Passive immunization with monoclonal antibodies against herpes simplex virus glycoproteins protects mice against herpetic ocular disease

Effector functions are required for broad and potent protection of neonatal mice with antibodies targeting HSV glycoprotein D

Multiple failed herpes simplex virus (HSV) vaccine candidates induce robust neutralizing antibody (Ab) responses in clinical trials, raising the hypothesis that Fc-domain-dependent effector functions may be critical for protection. While neonatal HSV (nHSV) infection results in mortality and lifelong neurological morbidity in humans, it is uncommon among neonates with a seropositive birthing parent, supporting the hypothesis that Ab-based therapeutics could protect neonates from HSV. We therefore investigated the mechanisms of monoclonal Ab (mAb)-mediated protection in a mouse model of nHSV infection. For a panel of glycoprotein D (gD)-specific mAbs, neutralization and effector functions contributed to nHSV-1 protection. In contrast, effector functions alone were sufficient to protect against nHSV-2, exposing a functional dichotomy between virus types consistent with vaccine trial results. Effector functions are therefore crucial for protection by these gD-specific mAbs, informing effective Ab and vaccine design and demonstrating the potential of polyfunctional Abs as therapeutics for nHSV infections.

Antibody effector functions are required for broad and potent protection of neonates from herpes simplex virus infection

The failure of multiple herpes simplex virus (HSV) vaccine candidates that induce neutralizing antibody responses raises the hypothesis that other activities, such as Fc domain-dependent effector functions, may be critical for protection. While neonatal HSV (nHSV) infection result in mortality and lifelong neurological morbidity in humans, it is uncommon among neonates with a seropositive birthing parent, suggesting the potential efficacy of antibody-based therapeutics to protect neonates. We therefore investigated the mechanisms of monoclonal antibody (mAb)-mediated protection in a mouse model of nHSV infection. Both neutralization and effector functions contributed to robust protection against nHSV-1. In contrast, effector functions alone were sufficient to protect against nHSV-2, exposing a functional dichotomy between virus types that is consistent with vaccine trial results. Together, these results emphasize that effector functions are crucial for optimal mAb-mediated protection, informing effective Ab and vaccine design, and demonstrating the potential of polyfunctional Abs as potent therapeutics for nHSV infections.

Lower expression of KAI1 as a biomarker of poor survival prognosis of melanoma combined with colorectal cancer metastasis

Objective

This study aimed to investigate the correlation between KAI1 (CD82) and miR-633 expression and prognosis and survival time of patients with melanoma combined with colorectal cancer (CRC).

Methods

Clinical and follow-up data of melanoma and CRC patients were recorded, and the expression levels of KAI1 and miR-633 were detected. Pearson chi-square tests and Spearman correlation coefficient were used to analyze the relationship between prognosis and related parameters in these patients. Cox proportional risk regression and receiver operating characteristic curve analyses were used.

Results

Overall, 195 patients were included. KAI1 and miR-633 expression levels were significantly correlated with the prognosis of patients with melanoma combined with CRC. Spearman correlation analysis showed that the expression levels of KAI1 and miR-633 were significantly correlated with the prognosis of patients. Multivariate Cox regression analysis suggested that low expression levels of KAI1 and high expression levels of miR-633 indicated shorter survival time for patients.

Conclusions

KAI1 expression was significantly correlated with melanoma and CRC patient prognosis. When KAI1 expression levels were low, the patient survival time was poor.

Herpes Simplex Virus 1 (HSV-1) 0ΔNLS Live-Attenuated Vaccine Protects against Ocular HSV-1 Infection in the Absence of Neutralizing Antibody in HSV-1 gB T Cell Receptor-Specific Transgenic Mice

The contribution of T cell and antibody responses following vaccination in resistance to herpes simplex virus 1 (HSV-1) infection continues to be rigorously investigated. In the present article, we explore the contribution of CD8+ T cells specific for the major antigenic epitope for HSV-1 glycoprotein B (gB498-505, gB) in C57BL/6 mice using a transgenic mouse (gBT-I.1) model vaccinated with HSV-1 0ΔNLS. gBT-I.1-vaccinated mice did not generate a robust neutralization antibody titer in comparison to the HSV-1 0ΔNLS-vaccinated wild-type C57BL/6 counterpart. Nevertheless, the vaccinated gBT-I.1 mice were resistant to ocular challenge with HSV-1 compared to vehicle-vaccinated animals based on survival and reduced corneal neovascularization but displayed similar levels of corneal opacity. Whereas there was no difference in the virus titer recovered from the cornea comparing vaccinated mice, HSV-1 0ΔNLS-vaccinated animals possessed significantly less infectious virus during acute infection in the trigeminal ganglia (TG) and brain stem compared to the control-vaccinated group. These results correlated with a significant increase in gB-elicited interferon-γ (IFN-γ), granzyme B, and CD107a and a reduction in lymphocyte activation gene 3 (LAG-3), programmed cell death 1 (PD-1), and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) expressed by TG infiltrating gB-specific CD8+ T cells from the HSV-1 0ΔNLS-vaccinated group. Antibody depletion of CD8+ T cells in HSV-1 0ΔNLS-vaccinated mice rendered animals highly susceptible to virus-mediated mortality similar to control-vaccinated mice. Collectively, the HSV-1 0ΔNLS vaccine is effective against ocular HSV-1 challenge, reducing ocular neovascularization and suppressing peripheral nerve virus replication in the near absence of neutralizing antibody in this unique mouse model.IMPORTANCE The role of CD8+ T cells in antiviral efficacy using a live-attenuated virus as the vaccine is complicated by the humoral immune response. In the case of the herpes simplex virus 1 (HSV-1) 0ΔNLS vaccine, the correlate of protection has been defined to be primarily antibody driven. The current study shows that in the near absence of anti-HSV-1 antibody, vaccinated mice are protected from subsequent challenge with wild-type HSV-1 as measured by survival. The efficacy is lost following depletion of CD8+ T cells. Whereas increased survival and reduction in virus replication were observed in vaccinated mice challenged with HSV-1, cornea pathology was mixed with a reduction in neovascularization but no change in opacity. Collectively, the study suggests CD8+ T cells significantly contribute to the host adaptive immune response to HSV-1 challenge following vaccination with an attenuated virus, but multiple factors are involved in cornea pathology in response to ocular virus challenge.

