Epstein-Barr Virus Vaccine Research Articles

Epstein-Barr virus vaccine development: a lytic and latent protein cocktail

Epstein-Barr Virus (EBV) is the causative agent of acute infectious mononucleosis and associates with malignancies such as Burkitt lymphoma, nasopharyngeal carcinoma, and non-Hodgkin's lymphoma. Additionally, EBV is responsible for B-lymphoproliferative disease in the context of HIV-infection, genetic immunodeficiencies and organ/stem-cell transplantation. Here we discuss past and current efforts to design an EBV vaccine. We further describe preliminary studies of a novel cocktail vaccine expressing both lytic and latent EBV proteins. Specifically, a tetrameric vaccinia virus (VV) -based vaccine was formulated to express the EBV lytic proteins gp350 and gp110, and the latent proteins EBNA-2 and EBNA-3C. In a proof-of-concept study, mice were vaccinated with the individual or mixed VV. Each of the passenger genes was expressed in vivo at levels sufficient to elicit binding antibody responses. Neutralizing gp350-specific antibodies were also elicited, as were EBV-specific T-cell responses, following inoculation of mice with the single or mixed VV. Results encourage further development of the cocktail vaccine strategy as a potentially powerful weapon against EBV infection and disease in humans.

Recombinant gp350 Vaccine for Infectious Mononucleosis: A Phase 2, Randomized, Double‐Blind, Placebo‐Controlled Trial to Evaluate the Safety, Immunogenicity, and Efficacy of an Epstein‐Barr Virus Vaccine in Healthy Young Adults

To date, there is no commercially available vaccine to prevent infectious mononucleosis, a disease frequently induced by Epstein-Barr virus (EBV) infection in adolescents or adults devoid of preexisting immunity to the virus. A total of 181 EBV-seronegative, healthy, young adult volunteers were randomized in a double-blind fashion to receive either placebo or a recombinant EBV subunit glycoprotein 350 (gp350)/aluminum hydroxide and 3-O-desacyl-4'-monophosphoryl lipid A (AS04) candidate vaccine in a 3-dose regimen. The vaccine had demonstrable efficacy (mean efficacy rate, 78.0% [95% confidence interval {CI}, 1.0%-96.0%]) in preventing the development of infectious mononucleosis induced by EBV infection, but it had no efficacy in preventing asymptomatic EBV infection. One month after receipt of the final dose of gp350 vaccine, 98.7% of subjects showed seroconversion to anti-gp350 antibodies (95% CI, 85.5%-97.9%), and they remained anti-gp350 antibody positive for >18 months. Furthermore, there were no concerns regarding the safety or reactogenicity of the gp350/AS04 vaccine. These data support the clinical feasibility of using an EBV vaccine to prevent infectious mononucleosis. ClinicalTrials.gov identifier: NCT00430534.

Phase I/II studies to evaluate safety and immunogenicity of a recombinant gp350 Epstein–Barr virus vaccine in healthy adults

Two double-blind randomised controlled studies (phase I and I/II) were performed to assess for the first time the safety and immunogenicity of a recombinant subunit gp350 Epstein-Barr virus (EBV) vaccine in 148 healthy adult volunteers. All candidate vaccine formulations had a good safety profile and were well tolerated, with the incidence of solicited and unsolicited symptoms within a clinically acceptable range. One serious adverse event was reported in the phase I trial which was considered to be of suspected relationship to vaccination. The gp350 vaccine formulations were immunogenic and induced gp350-specific antibody responses (including neutralising antibodies).

Epstein-Barr Virus (Infectious Disease and Therapy)

