Disabled Infectious Single Cycle Research Articles

A Novel Strategy to Generate a Recombinant, Live-Virus, Replication Incompetent Congenital Cytomegalovirus Vaccine Candidate

Abstract Background Preventing congenital cytomegalovirus (cCMV) infection, the most common infectious cause of disability in pediatrics, is a high public health priority. Subunit vaccine studies based on single viral proteins (usually envelope glycoproteins) have yielded disappointing results in clinical trials. In contrast, Disabled infectious single cycle (DISC) recombinant viruses are promising vaccine candidates, offering the potential for a robust immune response against multiple viral immunogens while maintaining an attenuated phenotype. These studies sought to examine the safety and immunogenicity of this strategy in an animal model of vaccine-preventable cCMV infection, the guinea pig cytomegalovirus (GPCMV) model. Design/Methods Vaccine design consisted of introducing a ligand-regulatable FKBP protein destabilization domain, ddFKBP, into an essential viral gene. This domain directs degradation of the tagged protein in cells unless the synthetic compound Shield-1 is present, allowing generation of viral particles capable of single-cycle replication. Two such essential genes, the GPCMV homologs of CMV genes UL51 and UL52 (GP51 and GP52), were targeted for vaccine design. In this study, we sought to test: 1) whether the DISC viruses GP51 and GP52 were attenuated for replication in a guinea pig model; and 2) whether the replication-incompetent viruses retained immunogenicity comparable to a wild-type virus. GPCMV-seronegative guinea pigs were challenged with DISC vaccines GP51 or GP52. Control animals were challenged with wild-type GPCMV (SG24). Animals (3 per group) were infected by subcutaneous injection and boosted at day 21. Blood collected at days 0, 7, 14, 21, 28, 35, 42, and 84 was used for PCR (to gauge attenuation) and serology (to examine immunogenicity). Results Real-time PCR showed a mean viral load of 8.5 x 105 genome copies/mL of blood at day 7 and 9.3 x 104 genome copies/mL at day 14 in guinea pigs that received SG24 compared to 2.9 x 104 and 1.9 x 103 genome copies/mL at days 7 and 14 respectively in recipients of GP51. No viral DNA was detected in recipients of GP52 at either day 7 or 14. These data demonstrate significantly lower viremia in the GP51 and GP52 groups compared to SG24 by two-way ANOVA (p<0.01; Fig. 1A). In spite of marked attenuation, no statistically significant difference in immune response was noted, with equivalent ELISA responses detected upon comparison of animals that received GP51, GP52, or SG24 CMV strains at days 14, 35, or 84 (Fig. 1B). Western blot analysis of sera used to probe fractions containing wild-type viral particles likewise demonstrated induction of a robust antibody response by GP51 and GP52. Conclusion(s) These data suggest that GP51 and GP52 are attenuated for replication but induce an immune response comparable to wild-type infection. Thus, they are promising options in the development of a vaccine to prevent cCMV. Examination of the extent of attenuation against vertical transmission of these DISC viruses, as well as their efficacy as vaccine candidates against cCMV, is warranted. These questions have important implications for potential future human clinical trials. Funding: Supported by 5 T35 AI118620-07, Medical Student Summer Research Program in Infection and Immunity

Vaccination with a replication-defective cytomegalovirus vaccine elicits a glycoprotein B-specific monoclonal antibody repertoire distinct from natural infection

Human Cytomegalovirus (HCMV) is the leading infectious congenital infection globally and the most common viral infection in transplant recipients, therefore identifying a vaccine for HCMV is a top priority. Humoral immunity is a correlate of protection for HCMV infection. The most effective vaccine tested to date, which achieved 50% reduction in acquisition of HCMV, was comprised of the glycoprotein B protein given with an oil-in-water emulsion adjuvant MF59. We characterize gB-specific monoclonal antibodies isolated from individuals vaccinated with a disabled infectious single cycle (DISC) CMV vaccine, V160, and compare these to the gB-specific monoclonal antibody repertoire isolated from naturally-infected individuals. We find that vaccination with V160 resulted in gB-specific antibodies that bound homogenously to gB expressed on the surface of a cell in contrast to antibodies isolated from natural infection which variably bound to cell-associated gB. Vaccination resulted in a similar breadth of gB-specific antibodies, with binding profile to gB genotypes 1–5 comparable to that of natural infection. Few gB-specific neutralizing antibodies were isolated from V160 vaccinees and fewer antibodies had identifiable gB antigenic domain specificity compared to that of naturally-infected individuals. We also show that glycosylation of gB residue N73 may shield binding of gB-specific antibodies.

