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J Gysin

Publications and source records attributed to J Gysin.

At least 55 records · Page 3Linked to original sources
PubMed1990

Functional characterization of the antibody-mediated protection against blood stages of Plasmodium falciparum in the monkey Saimiri sciureus.

The squirrel monkey Saimiri sciureus is one of the World Health Organization recommended experimental models of Plasmodium falciparum blood stage infection. Anti-malaria antibodies developed by this host after a drug-controlled infection play an important part in the acquired protection against the P. falciparum blood stages. Furthermore, the use of two anti-Saimiri immunoglobulin (Ig) monoclonal antibodies (mAb) has permitted the differentiation between protective (mAb 3A2/G6) and non-protective (mAb 3E4/H8) antibodies, as shown by transfer experiments to recipient monkeys infected with blood stage parasites. In the present study we have established that protection conferred by the 3A2/G6+ protective Ig preparation is strictly associated with an in vitro opsonic activity. Such an opsonic activity is not detectable in the 3E4/H8+ non-protective Ig population. In addition, results indicate that the 3E4/H8+ non-protective Ig population competes with protective opsonic 3A2/G6+ Ig antibodies when co-incubated with parasitized red blood cells. Thus, it follows that protection can be directly correlated to the quantitative and qualitative fluctuation of the two Ig populations. When challenged with 1 x 10(8) P. falciparum-infected Saimiri red blood cells parasitemia occurred in 5 out of 12 Saimiri who were lacking detectable 3A2/G6+ opsonic antibodies in their sera. By employing antibodies against the human Fc receptor for IgG (Fc gamma R) in an in vitro phagocytic assay, we have been able to show that the principal receptor is Fc gamma RIII. Finally, we also show that in contrast to the situation in man, this receptor is present on circulating monocytes. These findings could lead to a different strategy in designing malaria vaccine candidates and also allow the possibility of predicting the outcome of immunization trials in Saimiri monkeys.

Animals↗
PubMed1990

[Use of New World Saimiri and Aotus monkeys in the development of an anti-malaria vaccine].

Saimiri and Aotus, two neotropical primates, are currently used in different domains of human malaria research. Here we present a simplified and non exhaustive enumeration of different aspects in concern of using these monkeys as experimental hosts, their availability, laboratory-bred animals versus wild-caught animals, their potential as experimental model in evaluating anti-malaria vaccine candidates, and some related activities at the Pasteur Institute.

Animals↗
PubMed1989

A two-site sandwich immunoradiometric assay of squirrel monkey (Saimiri sciureus) IgM using monoclonal antibodies.

Nine hybrid clones secreting antibodies to squirrel monkey (Saimiri sciureus) IgM were produced and two of these (1F1G5 and 5H11B3) were selected for further studies. These non-precipitating monoclonal antibodies reacted with two distinct repetitive antigenic determinants, probably of the conformational type, only present on the native or SDS-denatured IgM molecule. Reduction of the pentamer with 2-mercaptoethanol led to complete destruction of the corresponding epitopes. 1F1G5 antibodies from ascitic fluids were used in the purification of monkey IgM by affinity chromatography. The characteristics of 1F1G5 and 5H11B3 MAbs permitted the development of a solid-phase two-site immunoradiometric assay for the measurement of IgM levels in serum specimens taken from healthy animal donors of both sexes.

Animals↗
PubMed1988

Plasmodium vivax: cloning and expression of a major blood-stage surface antigen.

Plasmodium vivax is a highly prevalent malaria pathogen of man; the following report is the first to describe the cloning and expression of a major asexual erythrocytic stage antigen of this species. The screening of a genomic DNA expression library with a monoclonal antibody directed against a 200-kDa surface component (Pv200) of the more mature schizonts of P. vivax led to the selection of a recombinant bacterial clone which produced a fusion protein. Mouse and rabbit immune sera raised against the purified fusion protein recognized the 200-kDa parasite antigen on Western blots and reacted with the surface of segmenters by immunofluorescence. Sequencing of the 1.9-kb P. vivax DNA insert coding for this fusion protein revealed a 45-47% homology at the nucleotide level with the P. falciparum gene of a parasite surface antigen, Pf195, which has been shown to be a promising candidate for a malaria vaccine in primates and in man.

Amino Acid Sequence↗
PubMed1987

Characterization of a 96-kilodalton thermostable polypeptide antigen of Plasmodium falciparum related to protective immunity in the squirrel monkey.

