Enhancement of immunoglobulin G2a and cytotoxic T-lymphocyte responses by a booster immunization with recombinant hepatitis C virus E2 protein in E2 DNA-primed mice

Potentiating the Cross-Reactive IFN-γ T Cell and Polyfunctional T Cell Responses by Heterologous GX-19N DNA Booster in Mice Primed with Either a COVID-19 mRNA Vaccine or Inactivated Vaccine

Waning vaccine-induced immunity, coupled with the emergence of SARS-CoV-2 variants, has inspired the widespread implementation of COVID-19 booster vaccinations. Here, we evaluated the potential of the GX-19N DNA vaccine as a heterologous booster to enhance the protective immune response to SARS-CoV-2 in mice primed with either an inactivated virus particle (VP) or an mRNA vaccine. We found that in the VP-primed condition, GX-19N enhanced the response of both vaccine-specific antibodies and cross-reactive T Cells to the SARS-CoV-2 variant of concern (VOC), compared to the homologous VP vaccine prime-boost. Under the mRNA-primed condition, GX-19N induced higher vaccine-induced T Cell responses but lower antibody responses than the homologous mRNA vaccine prime-boost. Furthermore, the heterologous GX-19N boost induced higher S-specific polyfunctional CD4⁺ and CD8⁺ T cell responses than the homologous VP or mRNA prime-boost vaccinations. Our results provide new insights into booster vaccination strategies for the management of novel COVID-19 variants.

Multi-omic network-based interrogation of rat liver metabolism following gastric bypass surgery featuring SWATH proteomics

Morbidly obese patients often elect for Roux-en-Y gastric bypass (RYGB), a form of bariatric surgery that triggers a remarkable 30% reduction in excess body weight and reversal of insulin resistance for those who are type II diabetic. A more complete understanding of the underlying molecular mechanisms that drive the complex metabolic reprogramming post-RYGB could lead to innovative non-invasive therapeutics that mimic the beneficial effects of the surgery, namely weight loss, achievement of glycemic control, or reversal of non-alcoholic steatohepatitis (NASH). To facilitate these discoveries, we hereby demonstrate the first multi-omic interrogation of a rodent RYGB model to reveal tissue-specific pathway modules implicated in the control of body weight regulation and energy homeostasis. In this study, we focus on and evaluate liver metabolism three months following RYGB in rats using both SWATH proteomics, a burgeoning label free approach using high resolution mass spectrometry to quantify protein levels in biological samples, as well as MRM metabolomics. The SWATH analysis enabled the quantification of 1378 proteins in liver tissue extracts, of which we report the significant down-regulation of Thrsp and Acot13 in RYGB as putative targets of lipid metabolism for weight loss. Furthermore, we develop a computational graph-based metabolic network module detection algorithm for the discovery of non-canonical pathways, or sub-networks, enriched with significantly elevated or depleted metabolites and proteins in RYGB-treated rat livers. The analysis revealed a network connection between the depleted protein Baat and the depleted metabolite taurine, corroborating the clinical observation that taurine-conjugated bile acid levels are perturbed post-RYGB.

Combined adenovirus vector and hepatitis C virus envelope protein prime-boost regimen elicits T cell and neutralizing antibody immune responses

Despite the recent progress in the development of new antiviral agents, hepatitis C virus (HCV) infection remains a major global health problem, and there is a need for a preventive vaccine. We previously reported that adenoviral vectors expressing HCV nonstructural proteins elicit protective T cell responses in chimpanzees and were immunogenic in healthy volunteers. Furthermore, recombinant HCV E1E2 protein formulated with adjuvant MF59 induced protective antibody responses in chimpanzees and was immunogenic in humans. To develop an HCV vaccine capable of inducing both T cell and antibody responses, we constructed adenoviral vectors expressing full-length and truncated E1E2 envelope glycoproteins from HCV genotype 1b. Heterologous prime-boost immunization regimens with adenovirus and recombinant E1E2 glycoprotein (genotype 1a) plus MF59 were evaluated in mice and guinea pigs. Adenovirus prime and protein boost induced broad HCV-specific CD8+ and CD4+ T cell responses and functional Th1-type IgG responses. Immune sera neutralized luciferase reporter pseudoparticles expressing HCV envelope glycoproteins (HCVpp) and a diverse panel of recombinant cell culture-derived HCV (HCVcc) strains and limited cell-to-cell HCV transmission. This study demonstrated that combining adenovirus vector with protein antigen can induce strong antibody and T cell responses that surpass immune responses achieved by either vaccine alone.

IMPORTANCE

HCV infection is a major health problem. Despite the availability of new directly acting antiviral agents for treating chronic infection, an affordable preventive vaccine provides the best long-term goal for controlling the global epidemic. This report describes a new anti-HCV vaccine targeting the envelope viral proteins based on adenovirus vector and protein in adjuvant. Rodents primed with the adenovirus vaccine and boosted with the adjuvanted protein developed cross-neutralizing antibodies and potent T cell responses that surpassed immune responses achieved with either vaccine component alone. If combined with the adenovirus vaccine targeting the HCV NS antigens now under clinical testing, this new vaccine might lead to a stronger and broader immune response and to a more effective vaccine to prevent HCV infection. Importantly, the described approach represents a valuable strategy for other infectious diseases in which both T and B cell responses are essential for protection.

An assessment of the use of chimpanzees in hepatitis C research past, present and future: 1. Validity of the chimpanzee model

The USA is the only significant user of chimpanzees in biomedical research in the world, since many countries have banned or limited the practice due to substantial ethical, economic and scientific concerns. Advocates of chimpanzee use cite hepatitis C research as a major reason for its necessity and continuation, in spite of supporting evidence that is scant and often anecdotal. This paper examines the scientific and ethical issues surrounding chimpanzee hepatitis C research, and concludes that claims of the necessity of chimpanzees in historical and future hepatitis C research are exaggerated and unjustifiable, respectively. The chimpanzee model has several major scientific, ethical, economic and practical caveats. It has made a relatively negligible contribution to knowledge of, and tangible progress against, the hepatitis C virus compared to non-chimpanzee research, and must be considered scientifically redundant, given the array of alternative methods of inquiry now available. The continuation of chimpanzee use in hepatitis C research adversely affects scientific progress, as well as chimpanzees and humans in need of treatment. Unfounded claims of its necessity should not discourage changes in public policy regarding the use of chimpanzees in US laboratories.

