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Immunization of mice against Naegleria fowleri infection
Abstract:
Naegleria fowleri produces fatal meningoencephalitis in humans and in experimentally infected laboratory animals. The course of the disease in mice is dependent upon the infecting dose of amoebae, route of inoculation, and prior exposure to Naegleria antigens. DUB/ICR mice were immunized by various routes and antigen preparations, held for 21 days, and, together with noninfected control mice, challenged intravenously (i.v.) or intranasally (i.n.) with 10(7) or 10(6) N. fowleri per mouse, respectively. Mice immunized with liver or formalinized N. fowleri or live N. gruberi subcutaneously, intraperitoneally, i.v., or i.n. were significantly protected against a subsequent lethal challenge with N. fowleri i.v. or i.n. In general, i.v. inoculation afforded greated protection than other routes of immunization, intact cells immunized mice better than did cell fragments, and N. gruberi appeared to be a better immunogen than N. fowleri.
Insights
Immunization with Naegleria antigens, particularly via intravenous inoculation, significantly protected mice against fatal Naegleria fowleri meningoencephalitis. Live Naegleria gruberi proved a more effective immunogen than Naegleria fowleri.
Area of Science:
- Immunology
- Parasitology
- Neuroscience
Background:
- Naegleria fowleri causes fatal primary amoebic meningoencephalitis (PAM) in humans.
- Disease severity in experimental models depends on infection dose, route, and prior antigen exposure.
Purpose of the Study:
- To evaluate the protective efficacy of various immunization strategies against Naegleria fowleri infection in mice.
- To determine the optimal route and antigen preparation for inducing protective immunity.
Main Methods:
- DUB/ICR mice were immunized using different routes (subcutaneous, intraperitoneal, intravenous, intranasal) and antigen preparations (liver, formalinized N. fowleri, live N. gruberi).
- Mice were challenged intravenously or intranasally with lethal doses of N. fowleri after a 21-day immunization period.
- Control groups received no immunization.
Main Results:
- Immunization with liver or formalinized N. fowleri, or live N. gruberi, conferred significant protection against lethal N. fowleri challenge via both intravenous and intranasal routes.
- Intravenous inoculation generally provided superior protection compared to other immunization routes.
- Intact amoebic cells were more effective immunogens than cell fragments.
- Naegleria gruberi demonstrated better immunogenicity than Naegleria fowleri.
Conclusions:
- Pre-exposure to Naegleria antigens can induce significant protection against experimental Naegleria fowleri infection.
- Intravenous immunization with intact cells, particularly using Naegleria gruberi, is a promising strategy for developing prophylaxis against PAM.