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Results for “Protein Subunit Vaccines”

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At least 73 records · Page 4Linked to original sources

PubMed2005

Vaccine potential of recombinant Ornithobacterium rhinotracheale antigens.

Ornithobacterium rhinotracheale is a pathogen involved in respiratory infection and systemic disease in poultry. Previously, eight potential vaccine candidates were identified that induced cross-protective immunity when administered to chickens as a multi-component vaccine. In this study, we analyzed the immunogenicity of these eight recombinant proteins by subunit vaccination, and characterized the different proteins and corresponding genes more thoroughly by sequencing, in vitro expression analysis, and cellular localization experiments. We found, that all genes encoding the eight antigens were highly conserved among different O. rhinotracheale serotypes, but the different antigens were not expressed by all serotypes. Cellular fractionation experiments indicated that the majority of the antigens are predominantly located in the outer membrane fraction. Vaccination of chickens with single-antigen vaccines demonstrated that the Or77 antigen was protective against serotypes that expressed Or77 in vitro, suggesting that the protein has strong potential as a vaccine antigen. Furthermore, immunization with four-component subunit vaccines indicated the existence of immunogenic synergism between the candidate vaccine antigens.

Air Sacs↗

PubMed2003

Clinical experience with respiratory syncytial virus vaccines.

Respiratory syncytial virus (RSV) infection is at times associated with life-threatening lower respiratory tract illness in infancy. Severe infection during the first year of life may be an important risk factor or indicator for the development of asthma in early childhood. Severe infections primarily occur in healthy infants, and young infants and children with specific risk factors. However, RSV causes respiratory infections in all age groups. Indeed it is now recognized that RSV disease is responsible for significant morbidity and mortality in the geriatric population. RSV infection remains difficult to treat, and prevention is a worldwide goal. For this reason there has been an intensive effort to develop an effective and safe RSV vaccine. Initial infection with RSV affords limited protection to reinfection, yet repeated episodes decrease the risk for lower respiratory tract illness. In the 20 years from 1960 to 1980, trials of several candidate RSV vaccines failed to attain the desired safety and protection against natural infection. Some vaccine types either failed to elicit immunogenicity, as with the live subcutaneous vaccine, or resulted in exaggerated disease on natural exposure to the virus, as with the formalin-inactivated (FI) type. Currently vaccine candidates are being developed based on the molecular virology of RSV. Recent formulations of candidate RSV vaccines have focused on subunit vaccines [such as purified fusion protein (PFP)], subunit vaccines combined with nonspecific immune activating adjuvants, live attenuated vaccines (including cold passaged, temperature-sensitive or cpts mutants), genetically engineered live attenuated vaccines and polypeptide vaccines.

Child↗

PubMed2003

Virus-like particles as immunogens.

Subunit vaccines based on recombinant proteins can suffer from poor immunogenicity owing to incorrect folding of the target protein or poor presentation to the immune system. Virus-like particles (VLPs) represent a specific class of subunit vaccine that mimic the structure of authentic virus particles. They are recognized readily by the immune system and present viral antigens in a more authentic conformation than other subunit vaccines. VLPs have therefore shown dramatic effectiveness as candidate vaccines. Here, we review the current status of VLPs as vaccines, and discuss the characteristics and problems associated with producing VLPs for different viruses.

Adjuvants, Immunologic↗

PubMed2001

Development of a quantitative assay for residual host cell proteins in a recombinant subunit vaccine against human respiratory syncytial virus.

We have developed and validated a process-specific immunoligand assay based on the Threshold system for the quantification of residual host cell proteins (HCPs) in a recombinant subunit vaccine candidate against the human respiratory syncytial virus (hRSV). The industrial process of this vaccine produced in Escherichia coli, involved five chromatography steps for the production of clinical-grade batches. The clearance of non-product-related protein throughout the purification process was documented by the evaluation of the HCP content in the chromatographic fractions at each step of the downstream processing. The assay had a detection limit of 0.5 ng/ml of HCP equivalent to 10 parts per million (ppm). The quantification limit was 1.3 ng/ml of HCP, giving a sensitivity range of the assay of 10 to 30 ppm. To our knowledge, this is the first sensitive HCP assay reported for a vaccine.

Antibodies, Bacterial↗

PubMed2005

Protection of macaques against Mycobacterium tuberculosis infection by a subunit vaccine based on a fusion protein of antigen 85B and ESAT-6.

