Differential expression of Cryptosporidium parvum genes encoding sporozoite surface antigens in infected HCT-8 host cells

Construction of a recombinant food-grade Lactococcus lactis expressing P23 protein of Cryptosporidium parvum

Cryptosporidium parvum infects enterocytes in diverse vertebrates, including humans, and causes diarrheal illness. However, no effective drugs are available for this protozoan infection. The P23 protein of C. parvum is a protective antigen, considered a potential candidate for developing an effective vaccine against cryptosporidiosis. In this study, the complementary DNA (cDNA) of the p23 gene was subcloned to Escherichia coli DH5α, with one nucleotide difference. The constructed plasmid pNZ8149-P23 was transferred by electroporation to Lactococcus lactis NZ3900, and the recombinant L. lactis NZ3900/pNZ8149-P23 strain was screened in Elliker-medium by adding bromocresolpurple indicator. A 23-kDa protein was detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) after nisin induction in LM17 broth medium, suggesting that P23 protein was in the form of glycosylation. Simultaneously, an optimal induction time of 9 h was determined, and the density of OD₆₀₀ = 2.7 was tested. Through western blot and indirect immunofluorescence (IIF) analysis, the immunocompetence of expressed P23 antigen was identified, and its location of release to the cell interior of recombinant L. lactis was manifested. The first report of a food-grade genetically engineered L. lactis strain expressing a P23 antigen of C. parvum is herein presented. This result provides a novel and safe utilization method of P23 against C. parvum infection.

Differential Expression of Three Cryptosporidium Species-Specific MEDLE Proteins

Cryptosporidium parvum and Cryptosporidium hominis share highly similar proteomes, with merely ~3% divergence in overall nucleotide sequences. Cryptosporidium-specific MEDLE family is one of the major differences in gene content between the two species. Comparative genomic analysis indicated that MEDLE family may contribute to differences in host range among Cryptosporidium spp. Previous studies have suggested that CpMEDLE-1 encoded by cgd5_4580 and CpMEDLE-2 encoded by cgd5_4590 are potentially involved in the invasion of C. parvum. In this study, we expressed in Escherichia coli, the C. hominis-specific member of the MEDLE protein family, ChMEDLE-1 encoded by chro.50507, and two C. parvum-specific members, CpMEDLE-3 encoded by cgd5_4600 and CpMEDLE-5 encoded by cgd6_5480. Quantitative PCR, immunofluorescence staining and in vitro neutralization assay were conducted to assess their biologic characteristics. The expression of the cgd5_4600 gene was high during 12–48 h of the in vitro culture, while the expression of cgd6_5480 was the highest at 2 h. ChMEDLE-1 and CpMEDLE-3 proteins were mostly located in the anterior and mid-anterior region of sporozoites and merozoites, whereas CpMEDLE-5 was expressed over the entire surface of these invasive stages. Polyclonal antibodies against MEDLE proteins had different neutralization efficiency, reaching approximately 50% for ChMEDLE-1 and 60% for CpMEDLE-3, but only 20% for CpMEDLE-5. The differences in protein and gene expression and neutralizing capacity indicated the MEDLE proteins may have different roles during Cryptosporidium invasion and growth.

Characterization of MEDLE-1, a protein in early development of Cryptosporidium parvum

Background

Cryptosporidium spp. are important diarrhea-causing pathogens in humans and animals. Comparative genomic analysis indicated that Cryptosporidium-specific MEDLE family proteins may contribute to host adaptation of Cryptosporidium spp., and a recent study of one member of this family, CpMEDLE-2 encoded by cgd5_4590, has provided evidence supporting this hypothesis. In this study, another member of the protein family, CpMEDLE-1 of Cryptosporidium parvum encoded by cgd5_4580, which is distinct from CpMEDLE-2 and has no signature motif MEDLE, was cloned, expressed and characterized to understand its function.

