Modulation of mucosal and systemic immunity by enteric administration of nonreplicating herpes simplex virus expressing cytokines

Response to HIV-1 gp160-carrying recombinant virus HSV-1 and HIV-1 VLP combined vaccine in BALB/c mice

Human immunodeficiency virus (HIV) induced AIDS causes a large number of infections and deaths worldwide every year, still no vaccines are available to prevent infection. Recombinant herpes simplex virus type 1 (HSV-1) vector-based vaccines coding the target proteins of other pathogens have been widely used for disease control. Here, a recombinant virus with HIV-1 gp160 gene integration into the internal reverse (IR) region-deleted HSV-1 vector (HSV-BAC), was obtained by bacterial artificial chromosome (BAC) technology, and its immunogenicity investigated in BALB/c mice. The result showed similar replication ability of the HSV-BAC-based recombinant virus and wild type. Furthermore, humoral and cellular immune response showed superiority of intraperitoneal (IP) administration, compared to intranasally (IN), subcutaneous (SC) and intramuscularly (IM), that evidenced by production of significant antibody and T cell responses. More importantly, in a prime-boost combination study murine model, the recombinant viruses prime followed by HIV-1 VLP boost induced stronger and broader immune responses than single virus or protein vaccination in a similar vaccination regimen. Antibody production was sufficient with huge potential for viral clearance, along with efficient T-cell activation, which were evaluated by the enzyme-linked immunosorbent assay (ELISA) and flow cytometry (FC). Overall, these findings expose the value of combining different vaccine vectors and modalities to improve immunogenicity and breadth against different HIV-1 antigens.

Efficacy of an HSV-1 Neuro-Attenuated Vaccine in Mice Is Reduced by Preventing Viral DNA Replication

We previously isolated an HSV-1 mutant, KOS-NA, that contains two non-synonymous mutations in UL39. One of the mutations, resulting in an R950H amino acid substitution in ICP6, renders KOS-NA severely neuro-attenuated and significantly reduces HSV-1 latency. Vaccination of mice with KOS-NA prior to corneal challenge provides significant protection against HSV-1-mediated eye diseases even at a very low immunizing dose, indicating its utility as a vaccine scaffold. Because KOS-NA contains a neuro-attenuating mutation in a single gene, we sought to improve its safety by deleting a portion of the UL29 gene whose protein product, ICP8, is essential for viral DNA replication. Whereas KOS-NA reduced replication of HSV-1 challenge virus in the corneal epithelium and protected mice against blepharitis and keratitis induced by the challenge virus, KOS-NA/8- and an ICP8- virus were significantly less efficacious except at higher doses. Our results suggest that the capacity to replicate, even at significantly reduced levels compared with wild-type HSV-1, may be an important feature of an effective vaccine. Means to improve safety of attenuated viruses as vaccines without compromising efficacy should be sought.

Effect of herpes simplex virus vector-mediated interleukin-4 gene therapy on bladder overactivity and nociception

We investigated the effects of replication-defective herpes simplex virus (HSV) vector expression of interleukin-4 (IL-4) on bladder overactivity and nociception. HSV vector expressing murine interleukin-4 (S4IL4) or the control vector expressing β-galactosidase (SHZ) were injected to the rat bladder wall. At 1 week after viral injection, in cystometry performed under urethane anesthesia, the S4IL4-treated group did not show the intercontraction intervals reduction during intravesical administration of 10 nM resiniferatoxin (RTx). At 2 weeks after viral injection, behavioral studies were performed on vector-injected animals in an awakened state. Freezing behavior induced by 3 μM RTx, administered for 1 min into the bladder, was significantly suppressed in the S4IL4 group compared with the SHZ group. Murine IL-4 levels examined by ELISA were significantly increased in bladder and bladder afferent dorsal root ganglia at 2 weeks after viral injection. The expression of IL-1β and IL-2 and bladder inflammatory responses were significantly suppressed in the RTx-irritated bladder of S4IL4-injected rats. These results indicate that HSV vector-mediated interleukin-4 expression in the bladder and bladder afferent pathways reduces the inflammatory response, bladder overactivity and nociceptive behavior induced by bladder irritation in the rat model. Therefore, IL-4 gene therapy could be a new strategy for treating urinary frequency and/or bladder pain.

