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Granulomatous arteritis characterizes the pathology of giant cell arteritis, granulomatous aortitis, and intracerebral varicella zoster virus (VZV) vasculopathy. Because intracerebral VZV vasculopathy and giant cell arteritis are strongly associated with productive VZV infection in cerebral and temporal arteries, respectively, we evaluated human aortas for VZV antigen and VZV DNA. Using 3 different anti-VZV antibodies, we identified VZV antigen in 11 of 11 aortas with pathologically verified granulomatous arteritis, in 1 of 1 cases of nongranulomatous arteritis, and in 5 of 18 control aortas (28%) obtained at autopsy. The presence of VZV antigen in granulomatous aortitis was highly significant (P = .0001) as compared to control aortas, in which VZV antigen was never associated with pathology, indicating subclinical reactivation. VZV DNA was found in most aortas containing VZV antigen. The frequent clinical, radiological, and pathological aortic involvement in patients with giant cell arteritis correlates with the significant detection of VZV in granulomatous aortitis.

(See the editorial commentary by Wittes on pages 1523–5.) Herpes zoster (HZ), caused by reactivation of latent varicella zoster virus (VZV) [1], entails rash and pain that decreases daily functioning and health-related quality of life, more so with increasing age [1–10]. The phase III Shingles Prevention Study (SPS) showed that the live, attenuated zoster vaccine (ZV; Zostavax, Merck, Whitehouse Station, NJ) had an estimated 51% vaccine efficacy (VE; 95% confidence interval [CI], 44%–58%) to reduce the incidence of HZ in persons aged ≥60 years [11]. Subsequently, another phase III Zostavax Efficacy and Safety Trial (ZEST) was conducted to assess the VE of ZV in persons aged 50–59 years and showed an estimated 70% VE (95% CI, 54%–81%) [12]. Secondary analyses of the SPS suggested that 3 different measures of VZV-specific immunity were correlated with protection from HZ: responder cell frequency–determined cell-mediated immunity (CMI), interferon γ (IFN-γ) enzyme-linked immunosorbent spot–determined CMI, and glycoprotein-based enzyme-linked immunosorbent assay (gpELISA)–determined antibody level [13]. Because the gpELISA is easier to use and more validated as a reproducible quantitative assay and because the combination of titers and fold rise appeared to best correlate with protection in the SPS [14], the ZEST included an objective to assess VZV antibody titers by gpELISA but not by the CMI measures as a correlate of protection (CoP). Both week 6 and fold rise in VZV antibody titers determined by gpELISA were strong inverse correlates of risk (CoRs) of HZ in vaccine recipients [15], where a CoR is defined as an immune biomarker that is associated with the rate of a study end point used to measure VE in a defined population [16]. Here we directly assess whether the identified CoRs are also good CoPs [16]. A CoP may be defined as an immune biomarker measuring a response to vaccination that reliably predicts the level of VE to prevent a clinically meaningful end point. The literature on approaches for assessing CoPs has used different meanings for the term “CoP,” with no consensus [16–20]. Plotkin and Gilbert [21] advocated for the common use of the definition specified above, which is solely about reliable statistical prediction and is silent about whether the biomarker is also a mechanism of protection. These authors also advocated for annotating CoPs as mCoPs (mechanistic CoPs) or nCoPs (nonmechanistic CoPs) for scenarios in which experiments have determined whether the biomarker is a true mechanism of protection. Validated CoPs benefit vaccine development by serving as reliable surrogate end points for true clinical end points of interest, thereby allowing using surrogate end points in phase I and II trials to provide reliable answers about clinical VE without requiring phase III field trials. Validated CoPs confer many other benefits, as extensively discussed elsewhere [16–20, 22]. Given that reliable prediction of VE is very useful in itself, even as a so-called black box predictor with no associated mechanism, nCoPs and mCoPs are highly beneficial for vaccine development. The concept of a CoP is the same as a valid surrogate end point in the clinical trials statistical literature. Two major statistical frameworks have been developed for assessing the validity of a surrogate end point based on an efficacy trial, the Prentice framework [16, 23–25] and the principal stratification or VE curve framework [26, 27]. While both are useful for assessing the validity of the candidate gpELISA CoPs, this article focuses on the VE curve framework. This approach directly estimates the VE curve, defined as the VE against the clinical end point for each of a spectrum of participant subgroups defined by their biomarker readout measuring vaccine-induced immune response. The major challenge posed to using this approach is that the vaccine-induced immune response is only measured in subjects assigned to receive the vaccine (it is unknown in subjects assigned to receive placebo). Consequently, its effective application requires availability of a subject characteristic before immunization that predicts the candidate CoP [28]; such a baseline immunogenicity predictor (BIP) allows inclusion of an estimate of the immune response to the vaccine that placebo recipients would have had had they been vaccinated, thereby enabling estimation of the VE curve. This approach can be used for estimating the VE curve for subgroups defined either by levels of the vaccine-induced immune response or by both the levels of this response and the response under assignment to placebo. Several statistical methods have been developed for estimating the VE curve based on a BIP [27–32]. However, because adequately predictive BIPs have not been available, the methods have not yet been effectively applied. Fortunately, a high-quality BIP is available in the ZEST, and here we report, for the first time, an application of this framework to produce clear results that validate one biomarker as an excellent CoP (fold rise in gpELISA titers) and another biomarker as a poor CoP (week 6 gpELISA titers). By directly assessing how VE varies with participant subgroups defined by gpELISA readouts, this framework provides clearly interpretable results that lend themselves to central applications, such as comparing the utility of different immune response biomarkers as CoPs and estimating seroprotection levels.

