Gram-negative bacteria, and compositions containing the bacteria, resistant to one or more stress conditions, including, but not limited to, CO2, acid pH, and high osmolarity, having reduced TNF-αinduction having a mutation in one or more lipid biosynthesis genes, e.g., msbB, rendered stress-resistant by a mutation in the zwf gene are provided. Methods for prophylaxis or treatment of a virally induced disease in a subject comprising administering preferably attenuated stress-resistant gram-negative bacterial mutants. and for prophylaxis or treatment of a virally induced disease in a subject comprising administering one or more stress-resistant gram-negative bacterial mutants as vectors for the delivery of one or more therapeutic molecules are provided.