Localization of alpha/beta and gamma/delta T lymphocytes in Cryptosporidium parvum-infected tissues in naive and immune calves

Immunophenotyping of peripheral circulating lymphocytes and serum selenium levels in calves with neonatal diarrhea

This work aims to: (1) elucidate the immune response exhibited by CD4 + and CD8 + T lymphocyte cells in response to various infectious agents in calves suffering with neonatal diarrhea; and (2) determine and investigate the association between serum selenium levels and T lymphocyte subtypes in neonatal calves afflicted with neonatal diarrhea and infected with various infectious agents. The study encompassed a cohort of 50 calves, encompassing both sexes and various breeds, within the neonatal age range (1-28 days old). Subdivided into distinct groups, the calves were categorized based on the causative agents of neonatal diarrhea, including Rotavirus (n = 10), Cryptosporidium parvum (C.parvum) (n = 10), Coronavirus (n = 5), Rotavirus+C.parvum (n = 5), and a Control group (n = 20). Blood samples were meticulously obtained from the vena jugularis of all animals utilizing specific techniques-8 ml in tubes devoid of anticoagulant and 3 ml in blood collection tubes containing EDTA. Serum selenium levels were analyzed by ICP-MS. Flow Cytometry device was used to determine CD4 + and CD8 +T lymphocyte levels. In this study, although there was no statistically significant difference in serum selenium levels between all study groups, it was found that the selenium level in the control group was not sufficient. CD4 T lymphocyte levels, the rotavirus+C.parvum group exhibited a statistically significant elevation compared to the coronavirus group. Regarding CD8 + T lymphocyte levels, the coronavirus group demonstrated a statistically significant increase when compared to the control group. In intragroup analyses of CD8 + T lymphocyte levels, the coronavirus group exhibited a significant elevation compared to the rotavirus group, C.parvum group, and the C.parvum + Rotavirus group. A significant negative correlation was detected between selenium levels and CD4 + T lymphocytes, while no correlation was found between CD8 + T lymphocytes. Fibrinogen concentration exhibited statistical significance, being higher in the Rotavirus group (p < 0.008) compared to the control group, in the C.parvum group (p < 0.004) compared to the control group, and in the Coronavirus group (p < 0.001) compared to the control group. The leukocyte count demonstrated statistical significance, being higher in the Rotavirus group compared to the control group (p < 0.001), in the Rotavirus+C.parvum group compared to the control group (p < 0.002), and in the Coronavirus group compared to the control group (p < 0.011). In conclusion, the data derived from this study illuminate discernible disparities in CD4 + and CD8 + T lymphocyte immune responses, contingent upon the specific etiological agent associated with neonatal diarrhea. Furthermore, the study underscores the importance of considering selenium deficiency as a relevant factor in calves affected by neonatal diarrhea.

Cryptosporidium parvum infection alters the intestinal mucosa transcriptome in neonatal calves: implications for immune function

One of the leading causes of infectious diarrhea in newborn calves is the apicomplexan protozoan Cryptosporidium parvum (C. parvum). However, little is known about its immunopathogenesis. Using next generation sequencing, this study investigated the immune transcriptional response to C. parvum infection in neonatal calves. Neonatal male Holstein-Friesian calves were either orally infected (N = 5) or not (CTRL group, N = 5) with C. parvum oocysts (gp60 subtype IIaA15G2R1) at day 1 of life and slaughtered on day 7 after infection. Total RNA was extracted from the jejunal mucosa for short read. Differentially expressed genes (DEGs) between infected and CTRL groups were assessed using DESeq2 at a false discovery rate < 0.05. Infection did not affect plasma immunohematological parameters, including neutrophil, lymphocyte, monocyte, leucocyte, thrombocyte, and erythrocyte counts as well as hematocrit and hemoglobin concentration on day 7 post infection. The immune-related DEGs were selected according to the UniProt immune system process database and were used for gene ontology (GO) and pathway enrichment analysis using Cytoscape (v3.9.1). Based on GO analysis, DEGs annotated to mucosal immunity, recognizing and presenting antigens, chemotaxis of neutrophils, eosinophils, natural killer cells, B and T cells mediated by signaling pathways including toll like receptors, interleukins, tumor necrosis factor, T cell receptor, and NF-KB were upregulated, while markers of macrophages chemotaxis and cytosolic pattern recognition were downregulated. This study provides a holistic snapshot of immune-related pathways induced by C. parvum in calves, including novel and detailed feedback and feedforward regulatory mechanisms establishing the crosstalk between innate and adaptive immune response in neonate calves, which could be utilized further to develop new therapeutic strategies.

