Biomedical subjects

L Vigneron

Publications and source records attributed to L Vigneron.

7 recordsLinked to original sources

PubMed2001

Efficacy of RTS,S/AS02 malaria vaccine against Plasmodium falciparum infection in semi-immune adult men in The Gambia: a randomised trial.

BACKGROUND: RTS,S/AS02 is a pre-erythrocytic malaria vaccine based on the circumsporozoite surface protein of Plasmodium falciparum fused to HBsAg, incorporating a new adjuvant (AS02). We did a randomised trial of the efficacy of RTS,S/AS02 against natural P. falciparum infection in semi-immune adult men in The Gambia. METHODS: 306 men aged 18-45 years were randomly assigned three doses of either RTS,S/AS02 or rabies vaccine (control). Volunteers were given sulfadoxine/pyrimethamine 2 weeks before dose 3, and kept under surveillance throughout the malaria transmission season. Blood smears were collected once a week and whenever a volunteer developed symptoms compatible with malaria. The primary endpoint was time to first infection with P. falciparum. Analysis was per protocol. FINDINGS: 250 men (131 in the RTS,S/AS02 group and 119 in the control group) received three doses of vaccine and were followed up for 15 weeks. RTS,S/AS02 was safe and well tolerated. P. falciparum infections occurred significantly earlier in the control group than the RTS,S/AS02 group (Wilcoxon's test p=0.018). Vaccine efficacy, adjusted for confounders, was 34% (95% CI 8.0-53, p=0.014). Protection seemed to wane: estimated efficacy during the first 9 weeks of follow-up was 71% (46-85), but decreased to 0% (-52 to 34) in the last 6 weeks. Vaccination induced strong antibody responses to circumsporozoite protein and strong T-cell responses. Protection was not limited to the NF54 parasite genotype from which the vaccine was derived. 158 men received a fourth dose the next year and were followed up for 9 weeks; during this time, vaccine efficacy was 47% (4-71, p=0.037). INTERPRETATION: RTS,S/AS02 is safe, immunogenic, and is the first pre-erythrocytic vaccine to show significant protection against natural P. falciparum infection.

Adult↗

PubMed1999

A phase I safety and immunogenicity trial with the candidate malaria vaccine RTS,S/SBAS2 in semi-immune adults in The Gambia.

RTS,S is a novel pre-erythrocytic malaria vaccine based on the circumsporozoite surface protein (CSP) of Plasmodium falciparum linked to hepatitis B surface antigen (HBs) and combined with a novel adjuvant system (SBAS2). We have conducted a Phase I trial with three doses of this vaccine given at 0, 1, and 6 months to 20 semi-immune, adult, male volunteers in The Gambia to assess its safety and immunogenicity. Eighteen of the 20 volunteers completed the study. There were no clinically significant local or systemic adverse events following each vaccination. Hematologic and biochemical indices before and two weeks after each vaccination showed no evidence of toxicity. Antibody titers to both CSP and HBs showed a significant increase after vaccination; these were the largest after the third dose. We conclude that the RTS,S/SBAS2 vaccine induces no significant toxicity in this semi-immune population and produces significant increases in antibody titers to CSP.

Adolescent↗

PubMed1995

Fourier transform infrared spectroscopy study of the secondary structure of the reconstituted Neurospora crassa plasma membrane H(+)-ATPase and of its membrane-associated proteolytic peptides.

We reconstituted purified plasma membrane H(+)-ATPase from Neurospora crassa into soybean phospholipid vesicles (lipid/ATPase ratio of 5:1 w/w). The proteoliposomes contained an active ATPase, oriented inside-out. They were subjected to proteolysis by using Pronase, proteinase K, trypsin, and carboxypeptidase Y. Fourier transform infrared attenuated total reflection spectroscopy indicates that the amount of protein remaining after hydrolysis and elimination of the extramembrane domain of ATPase represents about 43% of the intact protein. The secondary structure of intact ATPase and of the membrane-associated domain of ATPase was determined by infrared spectroscopy. The membrane domain shows a typical alpha-helix and beta-sheet absorption. Polarized infrared spectroscopy reveals that the orientation of the helices is about perpendicular to the membrane. Amide hydrogen/deuterium exchange kinetics performed for the intact H(+)-ATPase and for the membrane-associated domain demonstrate that this part of ATPase shows less accessibility to the solvent than the entire protein but remains much more accessible to the solvent than bacteriorhodopsin membrane segments.

Bacteriorhodopsins↗

PubMed1995

Reconstitution of the Neurospora crassa plasma membrane H(+)-adenosine triphosphatase.

