Challenging TaqMan probe-based real-time PCR and loop-mediated isothermal amplification (LAMP): the two sensitive molecular techniques for the detection of toxoplasmosis, a potentially dangerous opportunistic infection in immunocompromised patients

Comparison of B1 and RE 529 gene targets by real time PCR and LAMP assay for diagnosis of toxoplasmosis in pregnant females

PURPOSE

The aim of this study is to accurately diagnose the presence of toxoplasmosis in pregnant women. In this study we evaluated two gene targets B1 and RE-529 using two different molecular methods i.e., real-time PCR and LAMP.

PROCEDURE

A total of 150 blood samples were collected from pregnant women attending the PGIMER outpatient clinic. The serum and Buffy layer were extracted and various serological (ELISA) and molecular tests (qPCR and LAMP) targeting B1 and RE-529 were carried out.

FINDING

Out of 150 patients, 32 were seropositive. Amongst which for the RE-529 gene, 18 were LAMP positive and 16 were qPCR positive, while for the B1 gene, 14 were LAMP positive and 13 were qPCR positive.

CONCLUSIONS

Molecular methods were more sensitive than serological tests to diagnose congenital toxoplasmosis in antenatal females. Few seronegative patients were reported positive using molecular methods. In addition, LAMP targeting the RE-529 gene is more sensitive than qPCR, and LAMP targets the B1 gene.

Latent toxoplasmosis in COVID-19 patients and link with higher mortality in COVID-19 male patients

BACKGROUND

Immunocompromised patients may be at risk for reactivating the toxoplasmosis infection; therefore, early diagnosis would be highly desirable in these individuals. This study evaluated the possible association between coronavirus disease 2019 (COVID-19) and latent Toxoplasma gondii infection in Guilan province, Iran.

MATERIALS AND METHODS

The study was performed among 210 COVID-19 patients referred to Guilan University of Medical Sciences hospitals in 2022. Peripheral blood samples were taken for serum separation, collected into tubes, and kept at - 20 °C until use. Blood samples were obtained from COVID-19 patients. IgG antibody to Toxoplasma gondii was detected by a commercial ELISA kit. Accordingly, IgG absorbance levels <9 were considered harmful, 9-11 was considered borderline, and >11 was positive.

RESULTS

Toxoplasma IgG antibodies were found in 73.9 % of patients with COVID-19 in male patients. The seroprevalence of Toxoplasma in dead and lived COVID-19 male patients was 83.3 % and 66.7 %, respectively, and this difference was significant. A present study found a significant correlation between the rising titer of Toxoplasma IgG and the severity of COVID-19. There was no significant difference between the hospitalization duration factor and the seropositivity rate.

CONCLUSION

Regarding the significant association between the rising titer of Toxoplasma IgG and the severity of COVID-19. The findings demonstrated an association between the severity and mortality rate of COVID-19 with higher titer Anti-Toxoplasma IgG antibodies. Toxoplasmosis is currently considered a risk factor for COVID-19.

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.

Molecular and serological diagnosis of toxoplasmosis: a systematic review and meta-analysis

Toxoplasmosis is an infection of vast worldwide distribution whose etiologic agent is Toxoplasma gondii. This disease can cause problems ranging from mild symptoms to serious conditions, such as encephalitis, miscarriage and blindness. Therefore, it is of utmost importance to perform a diagnosis with reproducible techniques in order to obtain a good prognosis. The aim of this review was to analyze the efficiency of toxoplasmosis diagnostic techniques based on sensitivity and specificity results. Five research platforms in English language were used (Eric, Elsevier, Google Scholar, PubMed and SciELO), which contained data on the diagnosis of toxoplasmosis. The search and selection were performed for studies published prior to June 2021. The search resulted in the inclusion of 13 articles published from 2005 to 2020. The data revealed the use of different samples in the standardization of techniques such as serum, total blood, colostrum and amniotic fluid. The flow cytometry, lateral flow immunoassay and qPCR techniques showed 100% sensitivity, whereas the ELISA, western blotting, qPCR and RE-LAMP techniques achieved 100% specificity. Significantly, the qPCR and LAMP techniques were more accurate when the likelihood ratio was assessed. The meta-analysis identified that ISAGA and western blotting have low sensitivity values and LIASON, ELFA and ELISA, using a silica bioconjugate, also have low specificity values. It was noted that a wide range of methods have high values of sensitivity and specificity. Therefore, the choice of the method will be based on the conditions and its financial viability.