Monoclonal Antibodies, Derived from Humans Vaccinated with the RV144 HIV Vaccine Containing the HVEM Binding Domain of Herpes Simplex Virus (HSV) Glycoprotein D, Neutralize HSV Infection, Mediate Antibody-Dependent Cellular Cytotoxicity, and Protect Mice from Ocular Challenge with HSV-1

The RV144 HIV vaccine trial included a recombinant HIV glycoprotein 120 (gp120) construct fused to a small portion of herpes simplex virus 1 (HSV-1) glycoprotein D (gD) so that the first 40 amino acids of gp120 were replaced by the signal sequence and the first 27 amino acids of the mature form of gD. This region of gD contains most of the binding site for HVEM, an HSV receptor important for virus infection of epithelial cells and lymphocytes. RV144 induced antibodies to HIV that were partially protective against infection, as well as antibodies to HSV. We derived monoclonal antibodies (MAbs) from peripheral blood B cells of recipients of the RV144 HIV vaccine and showed that these antibodies neutralized HSV-1 infection in cells expressing HVEM, but not the other major virus receptor, nectin-1. The MAbs mediated antibody-dependent cellular cytotoxicity (ADCC), and mice that received the MAbs and were then challenged by corneal inoculation with HSV-1 had reduced eye disease, shedding, and latent infection. To our knowledge, this is the first description of MAbs derived from human recipients of a vaccine that specifically target the HVEM binding site of gD. In summary, we found that monoclonal antibodies derived from humans vaccinated with the HVEM binding domain of HSV-1 gD (i) neutralized HSV-1 infection in a cell receptor-specific manner, (ii) mediated ADCC, and (iii) reduced ocular disease in virus-infected mice.IMPORTANCE Herpes simplex virus 1 (HSV-1) causes cold sores and neonatal herpes and is a leading cause of blindness. Despite many trials, no HSV vaccine has been approved. Nectin-1 and HVEM are the two major cellular receptors for HSV. These receptors are expressed at different levels in various tissues, and the role of each receptor in HSV pathogenesis is not well understood. We derived human monoclonal antibodies from persons who received the HIV RV144 vaccine that contained the HVEM binding domain of HSV-1 gD fused to HIV gp120. These antibodies were able to specifically neutralize HSV-1 infection in vitro via HVEM. Furthermore, we showed for the first time that HVEM-specific HSV-1 neutralizing antibodies protect mice from HSV-1 eye disease, indicating the critical role of HVEM in HSV-1 ocular infection.

Immunotherapeutic strategies for sexually transmitted viral infections: HIV, HSV and HPV

More than 1 million sexually transmitted infections (STIs) are acquired each day globally. Etiotropic drugs cannot effectively control infectious diseases therefore, there is a dire need to explore alternative strategies especially those based on the regulation of immune system. The review discusses all rational approaches to develop better understanding towards immunotherapeutic strategies based on modulation of immune system in an attempt to curb the elevating risk of infectious diseases such as HIV, HPV and HSV because of their high prevalence. Development of monoclonal antibodies, vaccines and several other immune based treatments are promising alternative strategies that are offering new opportunities to eradicate pathogens.

