Identification of an Immunoglobulin Paratope Binding to Keratan Sulfate and Expression of a Single-Chain Derivative for Imaging.

Keratan sulfate (KS) is a negatively charged carbohydrate linked to proteins. Several KS-bearing structural glycosaminoglycans participate to maintain the homeostasis of a functional extracellular matrix. Dysfunction of its biochemical composition and structure might therefore lead to pathological situations. For this reason, imaging of KS in tissues is an important diagnostic tool. Here, we describe the identification of the KS paratope derived from the ancestral anti-KS IgG mAb MZ15, as well as the engineering, functional recombinant expression in E. coli, and purification of an anti-KS single-chain variable fragment (ScFv). The ScFv enabled in vitro imaging of KS in cryosections of rat cornea by immunofluorescence microscopy comparable to the ancestral IgG MZ15.