Herpes simplex virus vaccines as immunotherapeutic agents

Novel rat models to study primary genital herpes simplex virus-2 infection

In this study we describe that six rat models (SD, WIST, LEW, BN, F344 and DA) are susceptible to intravaginal herpes simplex virus-2 (HSV-2) infection after pre-treatment with progesterone. At a virus dose of 5 × 10(6) PFU of HSV-2, all rat models were infected presenting anti-HSV-2 antibodies, infectious virus in vaginal washes, and HSV-2 DNA genome copies in lumbosacral dorsal root ganglia and the spinal cord. Most of the LEW, BN, F344, and DA rats succumbed in systemic progressive symptoms at day 8-14 post infection, but presented no or mild genital inflammation while SD and WIST rats were mostly infected asymptomatically. Infected SD rats did not reactivate HSV-2 spontaneously or after cortisone treatment. In an HSV-2 virus dose reduction study, F344 rats were shown to be most susceptible. We also investigated whether an attenuated HSV-1 strain (KOS321) given intravaginally, could protect from a subsequent HSV-2 infection. All LEW, BN, and F344 rats survived a primary HSV-1 infection and no neuronal infection was established. In BN and F344 rats, anti-HSV-1 antibodies were readily detected while LEW rats were seronegative. In contrast to naïve LEW, BN, and F344 rats where only 3 of 18 animals survived 5 × 10(6) PFU of HSV-2, 23 of 25 previously HSV-1 infected rats survived a challenge with HSV-2. The described models provide a new approach to investigate protective effects of anti-viral microbicides and vaccine candidates, as well as to study asymptomatic primary genital HSV-2 infection.

Mucosal herpes immunity and immunopathology to ocular and genital herpes simplex virus infections

Herpes simplex viruses type 1 and type 2 (HSV-1 and HSV-2) are amongst the most common human infectious viral pathogens capable of causing serious clinical diseases at every stage of life, from fatal disseminated disease in newborns to cold sores genital ulcerations and blinding eye disease. Primary mucocutaneous infection with HSV-1 & HSV-2 is followed by a lifelong viral latency in the sensory ganglia. In the majority of cases, herpes infections are clinically asymptomatic. However, in symptomatic individuals, the latent HSV can spontaneously and frequently reactivate, reinfecting the muco-cutaneous surfaces and causing painful recurrent diseases. The innate and adaptive mucosal immunities to herpes infections and disease remain to be fully characterized. The understanding of innate and adaptive immune mechanisms operating at muco-cutaneous surfaces is fundamental to the design of next-generation herpes vaccines. In this paper, the phenotypic and functional properties of innate and adaptive mucosal immune cells, their role in antiherpes immunity, and immunopathology are reviewed. The progress and limitations in developing a safe and efficient mucosal herpes vaccine are discussed.

Identity of zinc finger nucleases with specificity to herpes simplex virus type II genomic DNA: novel HSV-2 vaccine/therapy precursors

Background

Herpes simplex type II (HSV-2) is a member of the family herpesviridae. Human infection with this double stranded linear DNA virus causes genital ulcerative disease and existing treatment options only serve to resolve the symptomatology (ulcers) associated with active HSV-2 infection but do not eliminate latent virus. As a result, infection with HSV-2 follows a life-long relapsing (active versus latent) course. On the basis of a primitive bacterium anti-phage DNA defense, the restriction modification (R-M) system, we previously identified the Escherichia coli restriction enzyme (REase) EcoRII as a novel peptide to excise or irreversibly disrupt latent HSV-2 DNA from infected cells. However, sequences of the site specificity palindrome of EcoRII 5'-CCWGG-3' (W = A or T) are equally present within the human genome and are a potential source of host-genome toxicity. This feature has limited previous HSV-2 EcoRII based therapeutic models to microbicides only, and highlights the need to engineer artificial REases (zinc finger nucleases-ZFNs) with specificity to HSV-2 genomic-DNA only. Herein, the therapeutic-potential of zinc finger arrays (ZFAs) and ZFNs is identified and modeled, with unique specificity to the HSV-2 genome.

