Glycoprotein-D-adjuvant vaccine to prevent genital herpes

BACKGROUND

An effective prophylactic vaccine would help control the spread of genital herpes.

METHODS

We conducted two double-blind, randomized trials of a herpes simplex virus type 2 (HSV-2) glycoprotein-D-subunit vaccine with alum and 3-O-deacylated-monophosphoryl lipid A in subjects whose regular sexual partners had a history of genital herpes. In Study 1, subjects were seronegative for herpes simplex virus type 1 (HSV-1) and HSV-2; in Study 2, subjects were of any HSV serologic status. At months 0, 1, and 6, subjects received either vaccine or a control injection and were evaluated for 19 months. The primary end point was the occurrence of genital herpes disease in all subjects in Study 1 and in HSV-2-seronegative female subjects in Study 2.

RESULTS

A total of 847 subjects who were seronegative for both HSV-1 and HSV-2 (268 of them women, in Study 1) and 1867 subjects who were seronegative for HSV-2 (710 of them women, in Study 2) underwent randomization and received injections. Vaccination was well tolerated and elicited humoral and cellular responses. Overall, the efficacy of the vaccine was 38 percent in Study 1 (95 percent confidence interval, -18 to 68 percent; 15 cases occurred in the vaccine group and 24 in the control group), and efficacy in female subjects was 42 percent in Study 2 (95 percent confidence interval, -31 to 74 percent; 9 cases occurred in the vaccine group and 16 in the control group). In both studies, further analysis showed that the vaccine was efficacious in women who were seronegative for both HSV-1 and HSV-2: efficacy in Study 1 was 73 percent (95 percent confidence interval, 19 to 91 percent; P=0.01), and efficacy in Study 2 was 74 percent (95 percent confidence interval, 9 to 93 percent; P=0.02). It was not efficacious in women who were seropositive for HSV-1 and seronegative for HSV-2 at base line or in men.

CONCLUSIONS

These studies suggest that the glycoprotein D vaccine has efficacy against genital herpes in women who are seronegative for both HSV-1 and HSV-2 at base line but not in those who are seropositive for HSV-1 and seronegative for HSV-2. It had no efficacy in men, regardless of their HSV serologic status.

Efficacy results of a trial of a herpes simplex vaccine

BACKGROUND

Two previous studies of a herpes simplex virus type 2 (HSV-2) subunit vaccine containing glycoprotein D in HSV-discordant couples revealed 73% and 74% efficacy against genital disease in women who were negative for both HSV type 1 (HSV-1) and HSV-2 antibodies. Efficacy was not observed in men or HSV-1 seropositive women.

METHODS

We conducted a randomized, double-blind efficacy field trial involving 8323 women 18 to 30 years of age who were negative for antibodies to HSV-1 and HSV-2. At months 0, 1, and 6, some subjects received the investigational vaccine, consisting of 20 μg of glycoprotein D from HSV-2 with alum and 3-O-deacylated monophosphoryl lipid A as an adjuvant; control subjects received the hepatitis A vaccine, at a dose of 720 enzyme-linked immunosorbent assay (ELISA) units. The primary end point was occurrence of genital herpes disease due to either HSV-1 or HSV-2 from month 2 (1 month after dose 2) through month 20.

RESULTS

The HSV vaccine was associated with an increased risk of local reactions as compared with the control vaccine, and it elicited ELISA and neutralizing antibodies to HSV-2. Overall, the vaccine was not efficacious; vaccine efficacy was 20% (95% confidence interval [CI], -29 to 50) against genital herpes disease. However, efficacy against HSV-1 genital disease was 58% (95% CI, 12 to 80). Vaccine efficacy against HSV-1 infection (with or without disease) was 35% (95% CI, 13 to 52), but efficacy against HSV-2 infection was not observed (-8%; 95% CI, -59 to 26).

