Recombinant varicella-zoster virus glycoproteins E and I: immunologic responses and clearance of virus in a guinea pig model of chronic uveitis

Analysis of the reliability of rapid diagnostic tests for varicella, including breakthrough cases

In the era of universal varicella vaccination, diagnosis of varicella is challenging, especially for breakthrough cases. We sought to clarify the reliability of direct varicella-zoster virus (VZV) loop-mediated isothermal amplification (LAMP) and DermaQuick® VZV using the immunochromatography technique as rapid diagnostic tests for varicella. In addition, the usefulness of saliva as a sample type for direct LAMP was investigated. Among the 46 enrolled patients with suspected VZV infection, 31 patients (67.3%) were positive for the nucleic acid test based on real-time PCR from skin swab samples. Direct LAMP of skin swabs was positive in 29 (63.0%) of 46 patients. DermaQuick® VZV was positive in 25 (54.3%) of 46 patients. VZV DNA was detected in only 48.4% of oral swabs with the direct LAMP method. With real-time polymerase chain reaction (PCR) as the standard for diagnosing varicella, the sensitivity and specificity of DermaQuick® VZV were 80.7% and 100%, respectively. The sensitivity and specificity of direct LAMP from skin swabs were 93.6% and 100%, respectively. The sensitivity and specificity of real-time PCR for DNA extracted from oral swabs were 74.2% and 93.3%, respectively. Thus, oral swab samples are not suitable for breakthrough varicella diagnosis. Although DermaQuick® VZV is considered the most convenient point-of-care test for varicella, its sensitivity and specificity were lower than those of direct VZV LAMP.

Trend in varicella patients 4 years after implementation of universal two-dose varicella vaccination in Japan

OBJECTIVE

To elucidate the trend and clinical spectrum of virologically diagnosed varicella patients after implementation of universal vaccination as a national immunization program in Japan.

PATIENTS AND METHODS

Study subjects were patients suspected of varicella, less than 15 years of age, who visited 14 pediatric clinics in the Nagoya VZV Study Group from September 2015 to August 2019. Practitioners collected patient samples and information such as backgrounds, clinical symptoms, and previous immunization status. All patients were confirmed as having varicella based on molecular diagnostic assays.

RESULTS

Varicella zoster virus (VZV) DNA was detected in swab samples from 506 (83.1%) of the 609 suspected patients. The 455 varicella patients for whom vaccination status was available were divided into two groups: 180 universal vaccination targets and 275 non-targets. Numbers of monthly varicella patients decreased gradually during the observation period. In the 2016/17 season, the seasonal epidemic of varicella became undetectable in the universal vaccination target group, and starting in the 2017/18 season, it was obscured even in the non-target group. The median age of patients was significantly lower in the universal vaccination target group (3 years) than the non-target group (7 years) (P < 0.001). Vaccination status differed significantly between the two groups (P < 0.001). Most varicella patients were in the non-target group, especially those who had been vaccinated once (60.4%). Frequency of fever (P < 0.001) and number of skin rashes at the time of the first hospital visit (P = 0.001) were significantly higher in the non-target group.

CONCLUSIONS

Although the number of childhood varicella patients declined after implementation of national immunization with two doses of varicella vaccination, sporadic outbreaks still occurred, mainly in the non-universal vaccination target group. Insufficient vaccination of members of this group is likely to be a major reason for small local outbreaks.

Evaluation of glycoprotein E subunit and live attenuated varicella-zoster virus vaccines formulated with a single-strand RNA-based adjuvant

Introduction

Varicella‐zoster virus (VZV), a human alphaherpesvirus 3, elicits both chickenpox and shingles and/or postherpetic neuralgia. A live attenuated vaccine (LAV) and glycoprotein E (gE) subunit vaccine were developed to prevent VZV‐induced diseases. We recently reported that single‐strand RNA (ssRNA) based on the intergenic region of the internal ribosome entry site of cricket paralysis virus (CrPV) is an effective adjuvant for protein‐based and virus‐like particle‐based vaccines. Here, Chinese hamster ovary expression system and an LAV from Oka/SK strains.