Prevention of herpes simplex virus induced stromal keratitis by a glycoprotein B-specific monoclonal antibody

The increasing incidence of acyclovir (ACV) and multidrug-resistant strains in patients with corneal HSV-1 infections leading to Herpetic Stromal Keratitis (HSK) is a major health problem in industrialized countries and often results in blindness. To overcome this obstacle, we have previously developed an HSV-gB-specific monoclonal antibody (mAb 2c) that proved to be highly protective in immunodeficient NOD/SCID-mice towards genital infections. In the present study, we examined the effectivity of mAb 2c in preventing the immunopathological disease HSK in the HSK BALB/c mouse model. Therefore, mice were inoculated with HSV-1 strain KOS on the scarified cornea to induce HSK and subsequently either systemically or topically treated with mAb 2c. Systemic treatment was performed by intravenous administration of mAb 2c 24 h prior to infection (pre-exposure prophylaxis) or 24, 40, and 56 hours after infection (post-exposure immunotherapy). Topical treatment was performed by periodical inoculations (5 times per day) of antibody-containing eye drops as control, starting at 24 h post infection. Systemic antibody treatment markedly reduced viral loads at the site of infection and completely protected mice from developing HSK. The administration of the antiviral antibody prior or post infection was equally effective. Topical treatment had no improving effect on the severity of HSK. In conclusion, our data demonstrate that mAb 2c proved to be an excellent drug for the treatment of corneal HSV-infections and for prevention of HSK and blindness. Moreover, the humanized counterpart (mAb hu2c) was equally effective in protecting mice from HSV-induced HSK when compared to the parental mouse antibody. These results warrant the future development of this antibody as a novel approach for the treatment of corneal HSV-infections in humans.

Suppression of transcription factor early growth response 1 reduces herpes simplex virus 1-induced corneal disease in mice

Herpes simplex virus 1 replication initiates angiogenesis and inflammation in the cornea. This can result in herpetic stromal keratitis (HSK), which is a leading cause of infection-induced corneal blindness. Host cellular factors mediate the progression of HSK, but little is known about these cellular factors and their mechanisms of action. We show here that the expression of the cellular transcription factor early growth response 1 (Egr-1) in HSV-1-infected mouse corneas was enhanced. Enhanced Egr-1 expression aggravated HSK by increasing viral replication and subsequent neovascularization with high levels of potent angiogenic factors, fibroblast growth factor 2, and vascular endothelial growth factor. Furthermore, Egr-1 deficiency due to a targeted disruption of the gene or knockdown of Egr-1 expression topically using a DNA-based enzyme significantly reduced HSK by decreasing both viral replication and the angiogenic response. The present study provides the first evidence that endogenous Egr-1 aggravates HSK and that blocking Egr-1 reduces corneal damage.

Kinetics of immune cell infiltration in vaccinia virus keratitis

PURPOSE

Vaccinia virus keratitis leading to blindness is a severe complication of smallpox vaccination. The clinical manifestations of vaccinia virus keratitis are similar to those of herpes simplex virus keratitis, a well-studied immunopathologic disease. Vaccinia virus keratitis is likely to involve an immunopathologic component, but little is known about the pathogenesis of the disease. The goal of this study was to determine type and kinetics of immune cell infiltration in the cornea during vaccinia virus keratitis.

METHODS

Rabbit eyes were trephined and inoculated with 1x10(5) pfu of the Dryvax strain of the vaccinia virus. On days 2, 4, 7, 10, 14, and 28 after infection, the animals were scored for clinical disease and eye sections were stained for B cells, CD4+ cells, CD8+ cells, and neutrophils. The eyelid, ciliary body, cornea, iris, iridocorneal angle, and choroid were examined.

RESULTS

Corneal vaccinia virus challenge resulted in the infiltration of B cells, CD4+ cells, CD8+ cells, and neutrophils into the cornea and eyelids. Neutrophils were the predominant cell type on days 2 and 3 after infection, whereas CD4+ cells were the predominant cell type detected in corneas on days 4 through 10. CD8+ cells and B cells peaked on day 10, but at lower levels than CD4+ cells and neutrophils.

CONCLUSIONS

These results suggest that sequential migration of neutrophils, then CD4+ cells, plays an important role in vaccinia virus keratitis.

Specific antibody production in herpes keratitis: intraocular inflammation and corneal neovascularisation as predicting factors

PURPOSE

The purpose of the study is to investigate whether analysis of specific antibody synthesis can aid the diagnosis of herpes keratitis.

METHODS

Aqueous humor was collected from 39 patients with presumed recurrent herpes keratitis, including 23 consulting for keratitis and 16 patients scheduled for penetrating keratoplasty. Local antibody production was ascertained by analysis of paired aqueous humor/serum samples, using a modified micro-ELISA technique.

RESULTS

Local production of antibodies was found in 32 patients (82%): anti-herpes simplex virus (HSV) antibodies in 26 (67%) and anti-varicella zoster virus (VZV) antibodies in 11 (28%). Twenty of 23 patients with active keratitis (87%), and 12 of 16 undergoing keratoplasty (75%), tested positive. Five patients had local production of both anti-HSV and anti-VZV antibodies, whereas seven patients tested negative. Local antibody production was significantly associated with intraocular inflammation (P<0.05), corneal neovascularisation (P<0.05), and positive response to anti-viral treatment (P<0.05). No complications were encountered in sampling aqueous humor.

CONCLUSIONS

Assessment of local anti-HSV and -VZV antibody production is a safe and reliable diagnostic procedure for recurrent herpes keratitis. It might be particularly helpful in patients presenting with intraocular inflammation and neovascularisation since it discriminates between herpes and non-herpes pathologies and may therefore be useful for preventive and therapeutic strategies.