The successful immune response against hepatitis C nonstructural protein 5A (NS5A) requires heterologous DNA/protein immunization

The aim of this study was to evaluate the immunogenicity of NS5A protein of human hepatitis C virus (HCV) when delivered as naked DNA (NS5A DNA), or recombinant protein (rNS5A). DBA/2J mice received NS5A DNA, rNS5A, or NS5A DNA/rNS5A in different prime-boost combinations with a peptidoglycan Immunomax((R)). The weakest response was induced after rNS5A prime and NS5A DNA boost; rNS5A alone induced an immune response with a strong Th2-component; and NS5A DNA alone, a relatively weak secretion of IL-2 and IFN-gamma. The most efficient was co-injection of NS5A DNA and rNS5A, which induced a significant increase in CD4(+) and CD8(+) T-cell counts, anti-NS5A antibodies, specific T-cell proliferation, and proinflammatory cytokine production in vitro against a broad spectrum of NS5A epitopes. Administration of the mixture of adjuvanted DNA and protein immunogens can be selected as the best regimen for further preclinical HCV-vaccine trials.

Enhancement of DNA Vaccine-induced Immune Responses by Influenza Virus NP Gene

DNA immunization induces B and T cell responses to various pathogens and tumors. However, these responses are known to be relatively weak and often transient. Thus, novel strategies are necessary for enhancing immune responses induced by DNA immunization. Here, we demonstrated that co-immunization of influenza virus nucleoprotein (NP) gene significantly enhances humoral and cell-mediated responses to codelivered antigens in mice. We also found that NP DNA coimmunization augments in vivo proliferation of adoptively transferred antigen-specific CD4 and CD8 T cells, which enhanced protective immunity against tumor challenge. Our results suggest that NP DNA can serve as a novel genetic adjuvant in cocktail DNA vaccination.

Combination of Recombinant Xenogeneic Endoglin DNA and Protein Vaccination Enhances Anti-tumor Effects

The immunization approaches with DNA vaccine priming and subsequent protein or peptide boosting has been widely tested in various models of infectious diseases. However, these approaches are seldom reported in the areas of cancer immunotherapy. In this study we combined endoglin plasmid DNA and recombinant protein as vaccines and used them to prime and boost, simultaneously, as a vaccine strategy. Our results showed that combination of endoglin DNA and protein vaccines could enhance both protective and therapeutic anti-tumor efficacy in both colon carcinoma and Lewis lung carcinoma models. Significant inhibition of tumor angiogenesis was found in the tumor tissues. The titers of autoantibodies against murine endoglin were significantly increased and the antibody levels lasted longer in the mice with combined endoglin DNA and recombinant protein vaccination. CTL response against endoglin-positive HUVECs, but not against endoglin-negative tumor cells was found in the mice combined DNA with protein vaccination. In addition, combination of endoglin DNA and recombinant protein vaccination significantly induced IFN-gamma secreting cells. These observations suggested that a combination of endoglin DNA and recombinant protein immunization as a vaccine strategy was superior to those using endoglin DNA or recombinant protein alone as vaccines.

Evidence for protection against chronic hepatitis C virus infection in chimpanzees by immunization with replicating recombinant vaccinia virus

Given the failures of nonreplicating vaccines against chronic hepatitis C virus (HCV) infection, we hypothesized that a replicating viral vector may provide protective immunity. Four chimpanzees were immunized transdermally twice with recombinant vaccinia viruses (rVV) expressing HCV genes. After challenge with 24 50% chimpanzee infective doses of homologous HCV, the two control animals that had received only the parental VV developed chronic HCV infection. All four immunized animals resolved HCV infection. The difference in the rate of chronicity between the immunized and the control animals was close to statistical significance (P = 0.067). Immunized animals developed vigorous gamma interferon enzyme-linked immunospot responses and moderate proliferative responses. To investigate cross-genotype protection, the immunized recovered chimpanzees were challenged with a pool of six major HCV genotypes. During the acute phase after the multigenotype challenge, all animals had high-titer viremia in which genotype 4 dominated (87%), followed by genotype 5 (13%). However, after fluctuating low-level viremia, the viremia finally turned negative or persisted at very low levels. This study suggests the potential efficacy of replicating recombinant vaccinia virus-based immunization against chronic HCV infection.

Strategies for induction of protective immunity to bovine herpesvirus-1 in newborn calves with maternal antibodies

The objective of this study was to evaluate Th1 promoting strategies for vaccination of neonates against bovine herpesvirus-1 (BHV-1). A plasmid encoding a secreted truncated version of glycoprotein D (tgD) and tgD protein formulated with CpG oligodeoxynucleotide (ODN) effectively primed the immune system of newborn lambs, whereas without CpG ODN the tgD protein was less effective. Furthermore, a heterologous DNA prime-protein/CpG boost induced stronger and more balanced immune responses than either the DNA vaccine or a protein/CpG prime-DNA boost. Three of these strategies were compared as an approach to induce protective immunity in newborn calves with BHV-1-specific maternal antibodies. Whereas the DNA vaccine induced minimal protection, the DNA prime-protein boost resulted in reduced temperature response, weight loss and virus shedding in comparison to the placebo group. Close to complete protection against BHV-1 challenge was elicited in the calves immunized with the protein/CpG formulation, as these animals lost very little weight, had only slightly elevated temperatures and shed almost no virus.

