Human Granulocytic Ehrlichiosis in Massachusetts

Telford, Sam R.; Lepore, Timothy J.; Snow, Patricia; Warner, Cynthia K.; Dawson, Jacqueline E.

doi:10.7326/0003-4819-123-4-199508150-00006

Cited by 74 publications

(34 citation statements)

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“…The NCH-1 isolate of A. phagocytophilum was used throughout these studies (16). Blood from rag1-null mice chronically infected with A. phagocytophilum NCH-1 strain (25% neutrophil infection) was used to inoculate immunocompetent C57BL/6 or gene-deficient mice.…”

Section: A Phagocytophilum Detection Methodsmentioning

confidence: 99%

ASC/PYCARD and Caspase-1 Regulate the IL-18/IFN-γ Axis during Anaplasma phagocytophilum Infection

Pedra

Sutterwala

Sukumaran

et al. 2007

The Journal of Immunology

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Anaplasma phagocytophilum is an obligate intracellular pathogen that resides within neutrophils and can cause fever, pancytopenia, or death. IFN-γ plays a critical role in the control of A. phagocytophilum; however, the mechanisms that regulate IFN-γ production remain unclear. In this study, we demonstrate that apoptotic specklike protein with a caspase-activating recruiting domain (ASC)/PYCARD, a central adaptor molecule in the Nod-like receptor (NLR) pathway, regulates the IL-18/IFN-γ axis during A. phagocytophilum infection through its effect on caspase-1. Caspase-1- and asc-null mice were more susceptible than control animals to A. phagocytophilum infection due to the absence of IL-18 secretion and reduced IFN-γ levels in the peripheral blood. Moreover, caspase-1 and ASC deficiency reduced CD4+ T cell-mediated IFN-γ after in vitro restimulation with A. phagocytophilum. The NLR family member IPAF/NLRC4, but not NALP3/NLRP3, was partially required for IFN-γ production in response to A. phagocytophilum. Taken together, our data demonstrate that ASC and caspase-1 are critical for IFN-γ-mediated control of A. phagocytophilum infection.

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Section: A Phagocytophilum Detection Methodsmentioning

confidence: 99%

ASC/PYCARD and Caspase-1 Regulate the IL-18/IFN-γ Axis during Anaplasma phagocytophilum Infection

Pedra

Sutterwala

Sukumaran

et al. 2007

The Journal of Immunology

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“…Salivary glands from transmission-fed I. scapularis nymphs infected with A. phagocytophilum strain NTN-1 (25) preserved in RNAlater (QIAGEN, Valencia, CA) (9) were homogenized with a Kontes pellet pestle motor (Kimble-Kontes, Vineland, NJ) for 3 min, followed by passage through a 26-gauge 0.375-in needle 30 times. Four-week-old ICR SCID male mice (Taconic Farm Inc., Germantown, NY) were inoculated intraperitoneally with 10 6 HL-60 cells infected with A. phagocytophilum strain HZ (80% infected cells).…”

Section: Methodsmentioning

confidence: 99%

Anaplasma phagocytophilum p44 mRNA Expression Is Differentially Regulated in Mammalian and Tick Host Cells: Involvement of the DNA Binding Protein ApxR

et al. 2007

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The natural life cycle of Anaplasma phagocytophilum, an obligatory intracellular bacterium that causes human granulocytic anaplasmosis, consists of alternate infection of two distinct hosts, ticks and mammals, in which bacterial surface proteins are expected to have a critical role. The present study investigated regulation of A. phagocytophilum p44 genes, which encode the P44 major surface proteins. Quantitative real-time reverse transcription-PCR analysis revealed that the amount of p44 mRNA obtained from spleens of A. phagocytophilum-infected SCID mice was approximately 10-fold greater than the amount obtained from salivary glands of A. phagocytophilum-infected Ixodes scapularis nymphs. Similarly, the amount of p44 mRNA obtained from A. phagocytophilum-infected HL-60 cells per bacterium was significantly greater than the amount obtained from infected ISE6 tick cells. The relative amount of p44 mRNA was approximately threefold higher in A. phagocytophilum-infected HL-60 cells cultured at 37°C than in A. phagocytophilum-infected HL-60 cells cultured at 28°C. Although there are more than 100 p44 paralogs, we observed expression mainly from the p44 expression locus (p44E) in various host environments. Interestingly, transcription of the A. phagocytophilum gene encoding the DNA binding protein ApxR was also significantly greater in A. phagocytophilum-infected HL-60 cells than in infected ISE6 tick cells. Gel mobility shift and DNase I protection assays revealed recombinant ApxR binding to the promoter regions of p44E and apxR. ApxR also transactivated the p44E and apxR promoter regions in a lacZ reporter assay. These results indicate that p44 genes and apxR are specifically up-regulated in the mammalian host environment and suggest that ApxR not only is positively autoregulated but also acts as a transcriptional regulator of p44E.The obligatory intracellular bacterium Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis (5, 11), is well adapted to a natural cycle of alternately infecting vertebrates and blood-sucking ticks. A. phagocytophilum surface proteins at the host-pathogen interface are expected to be differentially regulated in the two divergent host environments so that the bacterium can infect and acquire nutrients from the hosts and evade killing by the host immune systems.The polymorphic 44-kDa major outer membrane proteins (P44s, Msp2s) of A. phagocytophilum are the primary bacterial surface-exposed antigens recognized by immune systems of human granulocytic anaplasmosis patients, experimentally infected mice, and horses (8,14,20,30,(33)(34)(35). P44 has been demonstrated to function as a porin, facilitating transport of some sugars and amino acids through the bacterial membrane (13). Notably, 113 p44 genes are present in the A. phagocytophilum genome, including 22 full-length p44 genes, 64 shorter p44 genes (without a start codon), 21 fragmented p44 genes (containing only the 5Ј or 3Ј conserved region), and 6 truncated p44 genes (containing only the hypervariable region) ...

