Intramuscular Electroporation Research Articles

An LASV GPC pseudotyped virus based reporter system enables evaluation of vaccines in mice under non-BSL-4 conditions.

Lassa virus (LASV) causes a severe hemorrhagic fever endemic throughout western Africa. Because of the ability to cause lethal disease in humans, limited treatment options, and potential as a bioweapon, the need for vaccines to prevent LASV epidemic is urgent. However, LASV vaccine development has been hindered by the lack of appropriate small animal models for efficacy evaluation independent of biosafety level four (BSL-4) facilities. Here we generated an LASV-glycoprotein precursor (GPC)-pseudotyped Human immunodeficiency virus containing firefly luciferase (Fluc) reporter gene as surrogate to develop a bioluminescent-imaging-based BALB/c mouse model for one-round infection under non-BSL-4 conditions, in which the bioluminescent intensity of Fluc was utilized as endpoint when evaluating vaccine efficacy. Electron microscopy analysis demonstrated that LASV GPC pseudotyped virus appeared structurally similar to native virion. Meanwhile, we constructed DNA vaccine (pSV1.0-LASVGPC) and pseudoparticle-based vaccine (LASVpp) that displayed conformational GPC protein of LASV strain Josiah to vaccinate BALB/c mice using intramuscular electroporation and by intraperitoneal routes, respectively. Vaccinated mice in LASVpp alone and DNA prime+LASVpp boost schedules were protected against 100 AID50 of LASV pseudovirus challenge, and it was found that in vivo efficiencies correlated with their anti-LASV neutralizing activities and MCP-1 cytokine levels in serum sampled before infection. The bioluminescence pseudovirus infection model can be useful tool for the preliminary evaluation of immunogenicity and efficacy of vaccine candidates against LASV outside of BSL-4 containments, and the results with pseudoparticle-based vaccine provided very helpful information for LASV vaccine design.

Effective Protection Induced by a Monovalent DNA Vaccine against Dengue Virus (DV) Serotype 1 and a Bivalent DNA Vaccine against DV1 and DV2 in Mice.

Dengue virus (DV) is the causal pathogen of dengue fever, which is one of the most rapidly spread mosquito-borne disease worldwide and has become a severe public health problem. Currently, there is no specific treatment for dengue; thus, a vaccine would be an effective countermeasure to reduce the morbidity and mortality. Although, the chimeric Yellow fever dengue tetravalent vaccine has been approved in some countries, it is still necessary to develop safer, more effective, and less costly vaccines. In this study, a DNA vaccine candidate pVAX1-D1ME expressing the prME protein of DV1 was inoculated in BALB/c mice via intramuscular injection or electroporation, and the immunogenicity and protection were evaluated. Compared with traditional intramuscular injection, administration with 50 μg pVAX1-D1ME via electroporation with three immunizations induced persistent humoral and cellular immune responses and effectively protected mice against lethal DV1 challenge. In addition, immunization with a bivalent vaccine consisting of pVAX1-D1ME and pVAX1-D2ME via electroporation generated a balanced IgG response and neutralizing antibodies against DV1 and DV2 and could protect mice from lethal challenge with DV1 and DV2. This study sheds new light on developing a dengue tetravalent DNA vaccine.

Protection and durable humoral and cellular immune responses in cynomolgus macaques following administration of a Zaire Ebola virus (EBOV) GP DNA vaccine delivered by intramuscular or intradermal electroporation

Abstract The 2013–2016 Ebola virus disease (EVD) was the first time that the spread of the virus reached epidemic status. There are no licensed vaccines; however the most advanced candidate rVSV-ZEBOV vaccine, is a live-attenuated vesicular stomatitis virus encoding the Ebola virus glycoprotein (GP), and has demonstrated efficacy in a ring-vaccination trial. However, several EVD viral vector vaccine trials have reported adverse events that could limit administration to certain populations. The establishment of robust anamnestic responses has yet to be fully understood with these candidates and may be limited by potential anti-vector immunity. We designed EVD DNA vaccines as an alternative platform with a remarkable safety profile that is serology independent, allowing for possible repeat vector administration. We designed 3 novel synthetic Zaire Ebola virus (EBOV) GP DNA sequences which were tested alone or as multivalent formulations delivered by in vivo intramuscular (IM) or intradermal (ID) electroporation (EP). The EBOV-GP DNA vaccines were highly protective against lethal EBOV-Makona challenge in cynomolgus macaques, with 100% protection in NHPs receiving vaccine by ID-EP delivery and 75% protection in NHPs receiving 2 doses IM-EP. Vaccinated NHPs had no detectable viremia following challenge. Animals (n=4–5/group) injected with different IM-EP or ID-EP DNA regimens were followed to monitor long-term immunogenicity. NHPs have durable total IgG antibody titers and T cells responses to EBOV GP antigen, including polyfunctional CD4 and CD8 T cells and responses in memory subset populations. Together, the data strong support EBOV-GP DNA vaccine delivery for protection and the generation of robust memory immune responses.

