Systemic cytokine response in murine anthrax

Summary Systemic pro‐inflammatory cytokine release has been previously implicated as a major death‐causing factor in anthrax, however, direct data have been absent. We determined the levels of IL‐1β, IL‐6 and TNF‐α in serum of mice challenged with virulent (Ames) or attenuated (Sterne) strains of Bacillus anthracis. More than 10‐fold increase in the IL‐1β levels was detected in Ames‐challenged Balb/c mice, in contrast to more susceptible C57BL/6 mice, which showed no IL‐1β response. Balb/c mice have also responded with higher levels of IL‐6. The A/J mice demonstrated IL‐1β and IL‐6 systemic response to either Ames or Sterne strain of B. anthracis, whereas no increase in TNF‐α was detected in any murine strain. We used RT‐PCR for gene expression analyses in the liver which often is a major source of cytokines and one of the main targets in infectious diseases. A/J mice challenged with B. anthracis (Sterne) showed increased gene expression for Fas, FasL, Bax, IL‐1β, TNF‐α, TGF‐β, MIP‐1α, KC and RANTES. These data favour the hypothesis that apoptotic cell death during anthrax infection causes chemokine‐induced transmigration of inflammatory cells to vitally important organs such as liver. Administration of caspase inhibitors z‐VAD‐fmk and ac‐YVAD‐cmk improved survival in Sterne‐challenged mice indicating a pathogenic role of apoptosis in anthrax.