Enhancement of rhinovirus plaque formation in human heteroploid cell cultures by magnesium and calcium.

Fiala, Milan (University of Washington, Seattle), and George E. Kenny. Enhancement of rhinovirus plaque formation in human heteroploid cell cultures by magnesium and calcium. J. Bacteriol. 92:1710-1715. 1966.-A reproducible macroplaque assay for six M and three H strains of rhinoviruses has been developed in several human heteroploid cell lines. Plaques were produced only with suitable solidifying agents: purified agar (Ionagar, Agarose) or methylcellulose. Plaque development was greatly enhanced by increasing Mg(+2) to 30 to 40 mm. Diethylaminoethyl (DEAE) dextran also increased plaque sizes, and the effects of Mg(+2) and DEAE dextran were additive. In addition, Ca(+2) substituted for Mg(+2). The suitability of human heteroploid cell lines for rhinovirus plaque assay varied greatly, ranging from insensitivity through partial to complete sensitivity. This assay was six to seven times more sensitive than an end point tube assay. These results indicate that potentiation of plaque formation by Mg(+2) known for some enteroviruses can also be extended to the rhinovirus group of picornaviruses.