the polypeptide. The isolated DNA molecule is preferably at least 10 nucleotides in length, and the method may optionally include subjecting the polypeptide to post-translational modification. The host cell can be a bacterium, a yeast, a protozoan, or a cell derived from a multicellular organism such as a fungus, an insect cell, a plant cell, or a mammalian cell.