Antibody reaction of human anti-Toxoplasma gondii positive and negative sera with Neospora caninum antigens

Seroprevalences of Toxoplasma gondii and Neospora caninum infections in Jordanian women who had a recent spontaneous abortion

This cross-sectional study investigates Toxoplasma gondii and Neospora caninum among 445 recently spontaneously aborted (RSA) Jordanian women using ELISA and indirect fluorescent antibody (at a cut-off value of 1/200) tests, respectively. The type of hospital, age, cat and dog contacts, raw and barbecued meat and wild plant consumption, number of abortions, and stillbirths were tested as independent variables using univariate and multivariate logistic regression analyses. The true seroprevalences were 22.1% for T. gondii-IgG, 22.7% for N. caninum-IgG, 2.6% for T. gondii-IgM, 10.6% for N. caninum-IgM, 0% for T. gondii-IgG and IgM, 6.7% for N. caninum-IgG and IgM, and 4.6% and 0% for both parasite IgG and IgM, respectively. T. gondii-IgM-seropositivity was associated with the number of abortions with odds ratios (OR) of 2.4 and eating barbecued meat (OR = 0.12). N. caninum-IgG-seropositivity was associated with having a dog in the house (OR = 2.6), and with stillbirth (OR = 0.1). N. caninum-IgM was associated with visiting a private-hospital (OR = 2.7). RSA Jordanian women are equally exposed to both parasites with significantly (p < 0.05) higher seroprevalence of N. caninum-IgM compared to T. gondii-IgM suggestive of active infections among RSA women in Jordan.

Serological evaluation of Neospora caninum in pregnant women treated at referral center for prenatal screening in Mato Grosso do Sul, Brazil

Neospora caninum is an obligate intracellular protozoan with canids (Canis domesticus, Canis lupus dingo, Canis latrans, Canis lupus) as its definitive hosts. The objective of this study was to detect anti-N. caninum antibodies in pregnant women seen at referral center for prenatal screening in the state of state Mato Grosso do Sul, Brazil. A total of 188 serum samples from pregnant women provided by the Instituto de Pesquisa, Ensino e Diagnósticos da APAE de Campo Grande (IPED/ APAE) were subjected to IFA test and western blot analysis. The samples were divided into three groups: 23/99 samples from the seropositive group for toxoplasmosis were positive for anti-N. caninum IgG antibodies, and 9/99 positive for IgM; in the HIV group, 7/33 were positive for IgG; and in the HIV+toxoplasmosis group, 13/56 were positive for IgG and two positive for IgM. The seropositivity for IgG was assessed by western blot by testing 43 IFA test positive samples using rNcSRS2 (Nc-p43) as antigen. The serological results of the present study suggest that exposure of these pregnant women to the parasite N. caninum and presence of IgM antibodies are indicative of recent infection. Further studies are needed to establish the possibility of active infection.

Neospora caninum: a new class of biopharmaceuticals in the therapeutic arsenal against cancer

BACKGROUND

Microorganisms that can be used for their lytic activity against tumor cells as well as inducing or reactivating antitumor immune responses are a relevant part of the available immunotherapy strategies. Viruses, bacteria and even protozoa have been largely explored with success as effective human antitumor agents. To date, only one oncolytic virus-T-VEC-has been approved by the US Food and Drug Administration for use in biological cancer therapy in clinical trials. The goal of our study is to evaluate the potential of a livestock pathogen, the protozoan Neospora caninum, non-pathogenic in humans, as an effective and safe antitumorous agent.

METHODS/RESULTS

We demonstrated that the treatment of murine thymoma EG7 by subcutaneous injection of N. caninum tachyzoites either in or remotely from the tumor strongly inhibits tumor development, and often causes their complete eradication. Analysis of immune responses showed that N. caninum had the ability to 1) lyze infected cancer cells, 2) reactivate the immunosuppressed immune cells and 3) activate the systemic immune system by generating a protective antitumor response dependent on natural killer cells, CD8-T cells and associated with a strong interferon (IFN)-γ secretion in the tumor microenvironment. Most importantly, we observed a total clearance of the injected agent in the treated animals: N. caninum exhibited strong anticancer effects without persisting in the organism of treated mice. We also established in vitro and an in vivo non-obese diabetic/severe combined immunodeficiency mouse model that N. caninum infected and induced a strong regression of human Merkel cell carcinoma. Finally, we engineered a N. caninum strain to secrete human interleukin (IL)-15, associated with the alpha-subunit of the IL-15 receptor thus strengthening the immuno-stimulatory properties of N. caninum. Indeed, this NC1-IL15hRec strain induced both proliferation of and IFN-γ secretion by human peripheral blood mononuclear cells, as well as improved efficacy in vivo in the EG7 tumor model.

