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Biomedical subjects

Pierre Druilhe

Publications and source records attributed to Pierre Druilhe.

At least 19 recordsLinked to original sources
PubMed2006

Multiplex assay for simultaneous measurement of antibodies to multiple Plasmodium falciparum antigens.

Antibodies to Plasmodium falciparum are classically measured using the enzyme-linked immunosorbent assay (ELISA). Although highly sensitive, this technique is labor-intensive when large numbers of samples must be screened against multiple antigens. The suspension array technology (SAT) might be an alterative to ELISA, as it allows measurement of antibodies against multiple antigens simultaneously with a small volume of sample. This study sought to adapt the new SAT multiplex system for measuring antibodies against nine malarial vaccine candidate antigens, including recombinant proteins from two variants of merozoite surface protein 1, two variants of apical merozoite antigen 1, erythrocyte binding antigen 175, merozoite surface protein 3, and peptides from the circumsporozoite protein, ring erythrocyte surface antigen, and liver-stage antigen 1. Various concentrations of the antigens were coupled to microspheres with different spectral addresses, and plasma samples from Cameroonian adults were screened by SAT in mono- and multiplex formats and by ELISA. Optimal amounts of protein required to perform the SAT assay were 10- to 100-fold less than that needed for ELISA. Excellent agreement was found between the single and multiplex formats (R > or = 0.96), even when two variants of the same antigen were used. The multiplex assay was rapid, reproducible, required less than 1 mul of plasma, and had a good correlation with ELISA. Thus, SAT provides an important new tool for studying the immune response to malaria rapidly and efficiently in large populations, even when the amount of plasma available is limited, e.g., in studies of neonates or finger-prick blood.

Adult↗
PubMed2006

Liver-stage development of Plasmodium falciparum, in a humanized mouse model.

BACKGROUND: The liver stage of the human malaria parasite Plasmodium falciparum is the least known, yet it holds the greatest promise for the induction of sterile immunity and the development of novel drugs. Progress has been severely limited by the lack of adequate in vitro and in vivo models. METHODS: Recently, it was found that immunodeficient mice transgenic for the urokinase plasminogen activator allow survival of differentiated human hepatocytes. We confirm this finding but show that hepatocyte survival is short lived unless nonadaptive defenses are simultaneously depleted. RESULTS: By controlling macrophages and NK cells, we readily effected the long-term secretion of human serum albumin and human alpha-1 antitrypsin in mouse serum (at 3 months, the proportion of repopulated mice increased from 0% to 60% and from 22% to 80%, respectively; P<.0001). P. falciparum sporozoites delivered intravenously into mice readily infected transplanted human hepatocytes and developed into liver schizonts. Their size was twice as large as what was seen in vitro and was comparable to that found in humans and chimpanzees. CONCLUSION: These results emphasize the importance of nonadaptive defenses against xenotransplantation and lead to development of small laboratory models that, because they can harbor human hepatocytes, provide novel opportunities to study intrahepatic pathogens, such as those causing malaria and hepatitis.

Animals↗
PubMed2006

Human recombinant antibodies against Plasmodium falciparum merozoite surface protein 3 cloned from peripheral blood leukocytes of individuals with immunity to malaria demonstrate antiparasitic properties.

Immunoglobulins from individuals with immunity to malaria have a strong antiparasitic effect when transferred to Plasmodium falciparum malaria infected patients. One prominent target of antiparasitic antibodies is the merozoite surface antigen 3 (MSP-3). We have investigated the antibody response against MSP-3 residues 194 to 257 (MSP-3(194-257)) on the molecular level. mRNA from peripheral blood leukocytes from clinically immune individuals was used as a source of Fab (fragment antibody) genes. A Fab-phage display library was made, and three distinct antibodies designated RAM1, RAM2, and RAM3 were isolated by panning. Immunoglobulin G1 (IgG1) and IgG3 full-length antibodies have been produced in CHO cells. Reactivity with the native parasite protein was demonstrated by immunofluorescence microscopy, flow cytometry, and immunoblotting. Furthermore, the antiparasitic effect of RAM1 has been tested in vitro in an antibody-dependent cellular inhibition (ADCI) assay. Both the IgG1 and the IgG3 versions of the antibody show an inhibitory effect on parasite growth.

