Abstract
Cryptosporidium ryanae is one of the most common species for cryptosporidiosis in cattle. However, little is known of the genetic characteristics of C. ryanae due to the lack of subtyping tools. In the present study, the 60-kDa glycoprotein (gp60) gene of C. ryanae was identified in whole genome sequence data and analyzed for sequence characteristics using bioinformatics tools. The protein it encodes had some of the typical characteristics of GP60 proteins, with a signal peptide, a furin cleavage site, and a glycosylphosphatidylinositol anchor at the C terminus of the protein, and numerous O-glycosylation sites. The gene sequence was used in the development of a subtyping tool, which was used in characterizing C. ryanae from 110 specimens from dairy cattle, 2 from beef cattle, 6 from yaks, and 4 from water buffaloes in China. Altogether, 17 subtypes from 8 subtype families were recognized, namely XXIa to XXIh. Possible host adaption was identified within this species, reflected by the unique occurrence of XXIa, XXIc, and XXIh in dairy cattle, yaks, and water buffaloes, respectively. Some geographical differences were detected in the distribution of subtype families in dairy cattle; specimens from southern China showed higher genetic diversity than from northern China, and the XXIa subtype family was only seen in dairy cattle in southern and eastern China. The gp60-based subtyping tool should be useful in molecular epidemiological studies of the transmission of C. ryanae.
Highlights
Cryptosporidium spp. are important pathogens for moderate-to-severe diarrhea in humans and various animals, with a worldwide distribution [1]
There are over 40 established species, four of which are commonly seen in cattle, including Cryptosporidium parvum, C. bovis, C. ryanae and C. andersoni [2,3]
Despite the much larger size, the structure of the GP60 protein of C. ryanae had some of the classic features of GP60 proteins, including the presence of a signal peptide with a cleavage site between Ser 19 and Ala 20, a furin cleavage site (RSRR) between the GP40 and GP15 fragments of the protein, and a glycosylphosphatidylinositol (GPI) anchor at the C terminus of the protein, one potential N-glycosylation site, and 115 O-glycosylation sites
Summary
Cryptosporidium spp. are important pathogens for moderate-to-severe diarrhea in humans and various animals, with a worldwide distribution [1]. C. parvum is almost exclusively seen in pre-weaned calves, C. bovis and C. ryanae mostly in post-weaned calves, and C. andersoni in juvenile and adult cattle [4]. These four species differ significantly in infection patterns, pathogenicity, and human infectivity. Sequence analysis of the 60-kDa glycoprotein (gp60) gene has been widely used in subtyping C. parvum and other intestinal Cryptosporidium species or genotypes. The application of gp subtyping tools has contributed greatly to our understanding of the genetic diversity, transmission dynamics, as well as host adaption in human-pathogenic Cryptosporidium spp. Subtyping tools are not available for C. ryanae and C. bovis, the two bovine-specific intestinal Cryptosporidium spp. with reduced pathogenicity
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