Identification of immunodominant regions and linear B cell epitopes of the gE envelope protein of varicella-zoster virus

Immunogenicity in Mice Immunized with Recombinant Adenoviruses Expressing Varicella-Zoster Virus Envelope Glycoprotein E

Herpes zoster (HZ) is a disease caused by the reactivation of latent varicella-zoster virus (VZV). The subunit vaccine, Shingrix®, and live attenuated vaccine, Zostavax®, could be used as an HZ vaccine that prevents HZ from being developed due to the reactivation of latent VZV in the sensory ganglia due to aging, stress or immunosuppression. In this study, the recombinant adenoviruses rChAd63/gE expressing glycoprotein E (gE) of VZV based on chimpanzee adenovirus serotype 63 (ChAd63) were constructed and investigated for the immunogenicity of different immune pathways in C57BL/6 mice. The results showed similar CD4+ T and CD8+ T cell responses to Shingrix® were induced in mice vaccinated using rChAd63/gE via different immune pathways. This study elucidates that recombinant adenoviruses expressing VZV gE could be appropriate for further development as a new HZ vaccine candidate via different immune pathways.

Truncated glycoprotein E of varicella-zoster virus is an ideal immunogen for Escherichia coli-based vaccine design

Varicella-zoster virus (VZV) is a highly infectious agent responsible for both varicella and herpes zoster disease. Despite high efficacy, there remain safety and accessibility concerns with the licensed vaccines. Here, we sought to produce a VZV gE immunogen using an E. coli expression system. We found that the soluble expression and yield of gE protein could be enhanced via C-terminal truncations to the protein, thereby facilitating a robust and scalable purification process for the purpose of vaccine manufacturing. The lead truncated gE (aa 31-358), hereafter referred to as tgE, was a homogenous monomer in solution and showed excellent antigenicity. Finally, we assessed and compared the immunogenicity of tgE with commercial vOka LAV and Shingrix vaccine. We found that aluminum-adjuvanted tgE was immunogenic as compared with vOka LAV. When adjuvanted with AS01_B, a two-dose immunization of tgE showed comparable or better potency in antibody responses and cell-mediated immunity with those of the Shingrix vaccine at the same dosage, especially in terms of the proportion of IFN-γ-expressing CD4⁺ T cells. In conclusion, this method of E. coli-mediate tgE expression offers a cost-effective and scalable strategy to generate an ideal VZV gE immunogen for the development of both varicella and zoster vaccines.

Recombinant Glycoprotein E of Varicella Zoster Virus Contains Glycan-Peptide Motifs That Modulate B Cell Epitopes into Discrete Immunological Signatures

A recombinant subunit vaccine (Shingrix^®) was recently licensed for use against herpes zoster. This vaccine is based on glycoprotein E (gE) of varicella zoster virus (VZV), the most abundantly expressed protein of VZV, harboring sites for N- and O-linked glycosylation. The subunit vaccine elicits stronger virus-specific CD4+ T cell response as well as antibody B cell response to gE, compared to the currently used live attenuated vaccine (Zostavax^®). This situation is at variance with the current notion since a live vaccine, causing an active virus infection, should be far more efficient than a subunit vaccine based on only one single viral glycoprotein. We previously found gE to be heavily glycosylated, not least by numerous clustered O-linked glycans, when it was produced in human fibroblasts. However, in contrast to Zostavax^®, which is produced in fibroblasts, the recombinant gE of Shingrix^® is expressed in Chinese hamster ovary (CHO) cells. Hence, the glycan occupancy and glycan structures of gE may differ considerably between the two vaccine types. Here, we aimed at (i) defining the glycan structures and positions of recombinant gE and (ii) identifying possible features of the recombinant gE O-glycosylation pattern contributing to the vaccine efficacy of Shingrix^®. Firstly, recombinant gE produced in CHO cells (“Shingrix situation”) is more scarcely decorated by O-linked glycans than gE from human fibroblasts (“Zostavax situation”), with respect to glycan site occupancy. Secondly, screening of immunodominant B cell epitopes of gE, using a synthetic peptide library against serum samples from VZV-seropositive individuals, revealed that the O-linked glycan signature promoted binding of IgG antibodies via a decreased number of interfering O-linked glycans, but also via specific O-linked glycans enhancing antibody binding. These findings may, in part, explain the higher protective efficacy of Shingrix^®, and can also be of relevance for development of subunit vaccines to other enveloped viruses.

