Intranasal nanoparticle vaccine elicits protective immunity against Mycobacterium tuberculosis

Abstract Mucosal vaccines have the potential to elicit protective immune responses at the point of entry of respiratory pathogens thus preventing even the initial seed infection. Unlike licensed injectable vaccines, mucosal vaccines comprising protein subunits are only in the development stage. One of the primary challenges associated with mucosal vaccines has been the identification and characterization of safe yet effective mucosal adjuvants that can effectively prime multi-factorial mucosal immunity. In this study, we tested NanoSTING, a liposomal formulation of the endogenous activator of the stimulator of interferon genes (STING) pathway, cyclic guanosine adenosine monophosphate (cGAMP), as a mucosal adjuvant. Intranasal administration of this vaccine provides protection comparable to subcutaneous administration of the live attenuated Mycobacterium bovis vaccine strain Bacille–Calmette–Guérin (BCG) upon challenge with aerosolized Mycobacterium tuberculosis Erdman strain. Protection against the bacterium is likely due to CXCR3+ lung resident T cells that are known to be important for the control of bacterial infection. Intranasal delivery also induces IFNγ secreting CD4+ T cells in lung which is necessary for intracellular bactericidal activity. Our results indicate that NanoSTING adjuvanted protein vaccines can elicit a multi-factorial immune response that provides durable protection from infection by M. tuberculosis.