Methods

CpMEDLE-1 was expressed in Escherichia coli and polyclonal antibodies against the recombinant CpMEDLE-1 protein were prepared in rabbits. Quantitative PCR was used to analyze the expression profile of cgd5_4580 in C. parvum culture. Immunofluorescence staining was used to locate CpMEDLE-1 expression in life-cycle stages, and in vitro neutralization assay with antibodies was adopted to assess the role of the protein in C. parvum invasion.

Results

The results indicated that cgd5_4580 had a peak expression at 2 h of C. parvum culture. CpMEDLE-1 was located in the mid-anterior region of sporozoites, probably within the dense granules. The neutralization efficiency of anti-CpMEDLE-1 antibodies was approximately 40%.

Conclusions

The differences in protein and gene expression profiles between CpMEDLE-1 and CpMEDLE-2 suggest that MEDLE proteins have different subcellular locations, are developmentally regulated, could be potentially involved in the transcriptional regulation of the expression of parasite or host proteins and may exert their functions in different stages of the invasion and development process.

Preliminary Characterization of MEDLE-2, a Protein Potentially Involved in the Invasion of Cryptosporidium parvum

Cryptosporidium spp. are important causes of diarrhea in humans, ruminants, and other mammals. Comparative genomic analysis indicated that genetically related and host-adapted Cryptosporidium species have different numbers of subtelomeric genes encoding the Cryptosporidium-specific MEDLE family of secreted proteins, which could contribute to differences in host specificity. In this study, a Cryptosporidium parvum-specific member of the protein family MEDLE-2 encoded by cgd5_4590 was cloned and expressed in Escherichia coli. Immunofluorescent staining with antibodies generated from the recombinant protein showed the expression of the protein in sporozoites and development stages. In vitro neutralization assay with the antibodies partially blocked the invasion of sporozoites. These results support the potential involvement of MEDLE-2 in the invasion of host cells.

Preassembled Single-Stranded RNA-Argonaute Complexes: A Novel Method to Silence Genes in Cryptosporidium

Cryptosporidiosis is a common cause of diarrhea morbidity and mortality worldwide. Research progress on this infection has been slowed by lack of methods to genetically manipulate Cryptosporidium parasites. Small interfering RNA (siRNA) is widely used to study gene function, but Cryptosporidium species lack the enzymes necessary to process siRNA. By preassembling complexes with the human enzyme Argonaute 2 (hAgo2) and Cryptosporidium single-stranded RNA (ssRNA), we induced specific slicing in Cryptosporidium RNA targets. We demonstrated the reduction in expression of target genes at the mRNA and protein levels by transfecting live parasites with ssRNA-hAgo2 complexes. Furthermore we used this method to confirm the role of selected molecules during host cell invasion. This novel method provides a novel means of silencing Cryptosporidium genes to study their role in host-parasite interactions and as potential targets for chemotherapy.

Cryptosporidiuminfections: molecular advances

Cryptosporidiumhost cell interaction remains fairly obscure compared with other apicomplexans such asPlasmodiumorToxoplasma. The reason for this is probably the inability of this parasite to complete its life cyclein vitroand the lack of a system to genetically modifyCryptosporidium. However, there is a substantial set of data about the molecules involved in attachment and invasion and about the host cell pathways involved in actin arrangement that are altered by the parasite. Here we summarize the recent advances in research on host cell infection regarding the excystation process, attachment and invasion, survival in the cell, egress and the available data on omics.

Dysfunctions at human intestinal barrier by water-borne protozoan parasites: lessons from cultured human fully differentiated colon cancer cell lines

Some water-borne protozoan parasites induce diseases through their membrane-associated functional structures and virulence factors that hijack the host cellular molecules and signalling pathways leading to structural and functional lesions in the intestinal barrier. In this Microreview we analyse the insights on the mechanisms of pathogenesis of Entamoeba intestinalis, Giardia and Cryptosporidium observed in the human colon carcinoma fully differentiated colon cancer cell lines, cell subpopulations and clones expressing the structural and functional characteristics of highly specialized fully differentiated epithelial cells lining the intestinal epithelium and mimicking structurally and functionally an intestinal barrier.

