# Soluble expression of recombinant coagulation factor IX protein using Escherichia coli

## TL;DR

This paper presents a method to produce a soluble recombinant factor IX protein in E. coli for detecting anti-FIX antibodies in hemophilia B patients.

## Contribution

A novel method for expressing full-length, soluble recombinant FIX without fusion tags in E. coli is developed.

## Key findings

- rFIX was produced in a soluble form within five days without fusion tags.
- ELISA confirmed rFIX's high affinity and sensitivity for detecting anti-FIX antibodies.

## Abstract

Hemophilia B is a congenital bleeding disorder caused by factor IX (FIX) deficiency. Generation of recombinant FIX (rFIX) is required for detecting a Hemophilia B indicator, anti-FIX antibody. In this study, we described a method for producing recombinant FIX (rFIX) using Escherichia coli. We constructed a FIX-expressing plasmid without a fusion tag protein-encoding gene and produced rFIX as a soluble form within five days. Dose-dependent curve was obtained from ELISA using anti-FIX antibody, indicating that the rFIX can be used as an antigen to detect anti-FIX antibody with high affinity and sensitivity.

•Generation of a recombinant factor IX (rFIX) to compensate for detecting anti-FIX antibody in patients with hemophilia B.•Expression of a soluble form of full-length rFIX with no fusion sequence.•Confirmation of the binding efficiency of rFIX to anti-FIX antibody.

Generation of a recombinant factor IX (rFIX) to compensate for detecting anti-FIX antibody in patients with hemophilia B.

Expression of a soluble form of full-length rFIX with no fusion sequence.

Confirmation of the binding efficiency of rFIX to anti-FIX antibody.