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Avian Infectious Bronchitis Coronavirus Variation and Selection.

机译：禽传染性支气管炎冠状病毒变异和选择。

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摘要

Infectious bronchitis virus (IBV) is a highly variable virus, its genetic variation is generated by nucleotide insertions, deletions, or point mutations made by the viral polymerase during virus replication. Another mechanism for IBV variability is RNA recombination. Selection of IBV in the host has also been previously demonstrated. Specific objectives during this three-part investigation were to assess IBV intraspatial variation in chickens, determine the IBV evolutionary pathway in viral immunodeficient hosts, and evaluate IBV variation and effects on testes of young and adult roosters.;Variation inside the chicken (Intraspatial variation) was assessed, we inoculated chickens with an Ark-type IBV commercial vaccine and characterized the sequences of the spike (S) 1 gene of IBV contained in tear fluid, trachea, and reproductive tract. The predominant IBV phenotype contained in the vaccine (prior to inoculation), became a minor or non-detectable population at all times in all tissues after replication in the chickens. Five new predominant populations designated as component (C) 1 through C5, showing distinct non-synonymous changes, were detected in the tissues or fluids of individual vaccinated chickens. Significant differences were detected in the incidence of some distinct predominant IBV populations in tissues and fluids. These results indicate for the first time that IBV undergoes intraspatial variation during the host invasion.;We evaluated the same portion of the S1 gene sequence of the dominant phenotype of an IBV Ark vaccine strain during continued passages in chickens infected with the immunosuppressive viruses (CAV and/or IBDV) as well as in immunocompetent chickens. The dominant genotype of the vaccine strain was rapidly negatively selected in all chicken groups. Based on S1 geno/phenotype, exactly the same IBV subpopulations detected in the previous experiment emerged. During the first passage several subpopulations emerged in each group followed by establishment of one predominant population after further passages. Only subpopulation C2 successfully became established in either CAV or IBDV infected chickens. These results indicate that selection does not cease in immunodeficient chickens. Subpopulations C1 or C4 became established in immunocompetent birds but became extinct after only a few succeeding passages. A similar result was observed in chickens co-infected with CAV+IBDV. This finding constitutes further evidence for phenotypic drift occurring mainly as a result of selection.;Finally, we assessed IBV virulent strain variation and its effect on the chicken testes. Pre-puber males were inoculated with two IBV virulent strains (M41 and Ark). IBV RNA was detected in most of the testicles of both inoculated male groups. Marginal non-synonymous variation was detected in the S gene of the predominant population of IBV replicating in the testes. IBV M41 and Ark were detected in spermatogonia and Sertoli cells of testicles of infected roosters by immunofluorescence, without histopathological changes. Venereal transmission of IBV was demonstrated by artificially inseminating hens. IBV RNA was detected in the trachea of all hens inseminated with IBV-spiked semen and in 50% of hens inseminated with semen from IBV-infected males providing experimental evidence for IBV venereal transmission.;These results show high genetic variability of IBV populations resulting from mutation and selection, following the same evolutionary mechanisms originally described by Darwin for more complex species.
机译：传染性支气管炎病毒（IBV）是高度可变的病毒，其遗传变异是由病毒复制过程中病毒聚合酶产生的核苷酸插入，缺失或点突变产生的。 IBV变异性的另一种机制是RNA重组。先前已经证明了宿主中IBV的选择。此三部分调查的具体目标是评估鸡的IBV空间内变异，确定病毒免疫缺陷宿主中的IBV进化途径，评估IBV变异及其对幼年和成年雄鸡睾丸的影响;鸡内部变异（空间内变异）经过评估，我们用Ark型IBV商业疫苗接种了鸡，并表征了泪液，气管和生殖道中所含的IBV尖峰（S）1基因的序列。疫苗中所含的主要IBV表型（接种前）在鸡中复制后，在所有组织中始终都是次要或不可检测的种群。在个别接种鸡只的组织或体液中检测到五个新的主要种群，分别表示为组分（C）1至C5，显示出明显的非同义词变化。在组织和体液中一些不同的主要IBV人群的发病率中发现了显着差异。这些结果首次表明IBV在宿主侵袭过程中发生了空间内变异。;我们在感染了免疫抑制病毒（CAV）的鸡连续传代过程中评估了IBV Ark疫苗株显性表型的S1基因序列的相同部分和/或IBDV）以及具有免疫功能的鸡。在所有鸡群中，疫苗株的显性基因型迅速被否定选择。基于S1基因/表型，出现了与先前实验中检测到的完全相同的IBV亚群。在第一次传代期间，每组中出现了几个亚群，随后在进一步传代后建立了一个主要种群。在感染CAV或IBDV的鸡中仅成功建立了亚群C2。这些结果表明免疫缺陷鸡的选择不会停止。亚群C1或C4在具有免疫能力的禽类中建立，但仅在随后几代传代后就灭绝了。在用CAV + IBDV共同感染的鸡中观察到了相似的结果。这一发现构成了表型漂移的进一步证据，表型漂移主要是由于选择的结果。最后，我们评估了IBV毒株的变异及其对鸡睾丸的影响。青春期前的男性接种了两种IBV强毒株（M41和Ark）。在两个男性接种者的大多数睾丸中都检测到了IBV RNA。在睾丸中IBV复制的主要人群的S基因中检测到边缘的非同义变异。通过免疫荧光法在感染的公鸡睾丸的精原细胞和睾丸支持细胞中检测到IBV M41和Ark，无组织病理学改变。 IBV的性病传播是通过人工授精的母鸡来证明的。在所有IBV掺加精液的母鸡的气管中检测到IBV RNA，在50％的IBV感染雄性精子的母鸡中检测到IBV RNA，提供了IBV性病传播的实验证据;这些结果表明IBV人群的遗传变异性很高按照达尔文最初针对更复杂物种描述的相同进化机制进行突变和选择。

著录项

  • 作者

    Gallardo, Rodrigo A.;

  • 作者单位

    Auburn University.;

  • 授予单位 Auburn University.;
  • 学科 Agriculture Animal Pathology.;Biology Veterinary Science.;Biology Virology.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 117 p.
  • 总页数 117
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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