Neospora caninum: In vitro culture of tachyzoites in MCF-7 human breast carcinoma cells

Molecular mimicry between parasites and cancer: a novel approach for developing cancer vaccines and therapeutic antibodies

Cancer is one of the most dreaded diseases worldwide. Conventional treatments such as surgery, chemotherapy, and radiotherapy have limitations and adverse effects. Cancer immunotherapy and targeted therapies offer new treatment options. Parasite-based cancer therapy shows promise in fighting tumors. Some parasites have anti-cancer properties through multi-mechanistic strategies, with the molecular mimicry theory as a leading explanation for parasites' anti-cancer effects. This study aimed to explore the existence of shared antigenic proteins between parasites (Trichinella spiralis, Schistosoma mansoni, and Toxoplasma gondii) and cancer cell lines (MCF-7 human breast cancer and A549 human lung cancer). Polyclonal antisera against T. spiralis, S. mansoni, and T. gondii parasites were generated in rabbits. Antibody reactivity with extracts of MCF-7 and A549 cancer cells was detected using SDS-PAGE and immunoblotting. Results documented the molecular mimicry between parasites and cancers as it revealed cross-reactive bands when using T. spiralis antibodies against MCF-7 and A549 cancer cell extracts at approximate molecular weights of 70 and 35 kDa, and with S. mansoni antibodies at an approximate molecular weight of 80 kDa. Toxoplasma gondii antibodies neither reacted with MCF-7 human breast cancer nor A549 human lung cancer cell extracts. Results of this study could establish a foundation for subsequent investigation among a broad range of parasites for molecular mimicry with cancers. Identification, molecular characterization, and investigation of the anti-neoplastic activity of these cross-reactive antigens could shed light on new pathways for the potential development of a novel class of innovative cancer vaccine candidates and therapeutic antibodies of parasitic origin for cancer immunotherapy and targeted therapy.

Unveiling the anti-neoplastic potential of Schistosoma mansoni-derived antigen against breast cancer: a pre-clinical study

BACKGROUND

Cancer is a global health concern, with millions of new cases and deaths annually. Recently, immunotherapy has strengthened cancer treatment by harnessing the body's immune system to fight cancer. The search for advanced cancer immunotherapies has expanded to explore pathogens like parasites for their potential anti-neoplastic effects. While some parasites have shown promising results, the role of Schistosoma mansoni in breast cancer remains unexplored.

METHODS

This pre-clinical study investigated the anti-neoplastic potential of autoclaved Schistosoma mansoni antigen against breast cancer. In vitro, autoclaved Schistosoma mansoni antigen was evaluated on the MCF-7 human breast cancer cell line, while in vivo experiments used a chemically induced breast cancer rat model to evaluate tumour growth, liver enzyme levels, and immune response. Histopathological and immunohistochemical analyses assessed changes in tumour tissue, cell proliferation (Ki-67), angiogenesis (CD31), immune cell infiltration (CD8+ T cells), regulatory T cells (FoxP3+), and programmed death ligand 1 (PD-L1) expression.

RESULTS

In vitro, autoclaved Schistosoma mansoni antigen significantly reduced MCF-7 cell viability in a dose- and time-dependent manner. In vivo, autoclaved Schistosoma mansoni antigen treatment significantly reduced tumour weight and volume, improved liver enzyme levels, increased tumour necrosis, and decreased fibrosis. Immunohistochemical analysis revealed decreased Ki-67 and CD31 expression, indicating reduced cell proliferation and angiogenesis, respectively. Autoclaved Schistosoma mansoni antigen also enhanced immune responses by increasing CD8+ T cells infiltration and decreasing FoxP3+ expression, resulting in a higher CD8+ T cells/FoxP3+ ratio within the tumour microenvironment. Notably, PD-L1 expression was also downregulated, suggesting potential immune checkpoint inhibition.

CONCLUSIONS

Autoclaved Schistosoma mansoni antigen demonstrated potent anti-neoplastic activity, significantly reducing tumour growth and modulating the immune response within the tumour microenvironment. These results highlight autoclaved Schistosoma mansoni antigen's potential as a novel immunotherapy for breast cancer.

