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. 2019 Sep 5;9(9):656.
doi: 10.3390/ani9090656.

Molecular and Antigenic Characterization of GI-13 and GI-16 Avian Infectious Bronchitis Virus Isolated in Chile from 2009 to 2017 Regarding 4/91 Vaccine Introduction

Miguel Guzmán  1   2 , Leonardo Sáenz  3 , Héctor Hidalgo  4
Affiliations

Molecular and Antigenic Characterization of GI-13 and GI-16 Avian Infectious Bronchitis Virus Isolated in Chile from 2009 to 2017 Regarding 4/91 Vaccine Introduction

Miguel Guzmán et al. Animals (Basel). .

Abstract

The introduction of the 4/91 vaccine against infectious bronchitis in Chile, a lineage not described until that time in the country, led to looking for changes induced by this action. This study considers eight isolates obtained from 2009, 2015 and 2017 and uses a maximum likelihood approach to classify the field isolates. Three isolates were selected to analyze antigenic relationships through a virus neutralization test and to perform protection tests measured trough an RT-qPCR. The isolates from 2009 and 2015 showed a relationship with GI-16 while those from 2017 were related to GI-13. Though the field isolates were classified in two different phylogenetic lineages, all of them showed only minor variations in subtype. The 13885R-17 isolate from 2017 exhibited high antigenic relatedness to the 4/91 vaccine. As expected, 4/91 and Massachusetts vaccines were not antigenically related. Vaccinated birds with the 4/91 vaccine showed less tracheal virus replication for the 13885R-17 from 2017 challenge than for the 12101SP-09 from 2009 and 13347SP-15 from 2015 isolates. The results indicated genetic and antigenic diversity in the most recent infectious bronchitis virus (IBV) isolates in Chile. Moreover, the 4/91 vaccine would be involved in the generation of some current field viruses, which must be considered in vaccination programs and public policies.

Keywords: 4/91 vaccine; RT-qPCR; antigenic relationship; infectious bronchitis; phylogenetic classification; protection test.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Phylogenetic tree performed by a maximum likelihood method with the PhyML platform v3.0 [26] based on complete S1 region of infectious bronchitis virus (IBV). Red lines indicate Chilean sequences. The tree is rooted in GII and GIV because they showed higher amino-acid distance from other genotypes. The numbers indicate the bootstrap supports of 1000 replicates; only internal nodes over 500 are shown.
Figure 2
Figure 2
Amino-acid comparison of Mass and 4/91 vaccines with field strains from 2009, 2015 and 2017 along the entire S1 sequence performed with Bioedit software v7.2.5 [27]. Dots indicate the same amino acid in that position compared to the 4/91 vaccine.
Figure 3
Figure 3
Results of Tukey’s multiple comparison test (p-value = 0.05). Intervals that do not overlap the dotted line indicate a significant difference between the Ct values of the RT-qPCR from different challenge strains.
See this image and copyright information in PMC

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