Genotyping of Toxoplasma gondii: the advantages of variable number tandem repeats within coding regions

MORETTA, ROSALÍA; SANCHEZ, VANESA; FENOY, IGNACIO M.; GOLDMAN, A; RUYBAL, PAULA; MARTIN, VALENTINA

Infection, Genetics and Evolution

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 p. 226 - 230

1567-1348

Toxoplasma gondii is an intracellularprotozoan which is widely distributed. Infection occurs as a result ofingestion of uncooked meat and exposure to cat faeces. [if1] Immunocompetent individuals aregenerally asymptomatic, while the severe disease may occur in immunocompromisedsubjects and in congenital toxoplasmosis, which is caused by the transplacentalacquisition of T. gondii. Genetic diversity of T. gondii has often beenstudied using a PCR-RFLP scheme based on nine molecular markers. These studiesled to the description of a clonal population structure with three mainlineages (I, II and III) in North America and Europe and higher geneticdiversity in South America.The aim of thisstudy was to develop molecular markers that allowed discrimination of geneticvariants within each clonal lineage.We analyzed the genome of T. gondii toidentify genes containing variable number tandem repeats (VNTRs). The codingsequences of T. gondii ME49 genome wereprocessed with Tandem Repeat Finder software. A panel of candidate markerswas selected based on the following parameters: the repeat unit size (>9 bp) and composition (to avoidsingle and dinucleotide runs), the number of copies (<20), and the absenceof introns within the repeat region.The selected panel of eightmolecular markers was analyzed in PRU and RH strains. As a first step, thevariability of the sequence size allowed us to differentiate PRU from ME49 (two typeII strains) and RH from GT1 (two type I strains). Additionally,amplification products from PRU and RH strains were sequenced to studyintra-lineage variability. Aside from size polymorphisms in the amplification products we were ableto identify sequence variability in polymorphic markers.