Virus-like particle vaccine induces cross-protection against human metapneumovirus infections in mice

Human metapneumovirus (HMPV) is a paramyxovirus that causes acute respiratory-tract infections in children and adults worldwide. A safe and effective vaccine could decrease the burden of disease associated with this novel pathogen. We engineered HMPV viral-like particles (HMPV-VLPs) derived from retroviral core particles that mimic the properties of the viral surface of two HMPV viruses of either lineage A or B. These VLPs functionally display F and G HMPV surface glycoproteins. When injected in mice, HMPV-VLPs induce strong humoral immune response against both homologous and heterologous strains. Moreover, the induced neutralizing antibodies prevented mortality upon subsequent infection of the lungs with both homologous and heterologous viruses. Upon challenge, viral titers in the lungs of immunized animals were significantly reduced as compared to those of control animals. In conclusion, a HMPV-VLP vaccine that induces cross-protective immunity in mice is a promising approach to prevent HMPV infections.

Characterization of hepatitis C virus particle subpopulations reveals multiple usage of the scavenger receptor BI for entry steps

Hepatitis C virus (HCV) particles assemble along the very low density lipoprotein pathway and are released from hepatocytes as entities varying in their degree of lipid and apolipoprotein (apo) association as well as buoyant densities. Little is known about the cell entry pathway of these different HCV particle subpopulations, which likely occurs by regulated spatiotemporal processes involving several cell surface molecules. One of these molecules is the scavenger receptor BI (SR-BI), a receptor for high density lipoprotein that can bind to the HCV glycoprotein E2. By studying the entry properties of infectious virus subpopulations differing in their buoyant densities, we show that these HCV particles utilize SR-BI in a manifold manner. First, SR-BI mediates primary attachment of HCV particles of intermediate density to cells. These initial interactions involve apolipoproteins, such as apolipoprotein E, present on the surface of HCV particles, but not the E2 glycoprotein, suggesting that lipoprotein components in the virion act as host-derived ligands for important entry factors such as SR-BI. Second, we found that in contrast to this initial attachment, SR-BI mediates entry of HCV particles independent of their buoyant density. This function of SR-BI does not depend on E2/SR-BI interaction but relies on the lipid transfer activity of SR-BI, probably by facilitating entry steps along with other HCV entry co-factors. Finally, our results underscore a third function of SR-BI governed by specific residues in hypervariable region 1 of E2 leading to enhanced cell entry and depending on SR-BI ability to bind to E2.

The IgG autoimmune response in postpartum acquired hemophilia A targets mainly the A1a1 domain of FVIII

BACKGROUND

Acquired hemophilia A (AHA) is a severe life-threatening autoimmune disease due to the development of autoantibodies that neutralize the procoagulant activity of factor VIII (FVIII). In rare cases, AHA occurs in the postpartum period as a serious complication of an otherwise normal pregnancy and delivery. Due to its rarity, little is known about the features of the antibody response to FVIII in AHA.

OBJECTIVES

Our study wanted to (i) determine the epitope specificity and the immunoglobulin (Ig) subclasses of anti-FVIII autoantibodies in plasma samples from a large cohort of AHA patients, and (ii) compare the epitope specificity of anti-FVIII autoantibodies in plasma samples from postpartum AHA and other AHA patients.

PATIENTS/METHODS

Seventy-three plasma samples from patients with postpartum AHA (n = 10) or associated with malignancies (n = 16) or autoimmune diseases (n = 11) or without underlying disease (n = 36) were analyzed with three multiplexed assays.

RESULTS AND CONCLUSIONS

Our results showed a stronger response against the A1a1-A2a2-B fragments of FVIII and more specifically against the A1a1 domain in patients with postpartum AHA than in the other AHA groups (P < 0.01). Moreover, although IgG4 was the predominant IgG subclass in all groups, anti-A1a1-A2a2-B and anti-A1a1 domain autoantibodies of the IgG(1) and IgG3 subclasses were more frequently detected in postpartum AHA than in the other AHA groups. These findings support the involvement of the Th1-driven response in the generation of autoantibodies in women with postpartum AHA compared with the other groups of AHA patients in whom production of Th2-driven IgG4 was predominant.

