SIV DNA vaccine co-administered with IL-12 expression plasmid enhances CD8 SIV cellular immune responses in cynomolgus macaques

Induction of food-specific IgG by Gene Gun-delivered DNA vaccines

Background

Shellfish and tree nut allergies are among the most prevalent food allergies, now affecting 2%–3% and 1% of the US population, respectively. Currently, there are no approved therapies for shellfish or tree nut allergies, with strict avoidance being the standard of care. However, oral immunotherapy for peanut allergy and subcutaneous immunotherapy for environmental allergens are efficacious and lead to the production of allergen-specific IgG, which causes suppression of allergen effector cell degranulation. Since allergen-specific IgG is a desired response to alleviate IgE-mediated allergies, we tested transcutaneously-delivered DNA vaccines targeting shellfish and tree nut allergens for their ability to induce antigen-specific IgG, which would have therapeutic potential for food allergies.

Methods

We assessed Gene Gun-delivered DNA vaccines targeting either crustacean shellfish or walnut/pecan allergens, with or without IL-12, in naïve mice. Three strains of mice, BALB/cJ, C3H/HeJ and CC027/GeniUnc, were evaluated for IgG production following vaccination. Vaccines were administered twice via Gene Gun, three weeks apart and then blood was collected three weeks following the final vaccination.

Results

Vaccination with shellfish allergen DNA led to increased shrimp-specific IgG in all three strains, with the highest production in C3H/HeJ from the vaccine alone, whereas the vaccine with IL-12 led to the highest IgG production in BALB/cJ and CC027/GeniUnc mice. Similar IgG production was also induced against lobster and crab allergens. For walnut/pecan vaccines, BALB/cJ and C3H/HeJ mice produced significantly higher walnut- and pecan-specific IgG with the vaccine alone compared to the vaccine with IL-12, while the CC027 mice made significantly higher IgG with the addition of IL-12. Notably, intramuscular administration of the vaccines did not lead to increased antigen-specific IgG production, indicating that Gene Gun administration is a superior delivery modality.

Conclusions

Overall, these data demonstrate the utility of DNA vaccines against two lifelong food allergies, shellfish and tree nuts, suggesting their potential as a food allergy therapy in the future.

The Genetic Adjuvants Interleukin-12 and Granulocyte-Macrophage Colony Stimulating Factor Enhance the Immunogenicity of an Ebola Virus Deoxyribonucleic Acid Vaccine in Mice

In previous studies, we showed that deoxyribonucleic acid (DNA) vaccines expressing codon-optimized filovirus envelope glycoprotein genes protect mice and nonhuman primates from viral challenge when delivered by intramuscular (IM) electroporation (EP). To determine whether we could achieve equivalent immunogenicity and protective efficacy by a simplified delivery method, we generated DNA vaccine plasmids expressing genetic adjuvants to potentiate immune responses. We tested the Th1-inducing cytokine interleukin-12 and the granulocyte growth factor granulocyte-macrophage colony stimulating factor, both of which have demonstrated significant adjuvant effect when included in clinical DNA vaccine formulations. In addition, because interferon (IFN)-αβ is required for DNA vaccine-induced immunity, we tested inclusion of a potent stimulator of the IFN-αβ pathway. Our data suggest that IM vaccination of mice with plasmid DNA encoding genetic adjuvants enhances vaccine immunogenicity, resulting in increased anti-Ebola virus (EBOV) immunoglobulin G and T-cell responses. Codelivery of genetic adjuvants also improved EBOV neutralizing capability compared with vaccine alone. Finally, IM vaccination with plasmid EBOV and genetic adjuvants provided complete protection against EBOV challenge. Overall, our data suggest that codelivery of genetic adjuvants with filovirus DNA vaccines using IM delivery can provide comparable efficacy to the same DNA vaccines when delivered using IM-EP devices.

Designed DNA-Encoded IL-36 Gamma Acts as a Potent Molecular Adjuvant Enhancing Zika Synthetic DNA Vaccine-Induced Immunity and Protection in a Lethal Challenge Model

Identification of novel molecular adjuvants which can boost and enhance vaccine-mediated immunity and provide dose-sparing potential against complex infectious diseases and for immunotherapy in cancer is likely to play a critical role in the next generation of vaccines. Given the number of challenging targets for which no or only partial vaccine options exist, adjuvants that can address some of these concerns are in high demand. Here, we report that a designed truncated Interleukin-36 gamma (IL-36 gamma) encoded plasmid can act as a potent adjuvant for several DNA-encoded vaccine targets including human immunodeficiency virus (HIV), influenza, and Zika in immunization models. We further show that the truncated IL-36 gamma (opt-36γt) plasmid provides improved dose sparing as it boosts immunity to a suboptimal dose of a Zika DNA vaccine, resulting in potent protection against a lethal Zika challenge.

Prime-Boost Vaccine Regimen for SjTPI and SjC23 Schistosome Vaccines, Increases Efficacy in Water Buffalo in a Field Trial in China

Schistosomiasis remains a serious zoonotic disease in China and the Philippines. Water buffalo and cattle account for the majority of transmission. Vaccination of water buffalo is considered a key strategy to reduce disease prevalence. Previously, we showed that vaccination of water buffalo with SjC23 or SjCTPI plasmid DNA vaccines, induced 50% efficacy to challenge infection. Here, we evaluated several parameters to determine if we can develop a two dose vaccine that maintains the efficacy of the three dose vaccine. We performed four trials evaluating: (1) lab produced vs. GLP grade vaccines, (2) varying the time between prime and boost, (3) the influence of an IL-12 adjuvant, and (4) a two dose heterologous (DNA-protein) prime-boost. We found the source of the DNA vaccines did not matter, nor did increasing the interval between prime and boost. Elimination of the IL-12 plasmid lowered homologous DNA-DNA vaccine efficacy. A major finding was that the heterologous prime boost improved vaccine efficacy, with the prime-boost regimen incorporating both antigens providing a 55% reduction in adult worms and 53% reduction in liver eggs. Vaccinated buffalo produced vaccine-specific antibody responses. These trials suggest that highly effective vaccination against schistosomes can be achieved using a two dose regimen. No adjuvants were used with the protein boost, and the potential that addition of adjuvant to the protein boost to further increase efficacy should be evaluated. These results suggest that use of these two schistosome vaccines can be part of an integrated control strategy to reduce transmission of schistosomiasis in Asia.

The genetic adjuvant IL-12 enhances the protective efficacy of a DNA vaccine for Venezuelan equine encephalitis virus delivered by intramuscular injection in mice

We have previously shown that DNA vaccines expressing codon-optimized alphavirus envelope glycoprotein genes protect both mice and non-human primates from viral challenge when delivered by intramuscular electroporation (IM-EP). To determine if we could achieve equivalent immunogenicity and protective efficacy in the absence of electroporation, we co-delivered our Venezuelan equine encephalitis virus (VEEV) DNA vaccine with DNA plasmids expressing genetic adjuvants designed to augment immune responses. We tested the T_h1-inducing cytokine IL-12 as well as the granulocyte growth factor GM-CSF, both of which have demonstrated significant adjuvant effect when included in clinical DNA vaccine formulations. Additionally, as multiple reports have described the necessity of IFN-αβ in DNA vaccine immunogenicity, we tested vaccine plasmids encoding a potent stimulator of the IFN-αβ pathway. Our data suggest that IM vaccination of mice with plasmid DNA encoding genetic adjuvants enhances VEEV vaccine immunogenicity, resulting in improved T cell responses, as well as skewing of the anti-VEEV IgG antibody isotype. Additionally, IM vaccination of VEEV DNA vaccine and IL-12 provided complete protection against aerosol VEEV challenge. Overall, our data suggest that co-delivery of genetic adjuvants with alphavirus DNA vaccines using IM delivery can influence the type of immune response obtained and provide comparable protective immunity to that achieved by IM-EP delivery of the vaccine without adjuvants.

