Three major glycoprotein genes of varicella-zoster virus whose products have neutralization epitopes

Current Methods for the Detection of Antibodies of Varicella-Zoster Virus: A Review

Infection with the varicella-zoster virus (VZV) causes chickenpox and shingles, which lead to significant morbidity and mortality globally. The detection of serum VZV-specific antibodies is important for the clinical diagnosis and sero-epidemiological research of VZV infection, and for assessing the effect of VZV vaccine immunization. Over recent decades, a variety of methods for VZV antibody detection have been developed. This review summarizes and compares the current methods for detecting VZV antibodies, and discussed future directions for this field.

Understanding the immunology of the Zostavax shingles vaccine

Zostavax is a live-attenuated varicella zoster virus (VZV) vaccine recommended for use in adults >50 years of age to prevent shingles. The main risk factor for the development of shingles is age, which correlates with decreasing cell-mediated immunity. These data suggest a predominant role of T cell immunity in controlling VZV latency. However, other components of the immune system may also contribute. In this review, we will discuss how the immune system responds to Zostavax, focusing on recent studies examining innate immunity, transcriptomics, metabolomics, cellular, and humoral immunity.

Breadth and Functionality of Varicella-Zoster Virus Glycoprotein-Specific Antibodies Identified after Zostavax Vaccination in Humans

Herpes zoster (HZ) (shingles) is the clinical manifestation of varicella-zoster virus (VZV) reactivation. HZ typically develops as people age, due to decreased cell-mediated immunity. However, the importance of antibodies for immunity against HZ prevention remains to be understood. The goal of this study was to examine the breadth and functionality of VZV-specific antibodies after vaccination with a live attenuated HZ vaccine (Zostavax). Direct enumeration of VZV-specific antibody-secreting cells (ASCs) via enzyme-linked immunosorbent spot assay (ELISPOT assay) showed that Zostavax can induce both IgG and IgA ASCs 7 days after vaccination but not IgM ASCs. The VZV-specific ASCs range from 33 to 55% of the total IgG ASCs. Twenty-five human VZV-specific monoclonal antibodies (MAbs) were cloned and characterized from single-cell-sorted ASCs of five subjects (>60 years old) who received Zostavax. These MAbs had an average of ∼20 somatic hypermutations per VH gene, similar to those seen after seasonal influenza vaccination. Fifteen of the 25 MAbs were gE specific, whereas the remaining MAbs were gB, gH, or gI specific. The most potent neutralizing antibodies were gH specific and were also able to inhibit cell-to-cell spread of the virus in vitro Most gE-specific MAbs were able to neutralize VZV, but they required the presence of complement and were unable to block cell-to-cell spread. These data indicate that Zostavax induces a memory B cell recall response characterized by anti-gE > anti-gI > anti-gB > anti-gH antibodies. While antibodies to gH could be involved in limiting the spread of VZV upon reactivation, the contribution of anti-gE antibodies toward protective immunity after Zostavax needs further evaluation.IMPORTANCE Varicella-zoster virus (VZV) is the causative agent of chickenpox and shingles. Following infection with VZV, the virus becomes latent and resides in nerve cells. Age-related declines in immunity/immunosuppression can result in reactivation of this latent virus, causing shingles. It has been shown that waning T cell immunity correlates with an increased incidence of VZV reactivation. Interestingly, serum with high levels of VZV-specific antibodies (VariZIG; IV immunoglobulin) has been administered to high-risk populations, e.g., immunocompromised children, newborns, and pregnant women, after exposure to VZV and has shown some protection against chickenpox. However, the relative contribution of antibodies against individual surface glycoproteins toward protection from shingles in elderly/immunocompromised individuals has not been established. Here, we examined the breadth and functionality of VZV-specific antibodies after vaccination with the live attenuated VZV vaccine Zostavax in humans. This study will add to our understanding of the role of antibodies in protection against shingles.

Analysis of codon usage pattern of infectious laryngotracheitis virus immunogenic glycoproteins and its biological implications

Infectious laryngotracheitis virus (ILTV) is a highly contagious acute respiratory poultry pathogen. Modified live ILTV vaccines are the only control against ILT infections. Reversions and establishment of latent infections are the major concerns imparting the need to develop safer vaccines against ILTV infection. ILTV glycoprotein B and D (gB and gD) are major protective immunogens. The factors shaping synonymous codon usage bias and nucleotide composition in ILTV glycoprotein genes have not yet been reported. In the present study, we have analyzed the synonymous codon usage indices of ILTV gB and gD genes. Variation in the codon usage was seen in both the glycoproteins majorly by mutational pressure. The pattern was determined using the correspondence analysis, effective number of codon (Nc), GC3 plot and correlation analyses among different indices. The study is a comprehensive analysis of the codon usage patterns of ILTV glycoprotein genes. This will be helpful in understanding the codon usage bias of ILTV and related DNA viruses which could further explore its biology.

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.

Evaluation of the Protection Efficacy of a Serotype 1 Marek's Disease Virus-Vectored Bivalent Vaccine Against Infectious Laryngotracheitis and Marek's Disease

Laryngotracheitis (LT) is a highly contagious respiratory disease of chickens that produces significant economic losses to the poultry industry. Traditionally, LT has been controlled by administration of modified live vaccines. In recent years, the use of recombinant DNA-derived vaccines using turkey herpesvirus (HVT) and fowlpox virus has expanded, as they protect not only against the vector used but also against LT. However, HVT-based vaccines confer limited protection against challenge, with emergent very virulent plus Marek's disease virus (vv+MDV). Serotype 1 vaccines have been proven to be the most efficient against vv+MDV. In particular, deletion of oncogene MEQ from the oncogenic vvMDV strain Md5 (BACδMEQ) resulted in a very efficient vaccine against vv+MDV. In this work, we have developed two recombinant vaccines against MD and LT by using BACδMEQ as a vector that carries either the LT virus (LTV) gene glycoprotein B (gB; BACΔMEQ-gB) or LTV gene glycoprotein J (gJ; BACδMEQ-gJ). We have evaluated the protection that these recombinant vaccines confer against MD and LT challenge when administered alone or in combination. Our results demonstrated that both bivalent vaccines (BACΔMEQ-gB and BACδMEQ-gJ) replicated in chickens and were safe to use in commercial meat-type chickens bearing maternal antibodies against MDV. BACΔMEQ-gB protected as well as a commercial recombinant (r)HVT-LT vaccine against challenge with LTV. However, BACδMEQ-gJ did not protect adequately against LT challenge or increase protection conferred by BACΔMEQ-gB when administered in combination. On the other hand, both BACΔMEQ-gB and BACδMEQ-gJ, administered alone or in combination, protected better against an early challenge with vv+MDV strain 648A than commercial strains of rHVT-LT or CVI988. Our results open a new avenue in the development of recombinant vaccines by using serotype 1 MDV as vectors.

