Reproduction of vaccine and virulent Rickectsia prow azeki strains in continuous cell lines at different temperatures.

The features of intracellular development of the virulent Breinl strain and 3 vaccine E strains of Rickettsia prowazeki have been followed in continuous FL, McCoy, and B cell cultures at temperatures of 30, 35, 37, 38.5 and 40 degrees C. The virulent Breinl strain multiplied well at these temperatures in McCoy and B cells but in had been gradually lost when cultured at 40 degrees C in FL cells. In contrast to the virulent Breinl strain the vaccine E strains have lost their capacity of long term reproduction at 38.5 degrees C. At 40 degrees C the E strains did not multiply in and had been eliminated from the McCoy and B cells; thus the vaccine E strains revealed a ts-phenotype and, accordingly, it was found to represent a ts-mutant.