Methods

We appraised the adjuvant effect of the same CrPV ssRNA encoding the gE gene formulated in the two vaccines using VZV‐primed C57BL/6 mice and guinea pigs. Humoral immunity and cell‐mediated immunity were assessed by enzyme‐linked immunosorbent assay (ELISA) and ELISPOT in gE subunit vaccine and by ELISA and fluorescent antibody to membrane antigen in LAV.

Results

The gE subunit vaccine‐induced gE‐specific antibodies and CD4⁺ T‐cell responses (indicated by interferon‐γ [IFN‐γ] and interleukin‐2 secretion) in the ssRNA‐based adjuvant containing the VZV gE gene. Therefore, an ssRNA adjuvant combined with gE antigen can trigger the innate immune response and induce an adaptive immune response to ultimately activate humoral and cell‐mediated responses. VZV LAV could also induce VZV‐specific antibodies and IFN‐γ stimulated by LAV, whereas the effect of ssRNA as a vaccine adjuvant could not be confirmed. However, the ssRNA adjuvant increased VZV‐specific neutralizing antibody response.

Conclusions

Taken together, these results highlight that the gE subunit vaccine and LAV developed in this study can be functional VZV vaccines, and ssRNAs appear to function better as adjuvants in a subunit vaccine than in an LAV.

Reliability of direct varicella zoster virus loop-mediated isothermal amplification method for rapid diagnosis of breakthrough varicella

BACKGROUND

Since patients with breakthrough varicella (BV) have mild symptoms, clinical diagnosis is difficult. In high vaccine coverage area, as BV occurs sporadically, point of care test is required for controlling varicella outbreak. In this study, the reliability of varicella zoster virus (VZV)-loop mediated isothermal amplification (LAMP) was evaluated for the rapid diagnosis of BV.

STUDY DESIGN

A total of 328 swab samples collected from patients with suspected varicella were analyzed. For the laboratory diagnosis of varicella, VZV real-time PCR was carried out using DNA extracted from swab samples. Swab samples without DNA extraction were used for VZV-LAMP(direct-LAMP).

RESULTS

VZV infection was diagnosed by real-time PCR in 285 cases, including 105 natural varicella cases and 180 BV cases. VZV DNA was detected in 250 (87.8%) of the 285 cases by direct-LAMP. The presence and duration of fever, number of skin eruptions, and VZV DNA load were significantly lower in BV than natural varicella. The sensitivity of direct-LAMP for the diagnosis of varicella and BV was 93.3% and 84.4%, respectively.

CONCLUSIONS

Direct LAMP was considered to be useful for rapid diagnosis of BV as it has several advantages such as low cost, ease and rapidity, as compared to real time PCR.

Current In Vivo Models of Varicella-Zoster Virus Neurotropism

Varicella-zoster virus (VZV), an exclusively human herpesvirus, causes chickenpox and establishes a latent infection in ganglia, reactivating decades later to produce zoster and associated neurological complications. An understanding of VZV neurotropism in humans has long been hampered by the lack of an adequate animal model. For example, experimental inoculation of VZV in small animals including guinea pigs and cotton rats results in the infection of ganglia but not a rash. The severe combined immune deficient human (SCID-hu) model allows the study of VZV neurotropism for human neural sub-populations. Simian varicella virus (SVV) infection of rhesus macaques (RM) closely resembles both human primary VZV infection and reactivation, with analyses at early times after infection providing valuable information about the extent of viral replication and the host immune responses. Indeed, a critical role for CD4 T-cell immunity during acute SVV infection as well as reactivation has emerged based on studies using RM. Herein we discuss the results of efforts from different groups to establish an animal model of VZV neurotropism.

Laboratory Diagnosis of Breakthrough Varicella in Children

BACKGROUND

Breakthrough varicella (BV) develops in vaccinated persons as a result of infection by wild-type varicella-zoster virus more than 42 days after varicella vaccination. The clinical symptoms are atypical, and clinical diagnosis can be difficult. We investigated laboratory-based diagnostic methods that are relatively simple and highly precise to conduct accurate surveillance.

