Humoral immune response to herpes simplex virus type 2 glycoproteins in patients receiving a glycoprotein subunit vaccine

An Interleukin 12 Adjuvanted Herpes Simplex Virus 2 DNA Vaccine Is More Protective Than a Glycoprotein D Subunit Vaccine in a High-Dose Murine Challenge Model

Vaccination is a proven intervention against human viral diseases; however, success against Herpes Simplex Virus 2 (HSV-2) remains elusive. Most HSV-2 vaccines tested in humans to date contained just one or two immunogens, such as the virion attachment receptor glycoprotein D (gD) and/or the envelope fusion protein, glycoprotein B (gB). At least three factors may have contributed to the failures of subunit-based HSV-2 vaccines. First, immune responses directed against one or two viral antigens may lack sufficient antigenic breadth for efficacy. Second, the antibody responses elicited by these vaccines may have lacked necessary Fc-mediated effector functions. Third, these subunit vaccines may not have generated necessary protective cellular immune responses. We hypothesized that a polyvalent combination of HSV-2 antigens expressed from a DNA vaccine with an adjuvant that polarizes immune responses toward a T helper 1 (Th1) phenotype would compose a more effective vaccine. We demonstrate that delivery of DNA expressing full-length HSV-2 glycoprotein immunogens by electroporation with the adjuvant interleukin 12 (IL-12) generates substantially greater protection against a high-dose HSV-2 vaginal challenge than a recombinant gD subunit vaccine adjuvanted with alum and monophosphoryl lipid A (MPL). Our results further show that DNA vaccines targeting optimal combinations of surface glycoproteins provide better protection than gD alone and provide similar survival benefits and disease symptom reductions compared with a potent live attenuated HSV-2 0ΔNLS vaccine, but that mice vaccinated with HSV-2 0ΔNLS clear the virus much faster. Together, our data indicate that adjuvanted multivalent DNA vaccines hold promise for an effective HSV-2 vaccine, but that further improvements may be required.

A novel HSV-2 subunit vaccine induces GLA-dependent CD4 and CD8 T cell responses and protective immunity in mice and guinea pigs

BACKGROUND/OBJECTIVES

There is currently no licensed prophylactic or therapeutic vaccine for HSV-2 infection.

METHODS

We developed a novel preclinical vaccine candidate, G103, consisting of three recombinantly expressed HSV-2 proteins (gD and the UL19 and UL25 gene products) adjuvanted with the potent synthetic TLR4 agonist glucopyranosyl lipid A (GLA) formulated in stable emulsion. The vaccine was tested for immunogenicity and efficacy in pre-clinical models for preventative and therapeutic vaccination.

RESULTS

Vaccination of mice with G103 elicited antigen-specific binding and neutralizing antibody responses, as well as robust CD4 and CD8 effector and memory T cells. The T cell responses were further boosted by subsequent challenge with live virus. Prophylactic immunization completely protected against lethal intravaginal HSV-2 infection in mice, with only transient replication of virus in the genital mucosa and sterilizing immunity in dorsal root ganglia. Supporting the use of G103 therapeutically, the vaccine expanded both CD4 and CD8 T cells induced in mice by previous infection with HSV-2. In the guinea pig model of recurrent HSV-2 infection, therapeutic immunization with G103 was approximately 50% effective in reducing the number of lesions per animal as well as the overall lesions score.

CONCLUSIONS

Taken together, the data show that G103 is a viable candidate for development of a novel prophylactic and therapeutic HSV-2 vaccine.

Herpes simplex virus 2 (HSV-2) infected cell proteins are among the most dominant antigens of a live-attenuated HSV-2 vaccine