Variations in extracellular vesicle shedding of Cystoisospora suis stages (Apicomplexa: Coccidia)

Cystoisospora suis, a porcine enteral parasite of the order Coccidia, is characterized by a complex life cycle, with asexual and sexual development in the epithelium of the host gut and an environmental phase as an oocyst. All developmental stages vary greatly in their morphology and function, and therefore excrete different bioactive molecules for intercellular communication. Due to their complex development, we hypothesized that the extracellular vesicles (EVs) cargo is highly dependent on the life cycle stages from which they are released. This study aimed to characterize and compare EVs of all developmental stages of C. suis. Nanoparticle tracking analysis and microscopy were used to determine particle numbers and size distributions of stage-specific parasite EVs. Furthermore, Fourier-transform infrared spectral analysis was employed for the metabolic fingerprinting of EVs, and the lipid and protein profiles of all parasite stages were determined. Overall, the study revealed that asexual, sexual and transmissible stages of C. suis release different EVs during the parasite's life cycle. EVs of endogenous asexual and sexual stages were found to be more similar to each other than to those of the transmissible environmental stage, the oocyst. Furthermore, the ratio of fatty acids to polysaccharides and proteins changed during parasite development. In particular, proteins associated with the Apicomplexa and those involved in vesicle shedding showed changes in expression in all parasite stages. Lipid analysis showed that fatty acids were found in the same concentration through all parasite stages, whereas the amount of stereolipids, sphingolipids and glycerolipids changed between the parasite stages. In conclusion, this study, which presents the first known characterization of C. suis EVs, demonstrates a link between EVs and the respective developmental stages of the parasite, and putative functions in the parasite-parasite and host-parasite interplays.

Parasites revive hope for cancer therapy

Parasites have attained a life-long stigma of being detrimental organisms with deleterious outcomes. Yet, recently, a creditable twist was verified that can dramatically change our perception of those parasites from being a source of misery to millions of people to a useful anti-cancerous tool. Various parasites have shown promise to combat cancer in different experimental models, including colorectal, lung, and breast cancers, among others. Helminths and protozoan parasites, as well as their derivatives such as Echinococcus granulosus protein KI-1, Toxoplasma gondii GRA15II, and Trypanosoma cruzi calreticulin, have demonstrated the ability to inhibit tumor growth, angiogenesis, and metastasis. This article provides an overview of the literature on various cancer types that have shown promising responses to parasite therapy in both in vitro and in vivo animal studies. Parasites have shown anti-neoplastic activity through a variety of mechanisms that collectively contribute to their anti-cancer properties. These include immunomodulation, inhibition of angiogenesis, and molecular mimicry with cancer cells. This review article sheds light on this intriguing emerging field and emphasizes the value of collaborative multidisciplinary research projects with funding agencies and pharmaceutical companies. Thus, these strategies would secure continuous exploration of this new avenue and accelerate the advancement of cancer therapy research. Although experimental studies are heavily conducted by leaps and bounds, further steps are definitely lagging. Upgrading research from the experimental level to the clinical trial would be a wise progression toward efficient exploitation of the anti-neoplastic capabilities of parasites, ultimately saving countless lives.

Neospora caninum peroxiredoxin 1 is an essential virulence effector with antioxidant function

