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Biomedical subjects

M Wahlgren

Publications and source records attributed to M Wahlgren.

88 records · Page 5Linked to original sources
PubMed1984

Human antibodies to a Mr 155,000 Plasmodium falciparum antigen efficiently inhibit merozoite invasion.

IgG from a donor clinically immune to Plasmodium falciparum malaria strongly inhibited reinvasion in vitro of human erythrocytes by the parasite. When added to monolayers of glutaraldehyde-fixed and air-dried erythrocytes infected with the parasite, this IgG also displayed a characteristic immunofluorescence restricted to the surface of infected erythrocytes. Elution of the IgG adsorbed to such monolayers gave an antibody fraction that was 40 times more efficient in the reinvasion inhibition assay (50% inhibition titer, less than 1 microgram/ml) than the original IgG preparation. The major antibody in this eluate was directed against a parasite-derived antigen of Mr 155,000 (Pf 155) deposited by the parasite in the erythrocyte membrane in the course of invasion. A detailed study of IgG fractions from 11 donors with acute P. falciparum malaria or clinical immunity revealed the existence of an excellent correlation between their capacities to stain the surface of infected erythrocytes, their titers in reinvasion inhibition, and the presence of antibodies to Pf 155 as detected by immunoblotting. No such correlations were seen when the IgG fractions were analyzed for immunofluorescence of intracellular parasites or for the presence of antibodies to other parasite antigens as detected by immunoprecipitation of [35S]methionine-labeled and NaDodSO4/PAGE-separated parasite extracts. The results suggest that Pf 155 has an important role in the process of erythrocyte infection and that host antibodies to this antigen may efficiently interfere with this process.

Adolescent↗
PubMed1983

A comparison of knobby (K+) and knobless (K-) parasites from two strains of Plasmodium falciparum.

Erythrocytes infected with Plasmodium falciparum develop knob-like protrusions on their membranes. Knobby (K+) parasites of the FCR-3 (Gambian) strain have been shown to possess a histidine-labelled protein of apparent molecular weight 80 000 which is absent from knobless (K-) variants of the same strain. Here we report similar findings with K+ and K- parasites of another strain, the Malayan Camp strain, and also with cloned K+ and K- parasites of the FCR-3 strain. A histidine-labelled protein unique to the two K+ parasites was identified as a broad band with an apparent molecular weight of 89 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The presence of this protein in both K+ Malayan Camp parasites and K+ FCR-3 (Gambian) parasites and its absence from K- parasites of both strains is consistent with this protein being a major component of knobs.

Animals↗
PubMed1983

Monoclonal anti-parasite and anti-RBC antibodies produced by stable EBV-transformed B cell lines from malaria patients.

To produce human monoclonal antibodies associated with infectious disease, peripheral blood lymphocytes (PBL) from patients with Plasmodium falciparum malaria were transformed with EB-virus in vitro. To enrich for malaria-specific B cells, PBL were incubated for 3 days with unsoluble P. falciparum antigen before EBV-transformation. Furthermore, cyclosporin A was added during and after transformation to eliminate T cell suppression of B cell growth. Microcultures were screened for antibodies against blood stage antigens of P. falciparum or of noninfected erythrocytes by ELISA and indirect immunofluorescence. Cultures producing anti-P. falciparum and/or anti-erythrocyte antibodies were developed from the lymphocytes of eight patients, including some individuals with their first infection. Positive cultures were cloned and propagated for several weeks. Seven of 15 clones producing antibody at a stable rate have now been kept in cultures for more than 1 yr. Of six cultures analyzed in detail, all produced IgM antibodies of either K or lambda isotype. Although three clones were monoclonal after one cloning, three were oligoclonal. Of the former, two produced P. falciparum-specific antibodies directed to an antigen associated with the surface of merozoites. One of the oligoclonal cultures produced anti-erythrocyte antibodies, and it was probably reacting with spectrin.

Antibodies, Monoclonal↗
PubMed1983

Characterization of the humoral immune response in Plasmodium falciparum malaria. I. Estimation of antibodies to P. falciparum or human erythrocytes by means of microELISA.