Multimeric HCV E2 protein obtained from Pichia pastoris cells induces a strong immune response in mice

Production of immunogenic hepatitis C virus (HCV) envelope proteins will assist in the future development of preventive or therapeutics applications. Only properly folded monomeric E2 protein is able to bind a putative cellular co-receptor CD81, but this interaction may modulate cell immune function. Recombinant E2 proteins, similar to the native form, but lacking undesirable immunoregulatory features, might be promising components of vaccine candidates against HCV. To obtain E2 suitable for structural as well as functional studies, a recombinant E2 variant (E2680) was produced in Pichia pastoris cells. E2680, comprising amino acids 384 to 680 of the HCV polyprotein, was secreted into the culture supernatant in the N-glycosilated form and was mainly composed of disulfide-linked multimers. Both monomeric and oligomeric forms of E2680 were recognized by conformational-sensitive MAb H53. In addition, antibodies in sera from 70% of HCVpositive patients were reactive against E2680. By immunizing E2680 in BALB/c mice, both a specific cellular immune response and anti-E2680 IgG antibody titers of 1:200,000 were induced. Our data suggest that recombinant E2680 could be useful to successfully induce strong anti-HCV immunity.

Evaluation of T-cell responses to peptides with MHC class I-binding motifs derived from PE_PGRS 33 protein of Mycobacterium tuberculosis

The PE and PPE proteins of Mycobacterium tuberculosis form a source of antigenic variation among different strains of M. tuberculosis. One of the PE_PGRS proteins, Rv1818c, plays a role in the pathogenesis of mycobacterial infection and specifically influences host-cell responses to tuberculosis infection. Although little is known about these two classes of protein, an immunoinformatics approach has indicated the possibility of their participation in eliciting a major histocompatibility complex (MHC) class I-mediated immune response against tuberculosis, as peptides derived from Rv1818c are predicted to bind to MHC class I molecules with high affinity. In the present work, a DNA vaccine was constructed encoding the full-length Rv1818c protein of M. tuberculosis and its immunogenicity was analysed in BALB/c mice. Immunization with Rv1818c DNA induced a strong CD8+ cytotoxic lymphocyte and Th1-type response, with high levels of gamma interferon (IFN-gamma) and low levels of interleukin-4. Two nonameric peptides (Peptide(6-14) and Peptide(385-393)) from Rv1818c were identified by their ability to induce the production of IFN-gamma by CD8+ T cells in mice immunized with Rv1818c DNA. An epitope-specific response was demonstrated by the lysis of peptide-pulsed antigen-presenting cells, release of cytotoxic granules and IFN-gamma production. These peptides bound with high affinity to MHC H-2K(d) and showed low dissociation rates of peptide-MHC complexes. These results could form the basis for testing the identified T-cell epitopes of PE_PGRS proteins in the induction of protective immunity against M. tuberculosis challenge in the mouse model.

Elicitation of strong immune responses by a DNA vaccine expressing a secreted form of hepatitis C virus envelope protein E2 in murine and porcine animal models

AIM: To characterize the immunogenicity of a hepatitis C virus (HCV) E2 DNA vaccine alone or with a protein vaccine boost in murine and porcine animal models.

METHODS: A DNA vaccine expressing a secreted form of HCV E2 protein was constructed and used to vaccinate mice and piglets with or without boosting with a recombinant E2 protein vaccine formulated with CpG ODN and 10% Emulsigen. The immunogenicity of HCV E2 vaccines was analyzed by ELISA for antibody responses, MTT assay for lymphocyte proliferation, ELISPOT for the number of interferon-γ secreting cells, and cytotoxic T lymphocyte assays.

RESULTS: Intradermal injection of E2 DNA vaccine induced strong Th1-like immune responses in mice. In piglets, E2 DNA vaccine elicited moderate and more balanced immune responses. A DNA vaccine prime and protein boost vaccination strategy induced significantly higher E2-specific antibody levels and shifted the immune response towards Th2-like ones in piglets.

CONCLUSION: A DNA vaccine expressing a secreted form of HCV E2 protein elicited E2-specific immune responses in mice and piglets. Recombinant E2 protein vaccination following DNA immunization significantly increased the antibody response in piglets. These HCV E2 vaccines may represent promising hepatitis C vaccine candidates for further investigations.

Priming with DNA encoding E2 and boosting with E2 protein formulated with CpG oligodeoxynucleotides induces strong immune responses and protection from Bovine viral diarrhea virus in cattle

The objective of this study was to develop an optimal vaccination strategy for Bovine viral diarrhea virus (BVDV). The E2 protein of BVDV plays a major protective role against BVDV infection. In order to be able to compare DNA, protein and DNA prime-protein boost regimens, a plasmid was constructed encoding a secreted form of the NADL strain E2 protein (pMASIA-tPAsDeltaE2). Furthermore, a pure secreted recombinant DeltaE2 (rDeltaE2) protein was produced. The rDeltaE2 protein was formulated with a combination of Emulsigen and CpG oligodeoxynucleotide. Groups of calves were immunized with pMASIA-tPAsDeltaE2 or with rDeltaE2, or first with pMASIA-tPAsDeltaE2 and then with rDeltaE2. To evaluate the protection against BVDV, calves were challenged with BVDV strain NY-1 after the last immunization. Although all immunized calves developed humoral and cellular immune responses, the antibody responses in the DNA prime-protein boost group were stronger than those elicited by either the DNA vaccine or the protein vaccine. In particular, E2-specific antibody titres were enhanced significantly after boosting the DeltaE2 DNA-primed calves with rDeltaE2 protein. Moreover, protection against BVDV challenge was obtained in the calves treated with the DNA prime-protein boost vaccination regimen, as shown by a significant reduction in weight loss, viral excretion and lymphopenia, compared with the unvaccinated calves and the animals immunized with the DNA or protein only. These results demonstrate the advantage of a DNA prime-protein boost vaccination approach in an outbred species.

