Development of a Monoclonal Antibody Against Porcine CD163 SRCR5 Domain Which Partially Blocks Infection of PRRSV.

Yujiao Zhang,Guoxin Li,Wu Tong,Changlong Liu,Lingxue Yu,Liwei Li,Hao Zheng,Nannan Du,Guangzhi Tong,Fei Gao,Yanjun Zhou,Kuan Zhang,Yifeng Jiang,Kuan Zhao

doi:10.3389/fvets.2020.597843

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV), which seriously endangers the world pig industry, invades host cells through receptor-mediated endocytosis involving clathrin. CD163 is an essential receptor for PRRSV during its infection of cells. The scavenger receptor cysteine-rich 5 (SRCR5) domain of the CD163 molecule is necessary for PRRSV infection, and interacts with glycoproteins GP2a and GP4 of PRRSV, allowing the virus to infect the host cells. In this study, a monoclonal antibody (mAb) against the SRCR5-6 region of porcine CD163 was developed, and the target epitope of the mAb was determined as 497TWGTVCDSDF506, which is directly adjacent to the ligand-binding pocket (LBP) domain (487-495aa) of CD163. Further study indicated that the mAb could partially block PRRSV infection of its target cells, pulmonary alveolar macrophages. The mAb developed in the study may provide a foundation of antiviral therapy for PRRSV.

Highlights

CD163 is a member of the scavenger receptor cysteine-rich (SRCR) family, and is mainly expressed on monocytes, macrophages [1], and specific subsets of dendritic cells [2]
Because CD163 scavenger receptor cysteine-rich 5 (SRCR5) and SRCR6 are relatively conserved and are important for Porcine reproductive and respiratory syndrome virus (PRRSV) infection, a recombinant His-fused CD163 SRCR5-6 protein was successfully expressed in E. coli BL21(DE3) cells (Figure 1B)
The protein was expressed both in the cell supernatant and as inclusion bodies, but the His-fused CD163 SRCR5-6 protein was mainly present as inclusion bodies

Summary

Introduction

CD163 is a member of the scavenger receptor cysteine-rich (SRCR) family, and is mainly expressed on monocytes, macrophages [1], and specific subsets of dendritic cells [2]. CD163, as a receptor that scavenges hemoglobin by mediating the endocytosis of haptoglobin-hemoglobin complexes during haemolysis [3] and plays a role as an innate bacterial immune sensor, inducing pro-inflammatory cytokine production [4]. The abundance of CD163 is closely related to HIV infection, and the productivity of HIV infection was higher in CD163 abundant cells, whereas a significantly weaker HIV infection was observed in CD163-knocked-down macrophages [6]. The interaction between CD163 and the virus is important, and has been extensively studied in relation to Porcine reproductive and respiratory syndrome virus (PRRSV) [7] and African swine fever virus [8], both of which have devastating impacts on the swine industry.

Methods

Results

Conclusion