Immunity to childhood diseases is maintained for decades by mechanisms that, at present, are still unclear. We longitudinally studied immune responses in 16 adults exposed to children experiencing varicella (chicken pox). None of the individuals showed clinical signs of infection, and varicella-zoster virus (VZV) DNA could not be detected in peripheral blood or cultured from nasopharyngeal swabs. Exposure to VZV, however, induced expansion of antigen-specific CD4(+) T cells in peripheral blood, with concomitant changes in cytotoxic CD8(+) T cells and natural killer cells. VZV-specific memory CD4(+) T cells were uniformly CD45RA(-) and enriched for CD27(-) cells. The virus-specific cells produced interferon- gamma, tumor necrosis factor- alpha, and interleukin-2. These memory responses to VZV were compared with the primary immune responses of children experiencing varicella. VZV-specific memory CD4(+) T cell responses largely resemble the primary immune response to VZV.

Varicella (chickenpox) is a highly contagious disease caused by varicella zoster virus (VZV). After infection, the virus remains dormant in sensory dorsal root ganglia. Reactivation of latent VZV is associated with cutaneous disease occurring in $1 dermatomes, termed herpes zoster (HZ). Historically, HZ has been considered significantly less infectious than varicella and has not been thought to play an important role in person-to-person transmission. Since the licensure of the varicella vaccine in 1995 and the more recent recommendation that a second dose of vaccine be given to children aged 4–6 years [1], the epidemiology of pediatric varicella infection has shifted dramatically [2]. Efforts to quantify the burden of varicella in the community since vaccine licensure have been hindered by the absence of mandatory case-based reporting in most jurisdictions [3]. The article by Viner et al in this issue of the journal [4] provides important new insights into the epidemiology and transmissibility of VZV in a highly immunized, healthy pediatric population. The authors analyzed data obtained through a combination of active and passive surveillance for both varicella and HZ in Philadelphia schools and day care centers during 7 academic years. Cases were linked to the Philadelphia Department of Public Health immunization registry for ascertainment of vaccine status. Through this comprehensive surveillance system, 2296 cases of VZVassociated infection were identified, with 28% categorized as secondary varicella. Much of what is known about VZV transmission dynamics in the community comes from outbreak investigations at elementary schools or day care centers. In these settings, varicella attack rates among children who had previously received a single dose of varicella vaccine ranged from 12%–42% [5–7]. A recent report found that prior receipt of a second dose of vaccine did not appreciably decrease the attack rate during a school outbreak [8]. In contrast, in an elementary school outbreak during which the second dose of vaccine was given as an intervention for outbreak control, the attack rate was reduced from 43% among children who had received only a single vaccination to 5% among 2-dose recipients [9]. Large-scale, school-based varicella outbreaks such as these serve as important sentinel events but may not be representative of the true burden and infectivity of VZV in the community. In the study by Viner et al, .80% of epidemiologically linked transmissions involved ,4 secondary cases and, in the absence of a dedicated varicella