Therapeutic methods and microorganisms therefor are provided. The microorganisms are designed to accumulate in immunoprivileged tissues and cells, such as in tumors and other proliferating tissue and in inflamed tissues, compared to other tissues, cells and organs, so that they exhibit relatively low toxicity to host organisms. The microorganisms also are designed or modified to result in leaky cell membranes of cells in which they accumulate, resulting in production of antibodies reactive against proteins and other cellular products and also permitting exploitation of proliferating tissues, particularly tumors, to produce selected proteins and other products. Vaccines containing the microorganisms are provided. Combinations of the microorganisms and anti-cancer agents and uses thereof for treating cancer also are provided.