Lactoferrin modulation of BCG-infected dendritic cell functions.

Lactoferrin, an 80-kDa iron-binding protein with immune modulating properties, is a unique adjuvant component able to enhance efficacy of the existing Mycobacterium bovis Bacillus Calmette Guerin (BCG) vaccine to protect against murine model of tuberculosis. Although identified as having effects on macrophage presentation events, lactoferrin's capability to modulate dendritic cells (DCs) function when loaded with BCG antigens has not been previously recognized. In this study, the potential of lactoferrin to modulate surface expression of MHC II, CD80, CD86 and CD40 from bone marrow-derived dendritic cells (BMDCs) was examined. Generally, lactoferrin decreased pro-inflammatory cytokines [tumor necrosis factor (TNF)-alpha, IL-6 and IL-12p40] and chemokines [macrophage inflammatory protein (MIP)-1alpha and MIP-2] and increased regulatory cytokine, transforming growth factor-beta1 and a T-cell chemotatic factor, monocyte chemotactic protein-1, from uninfected or BCG-infected BMDCs. Culturing BCG-infected BMDCs with lactoferrin also enhanced their ability to respond to IFN-gamma activation through up-regulation of maturation markers: MHC I, MHC II and the ratio of CD86:CD80 surface expression. Furthermore, lactoferrin-exposed BCG-infected DCs increased stimulation of BCG-specific CD3(+)CD4(+) splenocytes, as defined by increasing IFN-gamma production. Finally, BCG-/lactoferrin-vaccinated mice possessed an increased pool of BCG antigen-specific IFN-gamma producing CD3(+)CD4(+)CD62L(-) splenocytes. These studies suggest a mechanism in which lactoferrin may exert adjuvant activity by enhancing DC function to promote generation of antigen-specific T cells.