Immunotherapy Targeting HPV16/18 Generates Potent Immune Responses in HPV-Associated Head and Neck Cancer

PURPOSE

Clinical responses with programmed death (PD-1) receptor-directed antibodies occur in about 20% of patients with advanced head and neck squamous cell cancer (HNSCCa). Viral neoantigens, such as the E6/E7 proteins of HPV16/18, are attractive targets for therapeutic immunization and offer an immune activation strategy that may be complementary to PD-1 inhibition.

PATIENTS AND METHODS

We report phase Ib/II safety, tolerability, and immunogenicity results of immunotherapy with MEDI0457 (DNA immunotherapy targeting HPV16/18 E6/E7 with IL12 encoding plasmids) delivered by electroporation with CELLECTRA constant current device. Twenty-two patients with locally advanced, p16⁺ HNSCCa received MEDI0457.

RESULTS

MEDI0457 was associated with mild injection site reactions, but no treatment-related grade 3-5 adverse events (AE) were noted. Eighteen of 21 evaluable patients showed elevated antigen-specific T-cell activity by IFNγ ELISpot, and persistent cellular responses surpassing 100 spot-forming units (SFUs)/10⁶ peripheral blood mononuclear cells (PBMCs) were noted out to 1 year. Induction of HPV-specific CD8⁺ T cells was observed. MEDI0457 shifted the CD8⁺/FoxP3⁺ ratio in 4 of 5 post immunotherapy tumor samples and increased the number of perforin⁺ immune infiltrates in all 5 patients. One patient developed metastatic disease and was treated with anti-PD-1 therapy with a rapid and durable complete response. Flow-cytometric analyses revealed induction of HPV16-specific PD-1⁺ CD8⁺ T cells that were not found prior to MEDI0547 (0% vs. 1.8%).

CONCLUSIONS

These data demonstrate that MEDI0457 can generate durable HPV16/18 antigen-specific peripheral and tumor immune responses. This approach may be used as a complementary strategy to PD-1/PD-L1 inhibition in HPV-associated HNSCCa to improve therapeutic outcomes.

Control of Heterologous Simian Immunodeficiency Virus SIVsmE660 Infection by DNA and Protein Coimmunization Regimens Combined with Different Toll-Like-Receptor-4-Based Adjuvants in Macaques

An effective AIDS vaccine continues to be of paramount importance for the control of the pandemic, and it has been proven to be an elusive target. Vaccine efficacy trials and macaque challenge studies indicate that protection may be the result of combinations of many parameters. We show that a combination of DNA and protein vaccinations applied at the same time provides rapid and robust cellular and humoral immune responses and evidence for a reduced risk of infection. Vaccine-induced neutralizing antibodies and Env V2-specific antibodies at mucosal sites contribute to the delay of SIV_smE660 acquisition, and genetic makeup (TRIM-5α) affects the effectiveness of the vaccine. These data are important for the design of better vaccines and may also affect other vaccine platforms.

We developed a method of simultaneous vaccination with DNA and protein resulting in robust and durable cellular and humoral immune responses with efficient dissemination to mucosal sites and protection against simian immunodeficiency virus (SIV) infection. To further optimize the DNA-protein coimmunization regimen, we tested a SIV_mac251-based vaccine formulated with either of two Toll-like receptor 4 (TLR4) ligand-based liposomal adjuvant formulations (TLR4 plus TLR7 [TLR4+7] or TLR4 plus QS21 [TLR4+QS21]) in macaques. Although both vaccines induced humoral responses of similar magnitudes, they differed in their functional quality, including broader neutralizing activity and effector functions in the TLR4+7 group. Upon repeated heterologous SIV_smE660 challenge, a trend of delayed viral acquisition was found in vaccinees compared to controls, which reached statistical significance in animals with the TRIM-5α-resistant (TRIM-5α R) allele. Vaccinees were preferentially infected by an SIV_smE660 transmitted/founder virus carrying neutralization-resistant A/K mutations at residues 45 and 47 in Env, demonstrating a strong vaccine-induced sieve effect. In addition, the delay in virus acquisition directly correlated with SIV_smE660-specific neutralizing antibodies. The presence of mucosal V1V2 IgG binding antibodies correlated with a significantly decreased risk of virus acquisition in both TRIM-5α R and TRIM-5α-moderate/sensitive (TRIM-5α M/S) animals, although this vaccine effect was more prominent in animals with the TRIM-5α R allele. These data support the combined contribution of immune responses and genetic background to vaccine efficacy. Humoral responses targeting V2 and SIV-specific T cell responses correlated with viremia control. In conclusion, the combination of DNA and gp120 Env protein vaccine regimens using two different adjuvants induced durable and potent cellular and humoral responses contributing to a lower risk of infection by heterologous SIV challenge.

IMPORTANCE An effective AIDS vaccine continues to be of paramount importance for the control of the pandemic, and it has been proven to be an elusive target. Vaccine efficacy trials and macaque challenge studies indicate that protection may be the result of combinations of many parameters. We show that a combination of DNA and protein vaccinations applied at the same time provides rapid and robust cellular and humoral immune responses and evidence for a reduced risk of infection. Vaccine-induced neutralizing antibodies and Env V2-specific antibodies at mucosal sites contribute to the delay of SIV_smE660 acquisition, and genetic makeup (TRIM-5α) affects the effectiveness of the vaccine. These data are important for the design of better vaccines and may also affect other vaccine platforms.

Advancements in DNA vaccine vectors, non-mechanical delivery methods, and molecular adjuvants to increase immunogenicity

A major advantage of DNA vaccination is the ability to induce both humoral and cellular immune responses. DNA vaccines are currently used in veterinary medicine, but have not achieved widespread acceptance for use in humans due to their low immunogenicity in early clinical studies. However, recent clinical data have re-established the value of DNA vaccines, particularly in priming high-level antigen-specific antibody responses. Several approaches have been investigated for improving DNA vaccine efficacy, including advancements in DNA vaccine vector design, the inclusion of genetically engineered cytokine adjuvants, and novel non-mechanical delivery methods. These strategies have shown promise, resulting in augmented adaptive immune responses in not only mice, but also in large animal models. Here, we review advancements in each of these areas that show promise for increasing the immunogenicity of DNA vaccines.

Advancements in DNA vaccine vectors, non-mechanical delivery methods, and molecular adjuvants to increase immunogenicity

A major advantage of DNA vaccination is the ability to induce both humoral and cellular immune responses. DNA vaccines are currently used in veterinary medicine, but have not achieved widespread acceptance for use in humans due to their low immunogenicity in early clinical studies. However, recent clinical data have re-established the value of DNA vaccines, particularly in priming high-level antigen-specific antibody responses. Several approaches have been investigated for improving DNA vaccine efficacy, including advancements in DNA vaccine vector design, the inclusion of genetically engineered cytokine adjuvants, and novel non-mechanical delivery methods. These strategies have shown promise, resulting in augmented adaptive immune responses in not only mice, but also in large animal models. Here, we review advancements in each of these areas that show promise for increasing the immunogenicity of DNA vaccines.