Clearance of genotype 1b hepatitis C virus in chimpanzees in the presence of vaccine-induced E1-neutralizing antibodies

Accumulating evidence indicates that neutralizing antibodies play an important role in protection from chronic hepatitis C virus (HCV) infection. Efforts to elicit such responses by immunization with intact heterodimeric E1E2 envelope proteins have met with limited success. To determine whether antigenic sites, which are not exposed by the combined E1E2 heterodimer structure, are capable of eliciting neutralizing antibody responses, we expressed and purified each as separate recombinant proteins E1 and E2, from which the immunodominant hypervariable region (HVR-1) was deleted. Immunization of chimpanzees with either E1 or E2 alone induced antigen-specific T-helper cytokines of similar magnitude. Unexpectedly, the capacity to neutralize HCV was observed in E1 but not in animals immunized with E2 devoid of HVR-1. Furthermore, in vivo only E1-vaccinated animals exposed to the heterologous HCV-1b inoculum cleared HCV infection.

Mimotopes of mutalysin-II from Lachesis muta snake venom induce hemorrhage inhibitory antibodies upon vaccination of rabbits

Mutalysin-II (mut-II) from Lachesis muta snake venom is an endopeptidase with hemorrhagic activity. A mAb against mutalysin-II that neutralized the hemorrhagic effect was produced previously. To identify the mAb epitopes, sets of 15-mer overlapping peptides covering the mut-II amino acid sequence were synthesized using the SPOT method and tested but failed to react with the mAb. Using a phage-display approach seventeen clones reactive with mAb were identified. Additional immunoassays with the peptides and mAb identified the QCTMDQGRLRCR, TCATDQGRLRCT, HCFHDQGRVRCA, HCTMDQGRLRCR and SCMLDQGRSRCR sequences as possible epitopes. Immunization of rabbits with these peptides induced antibodies that recognize mut-II and protected against the hemorrhagic effects of Lachesis venom.

Immunodiagnosis of human neurocysticercosis using a synthetic peptide selected by phage-display

The usefulness of a synthetic peptide in the serodiagnosis of Taenia solium human neurocysticercosis (NC) has been evaluated. Phage-displayed peptides were screened with human antibodies to scolex protein antigen from cysticercus cellulosae (SPACc). One clone was found to interact specifically with anti-SPACc IgGs. The corresponding synthetic peptide was found to be recognized in ELISA by NC patient's sera. The study was carried out with sera from 28 confirmed NC patients, 13 control sera and 73 sera from patients suffering from other infectious diseases. A 93% sensibility and a 94.3% specificity was achieved. Figures of 89% and 31.4% of sensibility and specificity were obtained in a SPACc-based ELISA. Immunoblotting of SPACc with anti-peptide antibodies revealed a single band of approximately 45 kDa in 1D and four 45 kDa isoforms in 2D-gel electrophoresis. A strong and specific immunostaining in the fibers beneath the suckers, at the base of the rostellum, and in the tissue surrounding the scolex of cysticerci was observed by immunomicroscopy. Our results show that a peptide-based immunodiagnostic of neurocisticercosis can be envisioned.

Risk genotypes and haplotypes of the GLUT1 gene for type 2 diabetic nephropathy in the Tunisian population

OBJECTIVE

Diabetic nephropathy (DN) is a long-term complication of both type 1 and type 2 diabetes. Genetic studies on DN have been of little help so far, since several genetic association studies have shown conflicting results. Here we report the findings of a case-control study on five SNPs in the glucose transporter 1 (GLUT1) gene. The study investigated the association of five GLUT1 genotypes and haplotypes with DN.

RESEARCH DESIGN AND METHODS

All subjects, 126 DN (cases) and 273 type 2 diabetes (controls), were genotyped using the polymerase chain reaction restriction fragment length polymorphism.

