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

Immediate versus deferred antiretroviral therapy in HIV-infected patients presenting with acute AIDS-defining events (toxoplasmosis, Pneumocystis jirovecii-pneumonia): a prospective, randomized, open-label multicenter study (IDEAL-study)

BACKGROUND

To evaluate clinical outcomes after either immediate or deferred initiation of antiretroviral therapy in HIV-1-infected patients, presenting late with pneumocystis pneumonia (PCP) or toxoplasma encephalitis (TE).

METHODS

Phase IV, multicenter, prospective, randomized open-label clinical trial. Patients were randomized into an immediate therapy arm (starting antiretroviral therapy (ART) within 7 days after initiation of OI treatment) versus a deferred arm (starting ART after completing the OI-therapy). All patients were followed for 24 weeks. The rates of clinical progression (death, new or relapsing opportunistic infections (OI) and other grade 4 clinical endpoints) were compared, using a combined primary endpoint. Secondary endpoints were hospitalization rates after completion of OI treatment, incidence of immune reconstitution inflammatory syndrome (IRIS), virologic and immunological outcome, adherence to proteinase-inhibitor based antiretroviral therapy (ART) protocol and quality of life.

RESULTS

61 patients (11 patients suffering TE, 50 with PCP) were enrolled. No differences between the two therapy groups in all examined primary and secondary endpoints could be identified: immunological and virologic outcome was similar in both groups, there was no significant difference in the incidence of IRIS (11 and 10 cases), furthermore 9 events (combined endpoint of death, new/relapsing OI and grade 4 events) occurred in each group.

CONCLUSIONS

In summary, this study supports the notion that immediate initiation of ART with a ritonavir-boosted proteinase-inhibitor and two nucleoside reverse transcriptase inhibitors is safe and has no negative effects on incidence of disease progression or IRIS, nor on immunological and virologic outcomes or on quality of life.

Prevalence of Toxoplasma gondii parasite in captive Mexican jaguars determined by recombinant surface antigens (SAG1) and dense granular antigens (GRA1 and GRA7) in ELISA-based serodiagnosis

Toxoplasma gondii is an obligate intracellular protozoan parasite that infects almost all warm-blooded animals, including humans, causing serious public health problems. In this study, the seroprevalence of T. gondii in captive jaguars in 10 Mexican zoos was determined using single and mixtures of recombinant surface antigens (SAG1) and dense granular antigens (GRA1 and GRA7) in immunoglobulin G (IgG) enzyme-linked immunosorbent assays (ELISAs). Their efficacy was compared with the tachyzoite lysate antigen. All recombinant antigens were characterised by high sensitivity (92.5-97.5%); the specificity of the IgG ELISAs was variable (83.3-91.6%). Mixtures of the two recombinant proteins were generally more reactive than single antigens. GRA7 + SAG1 showed the highest sensitivity (97.5%) and specificity (91.6%), almost perfect agreement (96.2%), and a kappa value of 0.89. An area under the curve value of 0.998 represented a highly accurate test with a cutoff value of 0.8. The seroprevalence of anti-T. gondii IgG antibodies in the single and mixed recombinant antigen ELISAs was 75.0-76.9%. This study shows that GRA7 + SAG1 can be successfully used to diagnose T. gondii infection in jaguars for effective monitoring of prevalence and for devising control methods and prevention strategies against toxoplasmosis.

