Utilization of host polyamines in alternatively activated macrophages promotes chronic infection byBrucella abortus.

Abstract

Treatment of intracellular bacterial pathogens with antibiotic therapy often requires a long course of multiple antibiotics. A barrier to developing strategies that enhance antibiotic efficacy against these pathogens is our poor understanding of the intracellular nutritional environment that maintains bacterial persistence. The intracellular pathogenBrucella abortussurvives and replicates preferentially in alternatively activated macrophages (AAM), however knowledge of the metabolic adaptations promoting exploitation of this niche is limited. Here we show that one mechanism promoting enhanced survival in AAM is a shift in macrophage arginine utilization from production of nitric oxide (NO) to biosynthesis of polyamines, induced by IL-4/IL-13 treatment.B. abortusis unable to synthesize polyamines, however production of polyamines by infected AAM promoted both intracellular survival of bacteria and chronic infection in mice, as inhibition of macrophage polyamine synthesis or inactivation of theB. abortusputrescine transporterpotIHGFreduced both intracellular survival in AAM and persistence in mice. These results demonstrate that increased intracellular availability of polyamines induced by arginase-1 expression in IL-4/IL-13-induced AAM promotes chronic persistence ofB. abortuswithin this niche and suggest that targeting of this pathway may aid in eradicating chronic infection.