PCR-based diagnosis is not always useful in the acute acquired toxoplasmosis in immunocompetent individuals

Latent Toxoplasma gondii infection and associated risk factors among patients with chronic kidney disease: a registry-based study

BACKGROUND

Patients with chronic kidney disease (CKD) are susceptible to acquiring opportunistic parasites due to acquired immunodeficiency caused by uremia. Therefore, the present case-control study attempted to determine the prevalence of T. gondii infection and also associated risk factors among patients with CKD under hemodialysis and healthy controls who were registered at the Iranian National Registry Center for Toxoplasmosis (INRCT) in Mazandaran Province, northern Iran.

METHODS

212 cases with CKD and 200 healthy controls were enrolled in this study. Informed consent as well as a questionnaire were obtained from all subjects. Blood samples were collected from each participant and the serum was screened for anti-Toxoplasma antibodies (IgG and IgM). PCR assay was performed to detect circulating T. gondii in the blood samples of patients and controls using the primer pair targeting the RE gene.

RESULTS

Out of 412 participants, 67.92% of patients and 15.5% of control subjects were positive for anti-Toxoplasma IgG, but all participants were negative for anti-Toxoplasma IgM. Also, considering PCR assays with RE target, the prevalence of T. gondii infection was 24.1% in case subjects, while none of the control subjects tested positive. Among the PCR positive, 34 (66.7%) had Toxoplasma IgG positivity. The results from the multiple multinomial logistic regression revealed that the seroprevalence of anti-T. gondii IgG antibodies in patients with CKD was 3.12 times higher than in healthy controls (OR = 3.12; 95% CI = 0.43, 14.8; P < 0.001). Also, there was a significant association between seroprevalence of T. gondii infection and age, having a cat at home, and level of glomerular filtration rate (GFR) in these patients.

CONCLUSION

Our findings demonstrate a highly significant association between latent T. gondii infection and CKD, mostly in the late stages. Thus, regular screening for T. gondii infection in these patients is strongly recommended to prevent the reactivation of latent infections. A combination of serological screening, chemoprophylaxis, and PCR follow-up for patients at risk of reactivation should effectively reduce the likelihood of latent infection reactivation.

CLINICAL TRIAL NUMBER

Not applicable.

The Potential Association Between Latent Toxoplasma Gondii Infection and Opioid Abuse: A Registry-Based Sero-Molecular Case-Control Study

Toxoplasma gondii is a ubiquitous parasitic protozoan that can cause neurological and psychiatric disorders, potentially impacting human emotional behavior. This study aimed to explore serological and molecular evidence of T. gondii infection in opioid abusers in northern Iran. In this case-control study, opioid abusers who were referred to substance abuse rehabilitation centers in Mazandaran Province, northern Iran, were enrolled. Blood samples were collected from the participants to perform a serological assay to detect T. gondii IgG and IgM antibodies. A polymerase chain reaction (PCR) test was also conducted on buffy coats of the blood samples. The study comprised a total of 474 participants, with 239 individuals being opioid abusers and 235 healthy individuals serving as the control group. The results indicated that 163 opioid abusers (68.2%) were positive for T. gondii IgG, whereas 76 (31.8%) were negative. Among the control group, 63 individuals (26.8%) tested positive for T. gondii IgG, whereas 172 (73.2%) tested negative. This difference was statistically significant according to p = 0.01, odds ratio (OR) = 2.67, and 95% confidence interval (CI) = 1.03-4.15. In addition, 7.1% (17/239) of the case and 2.1% (5/235) of the control groups were PCR positive for Toxoplasma DNA. This difference was statistically significant (p = 0.01; OR = 2.96; 95%; CI = 0.94-7.01). In contrast, all of the participants were negative for T. gondii IgM antibodies. Our findings demonstrated that the sero-molecular prevalence of latent T. gondii infection in opioid abusers is significantly higher than that in healthy individuals. This suggests a potential correlation between T. gondii IgG antibody positivity and PCR results with opioid abuse.

Guidelines for the management of Toxoplasma gondii infection and disease in patients with haematological malignancies and after haematopoietic stem-cell transplantation: guidelines from the 9th European Conference on Infections in Leukaemia, 2022

Patients with haematological malignancies might develop life-threatening toxoplasmosis, especially after allogeneic haematopoietic stem-cell transplantation (HSCT). Reactivation of latent cysts is the primary mechanism of toxoplasmosis following HSCT; hence, patients at high risk are those who were seropositive before transplantation. The lack of trimethoprim-sulfamethoxazole prophylaxis and various immune status parameters of the patient are other associated risk factors. The mortality of toxoplasma disease-eg, with organ involvement-can be particularly high in this setting. We have developed guidelines for managing toxoplasmosis in haematology patients, through a literature review and consultation with experts. In allogeneic HSCT recipients seropositive for Toxoplasma gondii before transplant, because T gondii infection mostly precedes toxoplasma disease, we propose weekly blood screening by use of quantitative PCR (qPCR) to identify infection early as a pre-emptive strategy. As trimethoprim-sulfamethoxazole prophylaxis might fail, prophylaxis and qPCR screening should be combined. However, PCR in blood can be negative even in toxoplasma disease. The duration of prophylaxis should be a least 6 months and extended during treatment-induced immunosuppression or severe CD4 lymphopenia. If a positive qPCR test occurs, treatment with trimethoprim-sulfamethoxazole, pyrimethamine-sulfadiazine, or pyrimethamine-clindamycin should be started, and a new sample taken. If the second qPCR test is negative, clinical judgement is recommended to either continue or stop therapy and restart prophylaxis. Therapy must be continued until a minimum of two negative PCRs for infection, or for at least 6 weeks for disease. The pre-emptive approach is not indicated in seronegative HSCT recipients, after autologous transplantation, or in non-transplant haematology patients, but PCR should be performed with a high level of clinical suspicion.