Dose-dependent inhibition of Gag cellular immunity by Env in SIV/HIV DNA vaccinated macaques

The induction of a balanced immune response targeting the major structural proteins, Gag and Env of HIV, is important for the development of an efficacious vaccine. The use of DNA plasmids expressing different antigens offers the opportunity to test in a controlled manner the influence of different vaccine components on the magnitude and distribution of the vaccine-induced cellular and humoral immune responses. Here, we show that increasing amounts of env DNA results in greatly enhanced Env antibody titers without significantly affecting the levels of anti-Env cellular immune responses. Co-immunization with Env protein further increased antibody levels, indicating that vaccination with DNA only is not sufficient for eliciting maximal humoral responses against Env. In contrast, under high env:gag DNA plasmid ratio, the development of Gag cellular responses was significantly reduced by either SIV or HIV Env, whereas Gag humoral responses were not affected. Our data indicate that a balanced ratio of the 2 key HIV/SIV vaccine components, Gag and Env, is important to avoid immunological interference and to achieve both maximal humoral responses against Env to prevent virus acquisition and maximal cytotoxic T cell responses against Gag to prevent virus spread.

Interleukin-21 administration leads to enhanced antigen-specific T cell responses and natural killer cells in HIV-1 vaccinated mice

Interleukin-21 (IL-21), which belongs to IL-2 γ chain receptor cytokine family, is as an important regulator of immune responses. In this study, we developed a novel strategy for immunizing mice with a DNA/vaccinia/protein vaccine in the presence or absence of mouse IL-21 (mIL-21) to evaluate whether mIL-21 could enhance immune responses. Our results demonstrated that co-immunization with mIL-21 did not increase significantly the capacity of vaccine induced antibodies to bind to HIV-1 GP140. An effect of mIL-21 in adjusting the efficacy of HIV-1 vaccine through enhancing Th1 type immune response was however observed. The frequencies of HIV-1-specific cytokine-producing CD4+ T and CD4+ TEM cells, especially multifunctional T cell responses, were significantly increased by co-administrating with mIL-21. A significant increase was also observed in the frequency of NK cells in mIL-21 adjuvant groups. Taken together, combination of mIL-21 with HIV-1 vaccines led to distinct enhancement of NK cells and T cell immune responses associated with immune protection.

Chemokine-adjuvanted electroporated DNA vaccine induces substantial protection from simian immunodeficiency virus vaginal challenge

There have been encouraging results for the development of an effective HIV vaccine. However, many questions remain regarding the quality of immune responses and the role of mucosal antibodies. We addressed some of these issues by using a simian immunodeficiency virus (SIV) DNA vaccine adjuvanted with plasmid-expressed mucosal chemokines combined with an intravaginal SIV challenge in rhesus macaque (RhM) model. We previously reported on the ability of CCR9 and CCR10 ligand (L) adjuvants to enhance mucosal and systemic IgA and IgG responses in small animals. In this study, RhMs were intramuscularly immunized five times with either DNA or DNA plus chemokine adjuvant delivered by electroporation followed by challenge with SIVsmE660. Sixty-eight percent of all vaccinated animals (P<0.01) remained either uninfected or had aborted infection compared with only 14% in the vaccine naïve group. The highest protection was observed in the CCR10L chemokines group, where six of nine animals had aborted infection and two remained uninfected, leading to 89% protection (P<0.001). The induction of mucosal SIV-specific antibodies and neutralization titers correlated with trends in protection. These results indicate the need to further investigate the contribution of chemokine adjuvants to modulate immune responses and the role of mucosal antibodies in SIV/HIV protection.

A pilot study of pNGVL4a-CRT/E7(detox) for the treatment of patients with HPV16+ cervical intraepithelial neoplasia 2/3 (CIN2/3)

OBJECTIVE

The purpose of this study was to evaluate the safety, efficacy, and immunogenicity of a plasmid vaccine, pNGVL4a-CRT-E7(detox), administered either intradermally, intramuscularly, or directly into the cervical lesion, in patients with HPV16-associated CIN2/3.

METHODS

Eligible patients with HPV16(+) CIN2/3 were enrolled in treatment cohorts evaluating pNGVL4a-CRT-E7(detox), administered by either particle-mediated epidermal delivery (PMED), intramuscular injection (IM), or cervical intralesional injection, at study weeks 0, 4, and 8. Patients were monitored for local injection site and systemic toxicity. A standard therapeutic resection was performed at week 15. The primary endpoints were safety and tolerability. Secondary endpoints included histologic regression and change in cervical HPV viral load. Exploratory endpoints included immune responses in the blood and in the target tissue.

RESULTS

Thirty-two patients with HPV16(+) CIN2/3 were enrolled onto the treatment phase of the study, and were vaccinated. Twenty-two of 32 patients (69%) experienced vaccine-specific related adverse events. The most frequent vaccine-related events were constitutional and local injection site in nature, and were grade 1 or less in severity. Histologic regression to CIN 1 or less occurred in 8 of 27 (30%) patients who received all vaccinations and underwent LEEP. In subject-matched comparisons, intraepithelial CD8+ T cell infiltrates increased after vaccination in subjects in the intralesional administration cohort.

CONCLUSION

pNGVL4a-CRT-E7(detox) was well-tolerated, elicited the most robust immune response when administered intralesionally, and demonstrated preliminary evidence of potential clinical efficacy.

Therapeutic and prophylactic DNA vaccines for HIV-1

INTRODUCTION

DNA vaccines have moved into clinical trials in several fields and their success will be important for licensure of this vaccine modality. An effective vaccine for HIV-1 remains elusive and the development of one is troubled by safety and efficacy issues. Additionally, the ability for an HIV-1 vaccine to induce both the cellular and humoral arms of the immune system is needed. DNA vaccines not only offer a safe approach for the development of an HIV-1 vaccine but they have also been shown to elicit both arms of the immune system.

AREAS COVERED

This review explores how DNA vaccine design including the regimen, genetic adjuvants used, targeting, and mode of delivery continues to undergo improvements, thereby providing a potential option for an immunogenic vaccine for HIV-1.

EXPERT OPINION

Continued improvements in delivery technology, in particular electroporation, and the use of prime-boost vaccine strategies will aid in boosting the immunogenicity of DNA vaccines. Basic immunology research will also help discover new potential adjuvant targets that can be combined with DNA vaccination, such as inhibitors of inhibitory receptors.

Intramuscular therapeutic vaccination targeting HPV16 induces T cell responses that localize in mucosal lesions

About 25% of high-grade cervical intraepithelial neoplasias (CIN2/3) caused by human papillomavirus serotype 16 (HPV16) undergo complete spontaneous regression. However, to date, therapeutic vaccination strategies for HPV disease have yielded limited success when measured by their ability to induce robust peripheral blood T cell responses to vaccine antigen. We report marked immunologic changes in the target lesion microenvironment after intramuscular therapeutic vaccination targeting HPV16 E6/E7 antigens, in subjects with CIN2/3 who had modest detectable responses in circulating T lymphocytes. Histologic and molecular changes, including markedly (average threefold) increased intensity of CD8(+) T cell infiltrates in both the stromal and epithelial compartments, suggest an effector response to vaccination. Postvaccination cervical tissue immune infiltrates included organized tertiary lymphoid-like structures in the stroma subjacent to residual intraepithelial lesions and, unlike infiltrates in unvaccinated lesions, showed evidence of proliferation induced by recognition of cognate antigen. At a molecular level, these histologic changes in the stroma were characterized by increased expression of genes associated with immune activation (CXCR3) and effector function (Tbet and IFNβ), and were also associated with an immunologic signature in the overlying dysplastic epithelium. High-throughput T cell receptor sequencing of unmanipulated specimens identified clonal expansions in the tissue that were not readily detectable in peripheral blood. Together, these findings indicate that peripheral therapeutic vaccination to HPV antigens can induce a robust tissue-localized effector immune response, and that analyses of immune responses at sites of antigen are likely to be much more informative than analyses of cells that remain in the circulation.

