Genetic recombination and Cryptosporidium hominis virulent subtype IbA10G2 - PubMed (original) (raw)

Genetic recombination and Cryptosporidium hominis virulent subtype IbA10G2

Na Li et al. Emerg Infect Dis. 2013 Oct.

Abstract

Little is known about the emergence and spread of virulent subtypes of Cryptosporidium hominis, the predominant species responsible for human cryptosporidiosis. We conducted sequence analyses of 32 genetic loci of 53 C. hominis specimens isolated from a longitudinally followed cohort of children living in a small community. We identified by linkage disequilibrium and recombination analyses only limited genetic recombination, which occurred exclusively within the 60-kDa glycoprotein gene subtype IbA10G2, a predominant subtype for outbreaks in industrialized nations and a virulent subtype in the study community. Intensive transmission of virulent subtype IbA10G2 in the study area might have resulted in genetic recombination with other subtypes. Moreover, we identified selection for IbA10G2 at a 129-kb region around the 60-kDa glycoprotein gene in chromosome 6. These findings improve our understanding of the origin and evolution of C. hominis subtypes and the spread of virulent subtypes.

Keywords: Cryptosporidium hominis; cryptosporidiosis; genetic recombination; molecular epidemiology; parasites; population genetics; subtype; subtype IbA10G2; virulence.

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Figures

Figure 1

Figure 1

Relationship among various 60-kDa glycoprotein gene subtypes of Cryptosporidium hominis by substructure analysis. Predicted population numbers K = 2–5 were applied in STRUCTURE version 2.2 (

http://pritch.bsd.uchicago.edu/structure.html

) analysis of the data. Colored regions indicate major ancestral contributions. Mixed genotypes are indicated by the pattern of color combinations. Values along the baseline indicate _C. hominis_–positive fecal specimens.

Figure 2

Figure 2

Median-joining network for various subtypes of Cryptosporidium hominis. Circles are proportional to the frequency of each multilocus genotype (MLG) (21 MLGs on the basis of segregating sites of concatenated sequences excluding the 60-kDa glycoprotein gene). The color of each circle represents the 60-kDa glycoprotein gene subtypes of the C. hominis specimens: IaA13R8 (green), IbA10G2 (blue), IdA10 (purple), IdA20 (yellow), and IeA11G3T3 (red). Length of lines connecting MLGs is proportional to the number of single-nucleotide polymorphisms.

Figure 3

Figure 3

Pairwise intergenic linkage disequilibrium (LD) matrix among 25 polymorphic loci of Cryptosporidium hominis. The 25 polymorphic loci are indicated in gray (see Table 2 for identification of loci). Significant LD between loci is indicated in red. Subtype IbA10G2 (A), which has 87 instances of pairwise LD, has fewer LD in comparison with the remaining subtypes (B), which have 227 instances of pairwise LD. In IbA10G2, loci around the 60-kDa glycoprotein gene (locus 12) have no LD with any other loci in chromosome 6.

Figure 4

Figure 4

Genetic variation in haplotype diversity at 25 polymorphic loci in chromosome 6 of Cryptosporidium hominis (see Table 2 for identification of loci). Red squares indicate subtype IbA10G2 and black circles indicate non-IbA10G2 subtypes. A homogeneity (reduced haplotype diversity) of subtype IbA10G2 was seen in 4 loci around the 60-kDa glycoprotein gene.

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