Oka Strain Research Articles

Cloning of the varicella-zoster virus genome as an infectious bacterial artificial chromosome in Escherichia coli

The complete genome of the varicella-zoster virus (VZV) Oka strain has been cloned as a bacterial artificial chromosome (BAC). Following electroporation into Escherichia coli ( E. coli) strain DH10B, the VZV BAC was stably propagated over multiple generations of its host. Human embryonic lung (HEL) cells transfected with VZV BAC DNA recovered from DH10B showed cytopathic effect (CPE), and virus spread to neighbouring cells was observed. BAC vector sequences are flanked by loxP sites and, coinfection of the reconstituted virus, with a recombinant adenovirus expressing Cre recombinase removed the bacterial sequences. The resulting recombinant rV02 grew as well as the parental virus in HEL cells. The recombinant VZV will promote VZV research and increase use of the viral genome as an investigative tool.

In vitro selection of drug-resistant varicella-zoster virus (VZV) mutants (OKA strain): differences between acyclovir and penciclovir?

Varicella-zoster virus (VZV) mutants were isolated under the pressure of different classes of antiviral compounds: (i) drugs that depend on the viral thymidine kinase (TK) for their activation, i.e. acyclovir (ACV), brivudin (BVDU), penciclovir (PCV) and sorivudine (BVaraU); (ii) drugs that are independent of the viral TK for their activation, i.e. 2-phosphonylmethoxyethyl (PME) derivatives of adenine (PMEA, adefovir) and 2,6-diaminopurine (PMEDAP); and (iii) drugs that do not require any metabolism to inhibit the viral DNA polymerase, i.e. foscarnet (PFA). Drug-resistant virus strains were obtained by serial passage of the OKA strain in human embryonic lung (HEL) fibroblasts and the different drug-resistant mutants were subsequently evaluated for their in vitro susceptibility to a broad range of antiviral drugs. Virus strains emerging under the pressure of ACV, BVDU and BVaraU were cross-resistant to all drugs that depend on the viral TK for activation, but remained susceptible to the acyclic nucleoside phosphonates (i.e. PMEA, PMEDAP and the 3-hydroxy-2-phosphonylmethoxypropyl derivatives of adenine (HPMPA) and cytosine (HPMPC, cidofovir)) and PFA. In contrast, the virus strains selected under pressure of PCV were resistant to PCV, ACV, PMEA and PFA; but not BVDU, BVaraU, GCV, HPMPC or HPMPA. Similar patterns of drug susceptibility were noted for the virus strains selected under the pressure of PMEA or PFA, pointing to an alteration in the viral DNA polymerase as basis for the resistant phenotype selected by PCV, as well as PMEA and PFA. In contrast, the resistant phenotype selected by ACV as well as BVDU and BVaraU may be attributed primarily to mutations in the viral TK gene. Our data thus indicate that ACV and PCV select in vitro for different drug-resistant VZV phenotypes; whether this is also the situation in vivo remains to be investigated.

Live varicella vaccine polarizes the mucosal adjuvant action of cholera toxin or its B subunit on specific Th1-type helper T cells with a single nasal coadministration in mice.

This study was undertaken to determine whether the specific Th1- or Th2-cell response to varicella-zoster virus was induced predominantly by a mucosal adjuvant, cholera toxin, in mice. A commercially available live varicella vaccine (Oka strain) and cholera toxin or its B subunit were administered simultaneously via the nasal route. Delayed-type hypersensitivity to the Oka vaccine was induced, but the systemic neutralizing antibody response was low. The delayed-type hypersensitivity evoked after a single administration was relatively higher than that on administration three times. When spleen cells from mice immunized once with the vaccine and cholera toxin or its B subunit were restimulated with the live vaccine in vitro, there was greater thymidine uptake and production of interleukin- 2 (IL-2) than controls, but only a low level of IL-4 production. The production of IL-2 induced by the B subunit of cholera toxin was less than that by cholera toxin and a mutant of Escherichia coli enterotoxin on co-immunization with the vaccine in mice. Cholera toxin and its B subunit have been reported to induce predominantly a specific Th2-type T-cell response to various antigens. However, the Oka vaccine is an antigen that polarizes the activation of specific Th1/Th2-type T cells by cholera toxin or its B subunit to the Th1-type side. Cholera toxin and its B subunit are thus useful mucosal adjuvants for inducing cellular immunity to the Oka vaccine similar to Escherichia coli enterotoxin.