Neospora caninum, an obligate intracellular parasitic protozoan discovered by Dubey in 1988, is the pathogen of neosporosis, which causes neurological symptoms in dogs and abortions in cows. Since there is no effective drug or vaccine against N. caninum, a deeper understanding of the molecules critical to parasite survival inside host cells is necessary. This study aimed to determine the role of N. caninum peroxiredoxin 1 (NcPrx1) in maintaining redox homeostasis and virulence of N. caninum. By determining the localization of NcPrx1 protein and establishing NcPrx1 gene knockout strain (ΔNcPrx1), the roles of NcPrx1 in N. caninum for invasion, replication, growth, oxidative stress, as well as pathogenicity were investigated. Our results showed that a predicted Alkyl Hydroperoxide1 (AHP1) domain was found in the amino acid sequence of NcPrx1, which displayed a high degree of similarity to homologs of several protozoa. Immunofluorescence assay (IFA) indicated that NcPrx1 was a cytoplasmic protein in N. caninum tachyzoites. Compared to wild type (WT) strain, ΔNcPrx1 strain showed reduced plaque area, invasion and egress rates. Reactive oxygen species (ROS) and malondialdehyde (MDA) were accumulated, and total antioxidant capacity (T-AOC) was attenuated in ΔNcPrx1 tachyzoites, which indicated that ΔNcPrx1 strain was more sensitive to oxidative stress. Furthermore, ΔNcPrx1 strain-infected C57BL/6 mice showed improved survival rate, reduced parasite burden, alleviated pathological changes in tissues, and decreased secretions of IL-6, IL-12, TNF-α, and IFN-γ in serum compared to the WT strain group. These findings suggested that NcPrx1 was a virulence factor of N. caninum which played an important role in maintaining the redox homeostasis of the parasite.

In vitro cultivation methods for coccidian parasite research

The subclass Coccidia comprises a large group of protozoan parasites, including important pathogens of humans and animals such as Toxoplasma gondii, Neospora caninum, Eimeria spp., and Cystoisospora spp. Their life cycle includes a switch from asexual to sexual stages and is often restricted to a single host species. Current research on coccidian parasites focuses on cell biology and the underlying mechanisms of protein expression and trafficking in different life stages, host cell invasion and host-parasite interactions. Furthermore, novel anticoccidial drug targets are evaluated. Given the variety of research questions and the requirement to reduce and replace animal experimentation, in vitro cultivation of Coccidia needs to be further developed and refined to meet these requirements. For these purposes, established culture systems are constantly improved. In addition, new in vitro culture systems lately gained considerable importance in research on Coccidia. Well established and optimized in vitro cultures of monolayer cells can support the viability and development of parasite stages and even allow completion of the life cycle in vitro, as shown for Cystoisospora suis and Eimeria tenella. Furthermore, new three-dimensional cell culture models are used for propagation of Cryptosporidium spp. (close relatives of the coccidians), and the infection of three-dimensional organoids with T. gondii also gained popularity as the interaction between the parasite and host tissue can be studied in more detail. The latest advances in three-dimensional culture systems are organ-on-a-chip models, that to date have only been tested for T. gondii but promise to accelerate research in other coccidians. Lastly, the completion of the life cycle of C. suis and Cryptosporidium parvum was reported to continue in a host cell-free environment following the first occurrence of asexual stages. Such axenic cultures are becoming increasingly available and open new avenues for research on parasite life cycle stages and novel intervention strategies.

Characteristic pro-inflammatory cytokines and host defence cathelicidin peptide produced by human monocyte-derived macrophages infected withNeospora caninum

Neospora caninumis a coccidian intracellular protozoan capable of infecting a wide range of mammals, although severe disease is mostly reported in dogs and cattle. Innate defences triggered by monocytes/macrophages are key in the pathogenesis of neosporosis, as these cells are first-line defenders against intracellular infections. The aim of this study was to characterize infection and innate responses in macrophages infected withN. caninumusing a well-known cell model to study macrophage functions (human monocyte THP-1 cells). Intracellular invasion of live tachyzoites occurred as fast as 4 h (confirmed with immunofluorescence microscopy usingN. caninum-specific antibodies). Macrophages infected byN. caninumhad increased expression of pro-inflammatory cytokines (TNFα, IL-1β, IL-8, IFNγ). Interestingly,N. caninuminduced expression of host-defence peptides (cathelicidins), a mechanism of defence never reported forN. caninuminfection in macrophages. The expression of cytokines and cathelicidins in macrophages invaded byN. caninumwas mediated by mitogen-activated protein kinase (MEK 1/2). Secretion of such innate factors fromN. caninum-infected macrophages reduced parasite internalization and promoted the secretion of pro-inflammatory cytokines in naïve macrophages. We concluded that rapid invasion of macrophages byN. caninumtriggered protective innate defence mechanisms against intracellular pathogens.

