Mechanism of antibody-mediated protection against herpes simplex virus infection in athymic nude mice: requirement of Fc portion of antibody

Polyfunctional antibodies: a path towards precision vaccines for vulnerable populations

Vaccine efficacy determined within the controlled environment of a clinical trial is usually substantially greater than real-world vaccine effectiveness. Typically, this results from reduced protection of immunologically vulnerable populations, such as children, elderly individuals and people with chronic comorbidities. Consequently, these high-risk groups are frequently recommended tailored immunisation schedules to boost responses. In addition, diverse groups of healthy adults may also be variably protected by the same vaccine regimen. Current population-based vaccination strategies that consider basic clinical parameters offer a glimpse into what may be achievable if more nuanced aspects of the immune response are considered in vaccine design. To date, vaccine development has been largely empirical. However, next-generation approaches require more rational strategies. We foresee a generation of precision vaccines that consider the mechanistic basis of vaccine response variations associated with both immunogenetic and baseline health differences. Recent efforts have highlighted the importance of balanced and diverse extra-neutralising antibody functions for vaccine-induced protection. However, in immunologically vulnerable populations, significant modulation of polyfunctional antibody responses that mediate both neutralisation and effector functions has been observed. Here, we review the current understanding of key genetic and inflammatory modulators of antibody polyfunctionality that affect vaccination outcomes and consider how this knowledge may be harnessed to tailor vaccine design for improved public health.

Interleukin-36β provides protection against HSV-1 infection, but does not modulate initiation of adaptive immune responses

Interleukin-36 (IL-36) represents three cytokines, IL-36α, IL-36β and IL-36γ, which bind to the same receptor, IL-1RL2; however, their physiological function(s) remain poorly understood. Here, the role of IL-36 in immunity against HSV-1 was examined using the flank skin infection mouse model. Expression analyses revealed increased levels of IL-36α and IL-36β mRNA in infected skin, while constitutive IL-36γ levels remained largely unchanged. In human keratinocytes, IL-36α mRNA was induced by HSV-1, while IL-1β and TNFα increased all three IL-36 mRNAs. The dominant alternative splice variant of human IL-36β mRNA was isoform 2, which is the ortholog of the known mouse IL-36β mRNA. Mice deficient in IL-36β, but not IL-36α or IL-36γ, succumbed more frequently to HSV-1 infection than wild type mice. Furthermore, IL-36β^−/− mice developed larger zosteriform skin lesions along infected neurons. Levels of HSV-1 specific antibodies, CD8⁺ cells and IFNγ-producing CD4⁺ cells were statistically equal in wild type and IL-36β^−/− mice, suggesting similar initiation of adaptive immunity in the two strains. This correlated with the time at which HSV-1 genome and mRNA levels in primary skin lesions started to decline in both wild type and IL-36β^−/− mice. Our data indicate that IL-36β has previously unrecognized functions protective against HSV-1 infection.

Discovery of potential diagnostic and vaccine antigens in herpes simplex virus 1 and 2 by proteome-wide antibody profiling

Routine serodiagnosis of herpes simplex virus (HSV) infections is currently performed using recombinant glycoprotein G (gG) antigens from herpes simplex virus 1 (HSV-1) and HSV-2. This is a single-antigen test and has only one diagnostic application. Relatively little is known about HSV antigenicity at the proteome-wide level, and the full potential of mining the antibody repertoire to identify antigens with other useful diagnostic properties and candidate vaccine antigens is yet to be realized. To this end we produced HSV-1 and -2 proteome microarrays in Escherichia coli and probed them against a panel of sera from patients serotyped using commercial gG-1 and gG-2 (gGs for HSV-1 and -2, respectively) enzyme-linked immunosorbent assays. We identified many reactive antigens in both HSV-1 and -2, some of which were type specific (i.e., recognized by HSV-1- or HSV-2-positive donors only) and others of which were nonspecific or cross-reactive (i.e., recognized by both HSV-1- and HSV-2-positive donors). Both membrane and nonmembrane virion proteins were antigenic, although type-specific antigens were enriched for membrane proteins, despite being expressed in E. coli.