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“…The NCH-1 isolate of aoHGE, which was recovered from a patient with granulocytic ehrlichiosis and has been shown to be infectious in mice, was used throughout these studies (41). aoHGE was initially cultured in HL-60 cells (240-CCL; American Type Culture Collection, Manassas, Va.) grown in Iscove's modified Dulbecco (Gibco BRL/ Life Technologies, Grand Island, N.Y.) medium supplemented with 20% fetal calf serum at 37°C with 5% CO 2 as described earlier (23).…”

Section: Methodsmentioning

confidence: 99%

Gamma Interferon Dominates the Murine Cytokine Response to the Agent of Human Granulocytic Ehrlichiosis and Helps To Control the Degree of Early Rickettsemia

Akkoyunlu

Fikrig

2000

Infect Immun

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The cytokine response to the agent of human granulocytic ehrlichiosis (HGE) was assessed in a murine infection model and the role of gamma interferon (IFN-␥), a cytokine that is crucial for host defenses against intracellular pathogens, was investigated by using IFN-␥-deficient mice. The agent of HGE (aoHGE) is an obligate intracellular bacterium that survives within neutrophils: morulae (vacuoles containing HGE organisms) are evident in polymorphonuclear leukocytes of experimentally infected immunocompetent mice for 1 to 2 weeks. We now show that IFN-␥ levels increase during early infection of C3H/HeN or C57BL/6 mice with HGE bacteria. Moreover, in response to aoHGE extracts or concanavalin A, splenocytes from ehrlichia-infected mice produced more IFN-␥ and less interleukin-4 than controls, suggesting that aoHGE partially skewed the immune response towards a Th1 phenotype. Absolute concentration of morulae containing neutrophils in blood was 122 ؎ 22 cells/l on day 8. The bacterial DNA burden was also highest on day 8 and then declined after IFN-␥ levels peaked. In contrast, IFN-␥-deficient mice had a markedly elevated HGE bacteria burden with morulae concentration of 282 ؎ 48 cells/l on day 5 (P ‫؍‬ 0.004) and 242 ؎ 63 cells/l on day 8 (P ‫؍‬ 0.005). Rickettsemia resolved in immunocompetent and IFN-␥ deficient mice after 2 weeks, while both the immunocompetent and the IFN-␥-deficient mice had increased serum antibodies against aoHGE antigens at this time point. These data demonstrate that the HGE agent elicits a prominent IFN-␥ response in mice and that IFN-␥ is important in controlling the degree of rickettsemia during the early phase of infection, while IFN-␥ independent mechanisms play a role at later time points.

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Human Granulocytic Ehrlichiosis in Massachusetts

Cited by 74 publications

References 0 publications

ASC/PYCARD and Caspase-1 Regulate the IL-18/IFN-γ Axis during Anaplasma phagocytophilum Infection

ASC/PYCARD and Caspase-1 Regulate the IL-18/IFN-γ Axis during Anaplasma phagocytophilum Infection

Anaplasma phagocytophilum p44 mRNA Expression Is Differentially Regulated in Mammalian and Tick Host Cells: Involvement of the DNA Binding Protein ApxR

Gamma Interferon Dominates the Murine Cytokine Response to the Agent of Human Granulocytic Ehrlichiosis and Helps To Control the Degree of Early Rickettsemia

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