STX-1 Non-Human Primate Toxemia Model: Circulating Leukocyte mRNA Changes Coincide with Disease Onset
JF Papin, DJ Stearns-Kurosawa, V Collins, S Freeman, G Peer, S Kurosawa. Boston University School of Medicine, Boston, MA; University of Oklahoma Health Sciences Center, Oklahoma City, OK; College of Veterinary Sciences, Oklahoma State University, Stillwater, OK
Background: Enterohemorrhagic Escherichia coli (EHEC) that produce Shiga-like toxins are an important public health problem and a biodefense concern. EHEC from contaminated water and food lead to the severe conditions of hemorrhagic colitis and hemolytic-uremic syndrome (HUS). The young and elderly are especially vulnerable and HUS survivors often suffer permanent renal damage. Antibiotics are contraindicated, and there is no specific treatment, other than general supportive care. The primary virulence factors are circulating Shiga-like toxins 1 and 2 (STX-1, STX-2). To accelerate the development of novel therapeutics, we are developing and characterizing a pre-clinical, non-human primate model for Shiga toxemia.
Design: Toxemia was induced by i.v. 100ng/kg STX-1 to anesthetized baboons, Papio cynocephalus (n=5) with lethal outcome at 48 72 hours. Quantitative PCR (qPCR) assays were designed from baboon sequences to follow expression of TNF, IL-6, IL-8, IL-12p35, MIP-1, MCP-1, Elastase-2 (neutrophil elastase), and VEGF in the blood during STX-1 toxemia. RNA was isolated from peripheral blood leukocytes (PBL) obtained from timed heparinized blood samples and used to generate target cDNA for the qPCR.
Results: The clinical manifestations included bloody diarrhea, oliguria, thrombocytopenia without fibrinogen depletion, microangiopathic hemolytic anemia (MAHA) with schistocytes. There was increased expression of TNF (4/5 baboons), IL-6 (3/5), IL-8 (5/5), MIP-1(5/5), and MCP-1 (4/5) in the PBLs. The expression of TNF, IL-6, IL-8, MIP-1, Elastase-2, and MCP-1 all showed marked increase at 24 hours post exposure that continued to increase through the 48-hour time point. On average, we observed 5 to 10 fold increases in expression in these cytokines, with the exception of MCP-1 which demonstrated a 20-40 fold increase.
Conclusions: The clinical manifestations in our baboon model recapitulate many of the characteristics in patients. Our findings in the baboon model show a marked increase of pro-inflammatory cytokine expressions in PBLs at 24 to 48 hours-post exposure to STX1. Notably, this burst of cytokine expression corresponds to the onset of thrombocytopenia, oliguria and MAHA, suggesting a direct role in the pathogenesis. [NIH UO1AI075386 (SK)]
Monday, March 9, 2009 1:00 PM
Poster Session II # 202, Monday Afternoon