The model

During experimental human endotoxemia, we challenge healthy human subjects intravenously with purified endotoxin (lipopolysaccharide (LPS)).

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The model

During experimental human endotoxemia, we challenge healthy human subjects with purified endotoxin (lipopolysaccharide (LPS)) intravenously which induces a short-lived, well-tolerated and controlled systemic inflammatory response, similar to that observed during sepsis. The human endotoxemia model can be conducted in a highly standardized and reproducible manner, using a carefully selected homogenous study population.

The model has proven to be safe, well-tolerated and without any known long-term health risks for the participating subjects. Intravenous endotoxin administration elicits a transient and controlled systemic inflammatory response, clinically characterized by an increase in core temperature of approximately 1.5–2 °C, flu-like symptoms (such as headache, chills, fatigue, myalgia, backache, and nausea) during 2–4 h, as well as hemodynamic alterations (tachycardia, tachypnea, and decrease in blood pressure).


Call for volunteers for endotoxemia research

Frequently we are recruiting for healthy volunteers (18-35) for an endotoxemia study. Do you want to participate? Or do you want to receive more information about our studies? register

Application of the model

Systemic inflammation plays a pivotal role in a multitude of conditions, including sepsis, trauma, major surgery and burns. However, comprehensive analysis of the pathophysiology underlying this systemic inflammatory response is greatly complicated by variations in the immune response observed in critically ill patients, which are a result of inter-individual differences in comorbidity, comedication, source of infection, causative pathogen, and onset of the inflammatory response. This heterogeneity between patients impedes evaluation of pathophysiological mechanisms and hampers accurate comparison of (pharmacological) interventions. As a consequence, large numbers of patients need to be included in clinical trials to demonstrate intervention efficacy. Strikingly, even when these numbers were met, many of the positive results found in preclinical (animal) studies of systemic inflammation could not be reproduced in expensive (phase III) clinical trials. Therefore, an intermediate step is highly warranted to improve translation of preclinical animal data to sepsis patients.
The experimental human endotoxemia model can be used to overcome the aforementioned constraints of translating preclinical results into clinical practice.
The human endotoxemia model can be conducted in a highly standardized and reproducible manner, using a carefully selected homogenous study population. As such, the experimental human endotoxemia model does not share the aforementioned clinical limitations and enables us to investigate both the mechanisms of systemic inflammation, as well as to evaluate novel (pharmacological) interventions in humans in vivo. 

Endotoxemia challenge in healthy volunteers

After approval of the local ethics committee and written informed consent, all subjects are thoroughly screened prior to inclusion (using medical history, physical examination, laboratory tests, and a 12-leads electrocardiogram). The procedure and general requirements for conducting a endotoxemia challenge are as follows:
  • On the day of the experiment, subjects are hospitalized and receive one or two (18 gauge) venous catheters to accommodate infusion of endotoxin, fluids, and (if applicable) study medication
  • Subsequently, an arterial catheter is placed, preferably in the radial artery of the non-dominant arm, for frequent blood withdrawals and blood pressure monitoring.
  • Vital signs are continuously monitored during the experiment using 3-lead electrocardiography, peripheral pulse-oximetry, and the intra-arterial blood pressure signal.
  • Body temperature (determined using an ear thermometer) and severity of symptoms are determined every half hour.
  • Approximately 1 hour prior to endotoxin administration, subjects are prehydrated with 1.5 L Sodium Chloride 0.45%/Glucose 2.5% solution, as this is known to reduce the risk of a vasovagal reaction following endotoxemia. Hereafter, fluid administration is continued at a rate of 150 mL/h until the end of the experiment.
  • Arterial blood is drawn at baseline and serially during the endotoxemia to determine leukocyte differentiation and cytokine concentration over time.

Depending on the research questions proposed, the evaluation of numerous parameters and/or (pharmacological) interventions can be added to the protocol.

