Analysis of the immune response to Neospora caninum in a model of intragastric infection in mice

Abstract

To study experimental Neospora caninum infection initiated at the gastrointestinal tract, Toll-like Receptor 4- and functional IL-12Rbeta2 chain-deficient C57BL/10 ScCr mice were challenged intragastrically with 5 x 10(6) N. caninum tachyzoites. All parasite-inoculated mice eventually died with disseminated infection. In contrast, immunocompetent BALB/c mice challenged with 1 x 10(7) N. caninum tachyzoites by the intragastric (i.g.) or the intraperitoneal (i.p.) route remained alive for at least 6 months. Expansion of splenic B- and T-cells, the latter displaying both activated and regulatory phenotypes, and increased levels of IFN-gamma and IL-10 mRNA were detected in both groups of infected BALB/c mice compared with non-infected controls, whereas in the Peyer's patches only IFN-gamma mRNA levels were found to be increased. Parasite-specific IgG1, IgG2a and IgA antibody levels were elevated in the sera of all infected mice, whereas increased N. caninum-specific IgA levels were detected in intestinal lavage fluids of i.g. challenged mice only. These results show that N. caninum infection can be successfully established in mice by i.g. administration of tachyzoites. They also show that the immune response elicited in i.g. or i.p. infected BALB/c mice, although conferring some degree of protection, was not sufficient for complete parasite clearance.

Protection against LethalNeospora caninumInfection in Mice Induced by Heterologous Vaccination with amic1 mic3KnockoutToxoplasma gondiiStrain

“…Teixeira et al compared the immune response elicited by N. caninum after intraperitoneal or intragastric immunization and found very similar levels of IFN-␥ and Il-10 mRNA production, in agreement with our results (39). After intraperitoneal and intragastric immunization, both effector and T-regulatory CD4 ϩ CD25 ϩ cells were found to be expanded in the spleen of immunized mice (39). Accordingly, different regulatory cell types can be triggered in the site of immunological encounter in order to activate regulatory mechanisms that can account for the development of protective immunity in relation to the immunization route.…”

“…It is evident that the differential induction of immune mediators associated with the immunization route and with the parasite itself determines the development of protective immunity. Teixeira et al compared the immune response elicited by N. caninum after intraperitoneal or intragastric immunization and found very similar levels of IFN-␥ and Il-10 mRNA production, in agreement with our results (39). After intraperitoneal and intragastric immunization, both effector and T-regulatory CD4 ϩ CD25 ϩ cells were found to be expanded in the spleen of immunized mice (39).…”

“…Oral immunization with N. caninum tachyzoites has recently been shown to be a valuable system for the establishment of specific immune responses in immunocompetent mice. Oral immunization with tachyzoites appears to be very close to one of the natural routes of N. caninum infection but with a parasitic stage more easily obtained than the oocyst (39). The infectivity of T. gondii tachyzoites administered by the oral route was originally documented by Dubey et al, who successfully established infection with 1,000 extracellular tachyzoites (9).…”

Mucosal and systemic T cell response in mice intragastrically infected with Neospora caninum tachyzoites

“…Free parasitic forms of N. caninum were obtained as previously described [11] with slight modifications. Infected VERO cells were cultured until the host cell monolayer was 90% destroyed.…”

“…route using a previously described protocol [11]. Briefly, 5 h before infection mice were deprived of food.…”