Cross Strain Protection against Cytomegalovirus Reduces DISC Vaccine Efficacy against CMV in the Guinea Pig Model.

Congenital cytomegalovirus (CMV) is a leading cause of disease in newborns and a vaccine is a high priority. The guinea pig is the only small animal model for congenital CMV but requires guinea pig cytomegalovirus (GPCMV). Previously, a disabled infectious single cycle (DISC) vaccine strategy demonstrated complete protection against congenital GPCMV (22122 strain) and required neutralizing antibodies to various viral glycoprotein complexes. This included gB, essential for all cell types, and the pentamer complex (PC) for infection of non-fibroblast cells. All GPCMV research has utilized prototype strain 22122 limiting the translational impact, as numerous human CMV strains exist allowing re-infection and congenital CMV despite convalescent immunity. A novel GPCMV strain isolate (designated TAMYC) enabled vaccine cross strain protection studies. A GPCMV DISC (PC+) vaccine (22122 strain) induced a comprehensive immune response in animals, but vaccinated animals challenged with the TAMYC strain virus resulted in sustained viremia and the virus spread to target organs (liver, lung and spleen) with a significant viral load in the salivary glands. Protection was better than natural convalescent immunity, but the results fell short of previous DISC vaccine sterilizing immunity against the homologous 22122 virus challenge, despite a similarity in viral glycoprotein sequences between strains. The outcome suggests a limitation of the current DISC vaccine design against heterologous infection.

Inclusion of the Viral Pentamer Complex in a Vaccine Design Greatly Improves Protection against Congenital Cytomegalovirus in the Guinea Pig Model.

A vaccine against congenital cytomegalovirus (cCMV) is a high priority. The guinea pig is a small-animal model for cCMV. A disabled infectious single-cycle (DISC) viral vaccine strain based on a guinea pig cytomegalovirus (GPCMV) capsid mutant was evaluated. A previous version of this vaccine did not express the gH/gL-based pentamer complex (PC) and failed to fully protect against cCMV. The PC is necessary for GPCMV epithelial cell/trophoblast tropism and congenital infection and is a potentially important neutralizing antigen. Here, we show that a second-generation PC-positive (PC+) DISC (DISCII) vaccine induces neutralizing antibodies to the PC and other glycoproteins and a cell-mediated response to pp65 (GP83). Additionally, a CRISPR/Cas9 strategy identified guinea pig platelet-derived growth factor receptor alpha (PDGFRA) to be the receptor for PC-independent infection of fibroblast cells. Importantly, PDGFRA was absent in epithelial and trophoblast cells, which were dependent upon the viral PC for infection. Virus neutralization by DISCII antibodies on epithelial and trophoblast cells was similar to that in sera from wild-type virus-infected animals and dependent in part on PC-specific antibodies. In contrast, sera from PC-negative virus-infected animals poorly neutralized virus on non-fibroblast cells. DISCII-vaccinated animals were protected against congenital infection, in contrast to a nonvaccinated group. The target organs of pups in the vaccine group were negative for wild-type virus, unlike those of pups in the control group, with GPCMV transmission being approximately 80%. Overall, the DISCII vaccine had 97% efficacy against cCMV. The complete protection provided by this PC+ DISC vaccine makes the possibility of the use of this approach against human cCMV attractive.IMPORTANCE Cytomegalovirus (CMV) is a leading cause of congenital disease in newborns, and an effective vaccine remains an elusive goal. The guinea pig is the only small-animal model for cCMV. Guinea pig cytomegalovirus (GPCMV) encodes a glycoprotein pentamer complex (PC) for entry into non-fibroblast cells, including placental trophoblasts, to enable cCMV. As with human cytomegalovirus (HCMV), GPCMV uses a specific cell receptor (PDGFRA) for fibroblast entry, but other receptors are required for non-fibroblast cells. A disabled infectious single-cycle (DISC) GPCMV vaccine strain induced an antibody immune response to the viral pentamer to enhance virus neutralization on non-fibroblast cells, and vaccinated animals were fully protected against cCMV. Inclusion of the PC as part of a vaccine design dramatically improved vaccine efficacy, and this finding underlines the importance of the immune response to the PC in contributing toward protection against cCMV. This vaccine represents an important milestone in the development of a vaccine against cCMV.

