Serological diagnosis of toxoplasmosis and standardization

RPA-CRISPR/Cas12a-LFA combined with a digital visualization instrument to detect Toxoplasma gondii in stray dogs and cats in Zhejiang province, China

Toxoplasma gondii, which causes toxoplasmosis, is prevalent in warm-blooded animals, such as cats, dogs, and humans. T. gondii causes economic losses to livestock production and represents a potential risk to public health. Dogs and cats are common hosts in the epidemiology of toxoplasmosis. The current molecular diagnostic tools for T. gondii infection require high technical skills, a laboratory environment, and complex instruments. Herein, we developed a recombinase polymerase amplification (RPA)-clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12a (Cas12a) assay to detect T. gondii. The lowest limit of detection of the assay was 31 copies/μL for the T. gondii B1 gene. In addition, we established a visual RPA-CRISPR/Cas12a lateral flow band assay (RPA-CRISPR/Cas12a-LFA) combined with a digital visualization instrument, which minimized the problem of false-negative results for weakly positive samples and avoided misinterpretation of the results by the naked eye, making the LFA assay results more accurate. The assay established in this study could identify T. gondii within 55 min with high accuracy and sensitivity, without cross-reaction with other tested parasites. The developed assay was validated by establishing a mouse model of toxoplasmosis. Finally, the developed assay was used to investigate the prevalence of T. gondii in stray cats and dogs in Zhejiang province, Eastern China. The positive rates of T. gondii infection in stray cats and dogs were 8.0% and 4.0%, respectively. In conclusion, the RPA-CRISPR/Cas12a-LFA is rapid, sensitive, and accurate for the early diagnosis of T. gondii, showing promise for on-site surveillance.

IMPORTANCE

Toxoplasma gondii is a virulent pathogen that puts millions of infected people at risk of chronic disease reactivation. Hosts of T. gondii are distributed worldwide, and cats and dogs are common hosts of T. gondii. Therefore, rapid diagnosis of early T. gondii infection and investigation of its prevalence in stray dogs and cats are essential. Here, we established a visual recombinase polymerase amplification-clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12a-assay combined with a lateral flow band assay and a digital visualization instrument. Detailed analyses found that the assay could be used for the early diagnosis of T. gondii without false-negative results. Moreover, we detected the prevalence of T. gondii in stray cats and dogs in Zhejiang province, China. Our developed assay provides technical support for the early diagnosis of T. gondii and could be applied in prevalence surveys of T. gondii in stray dogs and cats.

Prevalence of ocular toxoplasmosis among people living with HIV: a systematic review and meta-analysis

Aim: To determine the prevalence of ocular toxoplasmosis among people living with HIV through a systematic review and meta-analysis. Materials & methods: A literature search was conducted, estimating pooled prevalence and performing quality assessment, outlier, influential and meta-regression analyses. Results: Twenty-nine studies were included in the analysis, revealing that the rate of ocular toxoplasmosis among people living with HIV was 0.37% (95% CI: 0.2-0.6). Substantial heterogeneity was observed among the studies. Despite analyzing continuous variables, including year of publication, proportion of males, mean age and proportion of patients receiving antiretroviral therapy, no statistically significant associations were found. Conclusion: This study provides an overview of the prevalence of ocular toxoplasmosis in people living with HIV, emphasizing the need for further research to uncover factors contributing to its development.

Metallic Nanoparticles and Core-Shell Nanosystems in the Treatment, Diagnosis, and Prevention of Parasitic Diseases

The usage of nanotechnology in the fight against parasitic diseases is in the early stages of development, but it brings hopes that this new field will provide a solution to target the early stages of parasitosis, compensate for the lack of vaccines for most parasitic diseases, and also provide new treatment options for diseases in which parasites show increased resistance to current drugs. The huge physicochemical diversity of nanomaterials developed so far, mainly for antibacterial and anti-cancer therapies, requires additional studies to determine their antiparasitic potential. When designing metallic nanoparticles (MeNPs) and specific nanosystems, such as complexes of MeNPs, with the shell of attached drugs, several physicochemical properties need to be considered. The most important are: size, shape, surface charge, type of surfactants that control their dispersion, and shell molecules that should assure specific molecular interaction with targeted molecules of parasites' cells. Therefore, it can be expected that the development of antiparasitic drugs using strategies provided by nanotechnology and the use of nanomaterials for diagnostic purposes will soon provide new and effective methods of antiparasitic therapy and effective diagnostic tools that will improve the prevention and reduce the morbidity and mortality caused by these diseases.

Detection of chronic toxoplasmosis in the brain of mice using loop-mediated isothermal amplification (LAMP) and conventional PCR

BACKGROUND

Toxoplasma gondii is a common protozoan parasite that infects approximately one-third of the world's population. It is a disease with multiple manifestations. In immunocompetent individuals, symptoms are mild and flu-like, whereas, in immunocompromised patients, it often results in severe morbidity and mortality. Thus, studies for developing a simple, rapid diagnostic tool for early detection of Toxoplasma are emerging. Molecular diagnosis is highly accurate and helpful in congenitally infected and immunocompromised patients. The loop-mediated isothermal amplification (LAMP) technique was invented to improve nucleic acid amplification efficacy in terms of sensitivity and specificity.

AIM OF THE STUDY

The study aimed to validate a LAMP protocol for detecting Toxoplasma DNA in the brain homogenates from mice experimentally infected with Toxoplasma's ME-49 (cyst-forming type II) strain in comparison to PCR.

METHODS

In this study, the target DNA fragment was the Toxoplasma 529-bp, repeated 200-300 copies/genome. The sensitivity of both LAMP and conventional PCR techniques was estimated in brain homogenates in experimental mice at eight weeks post-infection and compared to the histopathology data.

RESULTS

The LAMP reaction showed positive results in 18 of the 26 examined samples of brain homogenates. PCR showed the characteristic 529-bp band in 15 of the 26 examined samples.

CONCLUSION

The LAMP showed a higher sensitivity over PCR in detecting Toxoplasma infection in brain homogenates of infected mice.

