Structural characterization of viral glycoprotein GP2a, GP3, and GP4 of Porcine Reproductive and Respiratory Syndrome Virus

Abstract

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is one of the most economically significant pathogens in the pork-producing industry worldwide. PRRSV is a major player in the porcine respiratory disease complex, which affects swine of all ages and which can result in reproductive failure in sows. PRRSV is single-stranded, positive sense RNA virus. The virus encodes seven glycoproteins, of which four are envelope glycoproteins namely, GP2a (ORF2a), GP3 (ORF3), GP4 (ORF4), and GP5 (ORF5). Currently, there is little information about the three-dimensional structure of the glycoproteins, their interaction with each other, and the virion formation. The results from a few studies point toward an essential role for GP2a/GP4 and GP3 in PRRSV assembly; however, very little is known about the function of these minor structural proteins. We hypothesize that the formation of a complex of GP2a, GP3, and GP4 alters the three-dimensional structure of these proteins, resulting in limited access to neutralizing epitopes on GP2a, GP3, and GP4. The purpose of this study is to shed light on the three-dimensional structure of the glycoproteins as part of a complex and by themselves. Two different expression systems were used to express and purify the ectodomains of the glycoproteins thought to be important in the complex formation. Nuclear magnetic resonance spectroscopy (NMR) was used to test folding of these ectodomains to enable three-dimensional structure prediction using computational bioinformatics.