Does intravenous vaccination with self-killing BCG lead to development of an immune response that protects against Mycobacterium tuberculosis?

Abstract The use of intradermal BCG offers limited protection against tuberculosis. Intravenous (IV) administration of BCG has shown to produce robust protection against infection in a non-human primate model of tuberculosis. However, the duration of exposure and time required to elicit an efficacious, protective response is unknown and safety of IV administration of live BCG remains a concern. Here we investigated whether a self-limiting strain of BCG (killswitchBCG; ksBCG) could induce protective responses in macaques. ksBCG uses two transcriptionally repressible lysins; the inducer doxycycline is required for repression, with the absence of inducer leading to BCG death. Our first study demonstrated the robust in vivo killing of ksBCG once doxycycline is stopped IV ksBCG elicited a robust, multicellular immune response in airways and lung up to 8 weeks, similar to standard BCG. In the current study we are assessing protection conferred against Mycobacterium tuberculosis with IV ksBCG. Mauritian cynomolgus macaques (MCM) were vaccinated intravenously with ksBCG. 5 months post vaccination, animals were challenged with M. tuberculosis and later euthanized 12 weeks post infection. Bronchoalveolar lavages were routinely taken throughout the study, and alongside tissue samples, analyzed using spectral flow cytometry. The presence of multiple cell types (CD4, CD8, and gd T cells, B cells, NK cells), cytokines (IFNg, IL-2, IL-17, TNF) and cytotoxic molecules (granzymes B and K, perforin, granulysin), as well as M. tuberculosis bacterial burden will be assessed to determine the level of protection provided by IV ksBCG. NIH R01 AI143788