SUBJECTS AND METHODS

We enrolled 42 patients with suspected BV at 2 pediatric hospitals and performed a real-time polymerase chain reaction (PCR) on the skin lesions to confirm the BV diagnosis. We performed PCR on saliva and blood collected during the acute phase, as well as direct fluorescent antibody (DFA) imaging on lesions, and measured varicella-zoster virus immunoglobulin (Ig) G and IgM during the acute and convalescent phases.

RESULTS

We confirmed the BV diagnosis in 31 of 42 enrolled patients. The sensitivity of DFA imaging of the lesion, and PCR of saliva and blood were 93.5%, 87.1% and 61.3%, respectively. IgM was detected in 12.9% of patients during the acute phase and in 65.5% during the convalescent phase. IgG increased more than 4-fold in 86.2% of patients between the acute and convalescent phases. The sensitivity and specificity of the assay were 83.9% and 81.8%, respectively, when the diagnostic criteria for IgG were set to greater than 20 during the acute phase.

CONCLUSIONS

The gold standard of laboratory-based diagnosis of BV has been the PCR of samples taken from lesions. However, DFA of the lesion showed equivalent sensitivity when compared with PCR. PCR using saliva samples is an effective, noninvasive method of diagnosis. We found that high values of IgG during the acute phase can aid in the diagnosis of BV.

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

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

Varicella-zoster virus glycoproteins B and E are major targets of CD4+ and CD8+ T cells reconstituting during zoster after allogeneic transplantation

BACKGROUND

After allogeneic hematopoietic stem-cell transplantation patients are at increased risk for herpes zoster as long as varicella-zoster virus specific T-cell reconstitution is impaired. This study aimed to identify immunodominant varicella-zoster virus antigens that drive recovery of virus-specific T cells after transplantation.

DESIGN AND METHODS

Antigens were purified from a varicella-zoster virus infected cell lysate by high-performance liquid chromatography and were identified by quantitative mass spectrometric analysis. To approximate in vivo immunogenicity for memory T cells, antigen preparations were consistently screened with ex vivo PBMC of varicella-zoster virus immune healthy individuals in sensitive interferon-γ ELISpot assays. Candidate virus antigens identified by the approach were genetically expressed in PBMC using electroporation of in vitro transcribed RNA encoding full-length proteins and were then analyzed for recognition by CD4(+) and CD8(+) memory T cells.

RESULTS

Varicella-zoster virus encoded glycoproteins B and E, and immediate early protein 62 were identified in immunoreactive lysate material. Predominant CD4(+) T-cell reactivity to these proteins was observed in healthy virus carriers. Furthermore, longitudinal screening in allogeneic stem-cell transplantation patients showed strong expansions of memory T cells recognizing glycoproteins B and E after onset of herpes zoster, while immediate early protein 62 reactivity remained moderate. Reactivity to viral glycoproteins boosted by acute zoster was mediated by both CD4(+) and CD8(+) T cells.

CONCLUSIONS

Our data demonstrate that glycoproteins B and E are major targets of varicella-zoster virus specific CD4(+) and CD8(+) T-cell reconstitution occurring during herpes zoster after allogeneic stem-cell transplantation. Varicella-zoster virus glycoproteins B and E might form the basis for novel non-hazardous zoster subunit vaccines suitable for immunocompromised transplant patients.