Diagnosis of Toxoplasmosis Using Surface Antigen Grade 1 Detection by ELISA, Nano-Gold ELISA, and PCR in Pregnant Women

Introduction

The accurate diagnosis of toxoplasmosis has critical importance in pregnant women. Nanotechnology and molecular biology are making possible opportunities for accurate and rapid diagnosis of many infectious diseases.

Aim and Methods

The aim of our study was to compare nano-gold ELISA with ELISA and PCR for diagnosis of toxoplasmosis using Toxoplasma surface antigen grade 1 (SAG1) in pregnant women seeking antenatal care in outpatient clinics.

Results

PCR showed the highest diagnostic values than nano-gold ELISA and ELISA regarding sensitivity (97.3% versus 89.2% and 83.8%); specificity (100% versus 94% and 88%); and diagnostic accuracy (98.9% versus 91.95% and 86.2%), respectively. There is no statistical difference between PCR and nanogold ELISA results.

Discussion

Nano-gold ELISA had a significant improvement in diagnosis than the traditional ELISA method. Most likely with the assistance of nanoparticles, more antibodies enter the antigen-antibody complex because of the considerable improvement in the surface area of nano-gold particles.

Conclusion

Although PCR had higher diagnostic values than nano ELISA, nano ELISA is cheaper and easier than PCR. We recommend nano-gold ELISA with SAG1 as a promising technique in the diagnosis of toxoplasmosis and survey studies.

Assessment of Geographical Distribution of Emerging Zoonotic Toxoplasma gondii Infection in Women Patients Using Geographical Information System (GIS) in Various Regions of Khyber Pakhtunkhwa (KP) Province, Pakistan

Toxoplasmosis is a zoonotic parasitic disease caused by T. gondii, an obligate intracellular apcomplexan zoonotic parasite that is geographically worldwide in distribution. The parasite infects humans and all warm-blooded animals and is highly prevalent in various geographical regions of the world, including Pakistan. The current study addressee prevalence of Toxoplasma infection in women in various geographical regions, mapping of endemic division and t district of Khyber Pakhtunkhwa province through geographical information system (GIS) in order to locate endemic regions, monitor seasonal and annual increase in prevalence of infection in women patients. Setting: Tertiary hospitals and basic health care centers located in 7 divisions and 24 districts of Khyber Pakhtunkhwa (KP) province of Pakistan. During the current study, 3586 women patients from 7 divisions and 24 districts were clinically examined and screened for prevalence of T. gondii infection. Participants were screened for Toxoplasma infection using ICT and latex agglutination test (LAT) as initial screening assay, while iELISA (IgM, IgG) was used as confirmatory assay. Mapping of the studied region was developed by using ArcGIS 10.5. Spatial analyst tools were applied by using Kriging/Co-kriging techniques, followed by IDW (Inverse Distance Weight) techniques. Overall prevalence of T. gondii infection was found in 881 (24.56%) patients. A significant (<0.05) variation was found in prevalence of infection in different divisions and districts of the province. Prevalence of infection was significantly (<0.05) high 129 (30.07%) in Kohat Division, followed by 177 (29.06%), 80 (27.87%), 287 (26.72%), 81 (21.21%), 47 (21.07%), and 80 (13.71%) cases in Hazara Division, D.I Khan Division, Malakand Division, Mardan Division, Bannu Division, and Peshawar Division. Among various districts, a significant variation (<0.05) was found in prevalence of infection. Prevalence of infection was significantly (<0.05) high 49 (44.95%) in district Karak, while low (16 (10.81%) in district Nowshera. No significant (>0.05) seasonal and annual variation was found in prevalence of Toxoplasma infection. LAT, ICT and ELISA assays were evaluated for prevalence of infection, which significantly (<0.05) detected T. gondii antibodies. LAT, ICT and ELISA assays significantly (<0.05) detected infection, while no significant (>0.05) difference was found between positivity of LAT and ICT assays. A significant difference (<0.05) was found in positivity of Toxoplasma-specific (IgM), (IgG) and (IgM, IgG) immunoglobulin by ICT and ELISA assay. The current study provides comprehensive information about geographical distribution, seasonal and annual variation of Toxoplasmosis infection in various regions of Khyber Pakhtunkhwa province of Pakistan. Infection of T. gondii in women shows an alarming situation of disease transmission from infected animals in the studied region, which is not only a serious and potential threat for adverse pregnancy outcomes, but also cause socioeconomic burden and challenges for various public and animal health organizations in Pakistan and across the country.

IgG Avidity Test as a Tool for Discrimination between Recent and Distant Toxoplasma gondii Infection—Current Status of Studies

Toxoplasma gondii, an obligate intracellular protozoan parasite, is the causative agent of one of the most prevalent zoonoses worldwide. T. gondii infection is extremely important from a medical point of view, especially for pregnant women, newborns with congenital infections, and immunocompromised individuals. Thus, an accurate and proper diagnosis of this infection is essential. Among the available diagnostic tests, serology is commonly used. However, traditional serological techniques have certain limitations in evaluating the duration of T. gondii infection, which is problematic, especially for pregnant women. Avidity of T. gondii-specific IgG antibodies seems to be a significant tool for discrimination between recent and distant infections. This article describes the problem of diagnosis of T. gondii infection, with regard to IgG avidity tests. The IgG avidity test is a useful serological indicator of toxoplasmosis, which in many cases can confirm or exclude the active form of the disease. IgG antibodies produced in the recent primary T. gondii infection are of low avidity while IgG antibodies with high avidity are detected in the chronic phase of infection. Furthermore, this paper presents important topics of current research that concern the usage of parasite recombinant antigens that may improve the performance of IgG avidity tests.