Towards the Generation of an ASFV-pA104R DISC Mutant and a Complementary Cell Line-A Potential Methodology for the Production of a Vaccine Candidate.

African swine fever (ASF) is a fatal viral disease of domestic swine and wild boar, considered one of the main threats for global pig husbandry. Despite enormous efforts, to date, neither the classical vaccine formulations nor the use of protein subunits proved to be efficient to prevent this disease. Under this scenario, new strategies have been proposed including the development of disabled infectious single cycle (DISC) or replication-defective mutants as potential immunizing agents against the ASF virus (ASFV). In this study, we describe the methodology to generate an ASFV-DISC mutant by homologous recombination, lacking the A104R gene, which was replaced by the selection marker (GUS gene). The recombinant viruses were identified when the infected cells acquired a blue color in the presence of X-Gluc (100 µg/mL), which is the substrate for the GUS gene. Since these viral particles result from loss-of-function mutations, being unable to replicate, helper-cell lines expressing the viral pA104R protein were produced. Vero and COS-1 cell lines were transfected by different methods, both physical and chemical, in order to stably express the ASFV-pA104R. Best results were obtained by using Lipofectamine 2000 and Nucleofection methodology of Vero with the pIRESneo vector and by using Flp-FRT site-directed recombination technology system in Flp-In CV-1 cells (transformed COS-1 cells with a single integration site in a transcriptional active region). In order to ensure an efficient and stable integration of the viral ORF on the host cellular genome, the maintenance of the insert was verified by PCR and its expression by immunofluorescence and immunoblot analysis. Although the isolation of the recombinant virus was not achieved, the confirmation of ASFV-ΔA104R sequence, and the detection of the recombinant mutant through three passages, suggest that this approach is feasible and could be a potential strategy to generate safe and efficient DISC vaccine candidates.

New generation vaccines against bluetongue virus

Over the last three decades, a variety of approaches have been investigated to develop new types of bluetongue virus (BTB) vaccines, ranging from baculovirus-expressed subunit vaccines to live vector vaccines. DNA vaccines against BTV consist of DNA plasmid expressing different BTV proteins after inoculation of the animals. The recombinant viral vector vaccines against BTV are based on recombinant viruses that express desired BTV antigens in the host upon inoculation. Viruses such as vaccinia, modified vaccinia Ancara (MVA), capripox, canarypox, herpes, myxoma and fowlpox viruses have been used as vectors of BTV genes. The reverse genetics (RG) systems for BTV are useful tools for BTV vaccine development. Disabled infectious single-cycle (DISC) vaccines make it possible to restore virus replication and can be used for differentiating infected from vaccinated animals (DIVA). These vaccines are based on the production of a modified virus with a deletion in one or more genes that are essential for virus replication. Another approach for BTV vaccine development using RG is the disabled infectious single-animal (DISA) vaccine, generated by deletion of NS3/NS3a expression. DISC and DISA vaccines can mimic the natural tropism of the virus and can express BTV proteins at the site of infection. Important advantages of these new generation vaccines over the conventional BTV vaccines are their high efficacy as well as the possibility of applying them for DIVA. At present, there are a number of novel laboratory-scale BTV vaccines that could meet vaccine profiles required for different field situations. However, further development and licensing of these vaccine candidates for many BTV serotypes is needed in order to prepare for future BT outbreaks. To date, all novel BTV vaccines described in this paper are still under laboratory testing. They are not available commercially, and the time of their application in the field is still indefinite. .

BTV-vector-host interaction: the epidemiological triangle in disease transmission

Understanding the interaction between the bluetongue virus (BTV), the Culicoides vector and the ruminant host is essential to control bluetongue (BT). This triangle of interaction can be understood individually at the level of the virus, the level of vector and the host level. BTV-vector-host interactions involve physiological and ecological mechanisms, and they have evolved under a specific set of environmental conditions. Recent advances in understanding this interaction include increased knowledge of the virus replication cycle, BTV immunology and pathogenesis in the vertebrate host, as well as the virulence and pathogenicity features of newly discovered BTV serotypes. To understand the virus-host-vector interaction, new molecular biology techniques and experimental infection biology methods have been widely used. The next-generation sequencing, the establishment of a reverse genetics system for the virus, and development of novel infection models and refinement of the existing BTV experimental infection methodologies have proven very helpful. This progress in biotechnology has also made it possible to develop new-generation BTV vaccines, such as disabled infectious single cycle (DISC) vaccines and disabled infectious single animal (DISA) vaccines. However, several questions still need to be answered, such as those concerning cellular pathways involved in the induction of innate immunity and the function of NS4 in the BTV replication cycle. In addition, the identities of specific molecular determinants and the role of quasi-species diversity in determining BTV phenotype are still unclear and should be better explained..