surveillance system, would be unrecognized and unreported. Despite the continued documentation of outbreaks among immunized school children, the varicella vaccine epitomizes a public health success story. In the prevaccine era, varicella was an almost universal disease of childhood. After the widespread implementation of pediatric vaccination in the United States, incidences of VZV-related infection, hospitalization, and death have all markedly declined [10, 11]. In the present study, .90% of children who developed secondary varicella had received $1 doses of vaccine before the onset of infection, representing vaccine failures. However, even in these breakthrough cases, the benefits of vaccination are evident. As has been reported elsewhere [12, 13], .70% of breakthrough varicella cases had mild disease characterized by ,50 skin lesions. Vaccinated varicella cases were associated with a significantly lower proportion of secondary cases compared with unvaccinated cases, presumably related to lower virus burden and shorter duration of viral shedding. Finally, there was a significant decline in the incidence of all VZV-related infections in Philadelphia schools beginning in 2007, Received 9 December 2011; accepted 12 December 2011; electronically published 27 March 2012. Correspondence: Karen C. Bloch, MD, MPH, Division of Infectious Diseases, Vanderbilt University Medical Center, A-2200, Medical Center North, Nashville, TN 37232 (karen.bloch@vanderbilt.edu). The Journal of Infectious Diseases 2012;205:1331–3 The Author 2012. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. permissions@oup.com DOI: 10.1093/infdis/jis214

Congenital varicella syndrome is a rare complication of varicella-zoster virus (VZV) infection during pregnancy. An infant was exposed to VZV at 18.5 weeks of gestation and had eye and skin abnormalities at birth and persistent feeding difficulties, prompting esophageal biopsies at 12 days and 20 and 20.5 months of age. Esophageal tissues demonstrated specialized intestinal metaplasia (Barrett's esophagus). VZV DNA (in situ hybridization) and proteins (immunohistochemistry and polymerase chain reaction) were found in esophageal epithelial cells adjacent to the Barrett's lesion. Immediate-early 63 protein (IE63) of VZV was demonstrated in the day 12 specimen, and IE62 and the late VZV glycoprotein E (gE) were found in the 20-month specimen. Clinical and endoscopic improvement followed fundoplication and acyclovir therapy, but VZV DNA and IE62 persisted in esophageal tissue. These findings associate VZV with specialized intestinal metaplasia within the esophagus and suggest a novel site for either latent or active VZV infection.

A method was developed to distinguish the Oka vaccine strain of varicella-zoster virus (VZV) from other clinical isolates. The molecular characteristics of 52 clinical isolates from varicella or zoster patients with no history of VZV vaccination and the Oka strain, including vaccine and parental viruses, were analyzed by PstI cleavage of the PstI site-less (PSL) region. This was followed by single-strand conformational polymorphism (SSCP) after polymerase chain reaction amplification of repeating region 2 (R2). Most of the clinical isolates tested, especially recent isolates, had a PstI site in the PSL region, but the Oka strain did not. The SSCP patterns of R2 in Oka strain virus differed from those of other viruses. These results suggest that analysis of the PstI site followed by SSCP of R2 will be useful for identifying the Oka vaccine virus in isolates.