Rapid and Visual Detection of Toxoplasma gondii in Blood Samples from Pet Cats and Dogs by Loop-Mediated Isothermal Amplification

Background: Toxoplasma gondii is an obligate intracellular parasite that invades nearly all nucleated cells of a broad spectrum of vertebrate hosts, and which may cause serious disease in immunocompromised patients, as well as in the immunologically incompetent fetus. This study aimed to establish a loop-mediated isothermal amplification (LAMP) technique to rapidly detect T. gondii in the blood infection by targeting the 529 bp repeat element of T. gondii. Methods: A turbidity monitoring system, together with visual reagent, was used to test the amplification result of the LAMP assay. In addition, the specificity and sensitivity of the LAMP assay were measured. Results: The results suggest that the successfully established LAMP assay profile can detect the DNA of T. gondii at 67°C within 40 min. The limit of detection of the LAMP assay was 10¹ copies/μL. No cross reaction occurred with Plasmodium vivax, Toxocara cati, Clonorchis sinensi, Spirometra mansoni or Cryptosporidium parvum. We validated the developed LAMP assay by detecting T. gondii in DNA extracted from 353 blood samples collected from domestic cats and dogs. The percentages of positive results in detecting these blood samples by LAMP and conventional PCR were 5.38% and 2.83%, respectively. Conclusions: Our findings show that the developed LAMP assay offers higher analytical sensitivity than conventional PCR and good analytical specificity, minimizes aerosol contamination, and can be applied to on-site rapid detection of T. gondii.

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.

Novel biomarkers of microRNAs in gastric cancer; an overview from diagnosis to treatment

The fourth frequent disease in the world and the second cause of cancer-related death is gastric cancer (GC). In this way, over 80% of diagnoses are made in the middle to advanced degrees of the disease, underscoring the requirement for innovative biomarkers that can be identified quickly. Meaningly, biomarkers that can complement endoscopic diagnosis and be used to detect patients with a high risk of GC are desperately needed. These biomarkers will allow for the accurate prediction of therapy response and prognosis in GC patients, as well as the development of an optimal treatment strategy for each individual. Conspicoiusly, microRNAs (miRNAs) and small noncoding RNA regulates the expression of target mRNA and thereby modifies critical biological mechanisms. According to the data, abnormally miRNAs expression in GC is linked to tumor growth, carcinogenesis, aggression and distant metastasis. Importantly, miRNA expression patterns and next-generation sequencing (NGS) can also be applied to analyze kinds of tissues and cancers. Given the high death rates and poor prognosis of GC, and the absence of a clinical diagnostic factor that is adequately sensitive to GC, research into novel sensitive and specific markers for GC diagnosis is critical. In this review,we evaluate the latest research findings that suggest the feasibility and clinical utility of miRNAs in GC.

Molecular diagnosis of toxoplasmosis: recent advances and a look to the future

INTRODUCTION

Toxoplasmosis is a globally distributed parasitic infection that can be particularly severe when opportunistic or congenital. Its diagnosis requires accurate and rapid techniques that rely mainly on serology and molecular methods.

AREAS COVERED

The aim of this review was to discuss the positioning of the molecular diagnosis of toxoplasmosis according to the different clinical situations possibly resulting from infection with T. gondii, and to detail recent developments in this technique. The English and French literature were searched with the following keywords: 'Toxoplasmosis', "Molecular diagnosis" and 'PCR'.