A panel of IgG1 b12 variants with selectively diminished or enhanced affinity for Fcγ receptors to define the role of effector functions in protection against HIV

Passive transfer of neutralizing antibodies is effective in protecting rhesus macaques against simian/human immunodeficiency virus (SHIV) challenge. In addition to neutralization, effector functions of the crystallizable fragment (Fc) of antibodies are involved in antibody-mediated protection against a number of viruses. We recently showed that interaction between the Fc fragment of the broadly neutralizing antibody IgG1 b12 and cellular Fcγ receptors (FcγRs) plays an important role in protection against SHIV infection in rhesus macaques. The specific nature of this Fc-dependent protection is largely unknown. To investigate, we generated a panel of 11 IgG1 b12 antibody variants with selectively diminished or enhanced affinity for the two main activating FcγRs, FcγRIIa and FcγRIIIa. All 11 antibody variants bind gp120 and neutralize virus as effectively as does wild-type b12. Binding studies using monomeric (enzyme-linked immunosorbent assay [ELISA] and surface plasmon resonance [SPR]) and cellularly expressed Fcγ receptors show decreased (up to 5-fold) and increased (up to 90-fold) binding to FcγRIIa and FcγRIIIa with this newly generated panel of antibodies. In addition, there was generally a good correlation between b12 variant affinity for Fcγ receptor and variant function in antibody-dependent cell-mediated virus inhibition (ADCVI), phagocytosis, NK cell activation assays, and antibody-dependent cellular cytotoxicity (ADCC) assays. In future studies, these b12 variants will enable the investigation of the protective role of individual FcγRs in HIV infection.

Immune control of mammalian gamma-herpesviruses: lessons from murid herpesvirus-4

Many acute viral infections can be controlled by vaccination; however, vaccinating against persistent infections remains problematic. Herpesviruses are a classic example. Here, we discuss their immune control, particularly that of gamma-herpesviruses, relating the animal model provided by murid herpesvirus-4 (MuHV-4) to human infections. The following points emerge: (i) CD8(+) T-cell evasion by herpesviruses confers a prominent role in host defence on CD4(+) T cells. CD4(+) T cells inhibit MuHV-4 lytic gene expression via gamma-interferon (IFN-gamma). By reducing the lytic secretion of immune evasion proteins, they may also help CD8(+) T cells to control virus-driven lymphoproliferation in mixed lytic/latent lesions. Similarly, CD4(+) T cells specific for Epstein-Barr virus lytic antigens could improve the impact of adoptively transferred, latent antigen-specific CD8(+) T cells. (ii) In general, viral immune evasion necessitates multiple host effectors for optimal control. Thus, subunit vaccines, which tend to prime single effectors, have proved less successful than attenuated virus mutants, which prime multiple effectors. Latency-deficient mutants could make safe and effective gamma-herpesvirus vaccines. (iii) The antibody response to MuHV-4 infection helps to prevent disease but is suboptimal for neutralization. Vaccinating virus carriers with virion fusion complex components improves their neutralization titres. Reducing the infectivity of herpesvirus carriers in this way could be a useful adjunct to vaccinating naive individuals with attenuated mutants.

Herpes simplex virus as a tool to define the role of complement in the immune response to peripheral infection

A complex network of interactions exist between the innate and adaptive immune pathways, which act together to elicit a broad and durable host response following pathogen infection. The importance of the complement system in the host's defense against viruses has become increasingly clear as a result of detailed studies using transgenic mouse models that disrupt specific components of this host immune mechanism. We have utilized herpes simplex virus and replication-defective mutant strains to examine the impact of the complement system on development and maintenance of humoral immune responses. Here we review work from our group and others that highlights the central role that complement proteins C3 and C4 and complement receptors Cr1/Cr2 play during viral infection. We discuss the implications of these results in the context of pathogen infection and current vaccine strategies.

