The use of frozen cells in the microtitre serum neutralization test for infectious bovine rhinotracheitis.

Some parameters of the microtitre serum neutralization test were examined when using bovine fetal kidney cells derived from stocks stored in liquid nitrogen. In replicate tests with one serum there was no significant difference (p greater than 0.05) between titres calculated on the basis of cytopathic effect when either two or four wells were used per serum dilution. Also, there was no significant difference between titres calculated on the basis of a cell staining method when either two or four wells were used per serum dilution. When titres obtained by the 2-well-cytopathic effect method were compared with those obtained by the 2-well-stain method differences were not significantly different and it was concluded that the latter method using frozen cells constituted a practical and reproducible test. No significant titre variation occurred in cells serially passaged after having been frozen, or in cells derived from five different fetuses. Titres of sera from 41 cattle conformed to a log normal distribution pattern.