Evaluating replication-defective vesicular stomatitis virus as a vaccine vehicle

We have generated replication-competent (VSV-C/E1/E2) and nonpropagating (VSVDeltaG-C/E1/E2) vesicular stomatitis virus (VSV) contiguously expressing the structural proteins of hepatitis C virus (HCV; core [C] and glycoproteins E1 and E2) and report on their immunogenicity in murine models. VSV-C/E1/E2 and VSVDeltaG-C/E1/E2 expressed high levels of HCV C, E1, and E2, which were authentically posttranslationally processed. Both VSV-expressed HCV E1-E2 glycoproteins were found to form noncovalently linked heterodimers and appeared to be correctly folded, as confirmed by coimmunoprecipitation analysis using conformationally sensitive anti-HCV-E2 monoclonal antibodies (MAbs). Intravenous or intraperitoneal immunization of BALB/c mice with VSV-C/E1/E2 or VSVDeltaG-C/E1/E2 resulted in significant and surprisingly comparable HCV core or E2 antibody responses compared to those of control mice. In addition, both virus types generated HCV C-, E1-, or E2-specific gamma interferon (IFN-gamma)-producing CD8(+) T cells, as determined by enzyme-linked immunospot (ELISPOT) analysis. Mice immunized with VSVDeltaG-C/E1/E2 were also protected against the formation of tumors expressing HCV E2 (CT26-hghE2t) and exhibited CT26-hghE2t-specific IFN-gamma-producing and E2-specific CD8(+) T-cell activity. Finally, recombinant vaccinia virus (vvHCV.S) expressing the HCV structural proteins replicated at significantly lower levels when inoculated into mice immunized with VSV-C/E1/E2 or VSVDeltaG-C/E1/E2, but not with control viruses. Our data therefore illustrate that potentially safer replication-defective VSV can be successfully engineered to express high levels of antigenically authentic HCV glycoproteins. In addition, this strategy may therefore serve in effective vaccine and immunotherapy-based approaches to the treatment of HCV-related disease.

The synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met as a novel adjuvant for DNA vaccine

Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm) is a synthetic peptide known to activate human neutrophils, monocytes and dendritic cells, resulting in the enhancement of superoxide generation, bactericidal activity, chemotactic migration and survival. In this study, we demonstrated that WKYMVm enhanced the surface expression of CD80, but not that of CD40, CD86 and MHC class II, on mouse bone marrow-derived dendritic cells which is one of the essential costimulatory signals for the induction of immune responses. Furthermore, when WKYMVm was codelivered with HIV, HBV and Influenza DNA vaccines, WKYMVm selectively enhanced the vaccine-induced CD8(+) T cell responses in a dose-dependent manner, in terms of IFN-gamma secretion and cytolytic activity. Our results indicate that a synthetic peptide, WKYMVm can function as a novel adjuvant for DNA vaccine.

CD8+-T-cell-dependent control of Trypanosoma cruzi infection in a highly susceptible mouse strain after immunization with recombinant proteins based on amastigote surface protein 2

We previously described that DNA vaccination with the gene encoding amastigote surface protein 2 (ASP-2) protects approximately 65% of highly susceptible A/Sn mice against the lethal Trypanosoma cruzi infection. Here, we explored the possibility that bacterial recombinant proteins of ASP-2 could be used to improve the efficacy of vaccinations. Initially, we compared the protective efficacy of vaccination regimens using either a plasmid DNA, a recombinant protein, or both sequentially (DNA priming and protein boosting). Survival after the challenge was not statistically different among the three mouse groups and ranged from 53.5 to 75%. The fact that immunization with a recombinant protein alone induced protective immunity revealed the possibility that this strategy could be pursued for vaccination. We investigated this possibility by using six different recombinant proteins representing distinct portions of ASP-2. The vaccination of mice with glutathione S-transferase fusion proteins representing amino acids 261 to 500 or 261 to 380 of ASP-2 in the presence of the adjuvants alum and CpG oligodeoxynucleotide 1826 provided remarkable immunity, consistently protecting 100% of the A/Sn mice. Immunity was completely reversed by the in vivo depletion of CD8(+) T cells, but not CD4(+) T cells, and was associated with the presence of CD8(+) T cells specific for an epitope located between amino acids 320 and 327 of ASP-2. We concluded that a relatively simple formulation consisting of a recombinant protein with a selected portion of ASP-2, alum, and CpG oligodeoxynucleotide 1826 might be used to cross-prime strong CD8(+)-T-cell-dependent protective immunity against T. cruzi infection.

Augmented humoral and cellular immune responses to hepatitis B DNA vaccine adsorbed onto cationic microparticles

Plasmid expressing HBV small envelope antigen was formulated with poly(lactide-co-glycolide-acid) (PLGA) and cetyltrimethylammonium bromide (CTAB) to generate highly uniform microparticles. Controlled release of DNA from these microparticles was demonstrated in vitro and in vivo using flow cytometry and confocal laser scanning microscopy with the focus on localization and quantitatively evaluation of antigen-presenting cells (APCs) involved in the expression of target antigen. Compared to mice vaccinated with naked DNA, mice immunized with PLGA-CTAB-DNA microparticles displayed a much higher percentage of CD11c+, HBsAg-expressing APCs in the draining lymph nodes at 24 h and day 14 postinoculation. In addition, a prolonged transcription of plasmid DNA was detected by RT-PCR in mice immunized with the microparticles. A significantly enhanced immunogenicity of PLGA-CTAB-DNA over naked DNA was observed in immunized mice, including higher levels of antibody production, interferon gamma (IFN-gamma) secretion and cytotoxic T lymphocyte activity. Mice immunized with PLGA-CTAB-DNA microparticles also showed greater efficacy of immunoprotection against challenge of transplanted HBsAg-expressing tumor cells. Our data suggest that controlled release of the PLGA-CTAB-DNA microparticles might involve in the mechanisms of its augmented immunogenicity and enhanced immunoprotection.

Needle-free jet injection of a mixture of Japanese encephalitis DNA and protein vaccines: a strategy to effectively enhance immunogenicity of the DNA vaccine in a murine model

Combined immunization with gene-based and protein-based vaccines can increase vaccine effectiveness. We previously demonstrated, using a murine model for Japanese encephalitis (JE), that simultaneous immunization with a DNA vaccine (pcJEME) by the intramuscular route and a protein vaccine consisting of subviral extracellular particles (EPs) by the subcutaneous route provided a synergistic increase in immunogenicities of these vaccines. Here, we investigated a novel immunization protocol consisting of a single inoculation with a mixture of DNA and protein vaccines using a needle-free jet injector. Immunization of ddY mice with 1 microg of pcJEME mixed with 1 microg of EPs or a 1/100 dose of commercial inactivated JE vaccine (JEVAX) induced neutralizing antibody titers of 1:40 to 1:80 (90% plaque reduction) 6 weeks after immunization, whereas immunization with DNA or protein alone only induced low titers (< or =1:10). Co-immunization with pcDNA3, a CpGcontaining vector of the vaccine plasmid, increased immunogenicity of JEVAX to some extent. IgG1/IgG2a isotype profiles supported increased production of EPs in pcJEME-inoculated mice by needle-free injection and an adjuvant effect of the vector on immunogenicity of JEVAX.