Adult↗
PubMed2006

Antibody responses to several malaria pre-erythrocytic antigens as a marker of malaria exposure among travelers.

Protective devices against vectors are used by travelers in malaria-endemic areas but their efficacy for protection against mosquitoes has rarely been evaluated. The level of exposure to malaria transmission of 205 soldiers deployed in Africa and the efficacy of their anti-vector prophylaxis was evaluated by comparison of their IgM and IgG responses against five pre-erythrocytic Plasmodium falciparum antigens (circumsporozoite protein, sporozoite threonine- and asparagine-rich protein, sporozoite- and liver-stage antigen, liver stage antigen 1, and SR11.1) before and at the end of their deployment, and three months after returning to France for 106 of these soldiers. The immune responses increased significantly during the mission in 35% (95% confidence interval = 28-42%) of the individuals. The permanent use of insecticide-treated bed nets and long-sleeve battle dress at night were associated with protective efficacy. The analysis of these antibody responses was sensitive enough to evaluate exposure to malaria transmission and the efficacy of anti-vector devices in travelers using antimalarial chemoprophylaxis.

Adolescent↗
PubMed2005

A malaria vaccine that elicits in humans antibodies able to kill Plasmodium falciparum.

BACKGROUND: Plasmodium falciparum merozoite surface protein 3 is a malaria vaccine candidate that was identified, characterised, and developed based on a unique immuno-clinical approach. The vaccine construct was derived from regions fully conserved among various strains and containing B cell epitopes targeted by human antibodies (from malaria-immune adults) that are able to mediate a monocyte-dependent parasite killing effect. The corresponding long synthetic peptide was administered to 36 volunteers, with either alum or Montanide ISA720 as adjuvant. METHODS AND FINDINGS: Both formulations induced cellular and humoral immune responses. With alum, the responses lasted up to 12 mo. The vaccine-induced antibodies were predominantly of cytophilic classes, i.e., able to cooperate with effector cells. In vitro, the antibodies induced an inhibition of the P. falciparum erythrocytic growth in a monocyte-dependent manner, which was in most instances as high as or greater than that induced by natural antibodies from immune African adults. In vivo transfer of the volunteers' sera into P. falciparum-infected humanized SCID mice profoundly reduced or abrogated parasitaemia. These inhibitory effects were related to the antibody reactivity with the parasite native protein, which was seen in 60% of the volunteers, and remained in samples taken 12 mo postimmunisation. CONCLUSION: This is the first malaria vaccine clinical trial to clearly demonstrate antiparasitic activity by vaccine-induced antibodies by both in vitro and in vivo methods. The results, showing the induction of long-lasting antibodies directed to a fully conserved polypeptide, also challenge current concepts about malaria vaccines, such as unavoidable polymorphism, low antigenicity, and poor induction of immune memory.

Adjuvants, Immunologic↗
PubMed2005

Insights into the P. y. yoelii hepatic stage transcriptome reveal complex transcriptional patterns.

During their complex life cycle, malaria parasites adopt morphologically, biochemically and immunologically distinct forms. The intra-hepatic form is the least known, yet of established value in the induction of sterile immunity and as a target for chemoprophylaxis. Using Plasmodium yoelii as a model we present here a novel approach to the elucidation of the transcriptome of this poorly studied stage. Sequences from Plasmodium were obtained in 388 of the 3533 inserts (11%) isolated from liver stages cDNA obtained from optimized cultures with high yields. These corresponded to a total of 88 putative P. yoelii genes. The majority of the transcribed genes identified, code for predicted proteins of as yet unknown function. The RT-PCR analysis carried out for 29 of these genes, confirmed expression at the hepatic stage and provided evidence for complex patterns of genes transcription in the distinct stages found in the mosquito and vertebrate host. The results demonstrate the efficacy of the approach that can now be applied to further detailed analysis of the hepatic stage transcriptome of Plasmodium.

Animals↗
PubMed2005

Worms can worsen malaria: towards a new means to roll back malaria?

