Preliminary comparative analysis of the genomes of selected field reisolates of the Mycoplasma synoviae vaccine strain MS-H reveals both stable and unstable mutations after passage in vivo

Somayeh Kordafshari,Pollob Shil,Barbara Konsak-Ilievski,Marc S Marenda,Amir H Noormohammadi,Olusola M Olaogun,Jillian Disint

doi:10.1186/s12864-020-06995-z

Somayeh Kordafshari, Pollob Shil + Show 5 more

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https://doi.org/10.1186/s12864-020-06995-z

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Journal: BMC Genomics	Publication Date: Aug 28, 2020
Citations: 5	License type: open-access

Affiliation: University of Melbourne

Abstract

BackgroundGenomic comparison of Mycoplasma synoviae vaccine strain MS-H and the MS-H parental strain 86,079/7NS established a preliminary profile of genes related to attenuation of MS-H. In this study we aimed to identify the stability of mutations found in MS-H after passage in experimental or field chickens, and to evaluate if any reverse mutation may be associated with changes in characteristics of MS-H in vitro or in vivo.ResultsWhole genome sequence analysis of 5 selected MS-H field reisolates revealed that out of 32 mutations reported previously in MS-H, 28 remained stable, while four found to be reversible to the wild-type. Each isolate possessed mutations in one to three of the genes obg, oppF1 and gap and/or a non-coding region. Examination of the 4 reversible mutations by protein modeling predicted that only two of them (in obg and oppF1 genes) could potentially restore the function of the respective protein to that of the wild-type.ConclusionsThese results suggest that the majority of the MS-H mutations are stable after passage in vaccinated chickens. Characterisation of stable mutations found in MS-H could be utilised to develop rapid diagnostic techniques for differentiation of vaccine from field strains or ts- MS-H reisolates.

Highlights

Genomic comparison of Mycoplasma synoviae vaccine strain MS-H and the MS-H parental strain 86, 079/7NS established a preliminary profile of genes related to attenuation of MS-H
A wide range of ts + viruses and bacteria have been used as vaccine candidates, but in many cases it is not Kordafshari et al BMC Genomics (2020) 21:598 exactly known whether temperature sensitivity is the cause of attenuation or just a coincidental phenotype in these organisms [4, 5]
The majority of MS clones recovered from vaccinated flocks display their ts + phenotype, but it has been suggested that MS-H proliferation in vaccinated birds generates a mixture of ts + and ts- clones in the farm [6, 7]

Summary

Introduction

Genomic comparison of Mycoplasma synoviae vaccine strain MS-H and the MS-H parental strain 86, 079/7NS established a preliminary profile of genes related to attenuation of MS-H. Unlike the non-virulent MSH strain, ts- field reisolates cause only minor lesions in the tracheal mucosa of the experimentally infected birds, significantly lower than the vaccine parent strain [7]. These results suggest that factors other than ts + phenotype are involved in the attenuation of the MS-H vaccine. OppD was found to be required for full expression of virulence of M. gallisepticum in chickens [11]

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