A rapid plaque method using vertical tube cultures for titration of viruses and neutralizing antibodies.

Standard methods for titrating and typing enteroviruses and other viruses, or for assaying antibodies against them, are based on observation of metabolic inhibition of infected cells or on direct microscopic reading of cytopathogenic effects. Incubation of cell cultures for at least a week, with two or three readings during this period, is usually required before assessment is completed. This report describes a vertical-tube method in which cell monolayers are confined to the bottom end of a serological tube; an agar overlay is used after virus or virus-serum inoculation. The reduced monolayer area allows seeding with only about 30% of the cells required for standard tube cultures, and 5% of those required for plaque assay in bottle cultures. The new method requires only a single macroscopic reading one to three days after the test is set up. This method has proved economical, simple and rapid in epidemiological studies on rapidly growing viruses of the entero-, reo-, herpes-, myxo- and poxvirus groups, and for tests of the genetic markers of live poliovirus vaccine.