Immunization strategies to block the herpes simplex virus type 1 immunoglobulin G Fc receptor

Herpes simplex virus type 1 (HSV-1) glycoprotein gE functions as an immunoglobulin G (IgG) Fc receptor (FcgammaR) that promotes immune evasion. When an IgG antibody binds by the F(ab')(2) domain to an HSV antigen, the Fc domain of some of the same antibody molecules binds to the FcgammaR, which blocks Fc-mediated functions. gE is a type 1 membrane glycoprotein with a large ectodomain that is expressed on the virion envelope and infected-cell surface. Our goal was to determine if immunizing with gE protein fragments could produce antibodies that bind by the F(ab')(2) domain to gE and block the FcgammaR, as measured by competitively inhibiting nonimmune human IgG binding to the FcgammaR. Three gE peptides were constructed in baculovirus spanning almost the entire ectodomain and used to immunize mice and rabbits. Two fragments were highly effective at producing antibodies that bind by the F(ab')(2) domain and block the FcgammaR. The most potent of these two antibodies was far more effective at blocking the FcgammaR than antibodies that are only capable of binding by the Fc domains to the FcgammaR, including anti-gC, anti-gD, and nonimmune IgG. These results suggest that immunizing with gE fragments has potential for preventing immune evasion by blocking activities mediated by the HSV-1 FcgammaR.

Sustained antibody-dependent cell-mediated cytotoxicity (ADCC) in SIV-infected macaques correlates with delayed progression to AIDS

Although several in vitro lines of evidence support the potential power of antibody-dependent cell-mediated cytotoxicity (ADCC) in controlling HIV infection, the role of ADCC in the pathogenesis of HIV infection in vivo remains uncertain. There are few studies to date that longitudinally determine the plasma ADCC activity in HIV-infected subjects. We sought to establish an SIV/macaque model to perform such a longitudinal study. In the rhesus macaque cohort studied here, three of five macaques (designated Group 1) maintained higher plasma ADCC activity for at least 1 year after inoculation with SIV/17E-Br. The ADCC activity of the two remaining macaques (Group 2) fell 12 weeks after inoculation. There were also differences in longitudinal measurements of anti-SIV envelope IgG titers and CD4 counts. Group 1 macaques maintained higher antienvelope IgG titers and higher CD4(+) T cell numbers as late as 60 weeks postinoculation, while Group 2 macaques had significantly lower titers at 1 year postinoculation and lower CD4(+) T cell counts by 30 weeks postinoculation. Our study shows a correlation between humoral response, ADCC activity, and disease progression (as measured by CD4(+) T cell counts). In these animals, ADCC activity is associated with delayed progression to AIDS. Further studies are underway to determine if ADCC is a protective immune response in SIV infection or if ADCC is a marker of intact cellular and humoral immune responses.

The antiviral activity of antibodies in vitro and in vivo

This chapter discusses in vitro and in vivo antiviral activities of antibody. Since experimentation is far easier in vitro , researchers have been sought to develop in vitro assays that are expected to predict activity in vivo . This could be important in both vaccine design and in passive antibody administration. The proposed mechanisms of in vitro neutralization range from those requiring binding of a single antibody molecule to virus to those requiring substantially complete antibody coating of virus. In vitro, antiviral activity can be separated into activity against virions and activity against infected cells. The activity against virions most often considered is neutralization that can be defined as the loss of infectivity, which ensues when antibody molecule(s) bind to a virus particle, and occurs without the involvement of any other agency. In vivo, it is conventional to distinguish phenomenologically between two types of antibody antiviral activity. One of them is the ability of antibody to protect against infection when it is present before or immediately following infection. Evidence for a number of viruses in vitro indicates that lower antibody concentrations are required to inhibit infection propagated by free virus than are required to inhibit infection propagated by cell-to-cell spread.

Antibody-dependent cell-mediated cytotoxicity can protect PBMC from infection by cell-associated HIV-1

We have developed a novel in vitro assay system to study the role of antibody-dependent cell-mediated cytotoxicity (ADCC) in protection against HIV-1 infection by cell-associated virus. HIV-1-infected NK-resistant cells are mixed with specific antibody and unstimulated PBMC and ADCC is allowed to occur over several hours. The PBMC are then activated and cultured to allow virus replication in newly infected T cells. To ensure that ADCC is the only mechanism by which protection could occur we have used haptenated (TNP) infected cells and anti-hapten antibody. Anti-hapten sera completely protected PBMC from infection by haptenated HIV-1-infected cells in ADCC protection assays. F(ab')2 fragments of anti-hapten IgG showed no protection, confirming that ADCC was responsible for protection by anti-hapten IgG. PCR analysis for HIV-1 DNA confirmed the elimination of infected cells. We believe this to be the first direct demonstration that ADCC alone can protect PBMC from infection by cell-associated HIV-1.