Virion glycoproteins such as glycoprotein D (gD) are believed to be the dominant antigens of herpes simplex virus 2 (HSV-2). We have observed that mice immunized with a live HSV-2 ICP0^- mutant virus, HSV-2 0ΔNLS, are 10 to 100 times better protected against genital herpes than mice immunized with a HSV-2 gD subunit vaccine (PLoS ONE 6:e17748). In light of these results, we sought to determine which viral proteins were the dominant antibody-generators (antigens) of the live HSV-2 0ΔNLS vaccine. Western blot analyses indicated the live HSV-2 0ΔNLS vaccine elicited an IgG antibody response against 9 or more viral proteins. Many antibodies were directed against infected-cell proteins of >100 kDa in size, and only 10 ± 5% of antibodies were directed against gD. Immunoprecipitation (IP) of total HSV-2 antigen with 0ΔNLS antiserum pulled down 19 viral proteins. Mass spectrometry suggested 44% of immunoprecipitated viral peptides were derived from two HSV-2 infected cells proteins, RR-1 and ICP8, whereas only 14% of immunoprecipitated peptides were derived from HSV-2’s thirteen glycoproteins. Collectively, the results suggest the immune response to the live HSV-2 0ΔNLS vaccine includes antibodies specific for infected cell proteins, capsid proteins, tegument proteins, and glycoproteins. This increased breadth of antibody-generating proteins may contribute to the live HSV-2 vaccine’s capacity to elicit superior protection against genital herpes relative to a gD subunit vaccine.

Antigenic breadth: a missing ingredient in HSV-2 subunit vaccines?

The successful human papillomavirus and hepatitis B virus subunit vaccines contain single viral proteins that represent 22 and 12%, respectively, of the antigens encoded by these tiny viruses. The herpes simplex virus 2 (HSV-2) genome is >20 times larger. Thus, a single protein subunit represents 1% of HSV-2's total antigenic breadth. Antigenic breadth may explain why HSV-2 glycoprotein subunit vaccines have failed in clinical trials, and why live HSV-2 vaccines that express 99% of HSV-2's proteome may be more effective. I review the mounting evidence that live HSV-2 vaccines offer a greater opportunity to stop the spread of genital herpes, and I consider the unfounded 'safety concerns' that have kept live HSV-2 vaccines out of U.S. clinical trials for 25 years.

HSV-2 vaccine: current state and insights into development of a vaccine that targets genital mucosal protection

HSV-2 is one of the most prevalent sexually transmitted infections that result in significant morbidity and financial burden on health systems around the world. Recurrent and asymptomatic re-activation accompanied by viral shedding is common among sero-positive individuals, leading to relatively high efficiency of transmission. Prophylactic HSV-2 vaccines are the best and cheapest option to address the problems associated with HSV-2 infections globally. However, despite persistent efforts, the search for an efficacious vaccine for HSV-2 remains elusive. In this review, the current state of HSV-2 vaccines and the outcome of past human trials are examined. Furthermore, we discuss the evidence and strategies from experimental mouse models that have been successful in inducing protective immunity in the genital tract against HSV-2, following immunization. Future vaccination strategies that focus on induction of robust mucosal immunity in the genital tract may hold the key for a successful vaccine against HSV-2.

Recent progress in herpes simplex virus immunobiology and vaccine research

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) cause prevalent, chronic infections that have serious outcomes in some individuals. Neonatal herpes may occur when the infant traverses the cervix during maternal genital herpes. Genital herpes is a major risk factor for human immunodeficiency virus type 1 transmission. Considerable efforts have been made to design and test vaccines for HSV, focusing on genital infection with HSV-2. Several protein subunit vaccines based on HSV-2 envelope glycoproteins have reached advanced-phase clinical trials. These antigens were chosen because they are the targets of neutralizing-antibody responses and because they elicit cellular immunity. Encouraging results have been reported in studies of treatment of HSV-seronegative women with a vaccine consisting of truncated glycoprotein D of HSV-2 and a novel adjuvant. Because most sexual HSV transmission occurs during asymptomatic shedding, it is important to evaluate the impact of vaccination on HSV-2 infection, clinically apparent genital herpes, and HSV shedding among vaccine recipients who acquire infection. There are several other attractive formats, including subunit vaccines that target cellular immune responses, live attenuated virus strains, and mutant strains that undergo incomplete lytic replication. HSV vaccines have also been evaluated for the immunotherapy of established HSV infection.

