Provided herein are isolated polypeptides comprising the amino-terminal domain of Mycobacterium tuberculosis porin A (MtpA), wherein the polypeptide is a porin monomer. Also provided are isolated polypeptides comprising the carboxy-terminal domain of Mycobacterium tuberculosis porin A, wherein the polypeptide is a toxin. Also provided are methods of treating or preventing a Mycobacterium tuberculosis (Mtb) infection in a subject with or at risk of developing a Mtb infection. Further provided are chimeric porin polypeptides comprising a first polypeptide comprising an amino-terminal domain of Mycobacterium tuberculosis porin and a second polypeptide comprising an antigen and the use the chimeric porin polypeptides in methods of eliciting an immune response in a subject.