Diagnosis of Candida albicans: conventional diagnostic methods compared to the loop-mediated isothermal amplification (LAMP) assay

Candida species cause a wide range of opportunistic infections in humans and animals. The detection of Candida species by conventional diagnosis methods is costly and time consuming. This study was conducted for the first time to evaluate and compare a relatively new molecular assay and the loop-mediated isothermal amplification (LAMP) technique with conventional methods for detection of Candida albicans. In this study, 70 different species of Candida identified by conventional methods were cultured on Sabouraud chloramphenicol agar medium and then the genomic DNA was extracted. The LAMP technique was performed using specific primers targeting the ITS2 gene of C. albicans. The analytical sensitivity and specificity of LAMP were measured using a tenfold serial dilution prepared from extracted DNA from standard C. albicans strain from 1 ng to 1 fg and the DNA samples of other clinical Candida species and three non-Candida yeast. Out of 70 yeast samples analyzed by LAMP technique, 24 samples (34.3%) were positive for C. albicans. Comparison of the results showed that the CHROMagar Candida and germ tube production methods are quite consistent with the LAMP technique, while the agreement amount between the results of carbohydrate assimilation and chlamydoconidia generation assays and LAMP technique was 98.5% and 72.8%, respectively. The detection limits of the LAMP assay were 10 fg of the DNA from the standard C. albicans strain. No amplification was observed in the DNA samples of other yeast species and only the DNA sample of standard C. albicans strain was amplified. Based on the results, it can be concluded that the LAMP method is as specific and precise as common diagnostic methods, but is faster, easier deployable or more sensitive. Therefore, this method can be used as a suitable complementary assay for Candida diagnosis in medical diagnostic laboratories and field conditions.

Acute Toxoplasma infection in pregnant women worldwide: A systematic review and meta-analysis

BACKGROUND

Acute Toxoplasma infection (ATI) during pregnancy, if left untreated, can cause severe adverse outcomes for the fetus and newborn. Here, we undertook a meta-analysis to estimate the worldwide prevalence of ATI in pregnant women.

METHODS

We searched international databases for studies published between January 1988 and November 2018. We included population-based cross-sectional and prospective cohort studies that reported the prevalence of ATI in pregnant women. Data were synthesized using a random effect model to calculate the overall prevalence of ATI (with a 95% CI) in six WHO regions and globally. We also performed linear meta-regression analyses to investigate associations of maternal, socio-demographic, geographical and climate parameters with the prevalence of ATI.

RESULTS

In total, 217 studies comprising 902,228 pregnant women across 74 countries were included in the meta-analysis. The overall prevalence of ATI in pregnant women globally was 1.1% (95% CI: 0.9-1.2%). In studies where more strict criteria for ATI were used, the overall prevalence was 0.6% (95% CI: 0.4-0.7%). The prevalence was highest in the Eastern Mediterranean region (2.5%; 95%CI: 1.7-3.4%) and lowest in the European region (0.5%; 95% CI: 0.4-0.7%). A significantly higher prevalence of ATI was found in countries with lower income levels (P = 0.027), lower human development indices (P = 0.04), higher temperatures (P = 0.02) and lower latitudes (P = 0.005) and longitudes (P = 0.02).

CONCLUSIONS

The risk of acquiring ATI during gestation is clinically important and preventive measures to avoid exposure of pregnant women to Toxoplasma infection should be strictly applied.

High-resolution melt curve analysis: A real-time based multipurpose approach for diagnosis and epidemiological investigations of parasitic infections

BACKGROUND

Real-time PCR coupled with high resolution melting curve analysis is a practical technique that could be employed in multipurpose studies. During the recent decade, this technique has been practiced for different targets, worldwide.

METHODS

In the current study three major database centers consisted of PubMed, Scopus and Web of Science were searched until Aug 2019 for applications of HRM real-time PCR in parasitology studies using terms: "Parasite" AND "HRM real-time PCR" OR "High Resolution Melting curve analysis" OR "Real-time PCR", "Protozoan parasites" AND "HRM real-time PCR" OR "High Resolution Melting curve analysis" OR "Real-time PCR", "Helminth" AND "HRM real-time PCR" OR "High Resolution Melting curve analysis" OR "Real-time PCR".

