Eradication ofCryptosporidium parvumInfection by Mice with Ovalbumin-Specific T Cells

Abstract

CD154 is necessary for mice to clear a Cryptosporidium parvum infection, but whether this ligand has to be expressed on T cells with specificity for C. parvum has not been determined. We infected DO11.10 (ovalbumin specific) T-cell receptor transgenic mice that had been bred to a RAG ؊/؊ background with C. parvum and found that the infection was cleared within 6 weeks, while RAG ؊/؊ controls were unable to clear C. parvum infection. Recovery was accompanied by an increase in the number of splenic T cells with the CD44 high phenotype that characterizes memory cells. To determine whether a C. parvum-infected environment sufficed to activate transgenic T cells, we reconstituted C. parvum-infected BALB/c SCID mice with DO11.10 RAG ؊/؊ splenocytes. Fecal excretion of C. parvum antigen ceased in the 12 weeks following the adoptive transfer, unless the mice were also injected with tolerizing doses of ovalbumin. DO11.10 T cells were found in the submucosa of C. parvum-infected, but not uninfected, BALB/c SCID hosts within 48 h of injection. The transferred DO11.10 T cells divided and acquired a CD44 high memory phenotype in C. parvum-infected, but not uninfected, recipients. DO11.10 splenocytes from CD154 knockout donors failed to clear a C. parvum infection, confirming a requirement for CD154 in recovery. In vitro, the DO11.10 cells did not proliferate in response to C. parvum antigen, and a tBlast GenBank search revealed no matches between the ovalbumin peptide and C. parvum DNA sequences. C. parvum-infected SCID mice given RAG ؊/؊ CD8 ؉ T cells with a Listeria-specific transgene did not recover from C. parvum infection. Our data suggest that antigen-nonspecific CD4 ؉ T-cell effector mechanisms in combination with the innate arm of the immune system are sufficient for the eradication of C. parvum infection.Cryptosporidium parvum causes severe diarrhea and weight loss in immunodeficient subjects, including those with AIDS (13) and boys with CD154 gene mutations causing X-linked immunodeficiency with hyper-immunoglobulin M (IgM) (17,20), but healthy adults have little if any symptomatology (9). T-cell-deficient mice fed C. parvum oocysts are infected first in the gut and some 6 weeks later in the intra-and extrahepatic biliary tree (29). Previous studies showed that C. parvum-infected SCID mice would clear the C. parvum infection if they were reconstituted with CD4 T cells (22,24) and that recovery was impaired by antibody to gamma interferon (IFN-␥) (7, 30), interleukin 4 (IL-4) (2), and IL-12 (31). Along with a requirement for major histocompatibility complex (MHC) class II expression (1), it seems likely that CD4 responses are central to recovery from C. parvum infection. Whether the CD4 response is contingent on stimulation of C. parvum-specific T cells by a C. parvum peptide on a class II molecule, or whether bystander T cells of other specificities might suffice to clear a C. parvum infection, is not known. Our own results indicate that a T-cell activation molecule, CD154, is necessary for C. parvum defense, becau...

Marrow-Derived CD40-Positive Cells Are Required for Mice To ClearCryptosporidium parvumInfection

“…It was previously shown that CD4 T cells expressing a transgene for an ovalbumin-specific antigen receptor sufficed to clear C. parvum infection from SCID mice, provided that the transgenic T cells became activated and were able to express CD154 (23). This result suggested that the clearance of C. parvum required an interaction between CD154 (presumably expressed on an activated T cell) and CD40.…”

“…Certainly CD8 T cells and MHC-I antigens do not seem to be required for cryptosporidia to be cleared (1,28). Even the CD4 T-cell response that can clear a C. parvum infection is unusual in that the specificity of the T-cell receptor seems less important than the activation of the T cells and their utilization of an intact CD154-CD40 signaling pathway (23). CD40 ligation can lead to apoptosis of fibroblasts (20) and, in vitro, of C. parvuminfected cells (17,30), so the direct triggering of apoptosis in CD40 ϩ infected cells by CD154 expressed on activated T cells was considered a potential mechanism that could account for the contribution of CD40 to C. parvum immunity.…”

“…1372) through the AIDS Research and Reference Reagent Program of the National Institute of Allergy and Infectious Diseases, National Institutes of Health (Bethesda, Md. ), as previously described (23). Over 50% of these oocysts excyst after being washed in bleach and incubated for 4 h at 37°C.…”

“…It was previously shown that T cells enter the laminae propriae of C. parvum-infected SCID mice prior to clearing of the infection (23). To determine whether CD40 was required for T cells to reach the lamina propria, we examined the guts of the CD40 Ϫ/Ϫ and wild-type C. parvum-infected recipients of the CFSE-labeled cells described above.…”

Cooperative Role of Macrophages and Neutrophils in Host Antiprotozoan Resistance in Mice Acutely Infected withCryptosporidium parvum

“…A variety of animal models have been used to study the nature and role of host immune responses to C. parvum infection, including neonatal mice (22), dexamethasonetreated mice (54), congenital immunodeficient (nude, RAG Ϫ/Ϫ , SCID) mice (1,28,33), and mice with targeted gene mutations for major histocompatibility complex class II, CD40, IFN-␥ or T-cell receptor ␣ (2, 19, 22, 50). From the studies performed with these models, the central importance of CD4 ϩ T cells (chronic) and IFN-␥ (acute and chronic) in the resistance to and recovery of animals from C. parvum infection have been proven.…”