Epstein-Barr virus (EBV) was the first recognized human tumor virus, but it is not the causative agent for the tumor in which it was discovered, Burkitt lymphoma. Common to all Burkitt lymphomas, endemic or sporadic, are distinctive chromosomal translocations that reactivate expression of the c-myc protooncogene and comprise the primary oncogenic mechanism. EBV is at least a contributory cofactor in endemic Burkitt lymphoma, but the virus is detected in <20% of sporadic cases in the United States. EBV does cause infectious mononucleosis, hairy leukoplakia, and B-lymphoproliferative neoplasms in immunocompromised persons. In addition, the early and utterly consistent presence of monoclonal EBV episomes in nasopharyngeal carcinoma worldwide suggests a crucial role for the virus in that neoplasm. While tantalizing, associations with other diseases, well reviewed in this volume, are inconsistent and suggest that the virus may have another role beyond the etiologic, namely, by affecting the phenotype of already existing tumor cells and possibly propelling tumor progression. This book is assembled mostly from a clinical perspective, and useful chapters on several of the EBV diseases bring together information not easily found elsewhere. Well-informed chapters on the virology and epidemiology of EBV infection are also included. One of the editors (whose list of milestones displays the clinical emphasis of the book) has provided a nice historical summary. As is usual with such compilations, the editors leave it to the contributors to speak for themselves, and the quality of the chapters is uneven. Some fall short in citation of primary sources or favor the author's view rather than one that weighs all the evidence. Withal it is a useful book, and having the less often discussed associations such as T-cell lymphomas and leiomyosarcomas assigned a place alongside authoritative chapters on the classic associations, nasopharyngeal carcinoma and Burkitt lymphoma, is convenient. The volume ends with a chapter on an EBV vaccine, which remains elusive after many years. In contrast, the penultimate chapter includes a brief summary of some successes with adoptive immunotherapy for posttransplant lymphoproliferative disease, which is generally refractory to conventional treatment. This volume is worth having for the cross-section of knowledge and developments in the EBV field it presents.

Dendritic cells initiate immune control of epstein-barr virus transformation of B lymphocytes in vitro.

The initiation of cell-mediated immunity to Epstein-Barr virus (EBV) has been analyzed with cells from EBV-seronegative blood donors in culture. The addition of dendritic cells (DCs) is essential to prime naive T cells that recognize EBV-latent antigens in enzyme-linked immunospot assays for interferon γ secretion and eradicate transformed B cells in regression assays. In contrast, DCs are not required to control the outgrowth of EBV-transformed B lymphocytes from seropositive donors. Enriched CD4+ and CD8+ T cells mediate regression of EBV-transformed cells in seronegative and seropositive donors, but the kinetics of T-dependent regression occurs with much greater speed with seropositives. EBV infection of DCs cannot be detected by reverse transcription–polymerase chain reaction with primers specific for mRNA for the EBNA1 U and K exons. Instead, DCs capture B cell debris and generate T cells specific for EBV latency antigens. We suggest that the cross-presentation of EBV-latent antigens from infected B cells by DCs is required for the initiation of EBV-specific immune control in vivo and that future EBV vaccine strategies should target viral antigens to DCs.

A promising synthetic peptide for the design of an Epstein-Barr virus vaccine

A promising synthetic peptide for the design of an Epstein-Barr virus vaccine

Contribution of HLA Class I Allele Expression to CD8+ T‐Cell Responses against Epstein–Barr Virus

Most immune responses to viral infections involve CD8+ T cells recognizing viral peptides of typically 9-10 amino acids in the groove of major histocompatibility complex (MHC) class I. Importantly, CD8+ T-cell responses appear to focus on few viral epitopes, a phenomenon termed immunodominance. While the understanding of this phenomenon has been based largely on experimental mice models, it is imperative to evaluate its contribution in humans, as the design of peptide-based vaccines may be influenced by immunodomination. Here, we present evidence that immunodominance can be detected among Epstein-Barr virus (EBV) epitopes associated with two of the most frequent class I alleles in Western Europe, human leucocyte antigen (HLA)-A2 and HLA-B7. CD8+ T-cell responses to HLA-A2-associated EBV epitopes were significantly reduced in individuals coexpressing HLA-B7. The impairment of HLA-A2-associated responses correlated with a dominant response to an HLA-B7 epitope. The data demonstrate a hierarchy in the human cellular immune response to immunodominant EBV epitopes presented by separate HLA class I alleles. This may have implications for EBV vaccine development as well as for the interpretation of isolated analysis of immunodominant responses to EBV.

Contrasting Epstein–Barr virus-specific cytotoxic T cell responses to HLA A2-restricted epitopes in humans and HLA transgenic mice: implications for vaccine design

This study investigates the hierarchy of cytotoxic T cell (CTL) responses to twelve HLA A2-restricted epitopes from the latent, lytic and structural proteins of Epstein–Barr virus (EBV) in acute infectious mononucleosis and in healthy seropositive donors and the relative immunogenecity of these epitopes in transgenic mice. Responses to the lytic epitope were uniformly strong in all healthy seropositive individuals and acute infectious mononucleosis donors while moderate or low responses were observed to the latent and structural epitopes, respectively in both groups studied. In contrast, when HLA A2/Kb transgenic mice were immunised with these peptide epitopes, CTL responses were observed to all epitopes with a maximal response to the epitopes within the structural proteins and low to moderate responses to the latent epitopes. This hierarchy of CTL responses in mice was also reflected in an MHC stabilisation analysis. These contrasting CTL responses in humans following natural infection compared to the immunogenicity of these epitopes and their ability to stabilise MHC may need to be considered when designing an EBV vaccine.