CONCLUSION

These results highlight N. caninum as a potential, extremely effective and non-toxic anticancer agent, capable of being engineered to either express at its surface or to secrete biodrugs. Our work has identified the broad clinical possibilities of using N. caninum as an oncolytic protozoan in human medicine.

Toxoplasma gondii-positive human sera recognise intracellular tachyzoites and bradyzoites with diverse patterns of immunoreactivity

Antibody detection assays have long been the first line test to confirm infection with the zoonotic parasite Toxoplasma gondii. However, challenges exist with serological diagnosis, especially distinguishing between acute, latent and reactivation disease states. The sensitivity and specificity of serological tests might be improved by testing for antibodies against parasite antigens other than those typically found on the parasite surface during the acute stage. To this end, we analysed the reactivity profile of human sera, identified as positive for anti-Toxoplasma gondii IgG in traditional assays, by indirect immunofluorescence reactivity to acute stage intracellular tachyzoites and in vitro-induced latent stage bradyzoites. The majority of anti-Toxoplasma gondii IgG positive sera recognised both intracellularly replicating tachyzoites and in vitro-induced bradyzoites with varying patterns of immune-reactivity. Furthermore, anti-bradyzoite antibodies were not detected in sera that were IgM-positive/IgG-negative. These results demonstrate that anti-Toxoplasma gondii-positive sera may contain antibodies to a variety of antigens in addition to those traditionally used in serological tests, and suggest the need for further investigations into the utility of anti-bradyzoite-specific antibodies to aid in diagnosis of Toxoplasma gondii infection.

Antibodies to Neospora caninum in sheep from slaughterhouses in the state of São Paulo, Brazil

Neosporosis is an emergent disease responsible for considerable economic impact due to reproductive losses. Its zoonotic potential remains unknown. This study involved a survey of antibodies to Neospora caninum in slaughtered sheep and their association with epidemiological variables. Serum samples from 596 sheep from the states of São Paulo and Rio Grande do Sul, Brazil, were collected in two slaughterhouses located in São Paulo and evaluated by indirect fluorescence antibody test (IFAT), using cut-off titers of 25. Among these samples, 353/596 (59.23%; 95%CI 55.23-63.10) were positive and 263/353 (74.50%; 95%CI 69.71-78.77%) were from Rio Grande do Sul. Statistical associations were determined in the univariate analysis between the serological results and sex, breed and municipality of origin. Sheep that came from extensive breeding system showed higher chance (OR=2.09) of presenting antibodies to N. caninum in relation to those from semi-intensive system. Higher chance was also observed for the different studied breeds, except Bergamácia, in relation to Hampshire Down. The results revealed the presence of infection by N. caninum in sheep from slaughterhouses.

Neospora caninum and Toxoplasma gondii serodiagnosis in human immunodeficiency virus carriers

INTRODUCTION

Neospora caninum and Toxoplasma gondii belong to the Sarcocystidae family, and both have one definitive and various intermediary hosts. Owing to their weak immune systems, immunocompromised persons might be prone to opportunistic infections. The aim of this study was to investigate the presence of anti- N. caninum and anti- T. gondii antibodies in immunocompromised individuals.

METHODS

This cross-sectional study investigated the rates of N. caninum and T. gondii , as assessed using immunofluorescent antibody reaction (IFAT) with 1:50 and 1:16 dilution, respectively, in patients with human immunodeficiency virus (HIV).

RESULTS

The seropositivity for N. caninum was 26.1% (81/310) in Mato Grosso do Sul and 31.2% (10/32) in Paraná and for T. gondii was 76.8% (238/310) in Mato Grosso do Sul and 68.7% (22/32) in Paraná.

CONCLUSIONS

There is evidence of anti- N caninum and anti- T. gondii antibodies in patients with HIV. Other aspects of T. gondii , which is a zoonosis, and N. caninum , which might affect immunodeficient individuals, need to be evaluated and reported.

