Abstract: Recombinant polynucleotides are provided that confer at least partial immunity on an individual to an infectious intracellular pathogenic agent. The recombinant polynucleotides encode a costimulatory factor and/or a target antigen polypeptide. The immune response that confers the immunity results from the expression of both polypeptides in an antigen presenting cell in the individual. The immunity is to the pathogenic agent that naturally encodes the target antigen polypeptide.