Antibodies and cytokines independently protect against pneumonic plague

Yersinia pestis causes pneumonic plague, an exceptionally virulent disease for which we lack a safe and effective vaccine. Antibodies specific for the Y. pestis F1 and LcrV proteins can protect mice against pulmonary Y. pestis infection. We demonstrate that neutralizing tumor necrosis factor-alpha (TNFα) and gamma-interferon (IFNγ) abrogates this protection at sub-optimal levels of F1- or LcrV-specific antibody, but not at optimal levels. Moreover, we demonstrate that endogenous TNFα and IFNγ confer measurable protection in the complete absence of protective antibodies. These findings indicate that antibodies and cytokines independently protect against pneumonic plague and suggest that surrogate assays for plague vaccine efficacy should consider both the level of vaccine-induced antibody and the capacity of vaccine recipients to produce TNFα and IFNγ upon exposure to Y. pestis.