Amelioration of experimental bacterial meningitis by levamisole: evidence of a direct effect on the infecting bacteria
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Abstract:
The immune-modulating effects of levamisole were evaluated in vivo in rabbits with experimental meningitis due to Escherichia coli and in vitro in assays of ingestive and digestive functions of polymorphonuclear leukocytes. Intracisternal treatment of rabbits with 0.5 ml of levamisole (400 micrograms/ml) 48 and 24 hr before infection resulted in a longer survival time (mean, 49.3 hr) than either control (mean, 21.3 hr; P < 0.01) or intravenously treated animals (mean, 18.3 hr; P < 0.05). However, treatment of the organism by incubation in levamisole (100 micrograms/ml) resulted in survival times significantly longer than that of intracisternally treated animals (mean, 98.5 hr; P < 0.05). A reduction of 5 logs of viable bacteria 22 hr after infection was noted by previous therapy of either the animal or the bacteria. No antibiotic effect was demonstrated. In vitro studies revealed increased ingestion by polymorphonuclear leukocytes (P < 0.02) and digestion (P < 0.05) of bacteria incubated in levamisole. These results suggest that levamisole may alter the bacteria, enhance killing, and produce salutary in vivo effects.
Insights
Levamisole enhances immune response against Escherichia coli meningitis in rabbits by improving polymorphonuclear leukocyte function. This immunomodulation increases survival time and bacterial clearance without direct antibiotic effects.
Area of Science:
- Immunology
- Pharmacology
- Microbiology
Background:
- Bacterial meningitis, particularly from Escherichia coli, poses significant health risks.
- Levamisole is known for its immune-modulating properties.
- Understanding levamisole's effects on host defense mechanisms is crucial.
Purpose of the Study:
- To evaluate the in vivo and in vitro immune-modulating effects of levamisole.
- To assess levamisole's efficacy in experimental Escherichia coli meningitis in rabbits.
- To investigate levamisole's impact on polymorphonuclear leukocyte functions.
Main Methods:
- In vivo study: Rabbits with experimental Escherichia coli meningitis were treated with levamisole intracisternally and intravenously.
- In vitro study: Polymorphonuclear leukocytes and Escherichia coli were incubated with levamisole.
- Survival rates and bacterial load were measured.
Main Results:
- Intracisternal levamisole treatment significantly increased rabbit survival time compared to controls.
- Pre-treatment of bacteria with levamisole also led to significantly longer survival times.
- In vitro, levamisole enhanced polymorphonuclear leukocyte ingestion and digestion of bacteria.
- No direct antibiotic effect of levamisole was observed.
Conclusions:
- Levamisole demonstrates significant immunomodulatory effects in experimental meningitis.
- Levamisole enhances host immune response by improving phagocytic cell function.
- These findings suggest levamisole's potential therapeutic value in combating bacterial infections.