Varicella-zoster viral glycoproteins analyzed with monoclonal antibodies

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.

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.

Prevention of postherpetic neuralgia with varicella-zoster hyperimmune globulin

Recovery after an acute attack of herpes zoster is followed by postherpetic neuralgia (PHN) in 9-14% of all patients. Depending on the patient's age, the severity of the acute attack of herpes zoster and the dermatome involved, the incidence of PHN may be as high as 65%. The purpose of our study was to ascertain the incidence of PHN after a prophylactic intravenous injection of varicella-zoster hyperimmune globulin (VZV-IG) (Varitect Biotest Pharma). For this double-blind placebo-controlled randomised investigation we defined PHN as pain confined to the dermatome previously affected by herpes zoster, and we required a pain intensity of at least 15% points on a visual analogue scale (VAS) for this dermatome. The inclusion criteria were the dermatological diagnosis of herpes zoster together with age over 50 years. On Day 1, 20 patients received a single intravenous infusion of VZV-IG in a dose of 2mL/kg body weight, 20 patients (control group) received a single infusion of human albumin 5% in a dose of 2mL/kg body weight. All patients received acyclovir intravenously in a dose of 15mg/kg body weight per 24h for 5 days. The patients were followed up for a total of 42 days. The incidence of PHN at Day 42 was selected as the main outcome criterion for assessing the efficacy of prophylaxis. On reaching a significant difference between the groups (t test; alpha<0.05) in favour of the active treatment group, prophylaxis of PHN by VZV-IG was assessed as effective. Pain was assessed on a VAS and a NAS. As auxiliary outcome criteria, we used the McGill Pain-Rating Questionnaire in its German version, the revised multidimensional pain scale (RMSS) and the Freiburg symptom list (FBL). All results were assessed by the t test (alpha<0.05). The frequency of PHN in the placebo group was 70% (14/20), in the active treatment group it was 35% (7/20) at Day 42. The results of the McGill test showed the variability of the perception of pain in the placebo group significantly greater. No significant group differences were found in the FBL. Being tested with the RMSS, the patients of the placebo group assessed their pains as significantly "more obstinate" (p=0.047). The results can be summed up by saying that VZV-IG not only reduces the incidence of PHN, but also that in certain respects the patients' assessments of their pain experience were different. In our study we found a 50% reduction in PHN incidence However, the outcome time point of our trial was so close to the acute phase of the zoster illness that spontaneous remissions of PHN still have to be taken into account. Despite the widely varied approaches to the problem, reliably effective therapy, let alone 100% prevention of PHN, is still not feasible.

Human herpesvirus 8 glycoprotein K8.1: expression, post-translational modification and localization analyzed by monoclonal antibody

BACKGROUND

The genome of human herpesvirus 8 (HHV-8) contains at least 84 open reading frames, including the highly immunogenic K8.1. Other studies have determined that K8.1 gene generates at least two spliced transcripts in the HHV-8 infected BCBL-1 cells, termed as glycoprotein (gp)K8.1A and gpK8.1B.

OBJECTIVE

To analyze the expression, post-translational modification and localization of HHV-8 gpK8.1 by monoclonal antibody (mAb).

STUDY DESIGN

Mabs to HHV-8 produced by conventional hybridization and several clones identified. A mAb was used by various immunological assays to analyze HHV-8 K8.1 proteins in BCBL-1- and Sf9 insect cells.

