Nucleotide Sequence Analysis of S1 Gene among Iranian Avian Infectious Bronchitis Viruses Isolated during 2001-2002

Document Type: Original Articles


1 Department of Veterinary Research and Biotechnology, Razi Vaccine and Serum Research Institute, Agricultural Research, Education, and Extension Organization, Mashhad, Iran

2 Department of Poultry Disease Research and Diagnosis, Razi Vaccine and Serum Research Institute, Agricultural Research, Education, and Extension Organization, Karaj, Iran


Infectious bronchitis (IB) virus genome codes for four structural proteins, among which the S1 subunit of spike glycoprotein comprises the major epitopes to induce neutralizing antibodies. This study involved the comparison of the full S1 sequences of five IB viruses, namely two Massachusetts and three 793/B serotypes, isolated from IB outbreaks during 2001-2002, with all other Iranian and foreign 793/B isolates and 10 known serotypes. Analysis of S1 subunit showed three unique amino acid changes at positions 349 (V to L), 392 (T to N), and 393 (Q or R to T or K or S) for the Iranian 793/B isolates, compared to those of the foreign 793/B isolates reported before 2006 (onset of vaccination with 793/B vaccine in Iran). They were used as amino acid markers for the differentiation of Iranian 793/B isolates for years. Sequence alignment of the Iranian isolates with those of the foreign ones reported after 2006 demonstrated that amino acids 392 and 393 were no longer considered as amino acid markers, and only the change in amino acid 349 still remained specific to the Iranian 793/B isolates. Phylogenetic tree sequence analysis revealed that the Iranian 793/B isolates were closely related indicating that they came from a single source, more probably from France. There was a very close correlation between the first detection of 793/B serotype and the time of French chicken meat importation. Moreover, it was shown that one of the Massachusetts isolates was completely identical with the H120 vaccine strain. Furthermore, the other Massachusetts isolate with two amino acid changes at positions 64 (G to E) and 95 (S to R) was very similar to this vaccine strain. It seems that the latter isolate is a passaged chicken H120 vaccine strain.


Main Subjects

Article Title [French]

Analyse de la Séquence Nucléotidique du Gène S1 Parmi les Virus de la Bronchite Infectieuse Aviaire Isolés en Iran entre 2001 et 2002

Abstract [French]

Le génome du virus de la bronchite infectieuse (BI) code quatre protéines structurelles, parmi lesquelles la sous-unité S1 de la glycoprotéine de Spike comprend les principaux épitopes permettant d'induire des anticorps neutralisants. Cette étude a pour objectif de comparer les séquences S1 complètes de cinq virus de BI, à savoir deux sérotypes Massachusetts et trois sérotypes 793/B, isolés des foyers d'infection épidémique de BI entre 2001 et 2002, avec tous les autres isolats 793/B iraniens et étrangers ainsi que 10 sérotypes connus. L'analyse de la sous-unité S1 a montré trois changements uniques des acides aminés aux positions 349 (V à L), 392 (T à N) et 393 (Q ou R à T ou K ou S) pour les isolats iraniens 793/B, comparés rapport à ceux des isolats étrangers 793/B signalés avant 2006 (début de la vaccination par le vaccin 793/B en Iran). Ils ont été utilisés comme acides aminés marqueurs afin de différencier les isolats iraniens 793/B pendant des années. L'alignement des séquences des isolats iraniens avec celles des isolats étrangers signalés après 2006 a montré que les acides

aminés 392 et 393 n'étaient plus des acides aminés marqueurs et que seulement le changement de l'acide aminé 349 demeurait spécifique aux isolats iraniens 793/B. La reconstruction de l'arbre phylogénétique a partir des séquences obtenues a révélé que les isolats iraniens 793/B étaient étroitement liés, indiquant qu'ils provenaient d'une source unique, plus probablement de France. Il existait en effet une corrélation très étroite entre la première détection du sérotype 793/B et la periode de l'importation de la viande de poulet française. De plus, il a été démontré qu'un des isolats du Massachusetts était complètement identique à la souche vaccinale H120. De plus, l'autre isolat du Massachusetts avec deux changements d'acide aminé aux positions 64 (G à E) et 95 (S à R) était très similaire à cette souche vaccinale. Il semble que ce dernier soit une souche vaccinale H120 de poulet ayant subi plusieurs passagesé.

Keywords [French]

  • Virus de la bronchite infectieuse
  • Sérotype 793/B
  • Gène S1
  • d'Acide aminé marqueur
  • Analyse phylogénétique
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