Antibody-dependent cell-mediated cytotoxicity against varicella-zoster virus-infected targets

Alphaherpesvirus Vaccines

Prophylactic and therapeutic vaccines for the alphaherpesviruses including varicella zoster virus (VZV) and herpes simplex virus types 1 and 2 have been the focus of enormous preclinical and clinical research. A live viral vaccine for prevention of chickenpox and a subunit therapeutic vaccine to prevent zoster are highly successful. In contrast, progress towards the development of effective prophylactic or therapeutic vaccines against HSV-1 and HSV-2 has met with limited success. This review provides an overview of the successes and failures, the different types of immune responses elicited by various vaccine modalities, and the need to reconsider the preclinical models and immune correlates of protection against HSV.

Safety and Varicella Outcomes in In Utero-Exposed Newborns and Preterm Infants Treated With Varicella Zoster Immune Globulin (VARIZIG): A Subgroup Analysis of an Expanded-Access Program

BACKGROUND

Infants exposed to varicella zoster virus (VZV) in utero ≤5 days before or ≤48 hours after delivery and preterm infants are at high risk for varicella complications. An expanded-access program assessed varicella outcomes after administration of varicella zoster immune globulin (human) (VARIZIG) in a real-world setting.

METHODS

In this open-label, expanded-access program, high-risk infants received ≤125 IU/10 kg of VARIZIG (NCT00338442). VZV outcomes and safety were assessed.

RESULTS

There were 43 newborns exposed to VZV in utero and 80 preterm infants exposed to VZV; >80% received VARIZIG within 96 hours of reported exposure. When varicella outcomes were available, varicella occurred in 7 of 38 (18%) in utero-exposed newborns and zero of 65 preterm infants. Varicella-related complications were reported in 3 in utero-exposed newborns (3 with >100 lesions, 1 each with encephalitis and pneumonia). Adverse events were reported for 16% of in utero-exposed newborns and 25% of preterm infants, but few were considered related to VARIZIG. There were no deaths attributable to varicella or VARIZIG.

CONCLUSIONS

Varicella incidence and morbidity were low in in utero-exposed infants and zero in preterm infants who received prophylactic VARIZIG. There were few VARIZIG-related safety concerns.

Development of adjuvanted recombinant zoster vaccine and its implications for shingles prevention

INTRODUCTION

GSK has developed a two-dose adjuvanted recombinant zoster vaccine (Shingrix, RZV) to protect people aged ≥50 years (50+) against herpes zoster (HZ) and its complications. RZV showed >90% efficacy against HZ, sustained over 4 years of follow-up, in all studied age groups.

AREAS COVERED

This article reviews the scientific rationale underlying the design of RZV; the clinical evidence demonstrating immunogenicity, safety, and efficacy in persons 50+; and the public health implications and cost-effectiveness.

EXPERT COMMENTARY

A decline in varicella zoster virus (VZV) immunity is associated with increased risk of HZ in adults 50+ and immunocompromised individuals. RZV was designed to restore levels of anti-VZV cellular and humoral immunity to prevent VZV reactivation. RZV includes the recombinant gE glycoprotein antigen, and Adjuvant System AS01_B which promotes cellular and antibody responses. In two Phase III studies in subjects aged 50+ and 70+ years, RZV efficacy against HZ compared to placebo was >90% and ≥89% against post-herpetic neuralgia (PHN). RZV is expected to dramatically impact HZ morbidity including its complications, and associated health-care costs. In the US population aged 50+ years, vaccination with RZV can be cost-effective compared to no vaccination and cost-saving compared to the currently available live-attenuated HZ vaccine (Zostavax, Merck).

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.