RESULTS

MAb clone 19B4 identified a 0.75-kb insert from the lambdaZAP cDNA expression library of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced BCBL-1 cells. Sequence analysis revealed that the cDNA insert corresponds to the published spliced ORF K8.1 mRNA of HHV-8. By immunofluorescence assay, the mAb stained the cell membrane, cytoplasm and perinuclear region of TPA induced BCBL-1 cells and showed no cross-reactivity with other herpesviruses. By immunoblotting assay, mAb 19B4 reacted with two species polypeptides giving a diffuse band with rMW from 42 to 64 kDa (gpK8.1A) and two closely migrating polypeptides of rMW 35/37 kDa (gpK8.1B). Both species were labeled by [14C]glucosamine, indicating that they are glycosylated and only gpK8.1A was detected in the virions. Expression of the full length K8.1 derived from cDNA in baculovirus system confirmed that these two glycoproteins are encoded by K8.1 gene. Enzymatic deglycosylation with endoF/peptide-N-glycosidase F, led to the reduction of rMW of both polypeptides whereas deglycosylation with O-glycosidase led only the reduction of rMW of K8.1A.

CONCLUSION

The mAb 19B4 reacts specifically with BCBL-1 and Sf9 cells infected with recombinant baculovirus containing HHV-8 K8.1 gene. In several assays the mAb reacts with gpK8.1A and gpK8.1B. Only the mature spliced gpK8.1A is incorporated into virion. Enzymatic deglacosylation determined that gpK8.1A is N- and O-glycosylated, whereas gpK8.1B may lack O-glycosylation.

Expression of neutralizing recombinant human antibodies against Varicella Zoster virus for use as a potential prophylactic

Chickenpox is a highly infectious disease that can be life-threatening to certain groups such as the newborn of nonimmune mothers and immunocompromised patients. At present, prophylactic treatment of individuals at risk involves the use of a polyclonal antibody preparation derived from the pooled sera of hyperimmune donors. While this product is effective, there are problems associated with maintaining supply, which depends on the availability of donors, and the variation of potency between batches. An effective human monoclonal preparation would be of value by providing a well-characterized and standardized preparation available on demand. In this study recombinant human anti-varicella zoster virus (VZV) monoclonals were generated from the mRNA of unstable anti-VZV secreting heterohybridoma cell lines, and characterized according to their molecular weight, isoelectric point, glycosylation, binding to C1q, and efficacy at neutralizing VZV in vitro. In one antibody (AEVZ 5.3) the VH region was grafted from the IgG1 parent antibody onto an IgG3 backbone to determine the effect of isotype on neutralization in vitro. Antibodies were expressed from NSO cells at concentrations of 3-24 microg/mL and contained the expected heavy and light chain fragments and N-linked glycan structures. Both AEVZ 5.1 and AVEZ 4 antibodies were IgG1 and recognized the viral coat protein glycoprotein E; both showed complement-independent and complement-enhanced neutralization. Changing the isotype of AEVZ 5.1 from IgG1 to IgG3 (AEVZ 5.3) further enhanced VZV neutralization in the presence of complement, but reduced its neutralization capacity in the absence of complement. Complement enhancement was consistent with our findings that the IgG3 form could bind more molecules of C1q. The results demonstrate the successful use of recombinant methods to generate stable, functional monoclonal antibodies. Modifications of the original antibodies were made with the aim of improving functionality. The resulting cell lines could be used for large-scale production of well-characterized antibodies for therapeutic use.

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.

Varicella-zoster virus (VZV) transcription during latency in human ganglia: detection of transcripts mapping to genes 21, 29, 62, and 63 in a cDNA library enriched for VZV RNA

Information on the extent of virus DNA transcription and translation in infected tissue is crucial to an understanding of herpesvirus latency. To detect low-abundance latent varicella-zoster virus (VZV) transcripts, poly(A)+ RNA extracted from latently infected human trigeminal ganglia was enriched for VZV transcripts by hybridization to biotinylated VZV DNA. After hybridization, the RNA-DNA hybrid was isolated by binding to avidin-coated beads and extensively washed, and the RNA was released by heat denaturation. A lambda-based cDNA library was then constructed from the enriched RNA. PCR and DNA sequencing of DNA extracted from the cDNA library revealed the presence of VZV genes 21, 29, 62, and 63, but not VZV genes 4, 10, 40, 51, and 61, in the enriched cDNA library. These findings confirm the detection of VZV gene 29 and 62 transcripts on Northern (RNA) blots prepared from latently infected human ganglia (J.L. Meier, R.P. Holman, K.D. Croen, J.E. Smialek, and S.E. Straus, Virology 193:193-200, 1993) and the presence of VZV gene 21 transcripts in a cDNA library from mRNA of latently infected ganglia (R.J. Cohrs, K. Srock, M.B. Barbour, G. Owens, R. Mahalingam, M.E. Devlin, M. Wellish and D.H. Gilden, J. Virol. 68:7900-7908,1994) and also reveal, for the first time, the presence of VZV gene 63 RNA in latently infected human ganglia.