Characterization of Bovine Intraepithelial T Lymphocytes in the Gut

Intraepithelial T lymphocytes (T-IELs), which constitute over 50% of the total T lymphocytes in the animal, patrol the mucosal epithelial lining to defend against pathogen invasion while maintaining gut homeostasis. In addition to expressing T cell markers such as CD4 and CD8, T-IELs display T cell receptors (TCR), including either TCRαβ or TCRγδ. Both humans and mice share similar T-IEL subsets: TCRγδ+, TCRαβ+CD8αα+, TCRαβ+CD4+, and TCRαβ+CD8αβ+. Among these subsets, human T-IELs are predominantly TCRαβ+ (over 80%), whereas those in mice are mostly TCRγδ+ (~60%). Of note, the majority of the TCRγδ+ subset expresses CD8αα in both species. Although T-IELs have been extensively studied in humans and mice, their profiles in cattle have not been well examined. Our study is the first to characterize bovine T-IELs using flow cytometry, where we identified several distinct features. The percentage of TCRγδ+ was comparable to that of TCRαβ+ T-IELs (both ~50% of CD3+), and the majority of bovine TCRγδ+ T-IELs did not express CD8 (CD8-) (above 60%). Furthermore, about 20% of TCRαβ+ T-IELs were CD4+CD8αβ+, and the remaining TCRαβ+ T-IELs were evenly distributed between CD4+ and CD8αβ+ (~40% of TCRαβ+ T-IELs each) with no TCRαβ+CD8αα+ identified. Despite these unique properties, bovine T-IELs, similar to those in humans and mice, expressed a high level of CD69, an activation and tissue-retention marker, and a low level of CD62L, a lymphoid adhesion marker. Moreover, bovine T-IELs produced low levels of inflammatory cytokines such as IFNγ and IL17A, and secreted small amounts of the immune regulatory cytokine TGFβ1. Hence, bovine T-IELs' composition largely differs from that of human and mouse, with the dominance of the CD8- population among TCRγδ+ T-IELs, the substantial presence of TCRαβ+CD4+CD8αβ+ cells, and the absence of TCRαβ+CD8αα+ T-IELs. These results provide the groundwork for conducting future studies to examine how bovine T-IELs respond to intestinal pathogens and maintain the integrity of the gut epithelial barrier in animals.

Structural Analyses of a Dominant Cryptosporidium parvum Epitope Presented by H-2Kb Offer New Options To Combat Cryptosporidiosis

Cryptosporidium parvum has gained much attention as a major cause of diarrhea in the world, particularly in those with compromised immune systems. The data currently available on how the immune system recognizes C. parvum are growing rapidly, but we lack data on the interactions among host major histocompatibility complex (MHC) diversity and parasitic T-cell epitopes. To identify antigenic epitopes in a murine model, we performed systematic profiling of H-2K^b-restricted peptides by screening the dominant Cryptosporidium antigens. The results revealed that the glycoprotein-derived epitope Gp40/15-SVF9 induced an immunodominant response in C. parvum-recovered C57BL/6 mice, and injection of the cytotoxic-T-lymphocyte (CTL) peptide with the adjuvant activated peptide-specific CD8⁺ T cells. Notably, the SVF9 epitope was highly conserved across Cryptosporidium hominis, C. parvum, and many other Cryptosporidium species. SVF9 also formed stable peptide-MHC class I (MHC I) complexes with HLA-A*0201, suggesting cross-reactivity between H-2K^b and human MHC I specificities. Crystal structure analyses revealed that the interactions of peptide-MHC surface residues of H-2K^b and HLA-A*0201 are highly conserved. The hydrogen bonds of H-2K^b-SVF9 are similar to those of a dominant epitope presented by HLA-A*0201, which can be recognized by a public human T-cell receptor (TCR). Notably, we found double conformations in position 4 (P4), 5 (P5) of the SVF9 peptide, which showed high flexibility, and multiple peptide conformations generated more molecular surfaces that can potentially be recognized by TCRs. Our findings demonstrate that an immunodominant C. parvum epitope and its homologs from different Cryptosporidium species and subtypes can benefit vaccine development to combat cryptosporidiosis. IMPORTANCE Adaptive immune responses and T lymphocytes have been implicated as important mechanisms of parasite-induced protection. However, the role of CD8⁺ T lymphocytes in the resolution of C. parvum infection is largely unresolved. Our results revealed that the glycoprotein-derived epitope Gp40/15-SVF9 induced an immunodominant CD8⁺ T-cell response in C57BL/6 mice. Crystal structure analyses revealed that the interactions of the H-2K^b-SVF9 peptide are similar to those of a dominant epitope presented by HLA-A*0201, which can be recognized by human TCRs. In addition, we found double conformations of the SVF9 peptide, which showed high flexibility and multiple peptide conformations that can potentially be recognized by TCRs.

Antiparasitic and immunomodulating effects of nitazoxanide, ivermectin and selenium on Cryptosporidium infection in diabetic mice

The present work aims to investigate the antiparasitic and the immunomodulating effects of nitazoxanide (NTZ) and ivermectin (IVC) alone or combined together or combined with selenium (Se), on Cryptosporidium infection in diabetic mice. The results revealed that the combined NTZ and IVC therapy achieved the highest reduction of fecal oocysts (92%), whereas single NTZ showed the lowest reduction (63%). Also, adding Se to either NTZ or IVC resulted in elevation of oocyst reduction from 63% to 71% and from 82% to 84% respectively. All treatment regimens, with the exception of NTZ monotherapy, showed a significant improvement in the intestinal histopathology, the highest score was in combined NTZ and IVC therapy. The unique results of immunohistochemistry in this study showed reversal of the normal CD4/CD8 T cell ratio in the infected untreated mice, however, following therapy it reverts back to a normal balanced ratio. The combined (NTZ+ IVC) treatment demonstrated the highest level of CD4 T cell expression. Taken together, NTZ and IVC combined therapy showed remarkable anti-parasitic and immunostimulatory effects, specifically towards the CD4 population that seem to be promising in controlling cryptosporidiosis in diabetic individuals. Further research is required to explore other effective treatment strategies for those comorbid patients.

