Prophylaxis of varicella in high-risk children: dose-response effect of zoster immune globulin

A quick algorithmic review on management of viral infectious diseases in pediatric solid organ transplant recipients

Pediatric solid organ transplant is a life-saving procedure for children with end-stage organ failure. Viral infections are a common complication following pediatric solid organ transplantation (SOT), which can lead to increased morbidity and mortality. Pediatric solid organ transplant recipients are at an increased risk of viral infections due to their immunosuppressed state. The most commonly encountered viruses include cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus (HSV), varicella-zoster virus (VZV), adenoviruses, and BK polyomavirus. Prevention strategies include vaccination prior to transplantation, post-transplant prophylaxis with antiviral agents, and preemptive therapy. Treatment options vary depending on the virus and may include antiviral therapy and sometimes immunosuppression modification. This review provides a Quick Algorithmic overview of prevention and treatment strategies for viral infectious diseases in pediatric solid organ transplant recipient.

PEPtalk 3: oral aciclovir is equivalent to varicella zoster immunoglobulin as postexposure prophylaxis against chickenpox in children with cancer - results of a multicentre UK evaluation

OBJECTIVE

To compare the occurrence of chickenpox in children with cancer who received varicella immunoglobulin (VZIG) or aciclovir as postexposure prophylaxis (PEP).

DESIGN

Prospective multicentre service evaluation of children with cancer who received either VZIG or aciclovir as PEP following significant exposure to varicella zoster virus (VZV) over a 24-month period from May 2018.

SETTING

Data were collected from 9 UK Paediatric Oncology Primary Treatment Centres.

PATIENTS

Children under 16 years old with a diagnosis of cancer and/or previous haematopoietic stem cell transplant who were VZV seronegative at exposure and/or diagnosis and received PEP following significant VZV exposure.

MAIN OUTCOME MEASURES

The primary outcome was the incidence of breakthrough varicella within 6 weeks of VZV exposure and treatment with PEP.

RESULTS

A total of 105 eligible patients were registered with a median age of 4.9 years (range 1.1-10.5 years). Underlying diagnoses were acute leukaemia (64), solid tumours (22), Langerhans cell histiocytosis (9), central nervous system (CNS) tumours (8) and other (2). Aciclovir was received by 86 patients (81.9%), 18 received VZIG (17.1%) and 1 valaciclovir (0.9%). There were seven reported break-through VZV infections in 103 patients at follow-up (7/103, 6.8%). Clinical VZV developed in 5/84 of the aciclovir group (6.0%, 95% CI 2.0 to 13.3) and 2/18 of VZIG group (11.1%, 95% CI 1.4 to 34.7). All breakthrough infections were either mild (5/7) or moderate (2/7) in severity.

CONCLUSION

Aciclovir is a safe and effective alternative to VZIG as VZV PEP in children with cancer and should be considered as standard of care.

Varicella zoster virus in inflammatory bowel disease patients: what every gastroenterologist should know

Primary Varicella Zoster virus (VZV) infection results in varicella (chickenpox) while its reactivation results in herpes zoster (HZ; shingles). Patients with Inflammatory Bowel Disease (IBD) are susceptible to complications of primary VZV infection and have an increased risk of HZ. Concerns of VZV and HZ infection in the IBD population has been highlighted by the emergence of JAK-inhibitors and their safety profile in this patient population such as tofacitinib for the treatment of ulcerative colitis (UC). The current pipeline of emerging therapies include novel molecules targeting multiple pathways including JAK/signal transducer and cytokine signalling pathways such as JAK/STAT. Hence VZV and HZ will be increasingly relevant for gastroenterologists treating IBD patients in light of these emerging therapies.