Development of adjuvanted recombinant zoster vaccine and its implications for shingles prevention

INTRODUCTION

GSK has developed a two-dose adjuvanted recombinant zoster vaccine (Shingrix, RZV) to protect people aged ≥50 years (50+) against herpes zoster (HZ) and its complications. RZV showed >90% efficacy against HZ, sustained over 4 years of follow-up, in all studied age groups.

AREAS COVERED

This article reviews the scientific rationale underlying the design of RZV; the clinical evidence demonstrating immunogenicity, safety, and efficacy in persons 50+; and the public health implications and cost-effectiveness.

EXPERT COMMENTARY

A decline in varicella zoster virus (VZV) immunity is associated with increased risk of HZ in adults 50+ and immunocompromised individuals. RZV was designed to restore levels of anti-VZV cellular and humoral immunity to prevent VZV reactivation. RZV includes the recombinant gE glycoprotein antigen, and Adjuvant System AS01_B which promotes cellular and antibody responses. In two Phase III studies in subjects aged 50+ and 70+ years, RZV efficacy against HZ compared to placebo was >90% and ≥89% against post-herpetic neuralgia (PHN). RZV is expected to dramatically impact HZ morbidity including its complications, and associated health-care costs. In the US population aged 50+ years, vaccination with RZV can be cost-effective compared to no vaccination and cost-saving compared to the currently available live-attenuated HZ vaccine (Zostavax, Merck).

Peptide Vaccines: New Trends for Avoiding the Autoimmune Response

Background:

Several marketed antiviral vaccines (such as that against hepatitis virus A and/or B, influenza virus, human papillomavirus, yellow fever virus, measles, rubella and mumps viruses) may elicit various autoimmune reactions.

Results:

The cause of autoimmune response due to vaccination may be: 1. the adjuvant which is regularly added to the vaccine (especially in the case of various oil substrates), 2. the specific viral component itself (a protein or glycoprotein potentially possessing cross-reactive epitopes) and/or 3. contamination of the vaccine with traces of non-viral proteins mostly cellular in origin. Believing that peptide vaccines might represent an optimal solution for avoiding the above-mentioned problems, we discuss the principles of rational design of a typical peptide vaccine which should contain oligopeptides coming either from the selected structural virion components (i.e.capsid proteins and/or envelop glycoproteins or both) or from the virus-coded non-structural polypeptides. The latter should be equally immunogenic as the structural virus proteins. Describing the feasibility of identification and design of immunogenic epitopes, our paper also deals with possible problems of peptide vaccine manufacturing. The presented data are in part based on the experience of our own, in part, they are coming from the results published by others.

Conclusion:

Any peptide vaccine should be able to elicit relevant and specific antibody formation, as well as an efficient cell-mediated immune response. Consequently, the properly designed peptide vaccine is expected to consist of carefully selected viral peptides, which should stimulate the receptors of helper T/CD4 cells as well as of cytotoxic (T/CD8) lymphocytes.

A novel combined vaccine based on monochimeric VLP co-displaying multiple conserved epitopes against enterovirus 71 and varicella-zoster virus