Chickenpox is a relatively mild disease in healthy children but may be life threatening in immuno-suppressed patents, neonates, and normal adults, especially smokers-for whom the risk of varicella pneumonia is high. The epidemiology of chickenpox appears to be changing: There has been an unexplained upward shift in the age distribution of cases over the last 20 years. This is reflected by increased consultations for chickenpox in general practices and more deaths in England and Wales. On the basis of hospital admissions for chickenpox in young adults, there is evidence of a similar trend in the United States. This epidemiologic change has important consequences for future mortality rates and for risk of infection in health care workers and pregnant women. The potential use of the varicella vaccine should be considered as a measure to reduce the risk of nosocomial transmission in view of the possible changing epidemiology of varicella.

Live attenuated varicella vaccine elicits protection against varicella-zoster virus (VZV), but adults require two doses to achieve optimal seroconversion rates. To assess the potential role of cell-mediated immunity (CMI), T cell proliferation to VZV antigen was compared in children and adults. Mean stimulation indices (SI) in two cohorts of 39 children tested 6 weeks after vaccination were 28.6 +/- 6.21 and 22.1 +/- 3.84, whereas 20 adult vaccines had a mean SI of 9.1 +/- 0.99 (P = .04). Vaccinees had significant increases in CMI after a second dose of vaccine. At 1 year, VZV CMI was significantly lower in adults after two doses (10.0 +/- 1.13 vs. 15.6 +/- 1.77; P = .02), even though 82% of children received one dose. Limitations in the adult helper T cell response to VZV antigens may explain the need for booster doses to elicit effective immunity and the more frequent occurrence of varicella when adult vaccines are exposed to wild type virus.

In a group of 21 women counseled after exposure to chickenpox during pregnancy, 4 developed varicella despite initial studies showing that preinfection sera were varicella-zoster virus (VZV)-seropositive by fluorescent anti-membrane antibody, latex agglutination, ELISA, and VZV glycoprotein immunoblot assay. Further investigations showed that 2 of the 4 had low-titer (1/100), low-avidity, VZV-reactive IgG3 antibodies by ELISAs of preinfection sera. After chickenpox, these women developed primary-like serologic responses to VZV. Two women with high-titer (1/1600, 1/3200), high-avidity, IgG1 antibodies showed anamnestic serologic responses after reinfection. The criteria of protective VZV immunity remain ill-defined.

The polymerase chain reaction method (PCR) was used to investigate events in the pathogenesis of varicella-zoster virus (VZV) infection in strain 2, Hartley, and euthymic hairless guinea pigs. VZV was detected in peripheral blood mononuclear cells (PBMC) obtained 2-5 days after infection in 8 (50%) of 16 strain 2, 4 (40%) of 10 hairless, and 10 (34%) of 29 Hartley guinea pigs. The frequency of VZV-infected PBMC was estimated to be at least 1/200,000, which is comparable to that observed in human infection. When VZV PCR was used to test ganglia from hairless guinea pigs, samples from 6 of 8 animals were positive. Of 45 VZV-infected guinea pigs that were tested for cellular immunity by VZV T lymphocyte proliferation assay, 44 developed a stimulation index > 2.0. Control animals had no detectable virus by PCR and did not develop cellular immunity to VZV. These experiments showed that viremia was detectable by PCR during primary VZV infection of guinea pigs in about half of the animals regardless of the strain of guinea pig. Acquisition of cellular immunity provided a consistent marker of infection in all guinea pig strains. PCR was also useful for demonstrating VZV in guinea pig ganglia tissue, with VZV gene sequences being detectable for at least 80 days after infection. With the combination of PCR and immunologic assays, various guinea pig strains should be useful for studies of VZV pathogenesis and for the evaluation of antiviral agents and vaccine strategies.

