Calcineurin subunit B is an immunostimulatory protein and acts as a vaccine adjuvant inducing protective cellular and humoral responses against pneumococcal infection.

Protective immunity involves a dynamic balance between humoral and cellular immune responses. In the present work we demonstrated that recombinant human calcineurin subunit B (rhCnB) stimulated the expression of the surface molecules CD83, CD80, CD86, CD40, and HLA-DR. It also promoted secretion of inflammatory cytokines IL-6, TNF-α, and IL-1β by human PBMC-derived dendritic cells. In in vivo experiments, splenocytes from BALB/c mice immunized with pneumolysin plus rhCnB contained a higher percentage of CD3(+)CD4(+) T lymphocytes, produced more antigen-specific splenocyte proliferation activity, and had higher anti-pneumolysin immunoglobulin G (IgG) titers. Transcript levels of cytokines such as IL-4, IL-10, and IFN-γ in the splenocytes were also upregulated when in vitro stimulated with pneumolysin. Thus, rhCnB promoted a mixed Th1/Th2 type immune response when given together with the specific antigen PN. RhCnB could have potential as a prophylactic vaccine adjuvant.
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