Varicella zoster virus in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice review the diagnosis, prevention, and management of varicella zoster virus (VZV) in the pre- and post-transplant period. Primary varicella is an uncommon complication post-solid-organ transplant (SOT), except among pediatric transplant patients and those seronegative for VZV. As the majority of SOT recipients are seropositive for VZV, herpes zoster (HZ) occurs frequently following SOT, particularly among recipients who are older (≥65 years of age) and those receiving more intensive immunosuppression. Transplant providers should aware of the increased risk for HZ-related complications such as dissemination, organ-specific involvement, and post-herpetic neuralgia. Treatment for localized zoster is primarily given as oral regimens, but those with more complicated presentations or those at risk for dissemination should be treated initially with IV therapy. Available antiviral prophylaxis regimens and vaccination strategies for varicella and HZ among these immunosuppressed patients remain a mainstay for prevention in the pre-and post-transplant periods. Finally, we discuss important approaches to addressing post-exposure prophylaxis and infection control practices for those SOT patients with documented VZV infections.

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.

PEPtalk2: results of a pilot randomised controlled trial to compare VZIG and aciclovir as postexposure prophylaxis (PEP) against chickenpox in children with cancer

OBJECTIVE

To determine the likely rate of patient randomisation and to facilitate sample size calculation for a full-scale phase III trial of varicella zoster immunoglobulin (VZIG) and aciclovir as postexposure prophylaxis against chickenpox in children with cancer.

DESIGN

Multicentre pilot randomised controlled trial of VZIG and oral aciclovir.

SETTING

England, UK.

PATIENTS

Children under 16 years of age with a diagnosis of cancer: currently or within 6 months of receiving cancer treatment and with negative varicella zoster virus (VZV) serostatus at diagnosis or within the last 3 months.

INTERVENTIONS

Study participants who have a significant VZV exposure were randomised to receive PEP in the form of VZIG or aciclovir after the exposure.

MAIN OUTCOME MEASURES

Number of patients registered and randomised within 12 months of the trial opening to recruitment and incidence of breakthrough varicella.

RESULTS

The study opened in six sites over a 13-month period. 482 patients were screened for eligibility, 32 patients were registered and 3 patients were randomised following VZV exposure. All three were randomised to receive aciclovir and there were no cases of breakthrough varicella.

CONCLUSIONS

Given the limited recruitment to the PEPtalk2 pilot, it is unlikely that the necessary sample size would be achievable using this strategy in a full-scale trial. The study identified factors that could be used to modify the design of a definitive trial but other options for defining the best means to protect such children against VZV should be explored.

TRIAL REGISTRATION NUMBER

ISRCTN48257441, EudraCT number: 2013-001332-22, sponsor: University of Birmingham.

Implementation of Hospital Policy for Healthcare Workers and Patients Exposed to Varicella-Zoster Virus

Varicella-zoster virus (VZV) causes a highly contagious and generally benign, self-limited disease. However, in high-risk populations including immunocompromised patients, pregnant women, and neonates, VZV infection can be associated with significant morbidity and mortality. Healthcare-associated transmission of VZV occurs among healthcare workers (HCWs) and patients by airborne transmission or by direct contact with the index case. To minimize the risk of transmission in healthcare settings, all VZV-susceptible HCWs should be encouraged strongly to be immunized with the varicella vaccine. For post-exposure management, active immunization (varicella vaccine), passive immunization (varicella-zoster immune globulin) and/or antiviral agents, and isolation could be used in specific situations. To prevent the transmission of VZV infection in the hospital settings, the development and implementation of hospital policies for appropriate infection control is also warranted. This article reviews the general information and healthcare-associated transmission of VZV and summarizes the recommendations for the pre- and post-exposure management of HCWs and patients, in hospital settings.

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.

Postexposure Prophylaxis Against Varicella-Zoster Virus Infection Among Recipients of Hematopoietic Stem Cell Transplant: Unresolved Issues

Recent guidelines for the prevention of opportunistic infections have addressed a variety of issues germane to recipients of hematopoietic stem cell transplant. However, there are several issues regarding postexposure prophylaxis against varicella-zoster virus that remain unresolved. We address these questions and offer several consensus recommendations.