Natural varicella-zoster virus (VZV) infection and immunization with live attenuated varicella vaccine elicits T lymphocytes that recognize VZV glycoproteins, gpI-V, and the immediate early/tegument protein, the product of gene 62 (IE62). Proliferation or cytotoxicity assays, done under limiting dilution conditions to estimate responder cell frequencies, indicate no preferential recognition of VZV proteins by human T cells. Analysis of the primary cytotoxic T lymphocyte (CTL) response after vaccination demonstrates that both gpI and IE62 are targets of the early response. CD4(+)- and CD8(+)-mediated CTL recognition of these viral proteins can be detected with natural and vaccine-induced immunity. Responder cell frequencies for protein-specific T cell proliferation and CTL function are generally comparable in subjects with natural and vaccine-acquired immunity to VZV. Exogenous reexposure to VZV results in enhanced T cell proliferation and may be an important mechanism for maintaining virus-specific cellular immunity. Providing exogenous reexposure by giving varicella vaccine to individuals who have preexisting natural immunity markedly increases the responder cell frequencies of T cells that proliferate in response to VZV antigen and the numbers of circulating CTL that recognize VZV proteins.

The cytotoxic T lymphocyte (CTL) response was evaluated in adults given live attenuated varicella vaccine, using target cells expressing varicella-zoster virus (VZV) immediate-early protein (IE62) or VZV glycoproteins gpI, gpIV, or gpV to determine viral protein specificity. The frequency of CTL that recognized IE62 was 1:171,000 +/- 46,000 SE in subjects tested 10 days to 8 weeks after the initial vaccine dose; the induction of CTL specific for gpI was equivalent. CTL recognition of VZV proteins was mediated by CD4+ or CD8+ cells. CTL recognition of IE62 and gpIV persisted in vaccinees (tested approximately 4 years later) and was comparable to that in the naturally immune. The mean frequency of CTL specific for gpV was lower (but not significantly) in vaccinees than in naturally immune subjects. Assay of responder cell frequencies showed persistence of equivalent numbers of T lymphocytes that recognized IE62 and gpI in vaccinees and naturally immune subjects. Immunization with this vaccine elicited memory T lymphocyte responses to VZV comparable to those induced by natural infection.

Peripheral blood mononuclear cells (PBMC) from humans of different ages were analyzed for DNA sequences specific for varicella-zoster virus (VZV) genes 29 and 62 by polymerase chain reaction (PCR). Neither VZV gene was detected in DNA from umbilical cord blood PBMC of 10 infants or from blood PBMC of two 3-year-old children. In 22 humans less than 60 years old, gene 29 was not detected, and gene 62 was detected in only one subject. In 33 humans greater than 60 years old, including patients with postherpetic neuralgia, PBMC from 4 subjects contained gene 29, 4 contained gene 62, and 1 contained both genes. The presence of VZV DNA correlated significantly with age (P less than .05, chi 2 and logistic regression analysis), but not with gender or postherpetic neuralgia.

BV-araU (1-beta-D-arabinofuranosyl-E-5-[2-bromovinyl]uracil) has potent antiviral activity against varicella zoster virus in cell culture and is undergoing clinical evaluation. In the present study, pharmacokinetic parameters and the efficacy of BV-araU against infection with simian varicella virus (SVV) were evaluated in African green monkeys. Pharmacokinetic parameters were determined by analysis of the BV-araU content of sera obtained after oral and intravenous administration to normal monkeys. Peak serum concentrations showed dose proportionality, with the 0.1 mg/kg dose resulting in a peak serum concentration of 0.05 micrograms/ml, the approximately ED50 value for the SVV inoculum in cell culture. BV-araU administered orally twice daily at 0.1 mg/kg for 10 days starting 48 h after intratracheal SVV infection prevented vesicular rash development and suppressed viremia. Effective therapy could be initiated 96 h after infection. Taken together, these results indicate that BV-araU is effective oral therapy at doses that achieve peak serum levels equivalent to the ED50 for SVV in cell culture.