Eight-plex PCR and liquid-array detection of bacterial and viral pathogens in cerebrospinal fluid from patients with suspected meningitis

We here report on the development of a novel multiplex PCR with product detection in a Luminex 100 suspension array system. The assay covers the nine most important bacterial and viral pathogens found in Danish meningitis patients. The microorganisms include Neisseria meningitidis, Streptococcus pneumoniae, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Streptococcus agalactiae, herpes simplex virus types 1 and 2, and varicella-zoster virus. The study was based on 1,187 samples, of which 55 were found to be positive by PCR. The assay was found to have an excellent sensitivity and an excellent specificity compared to the results of a "gold standard," defined by routine laboratory tests, for the two most important pathogens, S. pneumoniae (95 and 99.1%, respectively) and N. meningitidis (100 and 99.7%, respectively). The method provides a valuable supplement to the traditional microscopy and culture of cerebrospinal fluid (CSF) samples in a routine diagnostic setting, and results can be available within 1 workday. The method is suitable for use for the initial screening and identification of nine important microorganisms in CSF samples from patients with suspected meningitis. Compared to microscopy and culture of CSF, this rapid and sensitive method will support physicians with the selection of the appropriate antimicrobial agents and the initiation of timely treatment in the absence of live microorganisms in the CSF.

Varicella zoster virus glycoprotein E-specific CD4+ T cells show evidence of recent activation and effector differentiation, consistent with frequent exposure to replicative cycle antigens in healthy immune donors

Varicella zoster viru (VZV)-specific T cell responses are believed to be vital in recovery from primary VZV infection and also in the prevention of viral reactivation. While glycoprotein E (gE) is the most abundant and one of the most immunogenic proteins of the virus, there are no data addressing potential T cell epitopes within gE, nor the phenotype of specific T cells. Using interferon gamma enzyme-linked immunospot assays and intracellular cytokine assays, we identified gE-specific immune responses in 20 adult healthy immune donors which were found to be dominated by the CD4+ subset of T cells. We characterized three immune dominant epitopes within gE restricted through DRB1*1501, DRB1*07 and DRB4*01, and used DRB1*1501 class II tetrameric complexes to determine the ex vivo frequency and phenotype of specific T cells. In healthy immune donors, the cells were largely positive for CCR7, CD28 and CD27, but expressed variable CD62L and low levels of cutaneous lymphocyte associated antigen with evidence of recent activation. In summary, we show that circulating gE-specific CD4+ T cells are detected at a relatively high frequency in healthy immune donors and show evidence of recent activation and mixed central and effector memory phenotype. These data would be compatible with frequent exposure to replicative cycle antigens in healthy donors and are consistent with a role for gE-specific CD4+ T cells in the control of viral replication.

Downregulation of varicella-zoster virus (VZV) immediate-early ORF62 transcription by VZV ORF63 correlates with virus replication in vitro and with latency

Varicella-zoster virus (VZV) open reading frame 63 (ORF63) protein is expressed during latency in human sensory ganglia. Deletion of ORF63 impairs virus replication in cell culture and establishment of latency in cotton rats. We found that cells infected with a VZV ORF63 deletion mutant yielded low titers of cell-free virus and produced very few enveloped virions detectable by electron microscopy compared with those infected with parental virus. Microarray analysis of cells infected with a recombinant adenovirus expressing ORF63 showed that transcription of few human genes was affected by ORF63; a heat shock 70-kDa protein gene was downregulated, and several histone genes were upregulated. In experiments using VZV transcription arrays, deletion of ORF63 from VZV resulted in a fourfold increase in expression of ORF62, the major viral transcriptional activator. A threefold increase in ORF62 protein was observed in cells infected with the ORF63 deletion mutant compared with those infected with parental virus. Cells infected with ORF63 mutants impaired for replication and latency (J. I. Cohen, T. Krogmann, S. Bontems, C. Sadzot-Delvaux, and L. Pesnicak, J. Virol. 79:5069-5077, 2005) showed an increase in ORF62 transcription compared with those infected with parental virus. In contrast, cells infected with an ORF63 mutant that is not impaired for replication or latency showed ORF62 RNA levels equivalent to those in cells infected with parental virus. The ability of ORF63 to downregulate ORF62 transcription may play an important role in virus replication and latency.

