Complete cryspovirus genome sequences from Cryptosporidium parvum isolate Iowa.

Bisegmented dsRNA viruses that infect most or all isolates of apicomplexan parasite Cryptosporidium parvum are currently assigned to a single species, Cryptosporidium parvum virus 1, in genus Cryspovirus, family Partitiviridae. An analysis of existing sequence data suggested that the complete sequences of both cryspovirus genome segments, dsRNA1 and dsRNA2, had yet to be determined. We therefore set out to accomplish this for the virus strain that infects C. parvum isolate Iowa. The results suggest that several previous cryspovirus sequences are indeed truncated at one or both segment termini and also identify sequences at or near the termini that are conserved in both segments. Complete sequences of other cryspovirus strains, including ones from other Cryptosporidium species, are needed for refining their classification into one or more virus species.

The Cryptosporidium parvum C-Type Lectin CpClec Mediates Infection of Intestinal Epithelial Cells via Interactions with Sulfated Proteoglycans.

The apicomplexan parasite Cryptosporidium causes significant diarrheal disease worldwide. Effective anticryptosporidial agents are lacking, in part because the molecular mechanisms underlying Cryptosporidium-host cell interactions are poorly understood. Previously, we identified and characterized a novel Cryptosporidium parvum C-type lectin domain-containing mucin-like glycoprotein, CpClec. In this study, we evaluated the mechanisms underlying interactions of CpClec with intestinal epithelial cells by using an Fc-tagged recombinant protein. CpClec-Fc displayed Ca(2+)-dependent, saturable binding to HCT-8 and Caco-2 cells and competitively inhibited C. parvum attachment to and infection of HCT-8 cells. Binding of CpClec-Fc was specifically inhibited by sulfated glycosaminoglycans, particularly heparin and heparan sulfate. Binding was reduced after the removal of heparan sulfate and following the inhibition of glycosaminoglycan synthesis or sulfation in HCT-8 cells. Like CpClec-Fc binding, C. parvum attachment to and infection of HCT-8 cells were inhibited by glycosaminoglycans and were reduced after heparan sulfate removal or inhibition of glycosaminoglycan synthesis or sulfation. Lastly, CpClec-Fc binding and C. parvum sporozoite attachment were significantly decreased in CHO cell mutants defective in glycosaminoglycan synthesis. Together, these results indicate that CpClec is a novel C-type lectin that mediates C. parvum attachment and infection via Ca(2+)-dependent binding to sulfated proteoglycans on intestinal epithelial cells.

Systemic and Mucosal Immune Responses to Cryptosporidium-Vaccine Development.

Cryptosporidium spp is a major cause of diarrheal disease worldwide, particularly in malnourished children and untreated AIDS patients in developing countries in whom it can cause severe, chronic and debilitating disease. Unfortunately, there is no consistently effective drug for these vulnerable populations and no vaccine, partly due to a limited understanding of both the parasite and the host immune response. In this review, we will discuss our current understanding of the systemic and mucosal immune responses to Cryptosporidium infection, discuss the feasibility of developing a Cryptosporidium vaccine and evaluate recent advances in Cryptosporidium vaccine development strategies.