Abstract
BackgroundStrategies employed by parasites to establish infections are poorly understood. The host-parasite interface is maintained through a molecular dialog that, among other roles, protects parasites from host immune responses. Parasite excretory/secretory products (ESP) play major roles in this process. Understanding the biology of protein secretion by parasites and their associated functional processes will enhance our understanding of the roles of ESP in host-parasite interactions.Methodology/Principal FindingsESP was collected after culturing 10 adult female Ascaris suum. Perienteric fluid (PE) and uterine fluid (UF) were collected directly from adult females by dissection. Using SDS-PAGE coupled with LC-MS/MS, we identified 175, 308 and 274 proteins in ESP, PE and UF, respectively. Although many proteins were shared among the samples, the protein composition of ESP was distinct from PE and UF, whereas PE and UF were highly similar. The distribution of gene ontology (GO) terms for proteins in ESP, PE and UF supports this claim. Comparison of ESP composition in A. suum, Brugia malayi and Heligmosoides polygyrus showed that proteins found in UF were also secreted by males and by larval stages of other species, suggesting that multiple routes of secretion may be used for homologous proteins. ESP composition of nematodes is both phylogeny- and niche-dependent.Conclusions/SignificanceAnalysis of the protein composition of A. suum ESP and UF leads to the conclusion that the excretory-secretory apparatus and uterus are separate routes for protein release. Proteins detected in ESP have distinct patterns of biological functions compared to those in UF. PE is likely to serve as the source of the majority of proteins in UF. This analysis expands our knowledge of the biology of protein secretion from nematodes and will inform new studies on the function of secreted proteins in the orchestration of host-parasite interactions.
Highlights
Ascaris lumbricoides is an extremely prevalent gastrointestinal nematode parasite of humans
We identified 530 distinct proteins in these samples, 175 in excretory/secretory products (ESP), 308 in perienteric fluid (PE) and 274 in uterine fluid (UF)
In the ESP sample, 67 proteins were specific to ESP only, 26 were shared only between ESP and PE, and 40 were common only to ESP and UF (Table S4)
Summary
Ascaris lumbricoides is an extremely prevalent gastrointestinal nematode parasite of humans. Pathology may result when parasites migrate to the bile ducts, causing cholangitis. Ascaris lumbricoides has been reported to cause lactose intolerance and to reduce absorption of vitamin A. Severe pathology can occur when larvae migrate through the lungs, causing inflammatory reactions. This may lead to pneumonitis, depending on the number of larvae penetrating the alveolar walls, and to pulmonary eosinophilia, with symptoms of fever and difficulty in breathing. Parasite excretory/secretory products (ESP) play major roles in this process. Understanding the biology of protein secretion by parasites and their associated functional processes will enhance our understanding of the roles of ESP in host-parasite interactions
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