Detection of antibodies in serum and cerebrospinal fluid to Toxoplasma gondii by indirect latex agglutination test and enzyme-linked immunosorbent assay

Comparative Detection of Immunoglobulin Isotypes and Subclasses against Toxoplasma gondii Soluble Antigen in Serum and Colostrum Samples from Puerperal Women

Background: Toxoplasma gondii is an obligate intracellular parasite that can infect several species, including humans, and can cause severe damage to the fetus when the infection occurs during pregnancy. The environment and/or food contamination are critical to spreading the infection. Human milk is rich in nutrients and bioactive elements that provide growth and development of the immune system of the newborn. All isotypes of immunoglobulins are present in human colostrum and they are produced from systemic or local sources. Breastfeeding protects the infant against various pathogens, but there is no conclusive study to detect IgG subclasses in colostrum against T. gondii. Therefore, the aim of this study was to detect and evaluate the presence of antibody isotypes against T. gondii in paired samples of serum and colostrum. Methods: The study included 283 puerperal patients. ELISA (Enzyme-Linked Immunosorbent Assay) for detection of anti-T. gondii-specific IgM, IgA, and IgG isotypes and IgG1, IgG3, and IgG4 subclasses were conducted on paired samples of serum and colostrum. Results: It was found that 45.9%, 6.0%, and 2.1% of serum samples and 45.2%, 7.1%, and 2.1% of colostrum samples were positive for IgG, IgM, and IgA, respectively. Specific IgG1, IgG3, and IgG4 were positive, respectively, in 98.5%, 54.6%, and 44.6% of serum samples, in contrast with 56.9%, 78.5%, and 34.6% of colostrum samples. Thus, the predominant reactivity of IgG subclasses against T. gondii was IgG1 in serum and IgG3 in colostrum. The higher percentage of positive samples and higher levels of anti-T. gondii IgG3 antibodies were observed in colostrum, when compared to serum samples, suggesting a local production of this subclass. IgG3 and IgG1 subclasses presented different percentages of positivity in serum and colostrum. Only the IgG1 subclass showed a significant correlation between the levels of anti-T. gondii in serum and colostrum, suggesting that IgG1 in breast milk comes from a systemic source. IgG4 showed a similar percentage of positivity in both sample types, but no significant correlation was observed between their levels. Conclusion: Colostrum presents representative levels of IgM, IgA, IgG1, IgG3, and IgG4 antibodies specific to T. gondii. The detection of these antibodies presents the potential for diagnostic application of colostrum samples to better identify the diagnostic status of T. gondii infection, especially during the acute phase. In addition, breastfeeding can also be a possible source of protective antibodies for the newborn against toxoplasmosis, an anthropozoonosis maintained by environmental infection, which interferes in the public health of many countries.

Seroprevalence of Toxoplasma gondii assayed using Rapid Diagnostic Tests among Residents in Three Counties Adjacent to The Demilitarized Zone, Korea

Toxoplasma gondii seroprevalence have been rapidly increasing in some parts of Korea. We analyzed prevalence of anti-Toxoplasma gondii antibodies, using a rapid diagnostic test (RDT), in the sera of 552 residents in Ganghwa-gun, 661 ones in Cheorwon-gun, and 305 ones in Goseong-gun, Korea in 2019. IgG/IgM RDT mounted with recombinant fragment of major surface antigen (SAG1), glutathione-S-transferase-linker-SAG1A, were applied to the sera. IgG seroprevalence was 28.1% in Ganghwa-gun, 19.5% in Cheorwon-gun and 35.7% in Goseong-gun. Odds ratios comparing Cheorwon vs Ganghwa was 0.63 (P=0.001) and Goesong versus Ganghwa was 1.47 (P=0.01) adjusting age and sex. Goseong had highest seroprevalence among the 3 counties both in crude rates and logistic regression. Although Cheorwon and Goseong are adjacent to the demilitarized zone (DMZ) in Korea, seroprevalence rate was much higher in Goseong. Further investigation on other DMZ-closed areas is necessary whether they have high prevalence rates compared to the other areas. T. gondii prevalence in Korea is still persists; proper health policy should be established.

Seroprevalence and B1 gene Phylogeny of Toxoplasma gondii of Dogs and Cats in Republic of Korea

The outbreak of human toxoplasmosis can be attributed to ingestion of food contaminated with Toxoplasma gondii. Toxoplasmosis recently increased in domestic and stray dogs and cats. It prompted studies on the zoonotic infectious diseases transmitted via these animals. Sero- and antigen prevalences of T. gondii in dogs and cats were surveyed using ELISA and PCR, and B1 gene phylogeny was analyzed in this study. Toxoplasmosis antibodies were measured on sera of 403 stray cats, 947 stray dogs, 909 domestic cats, and 2,412 domestic dogs collected at nationwide regions, Korea from 2017 to 2019. In addition, whole blood, feces, and tissue samples were also collected from stray cats (1,392), stray dogs (686), domestic cats (3,040), and domestic dogs (1,974), and T. gondii-specific B1 gene PCR was performed. Antibody prevalence of stray cats, stray dogs, domestic cats, and domestic dogs were 14.1%, 5.6%, 2.3%, and 0.04%, respectively. Antigen prevalence of these animals was 0.5%, 0.2%, 0.1%, and 0.4%, respectively. Stray cats revealed the highest infection rate of toxoplasmosis, followed by stray dogs, domestic cats, and domestic dogs. B1 gene positives were 5 of stray cats, and identified to high/moderate pathogenic Type I/III group. These findings enforce that preventive hygienic measure should be strengthened at One Health level in dogs and cats, domestic and stray, to minimize human toxoplasmosis infections.