The major Epstein-Barr virus (EBV) envelope glycoprotein gp340 when incorporated into Iscoms primes cytotoxic T-cell responses directed against EBV lymphoblastoid cell lines

A recombinant form of the EBV envelope glycoprotein and vaccine candidate gp340, lacking its hydrophobic transmembrane region, was incorporated into Iscoms after coupling to phosphatidyl ethanolamine via carbohydrate residues. Coupling by partial oxidation of gp340 carbohydrate with sodium periodate partly denatured the incorporated gp340 as indicated by its reduced reactivity with monoclonal antibodies that recognise the major neutralising epitope. Immunisation of cottontop tamarins with these Iscoms elicited antibody responses to gp340, but these antibodies only poorly recognised the major neutralising epitope in a competition ELISA and were unable to neutralise EBV in vitro. Despite the lack of neutralising antibody, immunisation with these Iscoms primed significant in vitro proliferative responses to soluble gp340 in lymphocytes from the draining lymph nodes and spleen. T-cell lines were raised from both immunised and control animals by in vitro stimulation of peripheral blood lymphocytes or spleen cells with autologous EBV-transformed lymphoblastoid cell lines. The T-cell lines from control animals had higher numbers of CD4+ T-cells than CD8+ T-cells and were not cytotoxic for autologous lymphoblastoid cell lines (LCL). In contrast the lines from immunised animals contained more CD8+ T-cells than CD4+ T-cells and had marked cytotoxicity for autologous LCL.

New antigen presentation system based on retroviral-like particles; baculovirus or Semliki-Forest virus-based vector virus-like particle expression in host cell for e.g. HIV virus, Epstein-Barr virus and herpes virus vaccine generation : Wolf H World 9630 523; 3 October 1996

New antigen presentation system based on retroviral-like particles; baculovirus or Semliki-Forest virus-based vector virus-like particle expression in host cell for e.g. HIV virus, Epstein-Barr virus and herpes virus vaccine generation : Wolf H World 9630 523; 3 October 1996

Issues related to development of Epstein-Barr virus vaccines.

Issues related to development of Epstein-Barr virus vaccines.

Major Histocompatibility Complex Class I-Restricted Cytotoxic T Lymphocyte Responses to Epstein-Barr Virus in Children

Epstein-Barr virus (EBV)-specific cytotoxic T lymphocyte (CTL) responses were evaluated in 9 children aged 20-35 months. Autologous EBV-transformed B lymphoblastoid cell lines were used to restimulate EBV-specific memory CTL precursors in vitro. Recognition of individual EBV gene products by bulk CTL lines was evaluated by combining CTL lines with B cell blasts infected with recombinant vaccinia constructs expressing single latent genes. CTL lines from all 9 children recognized one or more EBV latent gene products. All children demonstrated CTL responses against one or more EBV nuclear antigen 3 proteins (EBNA3A, 3B, 3C), and EBNA3C was recognized most frequently. The striking similarity between EBV-specific CTL responses described here in young children and those reported for adults suggests that the EBNA3 family of proteins and latent membrane protein 2A should be considered for inclusion in candidate EBV vaccines.

Peptide-based EBV vaccine in phase I trial

The first clinical study of a synthetic peptide-based vaccine against the Epstein-Barr virus (EBV) is now underway. Researchers are hopeful that the vaccine, which contains a cytotoxic T-lymphocyte (CTL) epitope, may protect against EBV immunopathology.Inpharma spoke to Dr Andreas Suhrbier, from the Queensland Institute of Medical Research, Brisbane, Australia, about the current phase I trial and the potential applications for an EBV vaccine in protecting against infectious mononucleosis (glandular fever) and the development of post-transplant lymphoproliferative disease (PTLD).

Conformation-dependent recognition of baculovirus-expressed Epstein-Barr virus gp350 by a panel of monoclonal antibodies.

