Encephalitozoonosis in pharmacologically immunosuppressed mice

CD8 T lymphocytes from B-1 cell-deficient mice down-regulates fungicidal activity of macrophages challenged with E. Cuniculi

BACKGROUND

Encephalitozoon cuniculi is an opportunistic intracellular pathogen that establishes a balanced relationship with immunocompetent individuals depending on the activity of their CD8+ T cells lymphocytes. However, lower resistance to experimental infection with E. cuniculi was found in B-1 deficient mice (Xid), besides increased the number of CD8 T lymphocytes. Here, we evaluated the profile of CD8+ T lymphocytes from Balb/c wild-type (WT) or Balb/c Xid mice (with B-1 cell deficiency) on the microbicidal activity of macrophages challenged with E. cuniculi.

METHODS

Naïve CD8 T lymphocytes from WT or Xid mice uninfected and primed CD8 T lymphocytes from WT or Xid mice infected with E cuniculi were co-cultured with macrophages previously challenged with E. cuniculi. We evaluated macrophages viability and microbicidal activity, and CD8 T lymphocytes viability and presence of activating molecules (CD62L, CD69, and CD107a).

RESULTS

Macrophages co-cultured with naïve CD8 T lymphocytes from WT demonstrated high microbicidal activity. Naïve CD8 T lymphocytes obtained from WT mice had a higher expression of CD69 and LAMP-1-activating molecules compared to Xid CD8+ T lymphocytes. Primed CD8 T lymphocytes from Xid mice proliferated more than those from WT mice, however, when the expression of the activating molecule CD69 associated with the expression of CD62L was kept low. In conclusion, naïve CD8+ T lymphocytes from Xid mice, deficient in B-1 cells, they had reduced expression of activation molecules and cytotoxic activity.

Increased susceptibility to encephalitozoonosis associated with mixed Th1/Th2 profile and M1/M2 profile in mice immunosuppressed with cyclophosphamide

Encephalitozoon cuniculi is a unicellular, spore-forming, obligate intracellular eukaryote belonging to the phylum Microsporidia. It is known to infect mainly immunocompromised and immunocompetent mammals, including humans. The parasite-host relationship has been evaluated using both in vitro cell culturing and animal models. For example, Balb/c and C57BL/6 mouse strains have been used interchangeably, although the latter has been considered more susceptible due to the higher fungal load observed after infection. In the present study, we identified the characteristics of the immune response of C57BL/6 mice treated or not with the immunosuppressant cyclophosphamide (Cy) and challenged with E. cuniculi by intraperitoneal route. After 14 days of infection, serum was collected to analyze Th1, Th2, and Th17 cytokine levels. In addition, peritoneal washes were performed, and the spleen sample was collected for immune cell phenotyping, whereas liver, spleen, kidney, lung, intestine, and central nervous system (CNS) samples were collected for histopathological analysis. Although infected mice displayed a reduced absolute number of macrophages, they showed an M1 profile, an elevated number of CD4+T, CD8+T, B-1, and B-2 lymphocytes, with a predominance of Th1 inflammatory cytokines (interferon [IFN]-γ, tumor necrosis factor [TNF]-α, and interleukin [IL]-2) and Th17. Furthermore, Cy-Infected mice showed a reduced absolute number of macrophages with an M1 profile but a reduced number of CD4+T, CD8+T, B-1, and B-2 lymphocytes, with a predominance of Th1 inflammatory cytokines (IFN-γ, TNF-α, and IL-2) and Th2 (IL-4). This group displayed a higher fungal burden as well and developed more severe encephalitozoonosis, which was associated with a reduced number of T and B lymphocytes and a mixed profile of Th1 and Th2 cytokines.

