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

## TL;DR

This paper identifies a specific antibody region that binds to keratan sulfate and creates a smaller version for imaging in tissues.

## Contribution

The study identifies a KS paratope and expresses a functional single-chain antibody for imaging.

## Key findings

- The KS paratope was identified from the anti-KS IgG mAb MZ15.
- A functional ScFv was expressed and purified in E. coli.
- The ScFv enabled in vitro imaging of KS in rat cornea sections.

## Abstract

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.