Replication-Deficient Particles: New Insights into the Next Generation of Bluetongue Virus Vaccines.

ABSTRACTBluetongue virus (BTV) is endemic in many parts of the world, often causing severe hemorrhagic disease in livestock. To date, at least 27 different serotypes have been recognized. Vaccination against all serotypes is necessary to protect susceptible animals and to prevent onward spread of the virus by insect vectors. In our previous studies, we generated replication-deficient (disabled infectious single-cycle [DISC]) virus strains for a number of serotypes and reported preliminary data on their protective efficacy in animals. In this report, to advance the DISC vaccines to the marketplace, we investigated different parameters of these DISC vaccines. First, we demonstrated the genetic stabilities of these vaccine strains and also the complementing cell line. Subsequently, the optimal storage conditions of vaccines, including additives, temperature, and desiccation, were determined and their protective efficacies in animals confirmed. Furthermore, to test if mixtures of different vaccine strains could be tolerated, we tested cocktails of DISC vaccines in combinations of three or six different serotypes in sheep and cattle, the two natural hosts of BTV. Groups of sheep vaccinated with a cocktail of six different vaccines were completely protected from challenge with individual virulent serotypes, both in early challenge and after 5 months of challenge without any clinical disease. There was no interference in protection between the different vaccines. Protection was also achieved in cattle with a mixture of three vaccine strains, albeit at a lesser level than in sheep. Our data support and validate the suitability of these virus strains as the next-generation vaccines for BTV.IMPORTANCE Bluetongue (BT) is a debilitating and in many cases lethal disease that affects ruminants of economic importance. Classical vaccines that afford protection against bluetongue virus, the etiological agent, are not free from secondary and undesirable effects. A surge in new approaches to produce highly attenuated, safer vaccines was evident after the development of the BTV reverse-genetics system that allows the introduction of targeted mutations in the virus genome. We targeted an essential gene to develop disabled virus strains as vaccine candidates. The results presented in this report further substantiate our previous evidence and support the suitability of these virus strains as the next-generation BTV vaccines.

Rapid Generation of Replication-Deficient Monovalent and Multivalent Vaccines for Bluetongue Virus: Protection against Virulent Virus Challenge in Cattle and Sheep

Since 1998, 9 of the 26 serotypes of bluetongue virus (BTV) have spread throughout Europe, and serotype 8 has suddenly emerged in northern Europe, causing considerable economic losses, direct (mortality and morbidity) but also indirect, due to restriction in animal movements. Therefore, many new types of vaccines, particularly subunit vaccines, with improved safety and efficacy for a broad range of BTV serotypes are currently being developed by different laboratories. Here we exploited a reverse genetics-based replication-deficient BTV serotype 1 (BTV-1) (disabled infectious single cycle [DISC]) strain to generate a series of DISC vaccine strains. Cattle and sheep were vaccinated with these viruses either singly or in cocktail form as a multivalent vaccine candidate. All vaccinated animals were seroconverted and developed neutralizing antibody responses to their respective serotypes. After challenge with the virulent strains at 21 days postvaccination, vaccinated animals showed neither any clinical reaction nor viremia. Further, there was no interference with protection with a multivalent preparation of six distinct DISC viruses. These data indicate that a very-rapid-response vaccine could be developed based on which serotypes are circulating in the population at the time of an outbreak.

Generation of replication-defective virus-based vaccines that confer full protection in sheep against virulent bluetongue virus challenge.

