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L H Perrin

Publications and source records attributed to L H Perrin.

At least 37 records · Page 2Linked to original sources
PubMed1990

Initiation of translation at a UAG stop codon in the aldolase gene of Plasmodium falciparum.

The gene coding for the key glycolytic enzyme fructose-1,6-diphosphate aldolase of the human malaria parasite Plasmodium falciparum lacks a functional AUG initiation codon for translation. Protein sequences of natural or in vitro translated aldolase include the candidate start methionine residue at internal positions. No additional AUG start codon is found in genomic DNA, cDNA or mRNA sequences. Instead, a UAG chain termination codon is recognized as the start signal of protein synthesis in vivo and in vitro.

Amino Acid Sequence↗
PubMed1990

Development of a haptoglobin ELISA. Its use as an indicator for malaria.

Hypo- or ahaptoglobinemia, a common phenomenon in tropical countries, is mainly due to malaria induced hemolysis. We have recently shown that the prevalence of hypohaptoglobinemia is a useful epidemiologic indicator in malaria endemic areas. The main limitation to the practical utilisation of this indicator is the available methodologies. Here we describe a sandwich ELISA for the determination of haptoglobin concentrations which is easy to perform, sensitive and requires a minimal amount of equipment. With this test system it is possible to detect haptoglobin in serum at a lower limit of 100 micrograms/ml for 10(-4) dilutions and of less than 1 micrograms/ml for 10(-2) dilutions. This represents at least 200 fold increase in sensitivity as compared to radial immunodiffusion.

Enzyme-Linked Immunosorbent Assay↗
PubMed1990

Expression, purification, biochemical characterization and inhibition of recombinant Plasmodium falciparum aldolase.

The energy metabolism of the blood stage form of the human malaria parasite Plasmodium falciparum is adapted to the host cell. Like erythrocytes, P. falciparum merozoites lack a functional citric acid cycle. Generation of ATP depends therefore fully on the glycolytic pathway. Aldolase is a key enzyme of this pathway and a high degree of sequence diversity between parasite and host makes it a potential drug target. We have expressed the enzyme in its tetrameric form in Escherichia coli and the catalytic constants Vmax and Km of the recombinant enzyme correspond to the constants of parasite-derived aldolase. Rabbit antibodies against the recombinant P. falciparum aldolase inhibit the natural enzyme and no cross-reaction with human aldolase is detectable. Both the recombinant and the natural protein bind to the cytosolic domain of the band 3 membrane protein in vitro. A 19-residue synthetic peptide corresponding to the sequence of the binding domain of band 3 is an inhibitor when included in the binding assay. In addition, this peptide inhibits the catalytic activity of recombinant P. falciparum aldolase when assayed in a buffer system devoid of anions such as chloride or phosphate. The band 3-derived peptides compete with the aldolase substrate fructose-1,6-diphosphate for binding, suggesting that both reagents have a high affinity for the substrate pocket. A similar sequence motif exists in P. falciparum actin II. A 19-residue peptide corresponding to this sequence is also an inhibitor which could suggest that the P. falciparum aldolase can associate with the cytoskeleton of the parasite or of the host.

Amino Acid Sequence↗
PubMed1989

Asexual blood stage vaccines: from merozoites to peptides.

Asexual blood stage proliferation is responsible for the morbidity and mortality associated with malaria infection in man. These developmental stages are therefore obvious targets for the development of malaria vaccines. Several asexual blood stage components have been identified as potential candidates for the development of vaccines and some of them have been shown, following immunization, to induce at least partial protection in a variety of Plasmodium-host combinations. Studies on defined parasite components and on synthetic peptides derived from them have revealed new insights at the molecular level into parasite mechanisms involved in propagation and survival in the infected host, and into the interaction between parasite components and the host immune system. Practical application of these findings is likely to provide the basis for the design of more appropriate antigens for the development of vaccines.

Animals↗
PubMed1988

[Reversal of positive serology for human immunodeficiency virus (HIV). Apropos of 2 case reports].

The medical history and laboratory data of two persons who have been in contact with HIV-I positive carrier individuals are reported. The serologic data of successive serum samples collected from these persons were first negative, then positive (including antibodies directed against Gag and Env gene products), and finally negative for presence of anti-HIV-I antibodies. Physical examination and other laboratory data, including absolute number of CD4 lymphocytes/mm3, were within the normal range in these two individuals, who presented a reversal of positive serology for HIV-I.

AIDS Serodiagnosis↗
PubMed1988

Correlation of T and B cell activities in vitro and serum IL-2 levels in systemic lupus erythematosus.

