The Role of Disulfide Bridges in the Interaction of E. coli -Derived Recombinant SCARB2 and EV-A71's Capsid.

Background: Hand, Foot, and Mouth disease is an acute infectious disease caused by a group of enteroviruses, including Coxsackievirus A16 and Enterovirus 71. EV-A71-causing disease can give rise to severe complications in children, leading to meningitis, encephalitis, and even death. A potential approach to prevent the virus spread is inhibiting the invasion of EV-A71 into target cells, thereby helping to prevent not only the spread of EV-A71 in the community but also lessen the risk of outbreaks. EV-A71 cell's receptor, human scavenger receptor class B member 2, SCARB2, was used as a trap to gather the virus and limit its spreading.

Methods: In this study, the recombinant receptor was expressed using Escherichia coli (E. coli) system. SCARB2 proteins expressed from E. coli BL21(DE3), and E. coli SHuffle^® T7 Express were in inclusion bodies and subsequently refolded into soluble forms with recovery efficiencies of 57.57, and 82.2%, respectively. The presence of intramolecular disulfide bridges in the refolded SCARB2 was examined by SDS-PAGE in combination with Dithiothreitol (DTT). The two proteins were then utilized to evaluate the interaction with EV-A71 capsid by Indirect Enzyme-Linked Immunosorbent Assay (ELISA) at different pH levels to compare the adhesion efficiency.

Results: The results showed that SCARB2 protein expressed from E. coli SHuffle^® T7 Express with disulfide bond modifications had better adhesion to the viral capsid. Notably, when the medium pH was lowered to acidic levels, the binding efficiency of recombinant receptors to the viral capsid increased.

Conclusion: To our knowledge, this study reported for the first time the activity of SCARB2 under extreme pH conditions and also revealed the crucial role of disulfide bridges in the interaction with EV-A71's capsid. This finding contributed to the strategy using recombinant SCARB2 as a viral trap.