Combined DNA Vaccine Research Articles

Evaluation of combination vaccines targeting transmission of Plasmodium falciparum and P. vivax

Transmission-blocking vaccines interrupting malaria transmission within mosquitoes represent an ideal public health tool to eliminate malaria at the population level. Plasmodium falciparum and P. vivax account for more than 90% of the global malaria burden, co-endemic in many regions of the world. P25 and P48/45 are two leading candidates for both species and have shown promising transmission-blocking activity in preclinical and clinical studies. However, neither of these target antigens as individual vaccines has induced complete transmission inhibition in mosquitoes. In this study, we assessed immunogenicity of combination vaccines based on P25 and P48/45 using a DNA vaccine platform to broaden vaccine specificity against P. falciparum and P. vivax. Individual DNA vaccines encoding Pvs25, Pfs25, Pvs48/45 and Pfs48/45, as well as various combinations including (Pvs25 + Pvs48/45), (Pfs25 + Pfs48/45), (Pvs25 + Pfs25), and (Pvs48/45 + Pfs48/45), were evaluated in mice using in vivo electroporation. Potent antibody responses were induced in mice immunized with individual and combination DNA vaccines, and specific antibody responses were not compromised when combinations of DNA vaccines were evaluated against individual DNA vaccines. The anti-Pvs25 IgG from individual and combination groups revealed concentration-dependent transmission-reducing activity (TRA) in direct membrane feeding assays (DMFA) using blood from P. vivax-infected donors in Brazil and independently in ex vivo MFA using Pvs25-transgenic P. berghei. Similarly, anti-Pfs25 and anti-Pfs48/45 IgGs from mice immunized with Pfs25 and Pfs48/45 DNA vaccines individually and in various combinations revealed antibody dose-dependent TRA in standard membrane feeding assays (SMFA) using culture-derived P. falciparum gametocytes. However, antibodies induced by immunization with Pvs48/45 DNA vaccines were ineffective in DMFA and require further vaccine construct optimization, considering the possibility of induction of both transmission-blocking and transmission-enhancing antibodies revealed by competition ELISA. These studies provide a rationale for combining multiple antigens to simultaneously target transmission of malaria caused by P. falciparum and P. vivax.

Co-immunization with DNA vaccines encoding yidR and IL-17 augments host immune response against Klebsiella pneumoniae infection in mouse model

ABSTRACT Klebsiella pneumoniae is an important gram-negative bacterium that causes severe respiratory and healthcare-associated infections. Although antibiotic therapy is applied to treat severe infections caused by K. pneumoniae, drug-resistant isolates pose a huge challenge to clinical practices owing to adverse reactions and the mismanagement of antibiotics. Several studies have attempted to develop vaccines against K. pneumoniae, but there are no licensed vaccines available for the control of K. pneumoniae infection. In the current study, we constructed a novel DNA vaccine, pVAX1-YidR, which encodes a highly conserved virulence factor YidR and a recombinant expression plasmid pVAX1-IL-17 encoding Interleukin-17 (IL-17) as a molecular adjuvant. Adaptive immune responses were assessed in immunized mice to compare the immunogenicity of the different vaccine schemes. The results showed that the targeted antigen gene was expressed in HEK293T cells using an immunofluorescence assay. Mice immunized with pVAX1-YidR elicited a high level of antibodies, induced strong cellular immune responses, and protected mice from K. pneumoniae challenge. Notably, co-immunization with pVAX1-YidR and pVAX1-IL-17 significantly augmented host adaptive immune responses and provided better protection against K. pneumoniae infections in vaccinated mice. Our study demonstrates that combined DNA vaccines and molecular adjuvants is a promising strategy to develop efficacious antibacterial vaccines against K. pneumoniae infections.

Vaccination with immune complexes modulates the elicitation of functional antibodies against HIV-1.