Comparison of real-time and nested PCR assays for detection of herpes simplex virus DNA

We performed a real-time PCR assay to detect herpes simplex virus (HSV) DNA, and compared it prospectively with a nested PCR assay in 164 clinical samples (109 cerebrospinal fluid and 55 sera) from patients suspected of having neonatal HSV infection or HSV encephalitis. In 25 of 164 samples, HSV DNA was detected by the nested PCR assay. All samples positive for HSV DNA in the nested PCR assay were also positive in the real-time PCR assay, and all but two samples negative for HSV DNA in the nested assay were negative in the real-time assay. The real-time PCR assay thus had a sensitivity of 100% and a specificity of 99%, when compared with the nested assay. Sequential assays in a case of disseminated HSV showed that a decrease in HSV DNA paralleled clinical improvement. Quantification of HSV DNA by real-time PCR was useful for diagnosing and monitoring patients with HSV encephalitis and neonatal HSV infection.

Monitoring herpesvirus DNA in three cases of acute retinal necrosis by real-time PCR

BACKGROUND

It is not clear whether quantitative analysis of viral DNA in ocular specimens is correlated with disease activities of acute retinal necrosis (ARN).

OBJECTIVES

To monitor viral load in ocular specimens collected from patients with ARN by real-time polymerase chain reaction (PCR).

STUDY DESIGN

Ocular samples (aqueous humor and vitreous) were serially collected from three patients with ARN. Viral load in those samples was evaluated by real-time PCR.

RESULTS AND CONCLUSION

In case 1, large amounts of varicella zoster virus (VZV) DNA (4.8 x 10(6) to 5.5 x 10(6) copies/ml) were detected in aqueous humor during the first 2 weeks after admission. The viral load in vitreous was higher than that in aqueous humor at the time of vitrectomy. As ophthamoscopic findings and visual acuity improved through acyclovir (ACV) treatment, the viral load in aqueous humor decreased dramatically. In case 2, the patient was treated with intravenous ACV at first, but clinical features did not improve. The herpes simplex virus (HSV)-2 viral load in aqueous humor remained stable (2.3 x 10(3) to 2.8 x 10(3) copies/ml) during the first 3 weeks after admission. The amount of HSV-2 DNA in vitreous was again higher than that in aqueous humor. Although neither clinical features nor viral load had changed by ACV, intra-ocular ganciclovir (GCV) injection improved clinical features, and decreased viral load to undetectable levels. In case 3, the patient developed ARN within 1 month after the onset of varicella and demonstrated only mild clinical symptoms. She was treated with ACV administration alone and recovered quickly. In contrast to case 1, the copy number of VZV DNA at the time of admission was low (9 x 10(2) copies/ml), and decreased quickly in response to the treatment. Correlation between viral load in ocular specimens and clinical course of the disease was demonstrated in these patients.

Superiority of varicella skin test antigen over purified varicella-zoster virus glycoproteins in monitoring booster response to Oka varicella vaccine

Varicella skin test antigen has been developed based on the induction of delayed-type hypersensitivity (DTH) to varicella-zoster virus (VZV). The booster immune response to Oka varicella vaccine was assessed by cutaneous reactivity to purified VZV glycoprotein complexes, gB, gE:gI, gH:gL, and varicella skin test antigen. Skin tests with these antigens significantly augmented antibody production to glycoproteins and VZV antigen resulting in no further augmentation by the subsequent vaccination. All glycoprotein complexes induced the cutaneous reaction similarly to varicella skin test antigen. Cutaneous reaction to glycoproteins and varicella skin test antigen was boosted after vaccination. However, the magnitude of cutaneous reaction to each glycoprotein complex before and after vaccination was rich in variety. These results indicated that skin test with varicella skin test antigen is a more suitable indicator in monitoring cell-mediated immunity to VZV than that using purified glycoproteins.

Varicella exposure in a neonatal medical centre: successful prophylaxis with oral acyclovir

In December 2000, a female infant hospitalized in our Neonatal Care Centre was infected with varicella by her mother. Although prophylactic intravenous acyclovir was administered at a dose of 15 mg/kg daily, she later developed varicella during her hospital stay. We therefore initiated control procedures to prevent further hospital-acquired infections. Oral acyclovir (40 mg/kg daily divided into four doses) was administered prophylactically to six preterm infants in contact with the varicella patient. None of six preterm infants subsequently developed clinical varicella or had any adverse effects associated with acyclovir administration. It is suggested that prophylactic administration of oral acyclovir (40 mg/kg daily) might prevent hospital-acquired varicella-zoster virus (VZV) infections, and that oral acyclovir may be an option for VZV prophylaxis in situations where VZV immunoglobulin is not available.

