Infectious bronchitis (IB) is an acute, highly contagious, and economically important viral disease of chickens. The S۱ subunit from Spike (S) protein plays the major role in protective immunity and is involved in the host-virus interactions, as well as infectious bronchitis virus (IBV) serotyping. Aim of the present study was multi-aspect analysis of the molecular and immunological features of ۵' part belonging to the
S۱ glycoprotein sequence of Iranian ۷۹۳/B IBV strain isolates. This might ideally help in characterization, prevention, and vaccine development. The tissue samples were prepared, followed by virus isolation, reverse transcription polymerase chain reaction and restriction fragment length polymorphism analysis. In addition, sequencing and registration of the sequences in the National Center for Biotechnology Information were performed. Moreover, ۱۲ sequences were retrieved from Fars province, Iran. The next steps included evaluation of conservation/variability along the sequences, phylogenetic analysis, estimation of the average evolutionary divergence over all the sequence pairs, predicting the phosphorylation/N-glycosylation/palmitoylation sites, and the final analysis of antigenicity. The findings of alignment, entropy plot, and pairwise similarity analysis revealed ۱۷ hypervariable regions. The isolates belonging to Tehran were clustered in phylogenetic tree, and the most similar isolates to them were ADW۱۱۱۸۲ and ADW۱۱۱۸۳. Location of some of the N-glycosylation/phosphorylation/palmitoylation points indicated that these sites were conserved among the isolates. Furthermore, the frequency of epitopes and their scores reflect the high immunogenicity of S۱ protein in ۷۹۳/B serotype. Analysis of the primary and secondary structures demonstrated that their parameters had variable values and were different regarding the number and location of α-helix, β-strand, and coils. According to our findings, the Iranian isolates of
۷۹۳/B serotype change their molecular characteristics during time and in different geographical regions. These alterations might account for failure in prevention programs and differences in virulence and pathogenicity.