Therapeutic applications of monoclonal antibodies

Researchers have sought therapeutic applications for monoclonal antibodies since their development in 1975. However, murine-derived monoclonal antibodies may cause an immunogenic response in human patients, reducing their therapeutic efficacy. Chimeric and humanized antibodies have been developed that are less likely to provoke an immune reaction in human patients than are murine-derived antibodies. Antibody fragments, bispecific antibodies, and antibodies produced through the use of phage display systems and genetically modified plants and animals may aid researchers in developing new uses for monoclonal antibodies in the treatment of disease. Monoclonal antibodies may have a number of promising potential therapeutic applications in the treatment of asthma, autoimmune diseases, cancer, poisoning, septicemia, substance abuse, viral infections, and other diseases.

Twenty-five-year panorama of corneal immunology: emerging concepts in the immunopathogenesis of microbial keratitis, peripheral ulcerative keratitis, and corneal transplant rejection

PURPOSE

To describe the most recent advances in our understanding of the cellular and molecular mechanisms involved in the immunopathogenesis of corneal immunoinflammatory disorders including microbial keratitis, peripheral ulcerative keratitis. and allograft rejection.

METHODS

Review of the published peer-reviewed literature that has contributed significantly to our modern understanding of corneal immunology. In addition, the authors have summarized the information in conceptual diagrams that highlight the critical cellular and molecular pathways that lead to corneal immune responses in the two most thoroughly studied corneal immune disorders, herpes simplex keratitis (HSK) and transplant rejection.

RESULTS

In spite of the wide array of molecular and cellular factors that mediate corneal immunity, critical mechanistic facets are shared by the various corneal immunoinflammatory disorders. These include activation and migration of local antigen-presenting cells (APCs), including Langerhans cells (LCs), upregulation in pleiotropic proinflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor-alfa (TNF-alpha) that can mediate a wide array of immune functions in addition to up-regulating protease expression. and chemokines that play a critical role on the one hand in attracting nonantigen-specific inflammatory cells such as neutrophils and on the other in attracting CD4+ T helper type 1 (Th1) cells that mediate most of the destruction in the cornea.

CONCLUSIONS

In the last 25 years, we have seen our field develop from a descriptive stage into a new phase where the fundamental processes that mediate and effect corneal immunity are being accurately deciphered. It is anticipated that this new knowledge will allow development of specific molecular and genetic therapeutic strategies that could target critical steps in the immunopathogenesis of disease without the untoward side-effects of nonspecific generalized immune suppression that still remains the standard of care today.

Plasmid DNA encoding IFN-alpha 1 antagonizes herpes simplex virus type 1 ocular infection through CD4+ and CD8+ T lymphocytes

The present study was undertaken to further characterize the anti-viral efficacy of a plasmid DNA encoding IFN-alpha1 against ocular herpes simplex virus type 1 (HSV-1) infection. In mice ocularly treated with plasmid DNA encoding IFN-alpha 1, the efficacy of the transgene was inversely proportional to the amount of virus used to infect the mice. Ocular treatment of mice with the IFN-alpha 1 transgene was the only mucosal route tested that showed efficacy against ocular HSV-1 infection compared with vaginal or intranasal delivery. Mice treated with the plasmid DNA encoding IFN-alpha 1 showed a significant reduction in viral Ag expression in the eyes and trigeminal ganglion that correlated with a reduction in immune cell infiltration into the cornea and iris on days 3 and 6 postinfection, as evidenced by immunohistochemical staining. Depleting mice of either CD4+ or CD8+ T lymphocytes completely blocked the resistance to herpes simplex virus type 1-induced mortality in mice treated with the IFN-alpha 1 transgene. In the absence of infection, the application of naked DNA encoding IFN-alpha 1 significantly increased the levels of IL-6- and IFN-gamma-inducible protein 10 transcript expression in the corneas 24 h post-treatment. Expression of the plasmid construct following topical application in the eye included the rectus muscles proximal to the cornea as well as the spleen. Collectively, the protective efficacy of the IFN-alpha 1 transgene against ocular HSV-1 infection is dependent upon the local or distal participation of CD4+ and CD8+ T lymphocytes early in the course of the infection, suggesting an indirect effect of the transgene against HSV-1-induced mortality.

Localization of a passively transferred human recombinant monoclonal antibody to herpes simplex virus glycoprotein D to infected nerve fibers and sensory neurons in vivo

A human recombinant monoclonal antibody to herpes simplex virus (HSV) glycoprotein D labeled with the fluorescent dye Cy5 was administered to mice infected in the cornea with HSV type 1 (HSV-1). The distribution of such antibody in the corneas and trigeminal ganglia of the mice was then investigated by confocal microscopy. The antibody was detected on HSV-infected nerve fibers in the cornea--identified by colocalization with HSV antigens and the neuritic markers neurofilament, GAP-43, synapsin-1, and CNPase--and on the perikarya of sensory neurons in the HSV-1-infected neurons in ipsilateral trigeminal ganglia. Antibodies have been shown to be effective against many neurotropic viruses, often in the absence of obvious cell damage. Observations from experimental HSV infections suggest that antibodies could act in part by interfering with virus expression in the ganglia and/or with axonal spread. The present results provide morphological evidence of the localization of antiviral antibodies at anatomical sites relevant to such putative antibody-mediated protective actions and suggest that viral glycoproteins are accessible to antibodies on infected nerve fibers and sensory neurons.

