Background. Plague is initiated by Yersinia pestis, a highly virulent bacterial pathogen. In late stages of the infection, bacteria proliferate extensively in the internal organs despite the massive infiltration of neutrophils. The ineffective inflammatory response associated with tissue damage may contribute to the low efficacy of antiplague therapies during late stages of the infection. In the present study, we address the possibility of improving therapeutic efficacy by combining corticosteroid administration with antibody therapy in the mouse model of bubonic plague.
Methods. Mice were subcutaneously infected with a fully virulent Y. pestis strain and treated at progressive stages of the disease with anti–Y. pestis antibodies alone or in combination with the corticosteroid methylprednisolone.
Results. The addition of methylprednisolone to antibody therapy correlated with improved mouse survival, a significant decrease in the amount of neutrophils and matrix metalloproteinase 9 in the tissues, and the mitigation of tissue damage. Interestingly, the combined treatment led to a decrease in the bacterial loads in infected organs.
Conclusions. Corticosteroids induce an unexpectedly effective antibacterial response apart from their antiinflammatory properties, thereby improving treatment efficacy.