Identification and characterization of GRA6/GRA7 of Neospora caninum in MDBK cells

Neospora caninum, an apicomplexan parasite, is recognized as a major bovine abortifacient. Dense granule antigens (GRAs) play important roles in the formation and modification of parasitophorous vacuoles (PVs) in Toxoplasma gondii. However, a few studies investigating GRAs have been reported in N. caninum. The aim of the present study was to characterize the dense GRA6/GRA7 of N. caninum in PVs using MDBK cells as a host cell model. Neospora caninum was inoculated into MDBK cells, and changes were observed using a transmission electron microscope (TEM). Neospora caninum GRA6/GRA7 were identified and characterized using bioinformatics, cell fractionation, and immunofluorescence. The TEM results revealed that integrated PVs were present in MDBK cells after N. caninum infection. Bioinformatics analysis showed that NcGRA6/NcGRA7 shared 28.76% and 29.66% homology with T. gondii GRA6/GRA7 (TgGRA6/TgGRA7) but had similar signal peptides, transmembrane domains, and motifs. Cell fractionation and subcellular localization analyses both showed that NcGRA6 was distributed in the lumen and intravacuolar network in soluble and transmembrane forms. The transmembrane form of NcGRA7 was observed in the PV membrane. These data lay a foundation for further study on bovine neosporosis and NcGRA6/NcGRA7 function during PV formation.

Comparison of use of Vero cell line and suspension culture of murine macrophage to attenuation of virulence of Neospora caninum

In this study the tachyzoite yields of Neospora caninum were compared in two cell lines: Vero (African Green Monkey Kidney) and suspension culture of murine macrophage (J774) cell lines. Then, N. caninum were continuously passaged in these cell lines for 3 months and the effect of host cells on virulence of tachyzoites was assessed by broiler chicken embryonated eggs. Inoculation was performed in the chorioallantoic (CA) liquid of the embryonated eggs with different dilutions (0.5 × 10(4), 1.0 × 10(4), 1.5 × 10(4)) of tachtzoites isolated from these cell cultures. The mortality pattern and pathological changes of the dead embryos and hatched chickens were noted. Tissue samples of brain, liver and heart were examined by histopathological and detection of DNA of parasite by polymerase chain reaction (PCR). Also, consecutive sections of the tissues examined histologically were used for immunohistochemical (IHC) examination. Embryos inoculated with tachyzoites derived from Vero cell line (group V) showed a higher mortality rate (100%) than the embryos that received tachyzoites derived from J774 cell line (group J) (10% mortality rate). The results of this study indicated that the culture of N. caninum in J774 cell led to a marked increase in the number of tachyzoite yields and rapid attenuation in comparison to Vero, so the results were confirmed by IHC and PCR. This study is the first report of the significant effect of host cell on the attenuation of virulence of N. caninum tachyzoites. These findings could potentially provide a practical approach in the mass production of N. caninum tachyzoites, and also in producing live attenuated vaccine.

Neospora caninum surface antigen (p40) is a potential diagnostic marker for cattle neosporosis

Neospora caninum is an intracellular protozoan that infects domestic and wild canids as well as many warm-blooded animals as shown by the isolation of viable parasites. The effectiveness of diagnostic tests for detecting specific antibodies against N. caninum is hampered by potential cross-reaction with other Coccidia. So, there is currently an urgent need for a sensitive and specific diagnostic assay for detecting N. caninum in animals. The N. caninum 40-kD surface antigen (p40), similar to NcSAG1 and NcSRS2, was shown to belong to surface antigen super family and thus represents an excellent marker for the diagnosis of neosporosis. In order to test the hypothesis, recombinant Ncp40 (rNcp40) was expressed in Escherichia coli, and an indirect ELISA test was developed using recombinant NCp40 antigen for N. caninum serodiagnosis. The antigen used in this study did not have cross-reactivity with anti-Toxoplasma gondii serum. Anti-p40 antibodies were detected by ELISA in the sera of Yellow cattle and were compared with (IFAT). Optimal sensitivity and specificity (98.2 and 98.6 %) were identified by IFAT. Additionally, 37 positive sera of T. gondii were detected and there was no significant difference with the negative serum of N. caninum. The rNcp40 ELISA developed here provides a specific and sensitive assay for detecting neosporosis in cattle.