Abortive intrabronchial infection of rhesus macaques with varicella-zoster virus provides partial protection against simian varicella virus challenge

Varicella-zoster virus (VZV) is a human neurotropic alphaherpesvirus and the etiological agent of varicella (chickenpox) and herpes zoster (HZ, shingles). Previously, inoculation of monkeys via the subcutaneous, intratracheal, intravenous, or oral-nasal-conjunctival routes did not recapitulate all the hallmarks of VZV infection, including varicella, immunity, latency, and reactivation. Intrabronchial inoculation of rhesus macaques (RMs) with simian varicella virus (SVV), a homolog of VZV, recapitulates virologic and immunologic hallmarks of VZV infection in humans. Given that VZV is acquired primarily via the respiratory route, we investigated whether intrabronchial inoculation of RMs with VZV would result in a robust model. Despite the lack of varicella and viral replication in either the lungs or whole blood, all four RMs generated an immune response characterized by the generation of VZV-specific antibodies and T cells. Two of 4 VZV-inoculated RMs were challenged with SVV to determine cross-protection. VZV-immune RMs displayed no varicella rash and had lower SVV viral loads and earlier and stronger humoral and cellular immune responses than controls. In contrast to the results for SVV DNA, no VZV DNA was detected in sensory ganglia at necropsy. In summary, following an abortive VZV infection, RMs developed an adaptive immune response that conferred partial protection against SVV challenge. These data suggest that a replication-incompetent VZV vaccine that does not establish latency may provide sufficient protection against VZV disease and that VZV vaccination of RMs followed by SVV challenge provides a model to evaluate new vaccines and therapeutics against VZV.

IMPORTANCE

Although VZV vaccine strain Oka is attenuated, it can cause mild varicella, establish latency, and in rare cases, reactivate to cause herpes zoster (HZ). Moreover, studies suggest that the HZ vaccine (Zostavax) only confers short-lived immunity. The development of more efficacious vaccines would be facilitated by a robust animal model of VZV infection. The data presented in this report show that intrabronchial inoculation of rhesus macaques (RMs) with VZV resulted in an abortive VZV infection. Nevertheless, all animals generated a humoral and cellular immune response that conferred partial cross-protection against simian varicella virus (SVV) challenge. Additionally, VZV DNA was not detected in the sensory ganglia, suggesting that viremia might be required for the establishment of latency. Therefore, VZV vaccination of RMs followed by SVV challenge is a model that will support the development of vaccines that boost protective T cell responses against VZV.

CD4 T cell immunity is critical for the control of simian varicella virus infection in a nonhuman primate model of VZV infection

Primary infection with varicella zoster virus (VZV) results in varicella (more commonly known as chickenpox) after which VZV establishes latency in sensory ganglia. VZV can reactivate to cause herpes zoster (shingles), a debilitating disease that affects one million individuals in the US alone annually. Current vaccines against varicella (Varivax) and herpes zoster (Zostavax) are not 100% efficacious. Specifically, studies have shown that 1 dose of varivax can lead to breakthrough varicella, albeit rarely, in children and a 2-dose regimen is now recommended. Similarly, although Zostavax results in a 50% reduction in HZ cases, a significant number of recipients remain at risk. To design more efficacious vaccines, we need a better understanding of the immune response to VZV. Clinical observations suggest that T cell immunity plays a more critical role in the protection against VZV primary infection and reactivation. However, no studies to date have directly tested this hypothesis due to the scarcity of animal models that recapitulate the immune response to VZV. We have recently shown that SVV infection of rhesus macaques models the hallmarks of primary VZV infection in children. In this study, we used this model to experimentally determine the role of CD4, CD8 and B cell responses in the resolution of primary SVV infection in unvaccinated animals. Data presented in this manuscript show that while CD20 depletion leads to a significant delay and decrease in the antibody response to SVV, loss of B cells does not alter the severity of varicella or the kinetics/magnitude of the T cell response. Loss of CD8 T cells resulted in slightly higher viral loads and prolonged viremia. In contrast, CD4 depletion led to higher viral loads, prolonged viremia and disseminated varicella. CD4 depleted animals also had delayed and reduced antibody and CD8 T cell responses. These results are similar to clinical observations that children with agammaglobulinemia have uncomplicated varicella whereas children with T cell deficiencies are at increased risk of progressive varicella with significant complications. Moreover, our studies indicate that CD4 T cell responses to SVV play a more critical role than antibody or CD8 T cell responses in the control of primary SVV infection and suggest that one potential mechanism for enhancing the efficacy of VZV vaccines is by eliciting robust CD4 T cell responses.