High-level cellular and humoral immune responses in Guinea pigs immunized intradermally with a heat-inactivated varicella-zoster virus vaccine

The threat of varicella and herpes zoster in immunocompromised individuals necessitates the development of a safe and effective varicella-zoster virus (VZV) vaccine. The immune responses of guinea pigs to the intradermal (i.d.) or subcutaneous (s.c.) administration of a heat-inactivated or live VZV vaccine were investigated. Relative to nonimmunized animals, a single 399-PFU dose of vaccine induced nonsignificant increases in gamma interferon (IFN-γ), granzyme B, and perforin mRNA expression in the splenocytes of all groups, while two i.d. administrations of the inactivated vaccine increased IFN-γ mRNA expression significantly (P < 0.005). A single 1,995-PFU dose significantly increased the expression of IFN-γ mRNA in the groups receiving the vaccine either i.d. (P < 0.005) or s.c. (P < 0.05), that of granzyme B mRNA in the groups immunized i.d. with the inactivated (P < 0.005) or live (P < 0.005) vaccine, and that of perforin mRNA in the animals that received the inactivated vaccine i.d. (P < 0.005). Importantly, increases in the expression of IFN-γ (P = 0.025), granzyme B (P = 0.004), and perforin (P > 0.05) mRNAs were observed in the animals immunized i.d. with 1,995 PFU of inactivated vaccine relative to those immunized s.c. with the same dose. The proportion of animals expressing IFN-γ mRNA mirrored the proportion expressing IFN-γ protein (correlation coefficient of 0.88). VZV glycoprotein-specific and virus-neutralizing antibodies were produced with no significant intergroup differences. A booster i.d. administration of the 399-PFU dose of heat-inactivated vaccine enhanced the antibody responses. These results demonstrate that i.d. administration of an inactivated VZV vaccine can be an efficient mode of immunization against VZV.

Evaluation of a commercial glycoprotein enzyme-linked immunosorbent assay for measuring vaccine immunity to varicella

PURPOSE

To evaluate a recently marketed commercial glycoprotein enzyme-linked immunosorbent assay (gpEIA) kit, the VaccZyme™ VZV gpEIA, for measuring the immunity of varicella-vaccinated children.

MATERIALS AND METHODS

We investigated the accuracy and reproducibility of the VaccZyme™ VZV gpEIA kit for the detection of antibodies to VZV. We also examined the sensitivity, specificity, and correlation between antibody titers calculated with gpEIA versus fluorescent antibody to membrane antigen (FAMA) by using sera of 349 children, ranging from 1 to 6 years old.

RESULTS

VaccZyme™ VZV gpEIA gave precise and reproducible intra- and inter-assay results. FAMA and gpEIA titers showed a linear correlation (Pearson correlation coefficient=0.987). The sensitivity and specificity of the VaccZyme™ gpEIA was 31.4% and 100%, respectively, when the guidelines of the gpEIA (<100 mIU/mL) and FAMA 1:4 were adopted as cutoff values. However, the maximum sensitivity and specificity were 88.9% and 95.1%, respectively, with the highest correlation (κ=0.840), if the cutoff values were set with gpEIA at 49.7 mIU/mL and FAMA 1:16.

CONCLUSION

These results demonstrate that the VaccZyme™ VZV gpEIA kit gave precise and reproducible data for measuring antibody titer after varicella vaccination. The results also showed that the antibody titer calculated with the VaccZyme™ gpEIA kit strongly correlated with the FAMA titer. However, cutoff values should be re-optimized for the evaluation of vaccine immunity.

Duck enteritis virus glycoprotein D and B DNA vaccines induce immune responses and immunoprotection in Pekin ducks

DNA vaccine is a promising strategy for protection against virus infection. However, little is known on the efficacy of vaccination with two plasmids for expressing the glycoprotein D (gD) and glycoprotein B (gB) of duck enteritis virus (DEV) in inducing immune response and immunoprotection against virulent virus infection in Pekin ducks. In this study, two eukaryotic expressing plasmids of pcDNA3.1-gB and pcDNA3.1-gD were constructed. Following transfection, the gB and gD expressions in DF1 cells were detected. Groups of ducks were vaccinated with pcDNA3.1-gB and/or pcDNA3.1-gD, and boosted with the same vaccine on day 14 post primary vaccination. We found that intramuscular vaccinations with pcDNA3.1-gB and/or pcDNA3.1-gD, but not control plasmid, stimulated a high frequency of CD4+ and CD8+ T cells in Pekin ducks, particularly with both plasmids. Similarly, vaccination with these plasmids, particularly with both plasmids, promoted higher levels of neutralization antibodies against DEV in Pekin ducks. More importantly, vaccination with both plasmids significantly reduced the virulent DEV-induced mortality in Pekin ducks. Our data indicated that vaccination with plasmids for expressing both gB and gD induced potent cellular and humoral immunity against DEV in Pekin ducks. Therefore, this vaccination strategy may be used for the prevention of DEV infection in Pekin ducks.

[Varicella-zoster virus (VZV)]

Varicella-zoster virus (VZV) causes varicella in primary infection and zoster after reactivation from latency. Both herpes simplex virus (HSV) and VZV are classified into the same alpha-herpesvirus subfamily. Although most VZV genes have their HSV homologs, VZV has many unique biological characteristics. In this review, we summarized recent studies on 1) animal models for VZV infection and outcomes from studies using the models, including 2) viral dissemination processes from respiratory mucosa, T cells, to skin, 3) cellular receptors for VZV entry, 4) functions of viral genes required uniquely for in vivo growth and for establishment of latency, 5) host immune responses and viral immune evasion mechanisms, and 6) varicella vaccine and anti-VZV drugs.