The reverse genetics technology for bluetongue virus (BTV) has been used in combination with complementing cell lines to recover defective BTV-1 mutants. To generate a potential disabled infectious single cycle (DISC) vaccine strain, we used a reverse genetics system to rescue defective virus strains with large deletions in an essential BTV gene that encodes the VP6 protein (segment S9) of the internal core. Four VP6-deficient BTV-1 mutants were generated by using a complementing cell line that provided the VP6 protein in trans. Characterization of the growth properties of mutant viruses showed that each mutant has the necessary characteristics for a potential vaccine strain: (i) viral protein expression in noncomplementing mammalian cells, (ii) no infectious virus generated in noncomplementing cells, and (iii) efficient replication in the complementing VP6 cell line. Further, a defective BTV-8 strain was made by reassorting the two RNA segments that encode the two outer capsid proteins (VP2 and VP5) of a highly pathogenic BTV-8 with the remaining eight RNA segments of one of the BTV-1 DISC viruses. The protective capabilities of BTV-1 and BTV-8 DISC viruses were assessed in sheep by challenge with specific virulent strains using several assay systems. The data obtained from these studies demonstrated that the DISC viruses are highly protective and could offer a promising alternative to the currently available attenuated and killed virus vaccines and are also compliant as DIVA (differentiating infected from vaccinated animals) vaccines.

Rescue of disabled infectious single-cycle (DISC) Equine arteritis virus by using complementing cell lines that express minor structural glycoproteins

Equine arteritis virus (EAV) contains seven structural proteins that are all required to produce infectious progeny. Alphavirus-based expression vectors have been generated for each of these proteins to explore the possibilities for their constitutive expression in cell lines. This approach was successful for minor glycoproteins GP(2b), GP(3) and GP(4) and for the E protein. Subsequently, it was demonstrated that cell lines expressing these proteins could rescue EAV mutants that were disabled in the expression of the corresponding gene, resulting in the production of virus particles carrying the mutant genome. This system was particularly efficient for GP(2b)- and GP(4)-knockout mutants. Upon infection of non-complementing cells with these mutants, a self-limiting single cycle of replication was initiated, resulting in the expression of all but one of the viral proteins. These disabled infectious single-cycle (DISC) arteriviruses can also be used to express foreign sequences and are potentially useful in both fundamental research and vaccine development.

Trafficking of tumor peptide-specific cytotoxic T lymphocytes into the tumor microcirculation.

The major histocompatibility complex class I-restricted CD8(+) cytotoxic T-lymphocyte (CTL) effector arm of the adaptive immune response can specifically recognize and destroy tumor cells expressing peptide antigens. Although adoptive T-cell therapy has been successfully used for the treatment of viral and malignant diseases, little is known of the trafficking and fate of adoptively transferred antigen-specific T cells. In the present study, splenocytes derived from mice that rejected their tumors (CT26 or CT26-clone 25 tumors) in response to direct intratumor injection of disabled infectious single-cycle herpes simplex virus (DISC-HSV) encoding murine GM-CSF were restimulated with peptide in vitro. CTLs specific for the AH-1 and beta-gal peptides expressed by CT26 and CT26-clone 25 tumor cells, respectively, were generated and used for adoptive cellular therapy and trafficking studies. Intravenous administration of AH-1-specific CTLs 3 days following i.v. injection of CT26 cells resulted in significant tumor growth inhibition, whereas administration of control CTLs generated against a bacterial beta-gal peptide did not inhibit the growth of tumors. Trafficking of AH-1-specific lymphocytes and their interaction with the CT26 tumor microcirculation was analyzed using real-time in vivo microscopy (IVM). AH-1-specific but not beta-gal-specific CTLs adhered and localized in the CT26 tumor microvasculature, but neither population adhered to the endothelium of the normal microcirculation. This study provides direct visual evidence suggesting that AH-1-specific CTLs that mediate a therapeutic response traffic to and localize within the tumor microenvironment.

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.

Tumor regression induced by intratumor therapy with a disabled infectious single cycle (DISC) herpes simplex virus (HSV) vector, DISC/HSV/murine granulocyte-macrophage colony-stimulating factor, correlates with antigen-specific adaptive immunity.

Direct intratumor injection of a disabled infectious single cycle HSV-2 virus encoding the murine GM-CSF gene (DISC/mGM-CSF) into established murine colon carcinoma CT26 tumors induced a significant delay in tumor growth and complete tumor regression in up to 70% of animals. Pre-existing immunity to HSV did not reduce the therapeutic efficacy of DISC/mGM-CSF, and, when administered in combination with syngeneic dendritic cells, further decreased tumor growth and increased the incidence of complete tumor regression. Direct intratumor injection of DISC/mGM-CSF also inhibited the growth of CT26 tumor cells implanted on the contralateral flank or seeded into the lungs following i.v. injection of tumor cells (experimental lung metastasis). Proliferation of splenocytes in response to Con A was impaired in progressor and tumor-bearer, but not regressor, mice. A potent tumor-specific CTL response was generated from splenocytes of all mice with regressing, but not progressing tumors following in vitro peptide stimulation; this response was specific for the gp70 AH-1 peptide SPSYVYHQF and correlated with IFN-gamma, but not IL-4 cytokine production. Depletion of CD8(+) T cells from regressor splenocytes before in vitro stimulation with the relevant peptide abolished their cytolytic activity, while depletion of CD4(+) T cells only partially inhibited CTL generation. Tumor regression induced by DISC/mGM-CSF virus immunotherapy provides a unique model for evaluating the immune mechanism(s) involved in tumor rejection, upon which tumor immunotherapy regimes may be based.

