Recombinant bacille Calmette–Guérin (BCG) expressing human interferon‐alpha 2B demonstrates enhanced immunogenicity

To increase its immunostimulatory properties, BCG was genetically engineered to secrete recombinant human interferon‐alpha 2B (rhIFN‐ α ) under control of the mycobacterial heat shock protein (hsp)60 promoter and the α antigen signal sequence. Expression of rhIFN‐ α was readily detectable by ELISA and on Western blotting. When compared with control BCG, rhIFN‐ α BCG was substantially more active in inducing the production of IFN‐ γ and IFN‐inducible protein 10 (IP‐10) from human peripheral blood mononuclear cells, while IL‐10 production was correspondingly decreased. These effects were reversible upon antibody neutralization of rhIFN‐ α . Among 10 patients tested, rhIFN‐ α BCG enhanced IFN‐ γ production in all patients ranging from 1·4‐ to 23·7‐fold with a general trend toward greatest enhancement among those with weakest baseline responses to control BCG. Correspondingly, rhIFN‐ α BCG decreased IL‐10 production in all patients by 1·2–4·8‐fold. The onset of IFN‐ γ production induced by rhIFN‐ α BCG was also more rapid, occurring within 4 h after stimulation versus > 24 h with wild‐type BCG. The observation that the maximum IFN‐ γ induction depends on the simultaneous presence of both IFN‐ α and BCG highlights the advantages of rhIFN‐ α BCG. Taken together, these immunostimulatory properties of rhIFN‐ α BCG suggest that it may be a superior agent for immunotherapeutic protocols involving live BCG in humans.