Development of an Immunochromatographic Test Based on Rhoptry Protein 14 for Serological Detection of Toxoplasma gondii Infection in Swine

Toxoplasma gondii, a worldwide distributed apicomplexan protozoan, can infect almost all warm-blooded animals and may cause toxoplasmosis. In order to provide a point-of-care detection method for T. gondii infection, an immunochromatographic test (ICT) was established. The proposed test uses recombinant T. gondii rhoptry protein 14 (ROP14) conjugated with 20 nm gold particles, recombinant protein A as the detection line and monoclonal antibody TgROP14-5D5 as the control line. The specificity, sensitivity, positive predictive value, negative predictive value and stability of this new ICT were evaluated. rTgROP14 was specifically recognized by positive serum of T. gondii but not negative serum. mAb TgROP14-5D5 showed higher specific recognition of T. gondii antigens and was therefore selected for subsequent colloidal gold strip construction. The new ICT based on TgROP14 exhibited good diagnostic performance with high specificity (86.9%) and sensitivity (90.9%) using IHA as a “reference standard”. Among 436 field porcine sera, ICT and IHA detected 134 (30.7%) and 99 (22.7%) positive samples, respectively. The relative agreement was 87.8%. These data indicate that this new ICT based on TgROP14 is a suitable candidate for routine testing of T. gondii in the field.

A systematic literature review and meta-analysis of Toxoplasma gondii seroprevalence in goats

The aim of this study was evaluate to seroprevalence of Toxoplasma gondii in goats worldwide and the main risk factors associated from 2000 to 2020, through meta-analysis with 55,317 goats from 75 reports published in seven electronic databases of major global importance. A global seroprevalence detected was 27.49% (95% CI 24.15-30.95; I2 = 99%), with the lowest percentage in Asia (20.74%; 95% CI 16.45-25.39) and highest in Central America (62.15%; 95% CI 57.28-66.90) and Europe (31.53%; 95% CI 21.71-42.26). The seropositivity in Africa and South America were (29.41%; 95% CI 19.11-40.89) and (29.76%; 95% CI 25.84-33.83), respectively. The seroprevalence was associated with presence of cats (OR 2.22; 95% CI 1.30-3.82), goats older than one year (OR 1.77; 95% CI 1, 37-2.29), females (OR 1.43; 95% CI 1.23-1.65), rearing system (extensive vs. intensive) (OR 4.82; 95% CI 1.96-11, 84) and rearing system (semi-intensive vs. intensive) (OR 1.48; 95% CI 1.48-6.13). The heterogeneity was evidenced in most world regions and the risk factors may play roles in varying the seroprevalence.

Mining the Proteome of Toxoplasma Parasites Seeking Vaccine and Diagnostic Candidates

Simple Summary

The One Health concept to toxoplasmosis highlights that the health of humans is closely related to the health of animals and our common environment. Toxoplasmosis outcomes might be severe and fatal in patients with immunodeficiency, diabetes, and pregnant women and infants. Consequently, the development of effective vaccine and diagnostic strategies is urgent for the elimination of this disease. Proteomics analysis has allowed the identification of key proteins that can be utilized in the development of novel disease diagnostics and vaccines. This work presents relevant proteins found in the proteome of the life cycle-specific stages of Toxoplasma parasites. In fact, it brings together the main functionality key proteins from Toxoplasma parasites coming from proteomic approaches that are most likely to be useful in improving the disease management, and critically proposes innovative directions to finally develop promising vaccines and diagnostics tools.

Abstract

Toxoplasma gondii is a pathogenic protozoan parasite that infects the nucleated cells of warm-blooded hosts leading to an infectious zoonotic disease known as toxoplasmosis. The infection outcomes might be severe and fatal in patients with immunodeficiency, diabetes, and pregnant women and infants. The One Health approach to toxoplasmosis highlights that the health of humans is closely related to the health of animals and our common environment. The presence of drug resistance and side effects, the further improvement of sensitivity and specificity of serodiagnostic tools and the potentiality of vaccine candidates to induce the host immune response are considered as justifiable reasons for the identification of novel targets for the better management of toxoplasmosis. Thus, the identification of new critical proteins in the proteome of Toxoplasma parasites can also be helpful in designing and test more effective drugs, vaccines, and diagnostic tools. Accordingly, in this study we present important proteins found in the proteome of the life cycle-specific stages of Toxoplasma parasites that are potential diagnostic or vaccine candidates. The current study might help to understand the complexity of these parasites and provide a possible source of strategies and biomolecules that can be further evaluated in the pathobiology of Toxoplasma parasites and for diagnostics and vaccine trials against this disease.

A novel rapid visual detection assay for Toxoplasma gondii combining recombinase-aided amplification and lateral flow dipstick coupled with CRISPR-Cas13a fluorescence (RAA-Cas13a-LFD)

Toxoplasmosis, a parasitic disease resulting from Toxoplasma gondii infection, remains prevalent worldwide, and causes great harm to immunodepressed patients, pregnant women and newborns. Although various molecular approaches to detect T. gondii infection are available, they are either costly or technically complex. This study aimed at developing a rapid visual detection assay using recombinase-aided amplification (RAA) and lateral flow dipstick (LFD) coupled with CRISPR-Cas13a fluorescence (RAA-Cas13a-LFD) to detect T. gondii. The RAA-Cas13a-LFD assay was performed in an incubator block at 37 °C within 2 h, and the amplification results were visualized and determined through LFD by the naked eye. The detection limit was 1 × 10^-6 ng/μL by our developed RAA-Cas13a-LFD protocol, 100-fold higher than that by qPCR assay (1 × 10^-8 ng/μL). No cross-reaction occurred either with the DNA of human blood or Ascaris lumbricoides, Digramma interrupta, Entamoeba coli, Fasciola gigantica, Plasmodium vivax, Schistosoma japonicum, Taenia solium, and Trichinella spiralis, and the positive rate by RAA-Cas13a-LFD assay was identical to that by qPCR assay (1.50% vs. 1.50%) in detecting T. gondii infection in the unknown blood samples obtained from clinical settings. Our findings demonstrate that this RAA-Cas13a-LFD assay is not only rapid, sensitive, and specific and allows direct visualization by the naked eye, but also eliminates sophisticated and costly equipment. More importantly, this technique can be applied to on-site surveillance of T. gondii.