Kinetics of cytokine production in the cornea and trigeminal ganglion of C57BL/6 mice after corneal HSV-1 infection

To investigate the role of cytokines in the pathogenesis of acute herpetic keratitis (HK), we examined the kinetics of cytokine expression in the corneas and the trigeminal ganglia (TG) of C57BL/6Cr (B6) mice after herpes simplex virus type 1 (HSV-1) infection and observed the influence of the targeted disruption of interferon-gamma (IFN-gamma) gene on the clinical course of HK and/or viral clearance. Following corneal infection with HSV-1 Amakata strain, all corneas developed a typical dendritic keratitis. Quantitative analysis using enzyme-linked immunosorbent assay (ELISA) revealed that the expression of interleukin-1alpha (IL-1alpha), IL-5, IL-6, and IFN-gamma in corneas and TGs significantly elevated immediately after infection, peaked between days 2 and 7 postinfection (p.i.), and then diminished. One exception was IFN-gamma, whose expression significantly persisted in the TGs until day 30 p.i. An additional experiment using IFN-gamma-/- (gko) mice revealed that there was no significant difference in the peak level of viral replication in corneas and TGs between gko and B6 mice, although gko mice showed a significant delay of virus clearance in both corneas and TGs (p < 0.005) and higher mortality rate than B6 mice after HSV-1 infection (p < 0.01). These data suggest that the production of proinflammatory cytokines closely correlates with the pathogenesis of HK, and that IFN-gamma plays an important role in enhancing viral clearance from the cornea and TG.

Resistance to herpetic stromal keratitis in immunized B-cell-deficient mice

This study evaluates the role of antibody as an indicator of immunity to ocular challenge with herpes simplex virus (HSV). Two genotypes of mice, BALB/c or BALB/c with mu-chain knockout (muK/O; which lack functional B cells), were immunized systemically either with nonvirulent infectious virus or with a eukaryotic expression plasmid encoding glycoprotein B (gB). Whereas naive muK/O mice were 10- to 100-fold more susceptible to HSV infection than BALB/c mice, following immunization both groups showed similar levels of resistance to ocular challenge. Thus both HSV-immunized groups cleared virus within 3 days and showed no signs of ocular lesions. gB DNA-immunized mice cleared virus less rapidly (5 days), and the incidence of lesions was 10 and 25% in BALB/c and muK/O mice, respectively. Since muK/O mice failed to produce detectable anti-HSV antibody, the mechanism of rapid viral removal was assumed to have a T cell basis. However, T cells would likely not mediate any protection directly since such cells were absent in infected corneas during clearance. A likely mechanism of immunity could involve innate defenses, perhaps enhanced by the action of cytokines released from antigen-reactive CD4+ cells in vascularized tissue adjacent to the cornea. Thus an abrupt inflammatory response consisting principally of neutrophils occurred in the corneal stroma in immune mice, and this subsided when virus disappeared. These data reveal that even though the deficiency in generating antibody renders mice more susceptible to HSV infection, once primed, resistance to disease expression is mediated solely by the cellular components and their products.

Protective antibody therapy is associated with reduced chemokine transcripts in herpes simplex virus type 1 corneal infection

Herpes simplex virus type 1 (HSV-1) infection on the murine cornea induces an intense inflammatory response which can lead to blindness. This disease, known as herpes stromal keratitis, can be prevented by the timely passive transfer of monoclonal antibody specific for viral glycoprotein D (gD). Precisely how antibody treatment prevents excessive corneal inflammation is not known. In this study we investigated whether chemokine mRNA expression is inhibited by antibody treatment. Total cellular RNAs isolated from normal corneas and at various times after virus infection were analyzed via reverse transcription-PCR for mRNA coding for seven different chemokines. Constitutive levels of IP-10, KC, MIP-2, MCP-1, MIP-1 beta, and RANTES mRNA were detected in uninfected corneas of BALB/c mice. When the cornea was mechanically traumatized, message for all six chemokines was transiently elevated above constitutive levels. In contrast, HSV-1 infection resulted in prolonged enhanced chemokine message expression. The kinetics of mRNA accumulation was distinctive for each chemokine analyzed. MIP-1 alpha message, not detected constitutively, was not evident until day 7 postinfection. Administration of anti-HSV gD monoclonal antibody 1 day after infection was associated with reduced message for MIP-2, MCP-1, MIP-1 alpha, and MIP-1 beta. IP-10, KC, and RANTES messages were not altered. Collectively, our results suggest that anti-gD treatment may protect, at least in part, by inhibiting production of chemokines believed to promote inflammation.

