To investigate the roles of lncRNA deleted in lymphocytic leukaemia 1 (DLEU1) on migration and invasion of human trophoblast cells. Human chorionic trophoblast cell line HTR8/SVneo was cultured and transfected using lncRNA DLEU1 small interfering RNA. Real-time quantitative polymerase chain reaction was used to detect lncRNA DLEU1 expression. The activity of migration regulatory protein CDC42 was detected by western blot. The downstream miRNA targets of lncRNA and mRNAs targeted by corresponding miRNAs were respectively predicted using bioinformatics analyses. Compared with the control group, the expression of lncRNA DLEU1 in the small interfering RNA group was significantly decreased (P < 0.05). There was no significant change in cell proliferation capacity for transfected cells (lncRNA DLEU1 siRNA-1, P = 0.537; lncRNA DLEU1 siRNA-2, P = 0.384), but cell migration (lncRNA DLEU1 siRNA-1, P = 0.025; lncRNA DLEU1 siRNA-2, P = 0.019) and invasion (lncRNA DLEU1 siRNA-1, P = 0.0327; lncRNA DLEU1 siRNA-2, P = 0.021) was significantly reduced. CDC42 activity in the lncRNA DLEU1 knockdown group decreased and the phosphorylation of cofilin increased. Therefore, downregulation of lncRNA DLEU1 suppressed the migration and invasion of human trophoblast cells.

Plasmodium rhoptry neck protein 2 (RON2), which is released from the neck portion of the merozoite rhoptries and interacts with the microneme protein Apical Membrane Antigen 1 (AMA1), plays a crucial role in erythrocyte invasion. In this study, we sequenced the Plasmodium vivax RON2 gene from 19 P. vivax isolates collected in central China in order to establish whether this protein is under positive diversifying selection, which may occur as a result of protective host immune pressure†. In comparison with the P. vivax Sal-1 reference line, we found 10 amino acid substitutions dispersed throughout the open reading frame as well as indels caused by polymorphism in a repeat unit (21–23 repeats of (Q/E/K/N/H)(G/D)G(H/L/Y/P)G) in the second tandem repeat region located at amino acid positions 541–650. A McDonald-Kreitman test with RON2 sequences from the primate malaria parasite Plasmodium knowlesi, detected significant departure from neutrality in the PvRON2 3′ region (nucleotide positions 2668–6609). These results suggest that the PvRON2 gene has evolved under positive diversifying selection.

Twenty-one monoclonal antibodies, obtained after immunization of mice with erythrocytic stages of Plasmodium falciparum, produced a double dot image in IFA. Immunoelectronmicroscopy indicated that the mAbs reacted with the rhoptries. Rhoptries are pear-shaped apical organelles, believed to be involved in invasion of the host cell by the parasite. The mAbs all immunoprecipitated the high molecular weight antigen complex. Some mAbs recognized on immunoblots only 1 protein of this complex, whereas others reacted with RhopH1 and RhopH3, or RhopH2 and RhopH3 or with the 3 proteins. An additional antigen of 52 kDa was also recognized by some of the mAbs. The epitopes defined by the mAbs were present in most of the 40 P. falciparum strains or isolates studied by IFA. Interestingly, the mAbs also reacted with high titres on P. vivax and P. ovale, but produced images that did not indicate an apical location. The mAbs failed to react on the non-human malaria parasites studied, P. cynomolgi and P. inui. On P. berghei or P. chabaudi parasites, only 5 mAbs gave a positive reaction, labelling a large network outside the parasite. Finally, the mAbs did not react with P. falciparum sporozoites, indicating that the rhoptries of merozoites and sporozoites, the two invasive stages of the malaria life-cycle are equipped with distinct sets of proteins.

Microsporidia are obligate intracellular parasites that utilize a unique mechanism to infect host cells, which is one of the most sophisticated infection mechanisms in biology. Microsporidian spores contain a long coiled polar tube that extrudes from the spores and penetrates the membranes of new host cells. We have initiated a study to investigate the invasive process and intracellular fate of the microsporidium Encephalitozoon cuniculi. Here we show that relatively few cells were infected through the traditional penetration of the polar tube from outside. Rather, phagocytosis of spores occurred at least 10 times more frequently than injection of sporoplasms. Some spores extruded their polar tube inside the cells following phagocytosis. Membranes of the vacuoles surrounding the internalized spores were positive for late endosomal and lysosomal markers. Spores that remained inside these compartments disappeared within 3 days. Thus, our studies demonstrate that in addition to the unique way in which microsporidia infect host cells, E. cuniculi spores can also gain access to host cells by phagocytosis. The presence of intracellular spores that have extruded their polar tube shows that some spores germinate after phagocytosis, thus escaping from the phagosomes that mature into lysosomes.