Fusion of the dendritic cell-targeting chemokine MIP3α to melanoma antigen Gp100 in a therapeutic DNA vaccine significantly enhances immunogenicity and survival in a mouse melanoma model

BackgroundAlthough therapeutic cancer vaccines have been mostly disappointing in the clinic, the advent of novel immunotherapies and the future promise of neoantigen-based therapies have created the need for new vaccine...

Immunogenicity and malaria transmission reducing potency of Pfs48/45 and Pfs25 encoded by DNA vaccines administered by intramuscular electroporation

Pfs48/45 and Pfs25 are leading candidates for the development of Plasmodium falciparum transmission blocking vaccines (TBV). Expression of Pfs48/45 in the erythrocytic sexual stages and presentation to the immune system during infection in the human host also makes it ideal for natural boosting. However, it has been challenging to produce a fully folded, functionally active Pfs48/45, using various protein expression platforms. In this study, we demonstrate that full-length Pfs48/45 encoded by DNA plasmids is able to induce significant transmission reducing immune responses. DNA plasmids encoding Pfs48/45 based on native (WT), codon optimized (SYN), or codon optimized and mutated (MUT1 and MUT2), to prevent any asparagine (N)-linked glycosylation were compared with or without intramuscular electroporation (EP). EP significantly enhanced antibody titers and transmission blocking activity elicited by immunization with SYN Pfs48/45 DNA vaccine. Mosquito membrane feeding assays also revealed improved functional immunogenicity of SYN Pfs48/45 (N-glycosylation sites intact) as compared to MUT1 or MUT2 Pfs48/45 DNA plasmids (all N-glycosylation sites mutated). Boosting with recombinant Pfs48/45 protein after immunization with each of the different DNA vaccines resulted in significant boosting of antibody response and improved transmission reducing capabilities of all four DNA vaccines. Finally, immunization with a combination of DNA plasmids (SYN Pfs48/45 and SYN Pfs25) also provides support for the possibility of combining antigens targeting different life cycle stages in the parasite during transmission through mosquitoes.

A Phase 1 clinical trial of a DNA vaccine for Venezuelan equine encephalitis delivered by intramuscular or intradermal electroporation

Venezuelan equine encephalitis virus (VEEV), a mosquito-borne alphavirus, causes periodic epizootics in equines and is a recognized biological defense threat for humans. There are currently no FDA-licensed vaccines against VEEV. We developed a candidate DNA vaccine expressing the E3-E2-6K-E1 genes of VEEV (pWRG/VEE) and performed a Phase 1 clinical study to assess the vaccine's safety, reactogenicity, tolerability, and immunogenicity when administered by intramuscular (IM) or intradermal (ID) electroporation (EP) using the Ichor Medical Systems TriGrid™ Delivery System. Subjects in IM-EP groups received 0.5mg (N=8) or 2.0mg (N=9) of pWRG/VEE or a saline placebo (N=4) in a 1.0ml injection. Subjects in ID-EP groups received 0.08mg (N=8) or 0.3mg (N=8) of DNA or a saline placebo (N=4) in a 0.15ml injection. Subjects were monitored for a total period of 360 days. No vaccine- or device-related serious adverse events were reported. Based on the results of a subject questionnaire, the IM- and ID-EP procedures were both considered to be generally acceptable for prophylactic vaccine administration, with the acute tolerability of ID EP delivery judged to be greater than that of IM-EP delivery. All subjects (100%) in the high and low dose IM-EP groups developed detectable VEEV-neutralizing antibodies after two or three administrations of pWRG/VEE, respectively. VEEV-neutralizing antibody responses were detected in seven of eight subjects (87.5%) in the high dose and five of eight subjects (62.5%) in the low dose ID-EP groups after three vaccine administrations. There was a correlation between the DNA dose and the magnitude of the resulting VEEV-neutralizing antibody responses for both IM and ID EP delivery. These results indicate that pWRG/VEE delivered by either IM- or ID-EP is safe, tolerable, and immunogenic in humans at the evaluated dose levels.Clinicaltrials.gov registry number NCT01984983.

