Studies on Measles Virus in Various Tissue Cultures
I. Agar Cell-Suspension Plaque Assay of Measles Virus in Stable Cell Lines
1965 Volume 38 Issue 10 Pages 357-366
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1965 Volume 38 Issue 10 Pages 357-366
Recently several reports have appeared on the plaque assay procedures of measles virus, but all these methods have succeeded only by use of primary monkey kidney cell cultures and overlay media such as plasma clot or bovine amniotic fluid.
In order to simplify the technique or to suit for routine work, experiments were cat ried out with stable cell lines for plaque assay culture and obtained the following results:
1) When the “Sugiyama” strain of measles virus, adapted to FL cells, was plated in HEp-2, FL, HeLa and KB cell monolayers and oberlaid with Yeast extract-Lactalbumin hydrolysate-Earle's balanced salt solution (YLE) agar media and keeping all oberlaid plates at 36°C, we could easily obtain small clear plaques. Thus, a plaque assay method for measles virus has been developed useing YLE-agar oberlay medium.
2) The optimal condition was found in the YLE-agar oberlay medium (pH 7.6) of 0.5% NaHCO3, 10% serum and of 1.1-2.2% agar (about 3m1 per 50-m1 bottle).
3) Of our four human cell cultures, we found HEp-2 and KB cell cultures to possess the highest plating efficiency of measles virus under the same conditions, which were followed by FL and HeLa cell cultures in order.
4) In monolayers infected with appropriate dilutions of measles virus, there appeared small but distinct plaques on the 5th day. The average diameter of plaque was about 2-3 mm. Plaque number increased gradually up to the 10th day, but not increased thereafter, leaving the countable same number possibly up to the 20th day.
5) When the same input dose of measles virus was used, the constant plaque number appeared increasingly up to the 4th day in the cell sheet which was taken in the logarithmic growth phase, but in the contrary its plaque number rapidly decreased in the decline phase.
6) The plaque assay of strains of measles virus, “Edmonston”, FV49 (FL passage 49 of “Toyoshima” strain) and KB1.4 (KB passage 14 of FL-adapted “Toyosma” strain), which were all adapted to stable cell lines, showed almost the same results as that of “Sugiyama” strain.