In vivo immune evasion mediated by the herpes simplex virus type 1 immunoglobulin G Fc receptor

Herpes simplex virus (HSV) glycoproteins gE and gI form an immunoglobulin G (IgG) Fc receptor (FcgammaR) that binds the Fc domain of human anti-HSV IgG and inhibits Fc-mediated immune functions in vitro. gE or gI deletion mutant viruses are avirulent, probably because gE and gI are also involved in cell-to-cell spread. In an effort to modify FcgammaR activity without affecting other gE functions, we constructed a mutant virus, NS-gE339, that has four amino acids inserted into gE within the domain homologous to mammalian IgG FcgammaRs. NS-gE339 expresses gE and gI, is FcgammaR-, and does not participate in antibody bipolar bridging since it does not block activities mediated by the Fc domain of anti-HSV IgG. In vivo studies were performed with mice because the HSV-1 FcgammaR does not bind murine IgG; therefore, the absence of an FcgammaR should not affect virulence in mice. NS-gE339 causes disease at the skin inoculation site comparably to wild-type and rescued viruses, indicating that the FcgammaR- mutant virus is pathogenic in animals. Mice were passively immunized with human anti-HSV IgG and then infected with mutant or wild-type virus. We postulated that the HSV-1 FcgammaR should protect wild-type virus from antibody attack. Human anti-HSV IgG greatly reduced viral titers and disease severity in NS-gE339-infected animals while having little effect on wild-type or rescued virus. We conclude that the HSV-1 FcgammaR enables the virus to evade antibody attack in vivo, which likely explains why antibodies are relatively ineffective against HSV infection.

Directed selection of recombinant human monoclonal antibodies to herpes simplex virus glycoproteins from phage display libraries

Human monoclonal antibodies have considerable potential in the prophylaxis and treatment of viral disease. However, only a few such antibodies suitable for clinical use have been produced to date. We have previously shown that large panels of human recombinant monoclonal antibodies against a plethora of infectious agents, including herpes simplex virus types 1 and 2, can be established from phage display libraries. Here we demonstrate that facile cloning of recombinant Fab fragments against specific viral proteins in their native conformation can be accomplished by panning phage display libraries against viral glycoproteins "captured" from infected cell extracts by specific monoclonal antibodies immobilized on ELISA plates. We have tested this strategy by isolating six neutralizing recombinant antibodies specific for herpes simplex glycoprotein gD or gB, some of which are against conformationally sensitive epitopes. By using defined monoclonal antibodies for the antigen-capture step, this method can be used for the isolation of antibodies to specific regions and epitopes within the target viral protein. For instance, monoclonal antibodies to a nonneutralizing epitope can be used in the capture step to clone antibodies to neutralizing epitopes, or antibodies to a neutralizing epitope can be used to clone antibodies to a different neutralizing epitope. Furthermore, by using capturing antibodies to more immunodominant epitopes, one can direct the cloning to less immunogenic ones. This method should be of value in generating antibodies to be used both in the prophylaxis and treatment of viral infections and in the characterization of the mechanisms of antibody protective actions at the molecular level.

A novel function of the herpes simplex virus type 1 Fc receptor: participation in bipolar bridging of antiviral immunoglobulin G