RESULTS

The TT and the AA genotypes of the Haell and Enh2 SNP1, increased the risk of DN. The study also identified CGT as the highest risk haplotype (4.4-fold) followed by CAT with an increased risk of DN of 2.6-fold.

CONCLUSIONS

The GLUT1 gene confers susceptibility to DN in type 2 diabetes patients in the Tunisian population.

Association of glucose transporter 1 polymorphisms with type 2 diabetes in the Tunisian population

BACKGROUND

T2DM is a complex metabolic disease. Genetic studies on T2DM have been of little help so far because several genetic association studies have shown conflicting results. In this study, we report the findings of a case-control study on three SNPs in the GLUT1 gene. For this, we investigated the association of GLUT1 genotypes and haplotypes with T2DM.

RESEARCH DESIGN AND METHODS

All 273 T2DM subjects (cases) and 343 healthy subjects (controls) were genotyped using the polymerase chain reaction restriction fragment length polymorphism.

RESULTS

Results showed that the GT genotype of XbaI SNP could increase the risk of susceptibility to T2DM to 2.4 and that TAT is a 'risk haplotype' conferring a risk of 3.4 to T2DM.

CONCLUSION

The TAT haplotype of the GLUT1 gene confers susceptibility to T2DM in the Tunisian population.

Reactivity profile of anti-factor VIII antibodies with designed synthetic peptides mimicking epitopes of the C2 and a1 domains

Antibodies (Abs) that block factor VIII (FVIII) activity occur in hemophilia A patients treated with FVIII replacement therapy and severely impair treatment. In this work, we designed and synthesized ten peptides whose sequences are found in putative epitopes at the surface of a1 and C2 domains of the FVIII molecule. These peptides were screened for their ability to inhibit the binding of anti-FVIII Abs from plasmas of hemophilia A patients to FVIII. All peptides were efficient in inhibiting anti-FVIII Abs in plasma from patients with inhibitors, with however different efficiencies. It was found that each tested patient's plasma had a different profile of reactivity with peptides, consistent with an individual anti-FVIII Ab specificity. The profile of recognized peptides was also changing during the treatment of the patients. Three peptides were used in an affinity chromatography assay to attempt to remove anti-FVIII Abs from patients' plasma. Anti-FVIII IgGs were significantly captured by the peptide-Sepharose affinity matrixes as assessed by enzyme-linked immunosorbent assay. However, due to the low level of Abs in the plasma samples, other methods (Chromogenic and Bethesda assays) were not sensitive enough to properly detect the reduction of inhibitors.

The Loxtox protein family in Loxosceles intermedia (Mello-Leitão) venom

We isolated cDNA sequences coding for dermonecrotic/sphingomyelinases factor proteins from the brown spider Loxosceles intermedia, here named Loxtox proteins. The amino acid sequences based on cloned cDNA of several Loxtox proteins revealed at least six distinct groups of proteins expressed in the venom gland. The level of similarity among the toxins varied from 99% to 55%. The finding of several isoforms of Loxtox in the venom of this spider may reflect an evolutionary adaptation for different prey types and reinforces the idea of an efficient mutational mechanism in the venom gland of spiders.

Vascular emergencies in liver trauma

The use of CT in the diagnosis and management of liver trauma is responsible for the shift from routine surgical versus non-surgical treatment in the management of traumatic liver injuries, even when they are of high grade. The main cause of complication and of death in liver trauma is related to vascular injury. The goal of this review focussed on the vascular complications of liver trauma is to describe the elementary lesions shown by CT in liver trauma including laceration, parenchymal hematoma and contusions, partial devascularisation, subcapsular hematomas, hemoperitoneum, active bleeding, pseudoaneurysm of the hepatic artery, bile leak, and periportal oedema, to illustrate the possible pitfalls in CT diagnosis of liver trauma and to underline the key-points which may absolutely be present in a CT report of liver trauma. Then we will remind the grading system based on the CT features and we will analyze the interest and limitations of such grading systems. Last we will discuss the diagnostic strategy at the early phase in patients with suspected liver trauma according to their clinical conditions and underline the conditions of arterial embolization, and then we will discuss the diagnosis strategy at the delayed phase according to the suspected complications.