Applications of immunochemistry in human health: advances in vaccinology and antibody design (IUPAC Technical Report)

This report discusses the history and mechanisms of vaccination of humans as well as the engineering of therapeutic antibodies. Deeper understanding of the molecular interactions involved in both acquired and innate immunity is allowing sophistication in design of modified and even synthetic vaccines. Recombinant DNA technologies are facilitating development of DNA-based vaccines, for example, with the recognition that unmethylated CpG sequences in plasmid DNA will target Toll-like receptors on antigen-presenting cells. Formulations of DNA vaccines with increased immunogenicity include engineering into plasmids with “genetic adjuvant” capability, incorporation into polymeric or magnetic nanoparticles, and formulation with cationic polymers and other polymeric and non-polymeric coatings. Newer methods of delivery, such as particle bombardment, DNA tattooing, electroporation, and magnetic delivery, are also improving the effectiveness of DNA vaccines. RNA-based vaccines and reverse vaccinology based on gene sequencing and bioinformatic approaches are also considered. Structural vaccinology is an approach in which the detailed molecular structure of viral epitopes is used to design synthetic antigenic peptides. Virus-like particles are being designed for vaccine deliveries that are based on structures of viral capsid proteins and other synthetic lipopeptide building blocks. A new generation of adjuvants is being developed to further enhance immunogenicity, based on squalene and other oil–water emulsions, saponins, muramyl dipeptide, immunostimulatory oligonucleotides, Toll-like receptor ligands, and lymphotoxins. Finally, current trends in engineering of therapeutic antibodies including improvements of antigen-binding properties, pharmacokinetic and pharmaceutical properties, and reduction of immunogenicity are discussed. Taken together, understanding the chemistry of vaccine design, delivery and immunostimulation, and knowledge of the techniques of antibody design are allowing targeted development for the treatment of chronic disorders characterized by continuing activation of the immune system, such as autoimmune disorders, cancer, or allergies that have long been refractory to conventional approaches.

High IP-10 levels decrease T cell function in HIV-1-infected individuals on ART

HIV-1-infected subjects, despite control of viral replication with ART, have an altered immune cytokine/chemokine milieu. Changes in systemic cytokines and chemokines can alter immune responses. IP-10, in particular, has been associated with pathogenesis in a number of conditions, and we found that IP-10 is increased in serum in subjects who are HIV-1 infected and on stable ART compared with HIV-1-uninfected individuals. In a series of in vitro studies, we found that PBMCs exposed to IP-10 showed a significant decrease in the number of cells capable of secreting IFN-γ, as well as other cytokines, when stimulated with recall antigens. Furthermore, treatment with IP-10 led to decreased antigen-specific calcium signaling and MAPK38 phosphorylation. Importantly, the cytokines, as well as proliferative responses, could be enhanced with an IP-10 Nab. Our findings suggest that IP-10-modulating drugs may potentially enhance T cell responses to vaccination and HIV-1 in HIV+ subjects on ART.

The influence of delivery vectors on HIV vaccine efficacy

Development of an effective HIV/AIDS vaccine remains a big challenge, largely due to the enormous HIV diversity which propels immune escape. Thus novel vaccine strategies are targeting multiple variants of conserved antibody and T cell epitopic regions which would incur a huge fitness cost to the virus in the event of mutational escape. Besides immunogen design, the delivery modality is critical for vaccine potency and efficacy, and should be carefully selected in order to not only maximize transgene expression, but to also enhance the immuno-stimulatory potential to activate innate and adaptive immune systems. To date, five HIV vaccine candidates have been evaluated for efficacy and protection from acquisition was only achieved in a small proportion of vaccinees in the RV144 study which used a canarypox vector for delivery. Conversely, in the STEP study (HVTN 502) where human adenovirus serotype 5 (Ad5) was used, strong immune responses were induced but vaccination was more associated with increased risk of HIV acquisition than protection in vaccinees with pre-existing Ad5 immunity. The possibility that pre-existing immunity to a highly promising delivery vector may alter the natural course of HIV to increase acquisition risk is quite worrisome and a huge setback for HIV vaccine development. Thus, HIV vaccine development efforts are now geared toward delivery platforms which attain superior immunogenicity while concurrently limiting potential catastrophic effects likely to arise from pre-existing immunity or vector-related immuno-modulation. However, it still remains unclear whether it is poor immunogenicity of HIV antigens or substandard immunological potency of the safer delivery vectors that has limited the success of HIV vaccines. This article discusses some of the promising delivery vectors to be harnessed for improved HIV vaccine efficacy.

HIV DNA Vaccine: Stepwise Improvements Make a Difference

Inefficient DNA delivery methods and low expression of plasmid DNA have been major obstacles for the use of plasmid DNA as vaccine for HIV/AIDS. This review describes successful efforts to improve DNA vaccine methodology over the past ~30 years. DNA vaccination, either alone or in combination with other methods, has the potential to be a rapid, safe, and effective vaccine platform against AIDS. Recent clinical trials suggest the feasibility of its translation to the clinic.

Co-Administration of Molecular Adjuvants Expressing NF-Kappa B Subunit p65/RelA or Type-1 Transactivator T-bet Enhance Antigen Specific DNA Vaccine-Induced Immunity

DNA vaccine-induced immunity can be enhanced by the co-delivery of synthetic gene-encoding molecular adjuvants. Many of these adjuvants have included cytokines, chemokines or co-stimulatory molecules that have been demonstrated to enhance vaccine-induced immunity by increasing the magnitude or type of immune responses and/or protective efficacy. In this way, through the use of adjuvants, immune responses can be highly customizable and functionally tailored for optimal efficacy against pathogen specific (i.e., infectious agent) or non-pathogen (i.e., cancer) antigens. In the novel study presented here, we examined the use of cellular transcription factors as molecular adjuvants. Specifically the co-delivery of (a) RelA, a subunit of the NF-κB transcription complex or (b) T-bet, a T_h1-specific T box transcription factor, along with a prototypical DNA vaccine expressing HIV-1 proteins was evaluated. As well, all of the vaccines and adjuvants were administered to mice using in vivo electroporation (EP), a technology demonstrated to dramatically increase plasmid DNA transfection and subsequent transgene expression with concomitant enhancement of vaccine induced immune responses. As such, this study demonstrated that co-delivery of either adjuvant resulted in enhanced T and B cell responses, specifically characterized by increased T cell numbers, IFN-γ production, as well as enhanced antibody responses. This study demonstrates the use of cellular transcription factors as adjuvants for enhancing DNA vaccine-induced immunity.

DNA and protein co-immunization improves the magnitude and longevity of humoral immune responses in macaques

We tested the concept of combining DNA with protein to improve anti-HIV Env systemic and mucosal humoral immune responses. Rhesus macaques were vaccinated with DNA, DNA&protein co-immunization or DNA prime followed by protein boost, and the magnitude and mucosal dissemination of the antibody responses were monitored in both plasma and mucosal secretions. We achieved induction of robust humoral responses by optimized DNA vaccination delivered by in vivo electroporation. These responses were greatly increased upon administration of a protein boost. Importantly, a co-immunization regimen of DNA&protein injected in the same muscle at the same time induced the highest systemic binding and neutralizing antibodies to homologous or heterologous Env as well as the highest Env-specific IgG in saliva. Inclusion of protein in the vaccine resulted in more immunized animals with Env-specific IgG in rectal fluids. Inclusion of DNA in the vaccine significantly increased the longevity of systemic humoral immune responses, whereas protein immunization, either as the only vaccine component or as boost after DNA prime, was followed by a great decline of humoral immune responses overtime. We conclude that DNA&protein co-delivery in a simple vaccine regimen combines the strength of each vaccine component, resulting in improved magnitude, extended longevity and increased mucosal dissemination of the induced antibodies in immunized rhesus macaques.