Neutrophil-mediated suppression of virus replication after herpes simplex virus type 1 infection of the murine cornea

Herpes simplex virus type 1 (HSV-1) infection of the murine cornea induces the rapid infiltration of neutrophils. We investigated whether these cells could influence virus replication. BALB/c mice treated with monoclonal antibody (MAb) RB6-8C5 experienced a profound depletion of neutrophils in the bloodstream, spleen, and cornea. In these animals, virus titers in the eye were significantly higher than those in the immunoglobulin G-treated controls at 3 days postinfection. By day 9, virus was no longer detectable in the controls, whereas titers of 10(3) to 10(6) PFU were still present in the neutrophil-depleted hosts. Furthermore, virus spread more readily to the skin and brains of MAb RB6-8C5-treated animals, rendering them significantly more susceptible to HSV-1-induced blepharitis and encephalitis. Only 25% of the treated animals survived, whereas all of the controls lived. Although MAb RB6-8C5 treatment did not alter the CD4+ T-cell, B-cell, natural killer cell, or macrophage populations, the CD8+ T-cell population was partially reduced. Therefore, the experiments were repeated in severe combined immunodeficiency mice, which lack CD8+ T cells. Again virus growth was found to be significantly elevated in the eyes, trigeminal ganglia, and brains of the MAb RB6-8C5-treated hosts. These results strongly indicate that in both immunocompetent and immunodeficient mice, neutrophils play a significant role in helping to control the replication and spread of HSV-1 after corneal infection.

Immunisation against HSV-1 keratitis with a synthetic gD peptide

The authors tested the protective efficacy of, and the immune response to, immunisation with a synthetic peptide of glycoprotein D (gD) of HSV-1 in a murine model of herpes stromal keratitis (HSK). HSV-1 susceptible A/J mice were immunised subcutaneously with a peptide corresponding to the N-terminal epitope gD(5-23) prior to corneal HSV-1 challenge. Divergent immunisation protocols were compared for their protective potency, their ability to prevent the establishment of latency in the trigeminal ganglion, and their effect on the immune system. Low dosages (31 micrograms) of gD(5-23) protected against encephalitis and HSK. Protective efficacy was higher when gD(5-23) was coupled to the carrier protein keyhole limpet haemocyanin (KLH) and was emulsified with adjuvant. Latent infection was found in all control mice but in only 50-75% of immunised mice. The most potent protection was correlated with anti-HSV-1 neutralising antibodies of IgG1 and IgG2a isotypes, but free gD(5-23) protected in the absence of anti-HSV-1 antibodies. Our results suggest that immunisation with gD(5-23) stimulates both humoral and cellular immune mechanisms which protect against HSV-1 keratitis.

Diffusion of immunoglobulins into rabbit cornea after subconjunctival injection: experimental demonstration and mathematical model

To determine whether immunoglobulins of the IgG class diffus up to the corneal center after subconjunctival injection, rabbits were injected with fluorescein-isothiocyanate-labeled human IgG. The inoculum diffused from the entire periphery centrepetally towards the corneal center. The progression of the diffusion front slowed down as the distance to the limbus increased. The first increase of fluorescence in the corneal center was observed on day 6. The intensity increased during the following 10 days despite resorption in the corneal periphery due to the flow of IgG from paracentral toward central areas. The diffusion coefficient of 0.003-0.004 cm2/day was calculated by computer simulation using Fickian diffusion equations adapted for corneal geometry. We conclude that after subconjunctival application, IgG diffuses up to the corneal center with a delay of several days and that the penetration speed decreases as the distance to the limbus increases. This kinetics contributes to our understanding of the role of IgG in corneal pathology and may help to design therapeutic schedules for immunotherapy with IgG.

Protective effects of anti-glycoprotein D monoclonal antibodies in murine herpetic keratitis

The protective effects of passive immunization with two kinds of anti-glycoprotein D (anti-gD) monoclonal antibodies, having different antiviral activities, were investigated in murine herpetic keratitis. One monoclonal antibody, designated M1, had high virus-neutralizing antibody titers, along with undetectable levels of complement-dependent cytolysis (CDC) and antibody-dependent cellular cytotoxicity (ADCC); the other, designated M12, exhibited extremely low titers of virus-neutralization with high level of CDC and ADCC. When systemically administered 24 hours prior to virus inoculation to the cornea, both M1 and M12 almost completely prevented the development of stromal keratitis. The protective efficacy of both was observed to be dose-dependent. Pepsin-treated M1 retained its efficacy in suppressing stromal keratitis, whereas pepsin-treated M12 did not. When the administration of M1 and M12 were delayed, both provided significant (but less complete) protection, up to 24 hours after virus inoculation. These results suggest that both virus neutralization and CDC/ADCC play an important role in preventing virus growth in the corneal stroma during the early stage of corneal infection.

Protection from retinal necrosis by passive transfer of monoclonal antibody specific for herpes simplex virus glycoprotein D

Passive administration of antibody against herpes simplex virus type 1 (HSV-1) has been shown to protect against stromal keratitis and death from encephalitis. Although the exact mechanism by which passively-transferred antibody protects is not known, one of the features of protection by passively-transferred antibody is interference with the ability of the virus to spread within the nervous system. In the experiments reported herein, studies were performed to determine if 8D2, a monoclonal antibody against a type-common epitope of glycoprotein D, could protect mice from retinal necrosis following uniocular anterior chamber inoculation of HSV-1. Mice were protected from retinal necrosis when the antibody was administered 2 hours before virus inoculation or 24 hours after virus inoculation. When antibody was injected 2 hours before virus inoculation, the titer of virus at day 1 p.i. in the injected eyes of antibody-treated and control mice was the same, but by 3 days p.i., the titer of virus in the antibody-treated mice was significantly lower than that recovered from control mice. The titers of virus in the brains and in the uninoculated eyes of antibody-treated mice were also significantly lower than in control mice. The results of these studies suggest that passively-transferred antibody protects against retinal necrosis by limiting spread of virus to the CNS or replication of virus within the CNS.