Various new tuberculosis (TB) vaccine candidates in combination with new delivery systems, including subunit vaccines, are currently being evaluated by a number of laboratories. One vaccine candidate that has shown promising protective capacity in mice and guinea pigs is a fusion of Ag85B and ESAT-6. In this study, we have investigated the efficacy of this Ag85B-ESAT-6 fusion protein vaccine in a non-human primate model for TB. Vaccination of cynomolgus monkeys with the Ag85B-ESAT-6 fusion protein in two different adjuvant (DDA/MPL, AS02A) resulted in a reduction in bacterial number and/or lung pathology in animals challenged with Mycobacterium tuberculosis. Vaccination prevented an increase in C-reactive protein serum levels, general activation of CD4 and CD8 subsets and boosted development of humoral and cellular immune responses to a spectrum of mycobacterial antigens on exposure to M. tuberculosis infection. We show, in two independent experiments, that vaccination of primates with Ag85B-ESAT-6 induces protective immune responses, suggesting that Ag85B-ESAT-6 is a strong candidate for further clinical evaluation. As far as we are aware this is the first report of protection in primates with a subunit vaccine.

Acyltransferases↗

PubMed2003

Targeting of plant-derived vaccine antigens to immunoresponsive mucosal sites.

Most pathogenic microorganisms enter their host via the mucosal surfaces lining the digestive, respiratory and urino-reproductive tracts of the body. The most efficient means of protecting these surfaces is through mucosal immunization. Transgenic plants are safe and inexpensive vehicles to produce and mucosally deliver protective antigens. However, the application of this technology is limited by the poor response of the immune system to non-particulate, subunit vaccines. Co-delivery of therapeutic proteins with targeting proteins, such as the B subunit of the Escherichia coli heat labile enterotoxin (LTB), could increase the effectiveness of such antigens.

Antigens↗

PubMed2005

Mycobacterial 70 kD heat-shock protein is an effective subunit vaccine against bovine paratuberculosis.

Paratuberculosis is a chronic granulomatous inflammation of the small intestine of cattle and other ruminants, caused by infection with Mycobacterium avium ssp. paratuberculosis (MAP). The disease can be found in ruminant herds worldwide, causing substantial economic losses at farm level due to premature culling and production losses. In previous studies, it has been shown that immune responses to recombinant MAP Hsp70 proteins were predominantly cell mediated. As protective immunity to the intracellular mycobacterial pathogens is thought to be cell-mediated in origin, we have studied the use of a recombinant MAP Hsp70 as a subunit vaccine in cattle experimentally infected with MAP. The results of the current study demonstrate that recombinant MAP Hsp70 can be successfully used as a subunit vaccine against bovine paratuberculosis, significantly reducing shedding of bacteria in feces during the first 2 years following experimental infection.

Animals↗

PubMedDate not supplied

A novel method for the rational construction of well-defined immunogens: the use of oximation to conjugate cholera toxin B subunit to a peptide-polyoxime complex.

Cholera toxin B subunit (CTB), capable of binding to all mucous membranes in its pentameric form, is a potential carrier of mucosal vaccines. In our previous work we reported that the N-terminus of CTB, a threonine, could in principle undergo oxidation and oximation to form conjugates with a cascade of immunogenic peptides. In this study, we set up a model by chemically coupling CTB to a polyoxime that possessed five copies of influenza virus-derived peptides displayed in comblike form. The construct was reconstituted into pentameric form when eluted from a Superdex column after conjugation, and the pentameric nature of this CTB-viral peptide complex was confirmed by SDS-PAGE. GM(1)-ELISA assay showed that the binding properties of CTB-viral peptide complex were increased 4-5-fold over native CTB.

Cholera Toxin↗

PubMed1991

Stimulation of adherent cells by addition of purified proteins of viral hemorrhagic septicemia virus to trout kidney cell cultures.

Purified proteins of the virus causing viral hemorrhagic septicemia in the trout were added to cultures on semisolid medium of leukocytes obtained from either healthy or immunized rainbow trout. Adherent cells were specifically stimulated by the glycoprotein of the viral spikes and, to a lesser extent, by the nucleoproteins. In contrast, a specific memory response was associated more with the nucleoproteins than with the glycoprotein when leukocytes from trout immunized with the virus were employed. These results suggest the necessity of employing both proteins in subunit vaccination trials and the possibility of using this assay to select the proper epitopes for genetically engineered proteins during subunit vaccine development.

