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Host resistance of mice to Naegleria fowleri infections
Abstract:
Naegleria fowleri is an etiological agent of primary amoebic meningoencephalitis in humans and laboratory animals. The determinative factors in host resistance of mice to N. fowleri infections have not been fully characterized. Male or female B6C3F1 mice stimulated by intraperitoneal administration of 10(6) amoebae of N. fowleri nN68 per mouse produced agglutinating activity and markedly elevated levels of serum and immunoglobulins M and G. Despite a marked humoral response, protective immunity was increased only marginally by active immunization. Host resistance was not impaired by prior treatment with 350 rads of 60Co radiation or 200 mg of cyclophosphamide per kg or by concurrent daily treatment with 30 mg of cyclophosphamide per kg for 14 days. Moreover, host resistance was not impaired by daily treatment with 4 mg of diethylstilbestrol per kg for 14 days, with challenge on day 2 of drug exposure or 24 h after the last drug treatment. Mice depleted of hemolytic complement by cobra venom factor were more susceptible to N. fowleri infection than were untreated mice.
Insights
Naegleria fowleri infection in mice elicits a strong antibody response but limited protective immunity. Host resistance is not significantly affected by radiation, cyclophosphamide, or diethylstilbestrol, but complement depletion increases susceptibility.
Area of Science:
- Immunology
- Infectious Diseases
- Parasitology
Background:
- Naegleria fowleri causes primary amoebic meningoencephalitis.
- Factors influencing host resistance to N. fowleri are not fully understood.
Purpose of the Study:
- To investigate host resistance mechanisms in mice against Naegleria fowleri.
- To evaluate the impact of active immunization and immunosuppressive agents on N. fowleri infection.
Main Methods:
- Mice were infected with N. fowleri and immune responses were measured.
- Immunization, radiation, cyclophosphamide, diethylstilbestrol, and complement depletion were employed.
- Host resistance was assessed through survival rates and infection severity.
Main Results:
- Active immunization induced agglutinating activity and elevated immunoglobulins M and G, but only marginally increased protective immunity.
- Host resistance was not impaired by radiation, cyclophosphamide, or diethylstilbestrol treatments.
- Mice depleted of hemolytic complement showed increased susceptibility to N. fowleri infection.
Conclusions:
- A strong humoral response does not guarantee robust protection against Naegleria fowleri.
- Complement plays a crucial role in host defense against N. fowleri.
- Further research is needed to identify effective strategies for combating primary amoebic meningoencephalitis.