There have been only a few studies indicating that B cell hyperactivity in SLE could depend on Th cell activation. In particular, circulating CD4+ cells were found to express Ia. Our own previous investigations have shown that the decreased IL-2 secretion capacity in vitro of CD4+ cells in SLE is restored to normal when the cells are rested for a few days in culture. This suggested the presence of activated, exhausted T cells in the circulation. In this study, we report several observations concerning T cell function in SLE. 1) Decreased IL-2 secretion in vitro of PBL was found to correlate significantly with increased spontaneous IgG secretion of such cells; immunosuppressive treatment of 22 patients with steroids plus cyclosporin A led, to a large extent, to a correction of both abnormalities. 2) 9 of 18 patients with active disease (and low IL-2 secretion in vitro) had increased IL-2 levels in serum by ELISA; two sera contained IL-2 biologic activity, and chromatography of one serum showed IL-2 in a high molecular size complex (Mr approximately 50,000) dissociable with 6 M urea. The serum levels of IL-2R were also frequently increased, even in less active SLE. 3) In cell culture experiments, the IgG secretion by purified B cells from 6 of 9 patients with active SLE was increased by autologous T cells acting either alone (3 patients) or synergistically with rIL-2 (3 patients); the B cells from all 9 patients showed increased IL-2 responsiveness compared with blood donor B cells. Taken together, these results provide new evidence that increased T cell activation occurs and plays a role in SLE.

Adult↗
PubMed1988

Aldolase activity of a Plasmodium falciparum protein with protective properties.

Immunization with a 41-kilodalton blood stage antigen (p41) of Plasmodium falciparum induces immunity to malaria in monkeys. However, antigenic polymorphism and repetitive amino acids commonly found in protective antigens complicate vaccine development. The gene encoding p41 has now been cloned and analyzed. Sequencing and hybridization studies revealed that the gene structure is highly conserved in 14 parasite isolates from three continents. This finding and the lack of repetitive amino acids in the translated DNA sequence may indicate that p41 has an essential function. In this study the protein was found to be 60 percent homologous to the key glycolytic enzyme aldolase from vertebrates, and the affinity-purified p41 protein from parasites showed aldolase activity.

Animals↗
PubMed1988

Variation in p126, a parasitophorous vacuole antigen of Plasmodium falciparum.

We describe a cDNA clone expressing part of p126, a parasitophorous vacuole antigen of Plasmodium falciparum that is processed to smaller fragments about the time of schizont rupture. The amino acid sequence includes determinants that are antigenic during the course of infection. The sequence contains a string of serine residues but no other repetitive elements. Comparison of the sequence to a previously published sequence demonstrates conserved and variable sequence elements. The genomic context of the single copy gene is conserved in six different isolates. p126 is shown to be identical to Pf140, an antigen previously demonstrated to partially protect Saimiri monkeys against P. falciparum infection.

Amino Acid Sequence↗
PubMed1987

Limiting dilution assay for human B cells based on their activation by mutant EL4 thymoma cells: total and antimalaria responder B cell frequencies.

The analysis of human B cell responses at the clonal level (limiting dilution assay) is still technically difficult. In the present study we report on a culture system that leads to activation, proliferation and differentiation into antibody-secreting cells (ASC) of about 90% of B cells from peripheral blood or spleen. In this system, B cells are cultured in the presence of a mutant subclone of the mouse thymoma EL4 for B cell activation and human T cell plus macrophage supernatant as source of proliferation and differentiation factors. ASC precursors generating clonal responses of IgM only, IgM plus IgG, or IgG only occurred at a ratio of about 6:3:1. The mean clone size was 380 cytoplasmic Ig+ cells; the mean amount of Ig secreted per clone was 20 ng. Furthermore, it has been found using this system that a considerable proportion of peripheral blood B cells from individuals with a history of malaria infection could generate clones of anti-malaria (Plasmodium falciparum) ASC (range of 0.1 to 1%, n = 6). In a control group of blood donors the corresponding frequencies were 10 times lower (range of 0.01 to 0.1%, n = 9). These results show that the EL4 culture system can be applied to the investigation of the human B cell specificity repertoire and of priming effects such as result from infectious disease.

Adult↗
PubMed1986

Immunization with synthetic peptides of a Plasmodium falciparum surface antigen induces antimerozoite antibodies.