Differential susceptibility of human trophoblastic (BeWo) and uterine cervical (HeLa) cells to Neospora caninum infection

Neospora caninum is an apicomplexan parasite, closely related to Toxoplasma gondii, and causes abortion and congenital neosporosis in cattle worldwide. Trophoblast cells act in mechanisms of innate immune defense at the fetal-maternal interface and no data are available about the interaction of Neospora with human trophoblasts. Thus, this study aimed to verify the susceptibility of human trophoblastic (BeWo) compared with uterine cervical (HeLa) cell lines to N. caninum. BeWo and HeLa cells were infected with different parasite:cell ratios of N. caninum tachyzoites and analyzed at different times after infection for cell viability using thiazolyl blue tetrazole and lactate dehydrogenase assays. Both cell lines were also evaluated for cytokine production and parasite infection/replication assays when pre-treated or not with Neospora lysate antigen (NLA) or human recombinant IFN-γ. Cell viability was increased up to 48 h of infection in both types of cells, suggesting that infection could inhibit early cell death and/or induce cell proliferation. Neospora infection induced up-regulation of the macrophage migration inhibitory factor (MIF), mainly in HeLa cells, which was enhanced by cell pre-treatment by NLA or IFN-γ. Conversely, parasite infection induced down-regulation of the transforming growth factor (TGF-β), mostly in BeWo cells, which was decreased with NLA or IFN-γ pre-treatment. HeLa cells were more susceptible to Neospora infection than BeWo cells and IFN-γ pre-treatment resulted in reduced infection indices in both cell lines. Control of parasite growth was mediated by IFN-γ through an indoleamine-2,3-dioxygenase-dependent mechanism in HeLa cells alone. Based on these results, we concluded that BeWo and HeLa cells are readily infected by N. caninum, although presenting differences in susceptibility to infection, cytokine production and cell viability. Thus, these host cells can be considered in comparative approaches to understand strategies used by N. caninum to survive at the maternal-fetal interface.

Myeloid differentiation factor 88 is required for resistance to Neospora caninum infection

Neospora caninum is an intracellular parasite that causes major economic impact on cattle raising farms, and infects a wide range of warm-blooded hosts worldwide. Innate immune mechanisms that lead to protection against this parasite are still unknown. In order to investigate whether myeloid differentiation factor 88 (MyD88) is required for resistance against N. caninum, genetically deficient mice (MyD88^−/−) and wild type littermates were infected with live tachyzoites and the resistance to infection was evaluated. We found that sub-lethal tachyzoite doses induced acute mortality of MyD88^−/− mice, which succumbed to infection due to uncontrolled parasite replication. Higher parasitism in MyD88^−/− mice was associated with the lack of IL-12 production by dendritic cells, delayed IFN-γ responses by NKT, CD4⁺ and CD8⁺ T lymphocytes, and production of high levels of IL-10. MyD88^−/− mice replenished with IL-12 and IFN-γ abolished susceptibility as the animals survived throughout the experimental period. We conclude that protective IFN-γ-mediated immunity to N. caninum is dependent on initial MyD88 signaling, in a mechanism triggered by production of IL-12 by dendritic cells. Further knowledge on Toll-like receptor recognition of N. caninum antigens is encouraged, since it could generate new prophylactic and therapeutic tools to control parasite burden.

Lack of serologic evidence of Neospora caninum in humans, England

Retrospective testing of 3,232 serum samples from the general population and 518 serum samples from a high-risk group showed no evidence of human exposure to Neospora caninum in England. Results were obtained by using immunofluorescence antibody testing and ELISA to analyze frequency distribution.

Epidemiology and control of neosporosis and Neospora caninum

Neospora caninum is a protozoan parasite of animals. Until 1988, it was misidentified as Toxoplasma gondii. Since its first recognition in dogs in 1984 and the description of the new genus and species Neospora caninum in 1988, neosporosis has emerged as a serious disease of cattle and dogs worldwide. Abortions and neonatal mortality are a major problem in livestock operations, and neosporosis is a major cause of abortion in cattle. Although antibodies to N. caninum have been reported, the parasite has not been detected in human tissues. Thus, the zoonotic potential is uncertain. This review is focused mainly on the epidemiology and control of neosporosis in cattle, but worldwide seroprevalences of N. caninum in animals and humans are tabulated. The role of wildlife in the life cycle of N. caninum and strategies for the control of neosporosis in cattle are discussed.

