Encephalitozoon intestinalis:Humoral Responses in Interferon-γ Receptor Knockout Mice Infected with a Microsporidium Pathogenic in AIDS Patients

El Fakhry, Y., Achbarou, A., Desportes-Livage, I., and Mazier, D. 1998.Encephalitozoon intestinalis: Humoral responses in interferon-γ receptor knockout mice infected with a microsporidium pathogenic in AIDS patients.Experimental Parasitology,89,113–121. IFN-γ receptor knockout mice and wild-type mice were infectedper oswithEncephalitozoon intestinalis. Both groups developed an infection that was chronic in the mutant mice whereas it was only transient in wild-type mice. The infection of mutant mice was characterized by the continual shedding of spores in feces, splenomegaly, the enlargement of the biliary tract, and the occurrence of numerous nodules in the liver and in the small intestine wall. The humoral response was studied by ELISA, IFA, and Western blotting. ELISA titers of anti-E. intestinalisantibodies of IgG, IgM, and IgA isotypes were higher in IFN-γ R0/0mice than in wild-type mice and they increased in time after infection. Levels of IgG2a were inferior to those of IgG1 in mutant mice in contrast to wild-type mice. High levels of parasite specific antibodies were accompanied by an increase in type 2 cytokines (IL-4 and IL-10) secretion in the duodenum of IFN-γ R0/0mice. TheE. intestinalisspore wall was recognized by IgM, IgG, and IgA from all infected mice whereas the extruded polar tube only reacted with IgG and IgA from IFN-γ R0/0mice after 45 days of the infection. IFN-γ R0/0mice IgG and IgA reacting with polar tube identified also a series of proteins which could be components of this structure. On the proteins recognized by all infected mice sera, two were first recognized by IgM at day 15 and then by IgG at day 30 in wild-type (WT) mice. The persistent reactivity of all proteins in mutant mice is consistent with the chronicity of the infection in these animals; in contrast, their resorption at day 30 in WT animals corroborates the transient character of the infection in these mice. The correlation between the evolution of the proteic pattern and the development of the infection provides evidence of the validity of this murine model to study human microsporidiosis. Indeed the reported results confirm the potential value of serological methods for diagnosingE. intestinalisinfection in immunocompetent and in immunocompromised human subjects, for elucidating the age pattern of the microsporidiosis and also for identifying risk groups.