Immunization with a dominant-negative recombinant Herpes Simplex Virus (HSV) type 1 protects against HSV-2 genital disease in guinea pigs

Background

CJ9-gD is a novel dominant-negative recombinant herpes simplex virus type 1 (HSV-1) that is completely replication-defective, cannot establish detectable latent infection in vivo, and expresses high levels of the major HSV-1 antigen glycoprotein D immediately following infection. In the present study, CJ9-gD was evaluated as a vaccine against HSV-2 genital infection in guinea pigs.

Results

Animals immunized with CJ9-gD developed at least 700-fold higher titers of HSV-2-specific neutralization antibodies than mock-immunized controls. After challenge with wild-type HSV-2, all 10 control guinea pigs developed multiple genital lesions with an average of 21 lesions per animal. In contrast, only 2 minor lesions were found in 2 of 8 CJ9-gD-immunized animals, representing a 40-fold reduction on the incidence of primary genital lesions in immunized animals (p < 0.0001). Immunization significantly reduced the amount and duration of viral shedding and provided complete protection against neurological symptoms, while 90% of mock-immunized animals succumbed due to the severity of disease. Importantly, immunized animals showed no signs of recurrent disease or viral shedding during a 60-days observation period after recovery from primary infection, and carried 50-fold less latent viral DNA load in their dorsal root ganglia than the surviving mock-vaccinated controls (p < 0.0001).

Conclusions

Collectively, we demonstrate that vaccination with the HSV-1 recombinant CJ9-gD elicits strong and protective immune responses against primary and recurrent HSV-2 genital disease and significantly reduces the extent of latent infection.

Anionic liposomes increase the efficiency of adenovirus-mediated gene transfer to coxsackie-adenovirus receptor deficient cells

Despite remarkable progress in the research of both viral and nonviral gene delivery vectors, the drawbacks in each delivery system have limited their clinical applications. Therefore, one of the concepts for developing novel vectors is to overcome the limitations of individual vectors by combining them. In the current study, adenoviral vectors were formulated with anionic liposomes to protect them from neutralizing antibodies and to improve their transduction efficiency in Coxsackievirus-adenovirus receptor (CAR) deficient cells. A calcium-induced phase change method was applied to encapsulate adenovirus 5 (Ad5) into anionic liposomes to formulate the complexes of Ad5 and anionic liposomes (Ad5-AL). Meanwhile, the complexes of Ad5 and cationic liposomes (Ad5-CL) were also prepared as controls. LacZ gene expression in CAR overexpressing cells (A549) and CAR deficient cells (CHO and MDCK) was measured by either qualitative or quantitative detection. Confocal laser scanning microscopy was performed to determine intracellular location of Ad5 after their infection. Human sera with a high titer of antiadenovirus antibody were used to assess the neutralizing antibody protection ability of the complexed vectors. Accompanying the enhanced gene expression, a high ability to introduce Ad5 into cytoplasm and nucleus mediated by Ad5-AL was also observed in CAR deficient cells. Additionally, antibody neutralizing assay indicated that neutralizing serum inhibited naked Ad5 and Ad5-CL at rather higher dilution than Ad5-AL, which demonstrated Ad5-AL was more capable of protecting Ad5 from neutralizing than Ad5-CL. In conclusion, anionic liposomes prepared by the calcium-induced phase change method could significantly enhance the transduction ability of Ad5 in CAR deficient cells.

Replication-deficient mutant Herpes Simplex Virus-1 targets professional antigen presenting cells and induces efficient CD4+ T helper responses

Both neutralizing antibodies and cytotoxic T-cells are necessary to control a viral infection. However, vigorous T helper responses are essential for their elicitation and maintenance. Here we show that a recombinant replication-deficient Herpes Simplex Virus (HSV)-1 vector encoding the Human Immunodeficiency Virus (HIV)-1 matrix protein p17 (T0-p17) was capable of infecting professional antigen presenting cells (APCs) in vitro and in vivo. The injection of T0-p17 in the mouse dermis generated a strong p17-specific CD4+ T helper response preceding both p17-specific humoral and effector T cell responses. Moreover, we show that T0-p17 infection did not interfere with the endogenous processing of the transgene encoded antigen, since infected APCs were able to evoke a strong recall response in vitro. Our results demonstrate that replication-deficient HSV vectors can be appealing candidates for the development of vaccines able to trigger T helper responses.