Varicella zoster virus-specific cytotoxicity following secondary immunization with live or killed vaccine

Subjects > or = 55 years of age were immunized with attenuated varicella zoster virus (VZV) vaccine (live) or with the same vaccine, which had been heated to 56 degrees C for 7 days (killed). The ability of subjects' blood lymphocytes to lyse target cells infected with VZV was determined before and 3 months after immunization using autologous Epstein-Barr virus (EBV) lymphoblasts as targets for human leukocyte antigen (HLA) class I restricted cytotoxicity and human fibroblasts as targets for unrestricted (natural killer [NK]) cytotoxicity. The live vaccine recipients showed an increase in their class I-restricted lysis of targets compared with the recipients of the killed vaccine. The two populations showed equivalent increase in their NK-dependent lysis of fibroblast targets. The results support the view that both the live and killed vaccines stimulate cytotoxicity by VZV-specific lymphocytes but that the live vaccine stimulates relatively more class I-restricted killing.

Inhibition of varicella-zoster virus glycoprotein expression by peripheral blood mononuclear cells

The effect of peripheral blood mononuclear cells (PBMC) on expression of varicella-zoster virus (VZV) glycoproteins (Gps) was analyzed by flow cytometry. PBMC from VZV seropositive and seronegative donors and supernatant of PBMC co-cultured with VZV-infected human embryonic fibroblasts reduced VZV Gp expression. Neutralization of supernatant fluid with mixture of anti-interferons (IFN)-alpha, -beta, -gamma, and tumor necrosis factor (TNF)-alpha partially reduced inhibitory activity of supernatant on VZV Gp expression. Deletion of natural killer (NK) cells and adherent cells from PBMC reduced inhibitory activity of PBMC on VZV Gp expression. These results suggest that IFN-alpha, -beta, -gamma, TNF-alpha and other soluble factors released from NK cells and monocytes by co-cultivation with VZV-infected fibroblasts inhibit VZV Gp expression.

Cytotoxicity against varicella zoster virus infected targets in children with acute leukemia

To eliminate the role of natural killer (NK), antibody-dependent cell-mediated cytotoxicity (ADCC), and polymorphonuclear leukocyte (PMN)-mediated cytotoxicity in Varicella zoster virus (VZV) infections, peripheral blood mononuclear cell (PBMC)-mediated NK and ADCC, and phorbol myristate acetate-stimulated PMN-mediated cytotoxicity against VZV-infected targets were studied in children with leukemia. Natural killer and PMN-mediated cytotoxic activity was depressed for 6 months after complete remission and ADCC activity was depressed for 1 year after complete remission. The magnitude of three cytotoxic mechanisms in leukemic children gradually increased while they continued in complete remission. These results suggested that decreased cytotoxic activities of PBMC and PMN might contribute to serious VZV infections and susceptibility to herpes zoster in leukemic children.

Cytotoxicity and cytoadherence of human and murine polymorphonuclear leukocytes against Junin virus infected targets in the absence of anti-viral antibody and complement

Human and murine polymorphonuclear leukocytes (PMN) lysed L cells infected with Junin Virus (JV) in an in vitro system free of antiviral antibody and complement. Infected VERO cells proved to be resistant to the cytolytic effect. Murine PMN showed an increased adherence on JV-infected L cells but did not attach to VERO cells. The opposite was observed with human PMN, which did adhere to infected VERO cells but not to infected L cells. These results indicate that PMN activity may be an early mechanism of defense in JV infection by lysing virus-infected cells when no immune response has been established, and that cytoadherence is not a necessary step for target lysis.

Antibody response determined with antibody-dependent cell-mediated cytotoxicity (ADCC), neutralizing antibody, and varicella skin test in children with natural varicella and after varicella immunization

Humoral and cellular immune responses were examined in 115 children with varicella and in 21 children who had been immunized with live varicella vaccine. Antibody determined with antibody-dependent cell-mediated cytotoxicity (ADCC) was detected earlier than neutralizing antibody (NT) in both groups. While humoral and cellular immunity were detected simultaneously in the natural varicella group, cellular immunity was detected earlier than humoral immunity in the immunized group. This suggests that ADCC, rather than NT, is involved in the early stages of recovery from varicella-zoster virus (VZV) infection.

