Analysis of differentially expressed genes of Trichinella spiralis larvae activated by bile and cultured with intestinal epithelial cells using real-time PCR

The activation of Trichinella spiralis muscle larvae (ML) by exposure to intestinal contents or bile and the intestinal epithelial cells (IECs) themselves are two pivotal requirements for the in vitro larval invasion of IECs. However, it is yet unknown which genes are involved in the process of larval invasion. The purpose of the present study was to analyze the differentially expressed genes of T. spiralis larvae activated by bile and cultured with IECs by using real-time polymerase chain reaction. Ten T. spiralis genes encoded the proteins produced by the larvae after co-culture with IECs were selected. Compared with untreated ML, four genes were up-regulated in both bile-activated and cell-cultured larvae, including calcium-dependent secretion activator (Csa; 2.55- and 16.04-fold, respectively), multi cystatin-like domain protein precursor (Mcd; 4.36 and 52), serine protease (Sp; 2.03 and 20.02), and intermediate filament protein ifa-1 (Ifa 1; 2 and 3.31). The expression of two genes, enolase (Eno; 1.51) and ribosomal protein S6 kinase beta-1 (Rsk; 1.49), was up-regulated only in cell-cultured larvae, not in bile-activated larvae. The expression of secreted 5'-nucleotidase (5 N; 1.42) and putative serine protease (Psp; 1.41) was up-regulated in bile-activated larvae, but was not changed or down-regulated after cultured with IECs. ATP synthase F1, beta subunit (ATPase; 0.58 and 0.51) and serine protease precursor (Spp; 0.42 and 0.65) were down-regulated in both bile-activated and cell-cultured larvae. This study provide some differentially expressed genes among the untreated (normal), bile-activated and cell-cultured larvae of T. spiralis. The up-regulated genes might be related with the larval invasion of IECs, but their exact biological functions need to be further investigated. This study will be helpful to further elucidate the molecular mechanism of the invasion of IECs by T. spiralis larvae and to better understand the interaction between parasite and host enterocytes.