Recent studies in Africa and Asia indicate that different helminthic infections adversely affect the clinical outcome of malaria infections. This suggests that helminths can influence the acquisition of immunity against Plasmodium. Worms could constitute a confounding factor in the assessment of efficacy of malaria-control intervention, including vaccine prototypes in clinical trials. These observations have fundamental and practical consequences; if the deleterious effect of worms on malaria is confirmed, treatment of helminths would offer an affordable, strongly effective and novel means to roll back malaria. With this article, we hope to induce others to conduct similar studies in different regions.

Animals↗
PubMed2005

Immunization of Saimiri sciureus monkeys with a recombinant hybrid protein derived from the Plasmodium falciparum antigen glutamate-rich protein and merozoite surface protein 3 can induce partial protection with Freund and Montanide ISA720 adjuvants.

The immunogenicity and efficacy of a hybrid recombinant protein derived from the N-terminal end of the glutamate-rich protein (GLURP) and the C-terminal portion of the merozoite surface protein 3 (MSP3) of Plasmodium falciparum was evaluated in Saimiri sciureus monkeys. The GLURP/MSP3 hybrid protein, expressed in Lactococcus lactis, was administered in association with alum, Montanide ISA720, or complete or incomplete Freund adjuvant (CFA/IFA) in groups of five animals each. The three formulations were shown to be immunogenic, but the one with alum was shown to be weak compared to the other two, particularly CFA/IFA, which provided very high antibody titers (enzyme-linked immunosorbent assay titers of >3,000,000 and immunofluorescence antibody test titers of 6,400). After a challenge infection with P. falciparum FUP strain, all five monkeys from the GLURP/MSP3-alum group showed a rapid increase in parasitemia, reaching 10% and were treated early. The two monkeys with the highest antibody titers in group GLURP/MSP3-Montanide ISA720 had a delay in the course of parasitemia and were treated late due to a low hematocrit. In the GLURP/MSP3-CFA/IFA group, parasitemia remained below this threshold in four of the five animals and, after it reached a peak, parasitemia started to decrease and monkeys were treated late. When all animals were grouped according to the outcome, a statistically significant association between high antibody titers and partial protection was observed. The challenge infection boosted the antibody titers, and the importance of this event for vaccine efficacy in areas where this parasite is endemic is discussed. In conclusion, these data suggest that GLURP and MSP3 can induce protection against malaria infection if antibodies are induced at properly high titers.

Animals↗
PubMed2005

Phase I malaria vaccine trial with a long synthetic peptide derived from the merozoite surface protein 3 antigen.

The C-terminal conserved region of Plasmodium falciparum merozoite surface protein 3 (MSP3) is the trigger antigen of a protective immune response mediated by cytophilic antibodies. In an open, randomized, two-adjuvant (Montanide ISA 720, aluminum hydroxide) phase I clinical trial we evaluated the safety and immunogenicity of increasing doses of a long synthetic peptide construct spanning the conserved region of MSP3 targeted by biologically active antibodies (MSP3-LSP). Thirty-five healthy volunteers were randomized to receive three subcutaneous injections on days 0, 30, and 120. Of the 100 injections given, 10 caused severe local reactions, 62 caused transient mild to moderate local reactions, and 28 caused no reaction. On the basis of preestablished exclusion criteria, use of the Montanide formulation led to withdrawal of five volunteers after the second injection. This led to a reduction in the subsequent vaccine doses in four of the groups. No vaccine-related serious adverse events occurred throughout the trial. After the third injection, volunteers displayed a marked specific anti-MSP3-LSP antibody response (23/30 individuals, compared with 29/34 individuals for plasma from an area where malaria is endemic), an anti-native MSP3 antibody response (19/30 individuals), a T-cell-antigen-specific proliferative response (26/30 individuals), and gamma interferon production (25/30 individuals). In conclusion, the MSP3-LSP vaccine was immunogenic with both adjuvants, although it was unacceptably reactogenic when it was combined with Montanide. The potential usefulness of the candidate vaccine is supported by the induction of a strong cytophilic response (i.e., the type of anti-MSP3 antibodies involved in antibody-dependent, monocyte-mediated protective mechanisms in areas where malaria is endemic).

