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Biomedical subjects

P Druilhe

Publications and source records attributed to P Druilhe.

At least 37 records · Page 2Linked to original sources
PubMed2000

Protection against Plasmodium falciparum malaria in chimpanzees by immunization with the conserved pre-erythrocytic liver-stage antigen 3.

In humans, sterile immunity against malaria can be consistently induced through exposure to the bites of thousands of irradiated infected mosquitoes. The same level of protection has yet to be achieved using subunit vaccines. Recent studies have indicated an essential function for intrahepatic parasites, the stage after the mosquito bite, and thus for antigens expressed during this stage. We report here the identification of liver-stage antigen 3, which is expressed both in the mosquito and liver-stage parasites. This Plasmodium falciparum 200-kilodalton protein is highly conserved, and showed promising antigenic and immunogenic properties. In chimpanzees (Pan troglodytes), the primates most closely related to humans and that share a similar susceptibility to P. falciparum liver-stage infection, immunization with LSA-3 induced protection against successive heterologous challenges with large numbers of P. falciparum sporozoites.

Animals↗
PubMed2000

Cytophilic immunoglobulin responses to Plasmodium falciparum glutamate-rich protein are correlated with protection against clinical malaria in Dielmo, Senegal.

The goal of this study was to analyze antibody responses to Plasmodium falciparum glutamate-rich protein (GLURP) using clinical data and plasma samples obtained from villagers of Dielmo, Senegal. This molecule was chosen because it is targeted by human antibodies which induce parasite growth inhibition in antibody-dependent cellular inhibition (ADCI) assays. The results showed a strong correlation between protection against malaria attacks and levels of immunoglobulin G2 (IgG2) and IgG3 against GLURP(94-489) (R0) and IgG3 against GLURP(705-1178) (R2) when corrected for the confounding effect of age-related exposure to malaria. Thus, GLURP may play a role in the induction of protective immunity against P. falciparum malaria.

Adolescent↗
PubMed1999

Convergent peptide libraries, or mixotopes, to elicit or to identify specific immune responses.

Many recent studies have demonstrated the flexibility of epitope recognition by the immune system. This can be explored using a particular type of combinatorial peptide library, termed as 'convergent', consisting essentially of closely related molecular species; from this a fuzzy set can be constructed, which comprises several variants of a peptide that would act in synchrony to represent a model antigen and its recognition by the immune system.

Amino Acid Sequence↗
PubMed1999

Irradiated sporozoites prime mice to produce high antibody titres upon viable Plasmodium berghei sporozoite challenge, which act upon liver-stage development.

C57BL6 mice were protected against Plasmodium berghei sporozoite challenge by immunization with live 12 krad dose-irradiated sporozoites, but not by 20 krad dose-irradiated sporozoites. Immunization with 12 krad irradiated sporozoites generated low levels of antibody reactive to liver-stage parasites (titres of 1/100). Inoculation of as few as 100 live P. berghei sporozoites induced complete host protection accompanied by a very quick and high boost of antibody titres up to 1/4000. This sporozoite challenge-drive antibody boost was absent in mice immunized by 20 krad sporozoites and in non-protected, and non-immunized mice. Antibody was mainly liver-stage (LS) specific and due to an increase of IgG2a and IgG2b. The in vitro effect of pre- and post-challenge sera upon either sporozoite invasion or LS development was assessed in Hep-G2 cultures. Both were found to have a strong effect upon LS development even at 1/2500 dilution, and conversely a low effect upon invasion. These results suggest that sporozoites irradiated at doses that induce protection are able to prime T-cells which, upon challenge by non-irradiated sporozoites, provide help to B-lymphocytes to trigger the production of high titres of anti-LS antibodies that can inhibit LS development in vitro.

Animals↗
PubMed1999

Human antibodies to the 19kDa C-terminal fragment of Plasmodium falciparum merozoite surface protein 1 inhibit parasite growth in vitro.

The 19kDa, C-terminal fragment of the major surface protein of Plasmodium falciparum (PfMSP1(19)) is a candidate for inclusion in a subunit malaria vaccine. In this study, we show that PfMSP1(19)-specific antibodies, affinity purified from malaria-immune human serum, can: (i) compete with invasion-inhibitory monoclonal antibodies for binding to PfMSP1(19) and (ii) mediate inhibition of parasite growth in vitro, in the absence of complement and mononuclear cells, at physiological antibody concentrations (100 micrograms/ml). Parasites expressing either the Kl or 3D7 allele of PfMSP1(19) were equally susceptible to inhibition of merozoite invasion, indicating that the target epitopes of inhibitory antibodies are conserved or cross-reactive. These studies suggest that vaccines designed to induce antibodies to PfMSP1(19) may protect against the high levels of malaria parasitaemia which are associated with clinical disease.

Adult↗
PubMed1999

Well-breeding Anopheles dirus and their role in malaria transmission in Myanmar.

