Reproducible plaquing system for rhinovirus serotypes in HeLa cells--agarose suspension

HeLa cell--agarose suspension method provides an excellent plaquing system for assay of rhinovirus serotypes which ordinarily produce indistinct plaques on cell monolayers. The variable plaque size of cloned virus progeny does not involve antigenic change in phenotype as shown by plaque neutralization test. The system has proved useful for accurate and reproducible plaque assay of rhinoviruses, assay of serum neutralizing antibodies and cloning of viruses. The plaques produced are large, clear and reproducible. The factors which influence the plaquing of rhinoviruses in this system are the age of the cells, cell density and pH of the medium.