Varicella zoster virus (VZV) causes chickenpox and establishes a life-long latent infection in humans. VZV can reactivate years later to cause shingles, a debilitating and painful disease. Vaccines against both chickenpox and shingles are available but not 100% efficacious. Two doses of the chickenpox vaccine are required to provide adequate protection and the shingles vaccine reduces the incidence of this disease by 51%. To improve these vaccines, we must identify the components of the immune system that are important for the control of VZV replication. However, the contribution of T versus B cell responses is unknown. Infection of rhesus macaques with simian varicella virus is a robust model of VZV infection. Here, we used this unique animal model to show for the first time that the absence of B cells does not alter disease severity and that the loss of CD8 T cells only results in a mild increase in disease severity. In sharp contrast, the lack of CD4 T cells leads to disseminated varicella. These data highlight the importance of CD4 T cells and suggest that novel vaccines that focus on engendering a more robust CD4 T cell response against VZV might provide better protection from chickenpox and shingles.

Preventing varicella in children with malignancies: what is the evidence?

PURPOSE OF REVIEW

The prevention of varicella in children with cancer is generally agreed to be an important goal, because of their elevated risk of varicella zoster virus (VZV)-associated morbidity and mortality. However, there is a lack of consensus on the best means of achieving this. Here, we review the existing evidence in relation to postexposure prophylaxis against varicella in this group and summarize data regarding the role of active vaccination.

RECENT FINDINGS

Death from varicella during treatment for cancer is now rare, but VZV disease and its prevention remain significant problems in paediatric oncology practice. Measures to reduce VZV exposure amongst seronegative individuals are often neglected. When exposure is known to have occurred, early administration of varicella zoster immune globulin (VZIG) is generally protective against severe and complicated varicella. However, many centres in the UK and Japan use an oral antiviral agent, aciclovir, in place of VZIG. Published evidence for the efficacy of aciclovir as postexposure prophylaxis (PEP) relates mostly to healthy children, with no controlled studies in the immunocompromised.

SUMMARY

Good evidence already supports the administration of varicella vaccine to healthy susceptible family contacts of children with malignancy, but not to patients themselves. Further data are urgently needed to inform the choice of PEP against VZV in the immunocompromised.

Management of HSV, VZV and EBV infections in patients with hematological malignancies and after SCT: guidelines from the Second European Conference on Infections in Leukemia

These guidelines on the management of HSV, VZV and EBV infection in patients with hematological malignancies and after SCT were prepared by the European Conference on Infections in Leukemia following a predefined methodology. A PubMed search was conducted using the appropriate key words to identify studies pertinent to management of HSV, VZV and EBV infections. References of relevant articles and abstracts from recent hematology and SCT scientific meetings were also reviewed. Prospective and retrospective studies identified from the data sources were evaluated, and all data deemed relevant were included in this analysis. The clinical and scientific background was described and discussed, and the quality of evidence and level of recommendation were graded according to the Centers for Disease Control criteria.

Comparison of two different preparations of HIV immune globulin for efficiency of neutralization of HIV type 1 primary isolates

The objective of this study was to compare the virus-neutralizing ability of two different preparations of HIV immune globulin (HIVIG) isolated from human plasma units that were selected according to two different criteria. The first preparation, designated NYBC-HIVIG, was isolated from plasmas with high neutralizing antibody titers against HIV-1. The second preparation, designated NABI-HIVIG, was isolated from plasma with high titers of antibody to the HIV-1 p24 antigen. A panel of primary HIV-1 isolates was phenotypically characterized by their ability to induce syncytia in CEM-SS cells. Neutralization of this panel of primary isolates by the two HIVIG preparations was assessed in HeLa-MAGI-CCR5 cells, utilizing a luminescence-based assay. In addition, the reactivities of these two preparations with a panel of HIV-1 gp120 proteins, V3 loop peptides, and HIV-1 p24 antigen were determined. Both HIVIG preparations were shown to neutralize all virus isolates tested. However, doses of NABI-HIVIG required for 50% virus neutralization were 2.2- to 4.4- fold (mean, 3.2-fold) higher than the required doses of NYBC-HIVIG. Comparative antigen-binding assays showed that, although NABI-HIVIG possessed higher titers of antibody to HIV-1 p24, NYBC-HIVIG generally contained higher titers of antibody to HIV-1 gp120 and V3 peptides. These experiments show that the criteria used for selection of source plasmas for isolation of HIVIG can influence the effective concentration of virus-neutralizing antibody present in the final immunoglobulin preparation, and may determine the doses required for clinical efficacy.