Insulin degrading enzyme induces a conformational change in varicella-zoster virus gE, and enhances virus infectivity and stability

Varicella-zoster virus (VZV) glycoprotein E (gE) is essential for virus infectivity and binds to a cellular receptor, insulin-degrading enzyme (IDE), through its unique amino terminal extracellular domain. Previous work has shown IDE plays an important role in VZV infection and virus cell-to-cell spread, which is the sole route for VZV spread in vitro. Here we report that a recombinant soluble IDE (rIDE) enhances VZV infectivity at an early step of infection associated with an increase in virus internalization, and increases cell-to-cell spread. VZV mutants lacking the IDE binding domain of gE were impaired for syncytia formation and membrane fusion. Pre-treatment of cell-free VZV with rIDE markedly enhanced the stability of the virus over a range of conditions. rIDE interacted with gE to elicit a conformational change in gE and rendered it more susceptible to proteolysis. Co-incubation of rIDE with gE modified the size of gE. We propose that the conformational change in gE elicited by IDE enhances infectivity and stability of the virus and leads to increased fusogenicity during VZV infection. The ability of rIDE to enhance infectivity of cell-free VZV over a wide range of incubation times and temperatures suggests that rIDE may be useful for increasing the stability of varicella or zoster vaccines.

Quantitative measurement of varicella-zoster virus infection by semiautomated flow cytometry

Varicella-zoster virus (VZV; human herpesvirus 3) is the etiological cause of chickenpox and, upon reactivation from latency, zoster. Currently, vaccines are available to prevent both diseases effectively. A critical requirement for the manufacturing of safe and potent vaccines is the measurement of the biological activity to ensure proper dosing and efficacy, while minimizing potentially harmful secondary effects induced by immunization. In the case of live virus-containing vaccines, such as VZV-containing vaccines, biological activity is determined using an infectivity assay in a susceptible cellular host in vitro. Infectivity measurements generally rely on the enumeration of plaques by visual inspection of an infected cell monolayer. These plaque assays are generally very tedious and labor intensive and have modest throughput and high associated variability. In this study, we have developed a flow cytometry assay to measure the infectivity of the attenuated vaccine strain (vOka/Merck) of VZV in MRC-5 cells with improved throughput. The assay is performed in 96-well tissue culture microtiter plates and is based on the detection and quantification of infected cells expressing VZV glycoproteins on their surfaces. Multiple assay parameters have been investigated, including specificity, limit of detection, limit of quantification, range of linear response, signal-to-noise ratio, and precision. This novel assay appears to be in good concordance with the classical plaque assay results and therefore provides a viable, higher-throughput alternative to the plaque assay.

Characterization of neutralizing epitopes of varicella-zoster virus glycoprotein H

Varicella-zoster virus (VZV) glycoprotein H (gH) is the major neutralization target of VZV, and its neutralizing epitope is conformational. Ten neutralizing human monoclonal antibodies to gH were used to map the epitopes by immunohistochemical analysis and were categorized into seven epitope groups. The combinational neutralization efficacy of two epitope groups was not synergistic. Each epitope was partially or completely resistant to concanavalin A blocking of the glycomoiety of gH, and their antibodies inhibited the cell-to-cell spread of infection. The neutralization epitope comprised at least seven independent protein portions of gH that served as the target to inhibit cell-to-cell spread.

Isolation of therapeutic human monoclonal antibodies for varicella-zoster virus and the effect of light chains on the neutralizing activity

Therapeutic antibodies against varicella-zoster virus (VZV) were isolated from a combinatorial library of human antibodies using a phage-display system. Purified gH:gL was used to screen the library, and approximately 300 clones were isolated. Eight kinds of Fab-cp3-fused molecules (clones 10, 24, 36, 60, 94, 120, 192, and 431) neutralized viral infectivity. After conversion of Fab-cp3 antibodies to the Fab-protein A form, the concentrations of antibodies showing 50% inhibition of plaque formation ranged from 0.12 to 400 nM. Clones 10, 24, 94, 120 and 431 neutralized wild strains without showing strain specificity and were further converted to human IgG(1). Two clones (24 and 94) were confirmed to react with gH:gL and VZV-infected cells. IgG of clone 94 prevented spreading of infected cells. Thus these antibodies exhibited the typical phenotype of anti-gH antibody. Next the contribution of light (L) chains to neutralizing activity was analyzed by comparing the effect of L chain of clones 10, 120, and 192 with the identical heavy chain on their neutralizing activity. The L chain in the Fab form of clone 94 was replaced by L chains of clones 10, 24, 36, and 60 and the neutralizing activity of these replaced antibodies was weaker than that of the prototype clone 94. When the kappa-L chain of clone 94 was replaced by the lambda-L chain of clone 24, this antibody possessed neutralizing activity despite the kappa-lambda class change. Thus, human antibody library against VZV-gH has been established and characterized the role of the L chain in VZV-neutralizing activity to engineering further an antibody with stronger neutralizing activity.

Identification and DNA sequence analysis of the Marek's disease virus serotype 2 gene homologous to the herpes simplex virus type 1 glycoprotein H

Marek's disease virus (MDV) serotype 2 (MDV2) gene homologous to the glycoprotein H (gH) gene of herpes simplex virus type 1 was identified and sequenced. The predicted region encoding for the MDV2 gH gene was 2436 nucleotide and the primary translation product was 812 amino acids with a molecular weight of 89.4 kDa. The protein encoded by MDV2 gH gene has a number of features characteristic of a membrane-associated glycoprotein. First, there are 9 potential N-linked glycosylation sites and 11 cysteine residues, and 6 of the sites and 8 of the residues were conserved among all of the three MDV serotypes. Second, this protein had N-terminal and C-terminal hydrophobic regions, which were a signal sequence and a transmembrane-anchor domain, respectively. From the northern blot analysis, it was suggested that a transcript encoding MDV2 gH and a poly-cistronic transcript encoding MDV2 thymidine kinase, gH, and possibly other genes of downstream on this strand existed. Alignment of the amino acid sequences of the gH homologues among the three MDV serotypes showed 57.5% (MDV1 and MDV2), 56.2% (MDV1 and HVT), and 50.1% (MDV2 and HVT) identities.

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.

Live attenuated varicella vaccine

Varicella-zoster virus (VZV) is a ubiquitous human pathogen that causes varicella, commonly called chicken pox; establishes latency; and reactivates as herpes zoster, referred to as shingles. A live attenuated varicella vaccine, derived from the Oka strain of VZV has clinical efficacy for the prevention of varicella. The vaccine induces persistent immunity to VZV in healthy children and adults. Immunization against VZV also has the potential to lower the risk of reactivation of latent virus. The varicella vaccine may eventually reduce or eliminate herpes zoster, which is a serious problem for elderly and immunocompromised individuals.