EXPERT OPINION

Molecular techniques have revolutionized the diagnosis of toxoplasmosis, and practices have considerably evolved over the past decades. However, there is still a high degree of inter-laboratory heterogeneity which impairs comparisons between results and studies. Efforts to standardize practices are underway.

Development of a TaqMan loop-mediated isothermal amplification assay for the rapid detection of pigeon paramyxovirus type 1

Pigeon paramyxovirus-1 (PPMV-1) is a strain of Newcastle disease virus (NDV) that has adapted to infect pigeons and poses a constant threat to the commercial poultry industry. Early detection via rapid and sensitive methods, along with timely preventative and mitigating actions, is important for reducing the spread of PPMV-1. Here, we report the development of a TaqMan loop-mediated isothermal amplification assay (TaqMan-LAMP) for rapid and specific detection of PPMV-1 based on the F gene. This system makes use of six novel primers and a TaqMan probe that targets nine distinct regions of the F gene that are highly conserved among PPMV-1 isolates. The results showed that the limit of detection was 10 copies μL-1 for PPMV-1 cDNA and 0.1 ng for PPMV-1 RNA. The reaction was completed within 25 min and was thus faster than conventional RT-PCR. Moreover, no cross-reactions with similar viruses or with peste des petits ruminants virus (PPRV) or NDV LaSota vaccine strains were observed under the same conditions. To evaluate the applicability of the assay, the TaqMan-LAMP assay and a commercial RT-PCR assay were compared using 108 clinical samples, and the concordance rate between two methods was found to be 96.3%. The newly developed PPMV-1 TaqMan-LAMP assay can therefore be used for simple, efficient, rapid, specific, and sensitive diagnosis of PPMV-1 infections.

Biosensing Amplification by Hybridization Chain Reaction on Phase-Sensitive Surface Plasmon Resonance

Surface Plasmon Resonance (SPR) is widely used in biological and chemical sensing with fascinating properties. However, the application of SPR to detect trace targets is hampered by non-specific binding and poor signal. A variety of approaches for amplification have been explored to overcome this deficiency including DNA aptamers as versatile target detection tools. Hybridization chain reaction (HCR) is a high-efficiency enzyme-free DNA amplification method operated at room temperature, in which two stable species of DNA hairpins coexist in solution until the introduction of the initiator strand triggers a cascade of hybridization events. At an optimal salt condition, as the concentrations of H1 and H2 increased, the HCR signals were enhanced, leading to signal amplification reaching up to 6.5-fold of the detection measure at 30 min. This feature enables DNA to act as an amplifying transducer for biosensing applications to provide an enzyme-free alternative that can easily detect complex DNA sequences. Improvement of more diverse recognition events can be achieved by integrating HCR with a phase-sensitive SPR (pSPR)-tested aptamer stimulus. This work seeks to establish pSPR aptamer system for highly informative sensing by means of an amplification HCR. Thus, combining pSPR and HCR technologies provide an expandable platform for sensitive biosensing.

Accurate and rapid detection of Fasciola hepatica copro-DNA in sheep using loop-mediated isothermal amplification (LAMP) technique

Fascioliasis is a parasitic infection caused by Fasciola spp. in humans and animals. Despite significant advances in vaccination and new therapeutic agents, little attention has been paid to validate methods for the diagnosis of fascioliasis in animals. This study aimed to compare the loop‐mediated isothermal amplification (LAMP) technique with PCR assay for the diagnosis of F. hepatica in sheep. In this cross‐sectional study, 195 stool samples were collected from sheep for 3 months in Lorestan province, West of Iran. Specimens’ parasitological examination was performed by using the direct wet mount and formalin‐ether concentration method. After DNA extraction from the samples, molecular analysis was done using PCR and LAMP techniques based on the Fasciola ribosomal intergenic spacer (IGS) sequence. Of 195 specimens of sheep, 11 specimens were identified as F. hepatica‐positive infection by using microscopic, PCR and LAMP assays. Kappa agreement test results showed that there was a significant agreement between the results of microscopic examination diagnostic tests, PCR and LAMP (Kappa = 0.51–0.72 and p < .001). According to the results of chi‐square comparisons between parasite prevalence applying different techniques and variables of age, sex breed, and type of drinking water, there was no significant relationship (p ≥ .05). However, most of the infected sheep with Fasciola were 3‐ to 4‐year‐old females, of the Lori breed and consumed tap water. In many endemic areas, successful prevention and treatment of fascioliasis in animals depend on rapid and accurate diagnosis. Based on the results of the Kappa agreement, the significant agreement among the results of the microscopic examination, PCR and LAMP indicates the accuracy and reliability of these tests in the diagnosis of F. hepatica in sheep. However, molecular methods, especially the LAMP technique, are suggested because of their higher sensitivity and reliability for the diagnosis of F. hepatica even under field conditions.

