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Open Access Research

Ixodes scapularis saliva mitigates inflammatory cytokine secretion during Anaplasma phagocytophilum stimulation of immune cells

Gang Chen1, Maiara S Severo1, Mohammad Sohail1, Olivia S Sakhon1, Stephen K Wikel23, Michail Kotsyfakis4 and Joao HF Pedra1*

Author Affiliations

1 Center for Disease Vector Research and Department of Entomology, University of California-Riverside, Riverside, CA, 92521, USA

2 Department of Pathology, Center for Biodefense and Emerging Infectious Diseases and Center for Tropical Diseases, School of Medicine, University of Texas Medical Branch, Galveston, TX, 77555, USA

3 Department of Medical Sciences, Quinnipiac University, Hamden, CT, 06518, USA

4 Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic

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Parasites & Vectors 2012, 5:229  doi:10.1186/1756-3305-5-229

Published: 10 October 2012

Abstract

Background

Ixodes scapularis saliva enables the transmission of infectious agents to the mammalian host due to its immunomodulatory, anesthetic and anti-coagulant properties. However, how I. scapularis saliva influences host cytokine secretion in the presence of the obligate intracellular rickettsial pathogen Anaplasma phagocytophilum remains elusive.

Methods

Bone marrow derived macrophages (BMDMs) were stimulated with pathogen associated molecular patterns (PAMPs) and A. phagocytophilum. Cytokine secretion was measured in the presence and absence of I. scapularis saliva. Human peripheral blood mononuclear cells (PBMCs) were also stimulated with Tumor Necrosis Factor (TNF)-α in the presence and absence of I. scapularis saliva and interleukin (IL)-8 was measured.

Results

I. scapularis saliva inhibits inflammatory cytokine secretion by macrophages during stimulation of Toll-like (TLR) and Nod-like receptor (NLR) signaling pathways. The effect of I. scapularis saliva on immune cells is not restricted to murine macrophages because decreasing levels of interleukin (IL)-8 were observed after TNF-α stimulation of human peripheral blood mononuclear cells. I. scapularis saliva also mitigates pro-inflammatory cytokine response by murine macrophages during challenge with A. phagocytophilum.

Conclusions

These findings suggest that I. scapularis may inhibit inflammatory cytokine secretion during rickettsial transmission at the vector-host interface.

Keywords:
Tick; Ixodes scapularis; Saliva; Anaplasma phagocytophilum; Rickettsial agent