Comparative Performance of Recombinant GRA6, GRA7, and GRA14 for the Serodetection of T. gondii Infection and Analysis of IgG Subclasses in Human Sera from the Philippines

Highly specific and sensitive diagnostic methods are vital for the effective control and treatment of toxoplasmosis. Routine diagnosis is primarily serological because T. gondii infections stimulate persistently high IgG antibody responses. The sensitivity and specificity of methods are crucial factors for the proper diagnosis of toxoplasmosis, primarily dependent on the antigens used in different assays. In the present study, we compared the serodiagnostic performances of three recombinant dense granule antigens, namely, the GRA6, GRA7, and GRA14, to detect IgG antibodies against T. gondii in human sera from the Philippines. Moreover, we evaluated the IgG1, IgG2, IgG3, and IgG4 responses against the different recombinant antigens, which has not been performed previously. Our results revealed that the TgGRA7 has consistently displayed superior diagnostic capability, while TgGRA6 can be a satisfactory alternative antigen among the GRA proteins. Furthermore, IgG1 is the predominant subclass stimulated by the different recombinant antigens. This study's results provide options to researchers and manufacturers to choose recombinant antigens suitable for their purpose.

A novel enhanced dot blot immunoassay using colorimetric biosensor for detection of Toxoplasma gondii infection

This study reports development of a novel point of care assay, namely an enhanced immuno-dot blot assay, for discrimination of anti-Toxoplasma IgG and anti-Toxoplasma IgM antibodies. This method has been designed based on formation of a sandwich complex between a gold nanoprobe (chitosan gold nanoparticle-anti-human IgG or anti-IgM) and anti- Toxoplasma lysate antigen (TLA) which holds anti-TLA antibodies, either IgG or IgM. Briefly, anti-human IgG or anti-IgM antibody was conjugated to chitosan gold nanoparticles via glutaraldehyde chemistry. Then, lysate antigen was immobilized on the surface of nitrocellulose membrane, which followed by addition of the sera sample and gold nanoprobes. The positive signals were readily detectable via observation with naked eye. This positive color change was further intensified via gold enhancement chemistry. The intensity of biosensor signal was proportional to the concentration of active antibodies on the surface of nanoparticles, titer of T. gondii antibodies in the sera samples and concentration of Toxoplasma lysate antigen coated on the nitrocellulose membrane. A minimum concentration to use the antibodies for conjugation, to detect titer of Toxoplasma IgG and IgM antibodies, and the concentration of TLA coated in nitrocellulose membrane were 0.5 mg/mL, 2 IU/mL, 10 IU/mL, and 20 μg/mL, respectively. This enhanced immuno-dot blot assay offers a simple diagnostic technique without expensive equipment requirement for distinguishing of anti- T. gondii IgM and IgG antibodies in field conditions, pregnant women, and immunocompromised patients.

Characterization and evaluation of a recombinant multiepitope peptide antigen MAG in the serological diagnosis of Toxoplasma gondii infection in pigs

Background

Toxoplasmosis caused by Toxoplasma gondii is a serious disease threatening human and animal health. People can be infected with T. gondii by ingesting raw pork contaminated with cysts or oocysts. Serological test is a sensitive and specific method usually used for large-scale diagnosis of T. gondii infection in humans and animals (such as pigs). Commercial pig Toxoplasma antibody ELISA diagnostic kits are expensive, which limits their use; moreover, the wide antigen composition used in these diagnostic kits is still unclear and difficult to standardize. The multiepitope peptide antigen is a novel diagnostic marker, and it has potential to be developed into more accurate and inexpensive diagnostic kits.

Methods

The synthetic multiepitope antigen (MAG) cDNA encoding a protein with epitopes from five T. gondii-dominant antigens (SAG1, GRA1, ROP2, GRA4, and MIC3) was designed, synthesized, and expressed in Escherichia coli BL21 (DE3) strain. The recombinant protein was detected through western blot with pig anti-T. gondii-positive and -negative serum, and then IgG enzyme-linked immunosorbent assay (ELISA) named MAG-ELISA was designed. The MAG-ELISA was evaluated in terms of specificity, sensitivity, and stability. The MAG-ELISA was also compared with a commercial PrioCHECK^®Toxoplasma Ab porcine ELISA (PrioCHECK ELISA). Finally, the trend of pig anti-T. gondii IgG levels after artificial infection with RH tachyzoites was evaluated using MAG-ELISA and two other ELISA methods (rMIC3-ELISA and PrioCHECK ELISA).

Results

MAG antigen could be specifically recognized by pig anti-T. gondii-positive but not -negative serum. MAG-ELISA showed high diagnostic performance in terms of specificity (88.6%) and sensitivity (79.1%). MAG-ELISA could be used for detecting anti-T. gondii IgG in the early stage of T. gondii infection in pigs (at least 7 days after artificial infection).

Conclusions

Our results suggest that MAG antigen can be applied to specifically recognize anti-T. gondii IgG in pig, and MAG-ELISA has the potential for large-scale screening tests of T. gondii infection in pig farms and intensive industries.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04917-w.

Development of a real-time recombinase-aided amplification (RT-RAA) molecular diagnosis assay for sensitive and rapid detection of Toxoplasma gondii

Toxoplasma gondii, a protozoan intracellular parasite, is present in a wide range of hosts, including virtually all species of warm-blooded vertebrates. Toxoplasmosis spreads to humans through a variety of pathways, including contaminated food or water, and close contact with various types of domestic animals. It poses a severe threat to human health, and contributes to important economic losses, not only in cost-of-illness but also in surveillance programs. It is thus necessary to develop a rapid point-of-care field diagnostic technology to control or prevent pathogen transmission to economically important livestock animals, domestic animals, and human beings. In this study, we develop a real-time isothermal amplification method capable of detecting the T. gondii genome in swine and feline blood samples. This method can detect toxoplasma genome with a lowest detection limit of 10² copies of per reaction under optimal reaction conditions of 36 °C for 25 min. The assay displayed advantages in sensitivity and specificity in comparison to traditional real-time PCR, and can be performed in a portable instrument.