DNA Immunization for HIV Vaccine Development

DNA vaccination has been studied in the last 20 years for HIV vaccine research. Significant experience has been accumulated in vector design, antigen optimization, delivery approaches and the use of DNA immunization as part of a prime-boost HIV vaccination strategy. Key historical data and future outlook are presented. With better understanding on the potential of DNA immunization and recent progress in HIV vaccine research, it is anticipated that DNA immunization will play a more significant role in the future of HIV vaccine development.

Synthetic DNA vaccines: improved vaccine potency by electroporation and co-delivered genetic adjuvants

In recent years, DNA vaccines have undergone a number of technological advancements that have incited renewed interest and heightened promise in the field. Two such improvements are the use of genetically engineered cytokine adjuvants and plasmid delivery via in vivo electroporation (EP), the latter of which has been shown to increase antigen delivery by nearly 1000-fold compared to naked DNA plasmid delivery alone. Both strategies, either separately or in combination, have been shown to augment cellular and humoral immune responses in not only mice, but also in large animal models. These promising results, coupled with recent clinical trials that have shown enhanced immune responses in humans, highlight the bright prospects for DNA vaccines to address many human diseases.

Synthetic DNA vaccine strategies against persistent viral infections

The human body has developed an elaborate defense system against microbial pathogens and foreign antigens. However, particular microbes have evolved sophisticated mechanisms to evade immune surveillance, allowing persistence within the human host. In an effort to combat such infections, intensive research has focused on the development of effective prophylactic and therapeutic countermeasures to suppress or clear persistent viral infections. To date, popular therapeutic strategies have included the use of live-attenuated microbes, viral vectors and dendritic-cell vaccines aiming to help suppress or clear infection. In recent years, improved DNA vaccines have now re-emerged as a promising candidate for therapeutic intervention due to the development of advanced optimization and delivery technologies. For instance, genetic optimization of synthetic plasmid constructs and their encoded antigens, in vivo electroporation-mediated vaccine delivery, as well as codelivery with molecular adjuvants have collectively enhanced both transgene expression and the elicitation of vaccine-induced immunity. In addition, the development of potent heterologous prime-boost regimens has also provided significant contributions to DNA vaccine immunogenicity. Herein, the authors will focus on these recent improvements to this synthetic platform in relation to their application in combating persistent virus infection.

SIV antigen-specific effects on immune responses induced by vaccination with DNA electroporation and plasmid IL-12

Molecular adjuvants are important for augmenting or modulating immune responses induced by DNA vaccination. Promising results have been obtained using IL-12 expression plasmids in a variety of disease models including the SIV model of HIV infection. We used a mouse model to evaluate plasmid IL-12 (pIL-12) in a DNA prime, recombinant adenovirus serotype 5 (rAd5) boost regimen specifically to evaluate the effect of IL-12 expression on cellular and humoral immunity induced against both SIVmac239 Gag and Env antigens. Priming with electroporated (EP) DNA+pIL-12 resulted in a 2-4-fold enhanced frequency of Gag-specific CD4 T cells which was maintained through the end of the study irrespective of the pIL-12 dose, while memory Env-specific CD4+T cells were maintained only at the low dose of pIL-12. There was little positive effect of pIL-12 on the humoral response to Env, and in fact, high dose pIL-12 dramatically reduced SIV Env-specific IgG. Additionally, both doses of pIL-12 diminished the frequency of CD8 T-cells after DNA prime, although a rAd5 boost recovered CD8 responses regardless of the pIL-12 dose. In this prime-boost regimen, we have shown that a high dose pIL-12 can systemically reduce Env-specific humoral responses and CD4T cell frequency, but not Gag-specific CD4+ T cells. These data indicate that it is important to independently characterize individual SIV or HIV antigen immunogenicity in multi-antigenic vaccines as a function of adjuvant dose.

Highly optimized DNA vaccine targeting human telomerase reverse transcriptase stimulates potent antitumor immunity

High levels of human telomerase reverse transcriptase (hTERT) are detected in more than 85% of human cancers. Immunologic analysis supports that hTERT is a widely applicable target recognized by T cells and can be potentially studied as a broad cancer immunotherapeutic, or a unique line of defense against tumor recurrence. There remains an urgent need to develop more potent hTERT vaccines. Here, a synthetic highly optimized full-length hTERT DNA vaccine (phTERT) was designed and the induced immunity was examined in mice and non-human primates (NHP). When delivered by electroporation, phTERT elicited strong, broad hTERT-specific CD8 T-cell responses including induction of T cells expressing CD107a, IFN-γ, and TNF-α in mice. The ability of phTERT to overcome tolerance was evaluated in an NHP model, whose TERT is 96% homologous to that of hTERT. Immunized monkeys exhibited robust [average 1,834 spot forming unit (SFU)/10(6) peripheral blood mononuclear cells (PBMC)], diverse (multiple immunodominant epitopes) IFN-γ responses and antigen-specific perforin release (average 332 SFU/10(6) PBMCs), suggesting that phTERT breaks tolerance and induces potent cytotoxic responses in this human-relevant model. Moreover, in an HPV16-associated tumor model, vaccination of phTERT slows tumor growth and improves survival rate in both prophylactic and therapeutic studies. Finally, in vivo cytotoxicity assay confirmed that phTERT-induced CD8 T cells exhibited specific cytotoxic T lymphocyte (CTL) activity, capable of eliminating hTERT-pulsed target cells. These findings support that this synthetic electroporation-delivered DNA phTERT may have a role as a broad therapeutic cancer vaccine candidate.

Vaccination with Vaxfectin(®) adjuvanted SIV DNA induces long-lasting humoral immune responses able to reduce SIVmac251 Viremia

We evaluated the immunogenicity and efficacy of Vaxfectin(®) adjuvanted SIV DNA vaccines in mice and macaques. Vaccination of mice with Vaxfectin(®) adjuvanted SIV gag DNA induced higher humoral immune responses than administration of unadjuvanted DNA, whereas similar levels of cellular immunity were elicited. Vaxfectin(®) adjuvanted SIVmac251 gag and env DNA immunization of rhesus macaques was used to examine magnitude, durability, and efficacy of humoral immunity. Vaccinated macaques elicited potent neutralizing antibodies able to cross-neutralize the heterologous SIVsmE660 Env. We found remarkable durability of Gag and Env humoral responses, sustained during ~2 y of follow-up. The Env-specific antibody responses induced by Vaxfectin(®) adjuvanted env DNA vaccination disseminated into mucosal tissues, as demonstrated by their presence in saliva, including responses to the V1-V2 region, and rectal fluids. The efficacy of the immune responses was evaluated upon intrarectal challenge with low repeated dose SIVmac251. Although 2 of the 3 vaccinees became infected, these animals showed significantly lower peak virus loads and lower chronic viremia than non-immunized infected controls. Thus, Vaxfectin(®) adjuvanted DNA is a promising vaccine approach for inducing potent immune responses able to control the highly pathogenic SIVmac251.

Comparison of intradermal and intramuscular delivery followed by in vivo electroporation of SIV Env DNA in macaques

A panel of SIVmac251 transmitted Env sequences were tested for expression, function and immunogenicity in mice and macaques. The immunogenicity of a DNA vaccine cocktail expressing SIVmac239 and three transmitted SIVmac251 Env sequences was evaluated upon intradermal or intramuscular injection followed by in vivo electroporation in macaques using sequential vaccination of gp160, gp120 and gp140 expressing DNAs. Both intradermal and intramuscular vaccination regimens using the gp160 expression plasmids induced robust humoral immune responses, which further improved using the gp120 expressing DNAs. The responses showed durability of binding and neutralizing antibody titers and high avidity for>1 y. The intradermal DNA delivery regimen induced higher cross-reactive responses able to neutralize the heterologous tier 1B-like SIVsmE660_CG7V. Analysis of cellular immune responses showed induction of Env-specific memory responses and cytotoxic granzyme B(+) T cells in both vaccine groups, although the magnitude of the responses were ~10x higher in the intramuscular/electroporation group. The cellular responses induced by both regimens were long lasting and could be detected ~1 y after the last vaccination. These data show that both DNA delivery methods are able to induce robust and durable immune responses in macaques.