Real-time PCR in the diagnosis of congenital toxoplasmosis

The diagnosis of congenital toxoplasmosis presents limitations and therefore new options are necessary. The analysis of amniotic fluid by real-time PCR has already proved effective for confirmation of fetal infection. However, its performance in other biological samples is not clear yet. The aim of this study is to better understand the role of real-time PCR in the blood of the mother and newborn as well as in the amniotic fluid and placenta in the diagnosis of congenital toxoplasmosis. This is a descriptive cohort study of pregnant women with toxoplasmosis followed up in Rio de Janeiro, Brazil. Real-time PCR was performed in samples of maternal blood, amniotic fluid, placenta, and blood of newborns. In addition, histopathological examination of placentas was performed, and data collected from babies were collected. 116 pregnant women were followed up and 298 samples were analyzed. One (0.9%) pregnant woman presented positive PCR in the blood, 3 (3.5%) in the amniotic fluid, 1 (2.3%) in the placenta and no newborn had positive PCR in the blood. Histopathological study was suggestive of toxoplasmosis infection in 24 (49%) placentas. Six (5.2%) newborns were diagnosed with congenital toxoplasmosis, and only cases with positive PCR in the amniotic fluid had correlation of the PCR result with the diagnosis of congenital infection. Both maternal and blood samples of newborns and placenta did not prove to be promising in the diagnosis of congenital toxoplasmosis. Further studies are needed to evaluate the real role of molecular diagnosis in other biological materials rather than the amniotic fluid.

Detection of persistent low IgG avidity-an interpretative problem in the diagnosis of acute toxoplasmosis

OBJECTIVES

For the proper diagnosis of toxoplasmosis it is essential to determine the stage of the infection, for which the most preferred method is IgG avidity test. The avidity index (AI) should initially be low (AI≤0.3) in the acute phase and increase during the infection. However, persistent low avidity can occur in patients with latent toxoplasmosis, which can complicate the interpretation of the results. The aim of the study is to explain the causes of this phenomenon.

METHODOLOGY

A retrospective study was carried out with 717 serum samples collected from 442 patients from the categories of pregnant and non-pregnant women, men, and newborns + infants (age < 0.5 year). The trends of AI kinetics were evaluated in repeatedly examined patients. The frequency of cases with low avidity was compared in individual categories of patients and in groups of people with acute and non-acute toxoplasmosis.

RESULTS

The proportion of patients with initially low avidity was 42.1% in the acute toxoplasmosis group while it was 13.0% in the non-acute groups. In uninfected newborns with anti-Toxoplasma antibodies transmitted from the mother, a decrease in IgG avidity levels over time was observed, resulting in 29.2% of samples showing low (improper) avidity. While the dynamics of IgG avidity and the frequency of cases of improperly low avidity were similar in men and pregnant and non-pregnant women, the category of newborns and infants differed substantially for these indicators.

CONCLUSIONS

Due to acceptable specificity and negative predictive value, high avidity can rule out acute toxoplasmosis, but moderate sensitivity complicates the possibility of its confirmation. The results of the avidity test must be interpreted in the context of the results of other methods.

Diagnostic Value of Circulating Antigens in the Serum of Piglets with Experimental Acute Toxoplasmosis

Toxoplasmosis, caused by Toxoplasma gondii, an apicomplexan parasite, infects all warm-blooded animals, including a third of the human population. Laboratory diagnosis of acute toxoplasmosis is based on the detection of anti-T. gondii IgM and IgG and T. gondii nucleic acid; however, these assays have certain limitations. Circulating Ags (CAgs) are reliable diagnostic indicators of acute infection. In this study, we established a model of acute T. gondii infection in Large White pigs. CAg levels peaked between 3 and 5 d after inoculation, and 28 CAgs were identified using an immunoprecipitation-shotgun approach, among which dolichol-phosphate-mannose synthase family protein (TgDPM), C3HC zinc finger-like protein (TgZFLP3), and ribosomal protein RPL7 (TgRPL7) were selected to further investigate their value in the diagnosis of acute toxoplasmosis. Immunofluorescence assays revealed that TgDPM and TgRPL7 were localized in the membrane surface, while TgZFLP3 was localized in the apical end. Western blotting revealed the presence of the three proteins in the serum during acute infection. Indirect ELISA results indicate that TgZFLP3 is likely to be a novel candidate for the diagnosis of acute toxoplasmosis. However, these three proteins may not be useful as candidate vaccines against toxoplasmosis owing to their low protective ability. In addition, deletion of the zflp3 gene partially attenuated virulence in Kunming mice. Collectively, we identified 28 CAgs in the serum of piglets with experimental acute toxoplasmosis and confirmed that TgZFLP3 is a potential biomarker for acute T. gondii infection. The results of this study provide data to improve the detection efficiency of acute toxoplasmosis.