Current recommendations for the treatment of genital herpes

The incidence of genital herpes continues to increase in epidemic-like fashion. Aciclovir (acyclovir) has been the original gold standard of therapy. The recent addition of famciclovir and valaciclovir as antiherpes drugs has improved convenience as well as the efficacy of treatment. Although aciclovir remains a widely prescribed and reliable drug, its administration schedule falls short of the ease of usage that the newer nucleoside analogues offer, for both episodic and suppressive therapy. Suppression of symptomatic disease and asymptomatic shedding from the genitalia have both become popular approaches, if not the primary targets of antiviral therapy. Knowing that asymptomatic disease leads to most cases of transmission strongly suggests that suppression with antiviral agents could reduce transmission risk in discordant couples. Unfortunately, the role for antivirals in reducing transmission remains to be proven in clinical trials. Neonatal herpes is now successfully treated using aciclovir. Current randomised clinical trials are examining aciclovir and valaciclovir administration, as well as safety and efficacy for post-acute suppressive therapy. Prevention of recurrences in pregnancy is also a topic under investigation, with a view to reducing the medical need for Cesarean section, or alternatively (and far less likely to be accomplished) to protect the neonate. Although resistance is largely limited to the immunocompromised and a change in resistance patterns is not expected, several drugs are available for the treatment of aciclovir-resistant strains of herpes simplex. Foscarnet is the main alternative with proven efficacy in this setting. Unfortunately, administration of foscarnet requires intravenous therapy, although a single anecdote of topical foscarnet efficacy in this setting has been published. Alternatives include cidofovir gel, which is not commercially available but can be formulated locally from the intravenous preparation. Less effective alternatives include trifluridine and interferon. Future possibilities for treatment of genital herpes include a microparticle-based controlled-release formulation of aciclovir and resiquimod (VML-600; R-848). The search for an effective therapeutic vaccine for genital herpes has not been successful to date, although a live virus glycoprotein H-deficient (DISC) vaccine is currently in clinical trials. Recent data suggest that seronegative women are protected (albeit, not fully) by a glycoprotein D recombinant vaccine with adjuvant. Despite the established safety and convenience of current treatment options, better suppressive options and topical treatment options are much needed. Studies using existing agents as potential tools to avoid Cesarean section, or transmission to neonate or partner are ongoing. Both vaccines and antivirals may eventually play a role in prevention of infection.

Antibody-binding sites on truncated forms of varicella-zoster virus gpI(gE) glycoprotein

Varicella-zoster virus (VZV)-seropositive human sera were shown to be reactive with the truncated VZV gpI(gE) candidate subunit vaccine (TgpI-511). To identify the location of antibody-binding sites (epitopes) on TgpI-511, three truncated forms of TgpI-511 glycoprotein (TgpI-124, TgpI-160, TgpI-316) DNA encoding the N-terminal region of this glycoprotein with amino acid residues of 124, 160 and 360, respectively, were inserted into the vaccinia virus genome. Infection of cells with recombinant vaccinia viruses resulted in the secretion of all three truncated gpI(gE) as well as TgpI-511 from the infected cells. Immunoprecipitation of these truncated glycoproteins with VZV-seropositive human sera and gpI(gE)-specific monoclonal antibodies identified the location of four new antibody-binding sites on the VZV TgpI-511 glycoprotein. In addition, tunicamycin treatment and O-glycanase digestion revealed the presence of both N-linked and O-linked oligosaccharides on TgpI-511. These results revealed the location of new epitopes on VZV TgpI-511 and demonstrated that the epitopes on TgpI-511 were recognized by human sera from VZV-seropositive individuals.

Biochemical characterization of herpes simplex virus type-1-immunostimulating complexes (ISCMOs): a multi-glycoprotein structure

The preparation and characterization of an immunostimulating complex (ISCOM) preparation containing several HSV-1 glycoproteins, including the major glycoproteins B and D is described. The multi-glycoprotein HSV-1 ISCOM preparation was obtained from a gradient-purified aqueous HSV-1 antigen preparation following extraction from infected cells using a zwitterionic detergent. With polyclonal and monoclonal antibodies to HSV-1 glycoproteins in enzyme-linked immunosorbent assay, SDS-polyacrylamide gel electrophoresis and radioimmunoprecipitation techniques, the HSV-1 ISCOM preparation was shown to contain glycoproteins B, C, D, E, H and I, although further, additional proteins were also present. The DNA content of HSV-1 ISCOMs was determined using a 3H-thymidine labelling method. The protein and DNA contents of the HSV-1 ISCOM preparation are discussed with reference to the potentialities of the preparation as a vaccine for use in human beings.