A brief history of the global effort to develop a preventive HIV vaccine

Soon after HIV was discovered as the cause of AIDS in 1983-1984, there was an expectation that a preventive vaccine would be rapidly developed. In trying to achieve that goal, three successive scientific paradigms have been explored: induction of neutralizing antibodies, induction of cell mediated immunity, and exploration of combination approaches and novel concepts. Although major progress has been made in understanding the scientific basis for HIV vaccine development, efficacy trials have been critical in moving the field forward. In 2009, the field was reinvigorated with the modest results obtained from the RV144 trial conducted in Thailand. Here, we review those vaccine development efforts, with an emphasis on events that occurred during the earlier years. The goal is to provide younger generations of scientists with information and inspiration to continue the search for an HIV vaccine.

Immunotherapy against HPV16/18 generates potent TH1 and cytotoxic cellular immune responses

Despite the development of highly effective prophylactic vaccines against human papillomavirus (HPV) serotypes 16 and 18, prevention of cervical dysplasia and cancer in women infected with high-risk HPV serotypes remains an unmet medical need. We report encouraging phase 1 safety, tolerability, and immunogenicity results for a therapeutic HPV16/18 candidate vaccine, VGX-3100, delivered by in vivo electroporation (EP). Eighteen women previously treated for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3) received a three-dose (intramuscular) regimen of highly engineered plasmid DNA encoding HPV16 and HPV18 E6/E7 antigens followed by EP in a dose escalation study (0.3, 1, and 3 mg per plasmid). Immunization was well tolerated with reports of mild injection site reactions and no study-related serious or grade 3 and 4 adverse events. No dose-limiting toxicity was noted, and pain was assessed by visual analog scale, with average scores decreasing from 6.2/10 to 1.4 within 10 min. Average peak interferon-γ enzyme-linked immunospot magnitudes were highest in the 3 mg cohort in comparison to the 0.3 and 1 mg cohorts, suggesting a trend toward a dose effect. Flow cytometric analysis revealed the induction of HPV-specific CD8(+) T cells that efficiently loaded granzyme B and perforin and exhibited full cytolytic functionality in all cohorts. These data indicate that VGX-3100 is capable of driving robust immune responses to antigens from high-risk HPV serotypes and could contribute to elimination of HPV-infected cells and subsequent regression of the dysplastic process.

The p40 subunit of interleukin (IL)-12 promotes stabilization and export of the p35 subunit: implications for improved IL-12 cytokine production

IL-12 is a 70-kDa heterodimeric cytokine composed of the p35 and p40 subunits. To maximize cytokine production from plasmid DNA, molecular steps controlling IL-12p70 biosynthesis at the posttranscriptional and posttranslational levels were investigated. We show that the combination of RNA/codon-optimized gene sequences and fine-tuning of the relative expression levels of the two subunits within a cell resulted in increased production of the IL-12p70 heterodimer. We found that the p40 subunit plays a critical role in enhancing the stability, intracellular trafficking, and export of the p35 subunit. This posttranslational regulation mediated by the p40 subunit is conserved in mammals. Based on these findings, dual gene expression vectors were generated, producing an optimal ratio of the two subunits, resulting in a ∼1 log increase in human, rhesus, and murine IL-12p70 production compared with vectors expressing the wild type sequences. Such optimized DNA plasmids also produced significantly higher levels of systemic bioactive IL-12 upon in vivo DNA delivery in mice compared with plasmids expressing the wild type sequences. A single therapeutic injection of an optimized murine IL-12 DNA plasmid showed significantly more potent control of tumor development in the B16 melanoma cancer model in mice. Therefore, the improved IL-12p70 DNA vectors have promising potential for in vivo use as molecular vaccine adjuvants and in cancer immunotherapy.

IL-12 DNA as molecular vaccine adjuvant increases the cytotoxic T cell responses and breadth of humoral immune responses in SIV DNA vaccinated macaques

Intramuscular injection of macaques with an IL-12 expression plasmid (0.1 or 0.4 mg DNA/animal) optimized for high level of expression and delivered using in vivo electroporation, resulted in the detection of systemic IL-12 cytokine in the plasma. Peak levels obtained by day 4-5 post injection were paralleled by a rapid increase of IFN-γ, indicating bioactivity of the IL-12 cytokine. Both plasma IL-12 and IFN-γ levels were reduced to basal levels by day 14, indicating a short presence of elevated levels of the bioactive IL-12. The effect of IL-12 as adjuvant together with an SIVmac239 DNA vaccine was further examined comparing two groups of rhesus macaques vaccinated in the presence or absence of IL-12 DNA. The IL-12 DNA-adjuvanted group developed significantly higher SIV-specific cellular immune responses, including IFN-γ (+) Granzyme B (+) T cells, demonstrating increased levels of vaccine-induced T cells with cytotoxic potential, and this difference persisted for 6 mo after the last vaccination. Coinjection of IL-12 DNA led to increases in Gag-specific CD4 (+) and CD4 (+) CD8 (+) double-positive memory T cell subsets, whereas the Env-specific increases were mainly mediated by the CD8 (+) and CD4 (+) CD8 (+) double-positive memory T cell subsets. The IL-12 DNA-adjuvanted vaccine group developed higher binding antibody titers to Gag and mac251 Env, and showed higher and more durable neutralizing antibodies to heterologous SIVsmE660. Therefore, co-delivery of IL-12 DNA with the SIV DNA vaccine enhanced the magnitude and breadth of immune responses in immunized rhesus macaques, and supports the inclusion of IL-12 DNA as vaccine adjuvant.

Soluble mediators of inflammation in HIV and their implications for therapeutics and vaccine development

From early in the HIV epidemic it was appreciated that many inflammatory markers such as neopterin and TNF-α were elevated in patients with AIDS. With the advent of modern technology able to measure a broad array of cytokines, we now know that from the earliest points of infection HIV induces a cytokine storm. This review will focus on how cytokines are disturbed in HIV infection and will explore potential therapeutic uses of cytokines. These factors can be used directly as therapy during HIV infection, either to suppress viral replication or prevent deleterious immune effects of infection, such as CD4+ T cell depletion. Cytokines also show great promise as adjuvants in the development of HIV vaccines, which would be critical for the eventual control of the epidemic.

Cytokine production and dysregulation in HIV pathogenesis: lessons for development of therapeutics and vaccines

Numerous studies have characterized the cytokine modulation observed in human immunodeficiency virus (HIV) infected individuals, from initial infection through chronic disease. Progressive and non-progressive HIV infection models show the cytokine milieu differs in terms of production and responsiveness in these two groups, suggesting an understanding of the role cytokines play during infection is necessary for directing the immune response toward viral control. This review will cover cytokine induction and dysfunction during HIV pathogenesis, with a focus on the interplay between cytokines and transcription factors, T cell activation, and exhaustion. We highlight cytokines that have either vaccine adjuvant or therapeutic potential and discuss the need to identify key factors required for prevention of progression, clearance of infection, or protection from acquisition.

Cancer genome sequencing and its implications for personalized cancer vaccines

New DNA sequencing platforms have revolutionized human genome sequencing. The dramatic advances in genome sequencing technologies predict that the $1,000 genome will become a reality within the next few years. Applied to cancer, the availability of cancer genome sequences permits real-time decision-making with the potential to affect diagnosis, prognosis, and treatment, and has opened the door towards personalized medicine. A promising strategy is the identification of mutated tumor antigens, and the design of personalized cancer vaccines. Supporting this notion are preliminary analyses of the epitope landscape in breast cancer suggesting that individual tumors express significant numbers of novel antigens to the immune system that can be specifically targeted through cancer vaccines.