Varicella-zoster virus (VZV) transcription during latency in human ganglia: prevalence of VZV gene 21 transcripts in latently infected human ganglia

Reverse transcriptase-linked PCR was used to determine the prevalence of varicella-zoster virus (VZV) gene 21 transcription in latently infected human ganglia. Under conditions wherein reverse transcriptase-linked PCR detected > or = 1,000 transcripts, VZV gene 21 RNA, but not VZV gene 40 RNA, was found in ganglia but not other tissues from five of seven humans.

Inhibition of varicella-zoster virus glycoprotein expression by peripheral blood mononuclear cells

The effect of peripheral blood mononuclear cells (PBMC) on expression of varicella-zoster virus (VZV) glycoproteins (Gps) was analyzed by flow cytometry. PBMC from VZV seropositive and seronegative donors and supernatant of PBMC co-cultured with VZV-infected human embryonic fibroblasts reduced VZV Gp expression. Neutralization of supernatant fluid with mixture of anti-interferons (IFN)-alpha, -beta, -gamma, and tumor necrosis factor (TNF)-alpha partially reduced inhibitory activity of supernatant on VZV Gp expression. Deletion of natural killer (NK) cells and adherent cells from PBMC reduced inhibitory activity of PBMC on VZV Gp expression. These results suggest that IFN-alpha, -beta, -gamma, TNF-alpha and other soluble factors released from NK cells and monocytes by co-cultivation with VZV-infected fibroblasts inhibit VZV Gp expression.

Varicella-zoster virus (VZV) transcription during latency in human ganglia: construction of a cDNA library from latently infected human trigeminal ganglia and detection of a VZV transcript

The entire varicella-zoster virus (VZV) genome appears to be present in latently infected human ganglia, but the extent of virus DNA transcription is unknown. Conventional methods to study virus gene transcripts by Northern (RNA) blotting are not feasible, since ganglia are small and VZV DNA is not abundant. To circumvent this problem, we prepared radiolabeled cDNA from ganglionic RNA, hybridized it to Southern blots containing VZV DNA, and demonstrated the presence of a transcript within the SalI C fragment of the virus genome (R. Cohrs, R. Mahalingam, A. N. Dueland, W. Wolf, M. Wellish, and D. H. Gilden, J. Infect. Dis. 166:S24-S29, 1992). To further map VZV transcripts, in the work described here we constructed a cDNA library from poly(A)+ RNA obtained from latently infected human ganglia. Phage DNA isolated from the library was used in PCR amplifications to detect VZV-specific inserts. The specificity of the PCRs was provided by selection of a primer specific for VZV gene 17, 18, 19, 20, or 21 and a second vector-specific primer. VZV gene 21-specific sequences were identified by PCR amplification. The PCR product contained the XhoI cloning site and poly(A)+ sequences between vector and VZV gene 21 sequences. The sequence motif at the 3' end of VZV gene 21, determined by cloning and sequencing of the PCR product, consisted of 49 to 51 nucleotide bases of 3'-untranslated DNA, the termination codon for the VZV gene 21 open reading frame, and DNA sequences reading into the VZV gene 21 open reading frame.

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.

