Chickenpox virus

Structural and Synthetic Aspects of Small Ring Oxa- and Aza-Heterocyclic Ring Systems as Antiviral Activities

Antiviral properties of different oxa- and aza-heterocycles are identified and properly correlated with their structural features and discussed in this review article. The primary objective is to explore the activity of such ring systems as antiviral agents, as well as their synthetic routes and biological significance. Eventually, the structure-activity relationship (SAR) of the heterocyclic compounds, along with their salient characteristics are exhibited to build a suitable platform for medicinal chemists and biotechnologists. The synergistic conclusions are extremely important for the introduction of a newer tool for the future drug discovery program.

Comparison between of the attenuated BR-Oka and the wild type strain of Varicella Zoster Virus (VZV) on the DNA level

Oka strain VR-795 (Varicella Zoster Virus, VZV) of American Type Culture Collection (ATCC) has been used for chickenpox vaccine production. In order to use this strain for vaccine production, the strain must be identified and its stability must be confirmed. The identification of the Oka strain has been confirmed using Restriction Fragment Length Polymorphism (RFLP) and DNA sequence analysis of glycoprotein-II (gp-II). The amino acid sequences of Oka deduced from the DNA sequence of gp-II have changed at three amino acids against Ellen and at one amino acid against Webster. To prove the stability of the Oka strain during the passage, RFLP and DNA sequence analyses were also used with 11, 15 and 23 times of virus passage. We found that the Oka strain was stable at passages of up to 23 times, based on the RFLP and DNA sequence analyses. The confirmed Oka strain was renamed as BR-Oka for the purposes of chickenpox vaccine production.

The new varicella vaccine: efficacy, safety, and administration

Since the FDA has given approval for the manufacture of a varicella vaccine (Varivax), nurses are beginning to administer the vaccine to children. Over 11,000 healthy and immunocompromised children have been immunized since 1979. Varivax has been found to be 95% to 100% effective in conferring immunity for at least 10 years, and it appears to be a safe vaccine. This article presents a review of the research literature on clinical trials of Varivax, and the risks, benefits, and projected cost of the vaccine. Precautions, contraindications, and guidelines for administration are tabled and discussed in a sample case using the Health Belief Model as a theoretical framework. The article includes a discussion of areas for further research and implications for nursing.

The varicella vaccine. Vaccine development

In this article, rationales and method of development of attenuated live varicella (Oka) vaccine are described, with biologic and biophysical characteristics of the vaccine virus. The results of early clinical trials in Japan are also described, along with the results of detection of viremia in vaccinees and a follow-up of incidence of zoster in acute leukemic children, which indicate possible immunopathogenesis of varicella and zoster.

The epidemiology of varicella-zoster virus infections: the influence of varicella on the prevalence of herpes zoster

This paper uses mathematical models and data analysis to examine the epidemiological implications of possible immunologically mediated links between patterns of varicella and herpes-zoster incidence in human communities. A review of previously published reports does not clarify whether or not there is a relationship between the incidence of varicella and the incidence of zoster. However, new analysis of data collected by the Royal College of General Practitioners provides indirect evidence for the hypothesis that a high intensity of varicella transmission suppresses viral reactivation. The significance of this finding for proposed varicella vaccination campaigns is explored by a review of published data on the use of the vaccine. No significant difference is shown to exist between the risk of zoster caused by the vaccine and the wild virus. A mathematical model is then developed to take into consideration the influence of the prevalence of varicella on viral reactivation and the impact of vaccination with attenuated virus, which may be able to recrudesce. Under some conditions, mass application of such vaccines may have the impact of increasing zoster incidence. The results presented here indicate that, before starting any vaccination programme against varicella, its consequences need to be assessed in much more depth.