Excretion of Toxoplasma gondii oocysts from Feral Cats in Korea

Sporulated oocysts from the feces of infected cats with Toxoplasma gondii can cause detrimental disease in both humans and animals. To investigate the prevalence of feral cats that excrete T. gondii oocysts in the feces, we examined fecal samples of 563 feral cats over a 3-year period from 2009 to 2011. Oocysts of T. gondii excreted into the feces were found from 4 of 128 cats in 2009 (3.1%) and one of 228 (0.4%) in 2010 while none of the 207 cats in 2010 were found positive with oocysts in their feces, resulting in an overall prevalence rate of 0.89% (5/563) between 2009 and 2011. Among the 5 cats that tested positive with T. gondii oocysts, 4 of the cats were male and 1 was a female with an average body weight of 0.87 kg. Numerous tissue cysts of 60 μm in diameter with thin (<0.5 μm) cyst walls were found in the brain of one of the 5 cats on necropsy 2 months after the identification of oocysts in the feces. A PCR amplification of the T. gondii-like oocysts in the feces of the positive cats using the primer pairs Tox-5/Tox-8 and Hham34F/Hham3R confirmed the presence of T. gondii oocysts in the feces. This study provides a good indication of the risk assessment of feral cats in the transmission of T. gondii to humans in Korea.

Tissue Fluid Enzyme-Linked Immunosorbant Assay for Piglets Experimentally Infected with Toxoplasma gondii and Survey on Local and Imported Pork in Korean Retail Meat Markets

To investigate the prevalence of Toxoplasma gondii in pork on the market in Korea, an in-house enzyme-linked immunosorbent assay for tissue fluid (CAU-tf-ELISA) was developed using a soluble extract of T. gondii RH strain tachyzoites. As the standard positive controls, the piglets were experimentally infected with T. gondii: Group A (1,000 cysts-containing bradyzoites), Group B (500 cysts-containing bradyzoites) and Group C (1.0×103 or 1.0×104 tachyzoites). The CAU-tf-ELISA demonstrated infection intensity-dependent positivity toward tissue fluids with average cut-off value 0.15: 100% for Group A, 93.8% for Group B and 40.6% for Group C. When tissue-specific cut-off values 0.066-0.199 were applied, CAU-tf-ELISA showed 96.7% sensitivity, 100% specificity, 100% positive and 90.0% negative predictive values. When compared with the same tissue fluids, performance of CAU-tf-ELISA was better than that of a commercial ELISA kit. Of the 583 Korea domestic pork samples tested, anti-T. gondii antibodies were detected from 9.1% of whole samples and 37.9% from skirt meat highest among pork parts. In the 386 imported frozen pork samples, 1.8% (skirt meat and shoulder blade) were positive for anti-T. gondii antibodies. In Korea, prevalence of anti-T. gondii antibodies in the pork on retail markets appeared high, suggesting that regulations on pig farming and facilities are necessary to supply safe pork on the tables.

Seroprevalence of Toxoplasmosis Detected by RDT in Residents near the DMZ (demilitarized zone) of Cheorwon-gun, Gangwon-do, Korea

Seroprevalence of Toxoplasma gondii infection among the residents of Cheorwon-gun, Gangwon-do, Korea, which partly includes the demilitarized zone (DMZ), were surveyed for 4 years and evaluated by RDT using recombinant fragment of major surface antigen (SAG1A). Sera from 1336, 583, 526, and 583 adult residents were collected on a yearly basis from 2010 to 2013, respectively. The total positive seroprevalence was 19.3, 21.9, 23.4, and 26.8% from 2010 to 2013, respectively. The positive seroprevalence in men (23.6, 27.5, 29.5, 34.6%) was far higher than women (14.1, 18.3, 19.4, 21.4%), from 2010 to 2013, respectively. This high seroprevalence of toxoplasmosis in Cheorwon-gun may have been influenced in part by its geographical locality of the area as it includes the DMZ, where civilian access is strictly limited, thus creating a relatively isolated area that is a well-preserved habitat. Further research is necessary to study the epidemiology of toxoplasmosis in this area.

Seroprevalence of Toxoplasmosis with ELISA and Rapid Diagnostic Test among Residents in Gyodong-do, Inchon city, Korea: A Four-Year Follow-up

ELISA has been used for the diagnosis of toxoplasmosis, but it is being gradually replaced by a rapid diagnostic test (RDT). We compared and analyzed ELISA and RDT results using the sera collected during 4 consecutive years from residents of Gyodong-do (Island), Incheon-city, Korea. Sera from 921, 993, 940, and 838 adult residents were collected on a yearly basis (2010-2013). ELISA was performed by using a crude extract of T. gondii RH strain antigen and IgG/IgM RDT mounted with recombinant fragment of major surface antigen (SAG1), GST-linker-SAG1A, were applied to the sera. Comparison between groups was analyzed by the Student's t-test. The positive seroprevalence surged from 14.7% (135/921, 2010), 23.1% (231/993, 2011), 23.6% (222/940, 2012), and 32.1% (269/838, 2013) by ELISA. In contrast, RDT showed a more moderate increasing trend from 21.7% (200/921, 2010), 25.5% (253/993, 2011), 28.9% (272/940, 2012) and 33.1% (277/838, 2013). Discrepancies between ELISA and RDT were noted near the cut-off value. At the OD 0.15-0.24 range, RDT could detect 16.1% (169/1051) more positives, which suggests an early or acute toxoplasmosis, but at the OD 0.25-0.34 range, ELISA could detect 35.9% (92/256) more positives of possible chronic infections. Over the OD > 0.35 ELISA and RDT agreed in the majority of the cases. This surge in seroprevalence may be caused by the organic agriculture in addition to eating behavior or increase in pets among Koreans. These facts may be applied on a full-scale national survey using RDT to supplement ELISA to define the characteristics of the infection.

