Methods for purifying and detecting IGM antibodies

A method of purifying IgM from a fluid sample obtained from a test subject not previously exposed to B. burgdorferi antigens which comprises:

• a) contacting said fluid sample with an affinity substrate comprising a solid substrate having immobilized thereon an outer surface protein (Osp) of Borrelia burgdorferi, wherein the contacting is performed under conditions favorable to binding IgM to the immobilized outer surface protein,
• b) contacting the affinity substrate obtained from step a) with a liquid which dissociates IgM from the immobilized outer surface protein, and
• c) recovering dissociated IgM.

A method for detecting IgM in a fluid sample suspected of containing IgM, said fluid sample obtained from a test subject not previously exposed to Borrelia burgdorferi antigens which comprises:

• a) contacting said fluid sample with a binding substance comprising an outer surface protein (Osp) of Borrelia burgdorferi, Borrelia burgdorferi cells, or cellular or extracellular components obtained or derived from said cells which contain said Osp, under conditions favorable to binding of IgM to said binding substance to form IgM-binding substance complexes, and
• b) detecting said complexes formed by means of a label conjugated to said binding substance or by means of a labeled reagent that specifically binds to said complexes subsequent to their formation.