Induction of cellular immunity to varicella-zoster virus glycoproteins tested with pernasal coadministration of Escherichia coli enterotoxin in mice

A mutant of Escherichia coli enterotoxin promotes the induction of cellular immunity to a live varicella vaccine (the Oka strain) as a mucosal adjuvant in mice. An investigation was carried out to determine which of the purified glycoproteins of the virus among three induced cellular immunity with a single nasal administration. Spleen cells from mice immunized nasally with the vaccine and toxin produced interleukin-2 (IL-2) at the same level on restimulation in vitro with glycoprotein H: glycoprotein L (gH:gL), gB, and gE:gI, but not IL-4. The spleen cells from mice immunized with gH:gL, gB, or gE:gI and toxin produced IL-2 on restimulation with gH:gL, gB, or gE:gI, respectively, and the vaccine, but not IL-4. Immunization with gH:gL and the toxin showed increased thymidine uptake and production of IL-2 and interferon-gamma (IFN-gamma) of the spleen cells, but not IL-4, depending on the dose of gH:gL used for immunization and restimulation in vitro. Purified gE:gI and gB have been reported to be the strongest stimulators of cellular immunity to varicella upon subcutaneous injection and are useful as a subunit vaccine. All the glycoproteins tested are excellent stimulators of cellular immunity to the virus and itself on nasal co-immunization with the toxin.

The requirement of varicella zoster virus glycoprotein E (gE) for viral replication and effects of glycoprotein I on gE in melanoma cells

The glycoprotein E (gE) of varicella zoster virus (VZV), encoded by ORF68, is the most abundant viral glycoprotein. In the current experiments, we demonstrated that ORF68 deletion was incompatible with recovery of infectious virus from VZV cosmids. Replacing ORF68 at a nonnative AvrII site in the genome restored infectivity. Further, we found that VZV gE could be expressed under the control of the Tet-On promoter in stably transfected melanoma cell lines (Met-gE cells) without evidence of toxicity. In these Met-gE cells, gE colocalized with gamma-adaptin, a trans Golgi network marker, in perinuclear sites, but did not reach plasma membranes. In order to investigate how infection altered gE localization, we made a recombinant virus, vOka-MSPgE, with ORF68 from the VZV MSP strain. VZV MSP encodes a mutant gE protein (D150N) that lacks the mAb epitope, 3B3 (Santos et al., Virology 275, 306-317, 2000), whereas Met-gE protein binds mAb 3B3. Within 48 h after Met-gE cells were infected with vOka-MSPgE, the steady-state distribution of Met-gE protein extended beyond the perinuclear areas to other cytoplasmic sites and to plasma membranes. A second recombinant, vOka-MSPgE without gI (vOka-MSPgEdeltagI), was constructed to investigate Met-gE protein distribution in the absence of gI. The redistribution of Met-gE protein which was observed by 48 h after vOka-MSPgE infection did not occur until 5 days (140 h) within vOka-MSPgEdeltagI infected cells. After vOka-MSPgE infection of Met-gE cells, most Met-gE protein was in the final 94K mature form by 72 h. However, progression to predominance of mature gE was delayed in Met-gE cells infected with vOka-MSPgEdeltagI. These observations confirm our hypothesis that VZV gE is essential, based upon the demonstration of restored infectivity after replacing ORF68 in a nonnative site in the genome, and provide further evidence of the role of gI in facilitating the maturation and intracellular distribution of this critical VZV glycoprotein.

