另外一种方法是由毒性减弱的病原微生物制成，当作为疫苗注射时，这种微生物会引起温和的或不表现症状，但是可以保护接受者免受更猛烈的野生菌株的侵害。

In another they were made from weakened strains of pathogenic organisms that caused mild or no symptoms when injected as a vaccine yet protected recipients from more severe wild strains.

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如构建出突变体库，从中筛选出毒力减弱的副猪嗜血杆菌突变菌株，对研制出基因工程弱毒活疫苗具有重要意义。

So it's has great significance to construct the mutant storehouse and slecte the toxicity weak Hps mutant strain for developing the genetic engineering attenuated vaccine.

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为了解乙型脑炎（乙脑）减毒活疫苗弱毒株SA14 14 2神经毒力的减弱程度，本文对弱毒株及其原株SA14强毒株进行了猴体和小白鼠的致病性和病理学变化的比较试验。

In order to study the attenuation of neurovirulence of SA14 14 2 attenuated vaccine virus, monkeys and mice were tested with the strain and its parent SA14 virulent strain.

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