Neutralizing antibodies (Abs) are one of the immune components required to protect against viral infections. However, developing vaccines capable of eliciting neutralizing Abs effective against a broad array of HIV-1 isolates has been an arduous challenge. This study sought to test vaccines aimed to induce Abs against neutralizing epitopes at the V1V2 apex of HIV-1 envelope (Env). Four groups of rabbits received a DNA vaccine expressing the V1V2 domain of the CRF01_AE A244 strain on a trimeric 2J9C scaffold (V1V2-2J9C) along with a protein vaccine consisting of an uncleaved prefusion-optimized A244 Env trimer with V3 truncation (UFO-BG.ΔV3) or a V1V2-2J9C protein and their respective immune complexes (ICs). These IC vaccines were made using 2158, a V1V2-specific monoclonal Ab (mAb), which binds the V2i epitope in the underbelly region of V1V2 while allosterically promoting the binding of broadly neutralizing mAb PG9 to its V2 apex epitope in vitro. Rabbit groups immunized with the DNA vaccine and uncomplexed or complexed UFO-BG.ΔV3 proteins (DNA/UFO-UC or IC) displayed similar profiles of Env- and V1V2-binding Abs but differed from the rabbits receiving the DNA vaccine and uncomplexed or complexed V1V2-2J9C proteins (DNA/V1V2-UC or IC), which generated more cross-reactive V1V2 Abs without detectable binding to gp120 or gp140 Env. Notably, the DNA/UFO-UC vaccine elicited neutralizing Abs against some heterologous tier 1 and tier 2 viruses from different clades, albeit at low titers and only in a fraction of animals, whereas the DNA/V1V2-UC or IC vaccines did not. In comparison with the DNA/UFO-UC group, the DNA/UFO-IC group showed a trend of higher neutralization against TH023.6 and a greater potency of V1V2-specific Ab-dependent cellular phagocytosis (ADCP) but failed to neutralize heterologous viruses. These data demonstrate the capacity of V1V2-2J9C-encoding DNA vaccine in combination with UFO-BG.ΔV3, but not V1V2-2J9C, protein vaccines, to elicit homologous and heterologous neutralizing activities in rabbits. The elicitation of neutralizing and ADCP activities was modulated by delivery of UFO-BG.ΔV3 complexed with V2i mAb 2158.

Research Progress on the Development of Porcine Reproductive and Respiratory Syndrome Vaccines.

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious disease in the pig industry, but its pathogenesis is not yet fully understood. The disease is caused by the PRRS virus (PRRSV), which primarily infects porcine alveolar macrophages and disrupts the immune system. Unfortunately, there is no specific drug to cure PRRS, so vaccination is crucial for controlling the disease. There are various types of single and combined vaccines available, including live, inactivated, subunit, DNA, and vector vaccines. Among them, live vaccines provide better protection, but cross-protection is weak. Inactivated vaccines are safe but have poor immune efficacy. Subunit vaccines can be used in the third trimester of pregnancy, and DNA vaccines can enhance the protective effect of live vaccines. However, vector vaccines only confer partial protection and have not been widely used in practice. A PRRS vaccine that meets new-generation international standards is still needed. This manuscript provides a comprehensive review of the advantages, disadvantages, and applicability of live-attenuated, inactivated, subunit, live vector, DNA, gene-deletion, synthetic peptide, virus-like particle, and other types of vaccines for the prevention and control of PRRS. The aim is to provide a theoretical basis for vaccine research and development.

Co-Immunization with DNA Vaccines Expressing SABP1 and SAG1 Proteins Effectively Enhanced Mice Resistance to Toxoplasma gondii Acute Infection.