Detection of toxoplasmosis in aborted women in Alexandria, Egypt using ELISA and PCR

Toxoplasmosis is a worldwide infection that can be acquired through the ingestion of tissue cysts in poorly cooked meat, and/or oblivious intake of sporulated oocysts in cat faeces, and transplacental. The infection in pregnant women is mainly asymptomatic. It produces abortion or congenital infection. The present study aimed to test the utility of polymerase chain reaction (PCR) on placental tissues in comparison to enzyme-linked immunosorbent assay (ELISA) to detect infections with Toxoplasma gondii in aborted women presented to Al-Shatby Maternity Hospital, Alexandria University, Egypt. Specific Toxoplasma gondii IgG and IgM were detected in serum by ELISA. Placental tissues from each participant were subjected to DNA extraction and PCR amplification. It was found that overall seroprevalence was 73%, DNA was detected in placenta tissues by using PCR analysis in 46% of cases. {× 2 (p) 18.124(< 0.001)}. Toxoplasma IgG/IgM by ELISA was positive in 23% of the cases, 20% showed amplified DNA by PCR. Positive IgG without IgM was seen in 27% cases, only 2% of them were positive by PCR. Moreover, positive PCR among positive ELISA IgM aborted women was 21 of the 23 cases. Positive PCR was obtained in three seronegative women. Our results showed that PCR sensitivity was 58.90 specificity 88.89, positive predictive value was 93.48%, and negative predictive value 44.44%. Although ELISA assay is still the gold standard of diagnosis of Toxoplasmosis, other diagnostic modalities are highly required particularly in those ELISA seronegative cases. PCR can be used as a sensitive and precise modality.

Development and evaluation of recombinant GRA8 protein for the serodiagnosis of Toxoplasma gondii infection in goats

BACKGROUND

The development of sensitive and specific methods for detecting Toxoplasma gondii infection is critical for preventing and controlling toxoplasmosis in humans and other animals. Recently, various recombinant proteins have been used in serological tests for diagnosing toxoplasmosis. The production of these antigens is associated with live tachyzoites obtained from cell cultures or laboratory animals for genomic extraction to amplify target genes. Synthetic genes have gained a key role in recombinant protein production. For the first time, we demonstrated the production of the recombinant protein of the T. gondii dense granular antigen 8 (TgGRA8) gene based on commercial gene synthesis. Recombinant TgGRA8 plasmids were successfully expressed in an Escherichia coli system. The recombinant protein was affinity-purified and characterized via sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Furthermore, the diagnostic potential of the recombinant protein was assessed using 306 field serum samples from goats via indirect enzyme-linked immunosorbent assay (iELISA) and the latex agglutination test (LAT).

RESULTS

Western blotting using known positive serum samples from goats identified a single antigen at the expected molecular weight of TgGRA8 (27 kDa). iELISA illustrated that 15.40% of goat samples were positive for T. gondii-specific IgG antibodies. In addition, TgGRA8 provided high sensitivity and specificity, with significant concordance (91.83) and kappa values (0.69) compared with the results obtained using LAT.

CONCLUSION

Our findings highlight the production of a recombinant protein from a synthetic TgGRA8 gene and the ability to detect T. gondii infection in field samples. The sensitivity and specificity of TgGRA8 demonstrated that this protein could be a good serological marker for detecting specific IgG in goat sera.

Putative biomarkers for early diagnosis and prognosis of congenital ocular toxoplasmosis

In the present study we have evaluated the performance of several immunological biomarkers for early diagnosis and prognosis of congenital toxoplasmosis. Our results showed that ex vivo serum levels of CXCL9, and the frequencies of circulating CD4⁺CD25⁺ T-cells and T. gondii-specific IFN-γ⁺CD4⁺ T-cells measured 30–45 days after birth presented high accuracy to distinguish T. gondii-infected infants from healthy age-matched controls (Global Accuracy/AUC = 0.9; 0.9 and 0.8, respectively). Of note was the enhanced performance (Accuracy = 96%) achieved by using a combined stepwise analysis of CD4⁺CD25⁺ T-cells and CXCL9. In addition, high global accuracy (AUC = 0.9) with elevated sensitivity (Se = 98%) was also reached by using the total frequency of in vitro IFN-γ-producing T. gondii-specific T-cells (∑ IFN-γ⁺ CD4⁺ & CD8⁺) as a biomarker of congenital toxoplasmosis. Furthermore, the analysis of in vitro T. gondii-specific IL5⁺CD4⁺ T-cells and IFN-γ⁺NK-cells displayed a high accuracy for early prognosis of ocular lesion in infant with congenital toxoplasmosis (Global Accuracy/AUC = 0.8 and 0.9, respectively). Together, these findings support the relevance of employing the elements of the cell-mediated immune response as biomarkers with potential to endorse early diagnosis and prognosis of congenital ocular toxoplasmosis to contribute for a precise clinical management and effective therapeutic intervention.

Expression of in vivo biotinylated recombinant antigens SAG1 and SAG2A from Toxoplasma gondii for improved seroepidemiological bead-based multiplex assays

BACKGROUND

Few bead-based multiplex assays have been described that detect antibodies against the protozoan parasite Toxoplasma gondii in large-scale seroepidemiological surveys. Moreover, each multiplex assay has specific variations or limitations, such as the use of truncated or fusion proteins as antigens, potentially masking important epitopes. Consequently, such an assay must be developed by interested groups as none is commercially available.

RESULTS

We report the bacterial expression and use of N-terminal fusion-free, soluble, in vivo biotinylated recombinant surface antigens SAG1 and SAG2A for the detection of anti-T. gondii IgG antibodies. The expression system relies on three compatible plasmids. An expression construct produces a fusion of maltose-binding protein with SAG1 (or SAG2A), separated by a TEV protease cleavage site, followed by a peptide sequence recognized by E. coli biotin ligase BirA (AviTag), and a terminal six histidine tag for affinity purification. TEV protease and BirA are encoded on a second plasmid, and their expression leads to proteolytic cleavage of the fusion protein and a single biotinylated lysine within the AviTag by BirA. Correct folding of the parasite proteins is dependent on proper disulfide bonding, which is facilitated by a sulfhydryl oxidase and a protein disulfide isomerase, encoded on the third plasmid. The C-terminal biotinylation allowed the oriented, reproducible coupling of the purified surface antigens to magnetic Luminex beads, requiring only minute amounts of protein per determination. We showed that an N-terminal fusion partner such as maltose-binding protein negatively influenced antibody binding, confirming that access to SAG1's N-terminal epitopes is important for antibody recognition. We validated our bead-based multiplex assay with human sera previously tested with commercial diagnostic assays and found concordance of 98-100% regarding both, sensitivity and specificity, even when only biotinylated SAG1 was used as antigen.

