Analysis of factors affecting detection of infectious titers of oral poliovirus vaccine

  Objective   To assess the factors in the detection of infectious titers of oral poliovirus vaccine.

  Methods   The cytopathogenic microtitration assay in 96 well plates were used in these experiments.

  Results   Cell numbers ranging from fifty thousand to four hundred thousand showed no significant differences in infectious titers, but when cell number was under tweny five thousand the titers showed significant decrease.The infectious titers showed no significant differences at 33.5 and 35.5(P > 0.5).The infectious titers with cell passages of 290 through 300 were significantly lower than those with 150 through 160(P < 0.001).The cross inhibition of type Ⅱ and Ⅲ poliovirus polycolonal antibodies to type Ⅰ poliovirus was 0.120±0.116, the value of type Ⅰ and Ⅲ poliovirus was 0.161±0.179 for type Ⅱ, the value of type Ⅰ and Ⅱ was 0.227±0.145 for type.

  Conclusion   Cell passage is an important factor.The cross inhibitions of different types of sera depend on the ratio of viral inoculation level and serum concentration.