MSight: an image analysis software for liquid chromatography-mass spectrometry.

Images obtained from high-throughput mass spectrometry (MS) contain information that remains hidden when looking at a single spectrum at a time. Image processing of liquid chromatography-MS datasets can be extremely useful for quality control, experimental monitoring and knowledge extraction. The importance of imaging in differential analysis of proteomic experiments has already been established through two-dimensional gels and can now be foreseen with MS images. We present MSight, a new software designed to construct and manipulate MS images, as well as to facilitate their analysis and comparison.

Modern immunological approaches to assess malaria transmission and immunity and to diagnose plasmodial infection

The present paper reviews our recent data concerning the use of immunological methods employing monoclonal antibodies and synthetic peptides to study malaria transmission and immunity and to diagnose plasmodial infection. As concerns malaria transmission, we studied the main vectors of human malaria and the plasmodial species transmitted in endemic areas of Rondônia state, Brazil. The natural infection on anopheline was evaluated by immunoradiometric assay (IRMA) using monoclonal antibodies to an immunodominant sporozoite surface antigen (CS protein) demonstrated to be species specific. Our results showed that among six species of Anopheles found infected, An. darlingi was the main vector transmitting Plasmodium falciparum and P. vivax malaria in the immediate vicinity of houses. In order to assess the level of anti-CS antibodies we studied, by IRMA using the synthetic peptide corresponding to the repetitive epitope of the sporozoite CS protein, sera of individuals living in the same areas where the entomological survey has been performed. In this assay the prevalence of anti-CS antibodies was very low and did not reflect the malaria transmission rate in the studied areas. In relation to malaria diagnosis, a monoclonal antibody specific to an epitope of a 50 kDa exoantigen, the major component of supernatant collected at the time of schizont rupture, was used as a probe for the detection of P. falciparum antigens. This assay seemed to be more sensitive than parasitological examination for malaria diagnosis since it was able to detect plasmodial antigens in both symptomatic and asymtomatic individuals with negative thick blood smear at different intervals after a last parasitologically confirmed confirmed attack of malaria.

Evidence for multiple B- and T-cell epitopes in Plasmodium falciparum liver-stage antigen 3.

Liver-stage antigen 3 (LSA-3) is a new vaccine candidate that can induce protection against Plasmodium falciparum sporozoite challenge. Using a series of long synthetic peptides (LSP) encompassing most of the 210-kDa LSA-3 protein, a study of the antigenicity of this protein was carried out in 203 inhabitants from the villages of Dielmo (n = 143) and Ndiop (n = 60) in Senegal (the level of malaria transmission differs in these two villages). Lymphocyte responses to each individual LSA-3 peptide were recorded, some at high prevalences (up to 43%). Antibodies were also detected to each of the 20 peptides, many at high prevalence (up to 84% of responders), and were directed to both nonrepeat and repeat regions. Immune responses to LSA-3 were detectable even in individuals of less than 5 years of age and increased with age and hence exposure to malaria, although they were not directly related to the level of malaria transmission. Thus, several valuable T- and B-cell epitopes were characterized all along the LSA-3 protein, supporting the antigenicity of this P. falciparum vaccine candidate. Finally, antibodies specific for peptide LSP10 located in a nonrepeat region of LSA-3 were found significantly associated with a lower risk of malaria attack over 1 year of daily clinical follow-up in children between the ages of 7 and 15 years, but not in older individuals.

Altered expression of CD44 and DKK1 in the progression of Barrett's esophagus to esophageal adenocarcinoma.

