Cryptosporidium parvum infection of human intestinal xenografts in SCID mice induces production of human tumor necrosis factor alpha and interleukin-8

Abstract

The protozoan parasite Cryptosporidium parvum invades intestinal epithelial cells and can cause life-threatening diarrhea in immunocompromised individuals. Despite the clinical importance of this organism, much remains to be learned about the pathogenesis of C. parvum-induced diarrhea. To explore the role of the intestinal inflammatory response in C. parvum disease, using C. parvum oocysts we infected human intestinal xenografts in severe combined immunodeficient (SCID) mice. Seven days after infection, we found levels of human tumor necrosis factor alpha and interleukin-8 in C. parvum-infected human intestinal xenografts that were significantly higher than those seen in uninfected control xenografts. These results demonstrate that human intestinal cells produce proinflammatory cytokines in response to C. parvum infection and establish SCID-HU-INT mice as a model system to study the interactions of C. parvum with the human intestine.

FIG. 1

C. parvum infects human intestinal xenografts. These photomicrographs from sections from two different C. parvum-infected intestinal xenografts 7 days following infection show C. parvum parasites (arrowheads) present in crypt cells (A) and in crypt and villous cells (B). Magnification, ×290.

FIG. 2

mRNA transcripts for human IL-1β, IL-8, and human TNF-α are induced when human intestinal xenografts are infected with C. parvum. The results of an RT-PCR assay for mRNA transcripts for human IL-1β, IL-8, human TNF-α, and actin from tissue samples from an intestinal xenograft infected 7 days previously with C. parvum (lanes +) and the control uninfected contralateral graft (lanes −) are shown. Transcripts of the predicted sizes for human IL-1β (339 bp), IL-8 (281 bp), and human TNF-α (610 bp) are amplified in the C. parvum-infected graft but are not detectable in control xenografts. The equivalent density of the actin control suggests that equivalent quantities of cDNA were present in the samples. Lane φX contains the φX174RF/HaeIII DNA size standards.

FIG. 3

Human intestinal xenografts produce human TNF-α and IL-8 in response to C. parvum infection. (A) Seven days following infection, the mean level of human TNF-α in C. parvum-infected human intestinal xenografts (n = 8) is significantly higher (P < 0.002) than the level of human TNF-α in uninfected grafts (n = 8). (B) At the same time point, the mean level of IL-8 in C. parvum-infected human intestinal xenografts (n = 8) is significantly higher (P < 0.002) than the level of IL-8 in uninfected grafts (n = 8). Error bars, standard errors of the means.