The future of plague vaccines: hopes raised by a surrogate, live-attenuated recombinant vaccine candidate.

Yersinia pestis (YP) is the Gram-negative etiological agent of plague against which no commercial vaccine exists to prophylactically prevent a potential outbreak due to natural or bio-warfare/terrorism-mediated causes. The US FDA only recently approved levofloxacin to combat this deadly pathogen. In the article under review, an attenuated, recombinant Salmonella typhimurium ΔphoPQ mutant strain producing YP antigens F1, LcrV and F1-V (fusion protein) from either low-copy pBR or high-copy pUC vectors (maintained by plasmid addiction rather than antibiotic selection pressure) were evaluated for their ability to induce a humoral immune response in both mice and rabbits. This study highlights the need for developing a well-tolerated YP vaccine that, through the oral route, can be readily administered and elicit both mucosal and systemic anti-plague humoral immunity.