High Seroprevalence of Toxoplasmosis Detected by RDT among the Residents of Seokmo-do (Island) in Ganghwa-Gun, Incheon City, Korea

Seroprevalence of Toxoplasma gondii infection among the residents of Seokmo-do (Island) in Ganghwa-gun, Incheon, Korea was surveyed for 4 years by a rapid diagnostic test (RDT) using recombinant fragment of major surface antigen (SAG1), GST-linker-SAG1A. Sera from 312, 343, 390, and 362 adult residents were collected on a yearly basis from 2010 to 2013, respectively. Total positive seroprevalence regardless of gender was 29.2, 35.3, 38.7, and 45.3% from 2010 to 2013, respectively. Positive seroprevalence in male adults was 43.9, 48.2, 45.4, and 55.3%, which was far higher than that of the corresponding female adults which was 20.7, 29.2, 33.9, and 38.9%, from 2010 to 2013, respectively. This high seroprevalence of toxoplasmosis in Seokmo-do may have been caused in part by peculiar changes in the toxoplasmic environment of the island as it is a relatively isolated area preserving its natural habitat while also being connected by a bridge to the mainland. Further study is necessary to find out symptomatic patients and to confirm the risk factors.

Prevalence of Toxoplasma gondii infection in household and feral cats in Korea

This study was designed to investigate the prevalence rate of Toxoplasma gondii (T. gondii) infection in household cats in Korea. One hundred household cats and 50 feral cats from nine of the largest cities in Korea were enrolled in this study. The tests performed in this survey was an in-house rapid screen IgG and IgM combo test, faecal PCR test for T. gondii oocysts, and an ELISA immunoassay for IgG antibodies. There were no household cats positive for T. gondii infection detected using the in-house IgG and IgM rapid screen combo test, although 6/50 and 0/50 feral cats were positive in IgG and IgM tests, respectively. This initial finding was confirmed by subsequent ELISA test for IgG antibody and PCR for T. gondii in faeces. Despite the higher prevalence rate of the disease in feral cats in Korea, we did not find any household cats that were either infected or exposed previously to T. gondii in our study population. Our study indicates that there is minimal risk of T. gondii transmission from household cats to human in Korea.

Evaluation of colostrum as an alternative biological sample for the diagnosis of human congenital toxoplasmosis

Background

Toxoplasmosis is a zoonosis caused by Toxoplasma gondii, an intracellular protozoan parasite able to infect a wide range of hosts, including humans. Congenital infection can cause severe damage to the fetus. Thus, it is important to detect antibodies against the parasite to confirm clinical manifestations. Considering that all immunoglobulin isotypes may be present in biological samples from newborns and their mothers, this study aimed to evaluate the ability to diagnose recent toxoplasmosis by using colostrum, as an alternative noninvasive way to obtain biological samples, as well as to determine correlation rates between antibodies from serum samples to detect IgG, IgM and IgA isotypes against T. gondii.

Methods

A total of 289 puerperal women from Clinical Hospital of Federal University of Uberlândia (mean age: 24.8 years, range: 14 – 43 years) took part in this study. Serum and colostrum samples from these patients were analyzed using ELISA and immunoblotting assays for soluble antigens from T. gondii.

Results

ELISA immunoassays with serum samples showed reactivity in 47.0, 6.9 and 2.8 % of samples to anti-T. gondii IgG, IgM and IgA, respectively, in comparison with colostrum samples, which showed reactivity in 46.0, 7.9 and 2.8 % of samples to the same isotypes. Also, significant correlation rates of anti-T. gondii antibody levels between serum and colostrum samples were observed. Interestingly, reactivity to IgM and/or IgA in colostrum and/or serum confirmed clinical manifestations of congenital toxoplasmosis in three newborns. Immunoblotting assays showed that it is possible to detect IgG, IgM and IgA antibodies against various antigens of T. gondii in serum and colostrum samples. IgG antibodies in serum and colostrum samples recognized more antigenic fractions than IgM and IgA antibodies. Serum IgG detected more antigenic fractions than IgG antibodies present in the colostrum of the same patient. In contrast, specific IgA present in colostrum recognized a higher number of antigens than IgA present in serum samples of the same patient.

Conclusions

Overall, the results show that it is important to investigate the occurrence of congenital toxoplasmosis, even at puerperal period. Furthermore, this study demonstrates that T. gondii-specific IgG, IgM and IgA antibodies in serum and colostrum samples from puerperal women may be detected with a significant correlation, suggesting that colostrum may also be used as an alternative biological sample to efficiently diagnose recent human toxoplasmosis.

Mesial Temporal Lobe Epilepsy in Congenital Toxoplasmosis: A Case Report

Toxoplasmosis is a rare disease caused by intracellular protozoan parasite, Toxoplasma gondii. Though most patients with toxoplasmosis are asymptomatic, congenital toxoplasmosis in the fetus can cause ocular involvement such as chorioretinitis and central nervous system disease including intracerebral calcification, nystagmus, hydrocephalus and microcephaly. Also, these brain lesions can cause seizure secondarily. Our patient was diagnosed with congenital toxoplasmosis, based on toxoplasma-specific serologic test with typical clinical symptoms, including chorioretinitis, nystagmus, hydrocephalus and cerebral palsy. Her brain imaging findings revealed not only the multifocal encephalomalacia, but also multifocal cerebral calcification including intracerebral calcification in left perihippocampal region. Her epileptogenic zone was defined as mesial temporal lobe including hippocampus on left side by seizure semiology, electroencephalogram and neuroimaging including single photon emission computed tomography and 18F-Fluorodeoxyglucose positron-emission tomography. Her seizures were refractory to multiple anti-epileptic drugs. We report a patient with congenital toxoplasmosis who showed intractable mesial temporal lobe epilepsy.

Prevalence of Toxoplasma gondii infection in household cats in Korea and risk factors

Several epidemiological surveys have reported the prevalence of Toxoplasma gondii infection in stray cats in Korea, but little information is available on T. gondii infection in household cats. The aim of the present study was to assess the prevalence and risk factors of T. gondii infection among household cats reared in Seoul, Korea. A total of 474 blood samples were collected from clinically healthy household cats. All samples were tested using ELISA and PCR. The risk factor analysis was based on a questionnaire filled out by the owners. The overall positive rate for ELISA and PCR assays was 2.2% (10/437) and 2.1% (10/474), respectively. With regard to the origin of cats, the positive rates among cats adopted from the animal shelter and veterinary clinic for stray cats were significantly different (P<0.05). Our study demonstrated that the positive rate of T. gondii infection in household cats was low and that this low prevalence was assumed to be associated with keeping the cats indoors and restriction of eating raw food and uncooked meat. Therefore, we suggest that the owners check the origin of the cats prior to adoption to prevent infection of other animals, including humans.