Animals↗

PubMed2006

Humoral immune responses by prime-boost heterologous route immunizations with CTB-MPR(649-684), a mucosal subunit HIV/AIDS vaccine candidate.

CTB-MPR(649-684) is a translational fusion protein consisting of the cholera toxin B subunit and a 36-residue peptide, MPR(649-684), corresponding to the conserved membrane proximal ectodomain of gp41. CTB-MPR(649-684) was previously shown to induce HIV-1 transcytosis-blocking antibodies in mice. In this report, we describe an effective immunization regimen for this novel anti HIV-1 vaccine-candidate. Bacterially-produced CTB-MPR(649-684) was intranasally and/or intraperitoneally administered to investigate several prime-boost heterologous route immunization regimens. Mucosal priming with the adjuvant cholera toxin elicited significant levels of vaginal IgA and serum IgG specific to MPR(649-684). Systemic boosting after mucosal priming enhanced the levels of serum and mucosal antibodies. Systemic priming induced a strong serum anti-MPR(649-684) IgG response, which was efficiently recalled and augmented by either systemic or mucosal boosting. However, this regimen was less effective in inducing secretory anti-MPR(649-684) IgA. The serum anti-MPR(649-684) IgG subtype profile revealed that both IgG1 and IgG2a were induced in all the immunization regimens, and that mucosal co-administration of cholera toxin shifted the bias to the latter subtype. We concluded that, of the various immunization regimens examined here, mucosal priming with adjuvant followed by systemic boosting exhibited the best response in respect to either systemic or mucosal anti-MPR(649-684) antibodies. Most importantly, mucosal antibodies elicited by this regimen significantly inhibited HIV-1 transcytosis in a human tight epithelium model.

AIDS Vaccines↗

PubMed2026

Chimeric vaccine based on Iraqi HLA alleles against a predominant local Escherichia coli phylogroup.

INTRODUCTION: Escherichia coli remains amongst the most globally important pathogens implicated in severe clinical manifestations. The progressive rise in multidrug-resistant strains highlights the urgent need for new vaccines. Therefore, this study was designed to develop a new multi-epitope vaccine containing the most conserved epitopes across E. coli pathotypes. Consequently, the study aimed to investigate the immunoadjuvant role of faecal microbiota transplantation in enhancing vaccine efficacy. METHODS: Eighteen of the most conserved B-cell and T-cell epitopes of FimH, LptD, and BamA proteins were selected and included in a single construct. During the epitope selection process, HLA alleles predominant in the Iraqi population, as reported in previous studies, were used as criteria for selecting T-cell epitopes. The chimeric protein was expressed in BL21 E. coli and purified using affinity chromatography. Vaccine cross-protective immunity and protection were tested in in vivo experiments. Different formulations were used in the experimental evaluation: three doses of 100 μg of purified chimeric protein, injected intraperitoneally alone or encapsulated in PLGA nanoparticles, after faecal microbiota transplantation with and without gut microbiota modulation mediated by a cocktail of antibiotics. IgG1, IL-4, INF-γ, and NLRP3 levels were measured at 30 and 75 days after the first immunisation dose. Immunised mice were challenged with the local B2 UPEC phylogroup, and protection efficacy was considered 48 h later. Finally, the histological effects of the different chimeric protein formulations on the liver were assessed. RESULTS: All vaccine formulations except those after faecal microbiota transplantation without gut microbiota modulation induce significant increases in IgG1, IL-4, and INF-γ levels at different times. Only vaccination after faecal microbiota transplantation with gut microbiota modulation elicited robust NLRP3 levels at 30 and 75 days after, and this was linked to the highest reduction in bladder bacterial load by 813-fold compared to the other formulations, as well as the mildest effect on liver histological changes. DISCUSSION: These results demonstrated that the chimeric vaccine provides preliminary protection against a local B2 UPEC isolate. Furthermore, modulating gut microbiota via faecal transplantation markedly enhances the immunogenicity and protective efficacy of vaccination, suggesting its adjuvanticity.

Animals↗

PubMed2004

Receptor-binding domain of SARS-CoV spike protein induces highly potent neutralizing antibodies: implication for developing subunit vaccine.