Molecular detection of Cryptosporidium: an emerging parasite in different water sources of 2010 flood-affected district Nowshera, Pakistan

Cryptosporidium is a water-borne zoonotic parasite worldwide, usually found in lakes and rivers contaminated with sewage and animal wastes, causing outbreaks of cryptosporidiosis. In this study, 300 water samples were collected from four designated places of flood-affected district Nowshera consist of different water sources to find out the prevalence of Cryptosporidium via polymerase chain reaction (PCR). The overall prevalence of Cryptosporidium was 30.33% (91/300) with more prevalent 44% in drain water and low 5% in bore/tube well water. The prevalence in open well and tap water was recorded 33% and 20%, respectively. The highest prevalence was recorded in summer (June-September). The result of this study ensures enormous contamination of drinking water that requires appropriate treatment, cleaning and filtration to provide safe drinking water. Preventing water-borne disease and proper treatment of water supplies is essential to public health.

Bovine cryptosporidiosis: impact, host-parasite interaction and control strategies

Gastrointestinal disease caused by the apicomplexan parasite Cryptosporidium parvum is one of the most important diseases of young ruminant livestock, particularly neonatal calves. Infected animals may suffer from profuse watery diarrhoea, dehydration and in severe cases death can occur. At present, effective therapeutic and preventative measures are not available and a better understanding of the host-pathogen interactions is required. Cryptosporidium parvum is also an important zoonotic pathogen causing severe disease in people, with young children being particularly vulnerable. Our knowledge of the immune responses induced by Cryptosporidium parasites in clinically relevant hosts is very limited. This review discusses the impact of bovine cryptosporidiosis and describes how a thorough understanding of the host-pathogen interactions may help to identify novel prevention and control strategies.

The early intestinal immune response in experimental neonatal ovine cryptosporidiosis is characterized by an increased frequency of perforin expressing NCR1(+) NK cells and by NCR1(-) CD8(+) cell recruitment

Cryptosporidium parvum, a zoonotic protozoan parasite, causes important losses in neonatal ruminants. Innate immunity plays a key role in controlling the acute phase of this infection. The participation of NCR1+ Natural Killer (NK) cells in the early intestinal innate immune response to the parasite was investigated in neonatal lambs inoculated at birth. The observed increase in the lymphocyte infiltration was further studied by immunohistology and flow cytometry with focus on distribution, density, cellular phenotype related to cytotoxic function and activation status. The frequency of NCR1+ cells did not change with infection, while their absolute number slightly increased in the jejunum and the CD8+/NCR1- T cell density increased markedly. The frequency of perforin+ cells increased significantly with infection in the NCR1+ population (in both NCR1+/CD16+ and NCR1+/CD16- populations) but not in the NCR1-/CD8+ population. The proportion of NCR1+ cells co-expressing CD16+ also increased. The fraction of cells expressing IL2 receptor (CD25), higher in the NCR1+/CD8+ population than among the CD8+/NCR1- cells in jejunal Peyer’s patches, remained unchanged during infection. However, contrary to CD8+/NCR1- lymphocytes, the intensity of CD25 expressed by NCR1+ lymphocytes increased in infected lambs. Altogether, the data demonstrating that NK cells are highly activated and possess a high cytotoxic potential very early during infection, concomitant with an up-regulation of the interferon gamma gene in the gut segments, support the hypothesis that they are involved in the innate immune response against C. parvum. The early significant recruitment of CD8+/NCR1- T cells in the small intestine suggests that they could rapidly drive the establishment of the acquired immune response.

Cryptosporidiosis: host immune responses and the prospects for effective immunotherapies

Cryptosporidium spp. that develop in intestinal epithelial cells are responsible for the diarrhoeal disease cryptosporidiosis, which is common in humans of all ages and in neonatal livestock. Following infection, parasite reproduction increases for a number of days before it is blunted and then impeded by innate and adaptive immune responses. Immunocompromised hosts often cannot establish strong immunity and develop chronic infections that can lead to death. Few drugs consistently inhibit parasite reproduction in the host, and chemotherapy might be ineffective in immunodeficient hosts. Future options for prevention or treatment of cryptosporidiosis might include vaccines or recombinant immunological molecules, but this will probably require a better understanding of both the mucosal immune system and intestinal immune responses to the parasite.

Activated CD8+ T cells contribute to clearance of gastric Cryptosporidium muris infections

The role of CD4+ and CD8+ T lymphocytes in the development of a protective immune response against Cryptosporidium muris infection was studied by the reconstitution of severe combined immunodeficient (SCID) mice with well-defined populations of either naive or immune CD8+ or CD4+ T lymphocytes. Adoptive transfer of both naive and immune CD4+ T lymphocyte subpopulations protects SCID mice against cryptosporidiosis. Moreover, a significant biological impact of activated CD8+ T cells against gastric cryptosporidiosis was observed. The significant difference in the course and intensity of the infection in reconstituted SCID mice was found to be dependent on the protective function of both the CD4+ and CD8+ T-cell populations transferred. While SCID mice reconstituted with either immune or naive CD4+ or immune CD8+ T-cell subpopulations resolved the infection within 29, 37 and 51 days post-infection, respectively, those reconstituted with naive CD8+ T cells suffered from chronic infection similar to control SCID mice. Reconstitution with CD4+ T cells resulted in suppression of oocyst excretion and shortening of patent period in comparison with SCID mice reconstituted with CD8+ T cells. Thus, although CD4+ T cells are considered important in protective immunity, our results are the first to demonstrate the involvement of activated CD8+ T lymphocytes in the protection of mice against gastric cryptosporidiosis.