433. DNA Monoclonal Antibodies Target Influenza Virus In Vivo

Despite promising innovations, influenza vaccines and antiviral drugs fail to provide full protection from seasonal infection, and provide little defense against novel and potentially pandemic viral strains. Broadly cross-protective monoclonal antibodies have been developed with the aim of providing protection against highly divergent influenza viruses. However, the utility of delivering purified protein antibody as therapy or prophylaxis against influenza is limited, especially in pandemic settings. Use of gene therapy to generate monoclonal antibodies in vivo provides a simplified, flexible, and relatively inexpensive alternative to protein antibody treatment.In this study, we used intramuscular electroporation of plasmid DNA encoding immunoglobulin to express DNA monoclonal antibodies (DMAb) against influenza hemagglutinin (HA) surface protein in mice. Multiple aspects of plasmid construction, antibody design, and delivery were optimized to enhance expression of DMAb from muscle cells in vivo. We investigated multiple antibody clones, including the broadly-neutralizing anti-influenza-H1 antibody 5J8. The 5J8 DMAb was expressed at µg/mL levels in serum of both nude and immune-competent mice. Serum DMAb produced from muscle in vivo were functional in vitro - with the ability to bind influenza HA, block hemagglutination of red blood cells, and neutralize influenza virus. Serum DMAb expression levels approximate those required for protection. Influenza challenge studies of mice treated with 5J8 DMAb are underway.DMAb provide an important new approach to immune therapy. DNA has an excellent safety profile and averts challenges of pre-existing serology associated with many viral vectors. Here, we demonstrate that DNA can be used to deliver consistently high levels of potent monoclonal antibodies for protection against a viral pathogen.

Wilms’ tumour antigen 1 Immunity via DNA fusion gene vaccination in haematological malignancies by intramuscular injection followed by intramuscular electroporation: a Phase II non-randomised clinical trial (WIN)

BackgroundIn the UK almost 7000 people are diagnosed with leukaemia each year, but despite continuing advances in diagnosis and treatment with new drugs, such as the tyrosine kinase inhibitors, the majority of these patients will eventually die from their disease. Until quite recently, the only treatment to offer the possibility of long-term disease-free survival was allogeneic stem cell transplantation. However, this carries a substantial risk of mortality and is available to only a minority of patients.ObjectivesThe aim of the study was to test the hypothesis that molecular and clinical responses, induced by T lymphocytes (T cells), can be predicted by increases in the number of CD8+ (cluster of differentiation 8-positive) T cells specific for the vaccine-encoded T-cell epitopes. This project also aimed to build on the established programme of deoxyribonucleic acid (DNA) fusion-gene vaccination delivered by intramuscular injection, exploiting a unique experience with electroporation, to induce durable immune responses with the aim of controlling disease by precision attack of the tumour by CD8+ T cells.MethodA non-randomised, open-label, single-dose-level Phase II clinical trial in two patient groups [chronic myeloid leukaemia (CML) and acute myeloid leukaemia (AML)] on stable doses of imatinib. Human leucocyte antigen A2-positive (HLA A2+) patients were vaccinated with two DNA vaccines: (1) p.DOM–WT1-37 (epitope sequence: VLDFAPPGA); and (2) p.DOM–WT1-126 (epitope sequence: RMFPNAPYL). The HLA A2-negative patients formed an unvaccinated control group. The sample size for the HLA A2+ group was originally determined following Simon’s optimal Phase II trial design (Simon R. Optimal two-stage designs for phase II clinical trials.Control Clin Trials1989;10:1–10). This was changed to A’Hern’s single-stage design during the course of the trial (A’Hern RP. Sample size tables for single-stage phase II designs.Stat Med2001;20:859–66), which was endorsed by the trial’s independent oversight committees.ResultsThe study included 12 patients with CML who were vaccinated and nine patients with CML who were unvaccinated as the control group. Both the vaccines and the electroporation were safe, with no new or unexpected toxicities. The evaluation adverse events of special interest (heart, bone marrow, renal) did not reveal safety concerns. TwoBCR–ABL(breakpoint cluster region–Abelson murine leukaemia viral oncogene homolog 1) responses were observed, both of which were defined as a major response, with one in each group. Two Wilms’ tumour antigen 1 (WT1) molecular responses were observed in the vaccinated group and one was observed in the control group. At an immunological level, the vaccine performed as expected.ConclusionsThe study met its primary decision-making target with one major molecular response inBCR–ABLtranscript levels. Overall, the data showed, in this clinical setting, the immunogenicity and safety of the vaccine.LimitationsThe study did not complete recruitment and there were multiple hurdles that contributed to this failure. This is disappointing given the robust induction immune responses againstWT1T-cell responses in 7 out of 10 evaluable patients.Future workEvaluation of the p.DOM–WT1 vaccines in AML remains attractive clinically, but it is unlikely to be feasible at this time. Combination of the DNA vaccine approach with strategies to expand T-cell responses with immunomodulatory antibodies is in development.Funding detailsThis project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a Medical Research Council (MRC) and National Institute for Health Research (NIHR) partnership, and Bloodwise.