Cationic microparticles are a potent delivery system for a HCV DNA vaccine

We initially evaluated in mice the ability of naked DNA encoding intracellular forms of the E1E2 envelope proteins from HCV to induce antibody responses and compared the responses induced with the same plasmid adsorbed onto cationic poly (lactide co-glycolide) (PLG) microparticles. Although naked DNA was only able to induce detectable responses at the 100 microg dose level, making this approach impractical for evaluation in larger animals, PLG/DNA induced detectable responses at 10 microg. In addition, the PLG/DNA microparticles induced significantly enhanced responses to naked DNA when compared at the same dose level. Remarkably, PLG/DNA induced comparable responses to recombinant E1E2 protein adjuvanted with the emulsion MF59. Furthermore, PLG/DNA effectively primed for a booster response with protein immunization, while naked DNA did not. Therefore, PLG/DNA was selected for further evaluation in a non-human primate model. In a study in rhesus macaques, PLG/DNA induced seroconversion in 3/3 animals following three immunizations. Although the antibody responses appeared lower than those induced with recombinant protein adjuvanted with MF59, following a fourth dose, PLG/DNA and protein induced comparable responses. However, a single booster dose of recombinant protein administered to the animals previously immunized with PLG/DNA induced much higher responses. In addition, one of three animals immunized with PLG/DNA showed a cytotoxic T lymphocyte response in peripheral blood lymphocytes. In conclusion, cationic PLG microparticles with adsorbed HCV DNA generates potent immune responses.

Augmented humoral and cellular immune responses of a hepatitis B DNA vaccine encoding HBsAg by protein boosting

Several reports have indicated that combinatorial regimens with DNA and protein vaccines can elicit both strong immune responses, to circumvent the limits of each vaccine. Surprisingly little was known on HBV vaccine. Here, we investigated the immunization effects of several regimens in BALB/c mice. The level of total antibody and isotypes of IgG were determined by ELISA. Cellular immune responses were assayed by measuring the production of cytokines and CTL activity after re-stimulation for 7 days in vitro with tumor cells CT26/S stably expressing HBsAg. The efficacy of immunoprotection against the challenge of transplanted CT26/S was also examined. The regimen involving twice priming pVAX(S) encoding HBsAg and once recombinant HBsAg protein (rHBsAg) boosting, induced strong and homogenous antibody responses. This regimen induced significant stronger responses of interleukin-12 and gamma interferon (IFN-gamma) in splenocytes, and elicited stronger CD8+ CTL responses and greater immunopretectional efficacy than those elicited by immunization with rHBsAg or pVAX(S) alone. Our regimen may thus provide a strategy for developing an improved immunization against HBV and many other pathogens.

Priming with CpG-enriched plasmid and boosting with protein formulated with CpG oligodeoxynucleotides and Quil A induces strong cellular and humoral immune responses to hepatitis C virus NS3

Cell-mediated immune responses to hepatitis C virus (HCV) proteins play a key role in recovery from infection. The NS3 protein of HCV is of special interest, since it is one of the most conserved proteins and NS3-specific immune responses are stronger and more frequently observed in patients resolving the infection than in chronically infected patients. Since these characteristics make NS3 an attractive vaccine candidate, the objective of this study was to optimize NS3-specific immune responses. Results from this group first demonstrated that a plasmid enriched with 24 CpG motifs (pBISIA24-NS3) tends to induce the strongest and most consistent Th1-biased immune response. Subsequently, it was shown that NS3 formulated with CpG oligodeoxynucleotide and Quil A (rNS3+CpG+Quil A) adjuvants induces a balanced immune response in mice, whereas rNS3 combined with either CpG or Quil A elicits a Th2-biased response. To further enhance NS3-specific cell-mediated immune responses, a vaccination regime consisting of priming with pBISIA24-NS3, followed by boosting with rNS3+CpG+Quil A, was explored in mice and pigs. When compared to immunization with rNS3+CpG+Quil A, this regime shifted the immune response to a Th1-type response and, accordingly, enhanced MHC I-restricted killing by cytotoxic T lymphocytes in mice. Although immunization with pBISIA24-NS3 also induced a Th1-biased response, including cytotoxicity in the mice, the humoral response was significantly lower than that induced by the DNA prime-protein boost regime. These results demonstrate the advantage of a DNA prime-protein boost approach in inducing a strong NS3-specific cell-mediated, as well as humoral, immune response, in both inbred laboratory and outbred large animal species.

Protective effects of vaccination with bovine leukemia virus (BLV) Tax DNA against BLV infection in sheep

A DNA vaccination trial was performed on sheep to determine whether vaccination with bovine leukemia virus (BLV) transactivator Tax DNA is effective against BLV infection. Immunization was carried out with cationic liposomes containing the Tax-expressing plasmid DNA and subsequently all sheep were challenged with BLV. BLV titers in peripheral blood mononuclear cell (PBMC) determined by syncytium formation assay and BLV provirus load detected by genomic PCR analysis showed higher levels of virus titers in control sheep than those in Tax-vaccinated sheep. Higher levels of IFN-gamma mRNA expression have been demonstrated in vaccinated sheep after the challenge. These results suggested that Th1 type immune response induced by Tax DNA vaccine inhibited BLV propagation in vaccinated sheep at the early phase of infection.

Induction of hepatitis C virus-specific humoral and cellular immune responses in mice and rhesus by artificial multiple epitopes sequence

The investigation of antigenic epitopes in hepatitis C virus (HCV) protein suggests that a central sequence combined with multiple antigenic epitopes of HCV might be significant as a potential vaccine candidate. This artificial sequence of combined and modified multiple antigenic epitopic peptides (Hc-B2), containing three B and four T cell epitopes, was constructed and expressed in E. coli. Antigen analysis indicated that this peptide antigen was capable of interacting with anti-sera collected from hepatitis C patients infected by three genotypes of HCV from three different geographic areas of China, respectively. The immunological analysis of this peptide antigen in mice and rhesus suggested that its immunogenicity was effective. However, a complete evaluation of this peptide could not be made as an effective animal model for HCV infection (such as in the chimpanzee) was not available for this study.