Immunogenicity of herpes simplex virus type 1 glycoproteins expressed in vaccinia virus recombinants

Vaccinia virus recombinants expressing glycoproteins B (vgB11), D (VgD52), E (gE/7.5 and gE/4B), G (gG-vac), H (gH-vac), and I (gI-vac) of HSV-1 were used to compare the protective response to these individual glycoproteins in the mouse. Glycoprotein D induced the best neutralizing antibody titers and the most increased rates of HSV clearance from the ear as well as good protection from the establishment of latent HSV infections in the sensory ganglia. Glycoprotein B also induced good neutralizing antibody titers and as great a protection from the establishment of latency as gD although the rate of virus clearance from the ear was not as great as after immunization with gD. Glycoprotein E induced weak neutralizing antibody but gG, gH, and gI did not show a neutralizing antibody response. At higher challenge doses of virus (10(6) PFU HSV-1 in the ear), gE induced a protective response by increasing the rate of virus clearance and reducing the acute infection of ganglia as compared to negative control immunized mice. However there was no protection from the establishment of latent infections after immunization with gE. No protective response was seen to gG, gH, or gl.

Isolated gA/gB glycoprotein complex of human cytomegalovirus envelope induces humoral and cellular immune-responses in human volunteers

Three human cytomegalovirus (HCMV) seronegative individuals were immunized with a single dose of HCMV envelope; two individuals developed neutralizing antibodies. Two naturally HCMV seropositive and three HCMV seronegative human volunteers were immunized with a major glycoprotein complex, gA/gB, of HCMV that had been purified by immunoadsorbent column chromatography. After a single injection of the gA/gB preparation, the naturally seropositive individuals developed higher titres of neutralizing antibodies and temporarily higher HCMV-specific lymphocyte proliferation (HCMV-LP) responses in vitro. The seronegative individuals developed neutralizing antibodies after the third injection of gA/gB, which were present only transiently, but showed a rapid reappearance and increase in titre after the fourth injection. At 1 year after the first injection, the neutralizing antibody titres were still comparable with those of the naturally seropositive individuals. HCMV-LP responses to HCMV in the initially seronegative individuals developed after the second or third injection with the gA/gB preparation and remained positive during the 1-year observation period. These results show that the gA/gB protein induces both humoral and cellular immune responses in humans, and might serve as the basis of a subunit vaccine.

Sexually transmitted viruses

Human viruses known to be spread by sexual contact include herpes simplex viruses (HSV), papillomaviruses (HPV), human immunodeficiency virus (HIV), hepatitis B virus, and cytomegalovirus. Infections with the first three (HSV, HPV, and HIV) have reached epidemic proportions and pose global health concerns. Most of what we know about these human pathogens has been learned only recently, owing to the advent of DNA technologies and advances in culture techniques. In fact, our awareness of one virally transmitted venereal disease, acquired immunodeficiency syndrome, dates to the early 1980s. This paper touches on various aspects of the biology, pathogenesis, clinical manifestations, and, where applicable, oncogenicity of these agents, as well as current treatments and vaccine initiatives.

Herpes simplex virus (HSV)-specific proliferative and cytotoxic T-cell responses in humans immunized with an HSV type 2 glycoprotein subunit vaccine

Studies were undertaken to determine whether immunization of humans with a herpes simplex virus type 2 (HSV-2) glycoprotein-subunit vaccine would result in the priming of both HSV-specific proliferating cells and cytotoxic T cells. Peripheral blood lymphocytes (PBL) from all eight vaccines studied responded by proliferating after stimulation with HSV-2, HSV-1, and glycoprotein gB-1. The PBL of five of these eight vaccines proliferated following stimulation with gD-2, whereas stimulation with gD-1 resulted in relatively low or no proliferative responses. T-cell clones were generated from HSV-2-stimulated PBL of three vaccinees who demonstrated strong proliferative responses to HSV-1 and HSV-2. Of 12 clones studied in lymphoproliferative assays, 9 were found to be cross-reactive for HSV-1 and HSV-2. Of the approximately 90 T-cell clones isolated, 14 demonstrated HSV-specific cytotoxic activity. Radioimmunoprecipitation-polyacrylamide gel electrophoresis analyses confirmed that the vaccinees had antibodies only to HSV glycoproteins, not to proteins which are absent in the subunit vaccine, indicating that these vaccinees had not become infected with HSV. Immunization of humans with an HSV-2 glycoprotein-subunit vaccine thus results in the priming of T cells that proliferate in response to stimulation with HSV and its glycoproteins and T cells that have cytotoxic activity against HSV-infected cells. Such HSV-specific memory T cells were detected as late as 2 years following the last boost with the subunit vaccine.