Zoster sine herpete, a clinical variant

Two otherwise healthy immunocompetent men, ages 62 and 66 years, experienced years of radicular pain without zoster rash. An extensive search for systemic disease and malignancy was negative. Varicella-zoster virus DNA, but not herpes simplex virus DNA, was found in the cerebrospinal fluid of the first patient 5 months after the onset of pain, and in the second patient 8 months after the onset of pain. Prolonged radicular pain without zoster rash combined with the presence of varicella-zoster virus in the cerebrospinal fluid indicates that both men had zoster sine herpete, and strongly supports this syndrome as a clinical variant.

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.

Unsuspected varicella-zoster virus encephalitis in a child with acquired immunodeficiency syndrome

We report a case of progressive encephalitis caused by varicella-zoster virus (VZV) in an adolescent with hemophilia and acquired immunodeficiency syndrome but without cutaneous signs of VZV infection. Magnetic resonance imaging of the brain demonstrated an abnormally increased periventricular signal in T2-weighted images. Infection with VZV was proved by in situ hybridization and immunofluorescence staining of brain tissue, which showed histologic evidence of herpesvirus infection. Encephalitis caused by infection with VZV is a potentially treatable complication of acquired immunodeficiency syndrome and requires a high index of suspicion for diagnosis.

Infection of human fetal dorsal root neurons with wild type varicella virus and the Oka strain varicella vaccine

The relative ability of a varicella-zoster virus (VZV) clinical isolate and a live attenuated VZV vaccine strain (Oka) to infect human neurons was determined in vitro. VZV infection of neurons prepared in culture from dorsal root ganglia of fetuses was assessed using an infectious center assay. Cultures were infected with 50-5,000 pfu of either VZV and assayed at either 24 or 48 hours post-VZV infection. Cultures infected with the clinical VZV isolate had seven-fold more infected neurons than cultures infected with the vaccine strain VZV.

Quantitation of latent varicella-zoster virus DNA in human trigeminal ganglia by polymerase chain reaction

Competitive polymerase chain reaction was used to quantitate latent varicella-zoster virus (VZV) DNA in human trigeminal ganglia. Ganglionic DNA from five subjects was amplified with oligonucleotide primers specific for VZV gene 28. Two of the samples were also analyzed with primers specific for VZV gene 62. Our results indicated that there are 6 to 31 copies of the VZV genome in every 100,000 ganglionic cells.

Comparative immunohistochemical study of herpes simplex and varicella-zoster infections

Herpes simplex (HSV) and varicella-zoster (VZV) skin infections share so many histological similarities that distinguishing between them may prove to be impossible. We developed and characterized a new monoclonal antibody, VL8, IgG kappa isotype, directed to the VZV envelope glycoprotein gpI. Immunohistochemistry with VL8 appeared highly sensitive and specific on formalin-fixed paraffin-embedded biopsies and a clear-cut distinction between HSV and VZV infections was possible. The pattern of VL8 immunolabelling in VZV infections was strikingly different from that found in HSV infections studied with polyclonal antibodies to HSV I and II. Double immunolabelling revealed the VL8 positivity of sebaceous cells, endothelial cells, Mac 387- and CD68-positive monocyte-macrophages, and factor XIIIa-positive perivascular, perineural and interstitial dendrocytes. Intracytoplasmic VL8 labelling of endothelial cells and perivascular dendrocytes was found at the site of leukocytoclastic vasculitis.

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.

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.

Comparison of biotinylated DNA and RNA probes for rapid detection of varicella-zoster virus genome by in situ hybridization