Serologic survey of toxoplasmosis in Seoul and Jeju-do, and a brief review of its seroprevalence in Korea

Knowledge of the prevalence of human Toxoplasma gondii infection is required in the Republic of Korea. In this study, we surveyed the seroprevalence of T. gondii infection and analyzed the risk factors associated with seropositivity among residents in 2 administrative districts; Seoul and the island of Jeju-do, which have contrasting epidemiologic characteristics. Sera and blood collected from 2,150 residents (1,114 in Seoul and 1,036 in Jeju-do) were checked for IgG antibody titers using ELISA and for the T. gondii B1 gene using PCR. In addition, participants completed a questionnaire that solicited information on gender, age, occupation, eating habits, history of contact with animals, and travel abroad. The T. gondii B1 gene was not detected in all residents examined. However, ELISA showed 8.0% (89 of 1,114 sera) positive for IgG antibodies against T. gondii in Seoul and 11.3% (117 of 1,036 sera) in Jeju-do. In both districts, the positive rates were higher in males than in females, and those 40-79 years of age showed higher rates than other ages. In Seoul, residents older than 70 years of age showed the highest positive rate, 14.9%, whereas in Jeju-do the highest prevalence, 15.6%, was in those in their sixties. The higher seropositive rate in Jeju-do than in Seoul may be related to eating habits and occupations. The present results and a review of related literature are indicative of an increased seroprevalence of T. gondii in Korea in recent years.

Seroprevalence of toxoplasmosis in the residents of Cheorwon-gun, Gangwon-do, Korea

The seroepidemiological status of toxoplasmosis was surveyed among the residents of Cheorwon-gun, Gangwon-do by means of ELISA using a crude extract antigen of Toxoplasma gondii. The sera of 1,661 adult residents (866 males and 795 females) were collected and checked for IgG antibody titers, which showed 17.0% positive rate (282 sera). The positive rate was significantly different between the sex; 20.6% for males and 13.1% for females (P<0.05). The positive rates were higher in fifties of males (28.7%) and forties of females (20.0%). This positive rate of toxoplasmosis in Cheorwon-gun residents is regarded as the highest among the surveys of different geographical regions of Korea. This high positive rate may due in part to peculiar geographical locality of the surveyed area near the naturally well preserved demilitarized zone (DMZ) or presumably consumption of the pork imported from high endemic nations. Therefore, it is necessary to study further the epidemiology of toxoplasmosis in Cheorwon-gun.

A surge in the seroprevalence of toxoplasmosis among the residents of islands in Gangwha-gun, Incheon, Korea

Seroepidemiological changes of Toxoplasma gondii infection among the residents of the islands of Gangwha-gun, Incheon for 2 years were surveyed and evaluated by ELISA using a crude extract antigen. In 2010, sera of 919 adult residents in Gyodong-myeon and 313 adults in Samsan-myeon were collected and checked for IgG antibody titers, which showed 14.5% (133 sera) and 19.8% (62 sera) positive rates, respectively. In 2011, sera of 955 adults in Gyodong-myeon and 341 adults in Samsan-myeon were examined, which showed an increase of positive rates to 23.8% (227 sera) and 31.7% (108 sera), respectively. Totally, the seroprevalence of the first year was 15.8% and it increased rapidly to 25.8% in the second year. The positive rates of both sexes increased simultaneously with the significant ratio of males to females by 1.7-2.2 fold (P<0.05). In both myeons, 661 sera were collected every year and showed changes in optical density (OD) in 177 sera; newly found as positives in 73 persons (11.0%), negative conversion in 10 persons (1.5%), and maintained or increased in 94 persons (14.2%). This rapid increase in the prevalence of toxoplasmosis in Gangwha islands may be due to in part peculiar changes in the toxoplasmic environment of the islands and presumably the consumption of the pork bred domestically within the islands or imported from high endemic nations. It is necessary to find out symptomatic toxoplasmic patients and confirm the risk factors for further infection in the islands of Gangwha-gun.

Toxoplasmic pachymeningitis with visual field impairment in a single-eyed patient and a literature review

To describe the clinical features of a patient with toxoplasmic pachymeningitis and provide a review of the recent cases of pachymeningitis in the literature.Retrospective, observational case report. A one-eyed patient who presented to our institution with blurred vision, floaters, and visual field shrinkage. Review of clinical, laboratory, perimetric, and radiologic records of the patient and description of the efficacy of antibiotic therapy. The signs of ocular impairment, including visual acuity, visual field, and magnetic resonance imaging (MRI) changes. A one-eyed patient who complained of blurred vision and unexplained visual field shrinkage was evaluated. The diagnosis of toxoplasmic pachymeningitis was confirmed by existence of a toxoplasmic seroconversion, cerebrospinal fluid abnormalities, radiological features, absence of other diagnoses, improvement of symptoms, and resolution of pachymeningitis in MRI with oral trimethoprim-sulfamethoxazole combination.Pachymeningitis is a rare disease and toxoplasmic pachymeningitis has never been described. Among the various infectious causes, screening for toxoplasmosis must be performed because it can lead to pachymeningitis and sequelae. Variable features may lead to misdiagnosis and delay in the treatment of this sight-threatening and potentially fatal disease.

Maintained seroprevalence of toxoplasmosis among the residents of Jeju island, Korea

Seroepidemiological status of toxoplasmosis among the residents of Jeju island was surveyed and evaluated by ELISA with crude extract of Toxoplasma gondii. The sera of 2,348 residents (male 1,157 and female 1,191) were collected and checked for the IgG antibody titers, which showed 13.2% positive rate (309 sera). The positive rates were increasing gradually according to the age from 4.3% in teenage to 20.6% in seventies. The positive rates were significantly different between the sex by 16.2% for male and 10.2% for female (P<0.05). This positive rate of toxoplasmosis in Jeju island residents is regarded relatively higher than any other regions of Korea. And the high positive rate may be maintained continuously among Jeju island residents without any clear reasons until now but due to some parts peculiar socio-cultural tradition of Jeju island. Therefore, it is necessary to study further the epidemiology of toxoplasmosis of Jeju island.