CONCLUSIONS

In a study population that was representative of the general population of HSV-1- and HSV-2-seronegative women, the investigational vaccine was effective in preventing HSV-1 genital disease and infection but not in preventing HSV-2 disease or infection. (Funded by the National Institute of Allergy and Infectious Diseases and GlaxoSmithKline; ClinicalTrials.gov number, NCT00057330.).

Viruses transfer the antiviral second messenger cGAMP between cells

Cyclic GMP-AMP synthase (cGAS) detects cytosolic DNA during virus infection and induces an antiviral state. cGAS signals by synthesis of a second messenger, cyclic GMP-AMP (cGAMP), which activates stimulator of interferon genes (STING). We show that cGAMP is incorporated into viral particles, including lentivirus and herpesvirus virions, when these are produced in cGAS-expressing cells. Virions transferred cGAMP to newly infected cells and triggered a STING-dependent antiviral program. These effects were independent of exosomes and viral nucleic acids. Our results reveal a way by which a signal for innate immunity is transferred between cells, potentially accelerating and broadening antiviral responses. Moreover, infection of dendritic cells with cGAMP-loaded lentiviruses enhanced their activation. Loading viral vectors with cGAMP therefore holds promise for vaccine development.

Intranasal immunization with CpG oligodeoxynucleotides as an adjuvant dramatically increases IgA and protection against herpes simplex virus-2 in the genital tract

Development of vaccines capable of preventing the transmission or limiting the severity of sexually transmitted viruses, such as HSV and HIV, will likely be dependent on the induction of potent long-lasting mucosal immune responses in the genital tract. Recently, synthetic oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs were shown to serve as potent adjuvants for the induction of mucosal immune responses. Here, we show that intranasal immunization with CpG ODN, plus recombinant glycoprotein B (rgB) of HSV-1, results in significantly elevated levels of specific anti-gB IgA Abs in vaginal washes that remained high throughout the estrous cycle. Additionally, dramatically elevated numbers of specific IgA Ab-secreting cells were present and persisted in the genital tract in response to intravaginal (IVAG) HSV-2 challenge. HSV-2-specific CTL were observed at moderate levels in the spleens of CpG or non-CpG ODN-immunized mice. In contrast, strong CTL responses were observed locally in the genital tissues of both groups following IVAG HSV-2 challenge. Interestingly, mice immunized intranasally with rgB plus CpG ODN, but not non-CpG ODN, were significantly protected following IVAG HSV-2 challenge. Measurement of virus in protected CpG-immunized mice revealed a log lower level of replication within the first few days after infection. In conclusion, these results indicate that intranasal immunization with CpG ODN plus protein mediates immunity in the female genital tract capable of protecting against a sexually transmitted pathogen.

Role of Herd Immunity in Determining the Effect of Vaccines against Sexually Transmitted Disease

BACKGROUND

Vaccination programs provide both direct protection to those immunized and herd immunity, which is indirect protection of those who remain susceptible, owing to a reduced prevalence of infections.

METHODS

The well-understood impact of vaccination against ubiquitous childhood infections is compared with that of vaccination against sexually transmitted infections (STIs), and theoretical insights are derived from a review of mathematical modeling studies.

RESULTS

Typically, a large fraction of cases of STIs are acquired by those with modest risk, and these cases could be prevented by low-efficacy vaccines. If coverage is good, vaccination of only one sex can protect the other sex. Candidate vaccines against human papillomavirus (HPV) and genital herpes are in the final stages of testing. The former is likely to be highly efficacious for a limited number of disease-causing HPV types, and the latter has provided protection against disease in women who initially were seronegative for both herpes simplex virus (HSV) type 1 and HSV-2, with 73% efficacy. In models, this vaccine had a substantial impact when infectiousness was assumed to be reduced along with incidence of disease.

CONCLUSION

With such vaccines on the horizon, the requirements for vaccine delivery need to be considered, particularly who should be vaccinated and at what age.