We describe a general method for the production of nonisotopic DNA and RNA probes for the detection of the varicella-zoster virus (VZV) genome by in situ hybridization. VZV DNA was extracted from purified viral nucleocapsids, cleaved with restriction enzyme (RE) BamHI, and cloned into plasmid pBR322 by the standard vector insert procedure. We cloned over 85% of the VZV genome and obtained 18 recombinants. Plasmids containing the B, F, G, H, and J fragments of VZV DNA were labeled by the nick translation method with biotin-11-dUTP as the dTTP analog. Additionally, the B fragment was cleaved with RE AvaI, subcloned into the plasmid pGEM-4 transcription vector, and subsequently linearized with REs PstI and EcoRI. RNA was transcribed with T7 or SP6 polymerase, with a substitution of allylamine-UTP as the UTP analog, and labeled with epsilon-caproylamidobiotin-N-hydroxysuccinimide ester. The DNA and RNA probes were used under full-stringency conditions for in situ hybridization with alkaline phosphatase as the detector and 5-bromo-4-chloro-3-indolyl phosphate-Nitro Blue Tetrazolium as the substrate. When tested under comparable conditions, the RNA probe was slightly more sensitive than was the DNA probe: both probes showed homology only with VZV-infected cells and clinical tissues and not with the other herpesviruses. Probes prepared from variable regions of the genome (fragments F and J) performed as well as did those from conserved regions (fragments B. G. and H). Biotinylated probes have distinct advantages over isotopic probes and retain their full potency for more than 2 years when stored properly.

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.

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.

Monoclonal antibody to immediate early protein encoded by varicella-zoster virus gene 62

Monoclonal antibodies (mAbs) were prepared against varicella-zoster virus (VZV)-infected cell proteins, and 10 mAbs which reacted with nuclear antigens were selected. These mAbs recognized a major 175-180 kDa and three minor VZV-specific phosphoprotein species. Immunofluorescence staining of VZV-infected cells showed that the 175-180 kDa protein was synthesized within 6 h after infection. The synthesis of this protein was inhibited by cycloheximide (CH); however, reversal of CH treatment and addition of actinomycin D (ActD) resulted in the synthesis of the 175-180 kDa protein. To determine whether the 175-180 kDa protein seen in the infected cells is encoded by VZV immediate early (IE) gene 62, the predicted open reading frames of VZV genes 61 and 62 were cloned into pGEM transcription vectors. RNA was transcribed from each gene, translated in vitro and immunoprecipitated with a mAb which recognizes a major 175-180 kDa and three minor proteins. The reactivity of the in vitro translation products encoded by gene 62 with this mAb suggested that the 175-180 kDa protein is encoded by VZV IE gene 62.

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.

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.

Expression of varicella-zoster virus in blood mononuclear cells of patients with postherpetic neuralgia

Postherpetic neuralgia (PHN), the most frequent complication of varicella-zoster virus (VZV) reactivation, is characterized by pain that persists for greater than 1 mo and often for years after zoster rash. To examine whether PHN might be related to reactivation of VZV, blood mononuclear cells of patients with PHN were tested for the presence of VZV DNA and proteins. VZV DNA was detected in the mononuclear cells of one PHN patient. VZV-specific proteins were detected in mononuclear cells of two acute-varicella patients, one acute zoster patient, and six elderly patients with PHN, but these VZV-specific proteins were not detected in three elderly zoster patients without PHN. Furthermore, pulse-chase experiments revealed further processing or degradation of VZV-specific proteins in the mononuclear cells. These findings strongly suggest that persistence, reactivation, and expression of VZV may result in PHN.

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.

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.

Varicella-zoster virus infection of human mononuclear cells

Varicella-zoster virus (VZV) DNA was detected in mononuclear cells (MNC) of 7 humans with acute zoster 1-23 days after the onset of skin lesions. To further study the interaction of VZV with human MNC, cells obtained from seropositive normal donors were infected with VZV and analyzed for the presence of viral DNA and proteins. VZV-DNA was detected in T, B, and OKM 1 (monocyte-macrophage) positive cells, and virus-specific proteins were demonstrated by indirect immunofluorescence and immunoprecipitation. Hybridization studies revealed that VZV-DNA did not replicate in human MNC.