Toxoplasmosis after allogeneic haematopoietic cell transplantation-disease burden and approaches to diagnosis, prevention and management in adults and children

BACKGROUND

Toxoplasmosis is a rare but highly lethal opportunistic infection after allogeneic haematopoietic cell transplantation (HCT). Successful management depends on screening, early recognition and effective treatment.

OBJECTIVES

To review the current epidemiology and approaches to diagnosis, prevention and treatment of toxoplasmosis in adult and paediatric allogeneic HCT recipients.

SOURCE

Search of the English literature published in MEDLINE up to 30 June 2020 using combinations of broad search terms including toxoplasmosis, transplantation, diagnosis, epidemiology, prevention and treatment. Selection of articles for review and synthesis on the basis of perceived quality and relevance of content.

CONTENT

Toxoplasmosis continues to be a major challenge in the management of allogeneic HCT recipients. Here we provide a summary of published case series of toxoplasmosis in adult and paediatric patients post allogeneic HCT. We review and discuss the pathogenesis, epidemiology, clinical presentation, diagnosis and current recommendations for prevention and treatment. We also discuss impacts of toxoplasmosis in this setting and factors affecting outcome, emphasizing attention to neurological, neuropsychological and neurocognitive late effects in survivors.

IMPLICATIONS

Apart from careful adherence to established strategies of disease prevention through avoidance of primary infection, identification of seropositive patients and implementation of molecular monitoring, future perspectives to improve the control of toxoplasmosis in allogeneic HCT recipients may include the systematic investigation of pre-emptive treatment, development of immunomodulatory approaches, antimicrobial agents with activity against the cyst form and vaccines to prevent chronic infection.

A loop-mediated isothermal amplification (LAMP) assay for detection of Toxoplasma gondii infection in women with spontaneous abortion

The present study aimed to use the loop-mediated isothermal amplification (LAMP) technique in comparison with serological tests to determine the rate of T. gondii infection in women suffering from spontaneous abortion (SA). A total of 140 women suffering from their first SA were included in this study. The collected aborted fetal remains and blood samples from each patient were examined in sterilized conditions using the LAMP technique and ELISA. Of the 140 women, 80 (57.1%) tested seropositive for anti-Toxoplasma antibodies by ELISA, 72 (51.4%) women tested seropositive for the IgG antibody, 8 (5.7%) tested seropositive for the IgM antibody. Among the eight women who'd had their first SA who tested seropositive for IgM antibody by ELISA, only five cases (62.5%) reported positively to the LAMP test. The difference in the frequency distribution of the LAMP results for measuring the Toxoplasma infection in pregnant women under study was statistically significant (P < 0.001) from the results of the serological test (ELISA). Although there was a significant difference between age and positivity in the LAMP test (P = 0.017), no significant difference was observed between positivity in the LAMP test and other variables. The findings of the present investigation suggest that LAMP is a preferred method for determining Toxoplasma infection in pregnant women suffering from SA compared with other routine serological tests. Even in a field with limited facilities and equipment, this technique can be effective and efficient in accurately and specifically diagnosing Toxoplasma infections in women at high risk of SA.