Efficacy of polyclonal antibodies for treatment of ocular herpes simplex infection

PURPOSE

Herpes simplex virus (HSV) can cause corneal infections in humans and lead to permanent scarring, loss of vision, and blindness. Current treatment of epithelial HSV keratitis consists of using antiviral DNA analogs. In this study, we used in vitro and in vivo models to evaluate the efficacy of six polyclonal antibodies to HSV recombinant surface glycoprotein D in treating ocular epithelial HSV.

METHODS

Confluent cultures of African Green monkey kidney fibroblasts (Vero cells) and normal 3-to 5-lb female New Zealand White rabbits were infected with HSV type 1, strain RE. In vitro virucidal and antiviral assays were performed, and the best of the compounds was chosen for the in vivo stage. Animals were carefully monitored until day 5 after HSV-1 inoculation, then arbitrarily divided into groups receiving, for 14 days, varying doses of: polyclonal antibodies four times a day, polyclonal antibodies three times a day, trifluorothymidine (current treatment of choice and the positive control) nine times a day, or 0.9% physiologic saline nine times a day. The animals were followed up in a masked fashion and carefully monitored for severity and resolution of the HSV infection by biomicroscopy (slit lamp) examination and viral cultures using standardized plaque assays.

RESULTS

All six of the compounds tested were effective in vitro, but one compound in particular, SP-510-50, was superior. It was used for the in vivo testing and showed antiviral efficacy in a dose-dependent manner, and at dosing four times a day, it was of comparable efficacy to trifluorothymidine (nine times a day).

CONCLUSIONS

We conclude that polyclonal antibodies to glycoprotein D appear to be effective antiviral agents in vitro and in vivo in a rabbit model of HSV-1 keratitis and show promise as a new antiviral treatment for ophthalmic use.

Immunoglobulin G3 from polyclonal human immunodeficiency virus (HIV) immune globulin is more potent than other subclasses in neutralizing HIV type 1

Passive antibody prophylaxis against human immunodeficiency virus type 1 (HIV-1) has been accomplished in primates, suggesting that this strategy may prove useful in humans. While antibody specificity is crucial for neutralization, other antibody characteristics, such as subclass, have not been explored. Our objective was to compare the efficiencies of immunoglobulin G (IgG) subclasses from polyclonal human HIV immune globulin (HIVIG) in the neutralization of HIV-1 strains differing in coreceptor tropism. IgG1, IgG2, and IgG3 were enriched from HIVIG by using protein A-Sepharose. All three subclasses bound major HIV-1 proteins, as shown by Western blot assay and enzyme-linked immunosorbent assay. In HIV-1 fusion assays using X4, R5, or X4R5 envelope-expressing effector cells, IgG3 more efficiently blocked fusion. In neutralization assays with cell-free viruses using X4 (LAI, IIIB), R5 (BaL), and X4R5 (DH123), a similar hierarchy of neutralization was found: IgG3 > IgG1 > IgG2. IgG3 has a longer, more flexible hinge region than the other subclasses. To test whether this is important, IgG1 and IgG3 were digested with pepsin to generate F(ab')(2) fragments or with papain to generate Fab fragments. IgG3 F(ab')(2) fragments were still more efficient in neutralization than F(ab')(2) of IgG1. However, Fab fragments of IgG3 and IgG1 demonstrated equivalent neutralization capacities and the IgG3 advantage was lost. These results suggest that the IgG3 hinge region confers enhanced HIV-neutralizing ability. Enrichment and stabilization of IgG3 may therefore lead to improved HIVIG preparations. The results of this study have implications for the improvement of passive immunization with polyclonal or monoclonal antibodies and suggest that HIV-1 vaccines which induce high-titer IgG3 responses could be advantageous.