Expression of human immunodeficiency virus type 1 tat from a replication-deficient herpes simplex type 1 vector induces antigen-specific T cell responses

Herpes simplex type-1 virus (HSV-1) based vectors have been widely used in different gene therapy approaches and also as experimental vaccines against HSV-1 infection. Recent advances in the HSV-1 technology do support the use of replication defective HSV-1 as vaccine vectors for delivery of foreign antigens. We have examined the ability of a recombinant replication-defective HSV-1 vector expressing the HIV-1 Tat protein to induce long-term Tat-specific immune responses in the Balb/c murine model. The results showed that vector administration by the subcutaneous route elicits anti-Tat specific T-cell mediated immune responses in mice characterized by the presence of the Tat-specific cytotoxic activity and production of high levels of IFN-gamma.

HSV-mediated expression of interleukin-4 in dorsal root ganglion neurons reduces neuropathic pain

BACKGROUND

To examine the role of inflammatory mediators in neuropathic pain, we used a replication-defective genomic herpes simplex virus (HSV)-based vector containing the coding sequence for the anti-inflammatory peptide interleukin (IL)-4 under the transcriptional control of the HSV ICP4 immediate early promoter, vector S4IL4, to express IL-4 in dorsal root ganglion (DRG) neurons in vivo.

RESULTS

Subcutaneous inoculation of S4IL4 in the foot transduced lumbar DRG to produce IL-4. Transgene-mediated expression of IL-4 did not alter thermal latency or tactile threshold in normal animals, but inoculation of S4IL4 1 week after spinal nerve ligation (SNL) reduced mechanical allodynia and reversed thermal hyperalgesia resulting from SNL. Inoculation of S4IL4 1 week before SNL delayed the development of thermal hyperalgesia and tactile allodynia, but did not prevent the ultimate development of these manifestations of neuropathic pain. S4IL4 inoculation suppressed non-noxious-induced expression of c-Fos immunoreactivity in dorsal horn of spinal cord and reversed the upregulation of spinal IL-1beta, PGE2, and phosphorylated-p38 MAP kinase, characteristic of neuropathic pain.

CONCLUSION

HSV-mediated expression of IL-4 effectively reduces the behavioral manifestations of neuropathic pain, and reverses some of the biochemical and histologic correlates of neuropathic pain at the spinal level.

Development and application of replication-incompetent HSV-1-based vectors

The replication-incompetent HSV-1-based vectors are herpesviruses in which genes that are 'essential' for viral replication have been either mutated or deleted. These deletions have substantially reduced their cytotoxicity by preventing early and late viral gene expression and, together with other deletions involving 'nonessential' genes, have also created space to introduce distinct and independently regulated expression cassettes for different transgenes. Therapeutic effects in gene therapy applications requiring simultaneous and synergic expression of multiple gene products are easily achievable with these vectors. A number of different HSV-1-based nonreplicative vectors for specific gene therapy applications have been developed so far. They have been tested in different gene therapy animal models of neuropathies (Parkinson's disease, chronic pain, spinal cord injury pain) and lysosomal storage disorders. Many replication-incompetent HSV-1-based vectors have also been used either as potential anti-herpes vaccines, as well as vaccine vectors for other pathogens in murine and simian models. Anticancer gene therapy approaches have also been successfully set up; gene therapy to other targets by using these vectors is feasible.

Protection from bacterial infection by a single vaccination with replication-deficient mutant herpes simplex virus type 1

Adaptive immune responses in which CD8(+) T cells recognize pathogen-derived peptides in the context of major histocompatibility complex class I molecules play a major role in the host defense against infection with intracellular pathogens. Cells infected with intracellular bacteria such as Listeria monocytogenes, Salmonella enterica serovar Typhimurium, or Mycobacterium tuberculosis are directly lysed by cytotoxic CD8(+) T cells. For this reason, current vaccines for intracellular pathogens, such as subunit vaccines or viable bacterial vaccines, aim to generate robust cytotoxic T-cell responses. In order to investigate the capacity of a herpes simplex virus type 1 (HSV-1) vector to induce strong cytotoxic effector cell responses and protection from infection with intracellular pathogens, we developed a replication-deficient, recombinant HSV-1 (rHSV-1) vaccine. We demonstrate in side-by-side comparison with DNA vaccination that rHSV-1 vaccination induces very strong CD8(+) effector T-cell responses. While both vaccines provided protection from infection with L. monocytogenes at low, but lethal doses, only rHSV-1 vaccines could protect from higher infectious doses; HSV-1 induced potent memory cytotoxic T lymphocytes that, upon challenge by pathogens, efficiently protected the animals. Despite the stimulation of relatively low humoral and CD4-T-cell responses, rHSV-1 vectors are strong candidates for future vaccine strategies that confer efficient protection from subsequent infection with intracellular bacteria.