Adult↗
PubMed2005

Plasmodium falciparum merozoite surface protein 6 displays multiple targets for naturally occurring antibodies that mediate monocyte-dependent parasite killing.

Plasmodium falciparum MSP6 is a merozoite surface antigen that shows organization and sequence homologies similar to those of MSP3. Within its C-terminus conserved region, it presents some epitopes that are cross-reactive with MSP3 and others that are not, both being targets of naturally occurring antibodies that block the P. falciparum erythrocytic cycle in cooperation with monocytes.

Amino Acid Sequence↗
PubMed2004

Increase of malaria attacks among children presenting concomitant infection by Schistosoma mansoni in Senegal.

Helminthic infections concomitant with malaria are common in inter-tropical areas. A recent study showed that mice co-infected with Schistosoma mansoni and Plasmodium chabaudi develop higher P. chabaudi parasitaemia and had a higher mortality rate. This important observation deserved to be further investigated among human populations.Malaria attacks were recorded in 512 children aged 6-15 years living in Richard Toll (Northern Senegal) among whom 336 were infected by S. mansoni, and 175 were not. The incidence rate of malaria attacks was significantly higher among S. mansoni-infected individuals, particularly those carrying the highest worm loads, as compared to uninfected subjects (26.6% versus 16,4 %). In contrast, the rate of malaria attacks was lower, without reaching significance, in medium grade S. mansoni infections. Thus, infection by S. mansoni affects susceptibility to malaria, but this can vary according to the intensity of parasite load. The immunological mechanisms underlying this dual effect need to be further explored.

Adolescent↗
PubMed2004

Identification of a conserved region of Plasmodium falciparum MSP3 targeted by biologically active antibodies to improve vaccine design.

Merozoite surface protein 3 (MSP3) is a target of antibody-dependent cellular inhibition (ADCI), a protective mechanism against Plasmodium falciparum malaria. From the C-terminal half of the molecule, 6 overlapping peptides were chosen to characterize human immune responses. Each peptide defined at least 1 non-cross-reactive B cell epitope. Distinct patterns of antibody responses, by level and IgG subclass distribution, were observed in inhabitants of a malaria-endemic area. Antibodies affinity purified toward each peptide differed in their functional capacity to mediate parasite killing in ADCI assays: 3 of 6 overlapping peptides had a major inhibitory effect on parasite growth. This result was confirmed by the passive transfer of anti-MSP3 antibodies in vivo in a P. falciparum mouse model. T helper cell epitopes were identified in each peptide. Antigenicity and functional assays identified a 70-amino acid conserved domain of MSP3 as a target of biologically active antibodies to be included in future vaccine constructs based on MSP3.

Animals↗
PubMed2004

A Plasmodium falciparum GLURP-MSP3 chimeric protein; expression in Lactococcus lactis, immunogenicity and induction of biologically active antibodies.

Plasmodium falciparum malaria is a major cause of morbidity and mortality worldwide. To evaluate the efficacy of a possible vaccine antigen against P. falciparum infection, a fusion protein, derived from P. falciparum Glutamate-rich protein (GLURP) genetically coupled to P. falciparum Merozoite surface protein 3 (MSP3) was produced in Lactococcus lactis as a secreted recombinant GLURP-MSP3 fusion protein. The hybrid protein was purified to homogeneity by ion exchange and hydrophobic-interaction chromatography and its composition was verified by MALDI MS, SDS/PAGE and Western blotting with antibodies against antigenic components of GLURP and MSP3. Mice immunized with the hybrid protein produced higher levels of both GLURP- and MSP3-specific antibodies than mice immunized with either GLURP, MSP3 or a mix of both. The protective potential of the hybrid protein was also demonstrated by in vitro parasite-growth inhibition of mouse anti-GLURP-MSP3 IgG antibodies in a monocyte-dependent manner. These results indicate that the GLURP-MSP3 hybrid could be a valuable strategy for future P. falciparum vaccine development.