CONCLUSIONS

Our recombinant in vivo-biotinylated T. gondii antigens offer distinct advantages compared to previously described proteins used in multiplex serological assays for T. gondii. They offer a cheap, specific and sensitive alternative to either parasite lysates or eukaryotic-cell expressed SAG1/SAG2A for BBMA and other formats. The described general expression strategy can also be used for other antigens where oriented immobilization is key for sensitive recognition by antibodies and ligands.

The cross-sectional study of Toxoplasma gondii seroprevalence in selected groups of population in Slovakia

Toxoplasma gondii is an obligate intracellular protozoan parasite with domestic or free-living members of family Felidae known as the only definitive hosts of the parasite. The study aimed to evaluate the seroprevalence of toxoplasmosis in selected population groups in Slovakia and to analyse the infection risk factors. Totally 1536 serum samples of voluntary respondents were examined by EIA Toxoplasma IgG (Test-Line Ltd., Clinical Diagnostics, Brno, Czech Republic). IgG antibodies to T. gondii were detected in 322 (21.0%) sera, with the highest seropositivity recorded among farmers (42.5%) and hunters (28.5%). According to age, the highest seropositivity was recorded in 12-18-year-old Roma children (46.2%), what confirms increased risk of infection in this minority that often lives in inadequate hygiene conditions. When only adult participants were taken into account, the highest seroprevalence was observed in the age group of ≥ 70 years. Higher risk of infection (p < 0.05) was connected with cat ownership, living in rural residency and consumption of raw meat and meat processing. The results underline the importance of preventive measures and ongoing need to improve the knowledge on toxoplasmosis in both professionals and public.

Review on the Current Trends of Toxoplasmosis Serodiagnosis in Humans

Toxoplasmosis is a widely distributed zoonotic infection caused by the obligate intracellular apicomplexan parasite Toxoplasma gondii. It is mainly transmitted through the ingestion of oocysts shed by an infected cat acting as its definitive host. The key to effective control and treatment of toxoplasmosis is prompt and accurate detection of T. gondii infection. Several laboratory diagnostic methods have been established, including the most commonly used serological assays such as the dye test (DT), direct or modified agglutination test (DAT/MAT), indirect hemagglutination test (IHA), latex agglutination test (LAT), indirect immunofluorescent test (IFAT), enzyme-linked immunosorbent assays (ELISA), immunochromatographic tests (ICT), and the western blot. Nonetheless, creating specific and reliable approaches for serodiagnosis of T. gondii infection, and differentiating between acute and chronic phases of infection remains a challenge. This review provides information on the current trends in the serodiagnosis of human toxoplasmosis. It highlights the advantages of the use of recombinant proteins for serological testing and provides insight into the possible future direction of these methods.

Prevalence and predictors of Toxoplasma gondii infection in pregnant women from Dhamar, Yemen

BACKGROUND

Toxoplasmosis is a common and serious parasitic infection caused by the ubiquitous obligatory intracellular protozoan organism, Toxoplasma gondii. Although infection with T. gondii is usually asymptomatic in healthy individuals, it can lead to severe pathological effects in congenital cases and immunocompromised patients. This study aimed to determine the seroprevalence of T. gondii and its predictors among pregnant women seeking prenatal and medical care at the general maternal and child health facility in Dhamar district of Dhamar governorate, Yemen.

METHODS

A total of 420 pregnant women were randomly selected for this cross-sectional study. Participants were screened for anti-T. gondii antibodies (i.e. immunoglobulin M; IgM and immunoglobulin G; IgG) using electrochemiluminescence immunoassay. Demographic, socioeconomic, obstetric and behavioural data were collected using a pretested questionnaire via face-to-face interview. Univariate and multivariate analyses were used to identify the independent predictors of T. gondii seroprevalence.

RESULTS

The overall seroprevalence of anti-T. gondii antibodies (IgG and/or IgM) among the participants was 21.2% (89/420; 95% CI = 17.3-25.1). Anti-T. gondii IgG antibodies were detected in 20.0% (84/420) of the women of which 12.9% (54/420) were positive for only IgG and 7.1% (30/420) were positive for both IgG and IgM antibodies. Moreover, 5 women (1.2%) were reactive only for IgM antibodies. Significant associations between T. gondii seroprevalence and history of spontaneous abortion (P <  0.001), raw vegetables consumption (P = 0.036), and presence of cats in household (P = 0.049) were reported. Multivariate analysis confirmed that history of spontaneous abortion (AOR = 4.04; 95% CI = [2.46, 6.63]) and presence of cats in household (AOR = 1.77; 95% CI = [1.02, 3.07]) are significant predictors of T. gondii seroprevalence among the studied participants.

CONCLUSION

The study found a high seroprevalence (21.2%) of T. gondii infection during pregnancy in Dhamar district, which is significantly associated with adverse pregnancy outcomes. The provision of adequate maternal healthcare and health education pertaining to the prevention of T. gondii infection is therefore imperative to curtail the prevalence of infection among the studied population.