We describe a novel function of the Fc receptor of herpes simplex virus type 1 (HSV-1), its ability to participate in antibody bipolar bridging. This refers to the binding of a single immunoglobulin G (IgG) molecule by its Fab end to its antigenic target and by its Fc end to an Fc receptor (FcR). We demonstrate that various immune IgG antibodies, including polyclonal rabbit antibodies to HSV-1 glycoproteins gC1 and gD1 and monoclonal human antibody to gD1 blocked rosetting of IgG-coated erythrocytes at IgG concentrations 100- to 2,000-fold lower than required for rosette inhibition with nonimmune IgG. Steric hindrance did not account for the observed differences between immune and nonimmune IgG since rabbit anti-gC1 F(ab')2 fragments did not block rosetting. Murine anti-gC1 or anti-gD1 IgG, a species of IgG incapable of binding by its Fc end to the HSV-1 FcR, also did not block rosetting. When cells were infected with a gC1-deficient mutant, anti-gC1 IgG inhibited rosetting to the same extent as nonimmune IgG. This indicates that binding by the Fab end of the IgG molecule was required for maximum inhibition of rosetting. Bipolar bridging was shown to occur even when small concentrations of immune IgG were present in physiologic concentrations of nonimmune IgG. The biologic relevance of antibody bipolar bridging was evaluated by comparing antibody- and complement-dependent virus neutralization of an FcR-negative mutant and its parent HSV-1 strain. By engaging the Fc end of antiviral IgG, the parent strain resisted neutralization mediated by the classical complement pathway. These observations provide insight into the role of the HSV-1 FcR in pathogenesis and may help explain the function of FcR detected on other microorganisms.

Immunogenicity of herpes simplex virus glycoprotein gB-1-related protein produced in yeast

A protein related to glycoprotein B of herpes simplex virus type 1 (HSV-1) produced in yeast (ygB-1) was purified with an immunoadsorbent. The molecular weight of the purified ygB-1 as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis was 96,000. Mice injected twice with ygB-1 adsorbed to alum developed ELISA antibody to ygB-1, neutralizing antibody to HSV-1 and a lymphoproliferative response to ygB-1 and HSV-1. The immunized mice were protected against intraperitoneal and corneal challenge with HSV-1. Latent infection in the trigeminal ganglia after corneal challenge was also inhibited by immunization with ygB-1. Guinea-pigs pigs immunized with ygB-1 adsorbed to alum also developed ELISA antibody to to ygB-1 and neutralizing antibody to both types of HSV. After the second dose, strong lymphoproliferative responses were seen upon stimulation with HSV-2. Animals were protected against intravaginal challenge with HSV type 2.

Passive transfer of anti-HSV-1 IgG protects against stromal keratitis in mice

Cellular immune mechanisms are felt to play a primary role in modulating responses to herpes simplex virus (HSV) infections, but the role of anti-HSV antibody is less clear. We first investigated the effects of passive transfer of murine serum containing anti-HSV antibody and then fractionated IgG subclasses on the development of HSV stromal keratitis in mice. Both immune sera and fractionated IgG's from these sera were effective in preventing stromal keratitis in susceptible mice. Non-IgG immunoglobulins and other serum proteins are unnecessary and inadequate in transferring protection; transfer of sera depleted of IgG had no influence on the development of keratitis. These results suggest an important role for anti-HSV antibody in modulating destructive corneal responses to HSV.

Immunological mechanisms giving rise to latency of herpes simplex virus in the spinal ganglia of the mouse

In the model of genital herpes simplex virus (HSV)-infection of mice, early latency could be induced by passive immunization with HSV-specific antibodies and, to a lesser degree, by adoptive transfer of immune lymphocytes prepared from spleen and draining lymph nodes of genitally infected syngeneic mice. Conversely, spontaneously occurring latency was inhibited by treatment of the animals with cyclophosphamide (Cph) and, to a lesser degree, with cyclosporin A (CyA). Whereas the effect of CyA could be compensated by passively administered HSV-specific antibodies, that of Cph could not. Apparently specific antibodies cooperate with a non-specific proliferating cell type, probably macrophages and/or NK-cells, as could be demonstrated by significantly reduced antibody effect in silica-treated mice. Moreover, F(ab)2 fragments, in contrast to complete antibody molecules, were inactive. HSV-specific antibodies and also immune lymphocytes had little effect on virus production in the mucous membranes, immune lymphocytes being at least as active as antibodies. It is therefore not probable that latency is induced by attenuation of the peripheral disease. It can rather be concluded that the neuron itself is the target for the action of specific antibodies, cooperating in turn with macrophages and/or NK cells.