DNA Vaccines: A Strategy for Developing Novel Multivalent TB Vaccines.

Multivalent DNA vaccines that are delivered by electroporation (EP) through muscle tissue provide a novel method for eliciting immunity against tuberculosis (TB) as well as a broad range of diseases including HIV and cancers. Proper plasmid construction containing suitable protective TB antigens capable of evoking desired vaccine-induced responses would lead to the appropriate induction of both humoral and cellular immunity. DNA vaccines are safe and of low cost in comparison to traditional vaccines while also providing potentially effective prophylactic or therapeutic modalities against currently untreatable diseases. Here, we describe the steps for developing a rational multivalent TB DNA vaccine delivered with intramuscular EP in mice.

Human Polyclonal Antibodies Produced through DNA Vaccination of Transchromosomal Cattle Provide Mice with Post-Exposure Protection against Lethal Zaire and Sudan Ebolaviruses.

DNA vaccination of transchromosomal bovines (TcBs) with DNA vaccines expressing the codon-optimized (co) glycoprotein (GP) genes of Ebola virus (EBOV) and Sudan virus (SUDV) produce fully human polyclonal antibodies (pAbs) that recognize both viruses and demonstrate robust neutralizing activity. Each TcB was vaccinated by intramuscular electroporation (IM-EP) a total of four times and at each administration received 10 mg of the EBOV-GPco DNA vaccine and 10 mg of the SUDV-GPco DNA vaccine at two sites on the left and right sides, respectively. After two vaccinations, robust antibody responses (titers > 1000) were detected by ELISA against whole irradiated EBOV or SUDV and recombinant EBOV-GP or SUDV-GP (rGP) antigens, with higher titers observed for the rGP antigens. Strong, virus neutralizing antibody responses (titers >1000) were detected after three vaccinations when measured by vesicular stomatitis virus-based pseudovirion neutralization assay (PsVNA). Maximal neutralizing antibody responses were identified by traditional plaque reduction neutralization tests (PRNT) after four vaccinations. Neutralizing activity of human immunoglobulins (IgG) purified from TcB plasma collected after three vaccinations and injected intraperitoneally (IP) into mice at a 100 mg/kg dose was detected in the serum by PsVNA up to 14 days after administration. Passive transfer by IP injection of the purified IgG (100 mg/kg) to groups of BALB/c mice one day after IP challenge with mouse adapted (ma) EBOV resulted in 80% protection while all mice treated with non-specific pAbs succumbed. Similarly, interferon receptor 1 knockout (IFNAR -/-) mice receiving the purified IgG (100 mg/kg) by IP injection one day after IP challenge with wild type SUDV resulted in 89% survival. These results are the first to demonstrate that filovirus GP DNA vaccines administered to TcBs by IM-EP can elicit neutralizing antibodies that provide post-exposure protection. Additionally, these data describe production of fully human IgG in a large animal system, a system which is capable of producing large quantities of a clinical grade therapeutic product.

Skin Transfection Patterns and Expression Kinetics of Electroporation-Enhanced Plasmid Delivery Using the CELLECTRA-3P, a Portable Next-Generation Dermal Electroporation Device.