Natural killing of varicella-zoster virus (VZV)-infected fibroblasts in normal children, children with VZV infections, and children with Hodgkin's disease

We studied mononuclear cell (MNC)-mediated natural killing (NK) of varicella-zoster virus (VZV)-infected fibroblasts in normal children, children with VZV infections, and children with Hodgkin's disease. NK activity was tested in 18 hr 51Cr release assays. NK activity for adults was significantly higher than that for children 1-3 years old or 4-6 years old (p less than 0.05). Serological status did not affect NK activity. NK activity in normal children was not increased 4-6 weeks after immunization with varicella vaccine. Seven normal children with natural varicella showed significantly higher NK activity against VZV-infected and uninfected targets. Eight immunosuppressed children with herpes zoster showed significantly reduced NK activity within 72 hours of the onset of herpes zoster. However, their NK activity rose to the normal level one to two weeks later. Children with Hodgkin's disease had low NK activity. These results suggested that NK cells might play an initial defensive role in VZV infections, and that low NK activity in immunocompromised hosts might contribute to their high incidence of herpes zoster.

Inhibition of varicella-zoster virus in vitro by human peripheral blood mononuclear cells

A functional in vitro assay of cell-mediated immunity to varicella-zoster virus (VZV) is described. This procedure uses an enzyme-linked immunosorbent assay (ELISA) to measure the inhibitory effect of human peripheral blood mononuclear cells on VZV antigen production by VZV-infected cell monolayers. When mononuclear cells from VZV-immune, tetanus-immune donors were stimulated with either VZV antigen or tetanus toxoid they reduced VZV antigen production. In contrast, mononuclear cells from VZV-nonimmune, tetanus-immune donors reduced VZV antigen only when stimulated with tetanus toxoid, but not when stimulated with VZV antigen. Cell-free supernatants recovered from the VZV inhibition assays contained the anti-VZV activity. The magnitude of the anti-VZV activity of the supernatants equalled the inhibition observed when the stimulated mononuclear cells were added to the VZV-infected monolayers. Treatment of either mononuclear cells or supernatants with anti-interferon gamma antibody indicated that their VZV inhibitory capability was largely due to the production of interferon gamma by stimulated mononuclear cells.

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.

Interleukin 2 enhances natural killing of varicella-zoster virus-infected targets

Preincubation of peripheral blood non-adherent mononuclear cells with purified or recombinant interleukin 2 (IL-2) significantly enhanced natural killer (NK) activity against uninfected and varicella-zoster virus (VZV)-infected targets, while antibody-dependent cellular cytotoxicity (ADCC) against VZV-infected targets was not increased. Preincubation of effector cells with IL-2 had no effect on conjugate formation, but lysis of both targets was increased in single cell assays. IL-2-enhanced NK against VZV-infected targets was independent of gamma-interferon (gamma-IFN) production.

Human lymphocyte, monocyte and polymorphonuclear leucocyte mediated antibody-dependent cellular cytotoxicity against varicella-zoster virus-infected targets

The ability of lymphocytes, monocytes and polymorphonuclear leucocytes (PMN) to mediate antibody-dependent cellular cytotoxicity (ADCC) against varicella-zoster virus (VZV) infected fibroblasts was tested in 51Cr release and single-cell assays. Lymphocytes had the greatest lytic activity, monocytes were intermediate in activity and PMN were the least active. Lymphocyte-mediated ADCC was complete by as early as 4 h, while maximal monocyte and PMN-mediated ADCC required 18 h. In single-cell assays, monocytes formed conjugates with both uninfected and VZV-infected targets, but did not cause lysis. PMN failed to bind or lyse either target. Few lymphocytes formed conjugates with uninfected targets, while a higher percentage bound to VZV-infected targets and caused lysis. In the presence of human antibodies to VZV conjugate formation and lysis of VZV-infected targets was significantly increased with each of the effector-cell populations. Lymphocytes had the highest lytic activity in single-cell assays as well as in 51Cr release assays, and were responsible for most of the ADCC detected in adult peripheral blood against VZV-infected targets.