Cryptic parasite revealed improved prospects for treatment and control of human cryptosporidiosis through advanced technologies

Cryptosporidium is an important genus of parasitic protozoa of humans and other vertebrates and is a major cause of intestinal disease globally. Unlike many common causes of infectious enteritis, there are no widely available, effective vaccine or drug-based intervention strategies for Cryptosporidium, and control is focused mainly on prevention. This approach is particularly deficient for infections of severely immunocompromised and/or suppressed, the elderly or malnourished people. However, cryptosporidiosis also presents a significant burden on immunocompetent individuals, and can, for example have lasting effects on the physical and mental development of children infected at an early age. In the last few decades, our understanding of Cryptosporidium has expanded significantly in numerous areas, including the parasite life-cycle, the processes of excystation, cellular invasion and reproduction, and the interplay between parasite and host. Nonetheless, despite extensive research, many aspects of the biology of Cryptosporidium remain unknown, and treatment and control are challenging. Here, we review the current state of knowledge of Cryptosporidium, with a focus on major advances arising from the recently completed genome sequences of the two species of greatest relevance in humans, namely Cryptosporidium hominis and Cryptosporidium parvum. In addition, we discuss the potential of next-generation sequencing technologies, new advances in in silico analyses and progress in in vitro culturing systems to bridge these gaps and to lead toward effective treatment and control of cryptosporidiosis.

Immunogenicity of orally administrated recombinant Lactobacillus casei Zhang expressing Cryptosporidium parvum surface adhesion protein P23 in mice

Cryptosporidium parvum, an intestinal apicomplexan parasite, is a significant cause of diarrheal diseases in both humans and animals. What is more, there is no promising strategy for controlling cryptosporidiosis. In this study, the P23 immunodominant surface protein of C. parvum sporozoites was stably expressed in the Lactobacillus casei Zhang strain and its immunogenicity was evaluated in a mouse model. The molecular weight (23 kDa) and immunogenicity of p23 gene expressed by L. casei Zhang were similar to that of the native P23 protein. Oral immunization with control L. casei Zhang and recombinant L. casei Zhang-p23 activated the mucosal immune system to elicit serum immunoglobulin G (IgG) and mucosal IgA in mice. Furthermore, the expression of cytokines such as IL-4, IL-6, and IFN-γ in splenocytes of mice was detected by real-time PCR after oral immunization. P23-specific immunocyte activation was also verified. These findings indicate that the live L. casei Zhang vector may be a new tool for the production of mucosal vaccines against cryptosporidiosis in animals.

Molecular characterization of Cryptosporidium isolates from humans in Ethiopia

In this study, 1034 faecal samples from patients with diarrhoea were screened for Cryptosporidium oocysts. Samples were collected from nine different regions in Ethiopia. Of these, 79 samples (7.6%) were positive for Cryptosporidium by modified Ziehl-Neelson staining. From all positive samples DNA was extracted and PCR amplification of the COWP, SSU-rRNA and GP60 gene fragments was performed. A total of 41 samples (52%) were positive in any of the three typing methods. The majority of isolates (39 of 41) was identified as Cryptosporidium parvum, with one Cryptosporidium hominis and one mixed infection. Sequencing of the GP60 gene fragments of 13 isolates resulted in three different subgenotypes of C. parvum, all belonging to the zoonotic subtype family IIa and one subtype of C. hominis (Ib). These data identify C. parvum as the major cause of human cryptosporidiosis in Ethiopia and suggest a zoonotic transmission of the disease in contrast to reports from other developing countries.