The CELLECTRA-3P dermal electroporation device (Inovio Pharmaceuticals, Plymouth Meeting, PA) has been evaluated in the clinic and shown to enhance the delivery of an influenza DNA vaccine. To understand the mechanism by which this device aids in enhancing the host immune response to DNA vaccines we investigated the expression kinetics and localization of a reporter plasmid (pGFP) delivered via the CELLECTRA-3P. Histological analysis revealed green fluorescent protein (GFP) expression as early as 1 hr posttreatment in the epidermal and dermal layers, and as early as 2 hr posttreatment in the subdermal layers. Immunofluorescence techniques identified keratinocytes, fibrocytes, dendritic-like cells, adipocytes, and myocytes as the principal cell populations transfected. We proceeded to demonstrate elicitation of robust host immune responses after plasmid DNA (pDNA) vaccination. In guinea pigs equivalent humoral (antibody binding titers) immune responses were observed between protocols using either CELLECTRA-3P or intramuscular electroporation to deliver the DNA vaccine. In nonhuman primates, robust interferon-γ enzyme-linked immunospot and protective levels of hemagglutination inhibition titers after pDNA vaccination were observed in groups treated with the CELLECTRA-3P. In conclusion, these findings may assist in the future to design efficient, tolerable DNA vaccination strategies for the clinic.

Abstract 2511: Therapeutic dendritic cell targeting MIP3α-gp100 DNA vaccination with immunomodulatory αIL-10 and αPD-1 antibodies significantly enhances survival in a mouse melanoma model system

Abstract The current study demonstrates that the combination of a DNA vaccine encoding the chemokine MIP-3α fused to melanoma antigen gp100 with immunomodulatory antibodies prolongs survival in a melanoma mouse model. The current studies utilize the B16F10 mouse spontaneous melanoma syngeneic transplantable mouse model system. Previous published work with this vaccine platform has indicated the MIP-3α component targets nascent peptides to immature dendritic cells leading to processing by class I and class II MHC pathways. It has further been shown in this tumor system that prophylactic vaccination with the DNA construct alone delayed tumor growth. Other studies have provided evidence that αPD-1 or αIL-10 neutralizing antibodies enhance immunological melanoma therapies by modulating the tolerogenic tumor microenvironment. First, this study expanded previous results by finding a significant decrease in tumor burden and increase in survival by prophylactic intramuscular electroporation [IM EP] of the DNA vaccine construct. Adding three therapeutic doses of αIL-10 given subcutaneously [subQ] at the tumor site to the treatment further increased mouse survival. The development of cell-mediated and humoral immune responses were documented for the first time in this system by Elispot and in-cell ELISA assays. Secondly, a novel therapeutic vaccination protocol was developed by initiating vaccination and antibody therapies after tumor challenge. With this therapeutic protocol, we demonstrated for the first time that vaccine significantly delays tumor burden and increases median survival from 17 to 21 days (p = 0.006). Addition of αIL-10 (subQ) and αPD-1 (intra-peritoneally) antibodies led to further highly significant decreases in tumor burden and increased median survival from 17 to 25 days (p = 0.0005). Efficient targeting of antigen to immature dendritic cells with a chemokine fusion vaccine offers a potential alternative approach to the ex vivo dendritic cell antigen loading protocols currently undergoing clinical investigation. Combining this approach with agents able to modulate the tolerogenic tumor microenvironment offers promise as a novel melanoma therapy. Citation Format: James Gordy, Richard B. Markham. Therapeutic dendritic cell targeting MIP3α-gp100 DNA vaccination with immunomodulatory αIL-10 and αPD-1 antibodies significantly enhances survival in a mouse melanoma model system. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2511. doi:10.1158/1538-7445.AM2015-2511

Increased B and T Cell Responses in M. bovis Bacille Calmette-Guérin Vaccinated Pigs Co-Immunized with Plasmid DNA Encoding a Prototype Tuberculosis Antigen.

The only tuberculosis vaccine currently available, bacille Calmette-Guérin (BCG) is a poor inducer of CD8+ T cells, which are particularly important for the control of latent tuberculosis and protection against reactivation. As the induction of strong CD8+ T cell responses is a hallmark of DNA vaccines, a combination of BCG with plasmid DNA encoding a prototype TB antigen (Ag85A) was tested. As an alternative animal model, pigs were primed with BCG mixed with empty vector or codon-optimized pAg85A by the intradermal route and boosted with plasmid delivered by intramuscular electroporation. Control pigs received unformulated BCG. The BCG-pAg85A combination stimulated robust and sustained Ag85A specific antibody, lymphoproliferative, IL-6, IL-10 and IFN-γ responses. IgG1/IgG2 antibody isotype ratio reflected the Th1 helper type biased response. T lymphocyte responses against purified protein derivative of tuberculin (PPD) were induced in all (BCG) vaccinated animals, but responses were much stronger in BCG-pAg85A vaccinated pigs. Finally, Ag85A-specific IFN-γ producing CD8+ T cells were detected by intracellular cytokine staining and a synthetic peptide, spanning Ag85A131-150 and encompassing two regions with strong predicted SLA-1*0401/SLA-1*0801 binding affinity, was promiscuously recognized by 6/6 animals vaccinated with the BCG-pAg85A combination. Our study provides a proof of concept in a large mammalian species, for a new Th1 and CD8+ targeting tuberculosis vaccine, based on BCG-plasmid DNA co-administration.