Protective immunity against Plasmodium falciparum malaria in the squirrel monkey (Saimiri sciureus) is, in part, antibody mediated. We have previously shown that polypeptides of 41, 76, and 96 kilodaltons (kDa) are specifically immunoprecipitated with monkey sera which are protective in passive transfer experiments. We report here that three different 96-kDa polypeptides, of pI 5.15, 5.25, and 5.35, can be visualized when parasite extracts are analyzed in bidimensional gels. Only one of them (of pI 5.25) was stable after being heated at 100 degrees C for 5 min. The 96-kDa thermostable polypeptide of pI 5.25 was immunoprecipitated by protective monkey sera and by sera from adult humans living in hyperendemic areas and thus seems to be correlated with humoral protective immunity. This antigen was found in culture supernatants at the time of schizont rupture. It was synthesized during the schizont stage and is apparently not a glycoprotein.

Adult↗
PubMed1987

Human and primate malarial sera inhibit Fc receptor-mediated phagocytosis.

Sera obtained from humans in P. falciparum-endemic regions and from P. vivax-infected Saimiri sciureus were assayed for their ability to inhibit Fc receptor-mediated phagocytosis. Some sera of humans exposed to P. falciparum from The Gambia, Sudan, and Thailand inhibited ingestion via the Fc receptor by normal human monocytes. In addition, sera from infected monkeys and a high molecular weight fraction of infected monkey serum inhibited ingestion of EIgG by normal monkey spleen macrophages. Generally, inhibition was correlated with higher parasitemia and higher IFA titers.

Adolescent↗
PubMed1985

Measurement of squirrel monkey serum IgG levels by a two-site sandwich radioimmunoassay with monoclonal antibodies.

Monoclonal antibodies against the squirrel monkey Saimiri sciureus IgG have been produced for a more specific analysis of the antibody-related immunological aspects in experimental human or monkey malaria. Two monoclonal antibodies, 3D8/D5 and 3F11/G10, out of 64 reacted with distinct epitopes on the IgG present throughout the complete population without interfering with each other. The 2 monoclonal antibodies were used to develop a highly specific, reliable and sensitive two-site sandwich radioimmunoassay for the measurement of the serum IgG levels in 83 animals. The antibodies also allowed us to produce by a simple immunoabsorbent technique a highly purified IgG standard easy to calibrate and store. The assay permits the detection of IgG levels as low as 0.48 ng/ml. The standard curve is linear between 3.9 and 125 ng protein/ml and allows by a simple mathematical equation an accurate measurement of the serum IgG levels.

Animals↗
PubMed1984

Neutralization of the infectivity of sporozoites of Plasmodium knowlesi by antibodies to a synthetic peptide.

Antibodies against a synthetic peptide representing the repetitive epitope of the circumsporozoite protein (CS) of Plasmodium knowlesi have properties similar to those of antibodies against the native protein. Either antibody reacts with the synthetic peptide, cross-links the CS protein on the membrane of the parasite giving the CSP reaction, and neutralizes the infectivity of sporozoites. The synthetic peptide and sporozoite extracts were equally effective when used in an immunoradiometric assay as antigens to detect antibodies to CS proteins. It is likely that the corresponding synthetic repeats from the human malaria parasites could be used to measure levels of anti-sporozoite antibodies in endemic areas, or to evaluate the humoral response to anti-sporozoite vaccines. The authors are grateful to Dr. Robert Gwadz, NIH, for supplying Anopheles mosquitoes and P. knowlesi sporozoites used in this study.

Animals↗
PubMed1984

In vitro and in vivo studies on protective and inhibitory antibodies against Plasmodium falciparum in the Saimiri monkey.

Immunoglobulins (Ig) were purified from serum or ascitic fluids of Saimiri monkeys infected with Plasmodium falciparum and with differing levels of functional immunity. Their protective activity was assessed in studies of passive transfer of immunity in vivo, and their neutralizing activity was measured in studies of parasite inhibition in vitro in cultures of human or Saimiri RBC. Although protective and inhibitory antibodies were detected in different Ig preparations, the levels of these activities were not directly correlated. Some Ig preparations, showing high protective activity, provide little or no inhibition of the parasite in vitro. Conversely, inhibitory activity was present in Ig preparations unable to confer protection in vivo. These results indicate that protective antibodies are active through a more complex immune mechanism than simple neutralization probably involving cellular immunity.