Knowledge and practices regarding toxoplasmosis in housewives: A cross sectional study in a northern Mexican city

We aimed to determine the knowledge and practices regarding toxoplasmosis among housewives in the northern Mexican city of Durango. One hundred eighty-five women (mean age: 41.27 ± 12.40 years old) with an occupation of housewife were studied. A self-administered questionnaire was used. This tool included items about the parasite Toxoplasma gondii, its transmission routes, general clinical, diagnostic, and treatment aspects of toxoplasmosis, and practices to avoid infection. A minority (<10%) of women knew about the parasite, the disease, how the transmission occurs, the clinical manifestations, how an infection is diagnosed, the treatment, and how to avoid toxoplasmosis. Some women knew that cats can transmit T. gondii infection (20%), and that the parasite can be found in cat feces (20.5%). Only 7.6% of women knew that infection with T. gondii can be transmitted by consumption of contaminated food or water. Only 1.1% of women knew about the prevalence of T. gondii infection. Some (4.9%) women used to taste raw meat while cooking, and 7.6% used to undercook meat. In addition, 20% of women used to eat raw dried meat, and 13.5% consumed untreated water. Less than 90% of women always washed their hands before cooking, and washed fruits or vegetables. The majority (75.1%) of women never wore gloves when handling raw meat. About one quarter (27.6%) of women always froze meat. And 16.2% of women cleaned cat feces. This is the first study regarding knowledge and practices about toxoplasmosis in housewives. Poor knowledge regarding T. gondii infection, toxoplasmosis, and practices to avoid infection among the housewives studied was found. High risk practices for infection were identified. Strategies to improve toxoplasmosis-related knowledge and practices to avoid T. gondii infection and its sequelae in housewives are highly needed.

Performance of seven commercial automated assays for the detection of low levels of anti-Toxoplasma IgG in French immunocompromised patients

BACKGROUND

Immunocompromised patients are at high risk for the development of severe toxoplasmosis from tissue cyst reactivation, the most frequently, or from recently acquired acute infections. Knowledge of serologic status is therefore crucial. Screening for toxoplasmosis is sometimes performed while patients are already immunocompromised and have a low or even undetectable IgG titer by routine automated enzyme immunoassays. The aim of this study was to assess the sensitivity and specificity of seven reagents for the detection of low levels of IgG. Sera from 354 patients were collected and analysed.

RESULTS

Elecsys^® offered the best analytic performances, superior to those of Architect^® and Platelia^®, which were superior to those of Access II^® and TGS TA^®. Vidas II^® and Liaison II^® reagents exhibited poor analytical performances in this cohort. For Elecsys^®, Platelia^® and Architect^®, new thresholds for the grey zone and positive zone have been defined to improve the sensitivity of these reagents while maintaining excellent specificity.

CONCLUSIONS

Commercialized assays for toxoplasmosis screening are not suitable for IgG low-level detection in patients without adapting the supplier thresholds to avoid false negative results and risk generalized toxoplasmosis.

Detection of Anti-Toxoplasma gondii Antibodies in Human Sera Using Synthetic Glycosylphosphatidylinositol Glycans on a Bead-Based Multiplex Assay

Toxoplasmosis, while often an asymptomatic parasitic disease in healthy individuals, can cause severe complications in immunocompromised persons and during pregnancy. The most common method to diagnose Toxoplasma gondii infections is the serological determination of antibodies directed against parasite protein antigens. Here we report the use of a bead-based multiplex assay containing a synthetic phosphoglycan portion of the Toxoplasma gondii glycosylphosphatidylinositol (GPI1) for the detection of GPI1-specific antibodies in human sera. The glycan was conjugated to beads at the lipid site to retain its natural orientation and its immunogenic groups. We compared the response against GPI1 with that against the protein antigen SAG1, a common component of commercial serological assays, via the detection of parasite-specific human IgG and IgM antibodies, respectively. The GPI1-based test is in excellent agreement with the results for the commercial ELISA, as the ROC analysis of the GPI1 test shows 97% specificity and 98% sensitivity for the assay. GPI1 was a more reliable predictor for a parasite-specific IgM response compared to SAG1, indicating that a bead-based multiplex assay using GPI1 in combination with SAG1 may strengthen Toxoplasma gondii serology, in particular in seroepidemiological studies.

A novel peptide-based sensor platform for detection of anti-Toxoplasma gondii immunoglobulins

Toxoplasma gondii is an intracellular protozoan parasite responsible for toxoplasmosis, which affects humans and animals. Serologic detection of anti-T. gondii immunoglobulins plays a crucial role in the clinical diagnosis of toxoplasmosis. In this work, a novel electrochemical immunosensor for detecting anti-T. gondii immunoglobulins is reported, based on immobilization of an in silico predicted peptide (PepB3), obtained from membrane protein of T. gondii, on the graphite electrode modified with poly(3-hydroxybenzoic acid). Indirect ELISA confirmed infection and binding specificity of peptide PepB3. Molecular modelling and simulations show this peptide binds to the T. gondii human Fab antibody in the surface antigen 1 (SAG1) binding site, remaining a stable complex during the molecular dynamic simulations, especially by hydrogen bonds and hydrophobic interactions. This electrochemical immunosensor was able to discriminate different periods of infection, using infected mouse serum samples, showing selectivity and discriminating infected and uninfected mouse serum.

Focal Intramedullary Spinal Cord Lesion in Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome: Toxoplasmosis Versus Lymphoma

BACKGROUND

Neurologic complications are common in patients with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). Although both the central nervous system (CNS) and the peripheral nervous system can be affected, 80% of patients with HIV/AIDS have CNS involvement during the course of their illness. The brain is the primary site of HIV/AIDS-associated CNS complications. Spinal cord involvement is rare, particularly focal intramedullary spinal cord lesions without any associated cerebral lesions. Among various opportunistic infections and malignancies, toxoplasmosis and CNS lymphoma are the most common causes of focal neurologic disease in patients with HIV/AIDS. Distinguishing between toxoplasmosis and CNS lymphoma is challenging, as the diseases have similar clinical presentations.

CASE DESCRIPTION

In a woman with newly diagnosed HIV infection, myelopathy manifested as an isolated, single intramedullary spinal cord lesion.

CONCLUSIONS

Common methods to distinguish the diagnoses of toxoplasmosis and CNS lymphoma are addressed. There should be a high index of suspicion for toxoplasmosis in patients with HIV/AIDS presenting with a focal intramedullary spinal cord lesion.

Usefulness of paired samples for the Serodiagnosis of toxoplasmosis infection in a tertiary teaching Hospital in Malaysia

BACKGROUND

Accurate diagnosis of Toxoplasma gondii (T. gondii) infection remains elusive and requires a comprehensive assessment through laboratory and clinical investigation. In this study, a diagnostic algorithm based on paired serum samples and clinical data was developed and evaluated.