Barrett's esophagus (BE) is an acquired condition in which the normal lining of the esophagus is replaced by intestinal metaplastic epithelium. BE can evolve to esophageal adenocarcinoma (EAC) through low-grade dysplasia (LGD) and high-grade dysplasia (HGD). The only generally accepted marker for increased risk of EAC is the presence of HGD, diagnosed on endoscopic biopsies. More specific markers for the prediction of EAC risk are needed. A tissue microarray was constructed comprising tissue samples from BE, LGD, HGD, and EAC. Marker expression was studied by immunohistochemistry using antibodies against CD44, DKK1, CDX2, COX2, SOX9, OCT1, E-cadherin, and beta-catenin. Immunostaining was evaluated semi-quantitatively. CD44 expression decreased in HGD and EAC relative to BE and LGD. DKK1 expression increased in HGD and EAC relative to BE and LDG. CDX2 expression increased in HGD but decreased in EAC. COX2 expression decreased in EAC, and SOX9 expression increased only in the upper crypt epithelial cells in HGD. E-cadherin expression decreased in EAC. Nuclear beta-catenin was not significantly different between BE, LGD, and HGD. Loss of CD44 and gain of DKK1 expression characterizes progression from BE and LGD to HGD and EAC, and their altered expression might indicate an increased risk for developing an EAC. This observation warrants inclusion of these immunohistochemically detectable markers in a study with a long patient follow-up.

The antibody response in mice to carrier-free synthetic polymers of Plasmodium falciparum circumsporozoite repetitive epitope is I-Ab-restricted: possible implications for malaria vaccines.

The immunogenicity of a novel synthetic peptide consisting of an average of 40 (Asn-Ala-Asn-Pro) repeats of the circumsporozoite protein of Plasmodium falciparum, (NANP)40, was studied in mice without using any carrier proteins. First, high titers of anti-(NANP)40 antibodies could be obtained after immunization of C57BL/6 mice. These antibodies also reacted with an extract of mosquitoes infected with P. falciparum sporozoites. C57BL/6 nu/nu mice did not produce antibodies against (NANP)40. Secondly, when 14 strains of mice with nine different H-2 haplotypes were immunized with (NANP)40 without carrier, only H-2b mice were found to produce anti-(NANP)40 antibodies, whereas all non-H-2b mice were consistently unresponsive. This response was demonstrated to be I-A-linked by using recombinant and mutant mice. I-Ab [B10.A(5R)] mice produced anti-(NANP)40 antibodies as well as H-2b inbred mice. B6CH-2bm12 I-Ab-mutant mice showed only a very low response. Third, the antibody response against (NANP)40 could be induced in nonresponder mice by immunization with the peptide coupled to a carrier protein. In view of the existence of such an exceptional H-2b restriction in the response to sporozoite synthetic peptides in mice, the triggering of peptide-specific T cell responses in humans receiving sporozoite malaria vaccines might be difficult to achieve.

Amino acid identity and/or position determines the proteasomal cleavage of the HLA-A*0201-restricted peptide tumor antigen MAGE-3271-279.

The proteasome plays a crucial role in the proteolytic processing of antigens presented to T cells in the context of major histocompatibility complex class I molecules. However, the rules governing the specificity of cleavage sites are still largely unknown. We have previously shown that a cytolytic T lymphocyte-defined antigenic peptide derived from the MAGE-3 tumor-associated antigen (MAGE-3(271-279), FLWGPRALV in one-letter code) is not presented at the surface of melanoma cell lines expressing the MAGE-3 protein. By using purified proteasome and MAGE-3(271-279) peptides extended at the C terminus by 6 amino acids, we identified predominant cleavages after residues 278 and 280 but no detectable cleavage after residue Val(279), the C terminus of the antigenic peptide. In the present study, we have investigated the influence of Pro(275), Leu(278), and Glu(280) on the proteasomal digestion of MAGE-3(271-285) substituted at these positions. We show that positions 278 and 280 are major proteasomal cleavage sites because they tolerate most amino acid substitutions. In contrast, the peptide bond after Val(279) is a minor cleavage site, influenced by both distal and proximal amino acid residues.

A novel merozoite surface antigen of Plasmodium falciparum (MSP-3) identified by cellular-antibody cooperative mechanism antigenicity and biological activity of antibodies

We report the identification of a 48kDa antigen targeted by antibodies which inhibit Plasmodium falciparum in vitro growth by cooperation with blood monocytes in an ADCI assay correlated to the naturally acquired protection. This protein is located on the surface of the merozoite stage of P. falciparum, and is detectable in all isolates tested. Epidemiological studies demonstrated that peptides derived from the amino acid sequence of MSP-3 contain potent B and T-cell epitopes recognized by a majority of individuals living in endemic areas. Moreover human antibodies either purified on the recombinant protein, or on the synthetic peptide MSP-3b, as well as antibodies raised in mice, were all found to promote parasite killing mediated by monocytes.

