The novel use of transgenic plants as vectors for the expression of viral and bacterial antigens has been increasingly tested as an alternative methodology for the production and delivery of experimental oral vaccines. Here, we examined the immunogenicity of combined plant-made vaccines that include four genes encoding immune-dominant antigens from Mycobacterium tuberculosis. Compared with the wild type and other control groups, mice treated with the combined plant-made vaccines showed significantly higher levels of interferon-γ and interleukin-2 production in response to all four proteins, and higher levels of antigen-specific CD4(+) and CD8(+) T-cell responses and immunoglobulin (Ig) G and IgA titers. These results suggest that combined plant-made vaccines can induce immunogenicity against M. tuberculosis through the induction of stronger Th1-associated immune responses. This is the first report of an orally delivered combined plant-made vaccine against tuberculosis priming an antigen-specific Th1 response, a comprehensive effect including both mucosal and systemic immune responses.