The epidemiology of varicella-zoster virus infections: a mathematical model

Herpes-zoster is caused by the reactivation of varicella-zoster virus (VZV). In this paper different hypotheses of how this re-emergence of virus comes about are reviewed and discussed. From these hypotheses, and epidemiological data describing the initial transmission of the virus, a mathematical model of primary disease (varicella) and reactivated disease (zoster) in developed countries is derived. The steady-state age distributions of zoster cases predicted by this model are compared with the observed distribution, derived from a review and analysis of published epidemiological data. The model allows differentiation between published hypotheses in which age of host may or may not influence the probability of viral reactivation. The results indicate that the probability of reactivation must increase with age to allow the observed pattern of zoster cases. The basic mathematical model presented provides a conceptual framework, which may be extended to assess possible control programmes.

Antigenic cross-reaction between a varicella-zoster virus nucleocapsid protein encoded by gene 40 and a herpes simplex virus nucleocapsid protein

Human sera from varicella-zoster virus (VZV) and herpes simplex virus type 1 (HSV-1) seropositive individuals contain antibody to a 155-kilodalton (155 kDa) viral protein. In this study, we show that monoclonal antibodies (mAb10.1 and mAb1A1.4) prepared against VZV and HSV-1 proteins, respectively, reacted with nuclear antigens and recognized a 155 kDa protein in the infected cells. Immunoprecipitation of whole virions and viral nucleocapsids with these mAbs showed that the 155 kDa protein is located in VZV and HSV-1 nucleocapsids. In addition, immunofluorescence and cross-reaction experiments revealed the antigenic cross-reactivity between the VZV and HSV-1 155 kDa nucleocapsid proteins. To map the coding region of the VZV 155 kDa protein, a truncated DNA fragment from the predicted open reading frame 40 was cloned into an in vitro transcription vector (pGEM). The RNA transcribed from the inserted DNA was translated in vitro and immunoprecipitated with mAb10.1. The reactivity of the in vitro translation products with mAb10.1 indicated that the 155 kDa nucleocapsid protein is encoded by VZV gene 40. These findings demonstrated that the VZV 155 kDa nucleocapsid protein encoded by gene 40 induces humoral response which cross-reacts with both VZV and HSV.

Varicella zoster virus deoxythymidine kinase is present in serum before the onset of varicella

A sensitive enzyme assay with 125I-iododeoxyuridine as substrate and cytidine triphosphate as phosphate donor was used for the direct detection of varicella zoster virus (VZV) deoxythymidine kinase (TK) in human serum. Sera sampled during the incubation period of varicella from 2 patients, a 42-year-old man and his 11-year-old son, have been analysed for TK activity. A simultaneous increase in cellular and VZV TK activity, starting 5 to 3 days before the onset of clinical varicella, was observed.

The risk of zoster after varicella vaccination in children with leukemia

We examined the incidence of zoster in 346 children with underlying acute lymphoblastic leukemia who were immunized with live attenuated varicella vaccine while in remission. We also compared a subset of 84 of these children with a matched group of 84 children with leukemia who had had natural infection with varicella. Of the 346 vaccinated children, 5 (1.45 percent) became infected with zoster after 10,878 months of observation, for an incidence of 0.552 case per 100 person-years. Among the matched pairs of subjects, zoster occurred in 3 (3.6 percent) of the 84 vaccinated subjects during 2936 months of observation--an incidence of 1.23 cases per 100 person-years--and in 11 (13.1 percent) of the subjects with natural infection during 4245 months--an incidence of 3.11 cases of zoster per 100 person-years. Although the incidence of zoster was more than twice as high in the control children as in the vaccinated children (3.11 vs. 1.23 cases per 100 person-years), a Kaplan-Meier product-limit analysis revealed no significant differences in incidence between the two groups. Children from both groups in whom leukemia recurred were more likely to contract zoster than those who did not have a recurrence (7 of 35 vs. 7 of 133, P less than 0.025). Zoster was not a marker for impending relapse. No case of zoster was severe or disseminated. We conclude that the incidence of zoster following immunization with live attenuated varicella vaccine is no greater than that following natural varicella infection.

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

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