Clinical applications of DNA vaccines: current progress

It was discovered almost 20 years ago that plasmid DNA, when injected into the skin or muscle of mice, could induce immune responses to encoded antigens. Since that time, there has since been much progress in understanding the basic biology behind this deceptively simple vaccine platform and much technological advancement to enhance immune potency. Among these advancements are improved formulations and improved physical methods of delivery, which increase the uptake of vaccine plasmids by cells; optimization of vaccine vectors and encoded antigens; and the development of novel formulations and adjuvants to augment and direct the host immune response. The ability of the current, or second-generation, DNA vaccines to induce more-potent cellular and humoral responses opens up this platform to be examined in both preventative and therapeutic arenas. This review focuses on these advances and discusses both preventive and immunotherapeutic clinical applications.

Hepatitis C virus NS3/NS4A DNA vaccine induces multiepitope T cell responses in rhesus macaques mimicking human immune responses [corrected]

Numerous studies have suggested that an effective hepatitis C virus (HCV) vaccine must induce a strong T helper 1 (Th1) T cell response. While several therapeutic vaccine candidates have shown promise in clinical trials, response rates have been low suggesting that further optimization is important. However, such optimization has been hindered by a lack of a benchmark animal model in which to test vaccine-induced immune responses before clinical evaluation. The goal of this study was to analyze the utility of the rhesus macaque vaccination model in assessing HCV vaccine-induced T cell responses. To test this, we employed the use of a novel HCV genotype 1a/1b consensus DNA vaccine encoding both HCV nonstructural protein 3 (NS3) and nonstructural protein 4A (NS4A) proteins. Following immunization, rhesus macaques mounted HCV-specific responses strikingly similar to those reported in resolving patients, including strong NS3-specific interferon-γ (IFN-γ) responses, robust CD4(+) and CD8(+) T cell proliferation, and induction of polyfunctional T cells. Additionally, fine epitope mapping revealed one animal that mounted a T cell response against a known HCV NS3 human leukocyte antigen A2 (HLA-A2) epitope previously identified in humans. Taken together our findings suggest that the rhesus macaque vaccination model is a useful tool in the evaluation of immune responses induced by HCV immunogens.

Comparison of immune responses generated by optimized DNA vaccination against SIV antigens in mice and macaques

Optimized DNA vectors were constructed comprising the proteome of SIV including the structural, enzymatic, regulatory, and accessory proteins. In addition to native antigens as produced by the virus, fusion proteins and modified antigens with altered secretion, cellular localization and stability characteristics were generated. The DNA vectors were tested for expression upon transfection in human cells. In addition, the vectors were tested either alone or in combinations in mice and macaques, which provided an opportunity to compare immune responses in two animal models. DNA only immunization using intramuscular injection in the absence or presence of in vivo electroporation did not alter the phenotype of the induced T cell responses in mice. Although several fusion proteins induced immune responses to all the components of a polyprotein, we noted fusion proteins that abrogated immune response to some of the components. Since the expression levels of such fusion proteins were not affected, these data suggest that the immune recognition of certain components was altered by the fusion. Testing different DNA vectors in mice and macaques revealed that a combination of DNAs producing different forms of the same antigen generated more balanced immune responses, a desirable feature for an optimal AIDS vaccine.

Selected approaches for increasing HIV DNA vaccine immunogenicity in vivo

The safety, stability, and ability for repeat homologous vaccination makes the DNA vaccine platform an excellent candidate for an effective HIV-1 vaccine. However, the immunogenicity of early DNA vaccines did not translate from small animal models into larger non-human primates and was markedly lower than viral vectors. In addition to improvements to the DNA vector itself, delivery with electroporation, the inclusion of molecular adjuvants, and heterologous prime-boost strategies have dramatically improved the immunogenicity of DNA vaccines for HIV and currently makes them a leading platform with many areas warranting further research and clinical development.

Vaccination for hepatitis C virus: closing in on an evasive target

Hepatitis C virus (HCV) infects more than 170 million people globally and is a leading cause of liver cirrhosis, transplantation and hepatocellular carcinoma. Current gold-standard therapy often fails, has significant side effects in many cases and is expensive. No vaccine is currently available. The fact that a significant proportion of infected people spontaneously control HCV infection in the setting of an appropriate immune response suggests that a vaccine for HCV is a realistic goal. A comparative analysis of infected people with distinct clinical outcomes has enabled the characterization of many important innate and adaptive immune processes associated with viral control. It is clear that a successful HCV vaccine will need to exploit and enhance these natural immune defense mechanisms. New HCV vaccine approaches, including peptide, recombinant protein, DNA and vector-based vaccines, have recently reached Phase I/II human clinical trials. Some of these technologies have generated robust antiviral immunity in healthy volunteers and infected patients. The challenge now is to move forward into larger at-risk or infected populations to truly test efficacy.

DNA/Ad5 vaccination with SIV epitopes induced epitope-specific CD4⁺ T cells, but few subdominant epitope-specific CD8⁺ T cells

The goals of a T cell-based vaccine for HIV are to reduce viral peak and setpoint and prevent transmission. While it has been relatively straightforward to induce CD8(+) T cell responses against immunodominant T cell epitopes, it has been more difficult to broaden the vaccine-induced CD8(+) T cell response against subdominant T cell epitopes. Additionally, vaccine regimens to induce CD4(+) T cell responses have been studied only in limited settings. In this study, we sought to elicit CD8(+) T cells against subdominant epitopes and CD4(+) T cells using various novel and well-established vaccine strategies. We vaccinated three Mamu-A*01(+) animals with five Mamu-A*01-restricted subdominant SIV-specific CD8(+) T cell epitopes. All three vaccinated animals made high frequency responses against the Mamu-A*01-restricted Env TL9 epitope with one animal making a low frequency CD8(+) T cell response against the Pol LV10 epitope. We also induced SIV-specific CD4(+) T cells against several MHC class II DRBw*606-restricted epitopes. Electroporated DNA with pIL-12 followed by a rAd5 boost was the most immunogenic vaccine strategy. We induced responses against all three Mamu-DRB*w606-restricted CD4 epitopes in the vaccine after the DNA prime. Ad5 vaccination further boosted these responses. Although we successfully elicited several robust epitope-specific CD4(+) T cell responses, vaccination with subdominant MHC class I epitopes elicited few detectable CD8(+) T cell responses. Broadening the CD8(+) T cell response against subdominant MHC class I epitopes was, therefore, more difficult than we initially anticipated.

SIV antigen immunization induces transient antigen-specific T cell responses and selectively activates viral replication in draining lymph nodes in retroviral suppressed rhesus macaques

Background

HIV infection causes a qualitative and quantitative loss of CD4⁺ T cell immunity. The institution of anti-retroviral therapy (ART) restores CD4⁺ T cell responses to many pathogens, but HIV-specific responses remain deficient. Similarly, therapeutic immunization with HIV antigens of chronically infected, ART treated subjects results in poor induction of HIV-specific CD4 responses. In this study, we used a macaque model of ART treatment during chronic infection to study the virologic consequences of SIV antigen stimulation in lymph nodes early after immunization. Rhesus CMV (RhCMV) seropositive, Mamu A*01 positive rhesus macaques were chronically infected with SIVmac251 and treated with ART. The immune and viral responses to SIV gag and RhCMV pp65 antigen immunization in draining lymph nodes and peripheral blood were analyzed. Animals were immunized on contralateral sides with SIV gag and RhCMV pp65 encoding plasmids, which allowed lymph nodes draining each antigen to be obtained at the same time from the same animal for direct comparison.

