Characterization of protective and non-protective surface membrane carbohydrate epitopes of Schistosoma mansoni

We have produced a number of monoclonal antibodies, protective and non-protective, which recognize a complex of schistosomula antigens, including the 38 kDa antigen. Eight different protective and non-protective monoclonal antibodies, varying in isotypes, were used in the binding assays. Lectin inhibition studies suggested that the monoclonal antibodies probably recognized carbohydrate epitopes on the antigen(s). Immunoprecipitation studies showed that at least two of the monoclonal antibodies recognized different epitopes on the same molecule. Additionally, we tested for monoclonal antibody binding after the antigens were treated with; 1) proteases, 2) periodate, 3) various exo- and endoglycosidases, 4) mild acid hydrolysis. We also tested for binding of the antibodies to keyhole limpet hemocyanin (KLH). Using the 8 monoclonal antibodies as probes, we were able to define at least 4 different carbohydrate epitopes related to the protective monoclonal antibodies, and at least one epitope which is seen by the non-protective antibodies. The epitope seen by the non-protective antibodies was shown to be cross-reactive with epitopes on KLH. These results demonstrate the importance of epitope mapping studies for any defined vaccine.

Effects of irradiation and tunicamycin on the surface glycoproteins Schistosoma mansoni

The cercarial glycocalyx and schistosomulum surface contains a number of glycoproteins which are expressed in very variable amounts within a parasite population. Tunicamycin inhibits glycoprotein synthesis of schistosomula if the parasites are incubated for 24hr with the drug (10µg ml[raised to the power of -1]). An unexpected increase in lectin binding to the parasite surface was observed but no other changes were detected. Schistosomula treated in this way did not develop in the host past the lung stage. Ultraviolet irradiation (400µW min cm[raised to the power of-2]) also inhibited glycoprotein synthesis. Synthesis of other proteins, and in particular heat shock proteins, were also inhibited. Sera from mice (NIH strain) infected with irradiated cercariae contained antibodies which bound to normal schistosomula with lower affinity than to irradiated parasites. This is evidence that irradiation modifies the surface and secreted glycoproteins of schistosomula, so they are processed in a different way to normal glycoproteins by the host's immune system. The effects of irradiation on heat shock protein synthesis may allow the parasite to release a variety of proteins and glycoproteins in abnormal conformations. This may explain the enhanced immunogenicity of irradiated cercariae.

The surface charge of trypanosomatids of the genus trypanosoma

Cell electrophoresis was used for determionation of the electrophoretic mobility (EPM) of epimastigo and trypamastigote forms of several isolates of Trypanosoma cruzi and some stocks of other members of the Schizotrypanum subgenus, such as T. dionisii, T. vespertilionis and T. myoti. The EPM of T. bruceli, T. rangeli, and T. conorhini was also determined. The results obtained show that the EPM values con be useful to distinguish the parasites.

Lectin receptors distribution in the surface membrane of Trypanosoma cruzi blood forms collected from mice submitted to specific treatment

The author investigated the distribution of lectin receptors on Trypanosoma cruzi blood forms collected from mice inoculated with, respectively, the drug-resistant and drug-sensitive strains VL-10 and CL, and treated with the two standard active nitroheterocyclic compounds nifurtimox and benznidazole used for treatment of human Chagas' disease. Blood trypomastigotes purified in Fycoll-Hypaque were incubated with fluorescein-labelled lectins Con A, WGA, EE, WFA, TPA and PNA and then microscopically examined. Neither qualitative or quantitative differences in the fluorescence intensity could be detected between parasites from VL-10 and CL strains submitted or not to treatment. The results suggest that both strains do not differ in their surface membrane carbohydrate moieties. Moreover, the rapid clearance of blood forms the drug-sensitive strain in animals treated with singlo doses of both compounds is not likely to depend on membrane alterations expressed by changes in the carbohydrate components. furthermore, resistance or sensitivity to drugs is not apparently related to carbohydrate distribution on T. cruzi blood forms.