Production of high titre disabled infectious single cycle (DISC) HSV from a microcarrier culture

Disabled Infectious Single Cycle (DISC) HSV-2 has been cultured in the complimentary cell line CR2 to provide high titre bulk material suitable for the purification of the virus as a live viral vaccine. CR2 cells are cultured on the microcarrier Cytodex-1 at 5 g l-1 in small scale (1 l) and larger scale (15 l) reactors. The cells are infected at an MOI of 0.01 pfu cell-1 and the culture harvested 60–72 h later. The infected cells are removed from the microcarriers by the addition of a hypotonic saline and the virus released by low-pressure disruption techniques. Virus titres achieved are compared to the standard roller bottle process. The resulting material is the starting point for the purification of the DISC-HSV virus.

Disabled infectious single cycle (DISC) herpes simplex virus as a vector for immunotherapy of cancer.

Although the idea of immunotherapy for cancer is not new, recent advances in gene delivery systems and the discovery of new immunomodulatory genes has meant that the field is currently extremely active [1]. The delivery of genes which can modify the host’s response to its own tumour cells has been carried out both by using viral vectors and by non-viral delivery systems. In addition the genes have been delivered both directly to the tumours in vivo [2], or, more commonly, to tumour cells ex vivo, which are then re-injected into the tumour-bearing host [3]. There are two key features which may bear on the success of such approaches to the immunotherapy of cancer. Firstly the choice of immunomodulatory gene. Although there are a very large number of possible genes to test, and even larger number of potential combinations of genes, most reported work has concentrated on one or two key genes, principally cytokines such as IL-2 and GM-CSF. The second key element of the approach, and the subject of this article, is the choice of delivery system.KeywordsGenital HerpesSuicide GenePrimary Tumour CellAcute Lymphocytic LeukaemiaUnited Kingdom IntroductionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

A genetically inactivated herpes simplex virus type 2 (HSV-2) vaccine provides effective protection against primary and recurrent HSV-2 disease.

A glycoprotein H (gH)-deleted herpes simplex virus type 2 (HSV-2) was evaluated as a vaccine for the prevention of HSV-induced disease. This virus, which we term a DISC (disabled infectious single cycle) virus, can only complete one replication cycle in normal cells and should thus be safe yet still able to stimulate broad humoral and cell-mediated antiviral immune responses. A gH-deleted HSV-2 virus that has been tested as a vaccine in the guinea pig model of recurrent HSV-2 infection was constructed. Animals vaccinated with DISC HSV-2 showed complete protection against primary HSV-2–induced disease, even when challenged 6 months after vaccination. In addition, the animals were almost completely protected against recurrent disease. Even at low vaccination doses, there was a high degree of protection against primary disease. A reduction in recurrent disease symptoms was also observed following therapeutic vaccination of animals already infected with wild type HSV-2.

Protective vaccination against primary and recurrent disease caused by herpes simplex virus (HSV) type 2 using a genetically disabled HSV-1.

The vaccine potential of a mutant herpes simplex virus (HSV) type 1, with a deletion in the glycoprotein H (gH) gene, was evaluated. The virus requires a gH-expressing cell line for multi-cycle growth but can complete a single cycle of infection in noncomplementing cells. Such viruses, termed DISC (disabled infectious single cycle) viruses, should be safe, yet still able to stimulate humoral and cell-mediated responses against a broad range of virus antigens in vaccinated hosts. Prophylactic vaccination of guinea pigs with DISC HSV-1, by ear scarification or direct infection of the vaginal mucosa, afforded a high degree of protection against HSV-2-induced primary genital disease and reduced significantly the frequency of subsequent disease recurrence. There was also a trend toward reduced recurrence following therapeutic vaccination of animals already infected with HSV-2. DISC HSV vaccination, therefore, offers an effective route for control of HSV disease.