Assays for antibodies to varicella-zoster virus

Anti-varicella-zoster virus serum antibody assays and their use in vaccine development are described. Of particular interest are FAMA and neutralization assays and the gpELISA. These and other assays are compared and summarized in terms of characteristics including biologic relevance, sensitivity, specificity, and suitability for different laboratory and clinical applications.

Immune responses to varicella-zoster virus

The host response to VZV is critical to the outcome of primary VZV infection. The maintenance of immune memory to the virus is required to prevent symptomatic re-infection on exogenous re-exposure to VZV and to prevent symptomatic reactivation of endogenous virus. Immunization with live varicella (Oka) vaccine elicits primary and memory immunity to VZV. Humoral and cell-mediated host responses induced by the wild-type virus and by the vaccine strain are comparable, which is consistent with the clinical observation that varicella vaccine protects against or significantly reduces the clinical symptoms caused by primary VZV infection. Widespread use of the varicella vaccine in healthy children will yield further knowledge about host-virus interactions, such as the role of exogenous re-exposure in maintaining persistent immunity, which will be relevant to vaccine strategies to prevent other human herpesvirus infections.

Purification, characterization and immunogenicity of recombinant varicella-zoster virus glycoprotein gE secreted by Chinese hamster ovary cells

The gene of the varicella-zoster virus (VZV) glycoprotein gE, engineered to code for a truncated molecule lacking the anchor and carboxy-terminal tail domains, was transfected into Chinese hamster ovary (CHO) cells via the pEE14 mammalian expression vector. One recombinant cell line, CHO-gE-2-9, secreted high levels of truncated gE into the culture medium. The product was purified to near homogeneity by a combination of anion exchange, hydrophobic and metal-chelate chromatographies. Purified recombinant gE showed the expected amino-terminal sequence and its glycosylation pattern proved similar to that of the natural product. When injected into mice, using either Freund's or alum as adjuvant, the native truncated gE induced complement-dependent neutralizing antibodies. In contrast, when the molecule was first denatured, it lost immunogenicity with alum. These data show that the recombinant gE, although truncated, could potentially be included in a subunit vaccine against VZV infection.

DNA sequence of the simian varicella virus (SVV) gH gene and analysis of the SVV and varicella zoster virus gH transcripts

The varicella zoster virus (VZV) glycoprotein H (gH) stimulates VZV-specific immune responses and may be involved in virus penetration. This study reports the genomic map position and the DNA sequence of a simian varicella virus (SVV) homologue of the VZV gH gene. A 32P-labeled VZV gH-specific DNA probe hybridized to the HindIII B subclone of the SVV BamHI B restriction endonuclease (RE) fragment. The DNA sequence of the SVV HindIII B subclone was determined and analysis indicated a SVV open reading frame (ORF) homologous to several herpesvirus gH genes. The SVV gH ORF is 2559 base pairs in size and encodes a 852-amino acid protein. The SVV gH contains characteristics of a transmembrane glycoprotein including: 9 consensus N-linked glycosylation sites, a potential amino terminal signal sequence, and a predicted transmembrane segment located near the carboxyl terminus. The SVV and VZV gH genes exhibit 60.0% identity and the predicted polypeptides exhibit 54.5% identity. The SVV and VZV gH transcripts were analyzed and the promoter regions were compared. 32P-labeled SVV and VZV gH-specific DNA probes each hybridized to a single 2.9 kilobase transcript. The mRNA start sites of the SVV and VZV gH genes were determined by primer extension analysis, and alignment of the promoter regions indicated similar content and arrangement. The extensive conservation of SVV and VZV genes and predicted polypeptides further supports the use of SVV infection of non-human primates as a model of VZV infection of humans.

Combined use of complement and anti-immunoglobulin in an enhanced neutralization assay for antibodies to varicella-zoster virus

An enhanced neutralization assay was developed to permit the sensitive, specific, and reproducible measurement of antibodies to varicella-zoster virus (VZV). Optimal neutralization was achieved using a combination of guinea pig complement (C') and rabbit anti-human IgG. This provided 625-, 160- and 13- to 64-fold increases in dilution endpoints of human post-zoster serum, varicella-zoster immune globulin and representative sera from recipients of live attenuated varicella vaccine, respectively, above those measured in the absence of C' and anti-IgG. The specificity of the assay was shown by the absorption of serum neutralization capacity with VZV-specific antigen and the lack of concordance between antibody titers to VZV with those to either herpes simplex virus type-2 or cytomegalovirus. The antibody status of recipients of live attenuated varicella vaccine was established from the amount of neutralizing activity produced at a single optimal serum dilution.

Antibody-binding sites on truncated forms of varicella-zoster virus gpI(gE) glycoprotein

Varicella-zoster virus (VZV)-seropositive human sera were shown to be reactive with the truncated VZV gpI(gE) candidate subunit vaccine (TgpI-511). To identify the location of antibody-binding sites (epitopes) on TgpI-511, three truncated forms of TgpI-511 glycoprotein (TgpI-124, TgpI-160, TgpI-316) DNA encoding the N-terminal region of this glycoprotein with amino acid residues of 124, 160 and 360, respectively, were inserted into the vaccinia virus genome. Infection of cells with recombinant vaccinia viruses resulted in the secretion of all three truncated gpI(gE) as well as TgpI-511 from the infected cells. Immunoprecipitation of these truncated glycoproteins with VZV-seropositive human sera and gpI(gE)-specific monoclonal antibodies identified the location of four new antibody-binding sites on the VZV TgpI-511 glycoprotein. In addition, tunicamycin treatment and O-glycanase digestion revealed the presence of both N-linked and O-linked oligosaccharides on TgpI-511. These results revealed the location of new epitopes on VZV TgpI-511 and demonstrated that the epitopes on TgpI-511 were recognized by human sera from VZV-seropositive individuals.

