Genetic diversity of African isolates of Toxoplasma gondii

Toxoplasma gondii is an intracellular protozoan parasite and has the ability to infect allwarm-blooded animals, including humans. While the three clonal lineages of T. gondii (I, IIand III) predominate in North America and Europe, strains from other regions in the worldappear to have more diverse genotypes. The aim of the current research is to analyse thelevel of genetic variation among local African T. gondii isolates in relation to theirphenotype (genotype phenotype relationships). In this study, multi-locus nested PCRsequence analysis of seven Ugandan T. gondii isolates was applied using nine differentgenetic markers distributed across seven chromosomes and the apicoplast genome of T.gondii, which improved the discrimination power to detect variation among the localUgandan strains. Although these markers were sufficient to separate global variationbetween T.gondii strains, they were not adequate to totally resolve within closely relatedlocal isolates. To understand the impact of local variation on strain diversity, whole genomesequence was generated for two Ugandan strains type II using Illumina MiSeq paired-endsequencing, revealing variations between these strains and the type II reference strain of T.gondii (TgME49). In this study, we have perhaps the first example of the deeper sequencingof isolates from the same geographical region at the same time point, which showed thatthey are non-identical. Novel polymorphisms were identified in a virulence associated genein both Ugandan strains resulting in modification of the protein structure of this gene whichcould be associated with phenotype variation in the in vitro growth rate of these strains.Comparing the in vitro growth rates of the sympatric Ugandan strains, a cluster of 3 strainshad higher growth. These were genotypically identical by using PCR sequencing technique,while the non-identical sympatric strains had lower growth rates, providing evidence thatgenotype may influence phenotype. An important finding was evidence of recombinationbetween type II and III within three Ugandan strains, revealed through multi-locus PCRsequencing, and in an additional Ugandan strain through deeper whole genome sequencing.Six polymorphic markers were identified via analysis of three biologically relevant genesfamilies (SRS, ROPs and GRA), enhancing the resolution power to identify variationsamong local type II strains of T. gondii. It is recommended that further study of thesepolymorphic markers is carried out and that they are added into the MLST analysis of T.gondii, especially between closely related local isolates.

Level dc:type.qualificationlevel

Doctoral (Level 8)

Year dc:date.issued

2026

Author dc:creator

• Alruhaili, MHB

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1407061

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1407061