Simulated systemic recurrent Mycoplasma infection in rats induces recurrent sickness responses without residual
Tanya Swanepoel1, Brian H Harvey, Lois M Harden
1Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa. Tanya.Swanepoel@wits.ac.za
Abstract:
In spite of their prevalence and importance, recurrent acute infections seldom have been investigated in the laboratory. We set out to measure fever and sickness behaviour in simulated recurrent Mycoplasma infection; Mycoplasma is a common clinical cause of recurrent acute infection. Male Sprague-Dawley rats had radiotransponders implanted to measure abdominal temperature and cage activity. After recovery, rats received three intraperitoneal (I.P.) injections, 10 days apart, of either fibroblast-stimulating lipopeptide-1 (FLS-1), a pyrogenic moiety of Mycoplasma salivarium, at a dose of 500 μg.kg(-1) in 1 ml.kg(-1) phosphate-buffered saline (PBS), or vehicle (PBS, 1 ml.kg(-1)). Body mass and food intake were measured daily. For measurement of learning and memory, training in a Morris Water Maze commenced 10 days after the last of the three successive injections and continued daily for 4 days. Spatial memory was assessed on the following day. Hippocampal tissue of rats was collected on the day of the last exposure to the maze. Recurrent FSL-1 administration induced recurrent fevers (~1°C) for about 9h, recurrent lethargy (~40-60%) for 1 day, recurrent anorexia (~16-30%) for 1 day, and recurrent reductions in the rate of mass gain (~112%) for 1 day, but did not induce persistent stunting. Recurrent FSL-1 administration did not result in tolerance to fever, lethargy or anorexia. There was no residual histological damage to the hippocampus and no residual detrimental effect in learning or memory in rats. Though we cannot extrapolate our results directly to humans, clinical recurrent acute Mycoplasma infection may not impose a high risk of stunting or impaired spatial learning and memory.
Insights
Recurrent Mycoplasma infections in rats caused temporary fever and sickness behaviors but no lasting harm to learning or memory. These findings suggest clinical recurrent acute Mycoplasma infection may pose low risk for stunting or cognitive impairment.
Area of Science:
- Immunology
- Neuroscience
- Infectious Diseases
Background:
- Recurrent acute infections are common but understudied in laboratory settings.
- Mycoplasma species are frequent causes of recurrent acute infections in clinical practice.
Purpose of the Study:
- To investigate fever and sickness behavior in a rat model of simulated recurrent Mycoplasma infection.
- To assess the impact of recurrent infection on learning, memory, and physical development.
Main Methods:
- Male Sprague-Dawley rats received repeated intraperitoneal injections of fibroblast-stimulating lipopeptide-1 (FLS-1) or vehicle.
- Body temperature, activity, body mass, and food intake were monitored daily.
- Learning and spatial memory were evaluated using the Morris Water Maze, with hippocampal tissue collected for histological analysis.
Main Results:
- Recurrent FLS-1 administration induced transient fevers, lethargy, anorexia, and reduced mass gain, without causing stunting.
- No tolerance developed to the induced sickness behaviors.
- No histological damage to the hippocampus or lasting deficits in learning and memory were observed.
Conclusions:
- Simulated recurrent Mycoplasma infection in rats leads to temporary sickness responses but does not cause persistent physical or cognitive impairment.
- Clinical recurrent acute Mycoplasma infection may not significantly risk stunting or affect spatial learning and memory.