Mice with genetic and induced B-cell deficiency as a model for disseminated encephalitozoonosis

Encephalitozoon cuniculi, an intracellular pathogen, lives in a balanced relationship with immunocompetent individuals based on the activity of T lymphocytes. We previously highlighted the greater susceptibility of B-1 cell-deficient mice (XID mice) to encephalitozoonosis. This study aimed to develop a model of disseminated and severe encephalitozoonosis in mice with combined immunodeficiency to elucidate the role of B cells. To address this objective, cyclophosphamide (Cy)-treated BALB/c and XID mice were inoculated with E. cuniculi, followed by the evaluation of the immune response and histopathological lesions. Immunosuppressed BALB/c mice manifested no clinical signs with an increase in the populations of T lymphocytes and macrophages in the spleen. Immunosuppressed and infected XID mice revealed elevated T cells, macrophages populations, and pro-inflammatory cytokines levels (IFN-γ, TNF-α, and IL-6) with the presence of abdominal effusion and lesions in multiple organs. These clinical characteristics are associated with extensive and severe encephalitozoonosis. The symptoms and lesion size were reduced, whereas B-2 and CD4+ T cells populations were increased in the spleen by transferring B-2 cells adoptive to XID mice. Moreover, B-1 cells adoptive transfer upregulated the peritoneal populations of B-2 cells and macrophages but not T lymphocytes and decreased the symptoms. Herein, we speculated the consistency in the development of severe and disseminated encephalitozoonosis in mice with genetic deficiency of Bruton's tyrosine kinase (Btk) associated with Cy immunosuppression develop with that of the models with T cell deficiency. Taken together, these data emphasized the crucial role of B cells in the protective immune response against encephalitozoonosis.

Systems biology analysis of the effect and mechanism of total flavonoids of Astragali Radix against cyclophosphamide-induced leucopenia in mice

This study aimed to demonstrate the pharmacological mechanism of total flavonoids extracted from Astragali Radix (AR) on cyclophosphamide (Cy)-induced leucopenia in mice. First, flow cytometry, network pharmacology and plasma metabolomics were integrated to investigate the pharmacological mechanism of total flavonoids, the targets from network pharmacology and metabolites from metabolomics were analyzed by DAVID. Then, the key cytokines were validated to confirm the predicted metabolic pathway results. The results showed that total flavonoids significantly increased body weight, routine blood indices, bone marrow DNA cells, and also markedly caused lymphocyte proliferation by increasing the percentages of CD4⁺ and CD8⁺. Using network pharmacology and metabolomics methods, the study identified 13 signal-related pathways regulated by total flavonoids including PI3K-Akt signaling pathway, Jak-STAT signaling pathway, Sphingolipid signaling pathway, and so on. Total flavonoids also reversed changes in serum cytokines IL-2, IL-6, and GM-CSF. Total flavonoids exhibits protective effects against leucopenia probably by modulating immunologic functions, promoting cell proliferation, and regulating related metabolic pathways at the system level.

Cyclophosphamide Treatment Mimics Sub-Lethal Infections With Encephalitozoon intestinalis in Immunocompromised Individuals

Microsporidia, including Encephalitozoon intestinalis, are emerging pathogens which cause opportunistic infections in immunocompromised patients, such as those with AIDS, cancer, the elderly and people on immunosuppressive drugs. Intestinal mucosa (IM) is crucial for developing an efficient adaptive immune response against pathogenic micro-organisms, thereby preventing their colonization and subsequent infection. As immunosuppressive drugs affect the intestinal immune response is little known. In the present study, we investigated the immune response to E. intestinalis infection in the IM and gut-associated lymphoid tissue (GALT) in cyclophosphamide (Cy) immunosuppressed mice, to mimic an immunocompromised condition. Histopathology revealed lymphoplasmacytic enteritis at 7 and 14 days-post-infection (dpi) in all infected groups, however, inflammation diminished at 21 and 28 dpi. Cy treatment also led to a higher number of E. intestinalis spores and lesions, which reduced at 28 dpi. In addition, flow cytometry analysis demonstrated CD4⁺ and CD8⁺ T cells to be predominant immune cells, with up-regulation in both Th1 and Th2 cytokines at 7 and 14 dpi, as demonstrated by histopathology. In conclusion, Cy treatment reduced GALT (Peyer’s plaques and mesenteric lymph nodes) and peritoneum populations but increased the T-cell population in the intestinal mucosa and the production of pro-and anti-inflammatory cytokines, which were able to eliminate this opportunistic fungus and reduced the E. intestinalis infection.