Toxoplasma gondii (T. gondii) has many intermediate hosts, obligately invades nucleated cells, and seriously threatens human and animal health due to a lack of effective drugs and vaccines. Sialic acid-binding protein 1 (SABP1) is a novel invasion-related protein that, like surface antigen 1 (SAG1), is found on the plasma membrane of T. gondii. To investigate the immunogenicity and protective efficacy of DNA vaccines expressing SABP1 and SAG1 proteins against T. gondii acute infection, the recombinant plasmids pVAX1-SABP1 and pVAX1-SAG1 were produced and administered intramuscularly in Balb/c mice. Serum antibody levels and subtypes, lymphocyte proliferation, and cytokines were used to assess immunized mice's humoral and cellular immune responses. Furthermore, the ability of DNA vaccines to protect mice against T. gondii RH tachyzoites was tested. Immunized mice exhibited substantially higher IgG levels, with IgG2a titers higher than IgG1. When the immune group mice's splenocytes were stimulated with T. gondii lysate antigen, Th1-type cytokines (IL-12p70, IFN-γ, and IL-2) and Th2-type cytokine (IL-4) increased significantly. The combined DNA vaccine significantly increased the immunized mouse survival compared to the control group, with an average death time extended by 4.33 ± 0.6 days (p < 0.0001). These findings show that DNA vaccines based on the SABP1 and SAG1 genes induced robust humoral and cellular immunity in mice, effectively protecting against acute toxoplasmosis and potentially serving as a viable option for vaccination to prevent T. gondii infection.

Immune responses and protective efficacy of a trivalent combination DNA vaccine based on oprL, oprF and flgE genes of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an infectious pathogenic bacteria infecting many different species of animals. Currently, it lacks a commercial vaccine. In this study, three monovalent DNA vaccines (poprL, poprF, and pflgE), three bivalent combination DNA vaccines (poprL+poprF, poprL+pflgE, poprF+pflgE), and a trivalent DNA vaccine (poprL+poprF+pflgE) were constructed. Consequently, we immunised chickens with these DNA vaccines and used inactivated vaccines as the positive controls. Then, the immune efficacy was evaluated through serum antibody detection, a lymphocyte proliferation assay, and cytokine concentration determination. Lastly, we assessed the protection rate through a challenge experiment. Following vaccination, the serum antibody levels induced using these DNA vaccines were different due to the different coating antigens. In the trivalent combination DNA vaccine group, we established that the lymphocyte proliferation (SI values), IFN-γ, IL-2, and IL-4 levels were significantly higher than those of the other six DNA vaccine groups and the inactivated vaccine group. However, the protection provided was slightly lower than that of the inactivated vaccine and higher than those of other DNA vaccines. The protection rate of poprL, poprF, pflgE, poprL+poprF, poprL+pflgE, poprF+pflgE, poprL+poprF+pflgE, and the inactivated vaccine were 50, 45, 60, 75, 80, 80, 90, and 95%, respectively. The results of this study indicated the trivalent DNA vaccine based on oprL, oprF and flgE genes represents a promising approach for the prevention of Pseudomonas aeruginosa infections.

Immunotherapy against the Cystine/Glutamate Antiporter xCT Improves the Efficacy of APR-246 in Preclinical Breast Cancer Models.

Breast cancer is the most frequent cancer in women. Despite recent clinical advances, new therapeutic approaches are still required. The cystine-glutamate antiporter xCT, encoded by the SLC7A11 gene, which imports cystine in exchange with glutamate, is a potentially new target for breast cancer therapy, being involved in tumor cell redox balance and resistance to therapies. xCT expression is regulated by the oncosuppressor p53, which is mutated in many breast cancers. Indeed, mutant p53 (mut-p53) can induce xCT post-transcriptional down modulation, rendering mut-p53 tumors susceptible to oxidative damage. Interestingly, the drug APR-246, developed to restore the wild-type function of p53 in tumors harboring its mutation, alters the cell redox balance in a p53-independent way, possibly rendering the cells more sensitive to xCT inhibition. Here, we propose a combinatorial treatment based on xCT immunetargeting and APR-246 treatment as a strategy for tackling breast cancer. We demonstrate that combining the inhibition of xCT with the APR-246 drug significantly decreased breast cancer cell viability in vitro and induced apoptosis and affected cancer stem cells' self-renewal compared to the single treatments. Moreover, the immunetargeting of xCT through DNA vaccination in combination with APR-246 treatment synergistically hinders tumor progression and prevents lung metastasis formation in vivo. These effects can be mediated by the production of anti-xCT antibodies that are able to induce the antibody dependent cellular cytotoxicity of tumor cells. Overall, we demonstrate that DNA vaccination against xCT can synergize with APR-246 treatment and enhance its therapeutic effect. Thus, APR-246 treatment in combination with xCT immunetargeting may open new perspectives in the management of breast cancer.