Anti-glycoprotein D monoclonal antibody protects against herpes simplex virus type 1-induced diseases in mice functionally depleted of selected T-cell subsets or asialo GM1+ cells

Passive transfer of a monoclonal antibody (MAb) specific for glycoprotein D (gD) is highly effective in preventing the development of herpes simplex virus type 1-induced stromal keratitis. In the present study, we investigated whether animals which had been functionally depleted of T-cell subsets or asialo GM1+ cells would continue to be responsive to MAb therapy. BALB/c mice were depleted of CD4+, CD8+, or asialo GM1+ cells by treatment with anti-L3T4, anti-Lyt 2.2, or anti-asialo GM1 antibodies, respectively. Functional depletion of CD4+ cells was documented by the loss of delayed-type hypersensitivity responsiveness, while CD8+ cell depletion was accompanied by abrogation of cytotoxic lymphocyte activity. Anti-asialo GM1 treatment led to the loss of natural killer cell lytic activity. Mice depleted of the desired cell population and infected on the scarified cornea with herpes simplex virus type 1 uniformly developed necrotizing stromal keratitis by 3 weeks postinfection. A single inoculation of anti-gD MAb (55 micrograms) given intraperitoneally 24 h postinfection strongly protected hosts depleted of CD4+ cells against stromal keratitis. Likewise, antibody treatment in CD8+ or asialo GM1+ cell-depleted hosts was as therapeutically effective as that seen in non-cell-depleted mice. We also observed that in cell-depleted mice, the virus spread into the central nervous system and caused encephalitis. The CD4+ cell-depleted mice were the most severely affected, as 100% developed fatal disease. Anti-gD MAb treatment successfully protected all (32 of 32) CD4+-, CD8+-, or asialo GM1(+)-depleted hosts against encephalitis. We therefore conclude that antibody-mediated prevention of stromal keratitis and encephalitis does not require the obligatory participation of CD4+, CD8+, or asialo GM1+ cells. However, when mice were simultaneously depleted of both CD4+ and CD8+ T-cell subsets, antibody treatment could not prevent fatal encephalitis. Thus, antibody can compensate for the functional loss of one but not two T-lymphocyte subpopulations.

Humanized antibodies for antiviral therapy

Antibody therapy holds great promise for the treatment of cancer, autoimmune disorders, and viral infections. Murine monoclonal antibodies are relatively easy to produce but are severely restricted for therapeutic use by their immunogenicity in humans. Production of human monoclonal antibodies has been problematic. Humanized antibodies can be generated by introducing the six hypervariable regions from the heavy and light chains of a murine antibody into a human framework sequence and combining it with human constant regions. We humanized, with the aid of computer modeling, two murine monoclonal antibodies against herpes simplex virus gB and gD glycoproteins. The binding, virus neutralization, and cell protection results all indicate that both humanized antibodies have retained the binding activities and the biological properties of the murine monoclonal antibodies.

Herpes simplex keratitis: role of viral infection versus immune response

The cumulative clinical and experimental data regarding the role of viral infection versus the immune response in the pathogenesis of herpes simplex stromal keratitis and central disciform endotheliitis are discussed. Ultrastructural and viral isolation studies have been performed in only a limited number of cases of human stromal keratitis and disciform endotheliitis. Virus has been isolated from the minority of corneas cultured, whereas viral particles have been demonstrated in selected cases of stromal keratitis, most of which had been treated with steroids at some point in time. The possibility of corneal latency in cases of quiescent herpetic stromal keratitis will require further systematic study. Review of the experimental and clinical findings suggests a dialectical role of the immune response in limiting viral infection, while contributing to corneal opacification and scar formation.

External ocular herpesvirus infections in immunodeficiency

Infections of the eye with members of the herpes family of viruses (e.g. HSV, CMV, VZV) are frequent manifestations of acquired and inherited defects in cell mediated immunity. Herpesvirus infections in the immunocompromised may reflect frequent viral reactivation from the latent state, as well as extensive productive infection of ocular structures following reactivation or primary infection. A review of experimental and clinical studies of both acquired and inherited immune dysfunction implicates specific immune mechanisms influencing the establishment of latency, viral reactivation and the control of active viral replication in ocular tissues.