An acidic cluster of the cytoplasmic tail of the RD114 virus glycoprotein controls assembly of retroviral envelopes

Retroviral core proteins, Gag and envelope (Env) glycoproteins are expressed from distinct cellular areas and therefore need to encounter to assemble infectious particles. The intrinsic cell localisation properties of either viral component or their capacity to mutually interact determines the assembly of infectious particles. Here, we address how Env determinants and cellular sorting proteins allow the Env derived from gamma retroviruses, murine leukemia virus (MLV) and RD114, to travel to or from late endosomes (LE), which may represent the Env assembly site of retroviruses in some cells. The individual expression of MLV Env resulted in its accumulation in LE in contrast to RD114 Env that required the presence of gamma retroviral Gag proteins. To discriminate between intrinsic intracellular Env localisation and gamma retroviral Gag/Env interactions in influencing Env viral incorporation, we studied Env assembly on heterologous lentiviral particles on which they are passively recruited. We found that an acidic cluster present at the C-terminus of the RD114 Env cytoplasmic tail determines its sub-cellular localisation and retrograde transport. Mutation of this motif induced late endosomal concentration of the RD114 Env, correlating with increased viral incorporation and infectivity. Reciprocally, the reinforcement of a poorly functional acidic motif in the MLV Env resulted in a marked decrease of its late endosomal localisation, leading to weakly infectious lentiviral particles with low Env densities. Finally, through upregulation versus downregulation of its cellular expression, we show that phosphofurin acidic-cluster-sorting protein 1 (PACS-1) controls the function of the RD114 Env acidic cluster, assigning to this cellular effector a crucial role in modulation of Env assembly of some retroviruses.

Functional characterization and epitope analysis of a recombinant dermonecrotic protein from Loxosceles intermedia spider

In the present study the recombinant form (recLiD1) of a dermonecrotic protein present in the Brazilian brown spider Loxosceles intermedia venom was expressed in Escherichia coli cells and purified by reversed-phase HPLC using a C8 Vydac column. About 25.8mg of purified recLiD1 was produced from a litre of bacterial culture. SDS/PAGE and immunoblot analysis of the recombinant protein revealed an apparent molecular weight of 32-35kDa. The later result was confirmed by mass spectrometry (32,758Da). recLiD1 displayed dermonecrotic and platelet aggregation activities which were qualitatively similar to that displayed by the crude L. intermedia venom. However, very low sphingomyelinase D enzymatic activity and complement-dependent haemolytic activities were observed. recLiD1 immunized BALB/c mice developed an antibody response. Anti-recLiD1 antibodies recognized L. intermedia venom in an indirect enzyme-linked immunosorbent assay (ELISA) and cross-reacted with crude venoms from L. intermedia, L. gaucho and L. laeta. An in vivo protection assay carried out 5 weeks after the end of the immunization protocol showed that 75% of the vaccinated mice could resist the challenge by 2.5LD(50) of L. intermedia venom. To characterize epitopes associated with protective antibodies, we prepare sets of immobilized synthetic 15 mer overlapping peptides covering the complete amino acid sequences of the recLiD1. Antibodies revealed one antigenic region in the N-terminal part of the toxin. The amino acid sequence of this epitope was found in several dermonecrotic proteins and some of its residues have been implicated with the active site of the toxin.