Host immune response to Cryptosporidium parvum infection

Species of the genus Cryptosporidium are protozoan parasites (Apicomplexa) that cause gastroenteritis in animals and humans. Of these Cryptosporidium parvum and Cryptosporidium hominis are the major causative agents of human cryptosporidiosis. Whereas infection is self-limiting in the immunocompetent hosts, immunocompromised individuals develop a chronic, life-threatening disease. As specific therapeutic or preventive interventions are not yet available, better understanding of the immune response to the parasite is required. This minireview briefly summarizes the factors involved in the innate and acquired immune response in this pathogen-host interaction with an emphasis on more recent data from mouse models of infection.

Expression and regulation of IL-22 by bovine peripheral blood gamma/delta T cells

IL-22 is a novel T and NK cell cytokine that belongs to the IL-10 cytokine family. Here we report the identification of a bovine IL-22 ortholog that is expressed by mitogen activated bovine peripheral blood gamma/delta T cells. The full-length bovine IL-22 cDNA contained a 68 bp 5'-untranslated region (UTR), a 570-bp open reading frame, and a 480-bp 3'-UTR. The deduced pre-IL-22 has 190 amino acid residues containing a secretory signal peptide from amino acids 1-33 and several potential N-glycosylation sites. The mature protein is predicted to be a secreted, alpha-helical molecule. The bovine IL-22 gene is approximately 7.5 kb in length and is comprised of five introns and six exons, and the first exon is non-coding. Computer analysis and gel shift assay showed that the -1132 and -879 region in the 5' upstream gene sequence contained putative transcription factor binding sites for STATx, Sox-5/9, Sp1, Ik-1, and AREB6. Mutagenesis of STATx and Sox5/9 binding sites decreased promoter functionality by approximately 50%, suggesting their importance in transcription regulation of IL-22. Expression of IL-22 transcripts induced by various mitogens indicated existence of two regulatory control pathways in gamma/delta T cells; IL-2 or PMA treatment induced a slow accumulation of IL-22 mRNA without affecting the maximum induction pathway, whereas ConA treatment rapidly induced a limited amount of IL-22 transcripts. Similar maximal levels of IL-22 transcripts could be induced in gamma/delta T cells and alpha/beta T cells. We conclude that bovine gamma/delta T cells are important sources of IL-22 and suggest a role for this cytokine in regulating immune responses at mucosal surfaces, including the gut.

Biphasic modulation of apoptotic pathways in Cryptosporidium parvum-infected human intestinal epithelial cells

The impact of Cryptosporidium parvum infection on host cell gene expression was investigated by microarray analysis with an in vitro model using human ileocecal HCT-8 adenocarcinoma cells. We found changes in 333 (2.6%) transcripts at at least two of the five (6, 12, 24, 48, and 72 h) postinfection time points. Fifty-one of the regulated genes were associated with apoptosis and were grouped into five clusters based on their expression patterns. Early in infection (6 and 12 h), genes with antiapoptotic roles were upregulated and genes with apoptotic roles were downregulated. Later in infection (24, 48, and 72 h), proapoptotic genes were induced and antiapoptotic genes were downregulated, suggesting a biphasic regulation of apoptosis: antiapoptotic state early and moderately proapoptotic state late in infection. This transcriptional profile matched the actual occurrence of apoptosis in the infected cultures. Apoptosis was first detected at 12 h postinfection and increased to a plateau at 24 h, when 20% of infected cells showed nuclear condensation. In contrast, experimental silencing of Bcl-2 induced apoptosis in 50% of infected cells at 12 h postinfection. This resulted in a decrease in the infection rate and a reduction in the accumulation of meront-containing cells. To test the significance of the moderately proapoptotic state late in the infection, we inhibited apoptosis using pancaspase inhibitor Z-VAD-FMK. This treatment also affected the progression of C. parvum infection, as reinfection, normally seen late (24 h to 48 h), did not occur and accumulation of mature meronts was impaired. Control of host apoptosis is complex and crucial to the life of C. parvum. Apoptosis control has at least two components, early inhibition and late moderate promotion. For a successful infection, both aspects appear to be required.

Detection of epithelial-cell injury, and quantification of infection, in the HCT-8 organoid model of cryptosporidiosis

BACKGROUND

Intestinal cells grown in microgravity produce a three-dimensional tissue assembly, or "organoid," similar to the human intestinal mucosa, making it an ideal model for enteric infections such as cryptosporidiosis.

METHODS

HCT-8 cells were grown in a reduced-gravity, low-shear, rotating-wall vessel (RWV) and were infected with Cryptosporidium parvum oocysts. Routine and electron microscopy (EM), immunolabeling with fluorescein-labeled Vicia villosa lectin and phycoerythrin-labeled monoclonal antibody to a 15-kD surface-membrane protein, and quantitative polymerase chain reaction (qPCR) using probes for 18s rRNA of C. parvum and HCT-8 cells were performed.

RESULTS

The RWV allowed development of columnar epithelium-like structures. Higher magnification revealed well-developed brush borders at the apical side of the tissue. Incubation with C. parvum resulted in patchy disruption of the epithelium and, at the surface of several epithelial cells, in localized infection with the organism. EM revealed irregular stunting of microvilli, foci of indistinct tight junctions, and areas of loose paracellular spaces. qPCR showed a 1.85-log (i.e., 70-fold) progression of infection from 6 h to 48 h of incubation.

