Plaque Studies with Certain Group B Arboviruses. I. Japanese B Encephalitis Virus Strains on Hamster Kidney and Chick Embryo Tissue Culture.

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Abstract
Summary Nakayama and OCT-wild strains of JBE produced similar plaques on HKTC, double agar overlay, which are 0.3-0.7 cm in diameter, clear with sharp boundaries while plaques produced by OCT-attenu-ated are much smaller and hazy. Virus adsorption at 37°C is optimum at 2 hours for OCT-wild and only 1 hour for OCT-attenuated in HKTC; in CETC 90 minutes is the optimal adsorption time for Nakayama strain and 1 to 2 hours produces about the same plaques for OCT-attenuated strain. Washing after the adsorption period is apparently unessential and repeated washing is deleterious to the tissue. For optimal plaque visualization in HKTC with the 3 JBE strains, 0.004% neutral red is most satisfactory in the second agar overlay. Larger plaques occur with all strains at 37°C than at lower temperatures. Plaques produced by Nakayama and OCT-attenuated on CETC were much smaller and less clear than those on HKTC. Plaque formation of JBE Nakayama, OCT-wild and OCT-attenuated strains in HKTC (double agar overlay) and CETC (single agar overlay) is inhibited more by Noble-agar than by Bacto-agar. Autoclaved neutral red was less satisfactory than filtered dye for obtaining optimal plaques. NaHCO3 in the concentration of about 0.1 g % gave the best plaques on both HKTC and CETC.