Herpes zoster virus sclerokeratitis and anterior uveitis in a child following varicella vaccination

PurposeTo report a case of herpes zoster virus sclerokeratitis with anterior uveitis following vaccination with live attenuated varicella vaccine (Oka strain). DesignCase report. MethodsThe case records of the patient were reviewed retrospectively. Pertinent literature citations were identified using MEDLINE. ResultsA 9-year-old boy presented with herpes zoster ophthalmicus 3 years following vaccination with live attenuated varicella vaccine (Oka strain). Examination of the affected eye revealed a moderate follicular response on the palpebral conjunctiva, decreased corneal sensation, mildly elevated intraocular pressure, diffuse anterior scleritis with marginal keratitis, and a moderately severe anterior uveitis. Amplified DNA from fluid taken from the base of a cutaneous vesicle produced wild-type varicella zoster virus (VZV) DNA, not Oka strain. ConclusionsHerpes zoster virus infection needs to be considered in all patients who present with scleritis, keratitis, or anterior uveitis, regardless of their varicella vaccination status.

Microarray analysis of host cell gene transcription in response to varicella-zoster virus infection of human T cells and fibroblasts in vitro and SCIDhu skin xenografts in vivo.

During primary infection, varicella-zoster virus (VZV) is spread via lymphocytes to skin, where it induces a rash and establishes latency in sensory ganglia. A live, attenuated varicella vaccine (vOka) was generated by using the VZV Oka strain (pOka), but the molecular basis for vOka attenuation remains unknown. Little is known concerning the effects of wild-type or attenuated VZV on cellular gene regulation in the host cells that are critical for pathogenesis. In this study, transcriptional profiles of primary human T cells and fibroblasts infected with VZV in cell culture were determined by using 40,000-spot human cDNA microarrays. Cellular gene transcription in human skin xenografts in SCID mice that were infected with VZV in vivo was also evaluated. The profiles of cellular gene transcripts that were induced or inhibited in infected human foreskin fibroblasts (HFFs), T cells, and skin in response to pOka and vOka infection were similar. However, significant alterations in cellular gene regulation were observed among the three differentiated human cell types that were examined, suggesting specific differences in the biological consequences of VZV infection related to the target cell. Changes in cellular gene transcription detected by microarray analysis were confirmed for selected genes by quantitative real-time reverse transcription-PCR analysis of VZV-infected cells. Interestingly, the transcription of caspase 8 was found to be decreased in infected T cells but not in HFFs or skin, which may signify a tissue-specific antiapoptosis mechanism. The use of microarrays to demonstrate differences in effects on host cell genes in primary, biologically relevant cell types provides background information for experiments to link these various response phenotypes with mechanisms of VZV pathogenesis that are important for the natural course of human infection.

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.

Varicella-zoster virus isolates, but not the vaccine strain OKA, induce sensitivity to alpha-1 and beta-1 adrenergic stimulation of sensory neurones in culture.

The reactivation of varicella-zoster virus (VZV) from its persistent state in sensory neurones causes shingles and induces severe, long-lasting pain and hyperalgesia that often lead to postherpetic neuralgia. To investigate the VZV-induced neuropathic changes, we established conditions for the active infection of sensory neurones from rat dorsal root ganglia in vitro. After 2 days of culture, up to 50% of the cells expressed viral antigens of the immediate-early and late replication phase. The intracellular calcium ion concentration was monitored in individual cells by microfluorimetry. Whereas the calcium response to capsaicin was preserved, the VZV-infected neurones gained an unusual sensitivity to noradrenaline stimulation in contrast to non-infected cells. The adrenergic agonists phenylephrine and isoproterenol had a similar efficacy demonstrating that both alpha(1)- and beta(1)-adrenoreceptors were involved. The sensitivity to adrenergic stimulation was observed after infection with different wildtype isolates, but not with the attenuated vaccine strain OKA. The lack of noradrenaline sensitivity of vaccine-infected neurones demands a structural comparison of wildtype and vaccine viruses with and without phenotype. A partial sequence evaluation (26 kb) of the European OKA vaccine strain surprisingly revealed a series of nucleotide exchanges in comparison to presumably identical OKA strains from other sources, although VZV is generally considered genetically stable. In summary, we report that the infection with wildtype VZV isolates, but not with the vaccine strain, induces noradrenaline sensitivity in sensory neurones, which correlates with clinical and experimental observations of adrenergic effects involved in VZV-induced neuralgia.