Development and clinical evaluation of a rapid serodiagnostic test for toxoplasmosis of cats using recombinant SAG1 antigen

Rapid serodiagnostic methods for Toxoplasma gondii infection in cats are urgently needed for effective control of transmission routes toward human infections. In this work, 4 recombinant T. gondii antigens (SAG1, SAG2, GRA3, and GRA6) were produced and tested for the development of rapid diagnostic test (RDT). The proteins were expressed in Escherichia coli, affinity-purified, and applied onto the nitrocellulose membrane of the test strip. The recombinant SAG1 (rSAG1) showed the strongest antigenic activity and highest specificity among them. We also performed clinical evaluation of the rSAG1-loaded RDT in 182 cat sera (55 household and 127 stray cats). The kit showed 0.88 of kappa value comparing with a commercialized ELISA kit, which indicated a significant correlation between rSAG1-loaded RDT and the ELISA kit. The overall sensitivity and specificity of the RDT were 100% (23/23) and 99.4% (158/159), respectively. The rSAG1-loaded RDT is rapid, easy to use, and highly accurate. Thus, it would be a suitable diagnostic tool for rapid detection of antibodies in T. gondii-infected cats under field conditions.

Clinical features of ocular toxoplasmosis in Korean patients

We report here the records of 10 consecutive Korean patients (10 eyes) with ocular toxoplasmosis which showed the typical clinical manifestations with seropositivity for Toxoplasma gondii specific IgG antibodies by micro-ELISA between 2006 and 2010. Nine patients were males and 1 was female; their age was 50.5 ± 13.8 years. The most common accompanying signs were vitritis (100%), anterior uveitis (70%), and scattered white deposit (80%). Pre-existing retinochoroidal scar was found in 1 (10%) patient. All patients received antiparasitic chemotherapy and systemic corticosteroid treatment, which resolved the presenting attack and recovered the visual acuity better than initial one in 9 patients and worse in 1. Optic atrophy, cataract, and retinal neovascularization were observed during the follow-up period and recurrence was detected in 3 eyes (30%) 6 to 20 months after the initial attack. In Korea, although rarely detected and reported, ocular toxoplasmosis needs more attention in clinical field of retinal diseases.

Suppression of CD4 T-Cells in the spleen of mice infected with Toxoplasma gondii KI-1 tachyzoites

Toxoplasma gondii KI-1, a recent new isolate from Korea, shows similar pathogenicity and infectivity to mice compared to the virulent RH strain. To understand characteristics of host immunity, including immune enhancement or suppression, we investigated proliferative responses and phenotypes of spleen cells. In addition, kinetics of IFN-γ, a Th1 cytokine, was examined in BALB/c mice up to day 6 post-infection (PI). Intraperitoneal injection of mice with 10³ KI-1 tachyzoites induced significant decreases (P < 0.05) in proliferative responses of spleen cells. This occurred at days 2-6 PI even when concanavalin A (con A) was added and when stimulated with KI-1 antigen, suggesting suppression of the immunity. CD4⁺ T-cells decreased markedly at day 2 PI (P < 0.05), whereas CD8⁺ T-cells, NK cells, and macrophages did not show significant changes, except a slight, but significant, increase of CD8⁺ T-cells at day 6 PI. The capacity of splenocytes to produce IFN-γ by con A stimulation dropped significantly at days 2-6 PI. These results demonstrate that intraperitoneal injection of KI-1 tachyzoites can induce immunosuppression during the early stage of infection, as revealed by the decrease of CD4⁺ T-cells and IFN-γ.

Prevalence of Toxoplasma gondii infection in stray and household cats in regions of Seoul, Korea

The principal objective of this study was to investigate the prevalence of toxoplasmosis in household and stray cats in Seoul, Republic of Korea. We collected blood samples from 72 stray and 80 household cats, and all samples were examined by ELISA and nested PCR. The overall positive rates of Toxoplasma gondii in stray cats were 38.9% (28/72), with 15.3% (11/72) in ELISA and 30.6% (22/72) in PCR. The positive rate in male stray cats was slightly higher than that of female stray cats. The highest positive rate of T. gondii infection was noted in Gangnam and Songpa populations in ELISA and in Gwangjin population in PCR. In household cats, however, we could not detect any specific antibodies or DNA for T. gondii. In conclusion, we recognized that the infection rate of toxoplasmosis in stray cats in Seoul was considerably high but household cats were free from infection.

Prevalence of Toxoplasma gondii infection in feral cats in Seoul, Korea

The present study assessed the prevalence of Toxoplasma gondii infection in feral cat populations in Seoul using enzyme-linked immunosorbent assay (ELISA) and nested polymerase chain reaction (PCR). A total of 456 feral cats from 17 wards in Seoul was surveyed. The overall prevalence of T. gondii infection was 15.8% (69/456) by ELISA and 17.5% (80/456) by PCR; by gender, 17% (44/259) by ELISA and 16.2% (42/259) by PCR in males and 14.3% (28/196) by ELISA and 19.4% (38/196) by PCR in females. On a baseline of the Han River, prevalence was 15.1% (29/192) by ELISA and 15.6% (30/192) by PCR in the upper region and 16.4% (43/264) by ELISA and 18.9% (50/264) by PCR in the lower area. This suggested that toxoplasmosis is widespread throughout Seoul's feral cat population and it is critical that the city institute policies for the control of the feral cat population to reduce the risk of toxoplasmosis transmission to animals, including humans.