CAFs/tumor cells co-targeting DNA vaccine in combination with low-dose gemcitabine for the treatment of Panc02 murine pancreatic cancer

In this study, we investigate the synergistic effect of gemcitabine (Gem) and a novel DNA vaccine in the treatment of pancreatic cancer in mice and explore the anti-tumor mechanism of this combination therapy. Fibroblast activation protein α-expressing cancer-associated fibroblasts (FAPα+ CAFs), a dominant component of the tumor microenvironment (TME), have been shown to modulate the extracellular matrix (ECM) to promote the growth, invasion, and metastasis of pancreatic cancer (PC). Therefore, FAPα+ CAFs may be an ideal target for the treatment of PC. However, treatments that solely target FAPα+ CAFs do not directly affect tumor cells. We recently constructed a novel chimeric DNA vaccine (OsFS) against human FAPα and survivin, which simultaneously targets FAPα+ CAFs and tumor cells. In Panc02 tumor-bearing mice, OsFS vaccination not only reduced the proportion of immunosuppressive cells but also promoted the recruitment of tumor-infiltrating lymphocytes, which remodeled the TME to support anti-tumor immune responses. Furthermore, after depletion of regulatory T cells (Tregs) by metronomic low-dose Gem therapy, the anti-tumor effects of OsFS were enhanced. Taken together, our results indicate that the combination of the FAPα/survivin co-targeting DNA vaccine and low-dose Gem may be an effective therapy for PC.

A pilot trial of neoantigen DNA vaccine in combination with nivolumab/ipilimumab and prostvac in metastatic hormone-sensitive prostate cancer (mHSPC).

5068 Background: Treatment with immune checkpoint blockade (ICB) alone results in suboptimal response rates in prostate cancer. Prostvac-VF Tricom is a therapeutic vaccine that incorporates DNA for the shared self-antigen PSA. Personalized neoantigen vaccines based on specific mutated epitopes may have the ability to overcome immunoresistance seen with self-antigens. Even in low mutational burden tumors like prostate cancer, T cell responses against neoantigens have been correlated with favorable clinical outcomes. Thus, we hypothesized that the combination of shared antigen and neoantigen vaccines with dual ICB will induce robust immune responses and improve clinical outcomes. Methods: This Phase I clinical trial (NCT03532217) enrolled patients from 2018-2021. Eligible patients had histologically confirmed high risk mHSPC, must have completed a course of docetaxel and received continuous androgen deprivation therapy. Patients were treated with Prostvac-VF in combination with ipilimumab/nivolumab within 60 days of the last docetaxel dose. Then, patients were continued on monthly nivolumab with their personalized neoantigen vaccine administered via intramuscular electroporation. The primary objectives of this study were to assess the feasibility, safety/tolerability, and immune responses of this combination strategy. Key secondary objectives include failure free survival, milestone overall survival (OS), PSA responses, and radiographic progression free survival. Results: Nineteen patients were enrolled and treated on trial, and feasibility was shown with 15 (79%) receiving neoantigen vaccines. Four patients did not receive neoantigen vaccines (2 for progressive disease, 2 for ICB toxicity). Treatment was well-tolerated with only 2 (2.4%) grade 3 treatment related adverse events (TRAEs) of colitis, and no grade 4+ TRAEs. The common grade 1-2 TRAEs were diarrhea (10%), injection site reactions (10%), rash (7.4%), and fatigue (6%). Median follow-up to date is 22.6 (11.3-39.6) months, with median OS not yet reached and 2 year milestone OS of 75%. Six (31.5%) patients had PSA progression per PCWG2 criteria while on treatment, with the median time to PSA progression not yet reached for the total population. Increases in activation/co-stimulatory/co-inhibitory seen after treatment with Prostvac/ICB, suggest immune priming. Sample collection is complete and immune correlative analyses are ongoing. Final safety/tolerability and preliminary correlative and clinical outcomes will be reported. Conclusions: This is the first clinical trial evaluating the use of personalized neoantigen vaccines in a combination immunotherapeutic approach in mHSPC patients. Clinical trial information: NCT03532217.