METHODS

A total of 1267 suspected cases of Toxoplasma infection were enrolled in this study from January 2016 to December 2016. The cases were screened for anti-Toxoplasma IgM and IgG by electrochemiluminiscence immunoassay (ECLIA) method. Based on the serological profiles, all cases with first seropositive serum samples were considered as suggestive cases of Toxoplasma infection. Thus, second serum samples were obtained after an interval of 2 weeks. The diagnosis was made based on laboratory results and clinical data.

RESULTS

A total of 482 T. gondii seroreactive cases were selected. The patient's records were traced and the data were analysed. Accordingly, 152 cases were diagnosed as clinically confirmed cases; 198 cases were clinically asymptomatic and 132 cases were newborn babies or infants who did not have toxoplasmosis and only acquired passive immunity from their mothers. The paired serum algorithm allowed classifying the seroreactive cases as follows: early (0.6%), acute (1.9%), reactivation (13.5%), recent (1.5%), passive immunity from mother (27.3%) and possible congenital infections (1.2%). In addition, cases of reactivated toxoplasmosis were detected among the pregnant mothers (13/82; 15.8%), children aged above 1 year (2/8; 25.0%) and immunocompetent mothers (5/135; 3.7%). Furthermore, the application of the paired serum analysis resulted in remarkably improved treatment initiation.

CONCLUSIONS

Toxoplasmosis diagnosis and treatment can be improved through the use of paired serum diagnostic algorithm.

Advances in serological, imaging techniques and molecular diagnosis of Toxoplasma gondii infection

BACKGROUND

Toxoplasmosis is worldwide distributed zoonotic infection disease with medical importance in immunocompromised patients, pregnant women and congenitally infected newborns. Having basic information on the traditional and new developed methods is essential for general physicians and infectious disease specialists for choosing a suitable diagnostic approach for rapid and accurate diagnosis of the disease and, consequently, timely and effective treatment.

METHODS

We conducted English literature searches in PubMed from 1989 to 2016 using relevant keywords and summarized the recent advances in diagnosis of toxoplasmosis.

RESULTS

Enzyme-linked immunosorbent assay (ELISA) was most used method in past century. Recently advanced ELISA-based methods including chemiluminescence assays (CLIA), enzyme-linked fluorescence assay (ELFA), immunochromatographic test (ICT), serum IgG avidity test and immunosorbent agglutination assays (ISAGA) have shown high sensitivity and specificity. Recent studies using recombinant or chimeric antigens and multiepitope peptides method demonstrated very promising results to development of new strategies capable of discriminating recently acquired infections from chronic infection. Real-time PCR and loop-mediated isothermal amplification (LAMP) are two recently developed PCR-based methods with high sensitivity and specificity and could be useful to early diagnosis of infection. Computed tomography, magnetic resonance imaging, nuclear imaging and ultrasonography could be useful, although their results might be not specific alone.

CONCLUSION

This review provides a summary of recent developed methods and also attempts to improve their sensitivity for diagnosis of toxoplasmosis. Serology, molecular and imaging technologies each has their own advantages and limitations which can certainly achieve definitive diagnosis of toxoplasmosis by combining these diagnostic techniques.

Knowledge and Practices of Toxoplasmosis among Clinical Laboratory Professionals: A Cross-Sectional Study in Durango, Mexico

Background: The aim of this study was to determine the level of knowledge and practices about toxoplasmosis in a sample of clinical laboratory professionals in Mexico. Methods: 192 clinical laboratory professionals were surveyed. They were asked about (1) Toxoplasma gondii; (2) clinical manifestations, diagnosis, treatment, and epidemiology of toxoplasmosis; and (3) their practices with respect to toxoplasmosis. Results: The range of animals infected by T. gondii was known by 44.8% of participants. Clinical aspects of toxoplasmosis were known by up to 44.3% of subjects. Correct answers about the interpretation of serological markers of T. gondii infection were provided by up to 32.8% of participants. A minority (32.2%) of participants knew about a high number of false positive results of anti-T. gondii IgM antibody tests. Most participants (90.1%) did not know what the anti-T. gondii IgG avidity test was. Up to 55.7% of participants provided incorrect answers about the interpretation of serology tests for the treatment of pregnant women. Common routes of T. gondii infection were known by <15% of participants. Most (84.4%) participants had not performed tests for detection T. gondii infection. Conclusions: Results indicate incomplete knowledge of T. gondii infection and toxoplasmosis and a limited practice of laboratory tests among the professionals surveyed.

Nanomedicine advances in toxoplasmosis: diagnostic, treatment, and vaccine applications

Toxoplasmosis is an infectious disease caused by the intracellular parasite Toxoplasma gondii that affects about one third of the world's population. The diagnosis of this disease is carried out by parasite isolation and host antibodies detection. However, the diagnosis presents problems in regard to test sensitivity and specificity. Currently, the most effective T. gondii treatment is a combination of pyrimethamine and sulfadiazine, although both drugs are toxic to the host. In addition to the problems that compromise the effective diagnosis and treatment of toxoplasmosis, there are no reports or indications of any vaccine capable of fully protecting against this infection. Nanomaterials, smaller than 1000 nm, are currently being investigated as an alternative tool in the management of T. gondii infection. This article reviews how recent nanotechnology advances indicate the utility of nanomaterials in toxoplasmosis diagnosis, treatment, and vaccine development.

Pathogens of Food Animals: Sources, Characteristics, Human Risk, and Methods of Detection

Pathogens associated with food production (livestock) animals come in many forms causing a multitude of disease for humans. For the purpose of this review, these infectious agents can be divided into three broad categories: those that are associated with bacterial disease, those that are associated with viruses, and those that are parasitic in nature. The goal of this chapter is to provide the reader with an overview of the most common pathogens that cause disease in humans through exposure via the food chain and the consequence of this exposure as well as risk and detection methods. We have also included a collection of unusual pathogens that although rare have still caused disease, and their recognition is warranted in light of emerging and reemerging diseases. These provide the reader an understanding of where the next big outbreak could occur. The influence of the global economy, the movement of people, and food makes understanding production animal-associated disease paramount to being able to address new diseases as they arise.