Schloer G M, Hanson R P
J Virol. 1968 Jan;2(1):40-7. doi: 10.1128/JVI.2.1.40-47.1968.
Ability of 14 Newcastle disease virus strains to produce large plaques was related to virulence for chickens. Plaque-size comparisons were made under standard conditions in chick embryo cell monolayers. All plaque-producing strains showed a range of plaque sizes modified to a degree by the overlay medium used. An increase in size was found for most strains under methyl-cellulose overlay medium. Markedly larger plaques were found under this medium for both Calif-RO and Calif-CG strains. Heterogeneity in plaque size was most pronounced in velogenic (high virulence) strains. Only populations of small plaques were found in mesogenic (intermediate virulence) strains, and plaques were rarely found in lentogenic (low virulence) strains. Statistical analysis showed that the plaque size of velogenic strains differed significantly from mesogenic strains. None of the 11 plaque-producing strains had a normal distribution of plaque sizes, owing primarily to the presence of different genotypes within the plaquing population of a strain. This was demonstrated by derivation of clones from two of the strains. The populations of the large (Herts L) and small (Herts S) clear plaque clones derived from Eng-Herts were homogenous and distinct from one another on the basis of plaque size. Herts L was more virulent than Herts S. Although Herts L became more heterogenous in respect to plaque size upon repeated passage in embryonated eggs, no decrease in virulence of the strain was observed.
14株新城疫病毒产生大噬斑的能力与对鸡的毒力相关。在鸡胚细胞单层中于标准条件下进行噬斑大小比较。所有产生噬斑的毒株均表现出一定范围的噬斑大小，且在一定程度上会受到所用覆盖培养基的影响。在甲基纤维素覆盖培养基下，大多数毒株的噬斑大小有所增加。在此培养基下，Calif - RO和Calif - CG毒株均出现明显更大的噬斑。噬斑大小的异质性在速发型（高毒力）毒株中最为明显。在中发型（中等毒力）毒株中仅发现小噬斑群体，而在缓发型（低毒力）毒株中很少发现噬斑。统计分析表明，速发型毒株的噬斑大小与中发型毒株有显著差异。11株产生噬斑的毒株中，没有一株的噬斑大小呈正态分布，这主要是由于毒株噬斑形成群体中存在不同基因型。这通过从其中两株毒株衍生克隆得以证明。源自Eng - Herts的大（Herts L）、小（Herts S）透明噬斑克隆群体在噬斑大小方面是同质且彼此不同的。Herts L比Herts S毒力更强。尽管Herts L在鸡胚中反复传代后噬斑大小变得更加异质，但未观察到该毒株毒力下降。