The cycle of human herpes simplex virus infection: virus transport and immune control

After infection of skin or mucosa, herpes simplex virus enters the sensory nerve endings and is conveyed by retrograde axonal transport to the dorsal root ganglion, where the virus develops lifelong latency. Intermittent reactivation, which is spontaneous in humans, leads to anterograde transport of virus particles and proteins to the skin or mucosa, where the virus is shed and/or causes disease. Immune control of viral infection and replication occurs at the level of skin or mucosa during initial or recurrent infection and also within the dorsal root ganglion, where immune mechanisms control latency and reactivation. This article examines current views on the mechanisms of retrograde and anterograde transport of the virus in axons and the mechanisms of innate and adaptive immunity that control infection in the skin or mucosa and in the dorsal root ganglion--in particular, the role of interferons, myeloid and plasmacytoid dendritic cells, CD4(+) and CD8(+) T cells, and interferon- gamma and other cytokines, including their significance in the development of vaccines for genital herpes.

CD4+ CD25+ T cells regulate vaccine-generated primary and memory CD8+ T-cell responses against herpes simplex virus type 1

It has become evident that naturally occurring CD25(+) regulatory T cells (T(reg) cells) not only influence self-antigen specific immune response but also dampen foreign antigen specific immunity. This report extends our previous findings by demonstrating that immunity to certain herpes simplex virus (HSV) vaccines is significantly elevated and more effective if T(reg) cell response is curtailed during either primary or recall immunization. The data presented here show that removal of CD25(+) T(reg) cells prior to SSIEFARL-CpG or gB-DNA immunization significantly enhanced the resultant CD8(+) T-cell response to the immunodominant SSIEFARL peptide. The enhanced CD8(+) T-cell reactivity in T(reg) cell-depleted animals was between two- and threefold and evident in both acute and memory stages. Interestingly, removal of CD25(+) T(reg) cells during the memory recall response to plasmid immunization resulted in a twofold increase in CD8(+) T-cell memory pool. Moreover, in the challenge experiments, memory CD8(+) T cells generated with plasmid DNA in the absence of T(reg) cells cleared the virus more effectively compared with control groups. We conclude that CD25(+) T(reg) cells quantitatively as well as qualitatively affect the memory CD8(+) T-cell response generated by gB-DNA vaccination against HSV. However, it remains to be seen if all types of vaccines against HSV are similarly affected by CD25(+) T(reg) cells and if it is possible to devise means of limiting T(reg) cell activity to enhance vaccine efficacy.

Comparative efficacy and immunogenicity of replication-defective, recombinant glycoprotein, and DNA vaccines for herpes simplex virus 2 infections in mice and guinea pigs

Many candidate vaccines are effective in animal models of genital herpes simplex virus type 2 (HSV-2) infection. Among them, clinical trials showed moderate protection from genital disease with recombinant HSV-2 glycoprotein D (gD2) in alum-monophosphoryl lipid A adjuvant only in HSV women seronegative for both HSV-1 and HSV-2, encouraging development of additional vaccine options. Therefore, we undertook direct comparative studies of the prophylactic and therapeutic efficacies and immunogenicities of three different classes of candidate vaccines given in four regimens to two species of animals: recombinant gD2, a plasmid expressing gD2, and dl5-29, a replication-defective strain of HSV-2 with the essential genes UL5 and UL29 deleted. Both dl5-29 and gD2 were highly effective in attenuating acute and recurrent disease and reducing latent viral load, and both were superior to the plasmid vaccine alone or the plasmid vaccine followed by one dose of dl5-29. dl5-29 was also effective in treating established infections. Moreover, latent dl5-29 virus could not be detected by PCR in sacral ganglia from guinea pigs vaccinated intravaginally. Finally, dl5-29 was superior to gD2 in inducing higher neutralizing antibody titers and the more rapid accumulation of HSV-2-specific CD8+ T cells in trigeminal ganglia after challenge with wild-type virus. Given its efficacy, its defectiveness for latency, and its ability to induce rapid, virus-specific CD8(+)-T-cell responses, the dl5-29 vaccine may be a good candidate for early-phase human trials.