Intracellular transport of newly synthesized varicella-zoster virus: final envelopment in the trans-Golgi network

The maturation and envelopment of varicella-zoster virus (VZV) was studied in infected human embryonic lung fibroblasts. Transmission electron microscopy confirmed that nucleocapsids acquire an envelope from the inner nuclear membrane as they enter the perinuclear-cisterna-rough endoplasmic reticulum (RER). Tegument is not detectable in these virions; moreover, in contrast to the mature VZV envelope, the envelope of VZV in the RER is not radioautographically labeled in pulse-chase experiments with [3H]mannose, and it lacks gpI immunoreactivity and complex oligosaccharides. This primary envelope fuses with the RER membrane (detected in cells incubated at 20 degrees C), thereby releasing nucleocapsids to the cytosol. Viral glycoproteins, traced by transmission electron microscopy radioautography in pulse-chase experiments with [3H]mannose, are transported to the trans-Golgi network (TGN) by a pathway that runs from the RER through an intermediate compartment and the Golgi stack. At later chase intervals, [3H]mannose labeling becomes associated with enveloped virions in post-Golgi locations (prelysosomes and plasma membrane). Nucleocapsids appear to be enveloped by wrapping in specialized cisternae, identified as the TGN with specific markers. Tegument-like material adheres to the cytosolic face of the concave surface of TGN sacs; nucleocapsids adhere to this protein, which is thus trapped between the nucleocapsid and the TGN-derived membrane that wraps around it. Experiments with brefeldin A suggest that tegument may bind to the cytosolic tails of viral glycoproteins. Fusion and fission convert the TGN-derived wrapping sacs into an inner enveloped virion and an outer transport vesicle that carries newly enveloped virions to cytoplasmic vacuoles. These vacuoles are acidic and were identified as prelysosomes. It is postulated that secreted virions are partially degraded by their exposure to the prelysosomal internal milieu and rendered noninfectious. This process explains the cell-associated nature of VZV in vitro; however, the mechanism by which the virus escapes diversion from the secretory pathway to the lysosomal pathway in vivo remains to be determined.

Characterization and immunogenicity of a candidate subunit vaccine against varicella-zoster virus

This study describes the properties of an inactivated subunit antigen preparation from varicella-zoster virus (VZV)-infected MRC-5 cells by treatment with detergent and formaldehyde, ultracentrifugation over sucrose and acetone precipitation. The method preserved the antigenicity of VZV proteins and several VZV-specific glycoproteins, while virus DNA was less than 20 pg/250 micrograms protein--a putative vaccine dose. The vaccine was immunogenic in rabbits and stimulated antibodies to the major capsid protein as well as to glycoproteins; an immunoprecipitin was shared with a known immune human serum. The preparation contained no infectious VZV with no evidence of side effects in a rabbit or in five human vaccinees during a follow-up period of 6-10 years.

Characterization of immunoreactive octapeptides of human-cytomegalovirus gp58

We have mapped continuous epitopes, for positions 591-673 of the human cytomegalovirus 58-kDa glycoprotein using overlapping synthetic peptides and human sera. This region contains a fragment previously described as including the dominant site for induction of human-cytomegalovirus antibodies. Since the selected sequence is highly conserved among herpes viruses, we have considered the possible presence of antigenic cross-reactivity, particularly with the Epstein-Barr virus. Several peptides in the studied region were antigenic and two main continuous epitopes have been identified. Serological cross-reactions observed with Epstein-Barr virus are discussed, focusing on the possible implications of structural features and sequence similarity between human-cytomegalovirus and Epstein-Barr-virus glycoproteins.

Flow cytometric analysis of effects of cytokines on the expression of varicella-zoster virus glycoproteins

Varicella-zoster virus (VZV)-infected human embryonic fibroblast (HEF) cells were stained with monoclonal antibodies directed against VZV glycoprotein I, II and IV, and then labeled with fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG. The cells were analyzed by flow cytometry. VZV-infected cells expressing VZV glycoproteins were clearly distinguished from uninfected cells. This method was useful for analyzing expression of VZV glycoproteins in different experimental conditions. Interferon alpha, beta, and gamma and tumor necrosis factor (TNF)-alpha reduced the percentage of positive cells and the mean fluorescence intensity of the cells expressing VZV glycoproteins. Interleukin(IL)-1 beta, IL-6 and TNF-beta had little effect on the expression of VZV glycoproteins.

Expression of the Marek's disease virus (MDV) homolog of glycoprotein B of herpes simplex virus by a recombinant baculovirus and its identification as the B antigen (gp100, gp60, gp49) of MDV

A gene encoding a homolog of glycoprotein B of herpes simplex virus (gB homolog) has been identified on the Marek's disease virus (MDV) genome (L. J. N. Ross, M. Sanderson, S. D. Scott, M. M. Binns, T. Doel, and B. Milne, J. Gen. Virol. 70:1789-1804, 1989); however, the molecular and immunological characteristics of the gene product(s) are still not clear. In the present study, the gB homolog of MDV was expressed in insect cells by a recombinant baculovirus, and it was characterized to determine its molecular and antigenic properties. The expressed recombinant protein had three molecular sizes (88 to 110, 58, and 49 kDa) and was recognized by antisera from chickens inoculated with each of the three serotypes of MDV. By immunofluorescence analysis, it was shown that the protein was expressed in the cytoplasm and on the surface of the recombinant baculovirus-infected cells. The gB homolog of MDV was processed similarly to pseudorabies virus and varicella-zoster virus with respect to cleavage and the intramolecular disulfide bond between the cleaved products. Interestingly, the expressed protein reacted with monoclonal antibody M51, specific to the B antigen (gp100, gp60, gp49) of MDV, although the locations of the gene encoding the B antigen and of the gene encoding the gB homolog were reported to be different. Moreover, competitive experiments revealed that anti-gB homolog serum and monoclonal antibody M51 recognized the same molecules. From these results, the gB homolog and the B antigen of MDV seem to be the same glycoprotein.

Neutralizing antibodies induced by recombinant vaccinia virus expressing varicella-zoster virus gpIV

Monoclonal antibodies generated against varicella-zoster virus (VZV) glycoprotein I (gpI) also recognize VZV gpIV (A. Vafai, Z. Wroblewska, R. Mahalingam, G. Cabirac, M. Wellish, M. Cisco, and D. Gilden, J. Virol. 62:2544-2551, 1988). To determine whether the virus-neutralizing activity of these antibodies belongs to gpI, gpIV, or both, the open reading frame encoding gpIV was inserted into the vaccinia virus genome. Immunoprecipitation of recombinant vaccinia virus-infected cells with anti-gpIV monoclonal antibody yielded synthesis and processing of gpIV similar to those expressed in VZV-infected cells. Antibodies raised against VVgpIV in a rabbit recognized both native gpI and gpIV and neutralized VZV infectivity. In addition, antibodies raised against recombinant vaccinia virus carrying VZV gpI neutralized VZV infection. These results indicate a structural relationship between VZV gpI and gpIV and show that gpI and gpIV each induce virus-neutralizing antibody.

