Gram-negative bacterial mutants resistant stress conditions, including CO2, acid pH, and high osmolarity are provided, having reduced TNF-α induction having a msbB mutation, that are rendered stress-resistant by a mutation in the zwf gene. A method for prophylaxis or treatment of a virally induced disease in a subject comprising administering to said subject attenuated stress-resistant gram-negative bacterial mutants, is also provided, along with Methods for prophylaxis or treatment of a virally induced disease in a subject comprise administering to said subject one or more stress-resistant gram-negative bacterial mutants as vectors for the delivery of one or more therapeutic molecules. The methods provide efficient delivery of therapeutic molecules by stress-resistant gram-negative bacterial mutants engineered to express said therapeutic molecules.