Diabetes mellitus increases the susceptibility to encephalitozoonosis in mice

Microsporidiosis are diseases caused by opportunistic intracellular fungi in immunosuppressed individuals, as well as in transplanted patients, the elderly and children, among others. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and decreased T cell response, neutrophil function, humoral immunity failure, increasing the susceptibility to infections. Here, we investigated the susceptibility of streptozotocin (STZ)-induced type I diabetic and/or immunosuppressed mice to encephalitozoonosis by Encephalitozoon cuniculi. Microscopically, granulomatous hepatitis, interstitial pneumonia and pielonephritis were observed in all infected groups. STZ treatment induced an immunossupressor effect in the populations of B (B-1 and B2) and CD4⁺ T lymphocytes. Moreover, infection decreased CD4⁺ and CD8⁺ T lymphocytes and macrophages of DM mice. Furthermore, infection induced a significant increase of IL-6 and TNF-α cytokine serum levels in DM mice. IFN-γ, the most important cytokine for the resolution of encephalitozoonosis, increased only in infected mice. In addition to the decreased immune response, DM mice were more susceptible to encephalitozoonosis, associated with increased fungal burden, and symptoms. Additionally, cyclophosphamide immunosuppression in DM mice further increased the susceptibility to encephalitozoonosis. Thus, microsporidiosis should be considered in the differential diagnosis of comorbidities in diabetics.

Interferon γ and interleukin 10 responses in immunocompetent and immunosuppressed New Zealand White rabbits naturally infected with Encephalitozoon cuniculi

Levels of interferon (IFN)-γ and interleukin (IL)-10 were measured in the serum of immunocompetent and immunosuppressed New Zealand White rabbits naturally infected with Encephalitozoon cuniculi. IFN-γ levels were elevated in infected rabbits, and a synergic effect was observed in animals treated with the immunosuppressive agent dexamethasone (Dex). The role of IL-10 in infected rabbits remains unclear, as IL-10 levels were similar to those of negative controls. Dex appeared to exhibit a proinflammatory effect, as IFN-γ levels were elevated in infected immunosuppressed rabbits. Similarly, Dex exhibited a synergic effect in infected immunosuppressed rabbits, as evidenced by the elevation in IFN-γ production. These data indicate that the immune response to this glucocorticoid should be considered in the design of future animal model studies of immunosuppression.

Encephalitozoon cuniculi: Grading the Histological Lesions in Brain, Kidney, and Liver during Primoinfection Outbreak in Rabbits

This is the first confirmed report of Encephalitozoon cuniculi (E. cuniculi) in farm meat rabbits located in Northern Mexico. Eighty young rabbits exhibited clinical signs of this zoonotic emerging disease, like torticollis, ataxia, paresis, circling, and rolling. Samples of brain, kidney, and liver were examined for histology lesions. For the first time the lesions caused by E. cuniculi were graded according to their severity (I, II, and III) and the size of the granulomas (Types A, B, and C). The main cerebral injuries were Grade III, coinciding with the presence of Type C granulomas. The cerebral lesions were located in the cortex, brain stem, and medulla. The renal lesions were also Grade III distributed throughout cortex and renal medulla, with no granuloma formation. The involvement of hypersensitivity Types III and IV is suggested. All of the rabbits were seropositive to E. cuniculi by CIA testing, suggesting that this zoonotic and emerging pathogen is widely distributed among animals intended for human consumption. We believe this work could be used as a guide when examining E. cuniculi and will provide direction to confirm the diagnosis of this pathogen.

