Author(s)

Monique C. da Silva¹, Elena B. Lasunskaia¹, Wilmar Dias da Silva^2*

¹Laboratory of Biology of Recognition, Universidade Estadual do Norte Fluminense, Campos, Rio de Janeiro, Brazil.
²Laboratory of Immunochemistry, Institute Butantan, São Paulo, Brazil.

The cellular immune response elicited by Mycobacterium bovis Bacille Calmette-Guérin (BCG) has been carefully investigated, but the humoral immune response has been partially neglected. BALB/c mice were immunized with BCG strain used to immunize humans. Anti-BCG antibodies, as assayed by ELISA, began to appear in the sera after the third week of immunization and plateaued three weeks after the 8^th immunization. The total immunoglobulins (Igs) were purified by caprylic acid method from pooled serum collected after the 8^th immunization. Anti-BCG antigen antibodies were detected in the total Igs preparation as well as in IgG, IgM, IgA, IgG₁, IgG_2a, and IgG_2b, but not in the IgG₃. Distinct BCG proteins were recognized the IgGs in Western blot analysis. Opsonization of BCG bacilli by the purified Igs potentiated internalization of the bacteria by murine Raw 264.7 macrophages. The intracellular BCG elimination coincided with the induction of NO production, which was more pronounced in cells infected with opsonized BCG compared to those infected with the non-opsonized bacteria. Coincidently, the production of NO was also higher in macrophages infected with opsonized BCG (maximal NO production at 48 h of incubation). The obtained results demonstrate that repeated inoculations of BCG effectively activate the humoral immune response, justifying the use of BCG as a live recombinant vaccine vector to insert genes encoding virulence factors controlled by antibodies.

Mycobacterium bovis; Bacille Calmette-Guérin; BCG; Antibodies; Opsonization; Bacterial Killing

Silva, M. , Lasunskaia, E. and Silva, W. (2013) Repeated inoculations of Mycobacterium bovis Bacille Calmette-Guérin (BCG) are needed to induce a strong humoral immune response against antigens expressed by the bacteria. Open Journal of Immunology, 3, 71-81. doi: 10.4236/oji.2013.33011.