RESULTS

Totally, 83 papers met our criteria and were included in our study. This method was more frequently used for protozoan parasites (52/83; 62.65%), while lower (31/83; 37.35%) studies were incorporated on helminths parasites. Furthermore, Plasmodium spp., and Leishmania spp., were the most prevalent protozoan parasites, and Taenia spp., and filers were the most frequent helminths that were studied by HRM real-time PCR.

CONCLUSION

HRM real-time PCR is a sensitive, flexible and cost-effective method that could be used for multipurpose studies.

Molecular genotyping and serological evaluation of Toxoplasma gondii in mothers and their spontaneous aborted fetuses in Southwest of Iran

BACKGROUND

Given the lack of routine screening and the high prevalence of toxoplasmosis in pregnant women in Iran, the current study aimed to find out the rate and features of Toxoplasma gondii infection in the spontaneously aborted human fetuses in Kohgiluyeh and Boyer-Ahmad Province, Southwestern Iran.

METHODS

This cross-sectional study was performed on 100 spontaneously aborted fetuses' tissues and their mother blood samples. The mothers' sera were evaluated for anti-Toxoplasma antibodies while their buffy coat and aborted fetuses tissues were evaluated for Toxoplasma DNA. PCR product at GRA6 locus was sequenced and phylogenetic analysis was done. Likewise, quantitative Real-Time PCR was performed to find out the parasite burdens in mothers buffy coat and fetuses tissues.

RESULTS

Using serological method, anti-Toxoplasma IgG and IgM antibodies were detected in 7 (7%) and 3 (3%) out of 100 sera from women with spontaneous abortion. Real-time PCR method detected T. gondii DNA in the buffy coat of one seronegative and 2 (out of 3) IgM seropositive cases. None of the samples from aborted fetuses were infected with T. gondii. BLAST and phylogenetic analysis showed that the sequenced isolates belonged to type I of T. gondii and two identified T. gondii isolates were taxonomically grouped into one clade.

CONCLUSION

Our findings revealed type I genotype of T. gondii in two mothers with spontaneous abortion, without fetus involvement. It is necessary to examine more aborted fetuses' samples from different geographical areas to determine the association between Toxoplasma genotype and abortion.

The first study on the usefulness of recombinant tetravalent chimeric proteins containing fragments of SAG2, GRA1, ROP1 and AMA1 antigens in the detection of specific anti-Toxoplasma gondii antibodies in mouse and human sera

This study presents an evaluation of four tetravalent recombinant chimeric proteins containing fragments of the Toxoplasma gondii antigens, SAG2, GRA1, ROP1 and AMA1, as potential replacements of a the soluble, whole-cell tachyzoite lysate (TLA) used in serological assays. Recombinant chimeric proteins (SAG2-GRA1-ROP1-AMA1N, AMA1N-SAG2-GRA1-ROP1, AMA1C-SAG2-GRA1-ROP1, and AMA1-SAG2-GRA1-ROP1) obtained by genetic engineering were tested for their reactivity with specific IgM and IgG antibodies from sera of experimentally infected mice and humans with T. gondii infection using an enzyme-linked immunosorbent assay (ELISA). In total 192 serum samples from patients with acquired T. gondii infection and 137 sera from seronegative individuals were examined. The reactivity of chimeric antigens with antibodies generated during T. gondii invasion was measured and compared to the results obtained in assays based on whole-cell Toxoplasma antigen. Chimeric proteins proved effective in differentiation between T. gondii-infected and uninfected individuals (100% sensitivity and specificity in the IgG ELISAs) which shows their potential usefulness as a replacements for TLA in standardized commercial tests for the serodiagnosis of toxoplasmosis. In addition, the chimeric proteins were tested for use in avidity determination. Obtained results were comparable to those of the corresponding commercial assays, suggesting the utility of these proteins for avidity assessment. Furthermore, this study demonstrated that the AMA1-SAG2-GRA1-ROP1 chimeric protein has the potential to distinguish specific antibodies from serum samples of individuals with the early and chronic phase of T. gondii infection.