Chicken pox and hand, foot and mouth disease (HFMD) are two major infectious diseases that mainly affect infants and children, causing significant morbidity annually. Varicella-zoster virus (VZV) and enterovirus 71 (EV71), respectively, are the principal epidemic pathogens causing these two diseases. To investigate the possibility of developing a novel combined vaccine to prevent chicken pox and HFMD, we constructed three chimeric virus-like particles (VLPs) (termed HBc-V/1/2, HBc-2/V/1 and HBc-1/2/V) based on the hepatitis B core antigen (HBc) carrier that display epitopes derived from VZV-gE, EV71-VP1, and EV71-VP2 in a varied tandem manner. The chimeric HBc can self-assemble into VLPs with these three epitopes displayed on the surface of particles. Epitope-specific antibody characterization suggested that HBc-V/1/2 elicits a balanced antibody response toward these three epitopes, and no immune interference was observed between the three epitopes. Importantly, the anti-HBc-V/1/2 sera could simultaneously neutralize VZV and EV71 and cross-neutralize coxsackievirus A16 (CVA16), another major pathogen causing HFMD. Moreover, the anti-HBc-V/1/2 sera protected neonatal mice from lethal challenge of EV71 and CVA16. Collectively, our study not only demonstrated that HBc-V/1/2 is a promising candidate combined vaccine for HFMD and Chicken pox but also provides a novel strategy for the design of combined vaccines.

Global Mapping of O-Glycosylation of Varicella Zoster Virus, Human Cytomegalovirus, and Epstein-Barr Virus

Herpesviruses are among the most complex and widespread viruses, infection and propagation of which depend on envelope proteins. These proteins serve as mediators of cell entry as well as modulators of the immune response and are attractive vaccine targets. Although envelope proteins are known to carry glycans, little is known about the distribution, nature, and functions of these modifications. This is particularly true for O-glycans; thus we have recently developed a "bottom up" mass spectrometry-based technique for mapping O-glycosylation sites on herpes simplex virus type 1. We found wide distribution of O-glycans on herpes simplex virus type 1 glycoproteins and demonstrated that elongated O-glycans were essential for the propagation of the virus. Here, we applied our proteome-wide discovery platform for mapping O-glycosites on representative and clinically significant members of the herpesvirus family: varicella zoster virus, human cytomegalovirus, and Epstein-Barr virus. We identified a large number of O-glycosites distributed on most envelope proteins in all viruses and further demonstrated conserved patterns of O-glycans on distinct homologous proteins. Because glycosylation is highly dependent on the host cell, we tested varicella zoster virus-infected cell lysates and clinically isolated virus and found evidence of consistent O-glycosites. These results present a comprehensive view of herpesvirus O-glycosylation and point to the widespread occurrence of O-glycans in regions of envelope proteins important for virus entry, formation, and recognition by the host immune system. This knowledge enables dissection of specific functional roles of individual glycosites and, moreover, provides a framework for design of glycoprotein vaccines with representative glycosylation.

Comparative preclinical evaluation of AS01 versus other Adjuvant Systems in a candidate herpes zoster glycoprotein E subunit vaccine

The candidate vaccine HZ/su is being developed to prevent herpes-zoster disease (HZ). HZ occurrence is attributed to declines in varicella-zoster virus (VZV) specific T-cell immunity. HZ/su contains VZV antigen, gE, and Adjuvant System AS01_B (liposome-based formulation of MPL and QS-21). In clinical trials, AS01_B enhances CD4⁺ T-cell responses to gE. In clinical trials of other vaccines, Adjuvant Systems AS03 and AS04 also enhance antigen-specific CD4⁺ T-cell responses. Hence the purpose of this study was to evaluate gE formulated with AS01_B, AS01_E (50% less MPL and QS-21 than AS01_B), AS03 or AS04 in C57BL6 mice primed with live-attenuated VZV. Four-weeks post-vaccination, the gE-specific CD4⁺ T-cell response to gE/AS01_B was 5.4, 2.8 and 2.2-fold greater than those to gE/AS03, gE/AS04 and gE/AS03, respectively (p<0.001). Therefore in the VZV-primed mouse model, CD4⁺ T-cell responses to gE appeared most enhanced by AS01_B, and adds further support for the use of AS01_B in the HZ/su formulation.