Prevention and treatment of experimental herpes simplex virus encephalitis with human immune serum globulin

Pooled human immunoglobulin suitable for intravenous administration (IGIV) was evaluated in the prophylaxis and treatment of herpes simplex virus (HSV) type 1 encephalitis in a murine model. Four-week-old BALB/c mice received a single intraperitoneal injection of IGIV or saline 24 h before or up to 24 h after intranasal infection with 10(4.6) PFU of HSV type 1. Treatment with IGIV was protective against death, and the protective effects were dose and time dependent. Treatment with IGIV blocked the production of HSV antibody by infected mice and reduced the number of trigeminal ganglia containing latent virus. Removal of neutralizing antibody from the IGIV pool did not eliminate the protective effect, whereas F(ab)2 fragments of IGIV, which had virus-neutralizing activity that was identical to that of native IGIV, conferred no protection against death. Pooled human IGIV was effective for the prevention and treatment of HSV encephalitis in mice. Antibody-mediated protection required the Fc portion of the immunoglobulin molecule but did not require the direct neutralization of virus.

Protection against herpes simplex virus infection in mice by recombinant murine interferon-beta in combination with antibody

A recombinant murine interferon -beta (rMuIFN-beta) was used to suppress the development of skin lesions and death of mice after challenge with herpes simplex virus (HSV) type 1 (HSV-1). Depilated female BALB/c mice were inoculated intradermally with HSV-1, Hayashida strain, and were administered various concentrations of interferon (IFN) intraperitoneally 3 h later. The treatment with IFN was given once a day for 10 successive days. Under the conditions in which almost all control mice died after development of severe zosteriform skin lesions, the mortality of mice treated with IFN (8 X 10(5) or 8 X 10(4) U/mouse) was less than 50% (9/20 and 4/10, respectively), though all mice treated with a lower dose of IFN (8 X 10(3) U/mouse) died. Titration revealed that there was no significant suppression of virus growth by IFN in the skin or dorsal root ganglia, but it was significantly suppressed in the brain. The protective effect of IFN was enhanced when it was used in combination with human anti-HSV antibody having a neutralizing titer (NT) of 1:16. All mice treated with IFN (8 X 10(5) U/mouse) and antibody (NT, 1:16) survived, and only 40% of them developed slight zosteriform skin lesions. The effect of the combination was observed even when both IFN and antibody were diluted 1:10. The protective effect of IFN was also observed when athymic nude mice were used as the host. In this system, though the IFN-treated nude mice survived significantly longer than the controls, they finally died. In antibody- or acyclovir (ACV)-treated nude mice, there was also a prolongation of survival time as compared with control mice. The effect of antibody was enhanced by the addition of IFN, but IFN did not potentiate the effect of ACV.

Interferon-gamma and B cell stimulatory factor-1 reciprocally regulate Ig isotype production

Gamma interferon (IFN-gamma) and B cell stimulatory factor-1 (BSF-1), also known as interleukin-4, are T cell-derived lymphokines that have potent effects on B cell proliferation and differentiation. They are often secreted by distinct T cell clones. It is now shown that IFN-gamma stimulates the expression of immunoglobulin (Ig) of the IgG2a isotype and inhibits the production of IgG3, IgG1, IgG2b, and IgE. By contrast, BSF-1 has powerful effects in promoting switching to the expression of IgG1 and IgE but markedly inhibits IgM, IgG3, IgG2a, and IgG2b. These results indicate that BSF-1 and IFN-gamma as well as the T cells that produce them may act as reciprocal regulatory agents in the determination of Ig isotype responses. The effects of IFN-gamma and BSF-1 on isotype expression are independent.

Ability of monoclonal antibody to herpes simplex virus glycoprotein gB to promote healing of herpetic skin lesions in nude mice

The effect of monoclonal antibody (MCA) to glycoprotein gB of herpes simplex virus (HSV) was studied in athymic nude mice inoculated with HSV intracutaneously in the midflank. HS1, the MCA used in the study, had a high neutralizing titer (1:2048) and had antibody-dependent cell-mediated cytotoxicity. HS1 was injected intraperitoneally at various intervals after HSV infection. HS1 injected 3 h after infection inhibited the development of skin lesions and most mice survived. Administration of HS1 at the time the local skin erosions appeared at the inoculated site (4-7 days after infection) was also effective, and in four of eight mice skin lesions completely healed. Furthermore, in three of four mice that survived, latent infections in the ganglia were also prevented as evidenced by the failure to detect HSV by co-cultivation with Vero cells. Administration of HS1 after the development of zosteriform skin lesions (5-9 days after infection) reduced virus in the ganglia and prolonged the survival time, though the disease was not completely arrested and all the mice died eventually.