Vaccines against genital herpes: progress and limitations

Herpes simplex viruses (HSV) cause lifelong persistent infections with numerous disease manifestations. Genital herpes infections are widespread in populations throughout the world and a vaccine to protect against or subdue established genital herpes infections has been under development for decades. Vaccine-mediated protection against persistent viral infections can be extremely difficult to achieve. The more rapidly a virus reaches its target tissue for persistence, the more vigorously a vaccine-induced immune response must defend the vaccinated individual. After exposure to HSV through sexual contact, only a few days are required for the virus to establish latent infection of its host. Despite numerous improvements, traditional vaccine approaches of whole virus or protein subunits have met with only marginal success. The many disappointments have heightened interest in determining correlates of immune protection, studies pursued both in animal models and in humans. They have also led to reassessment of the goals of vaccination. Necessity has sparked several creative new vaccine approaches involving nucleic acid or live attenuated viruses and vectors. With improved concepts of protective immune responses has come fervent discussion of the means to stimulate and maintain cell-mediated immunity. The result of this work is likely to be a more thorough understanding of antiviral immunity in the genital mucosa and the nervous system, and of HSV pathogenesis and immune evasion strategies, as additional strides are taken toward the goal of a successful vaccine with which to confront HSV.

Expression of immunomodulating molecules by recombinant viruses: can the immunogenicity of live virus vaccines be improved?

Several obstacles exist for the development and use of live attenuated vaccines, including difficulty in achieving a proper balance between attenuation of viral replication and immunogenicity; inducing a strong T-helper 1 response in early life when the immune system is T helper 2 biased and immunization is sometimes associated with immunopathology and the immunosuppressive effect of maternal antibodies in infants. For some viral infections, the immune response to natural infection does not confer solid protection, complicating the task of vaccine development. The development of methods for generation of recombinant viruses provided new opportunities for improving the immunogenicity of live virus vaccine candidates, including the construction of viruses that express cytokines or other immunomodulating molecules. Depending on the choice of immunomodulating molecule, various stages of the immune response can be affected, such as antigen presentation or T-cell proliferation and differentiation. In addition to using the approach for development of viral live attenuated vaccines, it is currently being explored for the development of antitumor vaccines. For this type of vaccine, expression of tumor antigens and one or more immunomodulating molecules by one or several recombinant viruses has been proposed.

Cytokines in experimental herpes simplex virus infection

Herpes simplex virus (HSV) causes productive and latent forms of infection in humans and experimental animals. The primary infection and reactivation of the latent infection evoke an immune response in the host organism, involving activities of macrophages, CD4+ and CD8+ lymphocytes, and B lymphocytes. Strong cytokine responses are associated with the acute and recurrent phases of HSV infection. Also, during the latent phase of HSV infection in the sensory ganglia, expression of certain cytokines can be detected. The cytokine response to HSV infection is dominated by proinflammatory and Th1 type cytokines; however, Th2 type cytokines such as interleukin-4 also are expressed in the infected tissue. The use of novel HSV-derived, cytokine-expressing gene therapy vectors necessitates studies on the possible modulation of the host responses by the virus-encoded cytokine transgenes. This review focuses on the roles of certain Th1 and Th2 type cytokines in different phases of the experimental HSV infections.

Development of HSV-specific CD4+ Th1 responses and CD8+ cytotoxic T lymphocytes with antiviral activity by vaccination with the HSV-2 mutant ICP10DeltaPK

A growth compromised herpes simplex virus type 2 (HSV-2) mutant which is deleted in the PK domain of the large subunit of ribonucleotide reductase (ICP10DeltaPK) protects from HSV-2 challenge in the mouse and guinea pig cutaneous and vaginal models and reduces the incidence and frequency of recurrent disease (Vaccine (17) (1999) 1951; Vaccine (19) (2001) 1879). The present studies were designed to identify the immune responses induced by ICP10DeltaPK and define the component responsible for protective activity. We found that ICP10DeltaPK elicits a predominant HSV-specific T helper type 1 (Th1) response, as evidenced by: (1) higher levels of HSV-specific IgG2a (Th1) than IgG1 (Th2) isotypes and (2) higher numbers of CD4+ IFN-gamma than IL-10 secreting T cells in popliteal lymph nodes. This Th1 response pattern was associated with a significant increase in the levels of IL-12 produced by dendritic cells from ICP10DeltaPK than HSV-2 immunized animals. Lymph node cells (LNCs) from ICP10DeltaPK immunized mice had significantly higher levels of HSV-2 specific cytolytic activity than LNCs from mice immunized with HSV-2 and it was mediated by CD8+ T cells. CD8+ CTL were not seen in LNCs from HSV-2 immunized mice. In adoptive transfer experiments, CD8+ T cells and, to a lower extent, CD4+ T cells from ICP10DeltaPK immunized mice inhibited HSV-2 replication, suggesting that they are involved in the protective immunity induced by ICP10DeltaPK vaccination.

