Cryptosporidium parvum-Specific Mucosal Immune Response in C57BL/6 Neonatal and Gamma Interferon-Deficient Mice: Role of Tumor Necrosis Factor Alpha in Protection

Abstract

Both neonatal and C57BL/6 gamma interferon (IFN-␥) knockout (C57BL/6-GKO) mice are susceptible to Cryptosporidium parvum, but the course of infection is different. Neonatal mice are able to clear the parasite within 3 weeks, whereas C57BL/6-GKO mice, depending on age, die rapidly or remain chronically infected. The mechanism by which IFN-␥ leads to a protective immunity is yet poorly understood. In order to investigate the effect of IFN-␥ on other cytokines expressed in the intestinal mucosa during C. parvum infection, we studied cytokine mRNA expression in the neonates and GKO (neonatal and adult) mice by quantitative reverse transcription-PCR (RT-PCR) at 4 and 9 days after infection. IFN-␥ mRNA levels were quickly and strongly up-regulated in the mucosa of neonatal mice. In GKO mice, the Th1-type response was dramatically altered during the infection, whereas the mRNA expression levels of the Th2-type cytokines interleukin 4 (IL-4) and IL-10 were increased in both mouse models. In the absence of IFN-␥, the adult knockout mice up-regulated the mRNA levels of inflammatory cytokines, such as IL-1␤, IL-6, and granulocyte-macrophage colony-stimulating factor, in the mucosa, but not tumor necrosis factor alpha (TNF-␣), whereas all these cytokines were upregulated in the infected neonatal mice. Further experiments indicated that injections of TNF-␣ into GKO adult mice significantly reduced oocyst shedding. The results of the present study indicate that the resolution of infection is dependent on the expression of Th1-type cytokines in the mucosa of C57BL/6 mice and that TNF-␣ may participate in the control of parasite development.Cryptosporidium parvum is an obligate intracellular protozoan parasite that infects intestinal epithelial cells of humans and various other mammals. C. parvum causes protracted diarrhea in young and immunodeficient individuals and can lead to death for AIDS patients. Cryptosporidiosis is frequent in young farm animals and has economic and environmental consequences. In immunocompetent hosts, the disease is self-limited, suggesting a major role for host defense factors in controlling the infection.Most of the studies of experimental cryptosporidiosis have been performed with rodents whose immune systems were impaired, e.g., neonatal mice (14,25,35), rats immunosuppressed with dexamethasone (27), or congenitally mutated nude (21, 23) and SCID mice (17,34). More recent studies have used mice with targeted mutations for the genes of major histocompatibility complex class II (1), CD40, CD40L (7), or gamma interferon (IFN-␥) (33, 38). The key role of IFN-␥ in resistance to C. parvum infection initially demonstrated with antibody depletion was confirmed more recently with IFN-␥ knockout mice (GKO) (6,33,34). However, the mechanisms whereby IFN-␥ intervenes in the clearance of C. parvum are still not well understood. Some possibilities, not mutually exclusive, include a direct toxic effect of IFN-␥ on the parasite or the infected cells or the induction of other cytokines that can be toxic for the pa...

MyD88-Dependent Pathways Mediate Resistance toCryptosporidium parvumInfection in Mice

“…However, C. parvum infection of IFN-␥-neutralized MyD88 Ϫ/Ϫ mice resulted in severe enterocolitis, which most likely contributed to mortality in many of these mice. Our study confirms previous findings of intestinal inflammation in C. parvum-infected IFN-␥-deficient mice (22,39). MyD88-dependent pathways have also recently been shown to play a critical role in intestinal homeostasis and resistance to epithelial injury and inflammation (33).…”

Identification and Immunological Characterization of Three Potential Vaccinogens against Cryptosporidium Species

“…Significantly, IFN-␥, a critical cytokine associated with a protective Th1 memory response and protection against Cryptosporidium infection (20), was produced by spleen cells from animals immunized with each of the selected antigens after restimulation with their corresponding protein. Interestingly, profilin induced extremely high levels of IFN-␥, similar to the levels induced by ConA.…”

Infectivity of Cryptosporidium hominis and Cryptosporidium parvum Genotype 2 Isolates in Immunosuppressed Mongolian Gerbils

“…In immunocompromised adult and suckling rodents, doses ranged usually from 10 4 to 10 7 oocysts/animal, and some isolates were found to be infective at doses as low as 25 oocysts/animal or close to the "one-oocyst level" (4,5,10,15,17,19,21,26,35,39). The sensitivity of 100 oocysts/animal reached in the present model was included within the 1-to 1,000-oocyst range that was considered infective in immunocompetent humans from direct and indirect evidence (7,11,25).…”