Epitopes functional in neutralization of varicella-zoster virus

By competition neutralization assay using monoclonal antibodies (MAbs) to varicella-zoster virus (VZV) glycoproteins (gps), we attempted to determine the topographical relationship of epitopes which are functional in VZV neutralization. MAbs against gpI interfered moderately to strongly with neutralization of MAbs against gpIII, and one antigenic domain with two distinct epitopes was identified on gpIII. Competition neutralization assays performed with MAbs to gpI revealed at least three distinct antigenic domains: the first contained two complement-dependent neutralizing epitopes; the second contained five complement-dependent neutralizing, overlapping epitopes and one nonneutralizing, nonoverlapping epitope; and the third contained one complement-enhanced neutralizing epitope. Competition neutralization assays performed with MAbs to gpIV showed one antigenic domain with two distinct epitopes which competed with nonneutralizing gpI MAbs. gpII did not interfere with neutralization of gpI, gpIII, or gpIV. Our data suggest that neutralizing and nonneutralizing MAbs can interfere with the action of viral neutralization either by inhibition or by enhancement. This report describes the epitope mapping of VZV gps by a functional biological assay.

Acyclovir treatment for varicella does not lower gpI and IE-62 (p170) antibody responses to varicella-zoster virus in normal children

The varicella-zoster virus (VZV) membrane glycoprotein gpI elicits a major immunoglobulin G antibody response after naturally acquired VZV infection; antibody to a nonglycosylated immediate-early protein, IE-62 (p170), represents a response to a nonmembrane VZV component. We evaluated antibody response to VZV gpI and IE-62 (p170) at 28 days and 1 year following infection in 34 children (ages 5 to 16 years) enrolled in a randomized placebo-controlled study of oral acyclovir for the treatment of varicella. All children were VZV antibody negative at enrollment, were previously healthy, and had laboratory-documented varicella. Compared with placebo recipients, acyclovir recipients had lower geometric mean titers by the fluorescent antibody to membrane antigen technique at 28 days (620 versus 836) but similar titers at 1 year (122 versus 122). All children had antibodies to gpI and IE-62 detectable by enzyme-linked immunosorbent assay at 28 days and 1 year. No difference in gpI at 28 days compared with 1 year was noted in acyclovir recipients. No difference in antibody to IE-62 (p170) was noted when acyclovir and placebo recipients were compared at either 28 days or 1 year. Antibody responses to gpI and IE were similar when children were stratified by age (5 to 6 years, 7 to 11 years, 12 to 16 years). A short course of oral acyclovir for the treatment of varicella did not affect antibody responses to gpI or IE-62 (p170) in healthy children at 28 days and 1 year following varicella.

The glycoprotein products of varicella-zoster virus gene 14 and their defective accumulation in a vaccine strain (Oka)

Many characteristics of the putative protein encoded by varicella-zoster virus (VZV) open reading fram (ORF) 14 indicate that it is a glycoprotein, which has been designated gpV. To identify the protein products of the gene, the coding sequences were placed under the control of the vaccinia virus p7.5 promoter and recombinant vaccinia viruses were constructed. Heterogeneous polypeptides with molecular weights of 95,000 to 105,000 (95K to 105K polypeptides) were expressed in cells infected by a vaccinia virus recombinant (vKIP5) containing ORF 14 from VZV Scott but were not expressed by control vaccinia viruses. These polypeptides were recognized by antibodies present in human sera that contained high levels of anti-VZV antibodies. Conversely, antisera raised in rabbits inoculated with vKIP5 reacted specifically with heterogeneous 95K to 105K polypeptides present in VZV Scott-infected but not uninfected cells; these polypeptides show a patchy plasma membrane fluorescence pattern in VZV Scott-infected cells. These same antisera neutralized VZV strain Scott infectivity in the absence of complement. Endoglycosidase F treatment of isolated gpV polypeptides and tunicamycin treatment of cells infected with the vKIP5 recombinant indicated that the polypeptides were glycosylated. Three sets of data imply that the VZV strain Oka, which has been used to produce a live attenuated virus vaccine, accumulates low levels of gpV polypeptides relative to wild-type strains: (i) blocking of antibodies in human sera with excess VZV Oka-infected cell antigen yielded residual antibodies which were reactive with the 95K to 105K gpV polypeptides expressed in cells infected by VZV strain Scott and by the vKIP5 vaccinia virus recombinant, but not with Oka-infected cell polypeptides; (ii) antisera raised to vKIP5 detected very low levels of reactive polypeptides made in VZV Oka-infected cells and neutralized VZV Oka virus much less efficiently than VZV Scott; and (iii) comparisons of the reactivity of sera from live attenuated virus vaccine vaccinees with sera derived from patients recovering from wild-type infections indicated greatly reduced levels of gpV-specific antibodies in some vaccinees.

Neutralizing antibodies specific for glycoprotein H of herpes simplex virus permit viral attachment to cells but prevent penetration

Monoclonal antibodies specific for gH of herpes simplex virus were shown previously to neutralize viral infectivity. Results presented here demonstrate that these antibodies (at least three of them) block viral penetration without inhibiting adsorption of virus to cells. Penetration of herpes simplex virus is by fusion of the virion envelope with the plasma membrane of a susceptible cell. Electron microscopy of thin sections of cells exposed to virus revealed that neutralized virus bound to the cell surface but did not fuse with the plasma membrane. Quantitation of virus adsorption by measuring the binding of purified radiolabeled virus to cells revealed that the anti-gH antibodies had little or no effect on adsorption. Monitoring cell and viral protein synthesis after exposure of cells to infectious and neutralized virus gave results consistent with the electron microscopic finding that the anti-gH antibodies blocked viral penetration. On the basis of the results presented here and other information published elsewhere, it is suggested that gH is one of three glycoproteins essential for penetration of herpes simplex virus into cells.