Methods and results

Using the whole genome of HSV-2 strain HG52 (Dolan A et al.,), and with the ZFN-consortium's CoDA-ZiFiT software pre-set at default, more than 28,000 ZFAs with specificity to HSV-2 DNA were identified. Using computational assembly (through in-silico linkage to the Flavobacterium okeanokoites endonuclease Fok I of the type IIS class), 684 ZFNs with specificity to the HSV-2 genome, were constructed. Graphic-analysis of the HSV-2 genome-cleavage pattern using the afore-identified ZFNs revealed that the highest cleavage-incidence occurred within the 30,950 base-pairs (~between the genomic context coordinates 0.80 and 1.00) at the 3' end of the HSV-2 genome. At approximately 3,095 bp before and after the 5' and 3' ends of the HSV-2 genome (genomic context coordinates 0.02 and 0.98, respectively) were specificity sites of ZFNs suited for the complete excision of over 60% of HSV-2 genomic material from within infected human cells, through the process of non-homologous end joining (NHEJ). Furthermore, a model concerning a recombinant (ICP10-PK mutant) replication competent HSV-2 viral vector for delivering and transducing a diploid copy (or pair) of the HSV-2-genome-specific ZFN genotype within neuronal tissue, is presented.

Conclusion

ZFNs with specificity to HSV-2 genomic DNA that are precursors of novel host-genome expressed HSV-2 gene-therapeutics or vaccines were identified.

Circulating herpes simplex type 1 (HSV-1)-specific CD8+ T cells do not access HSV-1 latently infected trigeminal ganglia

Background

Therapeutic vaccines can be designed to enhance existing T cell memory populations for increased protection against re-infection. In the case of herpes simplex virus type 1, recurrent disease results from reactivation of latent virus in sensory ganglia, which is controlled in part by a ganglia-resident HSV-specific memory CD8⁺ T cell population. Thus, an important goal of a therapeutic HSV-1 vaccine would be to enhance this population.

Methods

HSV-1-infected mice were treated with TAK-779 to block CCR5- and CXCR3-mediated CD8⁺ T cell migration during both acute and latent infections. Additionally, HSV-1-specific CD8⁺ T cells were transferred into HSV-1 latently infected mice to mimic the effect of a therapeutic vaccine, and their migration into trigeminal ganglia (TG) was traced during steady-state latency, or during recovery of the TG-resident memory CD8⁺ T cell population following stress-, and corticosterone-induced depletion and HSV-1 reactivation from latency. Bromodeoxy uridine (BrdU) incorporation measured cell proliferation in vivo.

Results

TAK-779 treatment during acute HSV-1 infection reduced the number of infiltrating CD8⁺ T cells but did not alter the number of viral genome copies. TAK-779 treatment during HSV latency did not affect the size of the TG-resident memory CD8⁺ T cell population. Transferred HSV-specific CD8⁺ T cells failed to access latently infected TG during steady-state latency, or during recovery of the TG resident HSV-specific CD8⁺ T cell population following exposure of latently infected mice to stress and corticosterone. Recovery of the HSV-specific CD8⁺ T cell population after stress and corticosterone treatment occurred with homeostatic levels of cell division and did not require CD4⁺ T cell help.

Conclusions

Our findings are consistent with the notion that the CD8⁺ T cells in latently infected TG are a tissue-resident memory (Trm) population that is maintained without replenishment from the periphery, and that when this population is disrupted, it recovers without proliferation or detectable recruitment of HSV-specific CD8⁺ T cells from the blood. The compartmentalization of the HSV-specific CD8⁺ memory T cell population in latently infected TG will complicate the design of therapeutic vaccines.

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.

Novel two-parameter flow cytometry (MIL4/SSC followed by MIL4/CT7) allows for identification of five fractions of guinea pig leukocytes in peripheral blood and lymphoid organs

Though the guinea pig has been an extremely useful animal model for a variety of diseases, the tools necessary to undertake a full-scale immunological analysis of the guinea pig have been lacking. For instance, traditional two-parameter forward/side scatter (FSC/SSC) flow cytometry, though effective in human and other animal models, is unable to adequately identify the distinct fractions of guinea pig peripheral blood leukocytes (PBL). We introduce here a new flow cytometric technique (MIL4/SSC followed by MIL4/CT7) which redresses this lack by identifying and characterizing five distinct fractions of PBL: neutrophils, lymphocytes, monocytes, eosinophils plus basophils, and the novel MIL4(-)SSC(large)CT7(high) population. The MIL4(-)SSC(large)CT7(high) cells possess cytoplasmic inclusion bodies of variable size that were positive for periodic acid Schiff (PAS). Their cell surface stained positive for the helper/inducer lymphocyte markers, T cell markers, CD45, Thy-1, asialo GM1 and FcR, but negative for B cell markers, such as membrane-type IgM, CD8 and MHC class II. The novel flow cytometric technique also allowed us to establish that the five leukocyte fractions were found in PBL, splenocytes, thymocytes and lymph node cells. Cells which were positive for inclusion bodies comprised 16.6% of splenocytes, 9.9% of PBL and 4.3% of liver cells, but were comparatively rare in lymph node cells, thymocytes, and BM cells. The novel flow cytometric technique introduced here will allow a better understanding of the response of each type of guinea pig leukocyte and thereby shed light on the diseases with which they are associated.

