Comparison between immunopotency tests and specific active or passive acquired resistance against Mycobacterium tuberculosis in mice induced with three different preparations of BCG pasteur vaccine.

Tests, exploring hallmarks of cell-mediated immunity (CMI), were used in order to compare immunogenecity of same numbers of viable units from three different preparations of BCG vaccine derived from the same strain. Specific and non-specific cellular immune responses were assessed by several tests including, active and adoptive acquired resistance to Mycobacterium tuberculosis, local and systemic granuloma formation. BCG persistence in the spleen, delayed type hypersensibility (DTH) to tuberculin, immunopotentiation of DTH to sheep red blood cells, increase resistance to Listeria monocytogenes infection and occurrence of non-specific in vitro immunodepression. The ranking order of the three preparations concerning the active specific acquired resistance to tuberculosis did correlate well the ranking established for all immunopotency tests used in our study, however differences in acquired resistance were small as compared to differences observed for immunopotency tests. Moreover, adoptive transfer of same number of lymphoid cells from immune donors gave a different ranking order; the well dispersed fresh frozen (FF) vaccine being more able to induce higher adoptive protection as compared to the mechanically dispersed preparations. All these results clearly demonstrated that BCG could not be considered as single entity and that the test based on acquired resistance to M. tuberculosis or in vivo or in vitro hallmarks of CMI cannot be used as standard procedures.