Codon-optimized filovirus DNA vaccines delivered by intramuscular electroporation protect cynomolgus macaques from lethal Ebola and Marburg virus challenges

Cynomolgus macaques were vaccinated by intramuscular electroporation with DNA plasmids expressing codon-optimized glycoprotein (GP) genes of Ebola virus (EBOV) or Marburg virus (MARV) or a combination of codon-optimized GP DNA vaccines for EBOV, MARV, Sudan virus and Ravn virus. When measured by ELISA, the individual vaccines elicited slightly higher IgG responses to EBOV or MARV than did the combination vaccines. No significant differences in immune responses of macaques given the individual or combination vaccines were measured by pseudovirion neutralization or IFN-γ ELISpot assays. Both the MARV and mixed vaccines were able to protect macaques from lethal MARV challenge (5/6 vs. 6/6). In contrast, a greater proportion of macaques vaccinated with the EBOV vaccine survived lethal EBOV challenge in comparison to those that received the mixed vaccine (5/6 vs. 1/6). EBOV challenge survivors had significantly higher pre-challenge neutralizing antibody titers than those that succumbed.

An adjuvant clinical trial of SCIB1, a DNA vaccine that targets dendritic cells in vivo, in fully resected melanoma patients.

SCIB1 is a DNA vaccine encoding a human IgG1 antibody, with T cell epitopes from gp100 and TRP-2 antigens engineered into its CDRs. It targets dendritic cells in vivo via the high affinity Fc receptor. A clinical trial in stage III/IV melanoma patients showed that doses of 2-8 mg could induce T cell responses in 7/9 patients with no associated toxicity. Overall median survival was 24 months. In this study SCIB1 is used as an adjuvant therapy. Methods: 16 patients with fully resected stage III (9) or stage IV (7) melanoma, were immunised with SCIB1 by Intramuscular electroporation at 0, 3, 6, 12 and 24 weeks. Patients tolerating treatment were allowed to continue treatment for up to 5 years. Results: Thirteen patients received 4mg doses of SCIB1 on 5 occasions and one received 4 doses of 4mg followed by one dose of 2mg. One patient only tolerated administration of three 2mg doses of SCIB1. One patient received three 2mg doses and then two 4mg doses. Seven patients received additional doses of SCIB1. One patient received 3 doses prior to withdrawal due to disease progression and one patient received 5 doses. The other six patients remain on continuation: three have received 5 doses and two have received 6 doses of SCIB1. Apart from soreness at the injection site, there have been no significant toxicities. All sixteen patients showed an epitope specific proliferation response ex vivo and an IFN Elispot response in-vitroafter T cell expansion. Eleven patients responded to all 4 epitopes, three patients to 3 epitopes, one patients to 2 epitopes and one patients to 1 epitope. All patients with continued treatment showed strong T cell memory responses. Currently patients have a median survival time from trial entry of 29.5 months and from diagnosis of metastases of 34 months. Progression free survival is 78% and 72% for stage III and IV respectively and overall survival is 100% for both groups. Only 4 patients have relapsed at 4, 14, 18 and 18 months, since the last relapse there have been no further recurrences for 23 months. Conclusions: These results suggest that SCIB1 may confer protection from recurrence of melanoma with little associated toxicity. This vaccine deserves further evaluation as an adjuvant therapy. Clinical trial information: 2009-017355-10.

Intradermal DNA Electroporation Induces Cellular and Humoral Immune Response and Confers Protection against HER2/neu Tumor.