Correlate of immune protection against HSV-1 genital disease in vaccinated women

BACKGROUND

Previously we conducted a double-blind controlled, randomized efficacy field trial of gD-2 HSV vaccine adjuvanted with ASO4 in 8323 women. Subjects had been previously selected to be seronegative for HSV-1 and HSV-2. We found that vaccine was 82% protective against HSV-1 genital disease, but offered no significant protection against HSV-2 genital disease.

METHODS

To better understand the results of the efficacy study, post-vaccination anti-gD-2 antibody concentrations from all HSV infected subjects and matched uninfected controls were measured. Three models were used to determine whether thes responses correlated with protection against HSV infection or disease. Similarly, cellular immune responses from a subset of subjects and matched controls were evaluated for a correlation with HSV protection.

RESULTS

Antibodies to gD-2 correlated with protection against HSV-1 infection with higher antibody concentration associated with higher efficacy. Cellular immune responses to gD-2 did not correlate with protection.

CONCLUSIONS

The protection against HSV-1 infection observed in the Herpevac Trial for Women was associated with antibodies directed against the vaccine. Clinical Trials Registration NCT00057330.

Lipopeptide epitopes extended by an N?-palmitoyl-lysine moiety increase uptake and maturation of dendritic cells through a Toll-like receptor-2 pathway and trigger a Th1-dependent protective immunity

Lipopeptides, a form of peptide immunogens, are currently under intense investigation as human vaccines for many infectious pathogens and cancers. However, the cellular and molecular mechanisms of lipopeptide immunogenicity are only partially understood. We have investigated the influence of the lipid content on the immunogenicity of lipopeptides using the herpes simplex virus type 1 (HSV-1) gD(1-23) peptide as a model antigen. Totally synthetic lipopeptides were constructed by covalent attachment to the peptide backbone of either Nepsilon-palmitoyl-lysine (palmitoyl-lipidated peptide, palmitoyl-LP) or cholesterol-lysine (cholesterol-lipidated peptide, cholesterol-LP). Immunization of mice with the palmitoyl-LP, but not with its cholesterol-LP analog, induced a strong T cell-dependent protective immunity against lethal HSV-1 infection. Analysis of cytokine profiles and IgG2a/IgG1 ratios revealed that a dominant Th1-type immune response was stimulated by the palmitoyl-LP, as opposed to a Th2 response generated by its cholesterol-LP analog. The palmitoyl-LP was efficiently taken up in vitro by immature dendritic cells (DC) in a time- and dose-dependent manner, and induced phenotypic maturation and production of pro-inflammatory cytokines by DC. Finally, DC stimulated with the palmitoyl-LP induced antigen-specific T cell responses through the Toll-like receptor-2 pathway. These findings have important implications for the development of effective lipopeptide immunization strategies against infectious pathogens.

A live-attenuated HSV-2 ICP0 virus elicits 10 to 100 times greater protection against genital herpes than a glycoprotein D subunit vaccine