An enzyme linked immunosorbent assay (ELISA) has been developed to estimate disease related antibodies in sera from malaria patients or individuals living in malaria endemic areas. As antigen, Percoll enriched fractions (mainly late trophozoites, schizonts) from Plasmodium falciparum in vitro cultures were used. An ELISA with ghosts from normal human red blood cells (RBC) was performed in parallel. One hundred and seventy-five sera were tested for their reactivity with either one of the two antigens. Seven sera from patients with acute P. falciparum infection were negative. Most of these had been taken very early in infection and consecutive samples taken later usually were positive. The antibodies reacting with the P. falciparum antigen had a high parasite specificity as indicated by inhibition and absorption experiments. Many sera also had elevated levels of antibodies specific for RBC antigens. A correlation, most pronounced in the IgM system, was also seen between the anti-RBC and the anti-P. falciparum antibody levels.

Animals↗
PubMed1983

Characterization of the humoral immune response in Plasmodium falciparum malaria. II. IgG subclass levels of anti-P. falciparum antibodies in different sera.

The IgG subclass levels of anti-Plasmodium falciparum antibodies in human sera were determined in ELISA with monoclonal mouse antibodies specific for the human IgG subclasses as analytical reagents. The parasite antigen was a trophozoite/schizont enriched preparation of in vitro cultivated P. falciparum. Serum samples were from Swedish malaria patients and adult Liberians. Parasite specific antibodies were found in all four subclasses. Relatively elevated levels of IgG1 antibodies were found both in Swedish patients and in the Liberians. Relative to the Liberians, high IgG2 antibody levels were seen in most Swedish patients. In Liberian sera but not in those from Swedish patients elevated IgG3 levels were found. In two Swedish patients followed consecutively for a period of 15 weeks, elevated levels of IgG1 and IgG3 antibodies were seen after relapse. No differences between the groups in regard to the levels of IgG4 antibodies were noticed. The differences between the Swedish patients and the Liberians were also in part reflected by differences in the total amounts of the four IgG subclasses.

Animals↗
PubMed1983

Studies on the specificity of anti-erythrocyte antibodies in the serum of patients with malaria.

Sera from patients with Plasmodium falciparum, P. vivax or P. ovale malaria were selected according to their high levels of antibodies against human erythrocyte membranes as measured in a microELISA. The specificity of the anti-erythrocyte antibodies in these sera and two normal sera was investigated by means of an immunoblotting technique in combination with SDS-polyacrylamide gel electrophoresis. All the patients' sera as well as the control sera contained antibodies against several erythrocyte polypeptides. As compared with normal sera, most malaria sera showed elevated levels of antibodies against polypeptides of 80K, 70K, 40K and 28K molecular weights. Two sera reacted strongly against a polypeptide with an electrophoretic mobility similar to the alpha subunit of spectrin. One serum showed strong reaction and several other sera, including normal sera, showed weak reaction against a 45K molecular weight polypeptide corresponding to actin. No pervading differences were seen in the pattern of specificities of the anti-erythrocyte ghost antibodies between sera from patients with P. falciparum, P. vivax or P. ovale infections.

Antibody Specificity↗
PubMed1981

Asymptomatic congenital Chagas' disease in a 5-year-old child.

A case of asymptomatic Chagas' disease is a 5-year-old boy is described. The boy was born in Romania in 1975 and had never visited an area where Chagas' disease is endemic. It is important bear in mind the possibility of transplacental transmission, in view of increasing number of immigrants and refugees coming from South and Central America.

Chagas Disease↗
PubMed1975

Firearm residue detection by instrumental neutron activation analysis.

Work leading to an improved technique for firearm discharge residue detection by neutron activation is described. The troublesome and time-consuming postirradiation chemistry has been eliminated; also, sample size has been minimized to accommodate some 130 samples per irradiation capsule. To put the method in a proper perspective, previous work has been referenced and discussed.

Activation Analysis↗