An intradermal skin test for determination of immunity to varicella

AIMSTo evaluate the usefulness of a diluted, inactivated solution of attenuated varicella vaccine in predicting susceptibility to varicella and its correlation with specific antibody titre to varicella.METHODSIn a prospective blinded...

Long-term persistence of cellular immunity to Oka vaccine virus induced by pernasal co-administration with Escherichia coli enterotoxin in mice

A mutant of Escherichia coli enterotoxin induced cellular immunity to a live varicella vaccine (the Oka strain) as a mucosal adjuvant in mice. The persistence of this cellular immunity was investigated. A commercially available live Oka vaccine virus and toxin were administered once simultaneously via the nasal route, in mice. Ten or 12 months later, a delayed-type hypersensitivity to the vaccine virus was detected by footpad test, but an antibody neutralizing the varicella-zoster virus was not. When spleen cells from mice immunized with the vaccine and toxin were re-stimulated by live vaccine in vitro, their thymidine uptake and IL-2 production were higher than those from mice immunized with the vaccine alone, but lower than those of spleen cells prepared from mice 2 months after nasal administration. Production of IL-4 in these cells, however, was not induced by re-stimulation in vitro. These results suggest that although humoral immunity for Oka vaccine virus is only weakly induced by one co-administration of the vaccine and toxin, cellular immunity is induced and maintained over 1 year, though it declines with age. The nasal administration of the vaccine and toxin might be effective for maintaining cellular immunity to the varicella-zoster virus long term.

Infection by human varicella-zoster virus confers norepinephrine sensitivity to sensory neurons from rat dorsal root ganglia.

Varicella-zoster virus (VZV) is a widespread human herpes virus causing chicken pox on primary infection and persisting in sensory neurons. Reactivation causes shingles, which are characterized by severe pain and often lead to postherpetic neuralgia. To elucidate the mechanisms of VZV-associated hyperalgesia, we elaborated an in vitro model for the VZV infection of sensory neurons from rat dorsal root ganglia. Between 35 and 50% of the neurons showed strong expression of the immediate-early virus antigens IE62 and IE63 and the late glycoprotein gE. When the intracellular calcium concentration was monitored microfluorometrically for individual cells after infection, the sensitivity to GABA or capsaicin was similar in controls and in VZV-infected neurons. However, the baseline calcium concentration was increased. Neurons became de novo sensitive to adrenergic stimulation after VZV infection. Norepinephrine-responsive neurons were more frequent and calcium responses to norepinephrine were significantly higher after infection with wild-type isolates than with the attenuated vaccine strain OKA. The adrenergic agonists phenylephrine and isoproterenol had similar efficacy. We suggest that the infection with wild-type VZV isolates confers norepinephrine sensitivity to sensory neurons by using alpha(1)- and/or beta(1)-adrenergic receptors providing a model for the pathophysiology of the severe pain associated with the acute reactivation of VZV.

Evidence for frequent reactivation of the Oka varicella vaccine strain in healthy vaccinees.

Serum antibody levels and infection rates were followed for 4 years in 4,631 children immunized with the recently licensed Oka strain varicella vaccine. Anti-VZV titers declined over time in high-responder subjects, but rose in vaccinees with low titers. Among subjects with low anti-VZV titers, the frequency of clinical sequelae and immunological boosting significantly exceeded the 13%/yr rate of exposure to wild type varicella. These findings indicate that the Oka strain of VZV persisted in vivo, and reactivated as serum antibody titers declined after vaccination. This mechanism may improve vaccine-associated long-term immunity.

25 years' experience with the Biken Oka strain varicella vaccine: a clinical overview.

Although commonly considered a benign disease in childhood, varicella is a potentially serious infection not only in high risk groups such as children with immune deficiencies, but also in otherwise healthy adults and children. Complications include bacterial superinfections, pneumonia and encephalitis, and the infection can be fatal. In addition to the substantial burden of clinical disease, varicella presents a large economic burden to society. In the absence of a satisfactory treatment for varicella infection, vaccination has an important role in preventing the disease and its sequelae. The original Oka strain live attenuated varicella vaccine was developed in 1974 at the Biken Institute in Japan. Since its development more than 25 years ago, the Biken varicella vaccine has been studied in a large number of clinical trials. The wealth of clinical experience obtained with this vaccine serves to confirm its tolerability, immunogenicity and efficacy in both healthy and high risk individuals. Vaccination has been shown to prevent clinical infection and provide effective protection against the severe complications of varicella. This historical review summarises the long clinical experience with the Biken varicella vaccine and confirms that the vaccine is very well tolerated and provides long term immunity from varicella infection.