Microsporidiosis in Vertebrate Companion Exotic Animals

Veterinarians caring for companion animals may encounter microsporidia in various host species, and diagnosis and treatment of these fungal organisms can be particularly challenging. Fourteen microsporidial species have been reported to infect humans and some of them are zoonotic; however, to date, direct zoonotic transmission is difficult to document versus transit through the digestive tract. In this context, summarizing information available about microsporidiosis of companion exotic animals is relevant due to the proximity of these animals to their owners. Diagnostic modalities and therapeutic challenges are reviewed by taxa. Further studies are needed to better assess risks associated with animal microsporidia for immunosuppressed owners and to improve detection and treatment of infected companion animals.

Effect of three drugs against Encephalitozoon cuniculi infection in immunosuppressed mice

Microsporidia comprise a large group of obligate intracellular parasites. The microsporidian Encephalitozoon cuniculi causes disseminated infection in immunosuppressed patients with HIV, cancer, or transplants and in the elderly. In vivo and in vitro studies on the effectiveness of drugs are controversial. Currently, there is no effective treatment. We tested albendazole, albendazole sulfoxide, metronidazole, and cyclosporine in mice immunosuppressed with cyclophosphamide and inoculated by the intraperitoneal route with 10(7) E. cuniculi spores. One week after experimental inoculation, the mice were treated with albendazole, albendazole sulfoxide, metronidazole, and cyclosporine. Histological and morphometric analyses were performed to compare the treated groups. The state of immunosuppression was evaluated by phenotyping CD4(+) and CD8(+) T cells by flow cytometry. Nontreated mice showed acute disseminated and fatal encephalitozoonosis. The treatment with benzimidazoles significantly reduced infection until 30 days posttreatment (p.t.), but at 60 days p.t., the infection had recurred. Metronidazole decreased infection by a short time, and cyclosporine was not effective. All animals were immunosuppressed by all the experiments, as demonstrated by the low number of CD4(+) and CD8(+) T cells. We conclude that no drug was effective against E. cuniculi, but the benzimidazoles controlled the infection transiently.

Latent microsporidiosis caused by Encephalitozoon cuniculi in immunocompetent hosts: a murine model demonstrating the ineffectiveness of the immune system and treatment with albendazole

Background

Microsporidia are obligate intracellular parasites causing severe infections with lethal outcome in immunocompromised hosts. However, these pathogens are more frequently reported as latent infections in immunocompetent individuals and raises questions about the potential risk of reactivation following induced immunosuppression.

Aims

To evaluate the possibility latent microsporidiosis, efficacy or albendazole, and reactivation, the authors monitored the course of E. cuniculi infection in immunocompetent BALB/c mice and immunodeficient SCID mice using molecular methods.

Methods

Mice were per orally infected with 10⁷ spores of E. cuniculi. Selected groups were treated with albendazole, re-infected or chemically immunosuppressed by dexamethasone. The presence of microsporidia in the host’s organs and feces were determined using PCR methods. Changes in numbers of lymphocytes in blood and in spleen after induction of immunosuppression were confirmed using flow cytometry analysis.

Results

Whereas E. cuniculi caused lethal microsporidiosis in SCID mice, the infection in BABL/c mice remained asymptomatic despite parasite dissemination into many organs during the acute infection phase. Albendazole treatment led to microsporidia elimination from organs in BALB/c mice. In SCID mice, however, only a temporary reduction in number of affected organs was observed and infection re-established post-treatment. Dexamethasone treatment resulted in a chronic microsporidia infection disseminating into most organs in BALB/c mice. Although the presence of E. cuniculi in organs of albendazole- treated mice was undetectable by PCR, it was striking that infection was reactivated by immunosuppression treatment.

Conclusion

Our results demonstrated that microsporidia can successfully survive in organs of immunocompetent hosts and are able to reactivate from undetectable levels and spread within these hosts after induction of immunosuppression. These findings stress the danger of latent microsporidiosis as a life-threatening risk factor especially for individuals undergoing chemotherapy and in transplant recipients of organs originating from infected donors.