The purified H(+)-ATPase of the Neurospora crassa plasma membrane has been reconstituted by a gel filtration method into lipidic vesicles using sodium deoxycholate as the detergent. Reconstitution was performed for lipid/ATPase ratios ranging from 1000:1 to 5:1 (w/w). Whatever the lipid/ATPase ratio, the ATPase molecules completely associate with the lipid vesicles. The ATPase specific activity is identical for all proteoliposomes regardless of the lipid/ATPase ratio, but the H+ transport decreases at high protein/lipid ratios, suggesting that the proteoliposomes are more leaky to H+ as the amount of protein inserted into the lipidic membrane increases. Analysis of the fragments generated by trypsin proteolysis in the presence and in the absence of MgATP+ vanadate indicate that most of the reconstituted ATPase molecules are able to assume the transition state of the enzyme dephosphorylation reaction, and are therefore functional. The orientation (inside-out or rightside-out) of the ATPase molecules in the vesicles is independent of the lipid/ATPase ratio chosen for the reconstitution. For all the lipid/ATPase ratios tested, most of the ATPase molecules (> 99%) expose their cytoplasmic side to the outside of the reconstituted proteoliposomes. The size of the vesicles increases parallel to the ATPase amount. Although the H+ leakiness of our preparation at low lipid/protein ratios prevents proton pumping measurements, the reconstitution procedure described here has the main advantage on other procedures to allow the obtention of vesicles at high protein-to-lipid ratios, facilitating further structural characterization of the ATPase by biochemical and biophysical techniques. Therefore, the procedure described here could be of general interest in the field of membrane protein study.

Cell Membrane↗

PubMed1994

Tertiary conformational changes of the Neurospora crassa plasma membrane H(+)-ATPase monitored by hydrogen/deuterium exchange kinetics. A Fourier transformed infrared spectroscopy approach.

Attenuated total reflection Fourier transform infrared spectroscopy of hydrated films of the Neurospora crassa plasma membrane H(+)-ATPase has been used to monitor the alpha-helix and beta-sheet contents and amide hydrogen exchange rates of the enzyme in the absence of ligands or locked in several stages of the enzyme catalytic cycle by MgADP, Mg-vanadate, and MgATP-vanadate. No difference larger than 2% was found in the alpha-helix or beta-sheet content of the H(+)-ATPase in different conformational states. However, when the rate of hydrogen/deuterium exchange monitored by the evolution of the area of amide II and amide II' is decomposed into three components, the number of amide protons characterized by a short exchange rate (1.1 min) falls from 38% of the protein amide protons (or 37% in the presence of Mg2+ alone) to 24-27% in the presence of Mg-vanadate and MgATP-vanadate and to 19% in the presence of MgADP. These results suggest that the conformational changes known to occur when the H(+)-ATPase interacts with the above ligands are predominantly tertiary structure changes.

Adenine Nucleotides↗

PubMed1991

Secondary structure of the membrane-bound form of the pore-forming domain of colicin A. An attenuated total-reflection polarized Fourier-transform infrared spectroscopy study.

The structure of the pore-forming domain of the bacterial toxin colicin A was studied by attenuated total-reflection polarized Fourier-transform infrared spectroscopy. This channel-forming fragment interacts with dimyristoylglycerophosphoglycerol (Myr2GroPGro) vesicles and forms disk-like complexes. Analysis of the shape of the amide I' band indicates that its secondary structure is not affected by the pH 5.0-7.2. However, 5-10% of the peptide amino acids adopt an alpha-helical structure upon complex formation with Myr2GroPGro, while the random-coil and beta-sheet structure contents decrease. Interestingly, the increase in alpha-helical content is essentially due to an increase in the high-frequency component of the alpha-helical domain of amide I'. The fact that only this component was 90 degrees polarized (i.e. the helix is parallel to the acyl chain) suggests that only this particular type of helix is associated with the Myr2GroPGro bilayer.

Colicins↗

PubMed1991

Differences in primary structure among five phospholipases A2 from Heloderma suspectum.

Five increasingly anionic phospholipases A2 (Pa1-Pa5) exist in the venom of the lizard Heloderma suspectum. We recently elucidated the sequence of Pa5, the most abundant and most active variant, towards emulsified phosphatidylcholines. Here we present the primary structures of Pa2, Pa3 (subvariants a and b) and Pa4, based on Edman degradation of tryptic, endoproteinase Arg-C and chymotryptic fragments of the reduced and S-carboxymethylated proteins. Pa1-Pa5, considered collectively, belong to an original class of secretory phospholipases A2 with 141-143 residues, a short hydrophobic N-terminus, 10 half-cystine residues and an extended C-terminus. The only known phospholipase A2 with characteristics close enough to be a member of the same class is that present in the venom from the insect Apis mellifera. More specifically, the sequences of Pa3 and Pa5 are almost identical, and those of Pa2 and Pa4 are also quite similar. Both groups diverge enough to indicate the translation of two mRNA species in the venom gland. The primary structure of Pa3 reveals the existence of subvariants a and b, the sequence of which is identical to that previously defined for Pa5, except that the C-terminal tripeptide GEG in Pa5 is replaced by the dipeptide GE in Pa3a and the tetrapeptide GEGR in Pa3b, Pa4, when compared to Pa5, shows 21 substitutions with a cluster of five modified amino acids in positions 40-44, immediately after the catalytic segment amino acids 30-39, and added changes scattered before the C-terminus. Pa2 differs from Pa4 only by the absence of the Gly142 C-terminal residue. The 15% difference in primary structure observed between the Pa3-Pa5 and Pa2-Pa4 subgroups might be largely responsible for their distinct biological properties.

Amino Acid Sequence↗