Adjuvant action of Escherichia coli enterotoxin for delayed-type hypersensitivity to Oka vaccine virus on pernasal co-administration in mice

The usefulness of a mutant of Escherichia coli enterotoxin for the induction of cellular immunity to varicella-zoster virus as a mucosal adjuvant is assessed in mice. When a commercially available live varicella vaccine (the Oka strain) and toxin were once administered simultaneously via the nasal route, delayed-type hypersensitivity to Oka vaccine virus was significantly induced and detected by footpad test in mice. Moreover, when spleen cells from mice immunized with the vaccine and toxin were re-stimulated with live vaccine in vitro, they showed more thymidine uptake and produced more IL-2 than those from mice immunized with the vaccine alone. These results suggest that mutant enterotoxin has adjuvant action to induce a specific delayed-type hypersensitivity to Oka vaccine virus on nasal co-administration with live vaccine virus.

Varicella Vaccination in Children

Varicella vaccines have been developed, studied, tested and used since the early 1970s, first in Japan and subsequently in Europe, the US, Asia and South and Central America. Varicella vaccination was first used to immunise Japanese children in cancer remission, as wild-type varicella disease is often fatal in immunocompromised individuals. Since then, it has been licensed for use in healthy children as well. There are 3 manufacturers of the vaccine: Biken (Japan), Merck and Co. (US) and SmithKline Beecham (Belgium). The Biken vaccine has been approved for use in Japan since 1986 (although it was developed and used for research purposes from 1974). The Merck and Co. vaccine was approved in the US in March 1995 and the SmithKline Beecham vaccine was first licensed for use in immunocompromised children in 1984 and for healthy children in Sweden in October 1994. All 3 vaccines are derived from the Oka (Japanese) strain obtained from an immunologically normal 3-year-old Japanese boy named Oka with wild-type disease. Aventis-Pasteur has also purchased the rights to the Oka strain but no published literature is available for review. Use of the varicella vaccine has been controversial because many argue that: (i) the disease is mild and not worth preventing; (ii) the long term immunity provided by the vaccine is unknown; and (iii) the average age of those with the disease will increase if the vaccine is used and hence there will be more complications in older patients and, therefore, more costs. Because of some outbreaks of secondary bacterial infections after varicella in children in US day care centres, vaccination of healthy children is required in some states. It will be interesting to see whether other countries adopt a similar recommendation as more families have 2 working parents. The financial benefit of the vaccine (keeping parents at work) may encourage more use of the vaccine and a subsequent recommendation for immunisation schedules.

148 Phenotypic and genotypic characterization of antiviral drug-resistant cytomegalovirus in transplant recipients : N. Lurain 1, K. Kapell 1, D. Kohn 2, E. Robert 1, B. Yen-Lieberman 2, K. Pursell 3, E. Garrity 4, M. Arens 5, S. Bhorade 4, J. Bremer 1, V. Yeldandi 4. 1Rush Medical College, Chicago, IL, 2Cleveland Clinic, Cleveland, OH, 3Univ. of Illinois Chicago Medical

Varicella-zoster virus (VZV) mutants were isolated under the pressure of different classes of antiviral compounds: (i) drugs that depend on the viral thymidine kinase (TK) for their activation, i.e. acyclovir (ACV), brivudin (BVDU), penciclovir (PCV) and sorivudine (BVaraU); (ii) drugs that are independent of the viral TK for their activation, i.e. 2-phosphonylmethoxyethyl (PME) derivatives of adenine (PMEA, adefovir) and 2,6-diaminopurine (PMEDAP); and (iii) drugs that do not require any metabolism to inhibit the viral DNA polymerase, i.e. foscarnet (PFA). Drug-resistant virus strains were obtained by serial passage of the OKA strain in human embryonic lung (HEL) fibroblasts and the different drug-resistant mutants were subsequently evaluated for their in vitro susceptibility to a broad range of antiviral drugs. Virus strains emerging under the pressure of ACV, BVDU and BVaraU were cross-resistant to all drugs that depend on the viral TK for activation, but remained susceptible to the acyclic nucleoside phosphonates (i.e. PMEA, PMEDAP and the 3-hydroxy-2-phosphonylmethoxypropyl derivatives of adenine (HPMPA) and cytosine (HPMPC, cidofovir)) and PFA. In contrast, the virus strains selected under pressure of PCV were resistant to PCV, ACV, PMEA and PFA; but not BVDU, BVaraU, GCV, HPMPC or HPMPA. Similar patterns of drug susceptibility were noted for the virus strains selected under the pressure of PMEA or PFA, pointing to an alteration in the viral DNA polymerase as basis for the resistant phenotype selected by PCV, as well as PMEA and PFA. In contrast, the resistant phenotype selected by ACV as well as BVDU and BVaraU may be attributed primarily to mutations in the viral TK gene. Our data thus indicate that ACV and PCV select in vitro for different drug-resistant VZV phenotypes; whether this is also the situation in vivo remains to be investigated.