Mosquitos were collected with human and animal baits from March 1996 to January 1998 in four villages located along the Yadana gas pipe line in Yepyu township, Dawae district, Tanintharyi Division, southern Myanmar. A total of 23 anopheline species were collected. Anopheles dirus were abundant in pre-monsoon (May/June) an post-monsoon (October) months. All An. dirus caught both humans and cattle were assayed with specific, sporozoite enzyme-linked immunosorbent assays (ELISAs). A total of 5/250 (2%) caught with human bait was found positive with Plasmodium vivax from Eindayaza, Ohnbinkwin and Thaechaung during rainy and cool-dry months. Larval surveys also showed An. dirus larvae/pupae were caught from domestic wells (6 to 46% found positive). Clinical surveys indicated that transmission is hyperendemic and occur all year round in all four villages.

Animals↗
PubMed1998

A primary malarial infection is composed of a very wide range of genetically diverse but related parasites.

To address the question of how many distinct parasites are injected when a mosquito bites, we have characterized isolates resulting most probably from a single sporozoite inoculum. We describe the direct and immediate cloning on hepatocyte feeder layers of a Thai and an African Plasmodium falciparum primary isolate and the characterization of 67 independent clones by four techniques totaling nine different markers. This led to three main conclusions: (a) both the phenotypic and genotypic markers revealed an unexpectedly large degree of diversity within the clones from a single isolate; (b) the clones are nonetheless genetically related; and (c) a single mosquito inoculum would most likely be sufficient to generate considerable isolate complexity in the absence of repeated exposure. This diversity, which has been greatly underestimated in previous studies, does not bode well for the development of successful malaria control means.

Africa↗
PubMed1998

Antimalarial activity of 77 phospholipid polar head analogs: close correlation between inhibition of phospholipid metabolism and in vitro Plasmodium falciparum growth.

Seventy-seven potential analogs of phospholipid polar heads, choline and ethanolamine, were evaluated in vitro as inhibitors of Plasmodium falciparum growth. Their IC50 ranged from 10(-3) to 10(-7) mol/L. Ten compounds showed similar antimalarial activity when tested against three different parasite strains (2 chloroquine-sensitive strains and 1 chloroquine-resistant strain). Compounds showing marked antimalarial activity were assayed for their effects on phospholipid metabolism. The most active compounds (IC50 of 1 to 0.03 micromol/L) were inhibitors of de novo phosphatidylcholine (PC) biosynthesis from choline. For a series of 50 compounds, there was a close correlation between impairment of phospholipid biosynthesis and inhibition of in vitro malaria parasite growth. High choline concentrations caused a marked specific shift in the curves for PC biosynthesis inhibition. Concentrations inhibiting 50% PC metabolism from choline were in close agreement with the Ki of these compounds for the choline transporter in Plasmodium knowlesi-infected erythrocytes. By contrast, measurement of the effects of 12 of these compounds on rapidly dividing lymphoblastoid cells showed a total absence of correlation between parasite growth inhibition and human lymphoblastoid cell growth inhibition. Specific antimalarial effects of choline or ethanolamine analogs are thus likely mediated by their alteration of phospholipid metabolism. This indicates that de novo PC biosynthesis from choline is a very realistic target for new malaria chemotherapy, even against pharmacoresistant strains.

Animals↗
PubMed1998

The glutamate-rich protein (GLURP) of Plasmodium falciparum is a target for antibody-dependent monocyte-mediated inhibition of parasite growth in vitro.

Monocyte-dependent as well as direct inhibitory effects of antimalarial antibodies point toward antigens accessible at the time of merozoite release as targets for biologically active antibodies capable of mediating protection against Plasmodium falciparum. The glutamate-rich protein (GLURP), being an antigen associated with mature schizont-infected erythrocytes, was therefore the object of the present investigation, in which we analyzed whether anti-GLURP antibodies can either interfere directly with merozoite invasion or act indirectly by promoting a monocyte-dependent growth inhibition, antibody-dependent cellular inhibition. GLURP-specific human immunoglobulin G (IgG) antibodies, from pooled IgG of healthy Liberian adults who were clinically immune to malaria, were purified by affinity chromatography on columns containing R0 (N-terminal nonrepetitive region of GLURP) or R2 (C-terminal repetitive region of GLURP) recombinant protein or synthetic peptides as ligands. Analysis of the pattern of reactivity of highly purified anti-GLURP antibodies led to the definition of at least four B-cell epitopes. One epitope was specific for R0, two were specific for R2, and the fourth displayed cross-reactivity between R0 and R2. None of the purified IgG antibodies had direct invasion-inhibitory effects, even at high concentrations. In contrast, when allowed to cooperate with monocytes, all anti-GLURP IgG preparations mediated a strong monocyte-dependent parasite growth inhibition in a dose-dependent manner.

Animals↗
PubMed1998

Immunogenicity of four Plasmodium falciparum preerythrocytic antigens in Aotus lemurinus monkeys.

