Commonly administered bacille Calmette-Guerin strains induce comparable immune response

Area of Science:

• Immunology
• Vaccinology
• Microbiology

Background:

• Bacille Calmette-Guerin (BCG) is the sole vaccine available for tuberculosis (TB).
• BCG's protective efficacy against TB in adults exhibits significant variability.
• The specific BCG strain used may influence vaccine outcomes.

Purpose of the Study:

• To compare the immunogenicity of two widely used BCG strains: BCG China and BCG Pasteur.
• To evaluate differences in antibody production, splenocyte proliferation, T cell subsets, and cytokine secretion.
• To investigate how BCG strain variation impacts the host immune response.

Main Methods:

• Healthy BALB/c mice were immunized with either BCG China or BCG Pasteur strain.
• Humoral and cellular immune responses were assessed at multiple time points post-immunization (6, 8, 10, 12 weeks).
• Measurements included specific IgG, IgG1, IgG2a antibody titers, splenocyte proliferation, CD4(+) and CD8(+) T cell percentages, and IFN-γ and IL-4 concentrations.

Main Results:

• BCG Pasteur strain elicited significantly higher specific IgG and IgG1 antibody titers compared to BCG China strain.
• BCG Pasteur induced greater splenocyte proliferation and higher percentages of CD4(+) and CD8(+) T cells.
• A higher concentration of secreted IFN-γ was observed following immunization with BCG Pasteur.
• No significant differences were found in IgG2a antibody titers or IL-4 concentrations between the two BCG strains.

Conclusions:

• The immunogenicity of BCG vaccines is strain-dependent.
• Differences in immune responses, particularly T cell activation and IFN-γ production, vary between BCG strains.
• Strain-specific immune responses may contribute to the observed variability in BCG vaccine efficacy against tuberculosis.