Development of an ELISA for detection of antibodies to glycoprotein I of Aujeszky's disease virus: a method for the serological differentiation between infected and vaccinated pigs

A blocking ELISA was developed to distinguish between Aujeszky's disease virus (ADV)-infected and vaccinated pigs, on the basis of presence or absence of serum antibodies to glycoprotein I (gI) of ADV. The gI-ELISA detects antibodies that block the reaction of monoclonal antibodies to one or two epitopes on gI of ADV. The ADV-gI antibody response appeared between one and two weeks post-infection and persisted at a high level for at least seven months. Five of the nine ADV-vaccine strains examined were found to be "gI-negative". Pigs vaccinated with a gI-negative vaccine did not develop an ADV-gI antibody response until they were challenge-exposed to a virulent strain of ADV. The gI-ELISA is highly specific, sensitive and suitable for large-scale sero-epidemiological studies to identify infected pigs in populations vaccinated with gI-negative vaccines. The gI-ELISA provides, therefore, a basis for ADV-eradication programmes, which introduces a novel concept in the control of animal virus diseases.

Zwitterionic detergent solubilisation of HSV-1 surface antigens

A preparation was obtained from herpes simplex virus type 1 (HSV-1)-infected cells using a zwitterionic detergent, Empigen BB. The preparation was partially-purified either by ultracentrifugation over a cusion of 20% sucrose or on a sucrose density gradient. Partial characterisation of these materials by ELISA, using both polyclonal and monoclonal antibodies showed them to contain at least four major HSV glycoproteins, gB, gC, gD and gE. Comparison of Empigen-extracted HSV-1 antigen preparations with preparations obtained using the non-ionic detergents Nonidet P40 or Triton-X-100 indicate that, using conventional procedures, separation of glycoproteins, B, C, D, and E from unwanted proteins may be facilitated using the former detergent. Immunization of mice with Empigen-extracted, partially-purified or gradient-purified antigen preparations elicited good levels of antibody detectable by ELISA and a high degree of protection against both HSV-1 and HSV-2 challenge infection. Such protection could be achieved using aqueous antigen preparations, but was augmented using aluminium hydroxide gel as an adjuvant. In general, Empigen-extracted HSV-1 antigen preparations elicited higher ELISA antibody levels and more complete protection against HSV challenge infection than NP40 or Triton-X-100-extracted preparations. The value and usefulness of the detergent Empigen for obtaining HSV surface antigen preparations and the role of these as potential vaccines against HSV infections, is discussed.

The use of lectin affinity columns for selection of precursor or fully glycosylated forms of glycoprotein gD1 of herpes simplex virus type 1

Several lectins were examined for their ability to bind to the glycoprotein gD1 polypeptide from Vero cells infected by herpes simplex virus type 1 (HVS-1), strain KOS. At least four distinct forms of gD1 (1, 2, 3 and 4), ranging in size from 59K to 52K, were resolved by SDS-10% polyacrylamide gel electrophoresis. Wheat germ agglutinin (WGA) did not bind to any of these forms, suggesting that if any sialic residues are present in the carbohydrate moieties of gD1, they are not available for binding to WGA. The entire population of forms 1 and 2 (approximately 59K) bound to castor bean-120 (CB-120) lectin affinity columns, suggesting the presence of terminal galactose residues on the mature and more fully glycosylated carbohydrate moieties of gD1. The forms 3 and 4, representing precursor gD1 molecules, did not bind. The majority of forms 2 and 4, and a portion of form 3 bound to lentil lectin, suggesting the presence of fucose and alpha-linked mannosyl residues on these molecules. A gD1-specific, high molecular weight species (120-125K) was detected in the lentil lectin-binding fraction but not in the fraction bound to CB-120 lectin or in the original infected-cell extract. The results indicated that lectin affinity chromatography, using lentil and CB-120 lectins, is useful as an initial step for the selection and purification of the individual glycosylated forms of gD1.

