Lineage specific antigenic differences in porcine torovirus hemagglutinin-esterase (PToV-HE) protein

Abstract

Hemagglutinin-esterases (HE) are viral envelope proteins present in some members from the toro-, corona- and orthomyxovirus families, all related with enteric and/or respiratory tract infections. HE proteins mediate reversible binding to sialic acid receptor determinants, very abundant glycan residues in the enteric and respiratory tracts. The role of the HE protein during the torovirus infection cycle remains unknown, although it is believed to be important in the natural infection process. The phylogenetic analysis of HE coding sequences from porcine torovirus (PToV) field strains revealed the existence of two distinct HE lineages. In a previous study, PToV virus strains with HE proteins from the two lineages were found coexisting in a pig herd, and they were even obtained from the same animal at two consecutive sampling time points. In this work, we report antigenic differences between the two HE lineages, and discuss the possible implications that the coexistence of viruses belonging to both lineages might have on the spread and sustainment of PToV infection in the farms.

Recent Progress in Torovirus Molecular Biology

“…The HE gene of BToV can be genetically divided into two lineages, the BRV and B150 lineages [ 53 , 89 ]. A full-length genome analysis of five PToVs showed that they can be divided into two lineages, the Malkelo and P4 lineages, based on the HE gene [ 80 , 90 , 91 ], but not other genes [ 53 ] ( Figure 3 b). The two lineages may have been separated by an HE recombination event [ 89 ], and their common ancestor reportedly emerged 56 years ago [ 80 ].…”

Porcine Torovirus (PToV)—A Brief Review of Etiology, Diagnostic Assays and Current Epidemiology

“…It is a class I membrane protein, and a member of the receptor destroying enzyme (RDE) protein family. There are two main domains identified in the monomer: the enzymatic acetyl-esterase region (E); and the receptor binding or lectin domain (25). The HE protein specifically but reversibly binds to mucopolysaccharides, mediating adhesion of virions to the intestinal wall.…”

“…It could be seen that this ELISA method had a high sensitivity, but its specificity may be slightly worse. The indirect ELISA based on PToV-HE protein is less sensitive and may have false negative results because of the diversity of HE proteins and the antigenic differences between HE lineages (14, 25). Development of other ELISA diagnostic methods based upon the PToV S protein is needed, according to experiences from porcine coronavirus such as porcine epidemic diarrhea virus (PEDV) (41).…”

Activation of the autophagy pathway by Torovirus infection is irrelevant for virus replication

“…the RNAdependent RNA polymerase [RdRp] and the helicase [Hel] amongst others) [1,10,14,15]. The rest of the viral genome harbors ORFs encoding structural proteins: spike (S) [16,17], membrane (M) [18,19], hemagglutinin-esterase (HE) [20][21][22], and nucleocapsid (N) [14,23], which are individually expressed from a nested set of 3'-coterminal subgenomic mRNAs [11,24,25].Accumulating evidence from different positive-strand RNA viruses indicates that in this heterogeneous group of viruses, genome replication and transcription invariably occur in close association with highly modified cellular membranes of diverse origins [26][27][28]. In fact, the presence of double membrane vesicles (DMVs) in the cytoplasm of cells infected with different nidoviruses has been associated with the formation of their replication and transcription complexes (RTCs) [29][30][31][32][33][34][35].…”

“…the RNAdependent RNA polymerase [RdRp] and the helicase [Hel] amongst others) [1,10,14,15]. The rest of the viral genome harbors ORFs encoding structural proteins: spike (S) [16,17], membrane (M) [18,19], hemagglutinin-esterase (HE) [20][21][22], and nucleocapsid (N) [14,23], which are individually expressed from a nested set of 3'-coterminal subgenomic mRNAs [11,24,25].…”