CD8+ T-cell response to NY-ESO-1: relative antigenicity and in vitro immunogenicity of natural and analogue sequences.

We have shown previously that HLA-A*0201 melanoma patients can frequently develop a CTL response to the cancer testis antigen NY-ESO-1. In the present study, we have analyzed in detail the relative antigenicity and in vitro immunogenicity of natural and modified NY-ESO-1 peptide sequences. The results of this analysis revealed that, although suboptimal for binding to the HLA-A*0201 molecule, peptide NY-ESO-1 157-165 is, among natural sequences, very efficiently recognized by specific CTL clones derived from three melanoma patients. In contrast, peptides NY-ESO-1 157-167 and NY-ESO-1 155-163, which bind very strongly to HLA-A*0201, are recognized less efficiently. In agreement with previous data, substitution of peptide NY-ESO-1 157-165 COOH-terminal C with various other amino acids resulted in a significantly increased binding to HLA-A*0201 molecules as well as in an increased CTL recognition, although variable at the clonal level. Among natural peptides, NY-ESO-1 157-165 and NY-ESO-1 157-167 exhibited good in vitro immunogenicity, whereas peptide NY-ESO-1 155-163 was poorly immunogenic. The fine specificity of interaction between peptide NY-ESO-1 C165A, HLA-A*0201, and T-cell receptor was analyzed at the molecular level using a series of variant peptides containing single alanine substitutions. The findings reported here have significant implications for the formulation of NY-ESO-1-based vaccines as well as for the monitoring of either natural or vaccine-induced NY-ESO-1-specific CTL responses in cancer patients.

Development of a vaccine strategy against human and bovine schistosomiasis: background and update

Schistosomiasis is a chronic and debilitating parasitic disease that affects over 200 million people throughout the world and causes about 500,000 deaths annually. Two specific characteristics of schistosome infection are of primordial importance to the development of a vaccine: schistosomes do not multiply within the tissues of their definitive hosts (unlike protozoan parasites) and a partial non-sterilizing immunity can have a marked effect on the incidence of pathology and on disease transmission. Since viable eggs are the cause of disease pathology, a reduction in worm fecundity whether or not accompanied by a reduction in parasite burden is a sufficient goal for vaccine induced immunity. We originally showed that IgE antibodies played in experimental models a pivotal role for the development of protective immunity. These laboratory findings have been now confirmed in human populations. Following the molecular cloning and expression of a protein 28 kDa protein of Schistosoma mansoni and its identification as a glutathion S-transferase, immunization experiments have been undertaken in several animal species (rats, mice, baboons). Together with a significant reduction in parasite burden, vaccination with Sm28 GST was recently shown to reduce significantly parasite fecundity and egg viability leading to a decrease in liver pathology. Whereas IgE antibodies were shown to be correlated with protection against infection, IgA antibodies have been identified as one of the factors affecting egg laying and viability. In human populations, a close association was found between IgA antibody production to Sm28 GST and the decrease of egg output. The use of appropriate monoclonal antibody probes has allowed the demonstration that the inhibition of parasite fecundity following immunization was related to the inhibition of enzymatic activity of the molecule. Epitope mapping of Sm28 GST has indicated the prominent role of the N and C terminal domains. Immunization with the corresponding synthetic peptides was followed by a decrease of 70% of parasite fecundity and egg viability. As a preliminary step towards phase I human trials, vaccination experiments have been performed in cattle, a natural model for Schistosoma bovis. Vaccination of calves with the S. bovis GST has led to a reduction of ever 80% of egg output and tissue egg count. Significant levels of protection were also observed in goats after immunization with the recombinant S. bovis GST. Increasing evidence of the participation of IgA antibodies in protective immunity has prompted us toward the development of mucosal immunization. Preliminary results indicate that significant levels of protection can be achieved following oral immunization with live attenuated vectors or liposomes. These studies seem to represent a promising approach towards the future development of a vaccine strategy against one of major human parasitic diseases.