Antibodies against synthetic epitopes inhibit the enzymatic activity of mutalysin II, a metalloproteinase from bushmaster snake venom

Mutalysin II (mut-II), a 22.5kDa zinc endopeptidase isolated from bushmaster (Lachesis muta muta) snake venom, is a direct acting fibrin(ogen)olytic proteinase. It induces monoclonal and polyclonal antibodies which efficiently neutralize the hemorrhagic effect of L. muta and several Bothrops whole venoms. To characterize epitopes of protective antibodies we have used the Spot method of multiple peptide synthesis to prepare 64 overlapping dodecapeptides frameshifted by three residues, covering the complete amino acid sequence of mut-II. The rabbit anti-mut-II antibodies binding pattern to peptides revealed several continuous antigenic regions: one in the N-terminal part, two in the central region and the other in the C-terminal of mut-II. By using homology modelling, a three-dimensional model of mut-II was built which showed that epitopes are surface exposed. Anti-peptide antibodies were raised against three peptides (one representative of each epitope region) covalently coupled as a mixture to keyhole limpet hemocyanin. Purified IgG from the resulting anti- peptide antibodies cross-reacted with mut-II and induced a dose-dependent inhibition of the mut-II catalyzed proteolysis of fibrinogen.

High Density Lipoprotein Inhibits Hepatitis C Virus-neutralizing Antibodies by Stimulating Cell Entry via Activation of the Scavenger Receptor BI

Hepatitis C virus (HCV) exploits serum-dependent mechanisms that inhibit neutralizing antibodies. Here we demonstrate that high density lipoprotein (HDL) is a key serum factor that attenuates neutralization by monoclonal and HCV patient-derived polyclonal antibodies of infectious pseudo-particles (HCVpp) harboring authentic E1E2 glycoproteins and cell culture-grown genuine HCV (HCVcc). Over 10-fold higher antibody concentrations are required to neutralize either HCV-enveloped particles in the presence of HDL or human serum, and less than 3-5-fold reduction of infectious titers are obtained at saturating antibody concentrations, in contrast to complete inhibition in serum-free conditions. We show that HDL interaction with the scavenger receptor BI (SR-BI), a proposed cell entry co-factor of HCV and a receptor mediating lipid transfer with HDL, strongly reduces neutralization of HCVpp and HCVcc. We found that HDL activation of target cells strongly stimulates cell entry of viral particles by accelerating their endocytosis, thereby suppressing a 1-h time lag during which cell-bound virions are not internalized and can be targeted by antibodies. Compounds that inhibit lipid transfer functions of SR-BI fully restore neutralization by antibodies in human serum. We demonstrate that this functional HDL/SR-BI interaction only interferes with antibodies blocking HCV-E2 binding to CD81, a major HCV receptor, reflecting its prominent role during the cell entry process. Moreover, we identify monoclonal antibodies targeted to epitopes in the E1E2 complex that are not inhibited by HDL. Consistently, we show that antibodies targeted to HCV-E1 efficiently neutralize HCVpp and HCVcc in the presence of human serum.

Assembly of functional hepatitis C virus glycoproteins on infectious pseudoparticles occurs intracellularly and requires concomitant incorporation of E1 and E2 glycoproteins

Hepatitis C virus (HCV) E1 and E2 envelope glycoproteins (GPs) displayed on retroviral cores (HCVpp) are a powerful and highly versatile model system to investigate wild-type HCV entry. To further characterize this model system, the cellular site of HCVpp assembly and the respective roles of the HCV GPs in this process were investigated. By using a combination of biochemical methods with confocal and electron microscopic techniques, it was shown that, in cells producing HCVpp, both E1 and E2 colocalized with retroviral core proteins intracellularly, presumably in multivesicular bodies, but not at the cell surface. When E1 and E2 were expressed individually with retroviral core proteins, only E2 colocalized with and was incorporated on retroviral cores. Conversely, the colocalization of E1 with retroviral core proteins and its efficient incorporation occurred only upon co-expression of E2. Moreover, HCVpp infectivity correlated strictly with the presence of both E1 and E2 on retroviral cores. Altogether, these results confirm that the E1E2 heterodimer constitutes the prebudding form of functional HCV GPs and, more specifically, show that dimerization with E2 is a prerequisite for efficient E1 incorporation onto particles.