Review of zoonotic parasites in medical and veterinary fields in the Republic of Korea

Zoonotic parasites are animal parasites that can infect humans. The major zoonotic protozoa in the Republic of Korea are Babesia bovis, Chilomastix mesnili, Cryptosporidium parvum, Endolimax nana, Entamoeba coli, Entamoeba hitolytica, Giardia lamblia, Iodamoeba bütschlii, Pneumocystis carinii, Sarcocystis cruzi, and Toxoplasma gondii. The major zoonotic helminths in Korea include trematodes, cestodes, and nematodes. Trematodes are Clonorchis sinensis, Echinostoma hortense, Echinostoma spp., Fasciola hepatica, Heterophyes nocens, Metagonimus yokogawai, and Paragonimus westermani. Cestodes are Diphyllobothrium latum, Dipylidium caninum, Echinococcus granulosus, Hymenolepis nana, Raillietina tetragona, sparganum (Spirometra spp.), Taenia saginata, T. solium, and T. asiatica. Nematodes are Ancylostoma caninum, Brugia malayi, Capillaria hepatica, Dirofilaria immitis, Gnathostoma dololesi, Gnathostoma spinigerum, Loa loa, Onchocerca gibsoni, Strongyloides stercoralis, Thelazia callipaeda, Trichinella spiralis, Trichostrongylus orientalis, Trichuris trichiura, and Trichuris vulpis. The one arthropod is Sarcoptes scabiei. Many of these parasites have disappeared or were in decline after the 1990's. Since the late 1990's, the important zoonotic protozoa have been C. parvum, E. nana, E. coli, E. hitolytica, G. lamblia, I. buetschlii, P. carinii and T. gondii. The important zoonotic helminths have been C. sinensis, H. nocens, M. yokogawai, P. westermani, D. latum, T. asiatica, sparganum, B. malayi, T. orientalis, T. callipaeda and T. spiralis. However, outbreaks of these parasites are only in a few endemic areas. The outbreaks of Enterobius vermicularis and head lice, human parasites, have recently increased in the kindergartens and primary schools in the Republic of Korea.

Seroprevalence of Toxoplasma gondii infection and characteristics of seropositive patients in general hospitals in Daejeon, Korea

To figure out the epidemiological status and relevance with other diseases in toxoplasmosis, we checked serum IgG antibody titers of 1,265 patients and medical records of seropositive patients. Seropositive rates were 6.6% by latex agglutination test (LAT) and 6.7% by ELISA. No significant differences were detected between sexes and age groups. The peak seroprevalence was detected in the 40-49-year-old age group. According to clinical department, Toxoplasma-positive rates were high in patients in psychiatry, ophthalmology, health management, emergency medicine, and thoracic surgery. Major coincidental diseases in seropositive cases were malignant neoplasms, diabetes mellitus, arthritis, chronic hepatitis B, chronic renal diseases, schizophrenia, and acute lymphadenitis, in the order of frequency. In particular, some patients with chronic hepatitis B and malignant neoplasms had high antibody titers. These results revealed that the seroprevalence of toxoplasmosis in a general hospital-based study was similar to that in a community-based study, and T. gondii seropositivity may be associated with neoplasms, diabetes, and other chronic infections.

Prevalence of Toxoplasma gondii in stray cats of Gyeonggi-do, Korea

Toxoplasma gondii is an obligate intracellular zoonotic protozoan with a worldwide distribution. It infects humans as well as a broad spectrum of vertebrate hosts. Cats and wild felidae play crucial roles in the epidemiology of toxoplasmosis. This study was performed to survey the prevalence of T. gondii infection among stray cats in the Gyeonggi-do, Republic of Korea. A total of 174 stray cat blood samples were collected from Gwacheon-si (n=20), Bucheon-si (82), and Yangju-si (72). Positive sera for T. gondii were identified in 14 samples (8.1%) exclusively via the latex agglutination test, 28 (16.1%) via ELISA, and 23 (13.2%) via PCR analysis. The overall infection rate of female stray cats (29.2%) presented as higher than that of male cats (24.0%). This study suggests that T. gondii is widespread in the stray cat population of Gyeonggi-do, Korea. It is urgently needed to control urban stray cat population and to reduce the risk of zoonotic transmission of toxoplasmosis to other animal hosts and humans.

Evaluation of the Korean isolate-1 tachyzoite antigen for serodiagnosis of toxoplasmosis

To evaluate the usefulness of the Korean Isolate-1 (KI-1) antigen for serodiagnosis of toxoplasmosis, antigen profiles of KI-1 tachyzoites were analyzed in comparison with RH tachyzoites by SDS-PAGE and immunoblotting. ELISA was performed on latex agglutination (LA)-positive and negative serum samples using KI-1 and RH antigens. Immunoblotting of the KI-1 antigen showed multiple antigen bands with molecular sizes of 22-105 kDa. Among them, 1 and 6 common bands were noted against a KI-1-infected and a RH-infected human serum, respectively, which represented differences in antigenic profiles between KI-1 and RH tachyzoites. However, all 9 LA-positive human sera were found positive by ELISA, and all 12 LA-negative sera were negative by ELISA; the correlation between the ELISA titers and LA titers was high (r = 0.749). Our results suggest that tachyzoites of KI-1 may be useful for serodiagnosis of human toxoplasmosis.

Seroprevalence of toxoplasmosis in Korean pregnant women

This study was performed in order to evaluate the sero-epidemiological status of toxoplasmosis in pregnant Korean women. Among 5,175 sera and 750 amniotic fluid samples obtained from pregnant women, 41 serum samples (0.79%) and 10 (1.33%) amniotic fluid samples tested positive for IgG antibodies by ELISA. Fifty one cases showing a score more than 0.25 on ELISA were tested for PCR reaction against the SAG1 gene. Only one case of the 51 ELISA positive cases exhibited a positive reaction on all tests. This case had a history of acute nephropyelitis during early pregnancy, but fortunately, had delivered a phenotypically healthy baby. In this study, the seroprevalence of toxoplasmosis in pregnant women was found to be comparatively low, consistent with previous reports from Korea. However our trials, performed with a variety of diagnostic tools, were considered to be useful for the precise diagnosis of congenital toxoplasmosis.