Glycoprotein D (gD-2) is the entry receptor of herpes simplex virus 2 (HSV-2), and is the immunogen in the pharmaceutical industry's lead HSV-2 vaccine candidate. Efforts to prevent genital herpes using gD-2 subunit vaccines have been ongoing for 20 years at a cost in excess of $100 million. To date, gD-2 vaccines have yielded equivocal protection in clinical trials. Therefore, using a small animal model, we sought to determine if a live-attenuated HSV-2 ICP0⁻ virus would elicit better protection against genital herpes than a gD-2 subunit vaccine. Mice immunized with gD-2 and a potent adjuvant (alum+monophosphoryl lipid A) produced high titers of gD-2 antibody. While gD-2-immunized mice possessed significant resistance to HSV-2, only 3 of 45 gD-2-immunized mice survived an overwhelming challenge of the vagina or eyes with wild-type HSV-2 (MS strain). In contrast, 114 of 115 mice immunized with a live HSV-2 ICP0⁻ virus, 0ΔNLS, survived the same HSV-2 MS challenges. Likewise, 0ΔNLS-immunized mice shed an average 125-fold less HSV-2 MS challenge virus per vagina relative to gD-2-immunized mice. In vivo imaging demonstrated that a luciferase-expressing HSV-2 challenge virus failed to establish a detectable infection in 0ΔNLS-immunized mice, whereas the same virus readily infected naïve and gD-2-immunized mice. Collectively, these results suggest that a HSV-2 vaccine might be more likely to prevent genital herpes if it contained a live-attenuated HSV-2 virus rather than a single HSV-2 protein.

Prime-boost immunization with DNA vaccine: mucosal route of administration changes the rules

In this study we assessed prime-boost immunization strategies with a DNA vaccine (gB DNA) and attenuated recombinant vaccinia virus vector (rvacgB), both encoding the gB protein of HSV, for their effectiveness at inducing mucosal as well as systemic immunity to HSV. Confirming the reports of others, systemic priming with gB DNA and systemic boosting with rvacgB were the most effective means of inducing serum Ab and splenic T cell responses. Nevertheless, the systemic prime-boost approach failed to induce detectable humoral or T cell responses at mucosal sites. However, such responses, at both proximal and distal locations, were induced if immunizations, especially the priming dose, were administered mucosally. Curiously, whereas optimal immunity with systemic priming and boosting occurred when gB DNA was used to prime and rvacgB was used as a boost, mucosal responses were optimal when animals were mucosally primed with rvacgB and boosted with gB DNA given mucosally. Furthermore, notable mucosal responses also occurred in animals mucosally primed with rvacgB and subsequently boosted systemically with gB DNA. Because the mucosal prime-boost immunization protocol also induced excellent systemic immune responses, the approach should be useful to vaccinate against agents for which both mucosal and systemic immunity are important for protection.

Modulation of immunity against herpes simplex virus infection via mucosal genetic transfer of plasmid DNA encoding chemokines

In this study, we examined the effects of murine chemokine DNA, as genetic adjuvants given mucosally, on the systemic and distal mucosal immune responses to plasmid DNA encoding gB of herpes simplex virus (HSV) by using the mouse model. The CC chemokines macrophage inflammatory protein 1beta (MIP-1beta) and monocyte chemotactic protein 1 (MCP-1) biased the immunity to the Th2-type pattern as judged by the ratio of immunoglobulin isotypes and interleukin-4 cytokine levels produced by CD4(+) T cells. The CXC chemokine MIP-2 and the CC chemokine MIP-1alpha, however, mounted immune responses of the Th1-type pattern, and such a response rendered recipients more resistant to HSV vaginal infection. In addition, MIP-1alpha appeared to act via the upregulation of antigen-presenting cell (APC) function and the expression of costimulatory molecules (B7-1 and B7-2), whereas MIP-2 enhanced Th1-type CD4(+) T-cell-mediated adaptive immunity by increasing gamma interferon secretion from activated NK cells. Our results emphasize the value of using the mucosal route to administer DNA modulators such as chemokines that function as adjuvants by regulating the activity of innate immunity. Our findings provide new insight into the value of CXC and CC chemokines, which act on different innate cellular components as the linkage signals between innate and adaptive immunity in mucosal DNA vaccination.