Recombinant Cryptosporidium parvum p23 as a target for the detection of Cryptosporidium-specific antibody in calf sera

Cryptosporidium parvum is a widely distributed coccidian parasite and causes enteric disease in humans and animals. In addition to being a cause of life-threatening disease in immunodeficient people, mostly AIDS patients, C. parvum has been reported as a common serious primary cause of outbreaks of diarrhea in newborn calves, especially newborn ruminants (De Graaf et al. in Int J Parasitol 29:1269-1287, 1999). To obtain the recombinant P23 protein, we isolated the mRNA from oocyst of C. parvum and amplified the cDNA of P23 gene by reverse transcriptase PCR. Sequencing of cDNA showed 100% homology to the known P23 sequences. The double strand P23-cDNA was then cloned in pGEX-5X-2 expression vector. Western blot analysis of recombinant P23 showed that it could be recognized by the positive C. parvum serum. Since P23 is an immunodominant surface glycoprotein expressed in the early phase of infection (Jakobi and Petry in Microbes Infect 8:2186-2194, 2006) and the immunogenic epitopes are also found in the residual chain of amino acid sequence of this glycoprotein, the recombinant P23 was used for the screening of 437 serum samples collected from calves (#264) and cattle (#173). The dot blot analysis showed that from 264 calf and 173 cattle sera, 33% and 37% sera were positive, respectively. Due to the simple handling and equipment, dot blot analysis with P23 could be recommended for calves screening against cryptosporidiosis.

Binding and activation of human and mouse complement by Cryptosporidium parvum (Apicomplexa) and susceptibility of C1q- and MBL-deficient mice to infection

Cryptosporidium parvum is a protozoan parasite (Apicomplexa) that causes gastrointestinal disease in animals and humans. Whereas immunocompetent hosts can limit the infection within 1 or 2 weeks, immunocompromised individuals develop a chronic, life-threatening disease. The importance of the adaptive cellular immune response, with CD4+ T-lymphocytes being the major players, has been clearly demonstrated. Several non-adaptive immune mechanisms have been suggested to contribute to the host defence, such as interferon-gamma (IFN-gamma) from NK cells, certain chemokines, beta-defensins and pro-inflammatory cytokines, but the influence of the complement systems has been less well studied. We analysed the in vitro binding and activation of the human and mouse complement systems and tested the susceptibility to infection in complement-deficient mouse strains. We found that C. parvum can activate both the classical and lectin pathways, leading to the deposition of C3b on the parasite. Using real-time PCR, parasite development could be demonstrated in adult mice lacking mannan-binding lectin (MBL-A/C-/-) but not in mice lacking complement factor C1q (C1qA-/-) or in wild type C57BL/6 mice. The contribution of the complement system and the lectin pathway in particular to the host defence against cryptosporidiosis may become apparent in situations of immunodeficiency such as HIV infections or in early childhood.

Humoral immune response in IL-12 and IFN-gamma deficient mice after infection with Cryptosporidium parvum

Infection with Cryptosporidium spp. causes diarrhoeal disease and has become an important medical and veterinary problem especially in the immunocompromised host. The importance of the adaptive immune response, with CD4+ T-lymphocytes being the major players, has been clearly demonstrated. The requirement of IL-12 and IFN-gamma identifies this response as a Th1-dominated reaction. IFN-gamma is also important in the early phase of the host-parasite interaction. We analysed the outcome of infection in IL-12p40 (IL-12KO) and IFN-gamma (GKO) deficient C57BL/6 mice after primary and secondary challenge with the parasite and, for the first time, we demonstrate the resulting Ig response in sera and vaginal lavages. Although showing differences in the extent and the time course both strains of mice were able to clear infection and developed an almost complete resistance to re-infection. While GKO mice mounted prolonged parasite-specific IgG and IgA responses after primary infection, in IL-12KO mice IgG and IgA titres dropped over time. Re-challenge of mice 5 weeks after primary infection led to a booster effect in Ig response despite the absence of oocyst shedding. The data from infection and re-challenge experiments suggest that in IL-12- or IFN-gamma-deficient mice the development of resistance involves other protective immune responses.