Sub-fragments of the envelope gene are highly protective against the Japanese encephalitis virus lethal infection in DNA priming—protein boosting immunization strategies

The envelope (E) gene of Japanese encephalitis virus (JEV) plays a major protective role against JEV infection. In order to locate the part of E gene that is responsible for this protection, an N-terminal fragment EA (nucleotide number 933-1877 bp of JEV genome) and a C-terminal fragment EB (nucleotide number 1851-2330 bp of JEV genome) from E gene were prepared. Both of these fragments were used in the form of recombinant proteins (rEA and rEB) and plasmid DNA (pEA, pM15EA and pEB) for immunizations. Recombinant EA protein (rEA) was previously found to be non-protective because it was expressed in an insoluble form. Plasmid EA (pEA) was also found to be non-protective unless it is preceded by a 15 mer signal peptide derived from the very C-terminal of the membrane gene (M) of JEV to form pM15EA plasmid indicating the importance of the signal peptide in the expression of EA immunogenicity. Although pM15EA and pEB are both immunogenic and protective against JEV lethal infection, the protection by both fragments however is not optimal. Even when pM15EA and pEB were used together for immunization, maximum protection as those induced by control vaccine was not achieved. However, if individual fragments (EA or EB) were used in a DNA priming-protein boosting or protein priming-DNA boosting strategy, high levels of protection were achieved by both fragments. This was especially true for EA fragment where the level of protection against JEV lethal infection was equal to that induced by commercially available vaccine alone. The protection correlated very well with the neutralizing antibody titers and the T helper cell involved in this process in mainly the Th1 type.

Efficient induction of T helper 1 CD4+ T-cell responses to hepatitis C virus core and E2 by a DNA prime-adenovirus boost

Hepatitis C virus (HCV) is an important causative agent of liver disease, but currently there is no available prophylactic vaccine against HCV infection. Here, we investigated the HCV E2- and core-specific T-cell responses induced by DNA (D) and/or recombinant adenovirus (A) vaccines. In single (D versus A) or double immunizations (D-D versus A-A), the recombinant adenovirus vaccines induced higher levels of IFN-gamma secreting T-cell response and cytotoxic T lymphocytes (CTL) response than the DNA vaccines. However, a heterologous (D-A) regimen elicited the highest level of T helper 1 (Th1) CD4(+) T-cell responses. Furthermore, three E2-specific CTL epitopes were mapped using a peptide pool spanning the E2 protein sequence (a.a. 384-713) in BALB/c mice, and one of these (E2 405-414: SGPSQKIQLV) was shown to be immunodominant. Interestingly, no significant differences were found in the repertoire of E2-specific T-cell responses or in the immunodominance hierarchy of the three epitopes induced by D-D, D-A, A-A, and A-D, indicating that the breadth and hierarchy of T-cell responses is independent of these different vaccination regimens. In conclusion, the heterologous DNA prime-recombinant adenovirus boost regimen described offers an efficient promising strategy for the development of an effective T-cell-based HCV vaccine.

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Construction and expression of chrimeid plasmid pHCV-IgFc

AIM

To construct a recombinant cherimal plasmid of HCV-Fc that can express HCV core protein and IgG Fc.

METHODS

The HCV core gene derived from the plasmid pBRTM/HCV1-3011 by using polymerase chain reaction (PCR) was inserted into the backward position of cytomegalovirus (CMV) immediate early promotor element of Fc plasmid (pIgFc), then the recombinant plasmid pHCV-IgFc was obtained.

RESULTS

The insert DNA of pHCV-IgFc was HCV core and Fc gene conformed by endonuclease, PCR and sequencing. HCV core gene and Fc gene expressed transiently with Lipofectamine 2000 coated in human hepatoblastoma 7721 cells, which was conformed by immunofluorescence.

CONCLUSION

Recombinant cherimal plasmid vector pHCV-IgFc can express HCV core and Fc gene transiently in 7721 cells. It may be useful in transfection of dendritic cells and development into dendritic cell vaccince.

A DNA-priming protein-boosting regimen significantly improves type 1 immune response but not protective immunity to Trypanosoma cruzi infection in a highly susceptible mouse strain

BALB/c or C57Bl/6 mice immunized with plasmids containing Trypanosoma cruzi genes developed specific immune responses and protective immunity against lethal parasitic infection. In contrast, in the highly susceptible mouse strain A/Sn, DNA vaccination reduced the peak parasitemia but promoted limited mouse survival after challenge. In the present study, we tested whether the immunogenicity and protective efficacy of vaccination could be improved by combining DNA and recombinant protein immunization regimens. A/Sn mice immunized with plasmid p154/13 which harbours the gene encoding Trypanosoma cruzi trans-sialidase developed a predominant type 1 immune response. In contrast, immunization with the recombinant Trypanosoma cruzi trans-sialidase protein adsorbed to alum generated a typical type 2 immune response. Simultaneous administration of both p154/13 and recombinant Trypanosoma cruzi trans-sialidase protein also led to a predominant type 2 immune response. Sequential immunization consisting of two priming doses of p154/13 followed by booster injections with recombinant Trypanosoma cruzi trans-sialidase protein significantly improved specific type 1 immune response, as revealed by a drastic reduction of the serum IgG1/IgG2a ratio and by an increase in the in vitro interferon-gamma secretion by CD4 T cells. Our observations confirm and extend previous data showing that a DNA-priming protein-boosting regimen might be a general strategy to enhance type 1 immune response to DNA vaccines. Upon challenge with Trypanosoma cruzi, no improvement in protective immunity was observed in mice immunized with the DNA-priming protein-boosting regimen when compared to animals that received DNA only. Therefore, our results suggest that in this experimental model there is no correlation between the magnitude of type 1 immune response and protective immunity against Trypanosoma cruzi infection.

