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. 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. Whole 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. These 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.

中文翻译：

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对滑膜支原体疫苗菌株MS-H的选定野外分离株的基因组进行的初步比较分析显示，在体内传代后，稳定和不稳定突变均可见。

滑膜支原体疫苗株MS-H和MS-H亲本株86,079 / 7NS的基因组比较建立了与MS-H减毒有关的基因的初步概况。在这项研究中，我们旨在鉴定在实验或田间鸡传代后在MS-H中发现的突变的稳定性，并评估在体外或体内，是否有任何反向突变可能与MS-H特征的变化有关。对5个选定的MS-H场重新分离株的全基因组序列分析表明，先前在MS-H中报道的32个突变中，有28个保持稳定，而发现4个可逆至野生型。每个分离株在obg，oppF1和gap和/或非编码区的一到三个基因中具有突变。通过蛋白质建模对这4个可逆突变的检查表明，只有其中两个（在obg和oppF1基因中）​​可以将相应蛋白质的功能恢复为野生型。这些结果表明，大多数MS-H突变在接种鸡中通过后是稳定的。MS-H中发现的稳定突变的特征可用于开发快速诊断技术，以区分疫苗与田间毒株或ts-MS-H再分离株。