Study of the migration of Fasciola hepatica juveniles across the intestinal barrier of the host by quantitative proteomics in an ex vivo model

Abstract

Fasciola hepatica is a trematode parasite that infects animals and humans causing fasciolosis, a worldwide-distributed disease responsible for important economic losses and health problems. This disease is of growing public health concern since parasite isolates resistant to the current treatment (triclabendazole) have increasingly been described. F. hepatica infects its vertebrate host after ingestion of the encysted parasite (metacercariae), which are found in the water or attached to plants. Upon ingestion, newly excysted juveniles of F. hepatica (FhNEJ) emerge in the intestinal lumen and cross the intestinal barrier, reach the peritoneum and migrate to the biliary ducts, where adult worms fully develop. Despite the efforts made to develop new therapeutic and preventive tools, to date, protection against F. hepatica obtained in different animal models is far from optimal. Early events of host-FhNEJ interactions are of paramount importance for the infection progress in fasciolosis, especially those occurring at the host-parasite interface. Nevertheless, studies of FhNEJ responses to the changing host environment encountered during migration across host tissues are still scarce. Here, we set-up an ex vivo model coupled with quantitative SWATH-MS proteomics to study early host-parasite interaction events in fasciolosis. After comparing tegument and somatic fractions from control parasites and FhNEJ that managed to cross a mouse intestinal section ex vivo, a set of parasite proteins whose expression was statistically different were found. These included upregulation of cathepsins L3 and L4, proteolytic inhibitor Fh serpin 2, and a number of molecules linked with nutrient uptake and metabolism, including histone H4, H2A and H2B, low density lipoprotein receptor, tetraspanin, fatty acid binding protein a and glutathione-S-transferase. Downregulated proteins in FhNEJ after gut passage were more numerous than the upregulated ones, and included the heath shock proteins HSP90 and alpha crystallin, amongst others. This study

Fasciola hepatica juveniles interact with the host fibrinolytic system as a potential early-stage invasion mechanism

“…More specifically, we identify FhCL3 and FhCB3 as potential PLG-binding proteins, and FhCL1, FhCL2 and FhCB2 to a lesser extent. This is consistent with the developmental stage-specific expression of these proteases, being FhCB1-3 and FhCL3 mostly expressed in the juvenile stages of the parasite that are found in the duodenum [ 36 , 48 , 49 ]. However, one of the limitations of our 2D-MS approach is that it is performed under denaturing conditions, which may expose internal PLG-binding epitopes in some proteins that are not employed for PLG-binding in a real physiological context.…”

“…Notwithstanding the origin of the tegument PLG-binding proteins, and based on the capacity of plasmin to degrade components of the ECM [35], these results support our original idea that PLG fixation on the tegument could represent a mechanism for FhNEJ to harness the functions of the host fibrinolytic system that provides an additional source of proteolytic activity to facilitate traversal of the intestinal wall and the successful establishment of the parasite within the vertebrate host. In the future, these findings could be further validated using in vivo or ex vivo models of F. hepatica infection [36,37].…”

“…In the future, these findings could be further validated using in vivo or ex vivo models of F . hepatica infection [ 36 , 37 ].…”

Fasciola hepaticajuveniles interact with the host fibrinolytic system as a potential early-stage invasion mechanism

“…More specifically, we identify FhCL3 and FhCB3 as potential PLG-binding proteins, and FhCL1, FhCL2 and FhCB3 to a lesser extent. This is consistent with the developmental stage-specific expression of these proteases, being FhCB1-3 and FhCL3 mostly expressed in the juvenile stages of the parasite that are found in the duodenum (46–48). However, one of the limitations of our 2D-MS approach is that it is performed under denaturing conditions, which may expose internal PLG-binding epitopes in some proteins that are not employed for PLG-binding in a real physiological context.…”

Fasciolosis: pathogenesis, host-parasite interactions, and implication in vaccine development

“…The progress of the -omics technologies and the immunoinformatic/immunoproteomic approaches should provide useful data in the next few years. An example is the new proteomic technologies applied to NEJs after crossing the gut ( 158 ) or during the early stages of hepatic migration, which may be useful to select new vaccine candidates directed against NEJs, a stage of the parasite that it is more exposed to the host immune system than adult ones located within the bile ducts.…”