Aotus lemurinus monkeys were immunized with pools of either lipid-tailed peptides injected in PBS or peptides in Montanide ISA-51, all derived from four Plasmodium falciparum pre-erythrocytic antigens, namely, LSA1, LSA3, SALSA, and STARP. These formulations were well tolerated. Their immunogenicity was demonstrated by the induction of both B- and T-cell responses to most of the peptides studied (of the 12, 10 induced antibody production, 9 induced T-cell proliferative responses, and all 12 induced gamma interferon secretion). Immune responses proved to be long lasting, since some were still detectable 210 days after immunization. Of particular importance is the fact that B- and T-cell responses elicited in this way by synthetic peptides were specific for native parasite proteins on P. falciparum sporozoites and liver stage parasites.

Amino Acid Sequence↗
PubMed1997

Lipopeptide immunization without adjuvant induces potent and long-lasting B, T helper, and cytotoxic T lymphocyte responses against a malaria liver stage antigen in mice and chimpanzees.

We have employed a 26-amino-acid synthetic peptide based on Plasmodium falciparum liver stage antigen-3 to evaluate improvements in immunogenicity mediated by the inclusion of a simple lipid-conjugated amino acid during peptide synthesis. Comparative immunization by the peptide in Freund's adjuvant or by the lipopeptide in saline shows that the addition of a palmitoyl chain can dramatically increase T helper (Th) cell responses in a wide range of major histocompatibility complex (MHC) class II haplotypes, to the extent that responses were induced in mice otherwise unable to respond to the non-modified peptide injected with Freund's adjuvant, and that the increased immunogenicity of the lipopeptide led to high and longer lasting antibody production (studied up to 8 months). B and T cell responses induced by the lipopeptide were reactive with native parasite protein epitopes, and a lipopeptide longer than ten amino acids was endogenously processed to associate with MHC class I and elicit cytotoxic T lymphocyte (CTL) responses. Finally, the lipopeptide was safe and highly immunogenic in chimpanzees, whose immune system is very similar to that of humans. Our results suggest that relatively large synthetic peptides, carefully chosen from pertinent areas of proteins and incorporating a simple palmitoyl-lysine, can induce not only CTL, but also strong Th and antibody responses in genetically diverse populations. Lipopeptides engineered in this way are simple to produce and purify under GMP conditions, they are well tolerated by apes, and with the enhanced immunogenicity without the need for adjuvant that we report here, they offer a quick and relatively low-cost route to provide material for human malaria vaccination trials.

Adjuvants, Immunologic↗
PubMed1997

Plasmodium falciparum sporozoite invasion is inhibited by naturally acquired or experimentally induced polyclonal antibodies to the STARP antigen.

Antibody(Ab)-mediated inhibition of sporozoite invasion of hepatocytes is a mechanism that has been clearly demonstrated to act upon Plasmodium falciparum pre-erythrocytic stages in humans. Consequently we have analyzed the Ab response to a recently identified P. falciparum sporozoite surface protein, STARP, in malaria-exposed individuals and tested the inhibitory effect of these Ab upon hepatocyte invasion in vitro. STARP-specific IgG were detected in 90 and 61% of sera from regions where individuals were exposed to 100 and 1-5 infectious bites per year, respectively. These IgG were predominantly of the cytophilic IgG1 or IgG3 type. STARP and the major sporozoite surface protein, CS, elicited equivalent IgG levels in adults. When affinity purified from either African immune sera or the serum of an individual experimentally protected by irradiated sporozoite immunization, STARP-specific Ab prevented up to 90% of sporozoites from invading human hepatocytes. The dose-dependent and reproducible inhibition was more pronounced than that observed with human CS-specific Ab affinity purified under identical conditions. Substantial reduction of sporozoite invasion was also observed with Ab induced by artificial immunization with recombinant STARP protein and reactive with the native protein. Taken together with recent findings of human cytotoxic T lymphocytes specific for this antigen, these results promote the interest of studying the efficacy of STARP as a target for immune effector mechanisms operating upon pre-erythrocytic stages.

Animals↗
PubMed1997

Asymptomatic carriers of Babesia canis in an enzootic area.

Dogs latently infected with Babesia canis were systematically detected amongst a population kept in an enzootic area over a year. Detection of parasite was carried out on 43 healthy dogs and identified by two blood cultures in an interval of a few months. A serological study was performed using indirect immunofluorescence and Western blot. This study distinguished two distinct groups: asymptomatic carrier dogs (latently infected or premunised-33%) and non-carrier dogs with sterilising immunity. There is no difference between carrier and non-carrier dogs concerning age, breed or history of babesial infection and 36 out of the 43 dogs studied are seropositive. The antibody titer did not completely correlate with the detection of parasitaemia. All carrier dogs are seropositive to Babesia canis, but half of the seropositive dogs are not carriers. This study confirms that serological detection is not a good indicator of latent babesial infection. This study did not detect any difference between antibody responses (quantitative response (IIF) or qualitative response (WB)), related to latent parasitaemia.

Animals↗