Animals↗
PubMed1984

[Parameters for the evaluation of endurance capacity in horses].

The incremental three work loads test as a basis test, and the one work load test, in which one measures the heart rate and the serum lactic acid concentration, lead to the performance index values V4 and V150. These values are of great practical importance in judging the performance capacity, the ability to be trained, the trainings effectivity, and determining the optimal work load for interval training.

Animals↗
PubMed1983

Saimiri sciureus (karyotype 14-7): an alternative experimental model of Plasmodium falciparum infection.

In an earlier manuscript, we described the first phase of adaptation of the Palo Alto I strain of Plasmodium falciparum to Saimiri sciureus (squirrel monkeys). Now, after more than 50 P. falciparum blood transfers in splenectomized Saimiri, the parasite has become fully adapted to this experimental host. A highly reproducible pattern of infection is evident in these splenectomized animals, which is characterized by a rapidly rising parasitemia and a lethal outcome. In intact animals, the course of infection is extremely variable, with a tendency towards high parasitemias and low survival rates. After 60 passages, the parasites have maintained their invasiveness for human red blood cells and can easily be propagated by continuous in vitro culture. Conversely, prolonged in vitro culture of this parasite strain has not decreased its infectivity for Saimiri. Intact, P. falciparum-infected animals rapidly develop a high degree of resistance to reinfection, even when treatment is initiated shortly after detection of the first circulating parasites. Under identical conditions, splenectomized animals develop a variable degree of protection. The potential usefulness of squirrel monkeys as experimental hosts of P. falciparum and P. vivax malaria is discussed in light of the present findings.

Animals↗
PubMed1982

Protective antibodies against erythrocytic stages of Plasmodium falciparum in experimental infection of the squirrel monkey, Saimiri sciureus.

Serum and ascitic fluid from squirrel monkeys (Saimiri sciureus) inoculated with erythrocytic stages of Plasmodium falciparum were collected at different periods of the infection. Protection against P. falciparum was achieved by passive transfer of the sera or fluid recovered from animals after spontaneous or drug-induced cure. Purified immunoglobulins from the ascitic fluid also conferred protection. In contrast, protective antibodies directed against erythrocytic stages of P. falciparum could never be demonstrated during the acute phase of infection in spite of the high titres of malarial antibodies detected by immunofluorescence. The comparative immunochemical analysis of antigens recognized by protective and non-protective antibodies revealed quantitative differences which may be of use for the identification of antigens inducing protection.

Animals↗
PubMed1981

Ascites production in the squirrel monkey (Saimiri sciureus).

A method is described for inducing the production of large amounts of ascitic fluid (AF) in the squirrel monkey Saimiri sciureus. The total amount of protein in the induced AF is close to 60% of that in the serum. Electrophoretic analysis of serum and AF samples from the same monkey revealed similar protein patterns, including gamma globulins. Antibody titers against Plasmodium falciparum in infected monkeys, measured by indirect immunofluorescence, were also comparable in serum and AF.

Animals↗
PubMed1980

Experimental infection of the squirrel monkey (Saimiri sciureus) with Plasmodium falciparum.

Seventy-six squirrel monkeys, Saimiri sciureus, caught in Guyana and French Guiana, were examined for their susceptibility to infection with a strain of Plasmodium falciparum. Twenty-nine serial transfers were performed, both in splenectomized and intact animals. After a period of "adaptation," the strain became more virulent for the squirrel monkey and high parasitemias were obtained in splenectomized animals. Frequently, such infections led to the death of infected animals. In intact squirrel monkeys, a consistent parasitemia was observed in most animals, but with a less regular pattern and a lower level of infection. Cultivation of infected erythrocytes from squirrel monkeys and human erythrocytes confirmed that the parasite had kept its infectivity for human cells after a long period of serial syringe-transfers in the squirrel monkey, and tht the virulence for the Saimiri remained unchanged after 1-mo, in vitro progagation in human erythrocytes. All erythrocytic forms of the schizogonic cycle were observed in the bloodstream, and there was a certain synchronicity of the cycle. Gametocytes were not detected in infected animals nor in in vitro cultures derived from a parasitized squirrel monkey. Our results indicate that all the squirrel monkey can be a useful host in the laboratory for studies on P. falciparum, and it may become more important as the supply of other species of monkeys diminishes.

Animals↗