Vaxsafe MG (strain ts-11) is a live attenuated vaccine against the important poultry pathogen Mycoplasma gallisepticum that has been used globally to improve poultry health. However, the majority of the bacterial cells in Vaxsafe MG do not express the GapA cytadhesin, reducing their capacity to colonise the respiratory tract. Vaxsafe MG (strain ts-304) is a GapA positive clone recovered from Vaxsafe MG (strain ts-11) that has been shown to be safe and efficacious in turkeys, and preliminary studies have suggested that Vaxsafe MG (strain ts-304) may have greater efficacy in chickens than Vaxsafe MG (ts-11). The studies described here aimed to meet the international regulatory requirements for safety and efficacy in chickens. The vaccine colonised the trachea of 3-week-old chickens without inducing signs of respiratory disease or significant lesions in the respiratory tract, and was safe at a tenfold overdose and after repeated administration. It was transmissible from vaccinated to naïve chickens with no evidence of reversion to virulence following multiple in vivo passages. Finally, the superiority of Vaxsafe MG (strain ts-304) was demonstrated by its capacity to induce similar protection against infection with wild type M. gallisepticum at a 40 fold lower dose than the end of shelf life titre dose of Vaxsafe MG (ts-11). The lower effective dose of Vaxsafe MG (strain ts-304) allows it to be freeze-dried, enhancing its stability, making it easier to transport and store the vaccine and increasing its shelf life. Vaxsafe MG (strain ts-304) is, therefore, a highly efficacious and promising live attenuated vaccine candidate suitable for use in chickens.

中文翻译：

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鸡支原体支原体菌株ts-304是一种安全有效的减毒活疫苗，可用于鸡中。

Vaxsafe MG（ts-11毒株）是针对重要家禽病原体鸡毒支原体的减毒活疫苗，已在全球范围内用于改善家禽健康。但是，Vaxsafe MG中的大多数细菌细胞不表达GapA胞苷，从而降低了它们在呼吸道中定殖的能力。Vaxsafe MG（ts-304菌株）是从Vaxsafe MG（ts-11菌株）中回收的GapA阳性克隆，已证明在火鸡中是安全有效的，初步研究表明Vaxsafe MG（ts-304菌株）比Vaxsafe MG（ts-11）对鸡的疗效更好。此处描述的研究旨在满足国际法规对鸡的安全性和有效性的要求。该疫苗定居在三周大的鸡的气管中，没有引起呼吸道疾病或呼吸道明显损伤的迹象，并且在十倍过量和重复给药后是安全的。它可以从疫苗接种到幼稚的鸡中传播，没有证据表明经过多次体内传代后可以恢复为毒力。最后，Vaxsafe MG（ts-304菌株）的优越性是通过以比Vaxsafe MG（ts-304的保质期效价结束时低40倍的剂量）诱导抵抗野生型鸡毒支原体感染的类似保护作用而证明的。 11）。Vaxsafe MG（ts-304菌株）的有效剂量较低，因此可以将其冷冻干燥，从而提高其稳定性，使其更易于运输和存储疫苗，并延长其保质期。因此，Vaxsafe MG（ts-304菌株）是