Selección de péptidos sintéticos del Virus de la Hepatitis G (GBV-C/HGV) inhibidores del Péptido de Fusión HIV-I

El GB virus C (GBV-C) o virus de l'hepatitis G (HGV) es un virus format per una única cadena de RNA que pertany a la familia Flaviviridae. En els últims anys, s'han publicat nombrosos treballs en els quals s'associa la coinfecció del GBV-C i del virus de la immunodeficiència humana (VIH) amb una menor progressió de l'esmentada malaltia així com amb una major supervivència dels pacients una vegada que la SIDA s'ha desenvolupat. El mecanisme pel qual el virus GBV-C/HGV exerceix un “efecte protector” en els pacients amb VIH encara no està descrit. L’estudi de la interacció entre els virus GBVC/HGV i VIH podria donar lloc al desenvolupament de nous agents terapèutics per al tractament de la SIDA.Treballs recents mostren com la capacitat inhibitòria del virus del GBV-C/HGV és deguda a la seva glicoproteina estructural E2. S’ha vist que aquesta proteina seria capaç d’inhibir la primera fase de replicació de VIH, així com la unió i la fusió amb les membranes cel•lulars. Sobre la base d’aquests estudis, l’objectiu d’aquest treball ha estat seleccionar inhibidors del pèptid de fusió del VIH utilitzant pèptids sintètics de la proteina E2 del GBV-C/HGV. El treball realitzat ha consistit en estudiar, utilitzant assajos biofísics de leakage i de lipid mixing, la capacitat dels pèptids de la proteina estructural del virus del GBV-C/HGV per inhibir la interacció i el procés de desestabilització de membranes induïdes pel pèptid de fusió de la glicoproteina de l’embolcall, GP41, del VIH. Aquests assajos, com es descriu en treballs anteriors, han resultat útils per a la selecció i la identificació de compostos amb activitat específica anti-GP41. Es pot afirmar que efectivament els pèptids seleccionats de la proteina E2 del virus del GBV-C/HGV inhibeixen l’activitat del pèptid de fusió del VIH probablement com a consequència d’un canvi conformacional en aquest darrer.

Mechanisms of skin adherence and invasion by dermatophytes.

Dermatophytes are keratinophilic fungi that can be pathogenic for humans and animals by infecting the stratum corneum, nails, claws or hair. The first infection step consists of adherence of arthroconidia to the stratum corneum. The mechanisms and the kinetics of adherence have been investigated using different in vitro and ex vivo experimental models, most notably showing the role of a secreted serine protease from Microsporum canis in fungal adherence to feline corneocytes. After germination of the arthroconidia, dermatophytes invade keratinised structures that have to be digested into short peptides and amino acids to be assimilated. Although many proteases, including keratinolytic ones, have been characterised, the understanding of dermatophyte invasion mechanisms remains speculative. To date, research on mechanisms of dermatophyte infection focused mainly on both secreted endoproteases and exoproteases, but their precise role in both fungal adherence and skin invasion should be further explored.

Desenvolupament de vacunes peptídiques y dendrímers basats en polietilenglicol per al tractament del càncer

