PubMed Health⌕ Search

Biomedical subjects

P Rappelli

Publications and source records attributed to P Rappelli.

26 records · Page 2Linked to original sources
PubMed1996

Trichomonas vaginalis haemolysis: pH regulates a contact-independent mechanism based on pore-forming proteins.

There is a controversy in literature about involvement of secreted factors in the pathogenetic mechanisms of Trichomonas vaginalis, described mostly as contact-dependent. We found that the protozoan, under triggering conditions, is able to release molecules that lead to lysis without direct contact between parasite and target cells as a prerequisite. In this paper we characterize contact-independent cytotoxicity using the red blood cell as a cellular model. Contact-independent haemolysis is a phenomenon were pH exerts a key role, triggering the secretion of a lytic molecule and regulating its activity. A partial physicochemical characterization of the haemolytic factor suggests that a protein of M(r) > 30 kDa could be the effector responsible for damage. Furthermore, the parasite-induced membrane permeabilization, detected by measuring potassium escape from the target cell, and an effective osmotic protection by carbohydrates allowed us to relate the previously described pore-forming mechanism involved in contact-dependent cytotoxicity with the contact-independent lysis.

Animals↗
PubMed1995

Sequence of cDNA coding for a 65 kDa adhesive protein for the specific detection of Trichomonas vaginalis by PCR.

A Trichomonas vaginalis cDNA library was constructed and recombinant plaques were screened using rabbit immunoglobulins specific for P65, a protozoan protein involved in pathogenicity that we identified in a previous study. A 1.38 kilobases cDNA fragment coding for the P65 protein was cloned in E. coli and then sequenced. On the basis of of the sequence obtained, six primers were synthesised and used to set up a Polymerase Chain Reaction. The presence of a specific amplicon in all 30 clinical isolates tested shows that P65 is a conserved and stable gene. The reaction is highly sensitive (as few as 5 to 10 parasites can be detected) and specific for Trichomonas vaginalis; the gene coding P65 adhesin can be therefore considered a very good molecular target for polymerase chain reaction-based diagnostic purposes.

Animals↗
PubMed1993

Trichomonas vaginalis haemolysis: evidence of functional pores formation on red cell membranes.

We have investigated the mechanisms used by Trichomonas vaginalis to damage cellular membranes, using human erythrocytes as target cells. Haemolysis is a contact- and temperature-dependent phenomenon, and is inhibited in 4 mM EGTA. Osmotic protection experiments using carbohydrates with different molecular diameters as protectants demonstrated that the cytolytic activity of T. vaginalis is inhibited in 75 mM stachyose. On the basis of our data, we hypothesize a cytopathic mechanism mediated by the formation of functional pores into the target membrane. Some of the Trichomonas protein involved in haemolysis have been immunologically characterized.

Animals↗
PubMed1993

Reduced microbicidal and anti-tumour activities of human monocytes after ingestion of Plasmodium falciparum-infected red blood cells.

Oxidatively stressed red blood cells (RBC) and Plasmodium falciparum-infected RBC (PRBC) are avidly phagocytosed by human peripheral monocytes. Following the ingestion of PRBC the monocytes' ability to phagocytose PRBC and to generate aggressive oxidative compounds is severely impaired. In the present work the microbicidal and anti-tumour capacities of monocytes fed with diamide-treated RBC and PRBC harbouring mature (trophozoite) parasites have been investigated. The capacity of the latter, but not of the former, to phagocytose Escherichia coli and Staphylococcus aureus and to kill them, as well as ingested Candida albicans cells intracellularly, was found to be markedly impaired. Monocytes that have ingested PRBC had a significantly reduced cytostatic and cytolytic activities against a lymphoblastic tumour cell line. Monocytes fed with oxidatively stressed RBC had normal or sometimes even greater anti-tumour activities. Monocytes that have ingested PRBC showed a reduced capability to produce superoxide following stimulation with phorbol ester. Such impairment in monocyte functions may explain the reduced antibacterial and anti-tumour activities of monocytes in malaria patients, and could be consequential to their ability to resist bacterial infections and to provide means for the control of tumour development in those patients.

Animals↗
PubMed1992

Phenotypic variation of surface antigenic determinants in Trichomonas vaginalis detected by monoclonal antibodies.

We produced a large panel of murine monoclonal antibodies against surface determinants of Trichomonas vaginalis using the hybridoma technique. An immunoenzymatic technique (E.L.I.S.A.) was used to screen positive hybrid cells producing specific antibodies against the protozoan surface. Eleven monoclonal antibodies (Mabs) out of seventy-seven positives were further characterized. We tested antibody reactivity in order to investigate the antigenic variance among 13 different strains of Trichomonas vaginalis of different geographic origin. To elucidate the complexity of antigenic expression in Trichomonas vaginalis, further characterization of the antigenic pattern in our 13 clinical isolates was carried out by immunoblotting techniques. We demonstrate that some monoclonal antibodies react with antigens varying in molecular weight in the different strains tested. We also demonstrate the pivotal role of protozoan proteases in antigenic rearrangement.

Animals↗
PubMed1991

The use of polyclonal activators in the production of murine monoclonal and polyclonal antibodies.

We propose a new immunization method to stimulate a strong immune response against weak or diluted antigens. This technique is based on stimulation with polyclonal activators before exposure to the antigens. We also discuss the efficiency of various types of mitogen with particular regard to their capacity to produce monoclonal antibodies and serum antibodies. A specific immune response against soluble antigens is increased by pretreating mice with PPD. This preactivation permitted us to obtain monoclonal antibodies against weak antigens in a few days. No monoclonal antibodies were obtained by inoculating weak antigens or the activators by themselves.

Adjuvants, Immunologic↗
PubMed1991

Molecular probe for identification of Trichomonas vaginalis DNA.

Trichomoniasis is one of the most widespread sexually transmitted diseases in the world. Diagnosis can be achieved by several methods, such as direct microscopic observation of vaginal discharge, cell culture, and immunological techniques. A 2.3-kb Trichomonas vaginalis DNA fragment present in strains from diverse geographic areas was cloned and used as a probe to detect T. vaginalis DNA in vaginal discharge by a dot blot hybridization technique. This probe was specific for T. vaginalis DNA. It recognized strains from two regions in Italy (Sardinia, Piemonte) and from Mozambique (Africa). In addition, our probe did not cross-react with bacterial (Escherichia coli, Enterococcus spp., group B streptococci, Gardnerella vaginalis, Neisseria gonorrhoeae, Chlamydia trachomatis, and Lactobacillus spp.), viral (herpes simplex virus type 2), fungal (Candida albicans), protozoan (Entamoeba histolytica, Giardia lamblia, Plasmodium falciparum, Leishmania major, and Leishmania infantum), or human nucleic acids. The probe reacted with Pentatrichomonas hominis and Trichomonas foetus. The limit signal recognized by our probe corresponded to the DNA of 200 T. vaginalis isolates. The 2.3-kb probe was used in a clinical analysis of 98 samples. Of these, 20 samples were found to be positive both with the probe and by cell culture, and only 14 of these were positive by a standard wet mount method.

Animals↗