ELISA detection of vivax malaria with recombinant multiple stage-specific antigens and its application to survey of residents in endemic areas

An ELISA was developed for the diagnosis of vivax malaria using multiple stage-specific recombinant antigens of Plasmodium vivax. The DNA from the whole blood of a malaria patient was used as template to amplify the coding regions for the antigenic domains of circumsporozoite protein (CSP-1), merozoite surface protein (MSP-1), apical merozoite antigen (AMA-1), serine repeat antigen (SERA), and exported antigen (EXP-1). Each amplified DNA fragment was inserted into pQE30 plasmid to induce the expression of His-tagged protein in Escherichia coli (M15 strain) by IPTG. His-tagged proteins were purified by Ni-NTA metal-affinity chromatography and used as antigens for ELISA with patient sera that were confirmed previously by blood smear examinations. When applied to patient sera, 122 (80.3%) out of 152 vivax malaria cases reacted to at least one antigen, while no reactions were observed with 128 uninfected serum samples. We applied this ELISA to the screening of 3,262 civilian residents in endemic regions near the DMZ, which resulted in 236 positively detected (7.2%) cases. This method can be applied to serological diagnosis and mass screening in endemic regions, or can be used as a safety test for transfusion blood in endemic areas.

Laboratory passage and characterization of an isolate of Toxoplasma gondii from an ocular patient in Korea

Toxoplasma gondii tachyzoites were isolated from the blood of an ocular patient, and have been successfully passaged in the laboratory, for over a year, by peritoneal inoculation in mice. The isolated parasite was designated the Korean Isolate-1 (KI-1) and its characteristics were compared with those of the RH strain, a wellknown virulent strain originating from a child who suffered from encephalitis. The morphology, pathogenicity, infectivity and cell culture characteristics of the KI-1 were similar to those of the RH strain. Both RH and KI-1 antigens were detected by an anti-T. gondii monoclonal antibody (mAb), Tg563, against the major surface protein SAG1 (30 kDa), whereas no reaction was observed against an anti-Neospora caninum mAb, 12B4. The KI-1 was confirmed as an isolate of T. gondii. A long-term laboratory maintenance and characterization of a local T. gondii isolate is reported for the first time in the Republic of Korea.

Seroepidemiological study of Toxoplasma gondii infection in the rural area Okcheon-gun, Korea

There have been some reports about the prevalence of anti-Toxoplasma gondii antibody among Koreans, and most of all data were taken from patients visiting hospitals. However, the epidemiological data of the community-based study in Korea are rare. This study was performed to evaluate the seroprevalence of toxoplasmosis among the inhabitants of the rural area Okcheon-gun, Korea. A total of 1,109 serum samples (499 males, 610 females) were examined for the IgG antibodies by ELISA. To set up the cut-off point for ELISA, we used a commercial latex agglutination (LA) kit. The sensitivity and specificity of ELISA against LA test were 89.5%, and 98.6% respectively. Among 1,109 sera, 6.9% showed seropositivity by ELISA. The positive rates of males and females were 6.0% and 7.2%, respectively. However, there were no significant differences between sexes. Comparing the age groups, the highest seropositive rate showed in the seventies or higher, and their rates had a tendency to increase with age (0.05 < p < 0.3). These results revealed that the seroprevalence of toxoplasmosis in rural inhabitants is similar to previous reports in Korea; however we need further investigation to clarify the prevalence of toxoplasmosis in the general population.

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.

Seroprevalence of toxoplasmosis in the residents of Cheju island, Korea

This study was performed to evaluate the epidemiological status of toxoplasmosis among the residents of Cheju island. The sera of local students from 18 high schools (boys 2110, girls 2460) and those of adults (474 admitted to Cheju Chungang General Hospital) were collected and checked for the IgG antibody titers against Toxoplasma gondii. Serum samples collected from both the students and adults showed sero-positive rate of 5.5% and 12.9%, respectively. Although the rates were not significantly different between the sexes (5.4% for the boys and 5.5% for the girls attending school), the geographical difference showed a significant difference between the urban (4.6-6.9%) and rural areas (5.6-8.8%) (p < 0.05). Based on the high positive rates, it should be necessary to control toxoplasmosis in Cheju island.

A toxoplasmic uveitis case of a 60-year-old male in Korea

A toxoplasmic uveitis case was reported on the focus of impairment of pathological findings and serological antibody titers after chemotherapy. A chief complaint of a 60-year-old male was a decreased and blurred vision in his right eye for 2 weeks after experiencing tremendous stress and fatigue. A steroid therapy for 3 weeks was not effective and the retinal lesion became necrotic. Anti-Toxoplasma gondii antibody titer was checked to be a strong positive by both ELISA and indirect latex agglutination assay (ILA). He was treated with Fansidar F for 8 weeks. His vision improved as the necrotic lesion healed by scarring, but the antibody titers still remained very high without any signs of negative conversion. It is suggested to be a recurrent case of the past asymptomatic infection by presumed immune suppression caused by excessive stress.

Western blot analysis of stray cat sera against Toxoplasma gondii and the diagnostic availability of monoclonal antibodies in sandwich-ELISA

A total of 198 sera from stray cats was assayed against Toxoplasma gondii antigen by western blot. Out of 198 sera assayed, 26 sera (13.1%) showed typical blot patterns against T. gondii. When spotted by ELISA absorbance and indirect latex agglutination test (ILAT) titer, all 26 cases were distributed over the cut-off value of ELISA whereas 24 cases (92.3%) were in the positive range of 1:32 or higher and 2 cases in negative range by ILAT. Among western blot negative 172 sera, 162 cases were negative in both ILAT and ELISA while 10 cases were reactive falsely such that three cases were ILAT positive with 1:32 titer and 9 cases were ELISA positive (2 cases overlapped). These 10 cases reacted peculiarly without typical binding pattern in Western blot. Sandwich-ELISA was performed with monoclonal antibodies (mAbs) of Tg563 (30 kDa, SAG1), Tg505 (22 kDa, SAG2), Tg605 (43 kDa, SAG3), Tg556 (28 kDa. GRA2), Tg737 (32 kDa, GRA6), Tg695 (66 kDa, ROP2), Tg786 (42 kDa, ROP6), and Tg621 (32 kDa, anonymous but cytosolic) clone, respectively. All western blot-positive cases were in the positive range and negative cases in the negative range clearly. Among the 10 false reactive cases, 3 cases were in the positive range with one or more mAbs. All mAbs used in this study were confirmed to be specific to T. gondii infection as a standardized sandwich-ELISA to differentiate it from other pathogens.