Imunoprofilaxia anti-herpética utilizando vírus geneticamente modificado: vacina DISC

As vacinas anti-herpéticas podem atuar de forma profilática ou terapêutica contra a infecção pelo herpes simples. Diversos tipos de vacinas foram avaliados no passado com resultados pouco efetivos, tais como aquelas que utilizaram vírus vivos, porém atenuados, e as que utilizaram subunidades glicoprotéicas. As novas vacinas do tipo DISC, com partículas infectivas incapacitadas para mais de um ciclo replicativo, são desenhadas para combinar a segurança e as vantagens das vacinas que utilizam vírus atenuados com a imunogenicidade das que usam vírus vivos. Nas vacinas DISC utiliza-se um vírus cujo gene para a glicoproteína H foi removido. Torna-se, assim, capaz de infectar células humanas, exatamente como o vírus natural, mas sua progênie não pode mais completar o ciclo replicativo. São partículas virais não patogênicas, capazes de induzir ampla resposta de linfócitos T citotóxicos e da imunidade humoral contra antígenos herpéticos.

Vaccines in the 21st century

Steffens was wrong about the Soviet Union, and I may well be wrong about the future of vaccines; however, in Table 13, I give my [table: see text] prediction of the vaccination schedule of the next century. It is an optimistic vision, so let us hope that I am right.

Immunisation with phage displaying peptides representing single epitopes of the glycoprotein G can give rise to partial protective immunity to HSV-2

Filamentous phage displaying peptides representing single epitopes of the glycoprotein G of HSV-2 (gG2) were used as immunogens via the subcutaneous route in Balb/c mice without additional adjuvant. The phage were isolated from a random phage peptide display library and contain 15-mer peptide inserts that mimic epitopes of gG2. In each case, an antibody response to gG2 was generated that was dependent on the dose of phage administered and on the presence of the peptide insert. Phage displaying epitopes of gG2, which map to amino acids 551-570, were the most immunogenic; interestingly, this region of gG2 is frequently recognised by patients infected with HSV-2. The data also provide interesting information as regards choice of peptide mimics for use as immunogens because, surprisingly, the most antigenic of the individual clones was the least immunogenic. In two of the experiments, mice immunised with phage displaying a single epitope of gG2 were protected against challenge with a lethal dose of whole HSV-2. This suggests a possible role for phage-displayed peptides in inducing protective immunity against pathogens and provides a model system for investigating the underlying mechanisms.

Therapeutic vaccination against HSV-2: influence of vaccine formulation on immune responses and protection in mice

Therapeutic immunisation may represent a means of influencing viral infections that persist in the host by modulating the nature or level of host immunity. To assess the influence of the form of the antigenic stimulus on immunity to type-2 herpes simplex virus (HSV-2), mice pre-infected with sublethal doses of HSV-2 were immunised with various HSV-2 vaccine formulations prior to challenge infection with heterologous HSV-1. Measurements of interleukin-2 (IL-2), interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) levels in mouse spleen cell cultures restimulated in vitro with HSV-2 antigens showed that, depending on the form of HSV-2 antigen preparation used in this therapeutic context, changes in the levels of these cytokines could be effected. Measurement of HSV-specific antibody by serological tests support the contention that immunisation of HSV-2-infected mice can either enhance the existing Th1-like immune response elicited following HSV-2 infection, or modulate this response towards a more Th2-like profile, and this is dependent on the form of the antigenic stimulus. The degree of protection against subsequent lethal, heterologous HSV-1 challenge infection varied according to the nature of the infection and the immunisation history of the animals.

Prospects for control of herpes simplex virus disease through immunization

Herpes simplex viruses (HSVs) can cause a variety of infections, including genital herpes. Despite effective antiviral therapy, HSV infections remain a significant worldwide public health problem. Vaccines offer the best hope for controlling spread and limiting HSV disease. This article discusses the pathogenesis and immunobiology of mucocutaneous HSV infections, summarizes the spectrum of diseases caused by HSV, and provides a review of the field of HSV vaccine research. This article also discusses what might be realistically expected of a vaccine intended for control of genital herpes and explores the question of whether a vaccine that is effective in controlling genital HSV disease might also be effective in controlling nongenital HSV disease. The efficacy of such vaccines for the full spectrum of HSV disease will eventually determine the timing and targeting of immunization, ranging from selective immunization in preadolescence to universal childhood immunization as part of the routine childhood regimen.

