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Monophosphoryl lipid A as a prophylactic for sepsis and septic shock
G L Gustafson1, M J Rhodes, T Hegel
1Ribi ImmunoChem Research, Inc., Hamilton, MT 59840, USA.
Abstract:
The ability of monophosphoryl lipid A (MLA) to provide prophylactic protection against septic shock was evaluated in a mouse model of induced endotoxin hypersensitivity. Treatments of hypersensitized animals with low doses of MLA attenuated endotoxin lethality and endotoxin-mediated liver damage. These effects were related to the ability of MLA to suppress accumulation of TNF-alpha and IFN-gamma in the bloodstream of animals. MLA treatments had only a modest effect in suppressing the accumulation of nitrate in the bloodstream. This implied that MLA did not suppress induction of macrophage and hepatocyte nitric oxide synthetases that contribute to antimicrobial defense and protect against endotoxin-mediated liver damage. The MLA treatments did not appear to compromise inflammatory defenses against local infection since locally recruited leukocytes remained responsive to endotoxin after hypersensitivity had been attenuated. In agreement with these findings, other studies have shown that the induction of endotoxin tolerance by MLA parallels the induction of resistance of animals to lethal challenges with either Gram negative or Gram positive bacteria. As predicted from preclinical studies, human trials of the clinical form of MLA (MPL-immunostimulant) have confirmed that MLA could attenuate systemic responses to endotoxin in normal volunteers, including the attenuation of blood cytokine accumulation and attenuation of symptomatic responses.
Insights
Monophosphoryl lipid A (MLA) protects against septic shock by reducing endotoxin lethality and liver damage in mice. This immune-modulating effect, observed in preclinical and human studies, involves suppressing key inflammatory cytokines.
Area of Science:
- Immunology
- Pharmacology
- Toxicology
Background:
- Septic shock is a life-threatening condition caused by an overwhelming immune response to infection.
- Monophosphoryl lipid A (MLA) is a detoxified derivative of lipopolysaccharide (LPS) known for its immune-modulating properties.
- Understanding MLA's protective mechanisms against endotoxin is crucial for developing effective sepsis treatments.
Purpose of the Study:
- To evaluate the prophylactic efficacy of monophosphoryl lipid A (MLA) against endotoxin-induced septic shock in a mouse model.
- To investigate the specific molecular mechanisms underlying MLA's protective effects, focusing on cytokine and nitric oxide production.
- To assess whether MLA treatment compromises local inflammatory responses or innate immune defenses.
Main Methods:
- A mouse model of endotoxin hypersensitivity was established to mimic septic shock conditions.
- Hypersensitized mice were treated with low doses of MLA, and their survival rates were monitored.
- Levels of tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and nitrate in the bloodstream were quantified.
- Leukocyte responsiveness to endotoxin in local infections was assessed post-MLA treatment.
Main Results:
- MLA treatment significantly attenuated endotoxin lethality and reduced endotoxin-mediated liver damage in hypersensitized mice.
- MLA suppressed the accumulation of TNF-alpha and IFN-gamma in the bloodstream, correlating with its protective effects.
- MLA showed only a modest effect on nitrate levels, suggesting preserved nitric oxide synthetase activity.
- MLA did not compromise local inflammatory defenses, as leukocytes remained responsive to endotoxin.
Conclusions:
- Monophosphoryl lipid A (MLA) demonstrates significant prophylactic protection against endotoxin-induced septic shock and associated liver damage.
- MLA's efficacy is linked to its ability to suppress key pro-inflammatory cytokines like TNF-alpha and IFN-gamma.
- MLA treatment appears to preserve essential antimicrobial defense mechanisms, including nitric oxide production and local leukocyte function.