Herpes simplex virus vectors elicit durable immune responses in the presence of preexisting host immunity

Herpes simplex virus (HSV) recombinants are being developed as vaccine vectors for the expression of heterologous antigens. There is concern, however, that preexisting HSV immunity may decrease their effectiveness. We have addressed this issue in an animal model. Immunized mice were inoculated with a replication-defective HSV-1 vector that expressed the Escherichia coli beta-galactosidase protein as a model antigen. We assessed vector efficacy by analyzing the immunoglobulin G (IgG) antibody response and cellular proliferative response directed against beta-galactosidase. We report that the ability of the vector to induce antibody or proliferative responses was not diminished by preexisting immunity to HSV. Of further note, the anti-HSV and anti-beta-galactosidase IgG responses following vector administration were extremely durable in both immunized and naive mice. These results indicate that the ability of a replication-defective HSV-derived vaccine vector to elicit long-lived immune responses in mice is not impaired by prior HSV exposure.

Intrathecal delivery of IFN-gamma protects C57BL/6 mice from chronic-progressive experimental autoimmune encephalomyelitis by increasing apoptosis of central nervous system-infiltrating lymphocytes

The exclusive detrimental role of proinflammatory cytokines in demyelinating diseases of the CNS, such as multiple sclerosis, is controversial. Here we show that the intrathecal delivery of an HSV-1-derived vector engineered with the mouse IFN-gamma gene leads to persistent (up to 4 wk) CNS production of IFN-gamma and inhibits the course of a chronic-progressive form of experimental autoimmune encephalomyelitis (EAE) induced in C57BL/6 mice by myelin oligodendrocyte glycoprotein (MOG)(35-55). Mice treated with the IFN-gamma-containing vector before EAE onset showed an earlier onset but a milder course of the disease compared with control mice treated with the empty vector. In addition, 83% of IFN-gamma-treated mice completely recovered within 25 days post immunization, whereas control mice did not recover up to 60 days post immunization. Mice treated with the IFN-gamma-containing vector within 1 wk after EAE onset partially recovered from the disease within 25 days after vector injection, whereas control mice worsened. Recovery from EAE in mice treated with IFN-gamma was associated with a significant increase of CNS-infiltrating lymphocytes undergoing apoptosis. During the recovery phase, the mRNA level of TNFR1 was also significantly increased in CNS-infiltrating cells from IFN-gamma-treated mice compared with controls. Our results further challenge the exclusive detrimental role of IFN-gamma in the CNS during EAE/multiple sclerosis, and indicate that CNS-confined inflammation may induce protective immunological countermechanisms leading to a faster clearance of encephalitogenic T cells by apoptosis, thus restoring the immune privilege of the CNS.

Inflammation and clearance of Chlamydia trachomatis in enteric and nonenteric mucosae

Immunization(s) fostering the induction of genital mucosa-targeted immune effectors is the goal of vaccines against sexually transmitted diseases. However, it is uncertain whether vaccine administration should be based on the current assumptions about the common mucosal immune system. We investigated the relationship between mucosal sites of infection, infection-induced inflammation, and immune-mediated bacterial clearance in mice using the epitheliotropic pathogen Chlamydia trachomatis. Chlamydial infection of the conjunctival, pulmonary, or genital mucosae stimulated significant changes in tissue architecture with dramatic up-regulation of the vascular addressin, VCAM, a vigorous mixed-cell inflammatory response with an influx of alpha4beta1+ T cells, and clearance of bacteria within 30 days. Conversely, intestinal mucosa infection was physiologically inapparent, with no change in expression of the local MAdCAM addressin, no VCAM induction, no histologically detectable inflammation, and no tissue pathology. Microbial clearance was complete within 60 days in the small intestine but bacterial titers remained at high levels for at least 8 months in the large intestine. These findings are compatible with the notion that VCAM plays a functional role in recruiting cells to inflammatory foci, and its absence from the intestinal mucosa contributes to immunologic homeostasis at that site. Also, expression of type 1 T cell-mediated immunity to intracellular Chlamydia may exhibit tissue-specific variation, with the rate and possibly the mechanism(s) of clearance differing between enteric and nonenteric mucosae. The implications of these data for the common mucosal immune system and the delivery of vaccines against mucosal pathogens are discussed.