Skin represents an attractive target for DNA vaccine delivery because of its natural richness in APCs, whose targeting may potentiate the effect of vaccination. Nevertheless, intramuscular electroporation is the most common delivery method for ECTM vaccination. In this study we assessed whether intradermal administration could deliver the vaccine into different cell types and we analyzed the evolution of tissue infiltrate elicited by the vaccination protocol. Intradermal electroporation (EP) vaccination resulted in transfection of different skin layers, as well as mononuclear cells. Additionally, we observed a marked recruitment of reactive infiltrates mainly 6–24 hours after treatment and inflammatory cells included CD11c+. Moreover, we tested the efficacy of intradermal vaccination against Her2/neu antigen in cellular and humoral response induction and consequent protection from a Her2/neu tumor challenge in Her2/neu nontolerant and tolerant mice. A significant delay in transplantable tumor onset was observed in both BALB/c (p ≤ 0,0003) and BALB-neuT mice (p = 0,003). Moreover, BALB-neuT mice displayed slow tumor growth as compared to control group (p < 0,0016). In addition, while in vivo cytotoxic response was observed only in BALB/c mice, a significant antibody response was achieved in both mouse models. Our results identify intradermal EP vaccination as a promising method for delivering Her2/neu DNA vaccine.

Long-term central and effector SHIV-specific memory T cell responses elicited after a single immunization with a novel lentivector DNA vaccine.

Prevention of HIV acquisition and replication requires long lasting and effective immunity. Given the state of HIV vaccine development, innovative vectors and immunization strategies are urgently needed to generate safe and efficacious HIV vaccines. Here, we developed a novel lentivirus-based DNA vector that does not integrate in the host genome and undergoes a single-cycle of replication. Viral proteins are constitutively expressed under the control of Tat-independent LTR promoter from goat lentivirus. We immunized six macaques once only with CAL-SHIV-IN− DNA using combined intramuscular and intradermal injections plus electroporation. Antigen-specific T cell responses were monitored for 47 weeks post-immunization (PI). PBMCs were assessed directly ex vivo or after 6 and 12 days of in vitro culture using antigenic and/or homeostatic proliferation. IFN-γ ELISPOT was used to measure immediate cytokine secretion from antigen specific effector cells and from memory precursors with high proliferative capacity (PHPC). The memory phenotype and functions (proliferation, cytokine expression, lytic content) of specific T cells were tested using multiparametric FACS-based assays. All immunized macaques developed lasting peripheral CD8+ and CD4+ T cell responses mainly against Gag and Nef antigens. During the primary expansion phase, immediate effector cells as well as increasing numbers of proliferating cells with limited effector functions were detected which expressed markers of effector (EM) and central (CM) memory phenotypes. These responses contracted but then reemerged later in absence of antigen boost. Strong PHPC responses comprising vaccine-specific CM and EM T cells that readily expanded and acquired immediate effector functions were detected at 40/47 weeks PI. Altogether, our study demonstrated that a single immunization with a replication-limited DNA vaccine elicited persistent vaccine-specific CM and EM CD8+ and CD4+ T cells with immediate and readily inducible effector functions, in the absence of ongoing antigen expression.

Abstract 160: CD8+T cell-specific induction of NKG2D receptor by doxorubicin plus interleukin-12 requires the engagement of CD80 and CD28

Abstract Background: Increased infiltration of CD8+T cells into tumors inhibits tumor progression, in which natural killer group 2, member D receptor (NKG2D) plays a key role. At previous meetings, we have presented data showing that NKG2D can be induced on CD8+T through treatment with interleukin (IL)-12 plus doxorubicin (Dox), and that infiltration of this subpopulation of effector cells into tumors is associated with increased antitumor efficacy of treatment with IL-12 plus Dox. The mechanisms of both NKG2D induction and the tumor-specific infiltration were unknown. This year, we reveal the mechanism of NKG2D positive CD8+T infiltration into the tumor microenvironment. Methods: We administered Dox, IL-12 plasmid DNA, or both via intraperitoneal injection or intramuscular electroporation into tumor-bearing wild-type C57bl/6 mice or CD28 knockout mice. Control siRNA or CD80 siRNA were administered via intratumoral injection followed by electroporation. Induction of NKG2D in CD8+T cells was analyzed using flow cytometry. Cell death in tumors after each treatment was examined using the TUNEL assay. Antitumor cytolytic activity of CD8+T cells was examined using the CTL assay. NKG2D-positive CD8+T cell-specific localization in tumors was examined using immunofluorescence staining. Results: Treatment with Dox plus IL-12 specifically increased expression of NKG2D in CD8+T cells. This induced NKG2D expression in CD8+T cells was associated with increased accumulation of NKG2D-positive CD8+T cells in murine tumors, as well as with increased antitumor cytotoxicity in vitro and tumor cell death in vivo. Administration of NKG2D-blocking antibody completely abrogated the antitumor immune response. Knocking down CD80 in tumor cells or using CD28 knockout mice not only abolished the induction of NKG2D in CD8+T cells, but also abrogated the accumulation of NKG2D-positive CD8+T cells in tumors. Accumulation of NKG2D-positive CD8+T cells in tumors was dependent on the engagement of CD28 in CD8+T cells and CD80 in tumor cells. Conclusion: We conclude that treatment with IL-12 plus Dox induces NKG2D in CD8+T cells in vivo and boosts NKG2D+CD8+T-dependent antitumor immune surveillance. Induction of NKG2D and accumulation of NKG2D-positive CD8+T cells in tumors is dependent on the engagement of CD28 in CD8+T cells and CD80 in tumor cells. This discovery reveals a novel mechanism showing how chemo-immune therapy synergistically promotes T-cell-mediated antitumor immune surveillance. Citation Format: Jiemiao Hu, Xueqing Xia, Liangfang Zhang, Eugenie S. Kleinerman, Shulin Li. CD8+T cell-specific induction of NKG2D receptor by doxorubicin plus interleukin-12 requires the engagement of CD80 and CD28. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 160. doi:10.1158/1538-7445.AM2014-160