Report of Balanorchis anastrophus in Pará state with surface topography by scanning electron microscopy

Balanorchis anastrophus Fischoeder, 1901 from the reticulum from Bos taurus is reported for the first time in State of Pará, Brazil. The surface topography as revealed by scanning electron microscopy is presented.

Polypeptides reactive with antibodies eluted from the surface of Babesia bovis-infected erythrocytes

A technique was sought that would enable identification of surface-exposed parasite antigens on Babesia bovis-infected erythrocytes (BbIE) that are not detectable by surface-specific immunoprecipitations. Antibodies which bind to the surface of BbIE were recovered from intact cells using a low pH wash procedure. The eluted antibodies were then used in conventional immunoprecipitation assays to identify parasite-synthesized polypeptides carrying epitopes that are exposed on the surface or are cross reactive with shuch epitopes. The results of these experiments support our previous data, obtained using a surface-specific immunoprecipitation technique, in the identification of a repertoire of parasite-derived antigens on the surface of infected erythrocytes (Allred et al., 1991). In addition, two polypeptides of Mr 68,000 and 185,000 were identified wich react strongly with the eluted antibodies but wich are not detected by surface-immunoprecipitation. These data illustrate the potential of this approach for identification of parasite polypeptides wich carry epitopes exposed on, or cross-reactive with exposed epitopes of the infected erythrocyte surface.

A malaria merozoite surface protein (MSP1)-structure, processing and function

Merozoite surface protein-1 (MSP-1, also referred to as P195, PMMSA or MSA 1) is one of the most studied of all malaria proteins. The proteins. The protein is found in all malaria species investigated and structural studies on the gene indicate that parts of the molecule are well-conserved. Studies on Plasmodium falciparum have shown that the protein is in a processed form on the merozoite surface, a result of proteolytic cleavage of the large percursor molecule. Recent studies have identified some of these cleavage sites. During invasion of the new red cell most of the MSP1 molecule is shed from the parasite surface except for a small C-terminal fragment which can be detected in ring stages. Analysis of the structure of this fragment suggests that it contains two growth factor-like domains that may have a functional role.

Human IgG responses against the N-terminal region of Merozoite Surface Protein 1 of Plasmodium vivax

The complete primary structure of the gene encoding the Merozoite Surface Protein 1 of Plasmodium vivax (PvMSP-1) revealed the existence of interspecies conserved regions among the analogous proteins of other Plasmodia species. Here, three DNA recombinant clones expressing 50, 200 and 500 amino acids from the N-terminal region of the PvMSP-1 protein were used on ELISA and protein immunoblotting assays to look at the IgG antibody responses of malaria patients from the Brasilian amazon region of Rondônia. The results showed the existance of P. vivax and P. falciparum IgG antibodies directed against PvMSP-1 antigenic determinants expressed in the clones containing the first 200 and the following 500 amino acids of the molecule, but not within the one expressing the most N-terminal 50 amino acids. Interestingly, there was no correlation between the levels of these IgG antibodies and the previous number of malaria infections.

Naturally acquired antibodies against the major merozoite surface coat protein (MSP-1) of Plasmodium falciparum acquired by residents in an endemic area of Colombia

A preliminary baseline epidemiological malaria survey was conducted in the village of Punta Soldado, Colombia. Parasite prevalence and density as well as serological data were obtained from 151 asymptomatic children and adults. Fifty individuals were infected with Plasmodium falciparum. The mean parasite density was 184 parasites/mm3. Greater than 90 of the sample population were P. falciparum antibody positive as detected by the indirect immunofluorescent antibody test (IFAT). The enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies against the major merozoite surface protein (MSP-1) of P. falciparum. In this population, anti-MSP-1 antibody concentration is acquired in an age dependent manner with equal immunogenicity to both the N- and C-terminal regions of the molecule. Infection at the time of sampling was associated with a higher anti-MSP-1 antibody concentration than that found in non-infected individuals. Further studies are planned to assess the role of immune and non-immune factors in limiting the number of cases of severe malaria seen in this population.