Polypeptides expressed on the surface of merozoites, the invasive stage of the asexual blood cycle, are good candidates for the development of malaria vaccines. Five synthetic peptides with predetermined specificity deduced from a genomic DNA clone coding for the NH2-terminal portion of the main merozoite surface polypeptide of Plasmodium falciparum were evaluated for their capability to raise antibodies that react with the P. falciparum merozoites. Antibodies induced by two of the peptides (3 and 5) reacted with the membrane surfaces of seven of seven isolates of P. falciparum from different geographic areas. Antibodies against peptide 4, which contains a repeated amino acid sequence (Gly-Gly-Ser and Val-Ala-Ser), reacted with six of seven isolates. Structural analysis of the deduced polypeptides suggests that peptide 3 is exposed at the surface of merozoites. When it was used to immunize monkeys, three of the four animals were partially protected from a challenge infection that induced a fulminant infection in control animals.

Amino Acid Sequence↗
PubMed1986

Defined Plasmodium falciparum antigens in malaria serology.

The study evaluates three enzyme-linked immunosorbent assays (ELISA) of malaria antigens suitable for use in large-scale epidemiological studies. Results obtained using sera from 567 persons from the Gambia indicated that the micro-ELISA method using parasitized red blood cell extract did not reliably quantitate antimalarial antibodies, especially in young children. In contrast, two micro-ELISA methods that employed purified, defined antigens (a polypeptide of M(r) = 41 000 present in rhoptries, and a 31-1 fusion polypeptide corresponding to a merozoite surface antigen) permitted the precise determination of antimalarial antibodies in both adults and children. Problems and advantages associated with the use of the M(r) = 41 000 and 31-1 antigens for the determination of antimalarial antibodies are discussed.

Antigens, Protozoan↗
PubMed1985

Cloning and expression in Escherichia coli of a surface antigen of Plasmodium falciparum merozoites.

A complementary DNA library was constructed from mRNA purified from asexual blood forms of Plasmodium falciparum. Among the members of this library we have identified a plasmid (pMC31-1) coding for a polypeptide exposed at the surface of merozoites, the invasive stage of the asexual cycle. This plasmid was identified by direct expression using both polyclonal and monoclonal antibodies specific for a schizont polypeptide of 200 kd which has been shown to be processed to an 83-kd polypeptide expressed at the surface of merozoites. The cDNA portion of the pMC31-1 plasmid hybridizes with DNA from three isolates of P. falciparum. Antisera raised against extracts of Escherichia coli harbouring pMC31-1 react with surface and internal structures of schizonts and with the surface of merozoites from all the isolates of P. falciparum examined. These results suggest that plasmid pMC31-1 encodes an antigen of value for the development of a vaccine against malaria.

Amino Acid Sequence↗
PubMed1985

Immunization with a Plasmodium falciparum merozoite surface antigen induces a partial immunity in monkeys.

Saimiri monkeys immunized with a Plasmodium falciparum merozoite polypeptide of 41 kD mol wt are resistant to a blood challenge infection that induces a fulminant infection in control monkeys. The sera of the immunized monkeys reacted, as shown by the indirect immunofluorescence technique, with the apical part of the merozoites from five isolates or clones of P. falciparum. Whether the immunogen was dissolved in nonionic detergent (NP-40) or in sodium dodecyl sulfate (SDS) had a marked influence on the level of protection in immunized monkeys. Thus, monkeys immunized with the antigen solubilized in a nonionic detergent developed much lower parasitemia than monkeys immunized with denatured antigen (antigen eluted from SDS polyacrylamide gel electrophoresis).

Animals↗
PubMed1984

Antimalarial immunity in Saimiri monkeys. Immunization with surface components of asexual blood stages.

Plasmodium falciparum polypeptides of 200 and 140 K mol wt exposed at the surface of merozoites and/or schizonts were purified by affinity chromatography and by electroelution from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Monkeys were separated into three groups of four and immunized either with one of the two polypeptides or with saline (control). After intravenous challenge with 2.5 X 10(7) P. falciparum asexual blood stages, two monkeys of the control group had to be treated and two recovered spontaneously after peak parasitemia of 9 and 11%. The four monkeys immunized with the 140 K polypeptide recovered without treatment after peak parasitemia between 1.5 and 4.5%. Monkeys immunized with the 200 K polypeptide had similar peak parasitemia except one monkey who suffered from a large skin excoriation and who recovered spontaneously after a peak parasitemia of 11%. Prechallenge sera of the immunized monkeys reacted only with the polypeptide used for immunization except for one serum of the 140 K group, which precipitated an additional polypeptide of 39 K, and a polypeptide of 31 K weakly precipitated by the four sera of monkeys immunized with the 200 K polypeptide. The relatedness between the 200 and 140 K polypeptides was investigated using tryptic digestion and reverse phase chromatography. No clear analogy was found between the two polypeptides, which suggests that immunization with either of two independent surface components of P. falciparum asexual blood stages is able to induce at least a partial protective immunity in immunized hosts.

Animals↗