Existence of similar antigenic-sites on varicella-zoster virus gpI and gpIV

We previously identified the antibody-binding site of a monoclonal antibody (mAb 79.0) on varicella-zoster virus (VZV) glycoprotein I (gpI) and showed that this monoclonal antibody binds to both VZV gpI and gpIV (Vafai et al., J. Virol. 62, 2544, 1988). In this study, a synthetic peptide comprising the mAb 79.0 binding site (designated el) was prepared and anti-peptide antibodies (RAnti-el) were raised in rabbit. RAnti-el recognized the primary translation products encoded by VZV genes 67 (gpIV) and 68 (gpI). To further localize the binding site of RAnti-el on VZV gpIV, the gpIV gene cloned in pGEM transcription vector was cleaved at different locations to generate four truncated DNA fragments. RNA was transcribed from each truncated gpIV fragment, translated in vitro and immunoprecipitated with RAnti-el. The results indicated that RAnti-el binds an antigenic determinant within the first 153 amino acid residues on the primary translation product of VZV gpIV. In addition, RAnti-el recognized the high-mannose intermediate but not the mature from of gpI in the infected cells or the translation products of gpIV glycosylated in vitro in the presence of canine microsomal membrane. These results: (a) confirmed the existence of a shared antigenic determinant on both VZV gpI and gpIV; and (b) indicated that the addition of terminal sugar modification may influence the conformation of gpI and gpIV with respect to the antigenic determinant recognized by RAnti-el.

Identification of a neutralizing epitope on glycoprotein gp58 of human cytomegalovirus

Human cytomegalovirus contains an envelope glycoprotein of 58 kilodaltons (gp58). The protein, which is derived from a glycosylated precursor molecule of 160 kilodaltons via proteolytic cleavage, is capable of inducing neutralizing antibodies. We have mapped the epitopes recognized by the neutralizing monoclonal antibody 7-17 and a second antibody (27-287) which is not neutralizing. Overlapping fragments of the carboxy-terminal part of the open reading frame coding for gp58 were expressed in Escherichia coli as beta-galactosidase fusion proteins. The reactivities of antibodies 7-17 and 27-287 were determined by Western blot (immunoblot) analysis. Both antibodies recognized sequences between amino acids 608 and 625 of the primary gp58 translation product. The antibodies almost completely inhibited one another in a competitive binding assay with intact virus as antigen. Moreover, antibody 27-287 was able to inhibit the complement-independent neutralizing activity of antibody 7-17.

The human cytomegalovirus strain Towne glycoprotein H gene encodes glycoprotein p86

The gene encoding the glycoprotein H (gH) homologue of CMV strain Towne was cloned, sequenced, and expressed. The predicted 742 amino acid gH protein had characteristics typical of a membrane glycoprotein including hydrophobic signal and transmembrane domains and six possible N-linked glycosylation sites. The CMV (Towne) gH gene had a 95% nucleotide identity and a 96.6% amino acid identity with the CMV (AD169) gH gene, as described by M. P. Cranage, G. L. Smith, S. E. Bell, H. Hart, C. Brown, A. T. Bankier, P. Tomlinson, B. G. Barrell, and T. C. Minson (1988, J. Virol. 62, 1416-1422). Transcriptional analysis of the gH gene revealed that the 2.9-kilobase (kb) gH transcript was not detected until late after CMV infection, indicating that the kinetics of gH expression were typical of the late class of CMV genes. The gH gene was expressed in COS cells using a vector in which transcription was driven by the SV40 early promoter. The expression of gH was detected by immunofluorescence using the virus neutralizing murine monoclonal antibody 1G6, which is specific for an 86-kilodalton (kDa) CMV virion membrane protein (p86). Amino acid sequence analysis of p86 tryptic peptides revealed sequence identity with peptides from the deduced gH amino acid sequence, confirming that the gH gene encodes p86. These results indicate that CMV gH can induce virus neutralizing antibodies and establishes gH as a candidate antigen for a subunit vaccine against CMV.

Transcription mapping of glycoprotein I (gpI) and gpIV of varicella-zoster virus and immunological analysis of the gpI produced in cells infected with the recombinant vaccinia virus

In order to determine the transcripts of gpI and gpIV of varicella-zoster virus (VZV), RNA was isolated from human embryonic fibroblast cells infected with VZV and Northern blot analysis was carried out using cloned DNA probes of unique short region including gpI and gpIV genes. The analysis of RNA revealed two discrete transcripts of 3.6 and 2.15 kilobases (kb) and three transcripts of 3.6, 2.9, and 1.6 kb which hybridized to DNA probes covering the gpI and gpIV region, respectively. Next, mRNAs were hybrid-selected, translated in vitro and the polypeptide products were immunoprecipitated with antibodies against these glycoproteins. The polypeptides with a molecular weight of 70,000 (70K) and 37K which were in vitro translational products of mRNA hybrid-selected with the DNA clone covering gpI and gpIV were detected using antibodies against gpI and gpIV, respectively. The result showed that the 70K polypeptide is presumably the translational product of 2.15 kb mRNA and the 37K polypeptide is that of 1.6 kb mRNA. DNA fragment encoding gpI or gpIV was inserted into vaccinia virus DNA and the recombinant viruses, mO74 (gpI) and mO39 (gpIV), were used for immunological analysis. In consequence, the gpI derived from cells infected with mO74 showed antigenic characteristics similar to those of gpI from VZV-infected cells as determined from the immunoprecipitation pattern, although the molecular weight of each polypeptide was different, and antibody produced in rabbits infected with recombinant virus had a high neutralizing activity, when the reaction was performed with complement. This suggested that gpI plays an important role for protection and recovery from VZV infection.

Recognition of similar epitopes on varicella-zoster virus gpI and gpIV by monoclonal antibodies

Two monoclonal antibodies, MAb43.2 and MAb79.0, prepared against varicella-zoster virus (VZV) proteins were selected to analyze VZV gpIV and gpI, respectively. MAb43.2 reacted only with cytoplasmic antigens, whereas MAb79.0 recognized both cytoplasmic and membrane antigens in VZV-infected cells. Immunoprecipitation of in vitro translation products with MAb43.2 revealed only proteins encoded by the gpIV gene, whereas MAb79.0 precipitated proteins encoded by the gpIV and gpI genes. Pulse-chase analysis followed by immunoprecipitation of VZV-infected cells indicated reactivity of MAb43.2 with three phosphorylated precursor species of gpIV and reactivity of MAb79.0 with the precursor and mature forms of gpI and gpIV. These results indicated that (i) MAb43.2 and MAb79.0 recognize different epitopes on VZV gpIV, (ii) glycosylation of gpIV ablates recognition by MAb43.2, and (iii) gpIV is phosphorylated. To map the binding site of MAb79.0 on gpI, the pGEM transcription vector, containing the coding region of the gpI gene, was linearized, and three truncated gpI DNA fragments were generated. RNA was transcribed from each truncated fragment by using SP6 RNA polymerase, translated in vitro in a rabbit reticulocyte lysate, and immunoprecipitated with MAb79.0 and human sera. The results revealed the existence of an antibody-binding site within 14 amino acid residues located between residues 109 to 123 on the predicted amino acid sequences of gpI. From the predicted amino acid sequences, 14 residues on gpI (residues 107 to 121) displayed a degree of similarity (36%) to two regions (residues 55 to 69 and 245 to 259) of gp IV. Such similarities may account for the binding of MAb79.0 to both VZV gpI and gpIV.

