STUDIES ON SEVERAL FACTORS AFFECTING THE HEMAGGLUTININ TITER OF MEASLES VIRUS

A study on several factors affecting the hemagglutinin titer of measles virus was made. Without concentrating the infectious tissue culture fluid, the hemagglutinating titre of 1:32--1:64 has been obtained. The following factors were found to be important in obtaining high titre hemagglutinin: 1). Type of cell culture used--continuous cell line was better than its corresponding primary cell culture and human renal cell culture better than human ammion cell culture; 2). With the same type of cells, cultures showing over- rapid development of C P E gave low titre of hemagglutinin, although the infectivity titre was found to be approximately the same as those giving high titre of hemagglutinin with late development of C P E culture. Change of maintenance medium after 5--6 days of infection in primary cell culture or aftec 2--3 days in continuous cell lines not only maintained the cell in good condition but also stimulated the rapid development of CPE. Thus leading to the production of high titre hemagglutinin; 3). Cell cultures in- cubated at 33℃ gave a better production of hemagglutinin than those incubated at 37℃; 4). Treatment of infected cell culture with ultrasonic wave increased the yield of hemag- glutinin to 4 folds. By decreasing the concentraction of red blood cell from 1% to 0.5%, the hemagglutinin titre could be raised to 2 folds.