The Epstein-Barr virus (EBV) major membrane protein, gp350, induces antibodies that neutralize virus infectivity in vitro and is a potential candidate for an EBV vaccine. Full-length EBV gp350 and five protein fragments, encompassing the entire protein sequence, were generated in a baculovirus expression system. The recombinant proteins were analysed using a panel of 14 monoclonal antibodies (MAbs) (13 prepared against native gp350 derived from virus-producing cells and one prepared against an Escherichia coli recombinant protein). All 14 MAbs, including a virus-neutralizing antibody, reacted with the full-length recombinant gp350 in a dot blot immunoassay, but only four of the 14 MAbs reacted with polypeptides expressed by the five subclones, indicating that the full-length protein, but not the protein fragments, was antigenically similar to native gp350. Treatment of the six recombinant proteins with peptide-N-glycosidase F (PNGase F) indicated that the full-length gp350 protein and the N-terminal fragment were glycosylated and that the four internally initiated polypeptides were not glycosylated. PNGase F treatment of the full-length glycosylated gp350 did not eliminate its reactivity with all of the 10 MAbs examined (including the neutralizing MAb) in a dot blot immunoassay; however, denatured glycosylated gp350 lost reactivity with all but four of the 14 MAbs when analysed by either dot blot or Western blot immunoassay. The data suggest that conformational epitopes are more important in recognition of gp350 by this panel of MAbs than glycosylation sites, and that the epitope on gp350 recognized by the neutralizing MAb is conformation- and not glycosylation-dependent.

Localization of Epstein-Barr virus cytotoxic T cell epitopes using recombinant vaccinia: implications for vaccine development.

There is considerable interest in designing an effective vaccine to the ubiquitous Epstein-Barr virus (EBV). An important role for EBV-specific cytotoxic T lymphocytes (CTLs) in eliminating virus-infected cells is well established. Limited studies using a small number of immune donors have defined target epitopes within the latent antigens of EBV. The present study provides an extensive analysis of the distribution of class I-restricted CTL epitopes within EBV-encoded proteins. Using recombinant vaccinia encoding individual EBV latent antigens (Epstein-Barr nuclear antigen [EBNA] 1, 2, 3A, 3B, 3C, LP, and LMP 1), we have successfully localized target epitopes recognized by CTL clones from a panel of 14 EBV-immune donors. Of the 20 CTL epitopes localized, five were defined at the peptide level. Although CTL clones specific for nine epitopes recognized both type 1 and type 2 transformants, a significant number of epitopes (7/16 epitopes for which EBV type specificity was determined) were detected only on type 1 EBV transformants. Vaccinia recombinants encoding EBNA 3A and EBNA 3C were recognized more frequently than any other vaccinia recombinants used in this study, while no CTL epitopes were localized in EBNA 1. Surprisingly, epitope specificity for a large number of EBV-specific CTL clones could not be localized, although vaccinia recombinants used in this study encoded most of the latent antigens of EBV. These results suggest that any EBV vaccine based on CTL epitopes designed to provide widespread protection will need to include not only latent antigen sequences but also other regions of the genome. The apparent inability of human CTLs to recognize EBNA 1 as a target antigen, often the only latent antigen expressed in Burkitt's lymphoma and nasopharyngeal carcinoma, suggests that EBV-specific CTL control of these tumors will not be feasible unless the down-regulation of latent antigens can be reversed.

Protective immunization against Epstein-Barr virus-induced disease in cottontop tamarins using the virus envelope glycoprotein gp340 produced from a bovine papillomavirus expression vector.

Inoculation with Epstein-Barr virus (EBV) induces malignant lymphomas in the cottontop tamarin (Saguinus oedipus oedipus). This provides an experimental animal model for assessing the efficacy of candidate EBV vaccines which are intended to reduce the incidence of human tumours associated with EBV infection. Previous work has shown that experimental vaccines based on the major virus envelope glycoprotein gp340 prepared from the membranes of EBV-infected cells are effective in protecting cottontop tamarins against EBV-induced disease. However, not all purified gp340 preparations induce protective immunity against EBV lymphoma in the tamarin. In this work, cottontop tamarins were immunized with recombinant gp340, produced using a bovine papillomavirus (BPV) expression vector, and a threonyl muramyl dipeptide adjuvant formulation. Although the recombinant-derived gp340 lacked the membrane anchor sequence of authentic gp340 and was expressed in mouse cells, it was immunogenic and induced virus-neutralizing antibodies. Healthy vaccinated tamarins were protected against EBV-induced disease. The demonstration that a recombinant gp340 product is able to elicit protective immunity in the cottontop tamarin is a significant step in the development of an EBV vaccine because previously it had not been clear whether a recombinant product would have the exact tertiary structure, including the necessary carbohydrate components, to induce protective immunity. A recombinant gp340 vaccine offers various advantages over production of the authentic molecule by laborious biochemical separation, including lower cost and the absence of potentially oncogenic EBV DNA. Therefore, recombinant gp340 produced using the BPV expression vector is suitable for development as a candidate EBV vaccine for a human Phase I trial and beyond.

