Imaging Plasmodium falciparum-infected ghost and parasite by atomic force microscopy.

Atomic force microscopy was used to image the membrane cytoskeleton network of normal and P. falciparum-infected ghosts. The membrane cytoskeleton network was examined in air-dried ghost preparations from normal and infected cells. We found that the spectrin network was changed in infected ghosts. The thickness of the normal red cell membrane was about 15.05 +/- 2.27 nm, while the thickness of the P. falciparum-infected membrane was found to be 22.97 +/- 3.84 nm. The ghost containing ring stage parasites exhibited areas of particle-like protrusions ranging in size from 0.2 to 0.7 micron. The surface of the P. falciparum parasite was also imaged in air-dried samples, showing the existence of a large protrusion extending from the parasite surface.

Hepatitis C virus infection in children with hemophilia: characterization of antibody response to four different antigens and relationship of antibody response, viremia, and hepatic dysfunction.

We studied hepatitis C virus (HCV) infection in children with hemophilia by characterizing the antibody responses to four different HCV antigens and investigating the relationship of the antibody response to viremia and hepatic dysfunction. Three antigens (core, nonstructural (NS) 3, and NS5) were expressed in Escherichia coli transfected with plasmids that contained fragments of the putative core and of the NS3 and NS5 regions of the HCV genome, respectively. Antibody responses to these three antigens and the commercially available C100 antigen were detected by enzyme-linked immunosorbent assay. In 45 children with hemophilia, the percentage of children with seropositivity for C100, core, NS3, and NS5 protein in one or more specimens was 82%, 91%, 91%, and 89%, respectively. The time course of changes in the antibody response to the four antigens was determined by using sera obtained from 44 of the 45 patients at intervals of 1 to 4 years. Antibodies to the core and NS3 antigens appeared earlier and persisted longer than those to C100 and NS5 after HCV infection. The relationship of antibody response to viremia and hepatic dysfunction was investigated in 27 children by using the polymerase chain reaction assay. Five children whose tests results were negative for all four antigens did not have viremia or hepatic dysfunction; 13 of the 16 children with positive results for the four antigens had both viremia and hepatic dysfunction. Five of the six children whose serum had the core and NS3 antibodies but not either C100 or NS5, or both, had viremia, and three of them also had hepatic dysfunction. These results suggest that detection of antibodies to the core and NS3 antigens is useful for the serologic diagnosis of HCV infection and that both antibodies are more related to viremia than are the antibodies to C100 and NS5. In addition, viremia is strongly associated with hepatic dysfunction.