LPS = lipopolysaccharide, BP = blood pressure, ECG = electrocardiography, NaCl = Sodium chloride

Our Projects

  • Safety en tolerability of EA-230

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    Current projects

    Safety en tolerability of EA-230

    Aim and methods: The goal of this randomized, double-blind, placebo-controlled study is to investigate the safety, tolerability, pharmacodynamics and pharmacokinetics of the novel compound EA-230, a newly developed compound which is derived from the human chorionic gonadotropin hormone (hCG). This iss conducted in a phase 1 trial followed by a phase 2a trial using the experimental human endotoxemia model in 36 healthy human volunteers.


  • Completed studies

    Safety en tolerability of Adrecizumab (2018)

    Aim and methods: To investigate the safety, tolerability, pharmacodynamics and pharmacokinetics of the adrenomedullin-binding antibody Adrecizumab during experimental human endotoxemia in a randomized, double-blind, placebo-controlled manner in 24 healthy human volunteers.

    Conclusion: Administration of Adrecizumab was safe and well tolerated in the presence of systemic inflammation. These findings pave the way for further investigation of Adrecizumab in sepsis patients.


    Aspirin and systemic inflammation (2018)

    Aim and methods: To investigate immunostimulatory effects of acetylsalicylic acid (aspirin) during systemic inflammation and endotoxin tolerance. Healthy volunteers were randomized to receive either 80mg acetylsalicylic acid or placebo and subsequently challenged with endotoxin twice, at a 1-week interval.

    Conclusion: Treatment with low-dose acetylsalicylicacid partially reverses endotoxin tolerance in humans in vivo by shifting response toward a proinflammatory phenotype.


    Hypoxia and the cytokine response (2018)

    Aim and methods: In vitro and animal studies have shown different, opposing effects of hypoxia on the innate immune response. Meanwhile, there is a trend towards  more conservative oxygen strategies in patients in the Emergency Department and Intensive Care Unit with acute inflammatory diseases such as sepsis. We studied the effect of short term hypoxia (SpO2 80-85% for 3.5 hours) on the cytokine response after endotoxin administration in healthy subjects.

    Conclusion: Short term hypoxia results in a strong, early augmentation of the anti-inflammatory interleukin-10 and a subsequent attenuation of pro-inflammatory cytokines.


    Ticagrelor, clopidogrel and immunomodulation (2017)

    Aim and methods: In post-hoc analysis from randomized controlled trials, sepsis-related mortality appears to be lower in post-myocardial infarction patients treated with ticagrelor when compared to those treated with clopidogrel.  We investigated whether ticagrelor, when compared to clopidogrel, both in combination with acetylsalicylic acid, has immunomodulating effects that may explain these differences. Healthy volunteers were treated with placebo, monotherapy acetylsalicylic acid, ticagrelor-acetylsalicylic acid or clopidogrel-acetylsalicylic acid. At day 7 a cytokine response was induced by endotoxin administraton.
    Conclusion: Monotherapy acetylsalicylic acid augmented the pro-inflammatory cytokine response compared to placebo. There was no relevant effect on the cytokine response of neither ticagrelor nor clopidogrel.


    Vasopressors and the innate immune response (2016)

    Aim and methods: To ascertain the effects of vasopressors on the innate immune response in vivo, 40 healthy male volunteers were randomized to receive a 5-hour infusion of either noradrenaline (0.05µg/kg/min), phenylephrine (0.5µg/kg/min), vasopressin (0.04 IU/min) or placebo (NaCl 0.9%) in a double blinded manner. 1 hour after the start of the vasopressor infusion they were given an LPS bolus (2ng/kg) to elicit a systemic inflammatory response.

    Conclusion: Both noradrenaline and phenylephrine induced significantly higher circulating levels of the anti-inflammatory cytokine IL-10, and significantly lower levels of pro-inflammatory chemokines MIP-1β and CXCL-10, compared to placebo. Vasopressin did not significantly influence the cytokine levels in this trial, compared to placebo. Noradrenaline and phenylephrine shift the balance towards an anti-inflammatory phenotype during human experimental endotoxemia in vivo.


Our people

Contact Endotoxemia models

Peter Pickkers MD PhD
Professor of Experimental Intensive Care Medicine


Contact Endotoxemia models

Pleun Hemelaar MSc
Manager research