Genetic Diversity of Toxoplasma Gondii in Cancer Patients

The global cancer burden is estimated to have risen to 18.1 million new cases and 9.6 million deaths in 2018. Patients with cancer have deficient cellular immunity and are potentially susceptible to opportunistic infections including Toxoplasma gondii (T. gondii). Few reports are available about toxoplasmosis in this group of patients. In recent years, it has emerged as an important life-threatening opportunistic pathogen in immunocompromised patients.

T. gondii is a ubiquitous obligate intracellular protozoan parasite that can infect virtually any nucleated vertebrate cell. T. gondii is one of the most successful parasites worldwide, with upwards of 30% of the human population infected.

While T. gondii infection in immunocompetent individuals is usually asymptomatic, it is more detrimental in immunocompromised individuals, such as those with HIV, patients receiving organ transplants or undergoing cancer treatment. A variety of malignancies, including lymphoma, leukemia, and myeloma, can reactivate toxoplasmosis. Moreover, T. gondii is incriminated to be responsible for the progression of malignant diseases.

Screening of toxoplasmosis in cancer patients is mandatory to guard against life-threatening disseminated disease. Diagnosis rely mainly on serology. A study in 2018 was performed to assess the prevalence of anti-T. gondii antibody among cancer patients in Cairo-Egypt. Among 180 cancer patients, a total of 110 patients (61.1%) were positive for anti-T. gondii antibodies. Till now there is no screening program in Egypt for toxoplasmosis in cancer patients although recently demonstrated to be at high risk for acquiring the infection with life-threatening sequelae.

Despite the significant improvements in serological methods, there are still unresolvable limitations such as inability of these methods to confirm the presence of parasite in immunocompromised patients. To overcome these limitations, different molecular methods including conventional PCR (cn PCR), nested PCR, real-time PCR (qPCR) and also loop-mediated isothermal amplification (LAMP) techniques have been developed to detect T. gondii DNA in biological samples.