Ginette Jaureguiberry

Identification of a family of Rab G-proteins in Plasmodium falciparum and a detailed characterisation of pfrab6

As a first step towards developing a set of compartment-specific probes for studying protein trafficking in the malaria-infected erythrocyte, we describe here a family of Plasmodium falciparum Rab proteins. We characterise in detail P. falciparum Rab6 (PfRab6) a marker which in other cells is specific for the Golgi/trans Golgi network. Although PfRab6 mRNA is expressed throughout the intraerythrocytic cycle, maximal expression occurs at the trophozoite stage. Immunofluorescence microscopy shows that the distribution of PfRab6 changes during the final stages of parasite maturation, coalescing into multiple foci, each of which is associated with the nucleus of a forming daughter parasite.

PCR detection of Plasmodium falciparum by oligonucleotide probes

Abstract PCR experiments using rRNA sequence-specific oligonucleotides were used to detect Plasmodium falciparum DNA and Plasmodium vivax DNA from cultures and blood samples.

Plasmodium falciparum: Isolation and characterization of a 55-kDa protease with a cathepsin D-like activity from P. falciparum

Native electrophoresis followed by imprint digest method using hemoglobin as substrate allowed the detection of parasite hemoglobinase activity at acidic pH (3.9 to 5). This protease was inhibited specifically by pepstatin A and insensitive to other protease inhibitors. The molecular weight determination using modified SDS-PAGE followed by imprint digest method, demonstrated a single area of activity at 55-58 kDa, similar to cathepsin D characterized in eucaryotic cells. The parasitic origin has been shown by radiolabeling experiments with [35S]-methionine. The 55-kDa protein was immunoprecipitated by a rabbit anti-cathepsin D serum.

The polymorphic 11.1 locus of Plasmodium falciparum

Clone pPF11.1 encodes a Plasmodium falciparum antigen expressed during the intraerythrocytic cycle and containing tandem repeats of a 9 amino acid unit. We report here an analysis of the genomic region specific for 11.1, which extends over 30 kb. It contains two blocks of repeats, spanning 13 kb and 9 kb. The restriction map suggests that the locus may result from a gene duplication. The 11.1 region is present in all P. falciparum strains examined so far. Southern analysis of 8 distinct isolates indicates that the locus is highly polymorphic. Thus the pPF11.1 repeats constitute a sensitive and discriminating probe to type P. falciparum strains.

Small GTP-binding proteins in Plasmodium falciparum

During its erythrocytic life cycle Plasmodium falciparum exchanges compounds with host cells through phagocytosis and exocytosis. In eucaryotic cells, small GTP-binding proteins of the Ras superfamily appear to be involved in different steps of membrane trafficking and in intracellular signals. In this paper, we investigate the Rab4, Rab6 and Ras-related proteins in P falciparum infected red cells. We report that P falciparum Rab and Ras-related proteins could be distinguished from their counterparts by iso-electrofocusing and immunoblotting. The localization of P falciparum Rab 4 and Rab 6 was studied by immunogold electron microscopy on ultrathin frozen sections of infected red blood cells. Rab4 parasite-related protein was found associated with the membranes of early endosome-like structures near the parasite plasma membrane. Rab6-related protein was associated with the Golgi/trans Golgi network, as already suggested by immunofluorescence microscopy studies and Ras-related protein was cytoplasmic and plasma membrane-associated. These results are in accordance with their mammalian counterparts and support the implication of Rab-related proteins in vesicular trafficking in Plasmodium.

An alternative to DNA extraction for the diagnosis of Pneumocystis carinii pneumonia by polymerase chain reaction using a new oligonucleotide probe

We have used new specific primers and probe in a polymerase chain reaction (PCR) followed by Southern blot assays to detect Pneumocystis carinii in human bronchoalveolar lavage samples obtained from HIV-infected patients with pulmonary symptoms. To facilitate the procedure we developed a filtration technique without DNA extraction yielding a high sensitivity (18/18 positive results). The high specificity of the technique was shown by testing immunosuppressed patients without P. carinii pneumonia.