Human leukocytes kill varicella-zoster virus-infected fibroblasts in the presence of murine monoclonal antibodies to virus-specific glycoproteins

Seven murine monoclonal antibodies reacting with major glycoproteins of varicella-zoster virus were tested for functional activity in assays for antibody-dependent cellular cytotoxicity (ADCC) and antibody-plus-complement-mediated lysis. Human peripheral blood mononuclear cells killed varicella-zoster virus-infected fibroblasts in the presence of three of four monoclonal antibodies directed against gp98/62 and a single monoclonal antibody directed against gp118. Neither of two monoclonal antibodies directed against gp66 was able to mediate ADCC. In 18-h assays, adherent effector cells were more active than nonadherent effector cells in mediating ADCC. Adherent cells treated with anti-Leu-11b and complement retained their cytotoxic activity, suggesting that monocytes are responsible for most of the adherent-cell-mediated cytotoxicity. Both immunoglobulin G1 and G2a murine monoclonal antibodies were able to participate in ADCC. Of the two immunoglobulin G2a monoclonal antibodies tested, both of which reacted with gp98/62, only one mediated lysis in the presence of complement. These results indicate that some murine monoclonal antibodies against major glycoproteins of varicella-zoster virus have functional activity in cytotoxicity assays.

Antibody-dependent cell-mediated cytotoxicity against IBR-infected bovine kidney cells by ruminant neutrophils: the role of lysosomal cationic protein

Antibody-dependent cell-mediated cytotoxicity (ADCC) of infectious bovine rhinotracheitis (IBR)-infected bovine kidney cells (MDBK) by neutrophils was demonstrated. Neutrophils from bovine and sheep mammary exudate and peripheral blood, and also from human peripheral blood, were all active in the presence of anti-IBR antibody. The component of the ruminant neutrophil granules which was responsible for cytotoxicity appeared to be cationic protein since purified cationic protein lysed the virus-infected cells and heparin inhibited cytotoxicity. Human neutrophil cytotoxicity to herpes simplex virus (HSV)-infected human Chang liver cells was also inhibited by heparin. Human neutrophil cytotoxicity to IBR-infected bovine kidney cells did not appear to be mediated by cationic protein since it was inhibited by the chelators of oxidative intermediates DMSO, thiourea, tryptophane, benzoate and mannitol, and not by heparin.

Human polymorphonuclear leukocyte-mediated cytotoxicity against varicella-zoster virus-infected fibroblasts

Polymorphonuclear leukocytes (PMN) were studied for their ability to mediate cytotoxicity against varicella-zoster virus (VZV)-infected and uninfected human fibroblasts in 51Cr release assays. PMN were capable of mediating antibody-dependent cellular cytotoxicity (ADCC) against VZV-infected targets. Maximal ADCC was obtained with effector-to-target ratios of 100:1 and 18 h of incubation. Percent 51Cr release for 26 normal adults was 14.1 +/- 0.6 (mean +/- standard error) in the presence of pooled human seropositive sera (final dilution, 1:100) and 0.5 +/- 0.6 in the presence of pooled human seronegative sera. Addition of phorbol myristate acetate (PMA) enhanced PMN-mediated cytotoxicity against VZV-infected and uninfected targets. PMA-stimulated cytotoxicity was optimal with PMA concentrations of 200 ng/ml and effector-to-target ratios of 10:1, and antibody was not required; killing was detected as early as 3 h after incubation and was maximal after 18 h. Highly purified PMN were capable of mediating both ADCC and PMA-stimulated lysis. Catalase completely inhibited PMA-stimulated PMN cytotoxicity, but had no effect on PMN-mediated ADCC. PMN from patients with chronic granulomatous disease were capable of mediating ADCC, but not PMA-stimulated killing, against VZV-infected targets. Thus, PMN could kill VZV-infected targets by two different mechanisms: ADCC, which required antibody but not hydrogen peroxide (H2O2), and PMA-stimulated cytotoxicity, which required H2O2 but not antibody.