Detection of immunoglobulin G antibodies to Neospora caninum in humans: high seropositivity rates in patients who are infected by human immunodeficiency virus or have neurological disorders

Considering that little is known about the epidemiology of Neospora caninum infection in humans, particularly in populations with high Toxoplasma gondii infection rates, the present study aimed to investigate the presence of antibodies to N. caninum in T. gondii-seropositive and -seronegative individuals. A total of 256 serum samples divided into four groups (61 samples from human immunodeficiency virus [HIV]-positive patients, 50 samples from patients with neurological disorders, 91 samples from newborns, and 54 samples from healthy subjects) were assessed for N. caninum and T. gondii serologies by indirect fluorescent-antibody test, enzyme-linked immunosorbent assay, and immunoblotting (IB). Immunoglobulin G antibodies to N. caninum were predominantly detected in HIV-infected patients (38%) and patients with neurological disorders (18%), while newborns and healthy subjects showed lower seropositivity rates (5% and 6%, respectively). Seropositivity to N. caninum was significantly associated with seropositivity to T. gondii in both HIV-infected patients and patients with neurological disorders. Seroreactivity to N. caninum was confirmed by IB, with positive sera predominantly recognizing the 29-kDa antigen of N. caninum. The results of this study indicate the presence of N. caninum infection or exposure in humans, particularly in HIV-infected patients or patients with neurological disorders, who could have opportunistic and concurrent infections with T. gondii. These findings may bring a new concern for the unstable clinical health of HIV-infected patients and the actual role of N. caninum infection in immunocompromised patients.

Use of a multiplex polymerase chain reaction assay in the antemortem diagnosis of toxoplasmosis and neosporosis in the central nervous system of cats and dogs

OBJECTIVE

To develop a multiplex polymerase chain reaction (PCR) assay for the detection of Toxoplasma gondii and Neospora caninum DNA in canine and feline biological samples. SAMPLE POPULATION; Biological samples from 7 cats with systemic (n = 4) or CNS (3) toxoplasmosis, 6 dogs with neospora- or toxoplasma-associated encephalitis, and 11 animals with nonprotozoal disease.

PROCEDURE

Primers for T gondii, N caninum, and the canine ferritin gene (dogs) or feline histone 3.3 gene (cats) were combined in a single PCR assay. The DNA was extracted from paraffin-embedded brain tissue, CSF, or skeletal muscle. The PCR products with positive results were cloned, and sequence identity was confirmed.

RESULTS

Of 7 cats and 4 dogs with immunohistochemical or serologic evidence of toxoplasmosis, PCR results were positive for all cats and 3 dogs for T gondii, and positive for T gondii and N caninum for 1 dog. Another dog had negative PCR results for both parasites. Of 2 dogs with immunohistochemical or serologic evidence of neosporosis, PCR results were positive for 1 for N caninum and positive for the other for T gondii. All negative-control samples yielded negative results for T gondii and N caninum on the PCR assay.

CONCLUSIONS AND CLINICAL RELEVANCE

Standard tests for toxoplasmosis or neosporosis associated with the CNS rely on serologic, histologic, or immunohistochemical analysis and can be difficult to interpret. The multiplex PCR assay with built-in control reactions could be a complementary clinical tool for the antemortem diagnosis of toxoplasmosis or neosporosis associated with the CNS.

Review of Neospora caninum and neosporosis in animals

Neospora caninum is a coccidian parasite of animals. It is a major pathogen for cattle and dogs and it occasionally causes clinical infections in horses, goats, sheep, and deer. Domestic dogs are the only known definitive hosts for N. caninum. It is one of the most efficiently transmitted parasite of cattle and up to 90% of cattle in some herds are infected. Transplacental transmission is considered the major route of transmission of N. caninum in cattle. Neospora caninum is a major cause of abortion in cattle in many countries. To elicit protective immunity against abortion in cows that already harbor a latent infection is a major problem. This paper reviews information on biology, diagnosis, epidemiology and control of neosporosis in animals.

Detection of IgG antibody against Neospora caninum in cattle in Korea

A total of 492 cattle sera was screened by IgG-ELISA against Neospora caninum (Nc-1 strain and a Korean isolate, KBA-2) and Toxoplasma gondii. Out of 492, 113 sera (23.0%) reacted positively to either Nc-1 or KBA-2 strains of N. caninum. Among the 113 positive sera, 92 sera (81.4%) reacted with antigens of both strains, but 6 sera (5.3%) with Nc-1 and 15 sera (13.3%) with KBA-2 strain only. And with T. gondii antigen, 6 sera (1.2%) were positive but all reacted with N. caninum antigen also. Western blot revealed typical binding pattern according to ELISA values, such that high OD group reacted specifically to the major surface proteins including 43 kDa protein. Seroprevalence of 23.0% indicates that neosporosis seemed to be one of major causes of abortion in cattle. It is suggested here to establish more epidemiological researches nationwide systematically.