CONCLUSION

The HCT-8 organoid displayed morphologic changes indicative of successful and quantifiable infection with C. parvum. The HCT-8 organoid-culture system may have application in interventional in vitro studies of cryptosporidiosis.

Role of murine Peyer's patch lymphocytes against primary and challenge infections with Cryptosporidium parvum

In order to determine the role of Peyeros patch lymphocytes (PPL) in self-clearing of Cryptosporidium parvum infection in murine models, changes in PPL subsets, their cytokine expression, and in vitro IgG1 and IgA secretions by PPL were observed in primary- and challenge-infected C57BL/6 mice. In primary-infected mice, the percentages of CD4+ T cells, CD8+ T cells, sIgA+ B cells, IL-2+ T cells, and IFN-gamma+ T cells among the PPL, increased significantly (P < 0.05) on day 10 post-infection (PI). Secretion of IgG1 and IgA in vitro by PPL also increased on day 10 PI. However, all these responses, with the exception of IgG1 and IgA secretions, decreased in challenge-infected mice on day 7 post-challenge (= day 13 PI); their IgG1 and IgA levels were higher (P > 0.05) than those in primaryinfected mice. The results suggest that murine PPL play an important role in self-clearing of primary C. parvum infections through proliferation of CD4+, CD8+, IL-2+, and IFN-gamma+ T cells, and IgG1 and IgA-secreting B cells. In challenge infections, the role of T cells is reduced whereas that of B cells secreting IgA appeared to be continuously important.

The immunology of parasite infections in immunocompromised hosts

Immune compromise can modify the severity and manifestation of some parasitic infections. More widespread use of newer immnosuppressive therapies, the growing population of individuals with immunocompromised states as well as the prolonged survival of these patients have altered the pattern of parasitic infection. This review article discusses the burden and immunology of parasitic infections in patients who are immunocompromised secondary to congenital immunodeficiency, malnutrition, malignancy, and immunosuppressive medications. This review does not address the literature on parasitic infections in the setting of HIV-1 infection.

An early intestinal mucosal source of gamma interferon is associated with resistance to and control of Cryptosporidium parvum infection in mice

Resistance to and control of Cryptosporidium parvum infection in mice in the absence of adaptive immunity appears to be gamma interferon (IFN-gamma) dependent. Using an IFN-gamma-neutralizing antibody in a murine model, we demonstrated increased susceptibility to infection within 24 h. We correlated this early resistance and control with increased mucosal expression of IFN-gamma and demonstrate that CD8+ T-cell receptor alphabeta intestinal intraepithelial lymphocytes express and secrete this cytokine shortly after infection. The rapid kinetics of IFN-gamma expression and secretion by naive CD8+ T cells in response to a protozoan pathogen have not previously been demonstrated.

Kinetics and distribution of bovine gammadelta T-lymphocyte in the intestine: gammadelta T cells accumulate in the dome region of Peyer's patch during prenatal development

The kinetics and distribution of gammadelta T cells in bovine intestine including jejunal and ileal Peyer's patch were examined. The number of gammadelta T cells increased significantly in the dome region during prenatal development, but decreased notably after birth. The number of some gammadelta T cells, CD4+ cells, and CD8+ cells in the intestinal villi remained constant during prenatal development, but increased significantly after birth. The kinetics of the gammadelta T cells in the dome region during prenatal development were quite distinct from those of the gammadelta T cells, CD4+ cells, and CD8+ cells in the intestinal villi. In the fetal ileum at full-term gestation, the frequencies of expression of the T-cell receptor gamma variable region (TCR Vgamma) family were TCR Vgamma1 (48%), Vgamma2 (4%), and Vgamma5 (48%). However, in 2-month-old calf ileum, TCR Vgamma5 (90%) was dominant. We speculate that functional differences exist between gammadelta T cells in the dome region during prenatal development and in the intestinal villi after birth.

Cryptosporidium parvum regulation of human epithelial cell gene expression

Cryptosporidium parvum is an obligate intracellular protozoan capable of causing life-threatening diarrhoeal disease in immunocompromised individuals. Efforts to develop novel therapeutic strategies have been hampered by the lack of understanding of the pathogenesis of infection. To better understand the host response to C. parvum infection, gene expression profiles of infected human ileocecal adenocarcinoma cells were analysed by using Affymetrix oligonucleotide microarrays containing probe sets for 12,600 human genes. Statistical analysis of expression data from three independent experiments identified 223 genes whose expression was reproducibly regulated by C. parvum infection at 24 h post-inoculation (125 up-regulated and 98 down-regulated), 13 of which were validated by quantitative reverse transcriptase polymerase chain reaction analysis. This analysis revealed the consistent up-regulation of host heat-shock genes and genes for pro-inflammatory chemokines IL-8, RANTES, and SCYB5. Multiple genes for host actin and tubulin genes were up-regulated whereas genes for actin binding proteins were down-regulated, confirming previous observations of host cytoskeleton rearrangement in response to C. parvum infection. In addition, host genes associated with cell proliferation and apoptosis were differentially regulated, reflecting the complexity of host-parasite interaction. Together, this study demonstrated that C. parvum infection results in significant changes in host biochemical pathways and provides new insights into specific biological processes of infectious disease caused by an intracellular protozoan parasite.