Varicella-zoster virus gpI and herpes simplex virus gE: phosphorylation and Fc binding

gpI, the predominant varicella-zoster virus (VZV) envelope glycoprotein, was shown to be phosphorylated exclusively on serine and threonine residues, and phosphorylated gpI was detected in isolated virions. In cells infected with herpes simplex virus type 1 (HSV-1), a related neurotropic alpha-herpesvirus, HSV gE, the homolog to VZV gpI, and HSV gB, the homolog to VZV gpII, were also phosphorylated. The phosphate on gB and gE was alkali labile and resistant to endo H, suggesting linkage to serine and/or threonine. Although VZV gpI and HSV gE share sequence homology and similar post-translational modifications, no Fc-binding activity similar to that associated with gE was detected for gpI or any of the VZV glycoproteins.

Bovine herpesvirus type 1 gp87 mediates both attachment of virions to susceptible cells and hemagglutination

The 87,000-dalton glycoprotein (gp87) of bovine herpesvirus type 1 (BHV-1) was found to selectively attach to susceptible cells. The attachment of gp87 to the cells was markedly decreased by the prior adsorption of intact virions. Anti-gp87 (site Ia) monoclonal antibody, which inhibited BHV-1 adsorption to the cells and neutralized the virus without complement [Okazaki et al., Virology 250: 260-264], was effective in inhibiting the adsorption of gp87. Only the same antibody was able to inhibit the hemagglutination activity of BHV-1. Other monoclonal antibodies to the glycoproteins of BHV-1, including antibodies directed to sites Ib and Ic on gp87, were ineffective in inhibiting either virus adsorption or hemagglutination. The results of this study indicate that site Ia of gp87 molecule is the critical site of virus attachment for initiation of infection as well as the hemagglutination of BHV-1.

Assembly and processing of the disulfide-linked varicella-zoster virus glycoprotein gpII(140)

Varicella-zoster virus (VZV) specifies the synthesis of at least four families of glycoproteins, which have been designated gpI, gpII, gpIII, and gpIV. In this report we describe the assembly and processing of VZV gpII, a structural protein of an apparent Mr of 140,000, which is the homolog of gB of herpes simplex virus. For these studies, we used two anti-gpII monoclonal antibodies which exhibited both complement-independent neutralization activity and inhibition of virus-induced cell-to-cell fusion. Pulse-chase labeling experiments identified a 124,000-Mr intermediate which was chased to the mature 140,000-Mr product when analyzed in nonreducing gels; in the presence of a reducing agent, the native gp140 was cleaved into two closely migrating species (gp66 and gp68). The biosynthesis of VZV gpII was further analyzed in the presence of the following inhibitors of glycoprotein processing: tunicamycin, monensin, castanospermine, swainsonine, and deoxymannojirimycin. All intermediate and mature forms were digested with endoglycosidases H and F, neuraminidase, and O-glycanase to further define high-mannose, complex, and O-linked glycans. Finally, the addition of sulfate residues was investigated. This characterization of VZV gpII revealed the following results. (i) gp128 and gp124 were early high-mannose forms, (ii) gp126 was an intermediate form with complex N-linked oligosaccharides, (iii) gp130 was a later intermediate with both N-linked and O-linked glycans, and (iv) the mature product gp140 contained a mixture of N-linked and O-linked glycans which were both sialated and sulfated. Further investigations indicated that gpII sulfation was inhibited by tunicamycin and castanospermine but not by deoxymannojirimycin or swainsonine. We also concluded that VZV gpII displayed many biological and biochemical properties similar to those of its herpes simplex virus homolog gB.

Immunization of monkeys with varicella-zoster virus glycoprotein antigens and their response to challenge with simian varicella virus

African green monkeys (Cercopithecus aethiops) were immunized with three intramuscular injections of gpI, gpII, or gpIII glycoprotein antigens of varicella-zoster virus (VZV). Antibody responses to VZV were determined by enzyme-linked immunosorbent assay (ELISA) and to simian varicella virus (SVV) by immunofluorescence and by serum neutralization assays. Two weeks following the third immunization with VZV glycoproteins, the monkeys were challenged by inoculation of SVV. Antibodies to gpII or gpIII partially prevented infection by SVV, while the presence of antibodies to gpI was ineffective in preventing disease induced by SVV challenge. Factors affecting the immunogenicity of these antigens in this model are discussed.

Varicella-zoster virus as a live vector for the expression of foreign genes

The previous demonstration of the efficacy and tolerability of the Oka strain of varicella-zoster virus (VZV) in clinical trials involving vaccination of both normal and immunocompromised individuals has laid the foundation for its use in preventing chickenpox. In this context, VZV could be useful as a vector for vaccinating against other infectious agents as well. As an initial application, a live recombinant VZV expressing Epstein-Barr virus (EBV) membrane glycoproteins (gp350/220) was generated by inserting a gene fusion of the VZV gpI promoter and hydrophobic leader-encoding sequence with the gp350/220 coding sequence into the thymidine kinase (TK) gene of VZV (Oka). Insertion of the foreign DNA into the thymidine kinase gene was demonstrated by Southern blot analysis and the ability of the recombinant virus to replicate in the presence of bromodeoxyuridine. RNA splicing, glycosylation, and plasma membrane presentation of gp350/220 in cells infected with the recombinant virus were similar to those seen in EBV-infected cells. In addition, the expression of VZV-specific glycoproteins was unaltered by the concomitant expression of this large foreign glycoprotein. Thus, VZV can be used as a live viral vector for active immunization against EBV and other pathogens.