Cytokine gene therapy of autoimmune demyelination revisited using herpes simplex virus type-1-derived vectors

The peripheral delivery of drugs in patients affected by central nervous system (CNS)-confined diseases is therapeutically ineffective due to the presence of the blood-brain barrier which forms an inaccessible wall to the majority of CNS targeting molecules. When molecules with an anti-inflammatory profile have been systemically administered to patients affected by a chronic inflammatory demyelinating disease of the CNS, such as multiple sclerosis (MS), results have been disappointing. A successful therapeutic approach in MS should therefore consider the delivery of anti-inflammatory molecules directly into the CNS in order to inhibit blood-borne CNS-confined mononuclear cells which act as ultimate effector cells directly destroying oligodendrocytes and/or releasing myelinotoxic substances. Biological and physical vectors engineered with heterologous genes coding for immunomodulatory cytokines with an anti-inflammatory profile might represent the appropriate tool to deliver therapeutic genes into the CNS of patients with MS. So far, cytokine gene therapy has never been attempted in MS, but encouraging results have been obtained in the animal model of MS, experimental autoimmune encephalomyelitis (EAE), using viral vectors or plasmids engineered with cytokine genes and then injected systemically, either in the blood stream or circulating encephalitogenic T cells, or into the CNS. Here, we critically discuss the various attempts made in EAE using gene therapy protocols based on the delivery of immunomodulatory cytokine genes. Special emphasis is put on the use of non-replicative herpes simplex type-1 (HSV)-derived vectors engineered with the gene of the immunomodulatory cytokine interleukin (IL)-4.

Immunogenicity of herpes simplex virus type 1 mutants containing deletions in one or more alpha-genes: ICP4, ICP27, ICP22, and ICP0

Replication defective mutants of HSV have been proposed both as vaccine candidates and as vehicles for gene therapy because of their inability to produce infectious progeny. The immunogenicity of these HSV replication mutants, at both qualitative and quantitative levels, will directly determine their effectiveness for either of these applications. We have previously reported (Brehm et al., J. Virol., 71, 3534, 1997) that a replication defective mutant of HSV-1, which expresses a substantial level of viral genes without producing virus particles, is as efficient as wild-type HSV-1 in eliciting an HSV-specific cytotoxic T-lymphocyte (CTL) response. In this report, we have further evaluated the immunogenic potential of HSV-1-derived replication defective mutants by examining the generation of HSV-specific CTL following immunization with viruses that are severely restricted in viral gene expression due to mutations in one or more HSV alpha genes (ICP4, ICP27, ICP22, and ICP0). To measure the CTL responses induced by the HSV alpha-mutants, we have targeted two H-2Kb-restricted CTL epitopes: an epitope in a virion protein, gB (498-505), and an epitope in a nonvirion protein, ribonucleotide reductase (RR1 822-829). The HSV mutants used in this study are impaired in their ability to express gB while a majority of them still express RR1. Our findings demonstrate that a single immunization with these mutants is able to generate a strong CTL response not only to RR1 822-829, but also to gB498-505 despite their inability to express wild-type levels of gB. Furthermore, a single immunization with any individual mutant can also provide immune protection against HSV challenge. These results suggest that mutants which are restricted in gene expression may be used as effective immunogens in vivo.