Mapping of B-cell epitopes on the polypeptide chain of the Epstein-Barr virus major envelope glycoprotein and candidate vaccine molecule gp340.

The Epstein-Barr virus (EBV) major envelope glycoprotein gp340 is the subject of current efforts to develop an EBV subunit vaccine. The importance of gp340-specific humoral immunity has been highlighted by studies of natural infection in humans and gp340 immunization of experimental animals. The former studies have demonstrated the presence of gp340-specific serum antibodies which mediate EBV neutralization, complement fixation, and antibody-dependent cellular cytotoxicity. The latter studies have often shown a correlation between the induction of gp340-specific EBV-neutralizing antibodies and protection from virus challenge. We have used a series of bacterial beta-galactosidase-gp340 fusion proteins and overlapping synthetic peptides from the gp340 open reading frame to map the positions of B-cell epitopes within the gp340 primary amino acid sequence. The data reported here indicate the presence of B-cell epitopes within the carboxy-terminal third of the gp340 polypeptide chain. These epitopes could not be detected with a peptide enzyme-linked immunosorbent assay, thereby suggesting that they are discontinuous. Affinity purification of antibodies with a gp340 fusion protein from the carboxy terminus of the gp340 polypeptide chain has been used to show that these antibodies are not EBV neutralizing in vitro. The consequences of these findings for future EBV vaccine development are considered.

Control of viral disease: the development of Epstein-Barr virus vaccines

Since the discovery of Epstein-Barr virus (EBV) in an African Burkitt 's lymphoma biopsy by M.A. Epstein in 1964 [17], research into the molecular biology and immunology of infection by this virus has grown to be a major field of interest. The association of EBV with two major human cancers, endemic Burkitt 's lymphoma [41] (BL) and undifferentiated nasopharyngeal carcinoma (NPC) [16, 28, 79, 80] led to the proposal for the development of a vaccine to prevent infection by the virus to reduce the incidence of, or to eliminate entirely, cancers associated with EBV infection [15]. The development of EBV vaccines, starting with the conventional subunit type, has closely paralleled developments in DNA technology, adjuvant research and advances in the immunology of EBV. This account describes the development of EBV vaccines in recent years starting with purified envelope glycoproteins as subunit vaccines and extending to live recombinant virus vectors and synthetic peptides. Such has been the progress in this field that Phase I human trials on a recombinant-derived purified envelope glycoprotein subunit vaccine are scheduled for the near future.

Identification of two T-cell epitopes on the candidate Epstein-Barr virus vaccine glycoprotein gp340 recognized by CD4+ T-cell clones

Current efforts to develop an Epstein-Barr virus subunit vaccine are based on the major envelope glycoprotein gp340. Given the central role of CD4+ T cells in regulating immune responses to subunit vaccine antigens, the present study has begun the work of identifying linear epitopes which are recognized by human CD4+ T cells within the 907-amino-acid sequence of gp340. A panel of gp340-specific CD4+ T-cell clones from an Epstein-Barr virus-immune donor were first assayed for their proliferative responses to a series of truncated gp340 molecules expressed from recombinant DNA vectors in rat GH3 cells, by using an autologous B lymphoblastoid cell line as a source of antigen-presenting cells. The first four T-cell clones analyzed all responded to a truncated form of gp340 which contained only the first 260 N-terminal amino acids. These clones were subsequently screened for responses to each of a panel of overlapping synthetic peptides (15-mers) corresponding to the primary amino acid sequence of the first 260 N-terminal amino acids of gp340. One clone (CG2.7) responded specifically to peptides from the region spanning amino acids 61 to 81, while three other clones (CG5.15, CG5.24, and CG5.36) responded specifically to peptides from the region spanning amino acids 163 to 183. Work with individual peptides from these regions allowed finer mapping of the T-cell epitopes and also revealed the highly dose-dependent nature of peptide-induced responses, with inhibitory effects apparent when the most antigenic peptides were present at supraoptimal concentrations. Experiments using homozygous typing B lymphoblastoid cell lines as antigen-presenting cells showed that the T-cell clones with different epitope specificities were restricted through different HLA class II antigens; clone CG2.7 recognized epitope 61-81 in the context of HLA DRw15, whereas clones CG5.15, CG5.24, and CG5.36 recognized epitope 163-183 in the context of HLA DRw11. The present protocol therefore makes a systematic analysis of CD4+ T-cell epitopes within gp340 possible; it will be necessary to screen gp340-specific T-cell clones from a variety of donors to assess the wider influence of HLA class II polymorphism upon epitope choice.