Pro-inflammatory immune responses are associated with clinical signs and symptoms of human anaplasmosis.

Human anaplasmosis (HA) is an emerging tick-borne disease that may present as a mild flu-like illness or a life threatening, sepsis-like condition. Although disease severity is hypothesized to relate to immunopathology and immune dysfunction in humans, studies to directly measure immune responses in infected humans have been very limited. We quantified cytokines in 80 confirmed HA patients using a multiplex chemiluminescence immunoassay system and compared similarly measured responses in 1000 control subjects. Pro-inflammatory cytokines were significantly elevated in HA patients (all seven p<0.0001). Interferon gamma (IFN-γ) concentrations were particularly high, with average concentrations 7.8 times higher in the HA patients than the controls. A subset of cytokines consisting of IL-1ß, IL-8, IL-6, TNF-α, and IL-10 was also coordinately high and significantly associated with severity of thrombocytopenia in HA patients. Patients with infections in the very acute stage (≤ 4 days ill) tended to have the highest IFN-γ, IL-12p70, and IL-2 levels. Higher concentrations of IL-13 and IL-5 were associated with diarrhea and vomiting. Our findings support a pathophysiological role for a pro-inflammatory response in HA, especially with regard to the modulation of hematopoiesis and subsequent hematopoietic complications.

Superoxide anion production during Anaplasma phagocytophila infection.

Anaplasma phagocytophila persists within neutrophils and prevents the respiratory burst by inhibiting gp91(phox). Mutations in gp91(phox) result in chronic granulomatous disease (CGD), which is diagnosed by use of the nitroblue tetrazolium (NBT) and Fc-Oxyburst assays that examine whether cells produce O2-. This study assessed whether the NBT and Fc-Oxyburst assays could detect a respiratory burst during A. phagocytophila infection. O2- production was inhibited in HL-60 cells and neutrophils infected with A. phagocytophila. In a mouse model of A. phagocytophila infection, 15%+/-4% (mean+/-SD) of polymorphonuclear leukocytes from infected mice had an ineffective respiratory burst compared with 1%+/-1% (mean+/-SD) of the neutrophils from uninfected animals. A population of neutrophils that did not produce O2- was also detected in 2 patients with A. phagocytophila infection. These data demonstrate respiratory burst inhibition by A. phagocytophila in vivo and on an individual cell basis by use of assays designed to evaluate CGD.