In vivo modulation of vaccine-induced immune responses toward a Th1 phenotype increases potency and vaccine effectiveness in a herpes simplex virus type 2 mouse model

Several vaccines have been investigated experimentally in the herpes simplex virus type 2 (HSV-2) model system. While it is believed that CD4(+)-T-cell responses are important for protection in general, the correlates of protection from HSV-2 infection are still under investigation. Recently, the use of molecular adjuvants to drive vaccine responses induced by DNA vaccines has been reported in a number of experimental systems. We sought to take advantage of this immunization model to gain insight into the correlates of immune protection in the HSV-2 mouse model system and to further explore DNA vaccine technology. To investigate whether the Th1- or Th2-type immune responses are more important for protection from HSV-2 infection, we codelivered the DNA expression construct encoding the HSV-2 gD protein with the gene plasmids encoding the Th1-type (interleukin-2 [IL-2], IL-12, IL-15, and IL-18) and Th2-type (IL-4 and IL-10) cytokines in an effort to drive immunity induced by vaccination. We then analyzed the modulatory effects of the vaccine on the resulting immune phenotype and on the mortality and the morbidity of the immunized animals following a lethal challenge with HSV-2. We observed that Th1 cytokine gene coadministration not only enhanced the survival rate but also reduced the frequency and severity of herpetic lesions following intravaginal HSV challenge. On the other hand, coinjection with Th2 cytokine genes increased the rate of mortality and morbidity of the challenged mice. Moreover, of the Th1-type cytokine genes tested, IL-12 was a particularly potent adjuvant for the gD DNA vaccination.

Central nervous system delivery of interleukin 4 by a nonreplicative herpes simplex type 1 viral vector ameliorates autoimmune demyelination

Multiple sclerosis (MS) is a T cell-mediated organ-specific inflammatory disease leading to central nervous system (CNS) demyelination. On the basis of results obtained in experimental autoimmune encephalomyelitis (EAE) models, MS treatment by administration of antiinflammatory cytokines such as interleukin 4 (IL-4) is promising but is hampered by the limited access of the cytokines to the CNS and by the pleiotropic effects of systemically administered cytokines. We established a cytokine delivery system within the CNS using non-replicative herpes simplex type 1 (HSV-1) viral vectors engineered with cytokine genes. These vectors injected into the cisterna magna (i.c.) of mice diffuse in all ventricular and subarachnoid spaces and infect with high efficiency the ependymal and leptomeningeal cell layers surrounding these areas, without obvious toxic effects. Heterologous genes contained in the vectors are efficiently transcribed in infected ependymal cells, leading to the production of high amounts of the coded proteins. For example, 4.5 ng of interferon gamma (IFN-gamma) per milliliter is secreted into the cerebrospinal fluid (CSF) up to day 28 postinjection (p.i.) and reaches the CNS parenchyma in bioactive form, as demonstrated by upregulation of MHC class I expression on CNS-resident cells. We then exploited the therapeutic potential of the vectors in EAE mice. An HSV-1-derived vector containing the IL-4 gene was injected i.c. in Biozzi AB/H mice at the time of EAE induction. We found the following in treated mice: (1) delayed EAE onset, (2) a significant decrease in clinical score, (3) a significant decrease in perivascular inflammatory infiltrates and in the number of macrophages infiltrating the CNS parenchyma and the submeningeal spaces, and (4) a reduction in demyelinated areas and axonal loss. Peripheral T cells from IL-4-treated mice were not affected either in their antigen-specific proliferative response or in cytokine secretion pattern. Our results indicate that CNS cytokine delivery with HSV-1 vectors is feasible and might represent an approach for the treatment of demyelinating diseases. Advantages of this approach over systemic cytokine administration are the high cytokine level reached in the CNS, the absence of effects on the peripheral immune system, and the long-lasting cytokine production in the CNS after a single vector administration.

T-Helper 1 and T-helper 2 cytokine responses in gut-associated lymphoid tissue following enteric reovirus infection

Enteric infection of mice with reovirus serotype 1 elicits antibody and cytotoxic T-lymphocytes in gut-associated lymphoid tissue (GALT). This led to the hypothesis that T-helper 1 (Th1) and T-helper 2 (Th2) responses develop in GALT. Reverse transcriptase-polymerase chain reactions on RNA from Peyer's patches (PP), intraepithelial lymphocytes (IEL), and lamina propria (LP) lymphocytes demonstrated that interferon (IFN)-gamma message was increased in PP and IEL, but not in LP following infection. No increase in mRNA for interleukin (IL)-4, IL-5, or IL-6 was detected. IFN-gamma, IL-5, and IL-6 were produced in in vitro cultures of PP 4-10 days postinfection. PP and spleen lymphocytes from infected mice produced IFN-gamma, but no IL-5 following in vitro restimulation. Infection also induced production of mRNA for the beta2 chain of the IL-12 receptor in PP. We conclude that reovirus induces robust Th1 and weak Th2 cell responses in GALT.