Animals↗
PubMed2004

Association between protection against clinical malaria and antibodies to merozoite surface antigens in an area of hyperendemicity in Myanmar: complementarity between responses to merozoite surface protein 3 and the 220-kilodalton glutamate-rich protein.

We performed a longitudinal clinical and parasitological follow-up study in OoDo, a village in southeast Asia in which malaria is hyperendemic, in order to assess the association between protection against malaria attacks and antibodies to three currently evaluated vaccine candidates, merozoite surface protein 1 (MSP1), MSP3, and the 220-kDa glutamate-rich protein (GLURP) from Plasmodium falciparum. Our results showed that the levels of cytophilic immunoglobulin G3 (IgG3) antibodies against conserved regions of MSP3 and GLURP were significantly correlated with protection against clinical P. falciparum malaria. In contrast, the levels of noncytophilic IgG4 antibodies against GLURP increased with the number of malaria attacks. Furthermore, we observed a complementary effect of the MSP3- and GLURP-specific IgG3 antibodies in relation to malaria protection. In the individuals that did not respond to one of the antigens, a strong response to the other antigen was consistently detected and was associated with protection, suggesting that induction of antibodies against both MSP3 and GLURP could be important for the development of protective immunity. The complementarity of the responses to the two main targets of antibody-dependent cellular inhibition identified to date provides the first rational basis for combining these two antigens in a hybrid vaccine formulation.

Adolescent↗
PubMed2004

Long-term multiepitopic cytotoxic-T-lymphocyte responses induced in chimpanzees by combinations of Plasmodium falciparum liver-stage peptides and lipopeptides.

Preclinical immunogenicity studies of 12 malaria peptides, selected from four Plasmodium falciparum antigens (Ags), namely, LSA1, LSA3, SALSA, and STARP, that are expressed at the pre-erythrocytic (sporozoite and liver) stages of the human parasite were carried out in chimpanzees. To strengthen their immunogenicity, six of these synthetic peptides were modified by the C-terminal addition of a single palmitoyl chain (lipopeptides) and delivered without adjuvant, whereas the remaining six unmodified peptides were emulsified and delivered by using Montanide ISA51 adjuvant. We have previously reported that these peptides and lipopeptides induce high B-cell and CD4(+)-T-helper responses in chimpanzees. In this report, we show their ability to induce multiepitopic and long-lasting antigen-specific CD8(+) cytotoxic-T-lymphocyte (CTL) responses. The magnitude, consistency, and memory of CTL responses generated by LSA3 peptides point to the strong immunogenicity of this liver-stage Ag. These findings support the screening strategy used to select the four P. falciparum pre-erythrocytic Ags and emphasize their valuable immunogenic properties. The successful immunization of nonhuman primates with combinations of corresponding peptides in a mineral oil emulsion (ISA51) and lipopeptides in saline provide a vaccine formulation that can be tested in humans.

Amino Acid Sequence↗
PubMed2004

Short report: High prevalence of multidrug-resistant Plasmodium falciparum malaria in the French territory of Mayotte.

A drug-resistance survey was conducted in the French territory of Mayotte in the Comorian Islands in the Indian Ocean where malaria is endemic. A high prevalence of resistant Plasmodium falciparum parasites was observed, not only to chloroquine (88%) and pyrimethamine (99%), but more surprisingly to quinine (17%), mefloquine (9%), and amodiaquine (24%). This leaves few treatment alternatives other than artemisine-mefloquine combinations. However, despite notification to French Health authorities three years ago, inadequate treatment (chloroquine plus sulfadoxine-pyrimethamine) is still used in this locality. Thus, people still die of malaria in this remote territory of France.

Animals↗
PubMed2004

Update on the clinical development of candidate malaria vaccines.

The recent availability of significantly increased levels of funding for unmet medical needs in the developing world, made available by newly created public-private-partnerships, has proven to be a powerful driver for stimulating clinical development of candidate vaccines for malaria. This new way forward promises to greatly increase the likelihood of bringing a safe and effective vaccine to licensure. The investigators bring together important published and unpublished information that illuminates the status of malaria vaccine development. They focus their comments on those candidate vaccines that are currently in or expected to enter clinical trials in the next 12 months.

Clinical Trials as Topic↗