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

ABSTRACT

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.

KEYWORDS:

• Toxoplasmosis
• molecular diagnosis
• Toxoplasma gondii
• maternal–fetal infections
• opportunistic infections
• PCR
• LAMP

Article highlights

• Molecular diagnosis is, along with serology, one of the cornerstones of toxoplasmosis diagnosis. It is highly accurate, and especially helpful in immunocompromised patients, as well as for the diagnosis of congenital or ocular toxoplasmosis.

• Prenatal diagnosis of congenital toxoplasmosis relies on the detection of parasitic DNA in the amniotic fluid. It is proposed in case of maternal seroconversion during pregnancy or ultrasound features compatible with fetal infection. A positive result signs congenital toxoplasmosis.

• PCR follow-up of high-risk immunocompromised patients is helpful for the early detection and management of T. gondii infection, especially in seropositive patients at-risk for reactivation or in case of serological mismatch (seropositive donor/seronegative recipient) in solid organ transplants.

• Standardized protocols for molecular diagnosis of toxoplasmosis are lacking. Diagnostic performances, including sensitivity and specificity, may vary according to the techniques used for DNA extraction and amplification. To date, among the different T. gondii PCR methods described, qPCR targeting the rep529 sequence should be preferred.

• To date, no syndromic commercial panel includes the detection of T. gondii.

Acknowledgments

The authors especially thank Dr Yvon Sterkers and Pr Patrick Bastien (Molecular Biology “Pole” of the French National Reference Center for Toxoplasmosis) for their constructive and helpful review of this manuscript.

Authors’ contributions

All authors have contributed to the conception and design of the review article and have been involved in writing the review article and/or revised it for intellectual content.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.