Anti-Ehrlichia chaffeensis antibody complexed with E. chaffeensis induces potent proinflammatory cytokine mRNA expression in human monocytes through sustained reduction of IkappaB-alpha and activation of NF-kappaB

Abstract

Ehrlichia chaffeensis is an obligatory intracellular bacterium that infects monocytes and macrophages and is the etiologic agent of human ehrlichiosis in the United States. Our previous studies showed that the exposure of human monocytes to E. chaffeensis induces the expression of interleukin-1␤ (IL-1␤), IL-8, and IL-10 genes in vitro but not the expression of tumor necrosis factor alpha (TNF-␣) and IL-6 mRNAs. In this study, the effect of anti-E. chaffeensis antibody complexed with E. chaffeensis on the expression of major proinflammatory cytokines in human monocytes was examined. Human monocytic cell line THP-1 was treated with E. chaffeensis which had been preincubated with human anti-E. chaffeensis serum for 2 h, and the levels of cytokine mRNAs were evaluated by competitive reverse transcription-PCR. Anti-E. chaffeensis antibody complexed with E. chaffeensis significantly enhanced mRNA expression of IL-1␤ in THP-1 cells. The expression of TNF-␣ and IL-6 mRNAs was also induced. The levels of secreted IL-1␤, TNF-␣, and IL-6 during 24 h of stimulation were comparable to those induced by Escherichia coli lipopolysaccharide at 1 g/ml. Fab fragment of anti-E. chaffeensis immunoglobulin G complexed with E. chaffeensis did not induce any of these three cytokines, indicating that ehrlichial binding is required for IL-1␤ mRNA expression and that binding of the immune complex to the Fc␥ receptor is required for TNF-␣ and IL-6 mRNA expression and enhanced IL-1␤ mRNA expression. Furthermore, prolonged degradation of IB-␣ and activation of NF-B were demonstrated in THP-1 cells exposed to anti-E. chaffeensis serum and E. chaffeensis. This result implies that development of anti-E. chaffeensis antibody in patients can result in the production of major proinflammatory cytokines, which may play an important role in the pathophysiology of ehrlichiosis and immune responses to it.

Human Ehrlichiosis in Transplant Recipients

“…The reason for these findings is unknown, although there is evidence to suggest that some of the pathophysiological effects related to E. chaffeensis are host‐mediated. Human monocytes, when exposed to E. chaffeensis , have been shown to produce proinflammatory cytokines such as tumor necrosis factor alpha (TNF‐α), interleukin‐1β (IL‐1β) and IL‐6, particularly in the presence of anti‐ E. chaffeensis antibodies (24,25).…”

Protein Kinase A-Mediated Inhibition of Gamma Interferon-Induced Tyrosine Phosphorylation of Janus Kinases and Latent Cytoplasmic Transcription Factors in Human Monocytes byEhrlichia chaffeensis

“…For the reversibility experiment, PMA-treated cells were stimulated with IFN-␥ for 10 min and then incubated with viable E. chaffeensis organisms for 30 min. Fab fragment of normal dog antibody or dog anti-E. chaffeensis antibody was prepared as described previously (19). PMA-treated cells were incubated with viable E. chaffeensis organisms which had been preincubated with 0.2 mg of Fab fragment of normal antibody or anti-E. chaffeensis antibody at 37°C for 30 min and then stimulated with IFN-␥ for 10 min.…”

The Expression Profile of Lipopolysaccharide‐Binding Protein, Membrane‐Bound CD14, and Toll‐Like Receptors 2 and 4 in Chronic Periodontitis

“…The primers used to amplify the human LBP gene were 59 AGG GCC TGA GTC TCA GCA TCT 39 (sense) and 59 CAG GCT GGC CGT GTT GAA GAC 39 (antisense) 17 ; and human CD14 primers were 59 CAA CTT CTC CGA ACC TCA GC 39 (sense) and 59 TAG GTC CTC GAG CGT CAG TT 39 (antisense). 18 b-actin gene was amplified by using primer 59 GCT CGT CGT CGA CAA CGG CTC 39 (sense) and 59 CAA ACA TGATCT GGG TCA TCT TCT C 39 (antisense) 19 as an internal standard. The cycling conditions used were initial denaturation at 94°C for 5 minutes; 40 cycles of 94°C for 1 minute, 55°C (LBP) for 1 minute/57°C (CD14) for 1 minute, and 72°C for 90s; and a final extension at 72°C for 10 minutes.…”