A polymerase chain reaction (PCR) method developed to detect varicella zoster virus (VZV) in clinical samples is based on amplifying sequences of viral gene 31, the coding region for glycoprotein II. Its sensitivity was evaluated by amplification from plasmid VZV DNA containing VZV gene 31; 45 copies were detected in 1 microgram of human DNA. In testing within 24 h after the onset of varicella exanthem, 21 (75%) of 28 lesion samples were positive by VZV PCR, whereas VZV was isolated from only 21% by a standard tissue culture method. Only 1 (3.3%) of 30 samples of oropharyngeal secretions but peripheral blood mononuclear cells from 8 (67%) of 12 patients were positive. The sensitivity and specificity of the VZV PCR method indicates its usefulness for investigating the pathogenesis of VZV infection. Direct contact with cutaneous lesions rather than respiratory secretions may be the most important route of VZV transmission from healthy individuals with acute varicella.

Four hundred nineteen children and adolescents immunized with live varicella vaccine 4-6 years earlier were enrolled in a study to evaluate the safety and immune response to a booster dose containing approximately 3300 pfu of virus. Of the subjects, 99% (414/419) maintained antibody to varicella zoster virus (VZV) with a geometric mean titer of 25.7 and mean stimulation index (SI) for VZV-specific lymphoproliferation response of 40.3 +/- 5.3 (SE). Some 7-10 days after the booster immunization, seropositivity rates increased to 100% (302/302), and GMT was 143.6 (anamnestic response). At 6 weeks after the booster inoculation, a subset of subjects had 100% seropositivity (74/74) with a GMT of 218.8 and an SI of 58.6. After 3 months, seropositivity was 100% (358/358), GMT was 119.0, and SI was 61.4.

Colleagues—Varicella-zoster virus (VZV) has been recognized as one of the most frequent viral opportunistic infections in patients infected with the human immunodeficiency virus (HIV). The classic presentation of VZV infection in patients with AIDS is a multidermatomal zoster with or without dissemination. Persistent VZV infections with atypical cutaneous lesions have been recognized with increased frequency [1, 2]. Here we describe the case of an AIDS patient who developed meningoradiculoneuritis while on oral acyclovir given prophylactically at 400 mg twice daily for 8 months after several episodes of multidermatomal zoster. The virus isolated from skin lesions before the start of acyclovir prophylaxis was fully sensitive to acyclovir (isolate 1).

A serum bank maintained for renal transplant recipients allowed for a longitudinal study of antibody responses before and after herpes zoster. Renal transplant recipients without herpes zoster served as controls. Antibody responses to varicella-zoster virus, herpes simplex virus type 1, and cytomegalovirus were measured. The serological responses following herpes zoster were prompt and sustained (in the majority of cases), transient, or not present at all. Zoster without an eruption occurred (apparent only on retrospective chart review) and furnished an explanation for unexplained unilateral pain syndromes in these patients. Asymptomatic rises in titer of antibody to varicella-zoster virus not explained by rises in antibody to herpes simplex virus occurred in both groups. This latter finding points to an unstable relation between virus and host and supports and hypothesis of Hope-Simpson that subclinical release of virus with resulting antigenic stimulation may maintain immunity to varicella-zoster virus. Patients with herpes zoster and controls did not differ in several humoral immune parameters that might have explained the occurrence of herpes zoster. There was no evidence that herpes zoster precipitated renal graft rejection.

Liposomal formulations (distearoylphosphatidylcholine:dipalmitoylphosphatidylglycerol, 9:1) of recombinant human interferon-3ser,7 (IFN-3), administered im to African green monkeys at doses of 107 units/kg on days 1 and 6 after infection with simian varicella virus, resulted in partial protection of the monkeys from viral infection. Aqueous interferon administered under the same dosing regimen was ineffective. When given at 106 units/kg per dose twice daily for 10 d, however, it was highly effective in reducing viremia and rash. The antiviral efficacy obtained with the liposomal IFN-P formulation given in two injections 5 d apart was thus significantly more efficacious than aqueous IFN-I given in the same dosing regimen. However, it was not as efficacious as repeated, twicedaily injections of aqueous IFN-I. Thus, im-injected liposomal IFN-B, which results in sustained release of the IFN-D from the injection site, exerts antiviral efficacy in a primate model superior to that obtained with the identical dosing regimen of aqueous IFN-B. Human recombinant interferon-Oserl7 (IFN-0) is an effective antiviral agent against simian varicella virus (SVV) infection in African green monkeys. We previously demonstrated antiviral efficacy when 1 x 106 units/kg IFN-0 was administered iv twice daily for 10 d [1]. Because dosing twice daily by injection is impractical, we have explored using liposomal formulations of IFN-0 as depots for sustained release of interferon to thus reduce the frequency of