The spike (S) protein of severe acute respiratory syndrome (SARS) coronavirus (CoV), a type I transmembrane envelope glycoprotein, consists of S1 and S2 domains responsible for virus binding and fusion, respectively. The S1 contains a receptor-binding domain (RBD) that can specifically bind to angiotensin-converting enzyme 2 (ACE2), the receptor on target cells. Here we show that a recombinant fusion protein (designated RBD-Fc) containing 193-amino acid RBD (residues 318-510) and a human IgG1 Fc fragment can induce highly potent antibody responses in the immunized rabbits. The antibodies recognized RBD on S1 domain and completely inhibited SARS-CoV infection at a serum dilution of 1:10,240. Rabbit antisera effectively blocked binding of S1, which contains RBD, to ACE2. This suggests that RBD can induce highly potent neutralizing antibody responses and has potential to be developed as an effective and safe subunit vaccine for prevention of SARS.

Animals↗

PubMed2006

A protein-based smallpox vaccine protects mice from vaccinia and ectromelia virus challenges when given as a prime and single boost.

The heightened concern about the intentional release of variola virus has led to the need to develop safer smallpox vaccines. While subunit vaccine strategies are safer than live virus vaccines, subunit vaccines have been hampered by the need for multiple boosts to confer optimal protection. Here we developed a protein-based subunit vaccine strategy that provides rapid protection in mouse models of orthopoxvirus infections after a prime and single boost. Mice vaccinated with vaccinia virus envelope proteins from the mature virus (MV) and extracellular virus (EV) adjuvanted with CpG ODN and alum were protected from lethal intranasal challenge with vaccinia virus and the mouse-specific ectromelia virus. Organs from mice vaccinated with three proteins (A33, B5 and L1) and then sacrificed after challenge contained significantly lower titers of virus when compared to control groups of mice that were not vaccinated or that received sub-optimal formulations of the vaccine. Sera from groups of mice obtained prior to challenge had neutralizing activity against the MV and also inhibited comet formation indicating anti-EV activity. Long-term partial protection was also seen in mice challenged with vaccinia virus 6 months after initial vaccinations. Thus, this work represents a step toward the development of a practical subunit smallpox vaccine.

Adjuvants, Immunologic↗

PubMed2003

A subunit vaccine against the adenovirus egg-drop syndrome using part of its fiber protein.

In this study, the effectiveness of antibodies against the hexon, fiber or a fiber fragment of an avian adenovirus egg-drop syndrome (EDS), in neutralizing the virus was tested. The fiber protein is responsible for binding the virus to the target cell. The fiber fragment knob-s comprises the carboxy-terminal knob domain and 34 amino acids of the immediately adjacent shaft domain of the adenovirus fiber protein. The hexon, fiber capsid protein and knob-s were produced in E. coli and injected into chickens. Antibodies that were produced against the whole fiber protein showed some hemagglutination inhibition (HI) activity. Antibodies produced against the knob-s protein showed HI activity and serum neutralization (SN) activity similar to the positive control-whole virus vaccine. We assume that production of only part of the fiber enables the protein produced in E. coli to fold correctly. Antibodies produced against the hexon protein showed no SN activity. In summary, knob-s induced SN and HI antibodies against EDS virus at a rate similar to the whole virus and were significantly more efficient than the full-length fiber. The recombinant knob-s protein may be used as a vaccine against pathogenic adenovirus infections.

Adenoviridae Infections↗

PubMed2005

Purification of phocid herpesvirus type 1 glycoproteins B and D and pilot studies of immunogenicity in mice.

In the process of developing a subunit vaccine against phocid herpesvirus type 1, we have cloned and expressed the glycoproteins B and D (gB and gD) of phicid herpesvirus type 1, using an eukaryotic baculovirus expression system. To establish the proof of concept, candidate iscom vaccines based on these affinity-purified proteins either alone or in combination, were tested for their immunogenicity in BALB/C mice. Mice immunised with a combination of gB and gD developed higher antibody and proliferative T cell responses against PhHV-1 than those immunised with gB or gD alone. The corresponding antibody and T cell proliferative responses were higher against PhHV-1 than against FHV. These data favour further testing of these candidate vaccines based on gB and gD in the FHV-cat model.

Animals↗

PubMed1988

Mechanisms of immunodominance in T-cell recognition, with applications to vaccine design.