El principal problema de les teràpies actuals contra el càncer es la baixa especificitat envers les cèl•lules tumorals, cosa que comporta gran quantitat d’efectes secundaris. Per això es important el desenvolupament de nous tipus de teràpies i sistemes d’alliberament efectius per als fàrmacs ja existents al mercat. En la immunoteràpia contra el càncer es pretén estimular el sistema immunològic per a eliminar les cèl•lules canceroses de manera selectiva. En aquest projecte s’han sintetitzat derivats de l’antigen peptídic de melanoma NY-ESO1 i s’ha estudiat la seva capacitat per a estimular el sistema immunològic com a vacunes contra el càncer. També s’han encapsulat el antígens peptídics en liposomes com a adjuvants i sistemes d’alliberament. De totes les variants peptídiques la que resultà més immunogènica fou la que contenia el grup palmitoil i el fragment toxoide tetànic en la seva estructura. La utilització de liposomes com a sistema adjuvant sembla una estratègia interessant per al disseny de vacunes contra el càncer donat que l’encapsulació del pèptid en liposomes va augmentar notablement la resposta immunològica de l’antigen. Per altra banda, s’han desenvolupat dendrímers basats en polietilenglicol com a sistemes alliberadors de fàrmacs per al tractament de tumors. El polietilenglicol és àmpliament utilitzat com a sistema d’alliberament de fàrmacs degut a les seves interessants propietats, augment de la solubilitat i dels temps de residència en plasma, entre d’altres. La metodologia química descrita permet la diferenciació controlada de varies posicions en la superfície del dendrímer a més del creixement del dendrímer fins a una segona generació. S’ha sintetitzat la primera generació del dendrímer contenint el fàrmac antitumoral 5-fluorouracil i s’han realitzat estudis de citotoxicitat comprovant que l’activitat del nanoconjugat és del mateix ordre de magnitud que el 5-fluorouracil sense conjugar.

Regulation of adaptive behaviour during fasting by hypothalamic Foxa2.

The lateral hypothalamic area is considered the classic 'feeding centre', regulating food intake, arousal and motivated behaviour through the actions of orexin and melanin-concentrating hormone (MCH). These neuropeptides are inhibited in response to feeding-related signals and are released during fasting. However, the molecular mechanisms that regulate and integrate these signals remain poorly understood. Here we show that the forkhead box transcription factor Foxa2, a downstream target of insulin signalling, regulates the expression of orexin and MCH. During fasting, Foxa2 binds to MCH and orexin promoters and stimulates their expression. In fed and in hyperinsulinemic obese mice, insulin signalling leads to nuclear exclusion of Foxa2 and reduced expression of MCH and orexin. Constitutive activation of Foxa2 in the brain (Nes-Cre/+;Foxa2T156A(flox/flox) genotype) results in increased neuronal MCH and orexin expression and increased food consumption, metabolism and insulin sensitivity. Spontaneous physical activity of these animals in the fed state is significantly increased and is similar to that in fasted mice. Conditional activation of Foxa2 through the T156A mutation expression in the brain of obese mice also resulted in improved glucose homeostasis, decreased fat and increased lean body mass. Our results demonstrate that Foxa2 can act as a metabolic sensor in neurons of the lateral hypothalamic area to integrate metabolic signals, adaptive behaviour and physiological responses.

Normal glucagon signaling and β-cell function after near-total α-cell ablation in adult mice.

OBJECTIVEEvaluate whether healthy or diabetic adult mice can tolerate an extreme loss of pancreatic α-cells and how this sudden massive depletion affects β-cell function and blood glucose homeostasis.RESEARCH DESIGN AND METHODSWe generated a new transgenic model allowing near-total α-cell removal specifically in adult mice. Massive α-cell ablation was triggered in normally grown and healthy adult animals upon diphtheria toxin (DT) administration. The metabolic status of these mice was assessed in 1) physiologic conditions, 2) a situation requiring glucagon action, and 3) after β-cell loss.RESULTSAdult transgenic mice enduring extreme (98%) α-cell removal remained healthy and did not display major defects in insulin counter-regulatory response. We observed that 2% of the normal α-cell mass produced enough glucagon to ensure near-normal glucagonemia. β-Cell function and blood glucose homeostasis remained unaltered after α-cell loss, indicating that direct local intraislet signaling between α- and β-cells is dispensable. Escaping α-cells increased their glucagon content during subsequent months, but there was no significant α-cell regeneration. Near-total α-cell ablation did not prevent hyperglycemia in mice having also undergone massive β-cell loss, indicating that a minimal amount of α-cells can still guarantee normal glucagon signaling in diabetic conditions.CONCLUSIONSAn extremely low amount of α-cells is sufficient to prevent a major counter-regulatory deregulation, both under physiologic and diabetic conditions. We previously reported that α-cells reprogram to insulin production after extreme β-cell loss and now conjecture that the low α-cell requirement could be exploited in future diabetic therapies aimed at regenerating β-cells by reprogramming adult α-cells.