A highly conserved epitope-vaccine candidate against varicella-zoster virus induces neutralizing antibodies in mice

Varicella-zoster virus (VZV) is a highly infectious agent of varicella and herpes zoster (HZ). Vaccination is by far the most effective way to prevent these diseases. More safe, stable and efficient vaccines, such as epitope-based vaccines, now have been increasingly investigated by many researchers. However, only a few VZV neutralizing epitopes have been identified to date. We have previously identified a linear epitope between amino acid residues 121 and 135 of gE. In this study, we validated that this epitope is highly conserved amongst different VZV strains that covered five existing phylogenetic clades with an identity of 100%. We evaluated the immunogenicity of the recombinant hepatitis B virus core (HBc) virus-like particles (VLPs) which included amino acids (121-135). VZV-gE-specific antibodies were detected in immunized mouse serum using ELISA. The anti-peptide antiserum positively detected VZV via Western blot and immunofluorescent staining assays. More importantly, these peptides could neutralize VZV, indicating that these peptides represented neutralizing epitopes. These findings have important implications for the development of epitope-based protective VZV vaccines.

Serological Evaluation of Immunity to the Varicella-Zoster Virus Based on a Novel Competitive Enzyme-Linked Immunosorbent Assay

Varicella-zoster virus (VZV) is a highly contagious agent of varicella and herpes zoster. Varicella can be lethal to immunocompromised patients, babies, HIV patients and other adults with impaired immunity. Serological evaluation of immunity to VZV will help determine which individuals are susceptible and evaluate vaccine effectiveness. A collection of 110 monoclonal antibodies (mAbs) were obtained by immunization of mice with membrane proteins or cell-free virus. The mAbs were well characterized, and a competitive sandwich ELISA (capture mAb: 8H6; labelling mAb: 1B11) was established to determine neutralizing antibodies in human serum with reference to the FAMA test. A total of 920 human sera were evaluated. The competitive sandwich ELISA showed a sensitivity of 95.6%, specificity of 99.77% and coincidence of 97.61% compared with the fluorescent-antibody-to-membrane-antigen (FAMA) test. The capture mAb 8H6 was characterized as a specific mAb for VZV ORF9, a membrane-associated tegument protein that interacts with glycoprotein E (gE), glycoprotein B (gB) and glycoprotein C (gC). The labelling mAb 1B11 was characterized as a complement-dependent neutralizing mAb specific for the immune-dominant epitope located on gE, not on other VZV glycoproteins. The established competitive sandwich ELISA could be used as a rapid and high-throughput method for evaluating immunity to VZV.

Extensive CD4 and CD8 T Cell Cross-Reactivity between Alphaherpesviruses

The Alphaherpesvirinae subfamily includes HSV types 1 and 2 and the sequence-divergent pathogen varicella zoster virus (VZV). T cells, controlled by TCR and HLA molecules that tolerate limited epitope amino acid variation, might cross-react between these microbes. We show that memory PBMC expansion with either HSV or VZV enriches for CD4 T cell lines that recognize the other agent at the whole-virus, protein, and peptide levels, consistent with bidirectional cross-reactivity. HSV-specific CD4 T cells recovered from HSV-seronegative persons can be explained, in part, by such VZV cross-reactivity. HSV-1-reactive CD8 T cells also cross-react with VZV-infected cells, full-length VZV proteins, and VZV peptides, as well as kill VZV-infected dermal fibroblasts. Mono- and cross-reactive CD8 T cells use distinct TCRB CDR3 sequences. Cross-reactivity to VZV is reconstituted by cloning and expressing TCRA/TCRB receptors from T cells that are initially isolated using HSV reagents. Overall, we define 13 novel CD4 and CD8 HSV-VZV cross-reactive epitopes and strongly imply additional cross-reactive peptide sets. Viral proteins can harbor both CD4 and CD8 HSV/VZV cross-reactive epitopes. Quantitative estimates of HSV/VZV cross-reactivity for both CD4 and CD8 T cells vary from 10 to 50%. Based on these findings, we hypothesize that host herpesvirus immune history may influence the pathogenesis and clinical outcome of subsequent infections or vaccinations for related pathogens and that cross-reactive epitopes and TCRs may be useful for multi-alphaherpesvirus vaccine design and adoptive cellular therapy.