Results

We observed that both SIV and RhCMV immunizations stimulated transient antigen-specific T cell responses in draining lymph nodes. The RhCMV-specific responses were potent and sustained (50 days post-immunization) in the periphery, while the SIV-specific responses were transient and extinguished quickly. The SIV antigen stimulation selectively induced transient SIV replication in draining lymph nodes.

Conclusions

The data are consistent with a model whereby viral replication in response to SIV antigen stimulation limits the generation of SIV antigen-specific responses and suggests a potential mechanism for the early loss and poor HIV-specific CD4⁺ T cell response observed in HIV-infected individuals.

Multivalent smallpox DNA vaccine delivered by intradermal electroporation drives protective immunity in nonhuman primates against lethal monkeypox challenge

The threat of a smallpox-based bioterrorist event or a human monkeypox outbreak has heightened the importance of new, safe vaccine approaches for these pathogens to complement older poxviral vaccine platforms. As poxviruses are large, complex viruses, they present technological challenges for simple recombinant vaccine development where a multicomponent mixtures of vaccine antigens are likely important in protection. We report that a synthetic, multivalent, highly concentrated, DNA vaccine delivered by a minimally invasive, novel skin electroporation microarray can drive polyvalent immunity in macaques, and offers protection from a highly pathogenic monkeypox challenge. Such a diverse, high-titer antibody response produced against 8 different DNA-encoded antigens delivered simultaneously in microvolumes has not been previously described. These studies represent a significant improvement in the efficiency of the DNA vaccine platform, resulting in immune responses that mimic live viral infections, and would likely have relevance for vaccine design against complex human and animal pathogens.

Human immunodeficiency virus-1 vaccine design: where do we go now?

Numerous human immunodeficiency virus (HIV)-1 vaccines have been developed over the last three decades, but to date an effective HIV-1 vaccine that can be used for prophylactic or therapeutic purposes in humans has not been identified. The failures and limited successes of HIV-1 vaccines have highlighted the gaps in our knowledge with regard to fundamental immunity against HIV-1 and have provided insights for vaccine strategies that may be implemented for designing more effective HIV-1 vaccines in the future. Recent studies have shown that robust mucosal immunity, high avidity and polyfunctional T cells, and broadly neutralizing antibodies are important factors governing the induction of protective immunity against HIV-1. Furthermore, optimization of vaccine delivery methods for DNA or live viral vector-based vaccines, elucidating the immune responses of individuals who remain resistant to HIV-1 infections and also understanding the core immune responses mediating protection against simian immunodeficiency viruses (SIV) and HIV-1 in animal models following vaccination, are key aspects to be regarded for designing more effective HIV-1 vaccines in the future.

Unique Th1/Th2 phenotypes induced during priming and memory phases by use of interleukin-12 (IL-12) or IL-28B vaccine adjuvants in rhesus macaques

Adjuvant compounds are usually included in vaccinations in order to bolster total vaccine-specific responses or to tailor an immune response toward a desired endpoint, such as the production of gamma interferon or an increase in antibody titers. While most adjuvants are studied in regard to their impact on vaccine-specific responses during and just after the vaccination period, a detailed analysis of how adjuvants skew the Th1/Th2 axis at more distant time points is not often undertaken. In the current study, we present data that suggests that adjuvants differ in their relative abilities to bolster and skew immune responses in the short term compared with more distant time points. To that end, we have employed interleukin-12 (IL-12) and IL-28B as adjuvants for DNA vaccination of rhesus macaques. While both adjuvants were able to bolster Th1-biased responses, our analysis shows that this skewing was achieved through different mechanisms. Moreover, analysis 3 months after the final immunization revealed the activity of the IL-12 adjuvant to be short lived, while the IL-28B adjuvant continued to exert its influence on the immune system. Taken together, these data suggest that the scientific and medical communities would benefit from a more detailed analysis of adjuvant function, including the determination of long-term influences of administered adjuvants.

IL-28B/IFN-lambda 3 drives granzyme B loading and significantly increases CTL killing activity in macaques

Type III/lambda interferons (IFNs) were discovered less than a decade ago and are still in the process of being characterized. Although previous studies have focused on the function of IFN-lambda 3 (also known as interleukin (IL)-28B) in a small animal model, it is unknown whether these functions would translate to a larger, more relevant model. Thus in the present study, we have used DNA vaccination as a method of studying the influence of IFN-lambda 3 on adaptive immune responses in rhesus macaques. Results of our study show for the first time that IFN-lambda 3 has significant influence on antigen-specific CD8(+) T-cell function, especially in regards to cytotoxicity. Peripheral CD8(+) T cells from animals that were administered IFN-lambda 3 showed substantially increased cytotoxic responses as gauged by CD107a and granzyme B coexpression as well as perforin release. Moreover, CD8(+) T cells isolated from the mesenteric lymph nodes (MLN) of animals receiving IFN-lambda 3 loaded significant amounts of granzyme B upon extended antigenic stimulation and induced significantly more granzyme B-mediated cell death of peptide pulsed targets. These data suggest that IFN-lambda 3 is a potent effector of the immune system with special emphasis on CD8(+) T-cell killing functions which warrants further study as a possible immunoadjuvant.

Viral reservoir is suppressed but not eliminated by CD8 vaccine specific lymphocytes

It has long been postulated that while CD8 lymphocytes are capable of suppressing human immunodeficiency virus (HIV)-1 replication it is unlikely that the viral reservoirs once formed can be cleared. Our previous studies demonstrate that co-immunizing cynomologous macaques with a simian/human immunodeficiency virus (SHIV) DNA-based vaccines induces a strong cellular immune response that is able to suppress viral replication. We further demonstrated that interleukin (IL)-12 could significantly enhance the vaccine specific CD8 lymphocyte response. In this manuscript cynomologous macaques were vaccinated with a SHIV DNA-based vaccine co-delivered with IL-12. The macaques were then challenged with SHIV89.6p. Two years post-immunization and viral challenge we transiently depleted CD8(+) T cells. Plasma viral load increased, demonstrating the central role of CD8(+) T cells in viral suppression yet an inability to clear the viral reservoirs. Furthermore, in the data presented here, we found a higher number of IFN-gamma producing vaccine specific cells did not enhance suppression of viral replication.

Engineering superior DNA vaccines: MHC class I single chain trimers bypass antigen processing and enhance the immune response to low affinity antigens

It is commonly believed that delivery of antigen into the class I antigen presentation pathway is a limiting factor in the clinical translation of DNA vaccines. This is of particular concern in the context of cancer vaccine development as many immunodominant peptides derived from self tumor antigens are not processed and presented efficiently. To address this limitation, we have engineered completely assembled peptide/MHC class I complexes whereby all three components (class I heavy chain, beta(2)m, and peptide) are attached by flexible linkers and expressed as a single polypeptide (single chain trimers or SCT). In this study, we tested the efficacy of progressive generations of SCT DNA vaccines engineered to (1) enhance peptide binding, (2) enhance interaction with the CD8 coreceptor, and/or (3) activate CD4(+) helper T cells. Disulfide trap SCT (dtSCT) have been engineered to improve peptide binding, with mutations designed to create a disulfide bond between the class I heavy chain and the peptide linker. dtSCT DNA vaccines dramatically enhance the immune response to model low affinity antigens as measured by ELISPOT analysis and tumor challenge. SCT engineered to enhance interaction with the CD8 coreceptor have a higher affinity for the TCR/CD8 complex, and are associated with more robust CD8(+) T cell responses following vaccination. Finally, SCT constructs that coexpress a universal helper epitope PADRE, dramatically enhance CD8(+) T cell responses. Taken together, our data demonstrate that dtSCT DNA vaccines coexpressing a universal CD4 epitope are highly effective in generating immune responses to poorly processed and presented cancer antigens.