A 15-year experience with varicella infections in a pediatric burn unit

Because of their well described global immunosuppression, varicella infection may be hazardous in burned children. It is therefore important to prevent cross-infections within pediatric burn units. We describe a 15-year experience with varicella in a pediatric burn unit, focusing on the morbidity associated with the infection and measures that have been effective in the prevention of cross-infection. We found that varicella infection in acutely burned children is associated with pneumonitis, but little wound related morbidity. Despite the deceptively long incubation period, prompt identification and isolation of index cases was associated with an extremely low incidence of cross-infection. Until widespread administration of varicella vaccine confers herd immunity, varicella remains a threat to hospitalized young children, highlighting the importance of a well planned and executed index case isolation strategy.

Antiviral prophylaxis and treatment in chickenpox. A review prepared for the UK Advisory Group on Chickenpox on behalf of the British Society for the Study of Infection

Prophylactic intervention with varicella-zoster immunoglobulin early in the incubation period can prevent or attenuate the disease manifestations of varicella in susceptible contacts at high risk from this infection. Detailed guidelines are issued in the UK Department of Health publication on Immunization against Infectious Disease. Sensitive immunoassays are available for investigation of antibody status and subclinical seroconversion. Live attenuated varicella vaccine, which has been used successfully post-exposure as well as electively elsewhere, is at present not generally available in the UK. Effective protocols for prophylaxis against varicella with the antiviral agent aciclovir are not yet established. The nucleoside analogue aciclovir (syn: acyclovir, Zovirax) is effective in inhibiting replication of VZV when given at a dosage higher than that required for treatment of HSV, and is currently the only available and approved treatment for varicella in the U.K. Intravenous aciclovir therapy for 5-10 days is effective for varicella in neonates and the immunocompromised, and for varicella pneumonia or other complications in adults and children, if begun early. Oral aciclovir is only effective if begun with 24 h of onset of rash. With that proviso. it is recommended for treatment of varicella in otherwise healthy adults and adolescents, but not for routine use in children under 13 years of age unless they are sibling contacts or have other medical conditions. Aciclovir has a high therapeutic index and good safety profile, but caution is advised with use in pregnancy.

Pharmacokinetics of hyperimmune anti-human immunodeficiency virus immunoglobulin in persons with AIDS

Hyperimmune anti-human immunodeficiency virus immunoglobulin (HIVIG) is an intravenous immunoglobulin prepared from HIV-infected asymptomatic donors with a CD4 cell count greater than 400 cells/microl and a high titer of antibody to HIV-1 p24 protein. Twelve persons with AIDS received four doses of HMG (two at 50 mg/kg of body weight and then two at 200 mg/kg) every 28 days. Pharmacokinetics were evaluated by measurement of anti-p24 antibody. HIVIG was well tolerated, and all participants completed the study. Three subjects who were not receiving Pneumocystis carinii pneumonia (PCP) prophylaxis developed PCP. The mean value for HIVIG clearance was 3.02 ml/kg/day at 50 mg/kg and 3.65 ml/kg/day at 200 mg/kg (P = 0.027); the mean trough antibody titers (reciprocal units) were 1,442 and 4,428, respectively. This study indicates that high titers of anti-p24 antibody can be maintained with a monthly administration schedule of HIVIG and that short-term safety is acceptable. Comparisons to evaluate the therapeutic potential of HIVIG are justified.

Simian varicella virus antibody response in experimental infection of African green monkeys

The humoral immune response to simian varicella virus (SVV) was investigated following primary and secondary experimental infection of African green monkeys. Neutralization and immunoprecipitation assays were used to determine antibody titers to SVV throughout the course of infection. The immune response to specific viral polypeptides was analyzed by immunoprecipitation analysis. The results demonstrate that the simian varicella model offers a useful approach to investigate immune mechanisms in human varicella zoster virus (VZV) infections.