Immunodominant T-cell antigenic sites can so dominate a response that their presence leads to high responsiveness and their absence to low responsiveness. Therefore, it is important to locate such sites for vaccine development. Factors that lead to immunodominance include features extrinsic to the structure of the site itself, such as the major histocompatibility complex (MHC) molecules of the host and the types of fragments produced by processing of the protein antigen before the T cell sees it. They also include factors intrinsic to the structure of the T-cell site, that determine a repertoire of potential immunodominant sites from which the extrinsic factors select a subset that will be immunodominant in a given individual. We have focused on one of these intrinsic factors, helical amphipathicity, that we have found to be a common feature among both helper and cytotoxic T-cell antigenic sites, suggesting that the same physical principles apply to sites seen in association with class I and class II MHC molecules. We have used this feature to locate immunodominant epitopes on the circumsporozoite protein of the Plasmodium falciparum malaria parasite and the envelope protein of the AIDS virus. Both helper and cytotoxic T-cell epitopes were identified. At least in the case of the helper T-cell sites, it was striking that the same sites in both the malaria and AIDS proteins studied that were immunodominant in the mouse were also immunodominant in the human, an indication that the same principles apply across species, and that the animal model will be useful for identifying sites to be used in vaccines for humans. These sites have been coupled with neutralizing antibody sites to produce artificial constructs that can elicit antibodies. It is hoped that the rational design of more complex versions of these artificial constructs will produce vaccines that are more effective than the natural pathogen proteins used in subunit vaccines, since such pathogen protein antigens have been selected through evolution to evade the immune system, not to optimize immunogenicity.

Animals↗

PubMed2000

Serum neutralizing antibody titers of seropositive chimpanzees immunized with vaccines coformulated with natural fusion and attachment proteins of respiratory syncytial virus.

Subunit vaccines formulated with purified fusion proteins from the A2 (PFP-2) or attenuated 248/404 (PFP-3) strains of respiratory syncytial virus (RSV) were evaluated, either alone or in combination with native attachment (G) protein, for their ability to augment serum neutralizing antibody titers in seropositive chimpanzees. The results suggested that combination vaccines enhanced serum neutralizing antibody titers against both laboratory strains and clinical isolates of RSV. When compared with PFP-2 alone, the resultant neutralizing antibody titers after vaccination with PFP-2+Ga protein were significantly elevated against 71% of A strains tested. In a confirmatory experiment, immunization with PFP-3+Ga+Gb proteins resulted in elevated serum neutralizing antibody titers against 86% of A and 50% of B strains tested versus injection with PFP-3 alone. The results suggest that subunit vaccines composed of both PFP and G proteins have more potential than PFP alone to augment neutralizing antibody titers in seropositive recipients.

Animals↗

PubMed2005

Influence of intron and exon splicing enhancers on mammalian cell expression of a truncated spike protein of SARS-CoV and its implication for subunit vaccine development.

The spike (S) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) is important for vaccine development. A truncated S protein of the TW1 strain, STR2 (88 kDa), carrying three S fragments (S74-253, S294-739, and S1129-1255) was investigated to study the influences of intron and exon splicing enhancers to improve STR2 protein expression in mammalian cells. Our results showed that STR2 protein expression with the use of an 138 base-pair intron addition increased by 1.9-, 2.5-, and 4.1-fold in Vero E6, QBI-293A cells, and CHO/dhFr- cells (dihydrofolate reductase [dhfr] gene deficient CHO cells), respectively. Using the exon splicing enhancers, including a bidirectional splicing enhancer (BSE) or an exon splicing enhancer derived from the EDA alternative exon of the fibronectin gene (EDA ESE), were also found to increase STR2 protein expression in CHO/dhFr- cells by 1.7- and 2.6-fold. Nevertheless, combination of the intron and the exon splicing enhancers resulted in suppressing the intron-enhancing e STR2 protein expression in in CHO/dhFr- cells. Our studies also demonstrated the STR2 protein was mainly as the Endo H-sensitive glycoprotein (115 kDa) expressed in Vero E6, QBI-293A, and CHO/dhFr- cells. However, only a minor form of the Endo H-resistant glycoproteins ( approximately 130 kDa) was detected in CHO/dhFr- cells. Taken together, our results indicated that intron had a better enhancing effect on STR2 protein expression than exon splicing enhancers, and the expression of approximately 130 kDa STR2 glycoprotein was enhanced by the intron addition into the expression vector construct. Results of the present study can provide an optimal strategy to enhance SARS-CoV S protein expression in mammalian cells and may contribute to the development of SARS-CoV subunit vaccine.

Animals↗