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Oocyst production and immunogenicity of Cryptosporidium muris (strain MCR) in mice
1Department of Parasitology, School of Veterinary Medicine, Chonbuk National University, Chonju, Korea.
Abstract:
Three-week-old ICR SPF mice were orally inoculated with one of 5 doses ranging from 2 x 10(2) to 2 x 10(6) oocysts of Cryptosporidium muris (strain MCR) per mouse. Oocyst inoculation was directly proportional to the amount of oocysts shed and was inversely proportional to the period required for peak oocyst production and to the prepatent period. Peak oocyst production occurred between fifteen and thirty-one days with a patent period from 61 to 64 days. Three days after all mice stopped shedding oocysts, they were orally challenged with a single dose of 2 x 10(6) oocysts of the same species. Marked seroconversion for IgG antibody accompanied recovery from mice inoculated with 5 x 10(5) oocysts. Mice administered with carrageenan excreted a small number of oocysts for 49.0 days on the average after challenge inoculation (ACI) and control mice for 14.2 days in a dose-independent fashion. Just before challenge infection, phagocytic activity of peritoneal macrophages (M phi) and the number of peripheral M phi were dramatically decreased. Mild challenge infection implies that the immunogenicity of C. muris (strain MCR) is very strong, despite M phi blocker carrageenan administration.
Insights
Cryptosporidium muris infection dose impacts oocyst shedding and recovery time in mice. Even with suppressed immune cells, mice showed strong antibody responses, indicating robust immunity against this parasite.
Area of Science:
- Immunology
- Parasitology
- Microbiology
Background:
- Cryptosporidium muris is an opportunistic protozoan parasite.
- Understanding the host immune response to C. muris is crucial for developing effective treatments and vaccines.
- The impact of varying oocyst doses on infection dynamics and immune response requires further investigation.
Purpose of the Study:
- To investigate the dose-dependent effects of Cryptosporidium muris (strain MCR) inoculation on mice.
- To evaluate the host's immune response, including antibody production and macrophage activity, following infection and challenge.
- To assess the influence of macrophage activity suppression on parasite shedding and host recovery.
Main Methods:
- Mice were orally inoculated with five different doses of C. muris oocysts.
- Oocyst shedding, patent period, and peak production were monitored.
- Mice were subsequently challenged with a high dose of oocysts, and immune responses (IgG antibody, macrophage activity) were assessed.
Main Results:
- Oocyst inoculation dose was directly proportional to oocyst shedding and inversely proportional to prepatent and peak production periods.
- Marked IgG antibody seroconversion was observed in mice inoculated with 5 x 10^5 oocysts.
- Carrageenan administration (macrophage blocker) prolonged oocyst shedding post-challenge, but mice still mounted a strong immune response.
Conclusions:
- The dose of C. muris oocysts significantly influences infection kinetics in mice.
- Despite temporary suppression of macrophage activity, C. muris (strain MCR) demonstrates strong immunogenicity, leading to effective antibody-mediated recovery.
- This suggests a robust adaptive immune response capable of overcoming even pharmacologically impaired innate immunity.