Hybridomas producing human monoclonal antibodies against varicella-zoster virus

Hybridomas producing human monoclonal antibodies (mAb) against varicella-zoster virus (VZV) were generated by fusing human splenic lymphocytes with mouse myeloma cells. Before cell fusion, lymphocytes were stimulated in vitro with viral antigens and pokeweed mitogen. This combination synergistically increased the generation of VZV-specific hybridomas. Five established hybridomas have been stably producing mAb for at least 9 months. These mAb, designated V1, V2, V6, V8 and V9, were of the IgG1, lambda isotype. They bound to all 6 tested VZV strains but not to other herpes viruses, with the exception that V1 bound to herpes simplex virus (HSV) as well as VZV. Immunoprecipitation analysis showed that V1, V6 and V9 recognized glycoprotein gpII, whereas V2 and V8 recognized gpI. In addition, V1 reacted with the gB glycoprotein of HSV. All these mAb neutralized viral infectivity. The neutralizations by V2 and V8 were more effective and more complement dependent than those by V1, V6 and V9. Immunofluorescence tests revealed that all these mAb bound to the surface membrane of VZV-infected cells. These results suggest that cell fusion between in vitro stimulated lymphocytes and mouse myeloma cells is a reliable method for the generation of hybridomas capable of stable production of human mAb. The human mAb thus developed may provide a new means of passive immunization of humans against VZV infection.

Varicella-zoster virus infection of human sensory neurons

Primary varicella-zoster virus (VZV) infection of humans may result in latent infection of sensory neurons in the peripheral nervous system. To examine the interaction of VZV with the sensory neuron we infected immunochemically defined human neurons with cell-associated VZV. Utilizing double-label immunofluorescence technology, a VZV-specific glycoprotein and a nonglycosylated phosphoprotein were detected in human fetus dorsal root ganglion (DRG) neurons, as defined by the presence of the neuron-specific enolase isoenzyme and the A2B5 ganglioside antigen, respectively. In addition to VZV antigen expression, progressive virus-induced cytopathic damage (neuronal enlargement and nuclear granulation of a fraction of the neuron population) was evident. As determined by transmission electron microscopy, VZV-infected human fetus DRG neurons contained empty and complete nucleocapsids with numerous pleomorphic virus particles in the cytoplasm, often in association with vacuoles. Although virus-specific antigen expression, particle synthesis, and cytopathic effects were observed in the human neuron population, neurons were less susceptible to VZV-induced cytopathic damage than supporting nonneuronal cells, suggesting neuronal modulation of VZV infection in vitro. This system provides the first model to examine the neuron- and virus-specific gene(s) and gene product(s) pertinent to the interaction of VZV with the human neuron.

Identification and structure of the gene encoding gpII, a major glycoprotein of varicella-zoster virus

The genome of varicella-zoster virus (VZV) encodes three major families of glycoproteins (gpI, gpII, and gpIII). mRNA from VZV-infected cells was hybrid selected using a library of VZV recombinant plasmids and translated in vitro; polypeptide products were immunoprecipitated by polyclonal monospecific guinea pig antibodies to gpII. The mRNA encoding a 100-kD polypeptide precipitable by anti-gpII antibodies mapped to the HindIII D fragment near the center of the UL region. DNA sequence analysis of this region of the VZV genome revealed a 2.6-kbp open reading frame (ORF) potentially encoding a 98-kDa polypeptide possessing the characteristics of a glycoprotein. The 100-kDa polypeptide was specified by mRNA isolated by hybrid selection using a plasmid containing part of the 2.6-kbp ORF, and immunoprecipitation of this protein by anti-gpII antibodies and by convalescent zoster serum was blocked specifically by purified gpII. We conclude that the 2.6-kbp ORF encodes gpII. The imputed primary amino acid sequence of gpII shows a high degree of homology to that of herpes simplex virus type 1 (HSV-1) gB, a result consistent with the equivalent map locations of the respective genes in the HSV and VZV genomes and with the recently reported serological cross-reactivity of HSV-1 gB and VZV gpII. Unlike the mature gene products of gB, those of gpII have been described as a pair of glycoproteins with approximate molecular weights of 60 kDa in reducing gels, products of a single glycoprotein species with approximate mol mass of 125-140 kDa in nonreducing gels. Amino-terminal sequences of purified gpII were determined and compared to the imputed amino acid sequence. This comparison implies that the primary translational product is cleaved approximately into halves in vivo and suggests that mature gpII is a disulfide-linked heterodimer.