Evidence endogenous interferon production contributed to the lack of ocular virulence of an HSV intertypic recombinant

An intertypic recombinant isolated from rabbit kidney cells following co-transfection of HSV-1(17) and HSV-2(186) DNA failed to induce overt ocular pathology when inoculated onto the murine sacrificed cornea at concentrations as high as 10(7) PFU per eye. In contrast, both parents induced corneal disease at a 1000-fold lower dose. The reason(s) for the failure of the intertypic recombinant, designated RO25X, to induce corneal pathology was investigated. It was found that the recombinant was 100-fold more sensitive to the inhibitory effects of interferon (IFN) alpha/beta than the parent strains in corneal button growth studies in vitro. R025X readily grew in cultured mouse corneal fibroblasts at a low multiplicity of infection. However, the peak titer was approximately 8-fold lower than that of strain 17. Addition of rabbit anti-IFN alpha/beta to the culture medium resulted in a 4 to 5-fold increase in infectious titer compared to its growth in the absence of antiserum. Most significantly, when mice were pre-treated in vivo with anti-IFN alpha/beta 24 hours prior to virus corneal infection, 67% of the recipients developed moderate to severe stromal keratitis, whereas none of the controls developed corneal pathology. Blepharitis was also significantly increased in incidence and severity in the antiserum treated hosts. We conclude that the inability of R025X to induce ocular disease was due, at least in part, to the inhibitory effects of interferon produced in response to infection.

Ocular avirulence of a herpes simplex virus type 1 strain is associated with heightened sensitivity to alpha/beta interferon

BALB/c mice infected on the scarified cornea with herpes simplex virus type 1 strain 35 [HSV-1(35)] rarely developed ocular disease even at challenge doses as high as 10(7) PFU per eye. In contrast, HSV-1(RE) consistently induced stromal keratitis at an inoculum of 2 x 10(4) PFU. The goal of this study was to determine the reason for the difference in virulence between the two HSV strains. Both HSV-1 strains replicated to similar titers in excised corneal "buttons." However, after in vivo infection of the cornea, the growth of strain 35 was evident only during the first 24 h postinfection, whereas the replication of strain RE persisted for at least 4 days. In vitro tests revealed that HSV-1(35) was greater than 10 times more sensitive to alpha/beta interferon (IFN-alpha/beta) than HSV-1(RE). Both strains induced comparable serum levels of IFN after intraperitoneal inoculation. The kinetics of HSV-1(35) clearance from the eye was markedly altered by treatment with rabbit anti-IFN-alpha/beta. Virus titers exceeding 10(4) PFU per eye could be demonstrated 4 to 5 days postinfection in mice given a single inoculation of antiserum 1 h after infection. Furthermore, anti-IFN treatment in 3-week-old mice infected with HSV-1(35) led to the development of clinically apparent corneal disease which subsequently progressed to stromal keratitis in the majority of recipients. These results indicate that the striking difference in the capacity of HSV-1(35) and HSV-1(RE) to induce corneal disease was related to the inherently greater sensitivity of strain 35 to IFN-alpha/beta produced by the host in response to infection.

An improved model of recurrent herpetic eye disease in mice

Mice were passively immunized with serum containing antibodies to herpes simplex virus type 1 (HSV-1) before inoculation on the cornea with HSV-1 strain McKrae. After such immunization most mice survived and most had normal eyes. When primary infection had subsided, mice with normal eyes were selected and treated with cyclophosphamide, dexamethasone and UV irradiation of the inoculated eye or UV irradiation alone, to reactivate latent virus. After either treatment mice developed signs of recurrent infection (virus in eyewashings and recurrent corneal and/or lid disease). The incidence of such signs was 17/33 (52%) in mice receiving immunosuppressive drugs and UV irradiation and 19/32 (59%) in mice given UV irradiation alone. In mice treated with either stimulus dendritic or geographic ulceration of the cornea was seen. These closely resembled the herpetic lesions seen in humans. There was good correlation between the pattern and distribution of recurrent corneal disease and the distribution of cells containing virus antigens in corneal epithelial sheets. Again, as in humans, the induction of recurrent infection was found to correlate poorly with a rise in the level of serum neutralizing antibody. In mice treated with UV irradiation alone corneal ulcers healed and the eyes returned to normal. By contrast, in mice given immunosuppressive drugs and UV irradiation, the ulceration became more severe and the eyes became opaque and vascularized. The use of passive immunization has greatly improved our previously reported model of recurrent herpetic eye disease since it has increased the incidence of mice suitable for the induction of recurrent infection and has increased the incidence of such infection.

Quantitation of purified monoclonal antibody needed to prevent HSV-1 induced stromal keratitis in mice

A purified IgG2a monoclonal antibody with a neutralizing titer of 10(4) and specificity for gD was evaluated for its therapeutic potential in a murine ocular infection model. BALB/c mice, infected on the scarified cornea with 10 times the HSV-1 strain RE concentration needed to produce severe and persistent stromal opacity, were given a single inoculation of antibody intraperitoneally 24 hours later. The animals were then followed for corneal disease development. Antibody, at concentrations as low as 10 micrograms per mouse, was strikingly effective at preventing corneal opacity. Furthermore, the corneas, once clear, remained clear whereas the controls developed +3 to +5 stromal disease which was still present 60 days post-infection. Animals that had been treated and recovered from infection were resistant to subsequent HSV-1 challenge on the opposite cornea. These results demonstrate the therapeutic potential of systemically administered microgram quantities of anti-gD antibody.

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.