Kinetics of spleen and Peyer's patch lymphocyte populations during gut parasite clearing in Cryptosporidium parvum infected suckling mice

Data from experimental and human cryptosporidiosis have established a major role of specific immunity in the control of Cryptosporidium parvum infection. In this work, alterations in spleen and Peyer's patch (Pp) lymphocytes were investigated in the course of a spontaneously resolutive gut cryptosporidiosis in four-day-old suckling NMRI mice infected with either 4 x 10(5) or 30 viable oocysts. Oocysts from entire small intestines, and spleen and Pp lymphocytes were examined using flow cytometry from day 7 to day 27 post-infection. Compared to uninfected animals, a 3-5 fold increase in the numbers of spleen TCR alphabeta+, CD4+, CD8+, TCR gammadelta+ and CD45R/B220+ lymphocytes was observed on day 17 post-infection in heavily infected animals. In Pp, more than ten-fold increases were observed, except for TCR gammadelta+ lymphocytes. At termination of infection, i.e. on days 21-23 after ingestion of 4 x 105 oocysts, T and B lymphocytes decreased rapidly in both organs, and remained lower than in uninfected animals on days 19-23 post-infection. In mice infected with 30 oocysts, similar alterations were observed in Pp, but not in spleen. Data suggest that in normally developing mice, clearance of gut C. parvum infection is associated with an initial increase in systemic and local lymphocyte numbers, followed by their decrease to below control levels during the recovery phase.

Cryptosporidium and host resistance: historical perspective and some novel approaches

Cryptosporidium parvum is recognized as a major cause of diarrheal disease in neonatal bovine calves. In addition, this protozoan parasite has emerged as an important cause of disease in both immunocompromised and immunocompetent humans. Despite years of research, no consistently effective means of prevention or treatment are readily available for cryptosporidiosis in any species. Infection through ingestion of contaminated water has been widely documented; C. parvum was reported to be responsible for the largest waterborne outbreak of infectious disease in US history. In addition to its role as a primary disease agent, C. parvum has potential to initiate or exacerbate other gastrointestinal disorders, such as inflammatory bowel disease. Thus, control of C. parvum infection in both animals and humans remains an important objective. Research in our laboratory has focused on understanding mechanisms of resistance to C. parvum. We have demonstrated that acquisition of intestinal flora increases resistance to C. parvum. Substances present in the intestinal mucosa of adult animals can transfer resistance when fed to susceptible infants. Both expression of intestinal enzymes and rate of proliferation of epithelial cells may be altered following C. parvum infection. These and other changes may have profound effects on host resistance to C. parvum.

Role of murine intestinal intraepithelial lymphocytes and lamina propria lymphocytes against primary and challenge infections with Cryptosporidium parvum

To investigate the role of intestinal lamina propria lymphocytes (LPL) and intraepithelial lymphocytes (IEL) in controlling Cryptosporidium parvum infection, changes in their phenotypes and functional properties were studied after induction of primary and challenge infections in immunocompetent mice. As shown by oocyst-shedding patterns, the challenge-infected group recovered more rapidly from infection than did the primary-infected group. In LPL, proportions of activated CD4+, CD25+, IgG1+, IgA+, and CD4+/IFN-gamma+ cells increased significantly in the primary-infected group compared with controls. In the challenge-infected group, proportions of these cells decreased. The antigen-specific IgA level was elevated significantly among LPL of both primary- and challenge-infected groups. Among IEL, proportions of activated CD8+, T cell receptor (TCR) gammadelta+, and CD8+/TCR gammadelta+ cells increased significantly in the challenge-infected group compared with controls and the primary-infected group; their cytotoxicity also was enhanced. However, the proportion of IEL expressing Th1 cytokines was lower than that among LPL in both infected groups. The results suggest that LPL play a more important role in protection against a primary infection with C. parvum, through the production of IFN-gamma and IgA, whereas IEL are more involved in protection against a challenge infection, through enhanced cytotoxicity.

Recent advances in cryptosporidiosis: the immune response

An increased understanding of host immune responses to Cryptosporidium parvum which are responsible for clearance of primary infection and resistance to reinfection, and characterization of the parasite molecules to which they are directed, are essential for discovery of effective active and passive immunization strategies against cryptosporidiosis. In this article, recent advances in knowledge of humoral and cellular immune responses to C. parvum, their antigen specificities, and mechanisms of protection are briefly reviewed.

Association of IL-10 expression by mucosal lymphocytes with increased expression of Cryptosporidium parvum epitopes in infected epithelium

The objective of this study was to determine whether changes in the ileal intraepithelial lymphocyte (TEL) phenotype and function occurred prior to development of diarrhea in Cryptosporidium parvum-infected calves. Calves were orally inoculated with 10(8) oocysts and maintained in enteric pathogen-free conditions until their use in experiments. Age-matched uninfected calves were used for comparisons. Ileal IELs were isolated and phenotyped to determine whether changes in lymphocyte population dynamics had occurred by 3 days postinoculation (PI). Ex vivo reverse transcriptase-polymerase chain reaction of messenger ribonucleic acid (mRNA) from IELs from infected calves was compared with controls to determine whether changes in cytokine expression had occurred by 3 days PI. No significant changes in lymphocyte population dynamics were documented, however, IELs isolated from 4 out of 8 infected calves, but not from 8 out of 8 control calves, expressed mRNA for interleukin-10 (IL-10). IL-10 expression by IELs was associated with the expression of a significantly larger (P < 0.001) proportion (0.75) of monoclonal antibody-defined C. parvum epitopes within infected ileal epithelium, as compared with a much smaller proportion (0.30) of epitopes with IL-10 lymphocytes. The results suggest that a temporal association exists between the expression of IL-10 by ileal IELs and the expression of C. parvum antigens in infected calf epithelium prior to development of cryptosporidiosis.