Fatal varicella in steroid-dependent asthma

Disseminated varicella infection is a potentially life-threatening complication of chronic high-dose corticosteroid (CS) or immunosuppressive therapy. A review of the literature indicates that, with one possible exception, this complication has not occurred in a CS-dependent subject with asthma. We present in this article the clinical features and autopsy findings of a steroid-dependent subject with asthma who died of acute, disseminated varicella. A 16-year-old poorly compliant, steroid-dependent subject with asthma received two courses of high-dose intravenous methylprednisolone during a 3-week period, followed by a tapering schedule of oral prednisone. During this time, she was exposed to chickenpox. She subsequently developed a classic varicella rash, sever back pain, rapidly progressive hepatic failure, pneumonitis, and encephalopathy. Death ensued 3 days after the onset of the rash. Evidence of disseminated varicella infection was confirmed at autopsy. This case illustrates that a small number of subjects with severe asthma receiving high-dose CS need to be considered as a separate, high-risk group for developing disseminated varicella. We recommend that the immune status of these patients to varicella-zoster virus be assessed by a serum titer. If these patients are nonimmune, they would be candidates for varicella-zoster immune globulin on exposure, and for acyclovir therapy should varicella dissemination occur.

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.

The potency determination of human varicella-zoster immunoglobulin by enzyme-linked immunosorbent assay, complement-fixation test and indirect fluorescent antibody tests

Traditionally, plasma for the production of the human varicella-zoster immunoglobulin (VZIG) has been selected on the basis of the complement-fixing antibody (CFA) titre. Since immune individuals may lack CFA to varicella-zoster virus (VZV), non-CFA may be of importance in protection. In a search for a simple and reliable method for potency determination, 24 VZIG preparations were quantified by enzyme-linked immunosorbent assay (ELISA), the complement-fixation test (CFT), the indirect fluorescent antibody test to acetone-fixed (IF) and viable (FAMA) VZV-infected cells, respectively. The antibody titres obtained by the various methods were compared. Arranged in order of decreasing agreement, the correlation coefficients (r) of the regression equations between the variables were 0.62 for CFT and FAMA, 0.50 for CFT and ELISA and 0.26 for CFT and IF in a log2 plot. There was complete agreement between the titres obtained by the commercially available Enzygnost Varicella/Zoster kits (Behring Institute, Marburg, F.R. Germany) and the ELISA microtitre plates produced at our institute (r = 1). The regression equation lines for ELISA/CFT and FAMA/CFT titres tended to be parallel to each other, while the line for IF/CFT titres had a less steep slope. Similar titration curves were obtained for VZIGs fractionated by two different methods. Furthermore, the titration curves of serum pools from varicella and zoster convalescents, respectively, had a similar shape below delta OD = 0.4. Generally, a steeper slope was observed above delta OD = 0.4. As antibody detectable by ELISA seems to correlate with protection and the method is sensitive, specific, reproduceable, simple to carry out and easily automated, it may be suitable for the potency determination of VZIGs.

Short-time and low-dose intravenous acyclovir therapy in varicella zoster infections with malignant disease in children receiving combined chemotherapy

The effects of low-dose and short-time acyclovir therapy in 14 children with malignant disease of ages 4-18 years who had developed varicella zoster virus infections while receiving aggressive chemo-/+radiotherapy are reported. Ten of them had chickenpox and 4 herpes zoster. Acyclovir 5 mg/kg was infused IV every 12 h in 9 patients and every 8 h in 5 patients for a median of 4 days' duration. We resumed the primary therapy when the patients' lesions had dried out and became crusted and new lesions had not reappeared. The period of initiation of the acyclovir therapy to the resumption of oncological treatment was 8.4 +/- 2.7 days for chickenpox and 12.0 +/- 3.4 days for herpes zoster patients. After restarting the oncological therapy, no adverse effects of acyclovir or complication of infection were observed. The efficiency of early, short-term, and relatively low dose acyclovir therapy is discussed and compared to the results in the relevant literature.

Oncologic emergencies II. Hematologic and infectious complications of cancer and cancer treatment

Proper supportive care of the child with cancer is necessary to maximize the child's quality and length of life. This article discusses the pathophysiology, diagnosis, and management of the common hematologic and infectious complications of childhood cancer that the primary care physician must face.