Adjuvanted herpes zoster subunit vaccine

This review highlights the characteristics of a candidate herpes zoster (HZ) vaccine (HZ/su, GlaxoSmithKline Vaccines) that consists of 50 μg recombinant glycoprotein E (gE) of varicella zoster virus adjuvanted with AS01B. It is well tolerated and shows a clinically acceptable tolerability profile. It strongly enhances pre-existing gE-specific CD4+ T-cell and anti-gE antibody responses in older adults and immunocompromised persons. Administration of two doses 2 months apart reduces the risk of HZ by 97.2% in adults ≥50 years. This effect does not diminish with increasing age. Long-term persistence of its efficacy still needs to be determined. This candidate HZ vaccine may become an alternative for the high-dose live-attenuated varicella zoster virus vaccine for the prevention of HZ in older persons and in immunocompromised patients in whom the use of live-attenuated vaccines is contraindicated.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Cell-mediated immune responses to a varicella-zoster virus glycoprotein E vaccine using both a TLR agonist and QS21 in mice

Lack of adequate cell-mediated immunity (CMI) to varicella-zoster virus (VZV) has been associated with higher risks of developing herpes zoster (HZ) and associated post-herpetic neuralgia (PHN), and is of particular concern for older and immunocompromised individuals. Thus, the development of an effective HZ vaccine with a clinically acceptable safety profile that is capable of addressing decreased immunity would be highly desirable. In this study we compared the immunogenicity of different vaccine formulations containing VZV glycoprotein E (gE), an important target for CMI and antibody responses, in a VZV-primed mouse model. The formulations included recombinant gE, either unadjuvanted, or combined with aluminium salt or an Adjuvant System (AS01 or AS02), and CMI was used as the primary immunological endpoint. All adjuvanted vaccines induced gE- and/or VZV-specific CD4(+) T cell and antibody responses. A formulation of gE with an Adjuvant System containing the immunostimulants QS21 and 3-O-desacyl-4'-monophosphoryl lipid A (MPL) was shown to be more immunogenic than gE with aluminium salt or unadjuvanted gE (gE/saline). Both immunostimulants were shown to act synergistically in enhancing CMI responses. Formulations with AS01 elicited high frequencies of CD4(+) T cells producing IFN-γ and IL-2. These responses were dose-dependent with respect to both antigen and adjuvant. The gE/AS01(B) candidate vaccine induced higher frequencies of CD4(+) T cells producing IL-2 and/or IFN-γ than all other gE/AS01 formulations, supporting its use for clinical evaluations.

Recombinant glycoprotein E produced in mammalian cells in large-scale as an antigen for varicella-zoster-virus serology

A recombinant glycoprotein E (gE) from varicella-zoster virus (VZV) was generated and produced in Chinese Hamster Ovary (CHO) cells, in the development of a specific antigen for analysis of IgG antibodies to VZV. Several stable gE-secreting clones were established and one clone was adapted to growth in serum-free suspension culture. When the cells were cultured in a perfusion bioreactor, gE was secreted into the medium, from where it could be easily purified. The recombinant gE was then evaluated as a serological antigen in ELISA. When compared to a conventional whole virus antigen, the VZV gE showed similar results in ELISA-based seroprevalence studies of 854 samples derived from blood donors, students, ischemic stroke patients and their controls, including samples with border-line results in previous analyses. Eight samples (0.9%) were discordant, all being IgG-negative by the VZV gE ELISA and positive by the whole virus ELISA. The sensitivity and specificity of the VZV gE ELISA were 99.9% and 100%, respectively, compared to 100% and 88.9% for the VZV whole virus ELISA. The elderly subjects showed similar reactivities to both antigens, while VZV gE gave lower signals in the younger cohorts, suggesting that antibodies to gE may increase with age. It was concluded that the recombinant VZV gE from CHO cells was suitable as a serological antigen for the detection of IgG antibodies specific for VZV.

