Towards a rapid sequencing-based molecular surveillance and mosaicism investigation of Toxoplasma gondii

• Published in: Parasitology research (1987) 2020-02, Vol.119 (2), p.587-599
• Main Authors: Vilares, Anabela, Borges, Vítor, Sampaio, Daniel, Ferreira, Idalina, Martins, Susana, Vieira, Luis, Gargaté, Maria João, Gomes, João Paulo
• Format: Article
• Language: English
• Subjects: Alleles; Animals; Bioinformatics; Biomedical and Life Sciences; Biomedicine; DNA sequencing; DNA, Protozoan - genetics; Epidemiology; Genetic Variation; Genomes; Genomics; Genotype; Genotypes; Genotyping; Health aspects; Humans; Immunology; Medical Microbiology; Mice; Microbiology; Microsatellite Repeats; Mosaicism; Next-generation sequencing; Nucleotide sequencing; Polymorphism, Restriction Fragment Length; Protozoa; Protozoology - Original Paper; Recombination; Sequence Analysis, DNA; Strains (organisms); Surveillance; Toxoplasma - genetics; Toxoplasma - pathogenicity; Toxoplasma gondii; Toxoplasmosis, Animal - parasitology; Virulence; Virulence - genetics; Whole genome sequencing
• ISSN: 0932-0113; 1432-1955
• DOI: 10.1007/s00436-019-06523-3

Advances in molecular epidemiology of Toxoplasma gondii are hampered by technical and cost-associated hurdles underlying the acquisition of genomic data from parasites. In order to implement an enhanced genotyping approach for molecular surveillance of T. gondii , we applied a multi-locus amplicon-based sequencing strategy to samples associated with human infection. This approach, targeting genome-dispersed polymorphic loci potentially involved in adaptation and virulence, genetically discriminated almost all 68 studied strains and revealed a scenario of marked genomic mosaicism. Two-thirds ( n = 43) of all strains were classified as recombinant, although recombination seemed to be linked to the classical archetypal lineage. While 92% of the Sag 2 archetype I strains revealed genetic mosaicism, only 45% of Sag 2 archetype II strains were identified as recombinant. Contrarily to the virulence-associated archetype I, most type II strains (regardless of their recombination background) were non-virulent in mouse. Besides Sag 2, some of the newly studied loci (namely the type I/I-like alleles of Sag 1, B17, PK1, and Sag 3 and type III/III-like alleles of TgM-A) constitute promising candidates to rapidly infer T. gondii mouse virulence. Our successful attempt to capture microsatellite length variation launches good perspectives for the straightforward transition from the laborious intensive historical method to more informative next-generation sequencing (NGS)/bioinformatics-based methodologies. Overall, while T. gondii whole-genome sequencing will be hardly feasible in most laboratories, this study shows that a discrete loci panel has the potential to improve the molecular epidemiology of T. gondii towards a better monitoring of circulating genotypes with clinical importance.