Complete S1 glycoprotein analysis of two distinct groups of GI-19 (QX) infectious bronchitis virus from Indonesia: Molecular phylogenetic and in-silico approaches

Abstract

Infectious bronchitis (IB) is an important viral disease that impacts poultry productivity, according to many studies. The main important infectious bronchitis virus (IBV) protein, spike glycoprotein subunit 1 (S1), plays a role in pathogenicity and immunogenicity. Conventional molecular detection and analysis of the S1 gene still face many challenges due to its hypervariability. In Indonesia, there were only a few reports on partial S1 gene analysis of IBVs; thus far, there have been no phylogenetic or in-silico approaches to their S1 complete gene. This study aims to reveal molecular pathogenicity and immunogenicity features on the S1 complete gene of IBVs from Indonesia. We analyzed fourteen IBV isolates using conventional RT-PCR and Sanger sequencing and then aligned their verified S1 complete sequences with other Indonesian GI-19 IBVs from Genbank for molecular phylogenetic and in-silico analysis. Phylogenetic analysis consisted of amino acid polymorphism and identity, as well as phylogenetic tree construction. As part of the in-silico analysis, we used proteins that have homology and immunoinformatic predictions (B-cell epitope and N-glycosylation). Molecular phylogenetic analysis revealed the division of the Indonesian GI-19 IBVs into two distinct groups. These groups had different amino acid variations at receptor binding sites, hypervariable antigenic sites, and cleavage sites. We also calculated the amino acid identity at 95.4–98.3%. In-silico studies revealed significant similarities in B-cell epitopes, distinct N-glycosylation sites, and the suggestion of a homotrimer protein structure. We found that the S1 full gene of two different groups of GI-19 IBVs (QX strain) from Indonesia predicted changes in their pathogenicity and immunogenicity.