Varicella-zoster virus transcriptome in latently infected human ganglia

We recently developed a novel multiplex reverse transcription (RT)-PCR assay that allows rapid and sensitive detection of transcripts corresponding to all 68 unique varicella-zoster virus (VZV) open reading frames (ORFs) in only five amplification reactions (M. A. Nagel, D. Gilden, T. Shade, B. Gao, and R. J. Cohrs, J. Virol. Methods 157:62-68, 2009). Herein, we applied multiplex RT-PCR analysis to mRNA extracted from 26 trigeminal ganglia latently infected with VZV and one control trigeminal ganglion negative for VZV DNA that were removed from 14 men and women, 16 to 84 years of age, within 24 h after death. Analysis identified VZV transcripts mapping to VZV ORFs 29, 62, and 63, previously detected and sequence verified; VZV ORFs 4 and 40, previously detected by in situ hybridization; and VZV ORFs 11, 41, 43, 57, and 68, not previously detected. VZV ORF 63 transcripts were the most prevalent. Comparison of the 10 VZV ORFs transcribed during latency to their herpes simplex virus type 1 homologues reveals that the latently transcribed VZV genes encode immediate-early, early, and late transcripts.

Varicella-zoster virus immune evasion

CD4+ and CD8+ T cells play dual roles in varicella-zoster virus (VZV) pathogenesis. The first role is to deliver the virus to cutaneous sites during primary VZV infection, permitting replication at these sites and the successful transmission of the virus to other susceptible individuals. The second contribution of T cells is to provide the critical antigen-specific adaptive immunity needed to stop viral replication and maintain VZV latency in sensory ganglia. The equilibrium between VZV and the host can be predicted to be served by immune evasion mechanisms in at least two important ways, including the facilitation of cell-associated viremia during primary VZV infection and silent persistence in dorsal root ganglia. Interference with antigen presentation by MHC class I downregulation may be expected to play a role in both circumstances. Transient interference with MHC class II expression in varicella skin lesions should facilitate local replication and transmission. In addition, when VZV reactivates, the capacity of viral gene products to block the upregulation of MHC class II expression triggered by interferon-gamma should permit a sufficient period of viral replication to cause the lesions of herpes zoster, despite the presence of VZV-specific T cells, and to allow transmission of the virus to susceptible individuals. Although the effort is at an early stage compared to studies of other viral pathogens, identifying the VZV gene products that exert these effects and their mechanisms of interference has the potential to reveal novel aspects of MHC class I and class II antigen processing and presentation.

Induction of neutralizing antibody and T-cell responses to varicella-zoster virus (VZV) using Ty-virus-like particles carrying fragments of glycoprotein E (gE)

During infection with Varicella-zoster virus (VZV), the envelope proteins are highly immunogenic and glycoprotein E (gE) is one of the most abundant and antigenic. We have previously identified the immunodominant regions of gE and mapped the B-cell epitopes. In this study, we have evaluated the immunogenicity of recombinant hybrid Ty-virus-like particles (VLPs) carrying amino acids (1-134) or (101-161) of gE which contain the immunodominant sequences. VZV-specific antibodies were detected by ELISA in sera from mice and guinea pigs immunized with either gE(1-134)-VLPs or gE (101-161)-VLPs. The dominant B-cell epitopes, mapped by pepscan analysis of the sera, were found in peptides spanning amino acids 41-60, 56-75, 101-120, 116-135, 131-150 and 141-161. These sera also showed neutralizing activity against VZV in vitro. Epitopes recognized by neutralizing MAbs were mapped to both gE sequences (3B3 MAb recognizing amino acids 141-161 and IFB9 MAb recognizing amino acids 71-90). Lymphocyte proliferative responses to VZV were detected in four different mouse strains immunized with either gE(1-134)-VLPs or gE(101-134)-VLPs in alum. All mouse strains immunized with gE(1-134)-VLPs recognized epitopes in amino acids 11-30 and 71-90 and all those immunized with gE(101-161)-VLPs recognized epitopes in amino acids 91-110 and 106-125. These results indicate that VLPs carrying these gE sequences can prime potent humoral and cellular anti-VZV responses in small animals and warrant further investigation as potential vaccine candidates against varicella-zoster infections.