Humoral and cellular immune responses to herpes simplex virus-2 glycoprotein D generated by facilitated DNA immunization of mice

Predominance of herpes simplex virus type 1 from patients with genital herpes in Nova Scotia

The epidemiology of genital herpes is changing with evidence to suggest an increasing incidence of herpes simplex virus type 1 (HSV-1) infections. The results of 6529 HSV genital cultures taken between April 1998 and December 2001 were reviewed. overall, HSV-1 was recovered more often than HSV-2; 1213 versus 1045. This trend was particularly striking in young women 30 years of age or less, in whom 70.8% of isolates were HSV-1. In men of the same age range, 45% of isolates were HSV-1. The proportion of women with HSV-1 declined from 73.7% in those younger than 31 years of age to 4.5% in those older than 60 years of age.These observations have important implications. The decline in the relative proportion of HSV-1 isolates from young adults may be the result of changing sexual practices, changing susceptibility or increased exposure to HSV-1 during vaginal intercourse. In this setting HSV-2 vaccines may be less likely to produce the desired reduction in the overall prevalence of genital herpes infections.

Phase I study of a herpes simplex virus type 2 (HSV-2) DNA vaccine administered to healthy, HSV-2-seronegative adults by a needle-free injection system

We conducted a double-blind, vehicle-controlled, dose escalation safety and immunogenicity trial of a candidate herpes simplex virus type 2 (HSV-2) surface glycoprotein D2 (gD2) DNA vaccine administered by use of a needle-free device. Sixty-two healthy adults were randomized using a 4:1 vaccine-to-placebo ratio. Half of the participants were HSV-1 seronegative, and all were HSV-2 seronegative. Vaccine doses included 100 microg, 300 microg, 1,000 microg or 3,000 microg of a plasmid expressing the gD2 protein. Subjects received vaccine at 0, 4, 8, and 24 weeks. Some subjects received an additional 1,000-microg boost at 52 weeks. We found that the vaccine was safe and well tolerated, with most adverse events being local site reactions. No dose-limiting toxicities were observed. gD2-specific cytotoxic T-lymphocyte and lymphoproliferation responses were detected 2 weeks after the third vaccine injection in one of four HSV-1-seronegative, HSV-2-seronegative participants who received 3,000 microg of vaccine. A DNA-based vaccination strategy against HSV-2 appears to be safe and may generate a vaccine-specific cellular immune response, but high vaccine doses are likely needed to elicit an immune response in most vaccinees.

Pediatrics and herpes simplex virus vaccines

This review explores the development of prophylactic genital herpes vaccines and their potential impact on perinatal and oral-facial disease. Vaccine strategies have included the use of whole killed virus, viral subunits, attenuated live virus, viral vectors, and bare DNA. To date, the recombinant subunit vaccine, truncated HSV-2 gD and alum/MPL, has been the most efficacious. The vaccine is 73 to 74 percent effective in preventing genital disease in herpes simplex virus seronegative women but is not effective in men or seropositive women. Models predict a significant impact on genital herpes if it limits viral shedding. Reductions in perinatal and oral-facial disease are likely to occur as well. Once an efficacious herpes vaccine is available, its effectiveness will depend ultimately on vaccine acceptance by professional organizations, healthcare professionals, and parents. Further research is required to improve on and fully understand the implications of prophylactic herpes simplex vaccines.

DNA vaccines encoding interleukin-8 and RANTES enhance antigen-specific Th1-type CD4(+) T-cell-mediated protective immunity against herpes simplex virus type 2 in vivo

Chemokines are inflammatory molecules that act primarily as chemoattractants and as activators of leukocytes. Their role in antigen-specific immune responses is of importance, but their role in disease protection is unknown. Recently it has been suggested that chemokines modulate immunity along more classical Th1 and Th2 phenotypes. However, no data currently exist in an infectious challenge model system. We analyzed the modulatory effects of selected chemokines (interleukin-8 [IL-8], gamma interferon-inducible protein 10 [IP-10], RANTES, monocyte chemotactic protein 1 [MCP-1], and macrophage inflammatory protein 1 alpha [MIP-1 alpha]) on immune phenotype and protection against lethal challenge with herpes simplex virus type 2 (HSV-2). We observed that coinjection with IL-8 and RANTES plasmid DNAs dramatically enhanced antigen-specific Th1 type cellular immune responses and protection from lethal HSV-2 challenge. This enhanced protection appears to be mediated by CD4(+) T cells, as determined by in vitro and in vivo T-cell subset deletion. Thus, IL-8 and RANTES cDNAs used as DNA vaccine adjuvants drive antigen-specific Th1 type CD4(+) T-cell responses, which result in reduced HSV-2-derived morbidity, as well as reduced mortality. However, coinjection with DNAs expressing MCP-1, IP-10, and MIP-1 alpha increased mortality in the challenged mice. Chemokine DNA coinjection also modulated its own production as well as the production of cytokines. These studies demonstrate that chemokines can dominate and drive immune responses with defined phenotypes, playing an important role in the generation of protective antigen-specific immunity.

