Virulence factors of Yersinia pestis are overcome by a strong lipopolysaccharide response.

At mammalian body temperature, the plague bacillus Yersinia pestis synthesizes lipopolysaccharide (LPS)-lipid A with poor Toll-like receptor 4 (TLR4)-stimulating activity. To address the effect of weak TLR4 stimulation on virulence, we modified Y. pestis to produce a potent TLR4-stimulating LPS.