Quantitation of viral load in neonatal herpes simplex virus infection and comparison between type 1 and type 2

Neonatal herpes simplex virus (HSV) infection is a severe disease with high mortality and morbidity in spite of the development of effective anti-viral therapies. The viral load in neonatal herpes simplex virus (HSV) infection was measured retrospectively in 37 patients. HSV DNA copy numbers in serum and cerebrospinal fluid (CSF) were quantified using a real-time PCR assay. Patients with disseminated infection had a higher viral load in their sera. whereas patients with central nervous system (CNS) infection exhibited a higher viral load in the CSF. The viral load was significantly higher in the serum of patients who died later. Interestingly, patients with HSV type-2 infection exhibited more CNS involvement and neurological impairment, together with a high viral load in the CSF, than did HSV type-1 patients. These results suggest that quantitation of HSV viral load may be useful for assessing the prognosis, and may provide additional information for the management of neonatal HSV infection.

Investigation of varicella-zoster virus DNA in lymphocyte subpopulations by quantitative PCR assay

To investigate the nature of viremia during the acute phase of varicella, we studied the viral load in nine otherwise healthy children with varicella. Plasma and peripheral blood mononuclear cells (PBMC) were obtained, then PBMC were divided into CD4+T, CD8+T, and B lymphocytes and monocyte/macrophage fractions. The viral DNA in each component was quantified using a real-time quantitative polymerase chain reaction assay. Varicella-zoster virus (VZV) DNA was detected in plasma, PBMC and all subpopulations. The amount of viral DNA was similar in each PBMC subpopulation, suggesting that each lymphocyte fraction and monocytes carry similar amounts of VZV DNA during viremia.

Monitoring four herpesviruses in unrelated cord blood transplantation

Cord blood transplantation, which has lower risk of graft-versus-host disease than bone marrow transplantation, might have higher risk of infections. A system to quantify four herpesviruses, CMV, human herpesvirus 6 (HHV6), EBV, varicella-zoster virus using the real-time PCR assay was established and applied for prospective viral load monitoring in three recipients undergoing cord blood transplantation. CMV and HHV6 were detected in peripheral blood from all three recipients, while EBV was detected in two. Varicella-zoster virus was not detected at all. At the peak of HHV6 or CMV, each patient showed virus-related symptoms. During the pre-transplant period, CMV DNA was detected in two recipients who later developed CMV-related diseases. These observations indicate that our system is not only useful for managing herpesviruses infections in transplant recipients, but also a powerful method for clarifying the relationships between the viral load and clinical symptoms.

Usefulness of quantitative real-time polymerase chain reaction in following up patients with Epstein-Barr virus infection after liver transplantation

BACKGROUND

Post-transplant lymphoproliferative disease (PTLD), which is mainly induced by Epstein-Barr virus (EBV) infection, is a cause of significant morbidity and mortality for patients undergoing liver transplantation, especially when it is detected at such an advanced stage as monoclonal malignant lymphoma.

METHODS

In this series, 6 of 22 liver transplant patients suffered from EBV infection. We tested quantitative DNA (Qt-DNA) by real-time polymerase chain reaction (PCR), qualitative DNA in plasma (Q1-pDNA) by PCR, and EBV-encoded mRNA 1 (EBER 1) by in situ hybridization to clarify which of them is a better marker for the early diagnosis and prediction of EBV-associated disorders.

RESULTS

Four had signs or symptoms of PTLD, but 2 did not develop individualized lymphoid lesions. In all patients, both Qt-DNA and EBER 1 exceeded the cut-off level of 10(2.5) copies/microg DNA and 0.002%, respectively, at the time of diagnosis. In 2 patients, when Qt-DNA had a poor decline, EBER 1, even if it seemed to decrease after antiviral therapy, increased again after a few months and the clinical symptoms recurred. In 2 patients, Qt-DNA and EBER 1 increased again after a few months of antiviral therapy, and Q1-pDNA remained positive, whereas, in 3 patients, no reaction of EBV could be detected once Q1-pDNA became negative, even after the cessation of therapy.

CONCLUSIONS

These results suggest that real-time PCR for Qt-DNA was more sensitive to the real-time activity of EBV and that Q1-pDNA could indicate when to stop antiviral therapy.