Interleukin 7 can enhance antigen-specific cytotoxic-T-lymphocyte and/or Th2-type immune responses in vivo

Interleukin 7 (IL-7) protein has been reported to be important in the development of cytotoxic-T-lymphocyte (CTL) responses. However, other studies also support a partial Th2 phenotype for this cytokine. In an effort to clarify this unusual conflict, we compared IL-7 along with IL-12 (Th1 control) and IL-10 (Th2 control) for its ability to induce antigen (Ag)-specific CTL and Th1- versus Th2-type immune responses using a well established DNA vaccine model. In particular, IL-7 codelivery showed a significant increase in immunoglobulin G1 (IgG1) levels compared to IgG2a levels. IL-7 coinjection also decreased production of Th1-type cytokine IL-2, gamma interferon, and the chemokine RANTES but increased production of the Th2-type cytokine IL-10 and the similarly biased chemokine MCP-1. In herpes simplex virus (HSV) challenge studies, IL-7 coinjection decreased the survival rate after lethal HSV type 2 (HSV-2) challenge compared with gD plasmid vaccine alone in a manner similar to IL-10 coinjection, whereas IL-12 coinjection enhanced the protection, further supporting that IL-7 drives immune responses to the Th2 type, resulting in reduced protection against HSV-2 challenge. Moreover, coinjection with human immunodeficiency virus type 1 env and gag/pol genes plus IL-12 or IL-7 cDNA enhanced Ag-specific CTLs, while coinjection with IL-10 cDNA failed to influence CTL induction. Thus, IL-7 could drive Ag-specific Th2-type cellular responses and/or CTL responses. These results support that CTLs could be induced by IL-7 in a Th2-type cytokine and chemokine environment in vivo. This property of IL-7 allows for an alternative pathway for CTL development which has important implications for host-pathogen responses.

Protective immune correlates can segregate by vaccine type in a murine herpes model system

A central tenet of vaccine development is to identify immune correlates of protection. Both plasmid-encoded gD as well as recombinant protein gD can protect mice from lethal herpes simplex virus (HSV) challenge. It is known that different vaccine modalities should induce different immune phenotypes. Yet, paradoxically, it is also thought that the basis for protection should rely on exploitation of vulnerabilities of the pathogen and therefore that the overlapping properties of these different vaccines would reveal insight into common immune mechanisms responsible for protection. We sought to investigate this question by comparing two different vaccine modalities in the HSV-2 mouse model. We observed that gD protein was a strong inducer of T(h)2-type immune responses, and overall antibody titers of IgG, IgE and IgA were significantly higher than those induced by plasmid gD vaccines. In contrast, the plasmid gD vaccine induced a strong T(h)1 bias. Following high-dose challenge the gD protein was most effective at providing protection. However, at lower lethal dose challenge, while both vaccines were protective with regards to survival, only the plasmid-vaccinated animals were protected from HSV-2 infection-induced morbidity. These studies suggest that these different vaccine modalities induce protection through unique non-overlapping mechanisms, supporting that vaccine correlates are associated with the types of immunogen rather than solely the pathogen.

Potential for plasmid DNAs as vaccines for the new millennium

The advent of new technology and the unmet needs of old and new epidemics of infectious diseases have stimulated a new era of vaccinology. One of the most novel approaches employs plasmid DNA engineered to express one or more genes of the pathogen in mammalian cells. Plasmids may also express cytokine or costimulatory molecules to 'direct' the immune response and/or express altered forms of the antigen to direct it to a specific intracellular compartment or a specific extracellular receptor. The quality of immune responses generated by DNA vaccines in animals has previously only been equaled by live attenuated viral vaccines. The immune stimulating activity of DNA vaccines, combined with their versatility, suggests vast potential for these vaccines.