Evidence for the emergence of a type-1-like immune response in intestinal mucosa of calves recovering from cryptosporidiosis

This study was undertaken to characterize the mucosal response to Cryptosporidium parvum in infected calves that had recovered from diarrhea. Flow cytometric surface phenotypes of lamina propria lymphocyte (LPL) suspensions from infected calves and age-matched controls revealed the presence of a significantly larger proportion of CD25+ LPL in infected calves than in controls. Freshly isolated LPL from infected calves expressed more iNOS and interferon (IFN)-gamma than did controls. Infected calves excreted IgG1 and IgG2 isotype antibodies to C. parvum p23 by the end of the experiment. Moreover, immunohistochemistry of ileal sections revealed the presence of IgG1+ and IgG2+ B lymphocytes in the villi and IgG1+ but not IgG2+ B lymphocytes in continuous Peyer's patch nodules. These data are consistent with the emergence of a type-1-like mucosal immune response in terminal ileal mucosa as calves recover from cryptosporidiosis.

Host cell-mediated responses to infection with Cryptosporidium

The coccidian Cryptosporidium infects epithelial cells of a variety of vertebrate hosts and is the causative agent of cryptosporidiosis. In mammals, including humans and domestic animals, C. parvum infects the gastrointestinal tract producing an acute watery diarrhoea and weight loss. CD4+ T-cell-deficient hosts have increased susceptibility to infection with the parasite and may develop severe life-threatening complications. The host responses which induce protective immunity and contribute to pathogenesis are poorly understood. In the immunological control of infection, recent studies with murine infection models suggest that IFN-gamma plays a key role in a partially protective innate immunity against infection identified in immunocompromised mice and also in the elimination of infection mediated by CD4+ T-cells. At the mucosal level, CD4+ intraepithelial lymphocytes are involved in the control of cryptosporidial infection, acting at least in part through production of IFN-gamma which has a direct inhibitory effect on parasite development in enterocytes. Primary infection of ruminants induces an intestinal inflammatory response in which increased numbers of various T-cell subpopulations appear in the villi. In addition, infection results in increased intestinal expression of pro-inflammatory cytokines such as IL-12, IFN-gamma and TNF-alpha. Because these cytokines appear to be important in the aetiology of inflammatory bowel disease, it is possible that they are involved in the mucosal pathogenesis of cryptosporidiosis.

Excretion patterns of mucosally delivered antibodies to p23 in Cryptosporidium parvum infected calves

Fecal samples obtained at intervals from six calves with acute cryptosporidiosis contained antibodies of multiple isotypes to p23. IgM-, IgA-, and IgG(1)-isotype anti-p23 appeared before IgG(2)-isotype antibodies. All anti-p23 antibodies had declined by 2 months after infection. One calf that failed to shed oocysts following initial exposure developed IgG(1)-isotype anti-p23 antibodies. One calf that died following exposure to Cryptosporidium parvum oocysts lacked detectable anti-p23 antibodies. Re-inoculation with C. parvum resulted in a brief, marked recall response to p23.

Cryptosporidium parvum and mucosal immunity in neonatal cattle

Cryptosporidium parvum is an important zoonotic protozoan pathogen that causes acute infection and self-limiting gastrointestinal disease in neonatal calves. There are currently no consistently effective antimicrobials available to control cryptosporidiosis. Therefore, immunotherapeutic and vaccination protocols offer the greatest potential for long-term control of the disease. In order to devise effective control measures, it is important to better define mucosal immunity to C. parvum in young calves. This review summarizes the information that has accumulated over the last decade which helps to define the intestinal mucosal immune system in neonatal calves, and the events that occur in the intestinal mucosa after infection by C. parvum.

Gut intraepithelial lymphocytes and immunity to Coccidia

Little is known about the physiological functions of the intra-epithelial lymphocytes (IELs) of mucosal tissues, including their role in immunity to infection. Most IELs are T cells, but their surface phenotype and activation characteristics are different from those of peripheral T cells. Here, Vincent McDonald outlines the distinctive features of IELs and presents evidence, particularly from studies of Coccidia, that these cells have an important role in the control of intracellular infection at the mucosal surface.

Speculation on whether a vaccine against cryptosporidiosis is a reality or fantasy

In this paper the authors question whether the development of a vaccine against cryptosporidiosis could be taken into consideration. The necessity and feasibility of such a vaccine for human and veterinary application is discussed. Developmental stages within the life cycle of the parasite that might act as possible targets for vaccine development are summarised, as well as the target antigens offered by molecular biology and immunology studies. Vaccination trials against cryptosporidiosis carried out so far, including the active and passive immunisation approach, are also overviewed. It seems that with respect to a Cryptosporidium vaccine two target groups can be considered: children of the developing world and neonatal ruminants. Antigens representing possible candidates for a subunit vaccine were identified based on their function, location and/or the immune response they evoke. While the active vaccination of newborn calves, lambs and goat kids has to face a number of important limitations, the passive immunisation approach, where dams were immunised to protect their progeny by colostral transfer, was proven to be a valuable alternative. Finally, a number of points of action for the near future are put forward.