146 Characterization of drug resistance-associated mutations in the human cytomegalovirus DNA polymerase : Mehrdad Mousavi-Jazi, Annika Linde, Britta Wahren, and Maria Brytting. Swedish Institute for Infectious Disease Control, and MTC, Karolinska Institute, SE-171 82 Solna, Sweden

Varicella-zoster virus (VZV) mutants were isolated under the pressure of different classes of antiviral compounds: (i) drugs that depend on the viral thymidine kinase (TK) for their activation, i.e. acyclovir (ACV), brivudin (BVDU), penciclovir (PCV) and sorivudine (BVaraU); (ii) drugs that are independent of the viral TK for their activation, i.e. 2-phosphonylmethoxyethyl (PME) derivatives of adenine (PMEA, adefovir) and 2,6-diaminopurine (PMEDAP); and (iii) drugs that do not require any metabolism to inhibit the viral DNA polymerase, i.e. foscarnet (PFA). Drug-resistant virus strains were obtained by serial passage of the OKA strain in human embryonic lung (HEL) fibroblasts and the different drug-resistant mutants were subsequently evaluated for their in vitro susceptibility to a broad range of antiviral drugs. Virus strains emerging under the pressure of ACV, BVDU and BVaraU were cross-resistant to all drugs that depend on the viral TK for activation, but remained susceptible to the acyclic nucleoside phosphonates (i.e. PMEA, PMEDAP and the 3-hydroxy-2-phosphonylmethoxypropyl derivatives of adenine (HPMPA) and cytosine (HPMPC, cidofovir)) and PFA. In contrast, the virus strains selected under pressure of PCV were resistant to PCV, ACV, PMEA and PFA; but not BVDU, BVaraU, GCV, HPMPC or HPMPA. Similar patterns of drug susceptibility were noted for the virus strains selected under the pressure of PMEA or PFA, pointing to an alteration in the viral DNA polymerase as basis for the resistant phenotype selected by PCV, as well as PMEA and PFA. In contrast, the resistant phenotype selected by ACV as well as BVDU and BVaraU may be attributed primarily to mutations in the viral TK gene. Our data thus indicate that ACV and PCV select in vitro for different drug-resistant VZV phenotypes; whether this is also the situation in vivo remains to be investigated.

Varicella vaccination: evidence for frequent reactivation of the vaccine strain in healthy children.

Wild-type varicella zoster virus (VZV) causes chickenpox, a common childhood illness characterized by fever and a vesicular rash and rare serious complications. Wild-type VZV persists in a latent form in the sensory ganglia, and can re-activate to cause herpes zoster. More than 10 million American children have received the live attenuated Oka strain VZV vaccine (OkaVZV) since its licensure in 1995. Pre-licensure clinical studies showed that mean serum anti-VZV levels among vaccinees continued to increase with time after vaccination. This was attributed to immunologic boosting caused by exposure to wild-type VZV in the community. Here, we examine the alternative, that large-scale asymptomatic reactivation of OkaVZV might occur in vaccinees. We analyzed serum antibody levels and infection rates for 4 years of follow-up in 4,631 children immunized with OkaVZV. Anti-VZV titers decreased over time in high-responder subjects, but rose in vaccinees with low titers. Among subjects with low anti-VZV titers, the frequency of clinical infection and immunological boosting substantially exceeded the 13%-per-year rate of exposure to wild-type varicella. These findings indicate that OkaVZV persisted in vivo and reactivated as serum antibody titers decreased after vaccination. This has salient consequences for individuals immunized with OkaVZV.