A soluble varicella virus antigen for skin testing was developed using culture fluid from varicella-zoster virus-infected human diploid cells. The culture fluid was centrifuged at a high speed (100,000 g for 2 hr) to remove viral particles, and the supernatant, after heating at 56 C for 30 min, was used as the soluble skin test antigen. No virion or nucleocapsid was found by electron microscopy, and very little 3H-labeled DNA in the soluble antigen hybridized with viral DNA. By immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and fluorography, several viral glycoprotein bands were detected in the soluble antigen. In a comparative skin test on 10 medical students and 10 children using soluble and crude antigens prepared from culture fluid or infected cells, the skin reaction to the soluble antigen tended to be less than that to the crude antigens, but the former reaction correlated well with a history of varicella and the presence or absence of virus-neutralizing antibodies. The skin test measuring reactions to varicella-zoster virus (VZV) was originally developed by Kamiya et al. [1] and Baba et al. [2]. Both groups found that the results of the skin test correlated well with

Eight patients became clinically reinfected with varicella-zoster virus despite the presence of specific antibody in the blood three days to six months before the onset of illness. One patient had had varicella previously; a second had been immunized with live, attenuated varicella vaccine 10 months earlier. While it was suspected that these patients experienced a reactivation of latent virus that caused atypical disseminated zoster rather than varicella, detailed study of the vaccinated child suggests that this was not the case; by restriction-endonuclease techniques, this vaccinee was shown to have been infected with wild-type varicella-zoster virus despite the presence of specific antibody and cellular immunity to the virus. All cases clinically resembled chickenpox. Thus, not only subclinical varicella (manifested by a rise in antibody titer after close exposure) but also clinical reinfection with the virus can occur. Clinical reinfection probably develops more frequently in immunocompromised than in immunocompetent individuals. Reinfections are usually mild.

Lymphocytes obtained from nonimmune children and from adults after an attack of herpes zoster were incubated with antigens of varicella-zoster virus. Lymphocyte transformation, measured by the incorporation of tritiated thymidine, was found to reflect specific immunity to the varicella-zoster virus, although the degree of transformation could not be related to the activity of the disease. Production of interferon was dependent on the method of preparation of lymphocytes and was not related to disease activity or to the immune status of the donors. The interferon-producing and DNA-synthesizing activities could be dissociated by antigen dilution, further suggesting that production of interferon was nonspecific. The extent of immune-specific incorporation of tritiated thymidine by lymphocytes could be increased by incubation of the cultures in the presence of fetal calf serum. Cellular immunity to the varicella-zoster virus can be studied in relation to the risk of infection in immunosuppressed patients, and such work may lead to a better understanding of the phenomenon of latency.

Techniques for assay of in vitro lymphocyte transformation (LTF) were used with varicella-zoster virus (VZV) as the antigen to study the temporal characteristics of the VZV-specific cellular immune response in children with varicella and in normal subjects with a history of the illness. The LTF response in children with only vesicular eruptions was prompt, and individual peak activity was detected within one to two weeks after the onset of illness, followed by a gradual decrease of the activity to lower levels. Patients with a complication of meningoencephalitis showed a marked delay in the development of peak activity. No consistent defference in the development of complement-fixing antibody to VZV was observed in these patients with different clinical manifestations. The LTF response of normal subjects with remote clinical evidence of varicella was characterized by occasional high activity, a finding that suggests reinfection with VZV. These observations provide additional evidence that the specific cellular immune response is heavily involved in the pathogenesis of VZV infection.