Induction of neutralizing antibody response against four dengue viruses in mice by intramuscular electroporation of tetravalent DNA vaccines.

DNA vaccine against dengue is an interesting strategy for a prime/boost approach. This study evaluated neutralizing antibody (NAb) induction of a dengue tetravalent DNA (TDNA) vaccine candidate administered by intramuscular-electroporation (IM-EP) and the benefit of homologous TDNA boosting in mice. Consensus humanized pre-membrane (prM) and envelope (E) of each serotypes, based on isolates from year 1962–2003, were separately cloned into a pCMVkan expression vector. ICR mice, five-six per group were immunized for three times (2-week interval) with TDNA at 100 µg (group I; 25 µg/monovalent) or 10 µg (group II; 2.5 µg/monovalent). In group I, mice received an addtional TDNA boosting 13 weeks later. Plaque reduction neutralization tests (PRNT) were performed at 4 weeks post-last immunization. Both 100 µg and 10 µg doses of TDNA induced high NAb levels against all DENV serotypes. The median PRNT50 titers were comparable among four serotypes of DENV after TDNA immunization. Median PRNT50 titers ranged 240–320 in 100 µg and 160–240 in 10 µg groups (p = ns). A time course study of the 100 µg dose of TDNA showed detectable NAb at 2 weeks after the second injection. The NAb peaked at 4 weeks after the third injection then declined over time but remained detectable up to 13 weeks. An additional homologous TDNA boosting significantly enhanced the level of NAb from the nadir for at least ten-fold (p<0.05). Of interest, we have found that the use of more recent dengue viral strain for both vaccine immunogen design and neutralization assays is critical to avoid a mismatching outcome. In summary, this TDNA vaccine candidate induced good neutralizing antibody responses in mice; and the DNA/DNA prime/boost strategy is promising and warranted further evaluation in non-human primates.

Potent adjuvant effects of novel NKT stimulatory glycolipids on hemagglutinin based DNA vaccine for H5N1 influenza virus

H5N1 influenza virus is a highly pathogenic virus, posing a pandemic threat. Previously, we showed that phenyl analogs of α-galactosylceramide (α-GalCer) displayed greater NKT stimulation than α-GalCer. Here, we examined the adjuvant effects of one of the most potent analogs, C34, on consensus hemagglutinin based DNA vaccine (pCHA5) for H5N1 virus. Upon intramuscular electroporation of mice with pCHA5 with/without various α-GalCer analogs, C34-adjuvanted group developed the highest titer against consensus H5 and more HA-specific IFN-γ secreting CD8 cells (203±13.5) than pCHA5 alone (152.6±13.7, p<0.05). Upon lethal challenge of NIBRG-14 virus, C34-adjuvanted group (84.6%) displayed higher survival rate than pCHA5 only group (46.1%). In the presence of C34 as adjuvant, the antisera displayed broader and greater neutralizing activities against virions pseudotyped with HA of clade 1, and 2.2 than pCHA5 only group. Moreover, to simulate an emergency response to a sudden H5N1 outbreak, we injected mice intramuscularly with single dose of a new consensus H5 (pCHA5-II) based on 1192 full-length H5 sequences, with C34 as adjuvant. The latter not only enhanced the humoral immune response and protection against virus challenge, but also broadened the spectrum of neutralization against pseudotyped HA viruses. Our vaccine strategy can be easily implemented for any H5N1 virus outbreak by single IM injection of a consensus H5 DNA vaccine based on updated HA sequences using C34 as an adjuvant.