Comparison of the in vivo multiplication of 10 BCG substrains in three strains of mice: no correlation with their antitumour activity.

The dynamics of in vivo multiplication of 10 BCG substrains were studied in three different strains of mice: CF-1, B6D2F1/J and C57BL/6. For each substrain, the number of CFU recovered from the spleen of mice previously injected intravenously with BCG was determined weekly for 5 consecutive weeks. On the basis of the statistical analysis of the results, the BCG substrains were classified for each strain of mice in three groups of virulence: high, intermediate and low. The Russian and Japanese substrains were found to be the most virulent, and the Glaxo and Tice 946 BL (I2) the least virulent substrains. No correlation could be established between in vivo multiplication and antitumour activity of each BCG substrain as estimated in preventive treatment against three tumour systems: Ehrlich carcinoma in CF-1 mice, L1210 leukaemia in B6D2F1/J mice, and B16 melanoma in C57BL/6 mice.