A single strain of Mycobacterium bovis bacillus Calmette-Guerin (BCG) grown in two different media evokes distinct humoral immune responses in mice

Two attenuated bacillus Calmette-Guerin (BCG) preparations derived from the same Moreau strain, Copenhagen but grown in Sauton medium containing starc h and bacto-peptone (onco BCG, O-BCG), or asparagine (intradermal BCG, ID-B CG), exhibited indistinguishable DNA sequences and bacterial morphology. Th e number of viable bacilli recovered from spleen, liver and lungs was appro ximately the same in mice inoculated with the vaccines and was similarly re duced (over 90%) in mice previously immunized with either BCG vaccine. The humoral immune response evoked by the vaccines was, however, distinct. Sple en cell proliferation accompanying the growth of bacilli in tissue was sign ificantly higher in mice inoculated with O-BCG. These cells proliferated in vitro upon challenge with the corresponding BCG extract. Previous cell tre atment with mAb anti-CD4 T cells abolished this effect. Anti-BCG antibodies , as assayed either in serum by ELISA or by determining the number of antib ody-producing spleen cells by the spot-ELISA method, were significantly hig her in mice inoculated with ID-BCG. Anti-BCG antibodies were detected in al l immunoglobulin classes, but they were more prevalent in IgG with the foll owing distribution among its isotypes: IgG1>(IgG2a = IgG2b)> IgG3, When som e well-characterized Mycobacterium tuberculosis antigens were used as subst itutes fur BCG extracts in ELISA, although antibodies against the 65-kDa an d 96-kDa proteins were detected significantly, antibodies against the 71-kD a, 38-kDa proteins and lipoarabinomannan were only barely detected or even absent. These results indicate that BCC bacilli cultured in Sauton-asparagi ne medium permitted the multiplication of bacilli, tending to induce a stro nger humoral immune response as compared with bacilli grown in Sauton-starc h/bacto-peptone-enriched medium.