Serological and molecular screening of umbilical cord blood for Toxoplasma gondii infection

BACKGROUND

Human umbilical cord blood has proven to be a successful alternate source of hematopoietic stem cells for pediatric patients with major hematologic disorders. Toxoplasma gondii is a global opportunistic protozoan which cause fatal complications in immunocompromised individuals.

AIM

Our goal is to study the prevalence of toxoplasmosis in umbilical cord blood (UCB) and to assess the sensitivity of ELISA and PCR for Toxoplasma infection screening.

MATERIAL AND METHODS

One hundred cord blood samples were collected immediately after delivery. Anti-Toxoplasma IgG and IgM antibodies were determined using ELISA method; Toxoplasma DNA was detected using nested PCR technique. Total nucleated cells (TNC) and HB were also determined. Demographic data and risk factors data related to the transmission of toxoplasmosis, were collected from mothers.

RESULTS

Among 100 cord blood samples, 36 (36%) were positive for anti-Toxoplasma IgG antibodies and 6 (6%) were positive for anti-Toxoplasma IgM antibodies. The nested PCR showed 11 (11%) samples containing Toxoplasma DNA from which, 6 (55%) samples were IgM positive. There was no significant association between the risk of Toxoplasma transmission and cord blood positivity for toxoplasmosis.

CONCLUSION

Owing to the prevalence of toxoplasmosis, its rapid progression and its fatal outcome in immunocompromised patients, cord blood screening for toxoplasmosis with nested PCR should be incorporated into cord blood bank screening protocols.

Validation of Multiplex Serology for human hepatitis viruses B and C, human T-lymphotropic virus 1 and Toxoplasma gondii

Multiplex Serology is a high-throughput technology developed to simultaneously measure specific serum antibodies against multiple pathogens in one reaction vessel. Serological assays for hepatitis B (HBV) and C (HCV) viruses, human T-lymphotropic virus 1 (HTLV-1) and the protozoan parasite Toxoplasma gondii (T. gondii) were developed and validated against established reference assays. For each pathogen, between 3 and 5 specific antigens were recombinantly expressed as GST-tag fusion proteins in Escherichia coli and tested in Monoplex Serology, i.e. assays restricted to the antigens from one particular pathogen. For each of the four pathogen-specific Monoplex assays, overall seropositivity was defined using two pathogen-specific antigens. In the case of HBV Monoplex Serology, the detection of past natural HBV infection was validated based on two independent reference panels resulting in sensitivities of 92.3% and 93.0%, and specificities of 100% in both panels. Validation of HCV and HTLV-1 Monoplex Serology resulted in sensitivities of 98.0% and 95.0%, and specificities of 96.2% and 100.0%, respectively. The Monoplex Serology assay for T. gondii was validated with a sensitivity of 91.2% and specificity of 92.0%. The developed Monoplex Serology assays largely retained their characteristics when they were included in a multiplex panel (i.e. Multiplex Serology), containing additional antigens from a broad range of other pathogens. Thus HBV, HCV, HTLV-1 and T. gondii Monoplex Serology assays can efficiently be incorporated into Multiplex Serology panels tailored for application in seroepidemiological studies.

Seroprevalence and molecular detection of Toxoplasma gondii in healthy blood donors in southwest Iran

BACKGROUND

Toxoplasmosis is a cosmopolitan parasitic disease caused by Toxoplasma gondii (T. gondii). Blood transfusion is a probable route of T. gondii transmission. Due to lack of information about seroprevalence of T. gondii in healthy blood donors, this study was aimed to determine the chronic and acute infection using serological and molecular methods.

MATERIAL AND METHODS

In this cross-sectional investigation, 380 samples were collected from donated bloods. Anti-Toxoplasma IgG and IgM antibodies were examined using enzyme-linked immunosorbent assay (ELISA). Also, all IgG positive samples were tested by IgG avidity test. Eventually, to detection of active infection, DNA was extracted from IgM positive and low IgG avidity samples and then tested using nested-polymerase chain reaction (PCR).

