Success and Virulence in Toxoplasma as the Result of Sexual Recombination Between Two Distinct Ancestries

• DOI: 10.1126/science.1061888
• Publication Date: 2002-07-27T09:40:17Z
• Authors: Michael E. Grigg; Serge Bonnefoy; Adrian B. Hehl; Yasuhiro Suzuki; John C. Boothroyd
• Keywords: Recombination, Genetic; 0303 health sciences; Polymorphism, Genetic; Base Sequence; Genotype; Virulence; Genes, Protozoan; Molecular Sequence Data; Genetic Variation; Polymorphism, Single Nucleotide; Introns; 3. Good health; Lethal Dose 50; Mice; 03 medical and health sciences; Toxoplasmosis, Animal; Mice, Inbred CBA; Animals; Humans; Toxoplasma; Alleles; Crosses, Genetic; Toxoplasmosis

Toxoplasma gondii is a common human pathogen causing serious, even fatal, disease in the developing fetus and immunocompromised patients. Despite its ability to reproduce sexually broad geographic host range, has clonal population structure comprised principally of three lines. We have analyzed 15 polymorphic loci archetypal type I, II, III strains found that polymorphism was limited to, at most, two rather than allelic classes no detected between alleles given type. Multilocus analysis 10 nonarchetypal isolates likewise clustered vast majority into same distinct ancestries. These data strongly suggest currently predominant genotypes exist as pandemic outbreak from genetic mixing discrete ancestral To determine if such could lead extreme virulence observed for some strains, we examined F 1 progeny cross II strain, both which are relatively avirulent mice. Among were recombinants least 3 logs more virulent either parent. Thus, sexual recombination, by combining polymorphisms competing lines, can be powerful force driving natural evolution this highly successful pathogen.