Polypeptides encoded by varicella-zoster virus unique short sequences

The SalI-I and K DNA fragments which lie within the unique short sequences (Us) and contain a portion of the inverted repeat sequences (IRs/TRs) of varicella-zoster virus (VZV) DNA were cloned in an in vitro transcription vector system (pGEM-2). RNA was transcribed from both strands, translated in vitro and analyzed by SDS-PAGE. The results showed that SalI-I and K each codes for three primary translation products. Polypeptides with Mrs of 19,000 (19K), 47K, 93K/90K are encoded by SalI-I and polypeptides of 12K, 19K, and 50K are encoded by SalI-K. These results are consistent with the predicted genetic expression of the VZV SalI-I and SalI-K DNA fragments.

New common nomenclature for glycoprotein genes of varicella-zoster virus and their glycosylated products

The accumulation of recent data concerning the reactivity of monoclonal antibodies with particular varicella-zoster virus (VZV) glycoproteins and the mapping of several of their respective genes on the VZV genome has led to a unified nomenclature for the glycoprotein genes of VZV and their mature glycosylated products. Homologs to herpes simplex virus glycoprotein genes are noted.

Neutralization epitope of varicella zoster virus on native viral glycoprotein gp118 (VZV glycoprotein gpIII)

Varicella-zoster virus (VZV) specifies the formation of several glycoproteins, including a 118,000-Da mature structural product (gp118). The biologic and biochemical properties of gp118 were studied after production of murine monoclonal antibodies to both a lowpassage laboratory strain (VZV-32) and an attenuated vaccine strain (VZV-Oka). Structural analyses performed with the three glycosidases endo-beta-N-acetylglucosaminidase H (endoglycosidase H), endo-beta-N-acetylglucosaminidase F (endoglycosidase F), and endo-alpha-N-acetylgalactosaminidase demonstrated that gp118 was predominantly an N-linked complex type glycoprotein built upon a polypeptide backbone of approximately 79,000 Da. Sialic acid residues were present on the mature glycoprotein, but these terminal sugars were absent from the partially glycosylated intermediate forms recovered from monensin-treated infected cultures. Unlike another VZV-specified glycoprotein gp98, no new oligosaccharide moieties were observed on gp118 after addition of tunicamycin to VZV-infected cultures. By plaque reduction assays with a panel of monoclonal antibodies, we defined an epitope on this glycoprotein which elicited a complement-independent neutralizing antibody response of high magnitude. The epitope was highly conserved, since it was present on a laboratory VZV strain, wild type isolates, as well as the attenuated vaccine strain (VZV-Oka). Competitive blocking experiments with the same anti-gp118 monoclonal antibodies indicated that four neutralizing antibodies were directed against similar or identical epitopes whereas one nonneutralizing antibody reacted with a different antigenic site. Thus, this study demonstrates the presence of an immunodominant neutralization epitope on native viral glycoprotein gp118. Under a new consensus nomenclature, this glycoprotein will be designated VZV gpIII.

Induction of neutralizing antibody against varicella-zoster virus (VZV) by VZV gp3 and cross-reactivity between VZV gp3 and herpes simplex viruses gB