Difference between herpes simplex virus type 1 and type 2 neonatal encephalitis in neurological outcome

24 infants consecutively treated with acyclovir or vidarabine for neonatal herpes simplex virus (HSV) encephalitis were followed up for 6 months to 3 years to assess neurological and developmental outcome. 15 patients had HSV-2 and 9 had HSV-1 encephalitis. Infants with HSV-2 encephalitis presented with a higher frequency of seizures, greater pleocytosis and protein concentrations in the cerebrospinal fluid, and more frequent evidence of structural damage on computerised tomographic scans of the brain than did those with HSV-1 encephalitis. 1 patient died. All 9 HSV-1 patients were normal at follow-up (mean 19.4 months) compared with only 4 (23%) of the 14 surviving HSV-2 infected infants (p = 0.003). Among infants with HSV-2 encephalitis, 50% became microcephalic; 57% had seizure disorders; 64% had ophthalmological defects; 64% had cerebral palsy; and 57% had mental retardation. Infants with neonatal HSV-1 encephalitis treated with systemic antiviral chemotherapy have excellent neurological outcomes; the neurological morbidity of those with HSV-2 encephalitis is still high.

Comments on vaccines, August 1987

Because of latency and infectious recurrences, eradication of herpes simplex and herpes zoster from the world by vaccines is likely to be much more difficult to accomplish than eradication of smallpox. For some time we may have to settle for control of these diseases rather than their eradication. The live, attenuated varicella vaccine protects immunocompromised and normal persons against clinical chickenpox but it does not completely prevent subsequent infection with natural chickenpox virus or latency. With herpes simplex vaccines we may have to be satisfied with amelioration or control of clinical infections and diminution of latency and recurrent disease. Varicella zoster immune globulin plays a useful role in attenuation of varicella in immunocompromised or special-risk persons exposed to varicella zoster virus. Passive immunization for herpes simplex (herpes simplex immune globulin or other antibody preparations) has been studied very little. Maybe passive immunization will have a place in future therapies, especially for serious herpes simplex virus infections in immunocompromised hosts.

Detection of asymptomatic herpes simplex virus infections after vaccination

Twenty-two volunteers seronegative for antibodies to herpes simplex virus (HSV) were enrolled in a trial to determine tolerance and immunogenicity of an HSV-2 glycoprotein subunit vaccine. Vaccine was administered at days 0, 28, and 140, and sera were obtained on days 0, 7, 14, 21, 28, 35, 49, 56, 140, 147, and 365 for determination of HSV neutralizing antibody activity and antibody-dependent cell cytotoxicity (ADCC). Sera were also tested by immunoprecipitation of radiolabeled HSV-2-infected cell proteins and polyacrylamide gel electrophoresis to identify the viral proteins which elicited antibody responses in vaccine recipients. After vaccination two male volunteers presented with atypical first-episode genital herpes: patient 1 with a culture-negative genital lesion at day 53 and patient 3 with urethritis at day 68. Seroconversion to wild-type viral proteins not present in the vaccine was detectable by radioimmunoprecipitation-polyacrylamide gel electrophoresis within 10 days in both patients. Two additional volunteers, one a sex contact of patient 1, seroconverted asymptomatically to nonvaccine proteins during the trial. All four vaccine breakthrough patients were indistinguishable from the other volunteers in the time required to develop neutralizing and ADCC antibodies, in the titer of these antibodies, and the time to seroconversion to gB and gD vaccine proteins. However, only one of the four breakthrough patients had antibodies to g80 (a complex of gC-2 and gE) after vaccination as compared with 15 of the other 18 volunteers (P = 0.05). Neither neutralizing antibody nor ADCC titers consistently identified acquisition of wild-type viral infection; therefore, protein-specific serologies were required to detect wild-type antibodies in these four patients. These data underscore the importance of using serologic assays which will distinguish naturally acquired infection from the immune response to vaccination.