A novel HLA (HLA-A*0201) transgenic rabbit model for preclinical evaluation of human CD8+ T cell epitope-based vaccines against ocular herpes

We introduced a novel humanized HLA-A*0201 transgenic (HLA Tg) rabbit model to assess the protective efficacy of a human CD8(+) T cell epitope-based vaccine against primary ocular herpes infection and disease. Each of the three immunodominant human CD8(+) T cell peptide epitopes from HSV-1 glycoprotein D (gD(53-61), gD(70-78), and gD(278-286)) were joined with a promiscuous human CD4(+) T cell peptide epitope (gD(49-82)) to construct three separate pairs of CD4-CD8 peptides. Each CD4-CD8 peptide pair was then covalently linked to an N(epsilon)-palmitoyl-lysine residue via a functional base lysine amino group to construct CD4-CD8 lipopeptides. HLA Tg rabbits were immunized s.c. with a mixture of the three CD4-CD8 HSV-1 gD lipopeptides. The HSV-gD-specific T cell responses induced by the mixture of CD4-CD8 lipopeptide vaccine and the protective efficacy against acute virus replication and ocular disease were determined. Immunization induced HSV-gD(49-82)-specific CD4(+) T cells in draining lymph node (DLN); induced HLA-restricted HSV-gD(53-61), gD(70-78), and gD(278-286)-specific CD8(+) T cells in DLN, conjunctiva, and trigeminal ganglia and reduced HSV-1 replication in tears and corneal eye disease after ocular HSV-1 challenge. In addition, the HSV-1 epitope-specific CD8(+) T cells induced in DLNs, conjunctiva, and the trigeminal ganglia were inversely proportional with corneal disease. The humanized HLA Tg rabbits appeared to be a useful preclinical animal model for investigating the immunogenicity and protective efficacy of human CD8(+) T cell epitope-based prophylactic vaccines against ocular herpes. The relevance of HLA Tg rabbits for future investigation of human CD4-CD8 epitope-based therapeutic vaccines against recurrent HSV-1 is discussed.

Of mice and not humans: how reliable are animal models for evaluation of herpes CD8(+)-T cell-epitopes-based immunotherapeutic vaccine candidates?

Herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2)-specific CD8(+) T cells that reside in sensory ganglia, appear to control recurrent herpetic disease by aborting or reducing spontaneous and sporadic reactivations of latent virus. A reliable animal model is the ultimate key factor to test the efficacy of therapeutic vaccines that boost the level and the quality of sensory ganglia-resident CD8(+) T cells against spontaneous herpes reactivation from sensory neurons, yet its relevance has been often overlooked. Herpes vaccinologists are hesitant about using mouse as a model in pre-clinical development of therapeutic vaccines because they do not adequately mimic spontaneous viral shedding or recurrent symptomatic diseases, as occurs in human. Alternatives to mouse models are rabbits and guinea pigs in which reactivation arise spontaneously with clinical herpetic features relevant to human disease. However, while rabbits and guinea pigs develop spontaneous HSV reactivation and recurrent ocular and genital disease none of them can mount CD8(+) T cell responses specific to Human Leukocyte Antigen- (HLA-)restricted epitopes. In this review, we discuss the advantages and limitations of these animal models and describe a novel "humanized" HLA transgenic rabbit, which shows spontaneous HSV-1 reactivation, recurrent ocular disease and mounts CD8(+) T cell responses to HLA-restricted epitopes. Adequate investments are needed to develop reliable preclinical animal models, such as HLA class I and class II double transgenic rabbits and guinea pigs to balance the ethical and financial concerns associated with the rising number of unsuccessful clinical trials for therapeutic vaccine formulations tested in unreliable mouse models.

Requirement of an integrated immune response for successful neuroattenuated HSV-1 therapy in an intracranial metastatic melanoma model

Neuroattenuated herpes simplex virus ICP34.5 mutants slow progression of preformed tumors and lead to complete regression of some tumors. Although this was previously thought to be due to viral lysis of infected tumor cells, it is now understood that there is an immune component to tumor destruction. We have previously shown that no difference in survival is seen in lymphocyte-depleted mice after viral or mock therapy of syngeneic intracranial melanomas. We have also demonstrated the presence of a wide spectrum of immune cells following viral therapy, including larger percentages of CD4+ T cells and macrophages. In this paper, the contribution of the immune system to tumor destruction has been further delineated. Viral therapy of intracranial melanoma induces a tumor-specific cytotoxic and proliferative T cell response. However, there is no increase following viral therapy in either serum tumor antibody levels or viral-neutralizing antibodies. Thus specific T cell responses appear to mediate viral-elicited prolongation in survival. These data suggest that designing new viruses capable of augmenting T cell responses may induce stronger tumor destruction upon viral therapy.

