Longitudinal profiling of plasma cytokines in melioidosis and their association with mortality: a prospective cohort study.

OBJECTIVES: To characterize plasma cytokine responses in melioidosis and analyse their association with mortality. METHODS: A prospective longitudinal study was conducted in two hospitals in Northeast Thailand to enrol 161 individuals with melioidosis, plus 13 uninfected healthy individuals and 11 uninfected individuals with diabetes to act as controls. Blood was obtained from all individuals at enrolment (day 0), and at days 5, 12 and 28 from surviving melioidosis patients. Interferon-γ (IFN-γ), interleukin-1ß (IL-1ß), IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-17A, IL-23, and tumour necrosis factor-α (TNF-α) were assayed in plasma. The association of each cytokine and its dynamics with 28-day mortality was determined. RESULTS: Of the individuals with melioidosis, 131/161 (81%) were bacteraemic, and 68/161 (42%) died. On enrolment, median levels of IFN-γ, IL-6, IL-8, IL-10, IL-23 and TNF-α were higher in individuals with melioidosis compared with uninfected healthy individuals and all but IFN-γ were positively associated with 28-day mortality. Interleukin-8 provided the best discrimination of mortality (area under the receiver operating characteristic curve 0.78, 95% CI 0.71-0.85). Over time, non-survivors had increasing IL-6, IL-8 and IL-17A levels, in contrast to survivors. In joint modelling, temporal trajectories of IFN-γ, IL-6, IL-8, IL-10 and TNF-α predicted survival. CONCLUSIONS: In a severely ill cohort of individuals with melioidosis, specific pro- and anti-inflammatory and T helper type 17 cytokines were associated with survival from melioidosis, at enrolment and over time. Persistent inflammation preceded death. These findings support further evaluation of these mediators as prognostic biomarkers and to guide targeted immunotherapeutic development for severe melioidosis.

Expression of suppressor of cytokine signaling 3 (SOCS3) and cytokine-inducible Src homology 2-containing protein (CIS) induced in Burkholderia pseudomallei--infected mouse macrophages requires bacterial internalization.

We recently reported that Burkholderia pseudomallei was able to activate the expression of suppressor of cytokine signaling 3 (SOCS3) and cytokine-inducible Src homology 2-containing protein (CIS). In the present study, we presented evidence showing that the induction of these negative regulators was most probably triggered from within rather than at the cell surface of mouse macrophage cell line (RAW264.7) suggesting that macrophage activation most likely requires the interaction of bacteria with a putative host cell cytoplasmic component(s).

Burkholderia pseudomallei-induced expression of suppressor of cytokine signaling 3 and cytokine-inducible src homology 2-containing protein in mouse macrophages: a possible mechanism for suppression of the response to gamma interferon stimulation.

Burkholderia pseudomallei, the causative agent of melioidosis, is a facultative intracellular gram-negative bacterium that is able to survive and multiply in macrophages. Previously, we reported that B. pseudomallei was able to escape macrophage killing by interfering with the expression of inducible nitric oxide synthase (iNOS). In the present study, we extended this finding and demonstrated that B. pseudomallei was able to activate the expression of suppressor of cytokine signaling 3 (SOCS3) and cytokine-inducible Src homology 2-containing protein (CIS) but not SOCS1 in a mouse macrophage cell line (RAW 264.7). The expression of SOCS3 and CIS in B. pseudomallei-infected macrophages directly correlated with a decreased gamma interferon (IFN-gamma) signaling response, as indicated by a reduction in Y701-STAT-1 phosphorylation (pY701-STAT-1). Moreover, a reduction in the expression of IFN-gamma-induced proteins, such as interferon regulatory factor 1 (IRF-1), was observed in B. pseudomallei-infected macrophages that were treated with IFN-gamma. Since pY701-STAT-1 and IRF-1 are essential transcription factors for regulating iNOS expression, the failure to activate these factors could also result in depression of iNOS expression and a loss of macrophage killing capacity. Taken together, the data indicate that the activation of SOCS3 and CIS expression in B. pseudomallei-infected macrophages interfered with IFN-gamma signaling, thus allowing the bacteria to escape killing by these phagocytic cells.