A survey of helminthic infections in the residents of rural areas near Ulaanbaatar, Mongolia

A total of 738 samples was collected to survey the helminthic infections of residents in two rural areas near Ulaanbaatar, Mongolia for 2 weeks from July 23 to August 2, 1998. Among 391 scotch-taped slides of anal swabs of children and of young teenagers. Enterobius vermicularis eggs were detected in 138 cases (35.3%). With the fecal samples of 206 Kato-Katz thick smear slides from adults, the eggs of E. vermicularis were observed in 9 cases and Taenia sp. in one case, respectively. And by ELISA on 141 blood samples absorbed to blood sampling paper, 12 cases (8.5%) were found to be positive against the hydatid cyst antigen. Enterobiasis and hydatidosis are two major endemic diseases which are related closely to the life style of Mongolian.

Early recognized antigen (p34) of Toxoplasma gondii after peroral ingestion of tissue cyst forming strain (Me49 strain) in mice

Serum from mouse orally ingested with tissue cyst forming strain (Me49) of Toxoplasma gondii was assayed by Western blot and immunofluorescene assay (IFA) to establish early responses in antigenicity of the parasite in mouse model of foodborne toxoplasmosis. Sera were collected weekly to blot the RH antigen transferred onto nitrocellulose paper after being separated by 12% SDS-PAGE. With the second week serum, 34 kDa protein (p34) was detected uniquely, and all antigens of T. gondii were detected with the sera from 3 or 4 weeks. p34 was not a member of the major surface membrane proteins and confirmed to be localized in the rhoptry by IFA. It was secreted into parasitophorous vacuolar membrane (PVM) during the entry into host cells. When applied to the human sera of which the ELISA absorbance was in negative range, 10.3% of sera detected p34, while all the ELISA positive sera detected the band. It has diagnostic usefulness of presumed T. gondii infection. We suggest the name of the p34 protein as ROP9.

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

Anti-Neospora caninum antibody was detected in anti-Toxoplasma gondii positive and negative human sera by ELISA, western blot and immunofluorescence assay (IFA). Twelve cases out of 172 (6.7%) Toxoplasma-positive sera cross-reacted with both T. gondii and N. caninum antigens, and one out of 110 Toxoplasma-negative sera reacted with N. caninum antigen by ELISA. By western blot, all 12 sera reacted with T. gondii antigens with various banding patterns but specifically at 30 kDa (SAG1) and 22 kDa (SAG2) bands. With N. caninum antigen, the number of reactive bands was reduced, however a 43 kDa band reacted in three cases in Toxoplasma-positive sera in addition to one in Toxoplasma-negative control sera. All sera of the Toxoplasma-positive group labeled surface membrane of T. gondii, but reacted differently with N. caninum. Fluorescence was detected in surface membrane, subcellular organelles, or both in N. caninum. And one case in the Toxoplasma-negative group also reacted with N. caninum strongly in subcellular organelles. This suggested that the antibody against N. caninum may be present in human sera although the positive rate was very low in this study. The possibility of human infection with N. caninum remains to be evaluated further.

Partially purified Toxoplasma gondii antigens by immunoaffinity chromatography

Tachyzoite antigens of Toxoplasma gondii (RH) were partially purified by immunoaffinity chromatography. The cultivated Toxoplasma in vivo (mouse) and in vitro (Hep-2 cell) and peritoneal fluid of T. gondii infected mice were collected for antigen analysis. Tachyzoite antigens collected from infected mouse showed positive bands of 76 kDa, 70 kDa, 64 kDa, 53 kDa, 46 kDa, 44 kDa, 41 kDa, 35 kDa, 25 kDa, 18 kDa, and 13 kDa on immunoblot with anti-Toxoplasma rabbit sera, and those from infected Hep-2 cells revealed reactive bands of 70 kDa, 64 kDa, 53 kDa, 35 kDa 28 kDa, and 13-10 kDa. After applying to an IgG-Sepharose column, two elution peaks, E-1 and E-2 fractions, were obtained from both soluble antigen of T. gondii and the peritoneal fluid of infected mice, respectively. Immunoblots of soluble antigen with immunized rabbit sera revealed positive bands of 97 kDa, 63 kDa, 53 kDa, and 35 kDa from E-1 fraction and 53 kDa and 35 kDa from E-2. In the case of the eluted peaks from mice peritoneal fluid, E-1 showed protein bands of 84 kDa, 76 kDa, 53 kDa, and 29 kDa bands and 53 kDa and 45 kDa from E-2 on immunoblots. Serum IgG antibody titer of mice immunized with T. gondii tachyzoites was increased on 1 week after booster immunization when analysed by ELISA using crude antigen, while it was elevated on 3 weeks after booster immunization by ELISA using purified antigen.

Toxoplasma antibody titers by ELISA and indirect latex agglutination test in pregnant women

The seroepidemiologic studies on anti-Toxoplasma antibody titers were carried out using ELISA and indirect latex agglutination test. Among 899 sera prepared from pregnant women, 39 cases (4.3%) revealed positive reaction and 218 sera from middle school students showed 4 positive reaction (1.8%) by ELISA. By LAT (newly established by National Veterinary Research Institute. Korea), the sera of 7 pregnant women (0.8%) showed positive reaction. When 80 sera showing > or = 1:8 by LAT were used for comparing the results obtained from LAT and Toxotest-MT (Eiken Chemical Co., Japan), 7 cases and 8 sera were positive, respectively. All of 11 sera of proven toxoplasmosis patients showed positive reaction in both tests. Overall proportion of agreement between LAT kit and Toxotest-MT was 0.94 (kappa-index = 0.632, p < 0.011, and LAT was considered to be useful for the screening of toxoplasmosis.