Safety and immunogenicity of glycoprotein D-adjuvant genital herpes vaccine

BACKGROUND

Two previous trials have suggested that a herpes simplex virus (HSV) type 2 glycoprotein D (gD) vaccine combined with the adjuvants alum and 3'-O-deacylated-monophosphoryl lipid A (MPL) is well tolerated and provides protection against genital herpes disease in women with no preexisting HSV antibody.

METHODS

The safety and immunogenicity of this vaccine were evaluated in a large, multicenter, double-blind, randomized, placebo-controlled trial. The effects of sex and preexisting HSV immunity were sought.

RESULTS

When solicited symptoms that continued after the initial 4 days of observation were excluded, the incidence of unsolicited symptoms occurring during the 7 months after vaccination (the primary analysis period) was 22.1% in vaccine recipients and 21.9% in placebo recipients. Significant increases in the number of local and systemic symptoms were found in vaccine recipients within 4 days after vaccination. However, most symptoms were mild to moderate in severity and were short lived. Women reported symptoms more frequently than did men, but preexisting immunity had little effect. The vaccine induced higher titers of HSV gD antibody on enzyme-linked immunosorbent assays than did natural infection with HSV.

CONCLUSION

The vaccine was generally safe, well tolerated, and immunogenic.

The challenge of developing a herpes simplex virus 2 vaccine

HSV infections are prevalent worldwide. A vaccine to prevent genital herpes would have a significant impact on this disease. Several vaccines have shown promise in animal models; however, so far these have not been successful in human clinical studies. Prophylactic HSV vaccines to prevent HSV infection or disease have focused primarily on eliciting antibody responses. Potent antibody responses are needed to result in sufficiently high levels of virus-specific antibody in the genital tract. Therapeutic vaccines that reduce recurrences need to induce potent T-cell responses at the site of infection. With the increasing incidence of HSV-1 genital herpes, an effective herpes vaccine should protect against both HSV-1 and HSV-2. Novel HSV vaccines, such as replication-defective or attenuated viruses, have elicited humoral and cellular immune responses in preclinical studies. These vaccines and others hold promise in future clinical studies.

New concepts in herpes simplex virus vaccine development: notes from the battlefield

The recent discovery that T cells recognize different sets of herpes simplex virus type 1 and type 2 epitopes from seropositive symptomatic and asymptomatic individuals might lead to a fundamental immunologic advance in vaccine development against herpes infection and diseases. The newly introduced needle-free mucosal (i.e., topical ocular and intravaginal) lipopeptide vaccines provide a novel strategy that might target ocular and genital herpes and possibly provide 'heterologous protection' from HIV-1. Indeed, mucosal self-adjuvanting lipopeptide vaccines are easy to manufacture, simple to characterize, extremely pure, cost-effective, highly immunogenic and safe. In this review, we bring together recent published and unpublished data that illuminates the status of epitope-based herpes vaccine development and present an overview of our recent approach to an 'asymptomatic epitope'-based lipopeptide vaccine.