A review of the importance of cryptosporidiosis in farm animals

Cryptosporidium species are coccidian parasites with a large capacity to reproduce and to disseminate. Several species are known to infect farm animals, although the economic importance of cryptosporidiosis is highly host species dependent. This paper reviews the impact of cryptosporidial infections in livestock and poultry. For different farm animals, the Cryptosporidium spp. that occur, as well as their clinical and pathological features, and their interactions with other pathogens, are described. In addition, data concerning the prevalence, the transmission and the epidemiology of the disease are mentioned and a description of the economic losses associated with cryptosporidiosis in each of the hosts is given. Cryptosporidiosis seems to be mainly a problem in neonatal ruminants. Cryptosporidium parvum is considered to be an important agent in the aetiology of the neonatal diarrhoea syndrome of calves, lambs and goat kids, causing considerable direct and indirect economic losses. Avian cryptosporidiosis is an emerging health problem in poultry, associated with respiratory disease in chickens and other Galliformes, and with intestinal disease in turkeys and quails. Because of limited availability of effective drugs, the control of cryptosporidiosis relies mainly on hygienic measures and good management.

Pathogenesis of Cryptosporidium parvum infection

Cryptosporidium parvum can be regarded as a minimally invasive mucosal pathogen, since it invades surface epithelial cells that line the intestinal tract but does not invade deeper layers of the intestinal mucosa. Nonetheless, infection can be associated with diarrhea and marked mucosal inflammation. This article briefly reviews in vitro and in vivo models useful for studying the pathogenesis of C. parvum infection and explores the role of innate and acquired immune responses in host defense against this protozoan parasite.

Bovine T cell responses to Cryptosporidium parvum infection

To better understand the immune mechanisms important for clearing of the primary infection and the subsequent development of resistance to Cryptosporidium parvum infection, several groups have recently characterised changes within the lymphoid cell population of the intestinal mucosa and associated lymphoid tissue in calves with cryptosporidiosis. In naive animals, infection results in a significant increase in the number of CD4+ and CD8+ T cells present within the intraepithelial lymphocyte population, lamina propria and Peyer's patch of the ileum. This is accompanied by a rapid and transient increase in the number of gamma/delta T cells present within the intestinal villi. In response to a challenge infection in immune calves, there is a substantial increase in the number of CD4+ T cells present in the Peyer's patch of the ileum and a specific localization of CD8+ T cells to the epithelium of the intestinal villi. Together, these data demonstrate that C, parvum elicits a strong cell-mediated response following both primary and secondary infections in calves, and that CD8+ T cells may play an important role in the bovine immune response to C. parvum infection.

Susceptibility and serologic response of healthy adults to reinfection with Cryptosporidium parvum

Healthy adults are susceptible to infection with small numbers of Cryptosporidium parvum oocysts, resulting in self-limited infection. We investigated if infection of humans with C. parvum is protective 1 year after primary exposure. At 1 year after a primary challenge with 30 to 10(6) oocysts, 19 healthy immunocompetent adults were rechallenged with 500 oocysts and monitored for the development of infection and/or illness. Oocyst excretion was quantitated by direct immunofluorescence with a C. parvum-specific monoclonal antibody, and anti-C. parvum antibodies in serum were detected by an enzyme-linked immunosorbent assay. Fewer subjects shed oocysts after the second exposure (3 of 19; 16%) than after the first exposure (12 of 19; 63%) (P < 0.005). Although the rates of diarrhea were comparable after each of the two exposures, the clinical severity as determined by the mean number of unformed stools passed was lower after reexposure (11.25 versus 8.62; P < 0.05). The number of anti-Cryptosporidium immunoglobulin G and A seroconversions increased after secondary exposure. However, the C. parvum serum antibody response did not correlate with the presence or absence of infection.

Cryptosporidium parvum infection in bovine neonates: dynamic clinical, parasitic and immunologic patterns

Twenty-six experimentally infected calves were monitored daily for oocyst excretion. All began excreting oocysts 3-6 days p.i. Most calves (n = 23) excreted oocysts for 6-9 days, with a daily range from 4 x 10(2) to 4.15 x 10(7) oocysts g(-1) of faeces. Over half the calves excreted peak numbers of oocysts 6-8 days p.i. Diarrhoea, observed intermittently beginning as early as day 3 p.i., lasted 4-16 days and varied greatly in severity from calf to calf. In a second study, nine of 18 calves were orally inoculated with 5 x 10(6) oocysts between birth and 2 days of age and nine remained uninfected. Monoclonal antibodies for cell surface markers indicated substantial increases in CD4+ and CD8+ T cells in the intraepithelial lymphocyte population of the ilea of infected calves at 7-9 days of age. RT-PCR demonstrated increases in mRNA for interleukin-12 and interferon-gamma that correlated with increases in both CD4+ and CD8 + intraepithelial lymphocyte cells. Increased mRNA for interleukin-12 and interferon-gamma from lamina propria lymphocytes correlated with increased numbers of CD8+ cells. No changes were found in interleukin-2, interleukin-4 or interleukin-10 mRNA levels. However, interleukin-15 mRNA, possibly from epithelial cells contaminating intraepithelial lymphocytes, was decreased in infected calves and had a negative correlation with increases in CD4+ and CD8+ cells. No differences were detected in mRNA levels for cytokines from lymph node lymphocytes.