Evaluation of protection against Chlamydophila abortus challenge after DNA immunization with the major outer-membrane protein-encoding gene in pregnant and non-pregnant mice

The protective effect of DNA vaccination with the gene encoding the major outer-membrane protein (MOMP) of Chlamydophila abortus has been studied in non-pregnant and pregnant mouse models after chlamydial challenge. OF1 outbred mice were vaccinated intramuscularly three times every 3 weeks, mated and challenged with C. abortus 2 weeks after the last injection of DNA. In non-pregnant mice, the MOMP DNA vaccine elicited a specific humoral response with predominantly IgG2a antibodies, suggesting a Th1-type immune response. The induced antibodies showed no in vitro neutralizing effect on C. abortus infectivity. Moreover, immunization with the momp gene showed no reduction in the mean splenic bacterial counts of non-pregnant or pregnant mice or in the mean placental bacterial counts of pregnant mice after the C. abortus challenge. Nevertheless, the MOMP DNA immunization induced a non-specific and partial protection in fetuses against challenge.

Immunization with influenza virus hemagglutinin globular region containing the receptor-binding pocket

The globular region of hemagglutinin (residues 91-261) membrane glycoprotein of influenza virus that encompasses the binding zone to the oligosaccharide receptor of target cells has been cloned by reverse transcriptase-polymerase chain reaction (RT-PCR). This protein segment (denoted HA91-261 peptide) induced significant immune response in mice. The serum antibodies and lung homogenates from the immunized mice cross-reacted with native virus particles. The cellular immunity was manifested by proliferative splenocyte responses and cytokine release indicating T helper type 1 activity. The plasmid DNA containing this segment (denoted pHA91-261) provoked, in addition, a significant cytotoxic T lymphocyte (CTL) response, whereas the HA91-261 protein fragment led to no such response. Both the DNA and the protein fragment of HA91-261 induced significant protection against viral challenge, although the immune response they induce might be along different pathways. Interestingly, the combined DNA priming-protein boosting immunization regimen did not induce protection against viral challenges even though it led to significant humoral immune responses similar to that induced by the peptide vaccine.

DNA-based immunotherapy: potential for treatment of chronic viral hepatitis?

Persistent HBV and HCV infection represent major causes of chronic liver disease with a high risk of progression to liver cirrhosis and hepatocellular carcinoma (HCC). Conventional protein-based vaccines are highly efficacious in preventing HBV infection; whereas in therapeutic settings with chronically infected patients, results have been disappointing. Prophylactic vaccination against HCV infection has not yet been achieved due to many impediments including frequent spontaneous mutations of the virus with escape from immune system control. Using animal models it has been demonstrated that DNA-based immunisation strategies may overcome this problem because of their potential to induce immunity against multiple viral epitopes. DNA-based vaccines mimic the effect of live attenuated viral vaccines, eliciting cell mediated immunity in addition to inducing humoral responses. Efficacy may further be improved by addition of DNA encoding immunomodulatory cytokines and more recently, direct genetic modulation of antigen-presenting cells, such as dendritic cells (DC), has been shown to increase antigen-specific immune responses. This review focuses on immunological aspects of chronic HBV and HCV infection and on the potential of DNA- and DC-based vaccines for the treatment of chronic viral hepatitis.

Nucleic acid vaccines: tasks and tactics

There are no adequate vaccines against some of the new or reemerged infectious scourges such as HIV and TB. They may require strong and enduring cell-mediated immunity to be elicited. This is quite a task, as the only known basis of protection by current commercial vaccines is antibody. As DNA or RNA vaccines may induce both cell-mediated and humoral immunity, great interest has been shown in them. However, doubt remains whether their efficacy will suffice for their clinical realization. We look at the various tactics to increase the potency of nucleic acid vaccines and divided them broadly under those affecting delivery and those affecting immune induction. For delivery, we have considered ways of improving uptake and the use of bacterial, replicon or viral vectors. For immune induction, we considered aspects of immunostimulatory CpG motifs, coinjection of cytokines or costimulators and alterations of the antigen, its cellular localization and its anatomical localization including the use of ligand-targeting to lymphoid tissue. We also thought that mucosal application of DNA deserved a separate section. In this review, we have taken the liberty to discuss these enhancement methods, whenever possible, in the context of the underlying mechanisms that might argue for or against these strategies.

DNA vaccines for hepatitis C virus

Hepatitis C virus is an RNA encoded virus of the Flaviviridae family. In most cases, infections develop into a chronic carrier stage that can result in the onset of cirrhosis and hepatocellular carcinoma over a 20- to 30-year period. Because existing therapies are still of limited benefit and expensive, the development of a vaccine represents a priority to prevent further spreading of the infection. Immune correlates of protection remain poorly defined although increasing evidence suggests that both humoral and cellular immune responses are likely to contribute to protection and/or neutralization of the virus. Current DNA-based vaccines, while capable of generating the latter, appear limited in their capacity to induce a strong and long-lasting antibody response.

Live and killed rhabdovirus-based vectors as potential hepatitis C vaccines

A highly attenuated, recombinant rabies virus (RV) vaccine strain-based vector was utilized as a new immunization strategy to induce humoral and cellular responses against hepatitis C (HCV) glycoprotein E2. We showed previously that RV-based vectors are able to induce strong immune responses against human immunodeficiency virus type I (HIV-1) antigens. Here we constructed and characterized three replication-competent RV-based vectors expressing either both HCV envelope proteins E1 and E2 or a modified version of E2 which lacks 85 amino acids of its carboxy terminus and contains the human CD4 transmembrane domain and the CD4 or RV glycoprotein cytoplasmic domain. All three constructs stably expressed the respective protein(s) as indicated by Western blotting and immunostaining. Moreover, surface expression of HCV E2 resulted in efficient incorporation of the HCV envelope protein regardless of the presence of the RV G cytoplasmic domain, which was described previously as a requirement for incorporation of foreign glycoproteins into RV particles. Killed and purified RV virions containing HCV E2 were highly immunogenic in mice and also proved useful as a diagnostic tool, as indicated by a specific reaction with sera from HCV-infected patients. In addition, RV vaccine vehicles were able to induce cellular responses against HCV E2. These results further suggest that recombinant RVs are potentially useful vaccine vectors against important human viral diseases.