RESULTS

Among 380 blood donors, 131 (34.47%) were positive for only anti-T. gondii IgG, 2 (0.5%) were positive for only anti-T. gondii IgM, and 11 (2.9%) were positive for both IgG and IgM antibodies. Then, 142 samples (131 IgG ⁺ and 11 IgG ⁺IgM ⁺) were evaluated using IgG avidity test. Of these, 115 (81%) had high avidity IgG indicates past infection; 16 (11.26%) had low avidity IgG representing recent infection, and 11 (7.74%) were equivocal. With nested PCR, 20 samples of 50 seropositive samples were diagnosed positive.

CONCLUSION

Detected active infection using nested-PCR draws attention to the possibility of T. gondii infection via blood transfusion which emphasizes the importance of parasite DNA screening before donation of blood in high risk groups such as: multi-transfused persons, immunosuppressed patient, and pregnant women.

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.

Seroepidemiological evaluation of Toxoplasma gondii immunity among the general population in southwest of Iran

Toxoplasmosis is a cosmopolitan zoonotic infection, caused by a unicellular protozoan parasite known as Toxoplasma gondii (T. gondii) that belongs to the phylum Apicomplexa. The present investigation was aimed to evaluate the seroprevalence of T. gondii infection in the general population of Abadan city. In this cross-sectional study, a total of 496 subjects were participated. Anti-T. gondii IgG and IgM antibodies were tested using commercially available enzyme-linked immunosorbent assay (ELISA). Moreover, a structured questionnaire was completed for each person. Out of 496 subjects, 188 (37.9%) and 30 (6.05%) samples were seropositive for IgG and IgM, respectively. The more seroprevalence was found during spring season, among female subjects, in rural inhabitants, in persons with the education level of diploma or lower, from the subjects with a history of contact with cat, in individuals who consumed raw/undercooked meat, and amongst who drink unpurified water. The results showed that inhabitants of tropical areas, may be moderately exposed to T. gondii. Increase of knowledge of people about toxoplasmosis, certainly affects in reduction of the infection.

Screening of toxoplasmosis in cancer patients: a concern

Toxoplasmosis is an opportunistic infectious disease in immunocompromised patients, including cancer patients, whose detection is by molecular and serological methods. A total of 106 blood samples from patients with different types of cancer were evaluated for anti- Toxoplasma gondii IgG and IgM antibodies by the enzyme-linked immunosorbent assay (ELISA) and the parasite DNA by nested polymerase chain reaction (PCR). These were detected in 41.51% (44/106) and 0.94% (1/106), respectively, but T. gondii IgM antibody was not detected at all. These results suggest that the screening of toxoplasmosis should be considered more routinely in cancer patients.

Recent progress in microneme-based vaccines development against Toxoplasma gondii

Toxoplasmosis is a cosmopolitan zoonotic disease, which infect several warm-blooded mammals. More than one-third of the human population are seropositive worldwide. Due to the high seroprevalence of Toxoplasma gondii infection worldwide, the resulting clinical, mental, and economical complications, as well as incapability of current drugs in the elimination of parasites within tissue cysts, the development of a vaccine against T. gondii would be critical. In the past decades, valuable advances have been achieved in order to identification of vaccine candidates against T. gondii infection. Microneme proteins (MICs) secreted by the micronemes play a critical role in the initial stages of host cell invasion by parasites. In this review, we have summarized the recent progress for MIC-based vaccines development, such as DNA vaccines, recombinant protein vaccines, vaccines based on live-attenuated vectors, and prime-boost strategy in different mouse models. In conclusion, the use of live-attenuated vectors as vehicles to deliver and express the target gene and prime-boost regimens showed excellent outcomes in the development of vaccines against toxoplasmosis, which need more attention in the future studies.