Comparison of quantitations of viral load in varicella and zoster

The pathogenesis of varicella and zoster and the effects of antiviral treatment were investigated using real-time PCR for varicella-zoster virus (VZV) DNA in skin lesions and peripheral blood. A higher occurrence of viremic VZV DNA was observed in varicella than in zoster. Acyclovir treatment resulted in marked suppression of viremia in varicella.

Quantitative analysis of cytomegalovirus load using a real-time PCR assay

A novel real-time PCR assay system was developed to quantify the cytomegalovirus (CMV) genome load. The real-time PCR assay could detect from 6 to over 10(6) copies of CMV-DNA with a wide linear range. The virus load of immunocompromised patients with symptomatic CMV infections was quantified and compared to that of asymptomatic ones. In symptomatic patients, all 17 peripheral blood leukocytes were positive for CMV DNA, and its mean value was 10(3.3) copies/10(6) cells. On the other hand, only 9 of 38 samples (24%) were positive in the asymptomatic patients, and its mean titer was lower (10(2.0) copies/10(6) cells) than that of the symptomatic group (P = 0.002). In plasma, the virus genome was detected in 13 out of 17 samples from symptomatic patients (76%), and its mean value was 10(4.0) copies/ml. In contrast, for the asymptomatic group, only one out of 36 samples were positive (3%). Finally, this system was used to monitor two patients with CMV infections serially. The CMV DNA copy number changed with their clinical symptoms and anti-CMV therapy, and virtually paralleled the result of the pp65 antigenemia assay in both cases. In one patient with the cord blood transplantation, however, the CMV DNA became positive faster than the antigenemia assay. These results indicate that this assay is sensitive and useful for estimating the CMV genome load not only in peripheral blood leukocytes but also in plasma. It can be very helpful for diagnosing CMV-related diseases and monitoring the virus load in patients with CMV infections.

Quantitation of latent varicella-zoster virus and herpes simplex virus genomes in human trigeminal ganglia

Using real-time fluorescence PCR, we quantitated the numbers of copies of latent varicella-zoster virus (VZV) and herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) genomes in 15 human trigeminal ganglia. Eight (53%) and 1 (7%) of 15 ganglia were PCR positive for HSV-1 or -2 glycoprotein G genes, with means of 2,902 +/- 1,082 (standard error of the mean) or 109 genomes/10(5) cells, respectively. Eleven of 14 (79%) to 13 of 15 (87%) of the ganglia were PCR positive for VZV gene 29, 31, or 62. Pooling of the results for the three VZV genes yielded a mean of 258 +/- 38 genomes/10(5) ganglion cells. These levels of latent viral genome loads have implications for virus distribution in and reactivation from human sensory ganglia.

Quantitative analysis of Epstein-Barr virus load by using a real-time PCR assay

To measure the virus load in patients with symptomatic Epstein-Barr virus (EBV) infections, we used a real-time PCR assay to quantify the amount of EBV DNA in blood. The real-time PCR assay could detect from 2 to over 10(7) copies of EBV DNA with a wide linear range. We estimated the virus load in peripheral blood mononuclear cells (PBMNC) from patients with symptomatic EBV infections. The mean EBV-DNA copy number in the PBMNC was 10(3.7) copies/microg of DNA in patients with EBV-related lymphoproliferative disorders, 10(4.1) copies/microg of DNA in patients with chronic active EBV infections, and 10(2.2) copies/microg of DNA in patients with infectious mononucleosis. These numbers were significantly larger than those in either posttransplant patients or immunocompetent control patients without EBV-related diseases. In a patient with infectious mononucleosis, the virus load decreased as the symptoms resolved. The copy number of EBV DNA in PBMNC from symptomatic EBV infections was correlated with the EBV-positive cell number determined by the in situ hybridization assay (r = 0.842; P < 0.0001). These results indicate that the real-time PCR assay is useful for diagnosing symptomatic EBV infection and for monitoring the virus load.