IL-12 Gene as a DNA Vaccine Adjuvant in a Herpes Mouse Model: IL-12 Enhances Th1-Type CD4+ T Cell-Mediated Protective Immunity Against Herpes Simplex Virus-2 Challenge

IL-12 has been shown to enhance cellular immunity in vitro and in vivo. Recent reports have suggested that combining DNA vaccine approach with immune stimulatory molecules delivered as genes may significantly enhance Ag-specific immune responses in vivo. In particular, IL-12 molecules could constitute an important addition to a herpes vaccine by amplifying specific immune responses. Here we investigate the utility of IL-12 cDNA as an adjuvant for a herpes simplex virus-2 (HSV-2) DNA vaccine in a mouse challenge model. Direct i.m. injection of IL-12 cDNA induced activation of resting immune cells in vivo. Furthermore, coinjection with IL-12 cDNA and gD DNA vaccine inhibited both systemic gD-specific Ab and local Ab levels compared with gD plasmid vaccination alone. In contrast, Th cell proliferative responses and secretion of cytokines (IL-2 and IFN-γ) and chemokines (RANTES and macrophage inflammatory protein-1α) were significantly increased by IL-12 coinjection. However, the production of cytokines (IL-4 and IL-10) and chemokine (MCP-1) was inhibited by IL-12 coinjection. IL-12 coinjection with a gD DNA vaccine showed significantly better protection from lethal HSV-2 challenge compared with gD DNA vaccination alone in both inbred and outbred mice. This enhanced protection appears to be mediated by CD4+ T cells, as determined by in vivo CD4+ T cell deletion. Thus, IL-12 cDNA as a DNA vaccine adjuvant drives Ag-specific Th1 type CD4+ T cell responses that result in reduced HSV-2-derived morbidity as well as mortality.

Control of STDs--the role of prophylactic vaccines against herpes simplex virus

OBJECTIVES

To summarise the current status of genital herpes simplex virus (HSV) vaccine development and provide a discussion of the potential benefits and limitations of genital herpes vaccines.

METHODS

Literature review.

RESULTS

Genital herpes simplex virus infection has a complex pathogenesis that has contributed to it becoming a serious worldwide problem. In an attempt to control the problem five different types of genital herpes vaccines have been developed. These include inactivated virion derived vaccines, adjuvanted subunit vaccines, vectored vaccines, replication limited live viral vaccines, genetically attenuated live viral vaccines, and nucleic acid vaccines. While available commercially in some parts of the world, inactivated virion derived vaccines have not been proved effective. Of the others, adjuvanted subunit vaccines, replication limited live viral vaccines, and nucleic acid vaccines are currently in clinical trials and vectored vaccines and genetically attenuated live viral vaccines are in preclinical development.

CONCLUSION

With regard to HSV vaccines in general, it is reasonable to expect that the newer vaccines may protect the individual from developing symptomatic genital herpes but may not protect against asymptomatic viral infection. With widespread use HSV vaccines might help to prevent the spread of genital herpes.

Enhancement of protective humoral (Th2) and cell-mediated (Th1) immune responses against herpes simplex virus-2 through co-delivery of granulocyte-macrophage colony-stimulating factor expression cassettes

Granulocyte-macrophage colony-stimulating factor (GM-CSF) could in theory attract antigen-presenting cells in muscle following intramuscular DNA immunization, resulting in enhanced antigen-specific immune responses. Thus, such adjuvants could constitute an important addition to a herpes vaccine by amplifying specific immune responses. Here we investigate the utility of GM-CSF cDNA as a vaccine adjuvant for herpes simplex virus (HSV)-2 in a mouse challenge model. GM-CSF cDNA co-injection enhanced levels of specific IgG, IgE and IgA against HSV-2 gD protein significantly higher than gD plasmid vaccination alone. Moreover, GM-CSF co-injection induced a dramatic increase in IgG1 levels, as compared to IgG2a levels, suggesting a Th2 bias in the response. T helper cell proliferation and secretion of cytokines (IL-2 and IFN-gamma) were significantly increased by GM-CSF cDNA co-injection. When challenged with a lethal dose of HSV-2, GM-CSF co-injection increased survival rates to 90%, an improvement as compared to gD vaccination alone (60-63%). Furthermore, GM-CSF cDNA co-injection reduced herpetic lesions and resulted in a faster recovery from lesions. These data indicate that GM-CSF cDNA enhances both humoral and cellular immune responses and enhances vaccine efficacy, resulting in reduced HSV-2-derived morbidity as well as mortality.