A sensitive radioimmunoassay for serum antibody to varicella-zoster virus is described; it uses 125I-labeled staphylococcal protein A and a specially designed immunofiltration apparatus. The assay accurately distinguishes between individuals who are susceptible and those who are immune to infection with varicella-zoster virus. In addition, it can detect passive antibody in recipients of varicella-zoster immune globulin. This radioimmunoassay also detects the heterologous antibody responses that occasionally occur in patients infected with herpes simplex virus, which also have been detected by other antibody assays. The particular advantages of this assay are the use of noninfectious reagents, the speed of execution (less than 3 hr), the requirement for only small quantities of serum (30 microliters), the objectivity of end-point determination, and the capability of screening large numbers of sera. Consequently, this radioimmunoassay is especially useful for the rapid identification of susceptible individuals, which is essential for the appropriate management of patients and hospital personnel after exposure to varicella.

2'-Fluoro-5-iodoarabinosylcytosine (FIAC) has potent antiviral activity in vivo against herpes simplex virus types 1 and 2 and cytomegalovirus. For examination of the clinical efficacy of FIAC, a randomized, double-blind study of FIAC versus adenine arabinoside (ara-A) was conducted in 34 immunosuppressed individuals with varicella-zoster virus infections. The median time to the appearance of the last new lesion was shorter in patients who received FIAC relative to those who received ara-A (two versus five days, respectively; P less than .001) FIAC also reduced pain and accelerated initial crusting within 72 hr in a significantly greater proportion of patients when compared with ara-A (P = .004 and P = .0009, respectively). FIAC caused few toxic reactions (mild nausea and transient elevation in activity of serum aspartate aminotransferase). Thus FIAC is therapeutically superior to ara-A for the treatment of varicella-zoster virus infections in immunosuppressed subjects.

Three groups of patients were evaluated to determine the relation between viremia caused by varicella-zoster virus and the type of varicella course the patient had. The groups were: (1) children with varicella who had no known underlying disease, who were not receiving immunosuppressive therapy, and who had a typical course of varicella ("normal" children); (2) children who were considered to be at risk of developing progressive varicella because of preexisting disease or because they were receiving immunosuppressive therapy and who had a typical course of varicella; and (3) patients who were at risk of developing progressive varicella and who had a progressive varicella course. Viremia in association with exanthem occurred in patients who had a progressive varicella course, but it was not observed, either during incubation or exanthem, in normal children or in patients at risk of progressive infection who had a typical varicella course. The viremia was cell-associated in three patients.

Replication of varicella-zoster virus (VZV) and immunologic responses to VZV were examined by a sensitive culture technique for viral isolation and standard immunologic assays in children after close exposure to wild-type VZV or after inoculation with strain Oka varicella vaccine. Naturally infected children who developed clinical varicella had viremia between five days before and one day after clinical onset of disease, with the highest isolation rate one and two days before onset, and seroconversion followed two days later. Virus was not isolated from blood 12 and 13 days after contact in subclinically infected children. In the vaccine recipients a positive skin test reaction to VZV was observed as early as four to five days after immunization, and antibody appeared later. Virus was not isolated from blood and throat of the vaccinees from three to 14 days after immunization.

Humoral immunity following infection with varicella-zoster virus (VZV) was evaluated by a complement-enhanced neutralization test. The specificity of the test was examined and its sensitivity compared with that of the assay which measures antibody to VZV-induced membrane antigen (FAMA). Generally, the titer of neurtalizing antibody was two- to fourfold higher than the FAMA titer. The absence of neutralizing activity at a serum dilution of 1:4 indicated susceptibility of the donor to VZV infection and correlated with an absence of FAMA (titer, less than 1:2). A survey of susceptible leukemic children exposed to chicken pox revealed that several recipients of zoster immune globulin had a subclinical infection, as manifested by seroconversion and persistence of neutralizing antibody to VZV. Results of these studies indicate that the complement-enhanced neutralization test is a sensitive and specific assay for determination of humoral immune status with regard to VZV in healthy and immunosuppressed individuals.