Glycoprotein gp3 (64K) is one of the major proteins specified by varicella-zoster virus (VZV). This glycoprotein was purified on an immunoadsorbent consisting of monoclonal antibody (clone 8) against gp3 linked to protein A-Sepharose. Rabbits were then immunized with the purified antigen to obtain monospecific antisera against gp3. The monospecific antisera and monoclonal antibody immunoprecipitated polypeptides with the same molecular weights of approximately 64,000 (64K), 106K, and 116K from a lysate of labeled cells infected with VZV. The monoclonal antibodies against gp3 did not have neutralizing activity against VZV, but anti-gp3 monospecific sera neutralized VZV infectivity. The antigenic relation of VZV to herpes simplex virus (HSV) was investigated by the immunofluorescent test, immunoprecipitation followed by analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the neutralizing antibody test with monoclonal antibodies and monospecific antisera. In the indirect immunofluorescent test, the cytoplasm of cells infected with HSV-type 1 or HSV-type 2 was stained with anti-gp3 monospecific antiserum but not with anti-gp3 monoclonal antibodies. This serum also precipitated the polypeptides of HSV-type 1 and HSV-type 2 with molecular weight of approximately 120,000, possibly corresponding to gB of HSV-1 or HSV-2, and this immunoprecipitation was blocked by anti-gB monoclonal antibody. However, anti-gp3 monospecific antisera did not neutralize either HSV-type 1 or HSV-type 2 infectivity. These results suggest that gp3 induces neutralizing antibody against VZV and that it also has a cross-reacting antigenic determinant with gB of HSV.

Transcription mapping of the varicella-zoster virus genome

RNA was isolated from varicella-zoster virus-infected Flow 5000 cells (diploid fibroblasts) at late times after infection. With the use of overlapping DNA probes representing all regions of the varicella-zoster genome, an extensive Northern blot analysis of the RNA was carried out. The analysis revealed at least 58 discrete transcripts ranging in size from approximately 0.8 to 6.5 kilobases. RNAs were found to be homologous to all probes used except for those mapping at approximately map unit 0.3, where no RNA transcripts could be detected. Comparison of the sizes and locations of RNA transcripts mapping in the right-hand ends of the varicella-zoster virus and the herpes simplex virus DNAs shows a number of striking analogies, suggesting their similar genomic organization.

Cross-reactivity between herpes simplex virus glycoprotein B and a 63,000-dalton varicella-zoster virus envelope glycoprotein

Cross-reactive monoclonal antibodies recognizing both herpes simplex virus (HSV) glycoprotein B and a major 63,000-dalton varicella-zoster virus (VZV) envelope glycoprotein were isolated and found to neutralize VZV infection in vitro. None of the other VZV glycoproteins was recognized by any polyclonal anti-HSV serum tested. These results demonstrate that HSV glycoprotein B and the 63,000-dalton VZV glycoprotein share antigenic epitopes and raise the possibility that these two proteins have a similar function in infection.

Varicella-zoster virus envelope glycoproteins: biochemical characterization and identification in clinical material

Varicella-zoster virus (VZV)-infected human foreskin fibroblasts synthesize viral glycoproteins of 125,000 (gp125), 118,000 (gp118), 92,000 (gp92), 63,000 (gp63), 59,000 (gp59), and 47,000 (gp47) Da. In biochemical studies, all of these VZV glycoproteins were shown to contain asparagine-linked (N-linked) oligosaccharide chains and, except for gp125 and gp47, to be sialoglycoproteins. Experiments with endo-beta-N-acetylglucosaminidase H (endo H) demonstrated that gp92 contained only complex type (endo H-resistant) N-linked glycosyl chains, while the other mature glycoproteins contained both high-mannose (endo H-sensitive) and complex-type oligosaccharides. Monoclonal antibodies recognizing multiple glycoproteins, gp63/gp125 or gp92/gp59/gp47, neutralized virus infection, suggesting the glycoproteins were important components of the virus envelope. This was confirmed for gp92/gp59/gp47 by immunoelectron microscopy, which revealed dense staining localized exclusively to the virion envelope and to the plasma membrane of virus-producer cells. The mature forms of all of these glycoproteins were also present in viral material isolated from vesicles of varicella and zoster patients, indicating that in infected individuals the viral glycoproteins are synthesized and processed in a manner similar to that in tissue culture cells.