Experience with live attenuated varicella vaccine (Oka strain) in healthy Japanese subjects; 10-year survey at pediatric clinic

Live attenuated varicella vaccine (Oka strain, Biken Institute, Osaka, Japan) was administered to 973 healthy individuals over a 10-year period (1987–1997) at the pediatric clinic of Showa Hospital in Japan. We evaluated the relevant serological and clinical data, which were collected by questionnaire. Seroconversion by the immune adherence hemagglutination method was documented in 94% (805/860) of the initially seronegative subjects. Of the initially seropositive subjects, 56% (63/113) showed enhancement of antibody after vaccination. Reactions to the vaccine were generally insignificant, except for a rash at the injection site, seen in the first 3 days post-administration in 17% (41/241) of the recently vaccinated subjects. In March 1998, we conducted a survey of 559 of the initially seronegative subjects who had received the vaccine 0.6–10.8 (mean 5.4) years earlier. Of these subjects, 21% (119/559) contracted breakthrough varicella. However, their symptoms were milder than those caused by natural varicella seen in unvaccinated children. Seroconversion was demonstrated in 92% (109/119) of these cases. The incidence of breakthrough disease decreased with a rise in postvaccination antibody titer to ≧32. Four of the subjects (0.7% of 559) developed herpes zoster following vaccination, two of whom had earlier exhibited breakthrough varicella. Lesions in one case of zoster, without breakthrough varicella, appeared on the cervical dermatome at the injection site. The vaccine was safe and effective. However, there was a relatively high incidence of rash at the injection site with certain lot numbers used in recent years which warrants investigation.

Humoral immunoresponse to varicella-zoster virus pernasally coadministered with Escherichia coli enterotoxin in mice

It is evaluated whether Escherichia coli enterotoxin is useful for induction of immunity to varicella-zoster virus (VZV) as a mucosal adjuvant in mice. When a commercially available live varicella vaccine (Oka strain) and toxin were administered simultaneously via a nasal route three times at 2 or 6 month intervals, an antibody neutralizing VZV was detected in half or all of the mice vaccinated, respectively. The antibody specific to the vaccine strain of VZV reacted to five proteins, molecular weights of which were 110 K, 100 K, 62 K, 54 K and 46 K. These proteins were composed of glycosylated products of all kinds of glycoproteins. These results suggest that although a nasal administration of the vaccine without the adjuvant has little immunogenicity in mice, the simultaneous administration of the live vaccine and the toxin over a long period induces a specific humoral immunity to VZV.

Vaccination of immunocompetent elderly subjects with a live attenuated Oka strain of varicella zoster virus: a randomized, controlled, dose-response trial

After primary infection in childhood, varicella zoster virus (VZV) remains latent in the dorsal route ganglia. Its reactivation later in life can lead to a zoster episode. VZV-specific, T-cell-mediated immunity (VZV-CMI) is likely to be important in preventing symptomatic reactivation. As CMI declines with age, a vaccine enhancing VZV-CMI might be effective in decreasing the incidence or severity of zoster in elderly subjects. A randomized, double blind controlled trial assessing CMI responses of elderly subjects immunized with a live attenuated, VZV-Oka vaccine was conducted. Two hundred healthy volunteers (55–75 years of age) received either a single injection of the VZV vaccine (PMC), containing 3200 (Oka 3200), 8500 (Oka 8500), or 41,650 (Oka 41650) PFU of live VZV, or a pneumococcus vaccine control group (Pneumo 23(®). The immune response to VZV was assessed by measuring the T-cell response to VZV antigens, i.e. proliferation (stimulation index, SI), precursor cell frequency (PCF), cytokine secretion, and antibody titers. Six weeks post-vaccination, VZV-specific SI (adjusted mean values) was significantly greater ( P<0.0001) in the 3 vaccine groups (with SI=5.6 for Oka 3200; SI=5.0 for Oka 8500, and SI=7.2 for Oka 41,650) than in the control group (SI=2.9). The increase in PCF was striking, with 72.4, 91.2 and 85.1 precursors per million cells respectively in these 3 vaccine groups, vs 26.3 in the control group. No significant IL-4 secretion was observed in any subject, whereas the presence of IFN- γ secretion was found to correlate with good responder status. The increase of these CMI parameters did not depend upon the titer of virus injected. Geometric mean titers of VZV antibodies increased in all vaccine groups and remained unchanged in the control group. Nevertheless, no correlation between the antibody response and the cell-mediated response was found. Live attenuated VZV vaccine caused a significant increase in VZV-CMI in a healthy, elderly population. No relationship between vaccine dose and the intensity of the specific response was found.