Immunopathogenesis of hepatitis C virus infection

Hepatitis C virus, a recently identified member of the family Flaviviridae, is an important cause of chronic viral hepatitis and cirrhosis. There are similarities in the nature of the immune response to this pathogen with immunity in other flavivirus and hepatotropic virus infections, such as hepatitis B. However, the high rate of viral persistence after primary hepatitis C infection, and the observation that neutralizing antibodies are not protective, would suggest that there are a number of important differences between hepatitis C, other flaviviruses, and hepatitis B. The phenomenon of quasispecies evolution and other viral factors have been proposed to contribute to immune evasion by hepatitis C virus. In the face of established persistent infection, virus-specific cytotoxic T lymphocytes may exert some control over viral replication. However, these same effectors may also be responsible for the progressive liver damage characteristic of chronic hepatitis C infection. The nature of protective immunity, including the role of innate immune responses early after hepatitis C exposure, remains to be defined.

Identification of the epitopes on HCV core protein recognized by HLA-A2 restricted cytotoxic T lymphocytes

AIM

To identify hepatitis C virus(HCV) core protein epitopes recognized by HLA-A2 restricted cytotoxic T lymphocyte (CTL).

METHODS

Utilizing the method of computer prediction followed by a 4h(51)Cr release assay confirmation.

RESULTS

The results showed that peripheral blood mononuclear cells (PBMC) obtained from two HLA-A2 positive donors who were infected with HCV could lyse autologous target cells labeled with peptide "ALAHGVRAL (core 150-158)". The rates of specific lysis of the cells from the two donors were 37.5% and 15.8%, respectively. Blocking of the CTL response with anti-CD4 mAb caused no significant decrease of the specific lysis. But blocking of CTL response with anti-CD8 mAb could abolish the lysis.

CONCLUSION

The peptide (core 150-158) is the candidate epitope recognized by HLAA2 restricted CTL.

Update on antiviral DNA vaccine research (1998-2000)

DNA vaccines can induce protective cellular and humoral immune responses and have therefore been used during the last decade to develop vaccines against a variety of different pathogens. Because current antiviral vaccines predominantly generate humoral immunity, DNA immunization may be especially useful to provide long-term protection against viral diseases that also require cellular immunity (e.g. HIV). A significant number of articles published in the field of DNA vaccines are dealing with viral diseases, reflecting the need for better and alternative vaccination strategies against viruses. The success of DNA immunization depends on a variety of parameters (e.g. type of antigen, method of application and usage of adjuvants). Therefore, different strategies have been explored to modulate the induced immune response with respect to the requirements necessary to protect against a specific pathogen (e.g. induction of mucosal or cell-mediated immunity). The following article provides an update on different aspects of antiviral DNA vaccine research that have previously been reviewed by others.

Improved immunogenicity and protective efficacy of a tuberculosis DNA vaccine encoding Ag85 by protein boosting

C57BL/6 mice were vaccinated with plasmid DNA encoding Ag85 from Mycobacterium tuberculosis, with Ag85 protein in adjuvant, or with a combined DNA prime-protein boost regimen. While DNA immunization, as previously described, induced robust Th1-type cytokine responses, protein-in-adjuvant vaccination elicited very poor cytokine responses, which were 10-fold lower than those observed with DNA immunization alone. Injection of Ag85 DNA-primed mice with 30 to 100 microg of purified Ag85 protein in adjuvant increased the interleukin-2 and gamma interferon (IFN-gamma) response in spleen two- to fourfold. Further, intracellular cytokine analysis by flow cytometry also showed an increase in IFN-gamma-producing CD4(+) T cells in DNA-primed-protein-boosted animals, compared to those that received only the DNA vaccination. Moreover, these responses appeared to be better sustained over time. Antibodies were readily produced by all three methods of immunization but were exclusively of the immunoglobulin G1 (IgG1) isotype following protein immunization in adjuvant and preferentially of the IgG2a isotype following DNA and DNA prime-protein boost vaccination. Finally, protein boosting increased the protective efficacy of the DNA vaccine against an intravenous M. tuberculosis H37Rv challenge infection, as measured by CFU or relative light unit counts in lungs 1 and 2 months after infection. The capacity of exogenously given protein to boost the DNA-primed vaccination effect underlines the dominant role of Th1-type CD4(+) helper T cells in mediating protection.

Effects of a hexameric deoxyriboguanosine run conjugation into CpG oligodeoxynucleotides on their immunostimulatory potentials

CpG oligodeoxynucleotides (ODNs) are promising immunomodulatory agents for treating human diseases and vaccine development. Phosphodiester CpG ODNs were demonstrated to have poor immunostimulatory potentials for cytokine production. However, the conjugation of consecutive deoxyriboguanosine residues, called a dG run, at the 3' terminus of phosphodiester CpG ODNs significantly enhanced TNF-alpha and IL-12 production from mouse splenic dendritic cells (DCs). The optimal induction of cytokine production was achieved by the addition of a hexameric dG (dG6) run. In contrast, the existence of a dG6 run either at the 5' terminus of phosphodiester CpG ODNs or at the 3' terminus of phosphorothioate CpG ODNs diminished CpG-mediated cytokine induction, suggesting that the effects of a dG run depend on its location and the chemical property of the ODN backbone, respectively. In addition, we provided the evidence that the conjugation of a dG6 run caused the structural transformation of CpG ODNs, which facilitates their targeting into mouse APCs such as splenic DCs, B cells, and peritoneal macrophages with a scavenger receptor type A ligand specificity. Among primary APCs, DCs were the most potent for CpG ODN-mediated IL-12 production. Furthermore, we demonstrated that the conjugation of a dG6 run into the 3' terminus of phosphodiester CpG ODNs was crucial for their ability to generate Th1 immunity in vivo. Thus, the conjugation of a dG6 run into phosphodiester CpG ODNs would be an alternative way to optimize their immunostimulatory potentials in vitro and in vivo.