Effects of combined use of acyclovir and antibody in athymic nude mice inoculated intracutaneously with herpes simplex virus

Antiviral effects of acyclovir (ACV) and antibody were studied in athymic nude mice inoculated intracutaneously in the midflank with herpes simplex virus type 1. Three hours after virus inoculation, treatment was initiated. In ACV-treated mice, the development of skin lesions was inhibited and the mean survival time was prolonged as compared with controls. Treatment with ACV markedly reduced the viral titers both at the inoculation site and in the neural tissues (dorsal root ganglia, spinal cord and brain). Transfer of antibody was also effective in controlling infection as described previously. The use of ACV plus antibody was more effective than the use of ACV alone and in 5 of 17 mice the disease was completely inhibited. Furthermore, in the mice that survived, latent infections in the ganglia were also prevented. These results indicate that treatment with ACV plus antibody is highly effective against herpes simplex virus infection in the immunocompromised host.

Passive immunization of mice with monoclonal antibodies to glycoprotein gB of herpes simplex virus

To investigate the protective ability of monoclonal antibodies (MCAs) to viral glycoprotein in herpes simplex virus (HSV) infection, athymic nude mice were inoculated intracutaneously with HSV type-1 (HSV-1) in the midflank. Three hours after inoculation, one group of mice was passively immunized with one of a series of MCAs to glycoprotein gB of HSV-1, and a control group of mice was given phosphate buffered saline alone. The control mice died within 16 days after infection, whereas the mice passively immunized with any of the MCA showed suppressed development of skin lesions. Three of six mice given MCA failed to develop any visible lesions and no HSV could be isolated from the lumbar dorsal root ganglia of these mice 60 days after the challenge. BALB/c mice were also protected from infection with HSV type 2 by passive immunization with MCA to HSV-1 gB.

Antibody-dependent cellular cytotoxicity and natural killer cytotoxicity of peritoneal cells from nude mice to herpes simplex virus-infected cells

Nude BALB/c mice (athymic) were more susceptible to fatal herpes simplex virus (HSV) than normal BALB/c mice (P = 0.002). The peritoneal cells of nude mice mediated levels of antibody-dependent cellular cytotoxicity (ADCC) of equal or greater magnitude than cells from normal BALB/c, heterozygote nu/+, or C57BL/6 mice. Unstimulated natural killer cytotoxicity of peritoneal cells from nude mice was higher (P less than 0.05) than that mediated by cells from C57BL/6 mice. Nude mice failed to make anti-HSV ADCC antibody 6 to 14 days post HSV inoculation, at times when nu/+, BALB/c, and C57BL/6 mice produced antibody. Passive reconstitution of nude mice with high titer intraperitoneal anti-HSV immune globulin provided circulating anti-HSV ADCC antibody and significant protection against lethal HSV infection.

Immunotherapy of murine leukemia. IX. The requirement for the Fc portion of antibody for successful passive serum therapy of Friend leukemia virus-induced disease

The possible role of an antibody-dependent cellular cytotoxicity (ADCC)-type mechanism in the passive serum therapy of Friend leukemia virus (FLV)-induced erythroleukemia has been investigated by determining whether successful serum protection requires an intact Fc portion on the administered antibody. F(ab')2 fragments of IgG extracted from chimpanzee anti-FLV and goat anti-FLV gp71 antisera were prepared and compared with whole serum and uncleaved IgG for their capacity to protect DBA/2 mice against challenge with leukemogenic dose of FLV. Despite demonstrating in vitro virus neutralizing activity equivalent to that seen with antiviral serum or IgG, the virus-specific F(ab')2 preparations were devoid of protective activity. Given that passively administered F(ab')2 of goat origin have been reported to persist at stable levels in the mouse circulation, the failure of these F(ab')2 preparations to protect against virus challenge cannot be ascribed to rapid clearance from the treated animals. These results indicate that the passive serum therapy of FLV-induced disease is Fc dependent, consistent with the involvement of an ADCC-type mechanism, as well as confirming the previous suggestion that virus neutralization does not represent the sole mechanism of serum protection in this system.