Impact of Immunization with Glycoprotein D2/AS04 on Herpes Simplex Virus Type 2 Shedding into the Genital Tract in Guinea Pigs That Become Infected

In recent clinical trials, a vaccine that contained herpes simplex virus type 2 (HSV-2) glycoprotein D (gD2) and the adjuvant AS04 afforded HSV-seronegative women significant protection against HSV-2 genital disease and limited protection against infection. Similarly, in guinea pigs, immunization with the vaccine provided significant protection against genital HSV-2 disease but did not prevent mucosal infection. We explored the impact of immunization on the magnitude of latent virus infection and on the frequency and magnitude of virus reactivation as measured by both recurrent disease and viral shedding into the genital tract. Guinea pigs immunized with gD2/AS04 were shown by quantitative polymerase chain reaction (qPCR) analysis to have significantly less latent viral DNA in the ganglia than did naive control guinea pigs and to have a reduced incidence and frequency of recurrent disease. By contrast, all immunized guinea pigs shed virus into the genital tract with a frequency comparable to that seen in control guinea pigs. However, the amount of virus shed was significantly reduced, as measured by qPCR. These data suggest that immunization could affect transmission by altering viral shedding patterns.

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.

Cutting edge: recombinant Listeria monocytogenes expressing a single immune-dominant peptide confers protective immunity to herpes simplex virus-1 infection

The vast majority of the world's population is infected with HSV. Although antiviral therapy can reduce the incidence of reactivation and asymptomatic viral shedding, and limit morbidity and mortality from active disease, it cannot cure infection. Therefore, the development of an effective vaccine is an important global health priority. In this study, we demonstrate that recombinant Listeria monocytogenes (Lm) expressing the H-2K(b) glycoprotein B (gB)(498-505) peptide from HSV-1 triggers a robust CD8 T cell response to this Ag resulting in protective immunity to HSV infection. Following challenge with HSV-1, immune-competent mice primed with recombinant Lm-expressing gB(498-505) Ag were protected from HSV-induced paralysis. Protection was associated with dramatic reductions in recoverable virus, and early expansion of HSV-1-specific CD8 T cells in the regional lymph nodes. Thus, recombinant Lm-expressing Ag from HSV represents a promising new class of vaccines against HSV infection.

Immune response of T cells during herpes simplex virus type 1 (HSV-1) infection

Herpes simplex virus type 1 (HSV-1), a neurotropic member of the alphaherpes virus family, is among the most prevalent and successful human pathogens. HSV-1 can cause serious diseases at every stage of life including fatal disseminated disease in newborns, cold sores, eye disease, and fatal encephalitis in adults. HSV-1 infection can trigger rapid immune responses, and efficient inhibition and clearance of HSV-1 infection rely on both the innate and adaptive immune responses of the host. Multiple strategies have been used to restrict host innate immune responses by HSV-1 to facilitate its infection in host cells. The adaptive immunity of the host plays an important role in inhibiting HSV-1 infections. The activation and regulation of T cells are the important aspects of the adaptive immunity. They play a crucial role in host-mediated immunity and are important for clearing HSV-1. In this review, we examine the findings on T cell immune responses during HSV-1 infection, which hold promise in the design of new vaccine candidates for HSV-1.

Evaluation of AD472, a live attenuated recombinant herpes simplex virus type 2 vaccine in guinea pigs

An attenuated recombinant herpes simplex virus type 2 (HSV-2), designated as AD472, was constructed by deleting both copies of the gamma(1)34.5 gene, UL55-56, UL43.5, and the US10-12 region from HSV-2 strain G. This virus was engineered to be a safe and effective live attenuated HSV-2 vaccine and was tested in the guinea pig model of genital herpes to evaluate its ability to protect from disease upon challenge with the wild type (wt) virus, HSV-2 (G). AD472 administered intramuscularly did not prevent infection or virus replication in the vaginal tract, but did reduce both lesion development and severity in a dose-dependent manner in guinea pigs challenged with the wt virus. Frequency of reactivation from latency was low compared with that of the parent virus, HSV-2 (G). Immunization with AD472 at doses of 1x10(5)PFU generally precluded colonization of the ganglia or establishment of latency by the challenge virus. Results presented here support the concept of a rationally engineered live attenuated vaccine for the prevention of the genital disease associated with infection by HSV-2.