Objectives: Toxoplasma gondii infection in transplant recipients can lead to toxoplasmosis, which in some cases may have a rapid disease course or to be fatal. Serological tests do not often contribute to the diagnosis. Although PCR may early identify the infection, this technique is not well standardised and there is no consensus on the optimal protocol to be used in laboratories. We homogenised our PCR data with those of a Real-time PCR targeting different T. gondii genes. Methods: T. gondii genes were explored before and after liver transplantation (LT) with PCR and Real-time PCR (LightCycler, Roche) targeting bradyzoite (BAG-1) matrix (MAG-1), cyst surface (SAG-4) and dense granule (GRA-6) specific genes other than B1 gene. These have been developed by us and retrospectively evaluated in PBMC specimens from 7 LT patients in whom serological status (anti T. gondii IgG) before transplantation was known in 4 patients only. Results: We found 4 PCR positive specimens of which 2 with B1 gene (after LT) and 2 with GRA-6 and BAG-1 (before LT). With LightCycler (expressed as T. gondii genome equivalents/ml) the overall positivity rates were 12 before and 17 after LT. In particular, in marked contrast with PCR results, the number of positive specimens before LT were 4 (B1), 2 (SAG-1), 3 (SAG-4 and MAG-1, respectively). After LT we did detect 7 (B1), 3 (SAG-1), 5 (SAG-4) 3 (MAG-1). Two patients were found to have elevated DNA copy number of SAG-4 in post-LT specimens only. Conclusions: Transmission of toxoplasna infection via LT is extremely uncommon with only few confirmed cases previously reported. LightCycler based method can identify a relatively high incidence of potential new infections compared with PCR excluding most of the false-negative PCR results associated with contamination with previously amplified products. This is of greater use for monitoring LT recipients with negative serological tests at risk of developing toxoplasmosis and managing therapy. LT patients did not receive TMP/SMX as post-transplant infection prophylaxis. Improvement and standardisation of diagnostic tests, especially real-time PCR targeting markers expressed on bradyzoites or matrix is also important in order to prevent relapses and symptomatic disease.

Asymptomatic Toxoplasma gondii infection in liver transplant patients

CONTINI, Carlo;SERACENI, Silva;CULTRERA, Rosario;SCIVALES, Sonya;
2009

Abstract

Objectives: Toxoplasma gondii infection in transplant recipients can lead to toxoplasmosis, which in some cases may have a rapid disease course or to be fatal. Serological tests do not often contribute to the diagnosis. Although PCR may early identify the infection, this technique is not well standardised and there is no consensus on the optimal protocol to be used in laboratories. We homogenised our PCR data with those of a Real-time PCR targeting different T. gondii genes. Methods: T. gondii genes were explored before and after liver transplantation (LT) with PCR and Real-time PCR (LightCycler, Roche) targeting bradyzoite (BAG-1) matrix (MAG-1), cyst surface (SAG-4) and dense granule (GRA-6) specific genes other than B1 gene. These have been developed by us and retrospectively evaluated in PBMC specimens from 7 LT patients in whom serological status (anti T. gondii IgG) before transplantation was known in 4 patients only. Results: We found 4 PCR positive specimens of which 2 with B1 gene (after LT) and 2 with GRA-6 and BAG-1 (before LT). With LightCycler (expressed as T. gondii genome equivalents/ml) the overall positivity rates were 12 before and 17 after LT. In particular, in marked contrast with PCR results, the number of positive specimens before LT were 4 (B1), 2 (SAG-1), 3 (SAG-4 and MAG-1, respectively). After LT we did detect 7 (B1), 3 (SAG-1), 5 (SAG-4) 3 (MAG-1). Two patients were found to have elevated DNA copy number of SAG-4 in post-LT specimens only. Conclusions: Transmission of toxoplasna infection via LT is extremely uncommon with only few confirmed cases previously reported. LightCycler based method can identify a relatively high incidence of potential new infections compared with PCR excluding most of the false-negative PCR results associated with contamination with previously amplified products. This is of greater use for monitoring LT recipients with negative serological tests at risk of developing toxoplasmosis and managing therapy. LT patients did not receive TMP/SMX as post-transplant infection prophylaxis. Improvement and standardisation of diagnostic tests, especially real-time PCR targeting markers expressed on bradyzoites or matrix is also important in order to prevent relapses and symptomatic disease.
2009
Toxoplasma gondii; Liver transplantation; Light-Cycler PCR; Bradyzoite gene
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1379522
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