Herpes simplex virus vaccines

Herpes simplex virus (HSV) infections are common and produce not only a primary infection, but also latent and recurrent infections. Therefore, the goals of a HSV vaccine are different from other vaccines. In this review, the goals of both prophylactic and therapeutic HSV vaccines are discussed and related to the immunobiology of acute and recurrent HSV infections. Next, the vaccine strategies that have been and are being evaluated for control of HSV disease are described. Current approaches take advantage of many of the modern methodologies for vaccine development. Thus, as we await final evaluations of subunit HSV glycoprotein vaccines, early phase I trails are evaluating newer vaccine approaches including DNA-based vaccines and replication-impaired viruses. The definitive HSV vaccine may await increased knowledge of the optimal viral antigen(s) and routes to induce genital tract immunity.

Herpes. Vaccines for HSV

Herpes simplex viruses type 1 (HSV-1) and 2 (HSV-2) are ubiquitous human pathogens capable of producing primary, latent, and recurrent infections. These viruses cause a variety of clinical illnesses including genital herpes, oral-facial infections, cutaneous infections, ocular infections, neonatal herpes, herpes encephalitis, disseminated infection, and erythema multiforme. This article summarizes the past and current efforts to develop both prophylactic and therapeutic HSV vaccines.

Prospects for the development of fungal vaccines

In an era that emphasizes the term "cost-effective," vaccines are the ideal solution to preventing disease at a relatively low cost to society. Much of the previous emphasis has been on childhood scourges such as measles, mumps, rubella, poliomyelitis, and Haemophilus influenzae type b. The concept of vaccines for fungal diseases has had less impact because of the perceived limited problem. However, fungal diseases have become increasingly appreciated as serious medical problems that require recognition and aggressive management. The escalation in the incidence and prevalence of infection has prompted a renewed interest in vaccine development. Herein, I discuss the most recent developments in the search for vaccines to combat fungal infections. Investigators have discovered several inert substances from various fungi that can mediate protection in animal models. The next challenge will be to find the suitable mode of delivery for these immunogens.

Enhancement of the immune response to non-replicating herpes simplex virus type-1 preparations by mucosal administration in the presence of cholera toxin

Different immunization regimes were compared in order to enhance the immune response following mucosal administration of non-replicating HSV-1 preparations to mice. The serum anti-HSV Ig response following intragastric administration of heat or UV inactivated HSV-1 strain SC16 was compared with that elicited by an attenuated derivative of SC16 (TKDM21). The highest response followed immunization with TKDM21 and this was markedly enhanced by repeated intragastric administration, reaching ca 35% of that elicited following a cutaneous infection with live virus. Repeated doses of killed virus produced only a minimal increase in the response even when given intranasally (i.n.). However, cholera toxin and its B-subunit with UV-inactivated virus or a mixture of purified viral glycoproteins enhanced the anti-HSV response after i.n. immunization and produced antibody levels equivalent to those following intragastric delivery of live TKDM21.

Red blood cells as delivery system for recombinant HSV-1 glycoprotein B: immunogenicity and protection in mice

The immunotherapeutic potential of autologous red blood cells (RBC) coupled to the secretory form of herpes simplex virus type 1 (HSV-1) glycoprotein B (gB1s) was examined with a mouse model of HSV-1 infection. C57BL/6 mice were immunized intraperitoneally with gB1s (0.05 microgram per dose) linked to RBC, or mixed with Freund's complete or bound to AlPO4 adjuvants (0.5 microgram per dose). Mice immunized with RBC coupled gB1s were protected against lethal and latent HSV-1 infection, and developed an anti-HSV antibody response, as measured by ELISA and HSV-1 neutralization assays, similar or higher than that elicited by the same antigen in Freund's complete adjuvant, which suggested that autologous RBC coupled to gB1s may provide an effective and safe method of immunization against HSV infection.

Herpes simplex: evolving concepts

A large body of molecular biologic research has begun to clarify some basic aspects of viral latency and reactivation. The clinical definition of herpes simplex virus infection is expanding, with the recognition that the disease is largely asymptomatic and that most transmission occurs during periods of asymptomatic viral shedding. With this awareness, serologic diagnosis has become increasingly important. New treatment modalities are now available, and other promising treatments are in development.