Comparison of varicella zoster antibody titers in patients given intravenous immune serum globulin or varicella zoster immune globulin

We compared the VZV IgG antibody titers after administration of varicella zoster immune globulin and serum immune globulin intravenously (IGIV) in VZV seronegative pediatric patients with cancer. Four patients received VZIG at standard doses; four received IGIV at 4 ml/kg every 4 weeks for four doses; and five received IGIV at 6 ml/kg every 6 weeks for two to four doses. VZV antibody titers were measured by radiommunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody assay (IFA), and neutralizing antibody assay. The mean peak and trough VZV titers by RIA were comparable in all three groups: 1:724 at 4 weeks after VZIG, 1:2048 at 4 weeks after 4 ml/kg IGIV, and 1:776 at 6 weeks after 6 ml/kg IGIV. The titers measured by ELISA, IFA, and neutralizing antibody were comparable after VZIG or IGIV. The VZV titers by RIA were maintained at greater than or equal to 1:1024 after subsequent doses of 4 ml/kg IGIV, and at greater than or equal to 1:256 after subsequent doses of 6 ml/kg IGIV. Adverse effects were rare. The VZV antibody titers assessed 4 to 6 weeks after IGIV administration were equivalent to the titers measured 4 weeks after administration of VZIG.

Symposium on infectious complications of neoplastic disease (Part II). Immunoprophylaxis of varicella-zoster infections

Because it is possible to identify groups of persons with a high risk of varicella development and also because it is possible to anticipate when an attack may occur, immunoprophylaxis for varicella has met with great success. In contrast, the nature of zoster--its unpredictability and low attack rate--makes immunoprophylaxis much more difficult to implement. Varicella may be modified by administration of varicella-zoster immune globulin within three days of a known exposure to the virus. Although interferon has not yet been used in an attempt to prevent or modify varicella in humans, it has been used successfully to abort an outbreak of simian varicella in a monkey colony. Thus it might be clinically useful, particularly for those who cannot be given varicella-zoster immune globulin within three days of exposure. Transfer factor has also been shown to induce at least partial immunity to varicella in children with leukemia. The duration of this protection is unknown, and further study of the efficacy of transfer factor against both varicella and possibly even against zoster seems warranted. Live attenuated varicella vaccine, although still experimental, seems now to be the most practical way to prevent severe varicella in high-risk persons. The vaccine is safe and immunogenic, even in children with underlying leukemia who are still receiving chemotherapy. Studies in Japan, Europe, and the United States have shown that most vaccinated leukemic children who are exposed are protected against severe disease, although mild breakthrough cases have been reported. Varicella vaccine's potential to cause zoster remains under study.

Varicella zoster antibody titers after the administration of intravenous immune serum globulin or varicella zoster immune globulin

Varicella is a serious infection in the immunocompromised patient. Prophylaxis with varicella zoster immune globulin is known to decrease the incidence of severe varicella infection. The titers of antibody to varicella zoster virus were compared in patients who received either varicella zoster immune globulin or intravenous immune globulin, 4 ml or 6 ml/kg per dose. The titers of antibody to varicella zoster virus were comparable in each group.

Acyclovir therapy of chickenpox in immunosuppressed children--a collaborative study

A randomized double-blind, placebo-controlled, multicenter investigation assessed the usefulness of acyclovir in the treatment of immunosuppressed children with chickenpox. Twelve patients received placebo and eight received acyclovir. If the event of clinical deterioration, patients could be removed from the study to receive acyclovir. Eighteen patients had skin lesions within 96 hours of admission to the study. Nineteen patients had malignancies. The two groups of patients were similar in age, in concomitant or preceding immunosuppressive therapy, in status of malignancy, and in presenting granulocyte and lymphocyte counts. Zoster immune globulin or plasma had been given to 50% of the placebo group but to only 25% of the acyclovir group. One patient in each group had pneumonitis at entry. Of the patients without pneumonitis at entry, five of the 11 placebo patients compared with none of the seven acyclovir patients developed pneumonitis during treatment (P = 0.054). No evidence of toxicity related to acyclovir was observed.