Molecular and virulence characterization of Toxoplasma gondii strains isolated from humans in Portugal

Abstract

Toxoplasma gondii is an apicomplexan parasite responsible for toxoplasmosis which infects all warm-blooded vertebrates, including mammals and birds. The majority of studies conducted in Europe have revealed that more than 80 % of strains isolated from human infections belong to genotype II, whereas genotypes I and III are responsible for a small number of cases. Atypical and recombinant strains are generally associated with more severe infections. In Portugal, there is a lack of data concerning genetic diversity as the classical typing studies in humans have never been performed. We aimed to determine the Sag2 and microsatellite-based (TUB2, TgM-A, W35, B17, B18) genotypes of T. gondii isolated from humans in Portugal, as well as to study their virulence in mice. We analyzed 48 strains from congenital and acquired toxoplasmosis collected during the last two decades. Sag2-based genotyping of T. gondii was achieved in all 48 strains where 35 (73 %) were classified as type II and 13 (27 %) were type I. The multilocus PCR of five microsatellites allowed the classification of 10 strains (21 %) as recombinant strains that had been previously identified as type II or I by Sag2 typing. Seven out of the 48 strains, including three type I, three recombinant, and one type I, were virulent in mice. This study constitutes the first evidence of recombinant strains circulating in Portugal in humans from congenital infection, highlighting the need for a better evaluation of these strains as their phenotype is still barely understood.

First isolation and molecular characterization of Toxoplasma gondii strains from human congenital toxoplasmosis cases in Monastir, Tunisia

“…Elsewhere, in European countries it has been shown that more than 80% of strains isolated from human infections belong to genotype II 12,13,28,29 . Genetic characterization of samples from German patients with cerebral, ocular, and systemic toxoplasmosis was achieved in 88% of T. gondii type II.…”

Toxoplasma gondii Genotyping: A Closer Look Into Europe

“…Unlike the previously mentioned methods, the MS-based methodology has been widely used in the genetic characterization of human samples, involving a total of 428 samples in 20 different studies. Despite the participation of a greater number of European countries, France clustered 77.3% of the human samples analyzed ( Ajzenberg et al., 2009 ; Ajzenberg et al., 2015 ), followed by Portugal (11.7%) ( Ajzenberg et al., 2009 ; Vilares et al., 2017 ), Denmark (4.7%) ( Jokelainen et al., 2018 ), and Belgium (4.4%) ( Gisbert Algaba et al., 2020 ); most of the other countries contributed with up to three single isolates (Austria, Germany, Romania, Serbia, The Netherlands, and UK). Concerning strain types detected in human population, 86.4% corresponded with type II strains, the types I and III were found in low proportions (2.6 and 3% respectively), and those of MRA infections corresponded to 6.3% of cases.…”

Recém-nascidos com risco de toxoplasmose congênita, revisão de 16 anos

“…Isto está de acordo com os presentes resultados, visto que não se encontraram diferenças quanto a este achado e o momento da infeção congênita, ressalvando que a retinocoroidite foi pouco frequente na nossa amostra, principalmente se comparada a estudos sul-americanos. Tendo em vista que os exames oftalmológicos foram realizados em todos os casos no período neonatal e os lactentes foram reavaliados até os 12 meses independentemente do resultado anterior, é possível que a baixa ocorrência de retinocoroidite seja resultante da menor agressividade da estirpe de T. gondii prevalente em Portugal, como descrito por Vilares et al [48], e as lesões oculares sejam comparáveis às de outras crianças europeias, menos frequentes e mais leves do que no Brasil [45,57].…”