Combination of DNA Vaccine and Immune Checkpoint Blockades Improves the Immune Response in an Orthotopic Unresectable Glioblastoma Model.

Combination immunotherapy has emerged as a promising strategy to increase the immune response in glioblastoma (GBM) and overcome the complex immunosuppression occurring in its microenvironment. In this study, we hypothesized that combining DNA vaccines—to stimulate a specific immune response—and dual immune checkpoint blockade (ICB)—to decrease the immunosuppression exerted on T cells—will improve the immune response and the survival in an orthotopic unresectable GL261 model. We first highlighted the influence of the insertion position of a GBM epitope sequence in a plasmid DNA vaccine encoding a vesicular stomatitis virus glycoprotein (VSV-G) (here referred to as pTOP) in the generation of a specific and significant IFN-γ response against the GBM antigen TRP2 by inserting a CD8 epitope sequence in specific permissive sites. Then, we combined the pTOP vaccine with anti-PD-1 and anti-CTLA-4 ICBs. Immune cell analysis revealed an increase in effector T cell to Treg ratios in the spleens and an increase in infiltrated IFN-γ-secreting CD8 T cell frequency in the brains following combination therapy. Even if the survival was not significantly different between dual ICB and combination therapy, we offer a new immunotherapeutic perspective by improving the immune landscape in an orthotopic unresectable GBM model.

A Novel Combined DNA Vaccine Encoding Toxoplasma gondii SAG1 and ROP18 Provokes Protective Immunity Against a Lethal Challenge in Mice.

Antigens expressed by Toxoplasma gondii (T. gondii) during its life cycle trigger various immune responses in the host. Recently, toxoplasma vaccine research focused on T. gondii surface antigen 1 (SAG1) and Rhoptry Protein 18 (ROP18) to establish a safe and efficacious DNA vaccine. We constructed two eukaryotic expression plasmids: p3 × FLAG-Myc-CMV™-24-SAG1 and p3 × FLAG-Myc-CMV™-24-ROP18. BALB/c mice were randomly divided into six groups and immunized with these DNA vaccines either separately or in combination. The combination vaccine was administered at either the full dose or at half-strength dose. Control mice were immunized with empty vector or with phosphate-buffered saline. The frequency of CD4+ cells in the spleen was consistent among all groups, whereas that of CD8+ T cells was the highest in the group immunized with the combination vaccine at half-strength dose (p < 0.05). Importantly, the mRNA expression levels of interleukin-12 (IL-12) and interferon-gamma (INF-γ) were closely correlated (r = 0.6, p < 0.0001) and both were upregulated in the group that was immunized with the combination vaccine at half-strength dose (p < 0.0001). The survival time of the mice subjected to a lethal dose of toxoplasma was significantly extended by prior immunization with DNA vaccines expressing either SAG1 or ROP18 or a combination of both (p < 0.05). The group that was immunized with the combination vaccine at half-strength dose demonstrated the best efficacy (p < 0.05). These results showed that the combination DNA vaccine provided better immune protection than the single gene vaccines, and that optimizing the dosing of the vaccine can improve the immune response.

A pilot trial of neoantigen DNA vaccine in combination with nivolumab/ipilimumab and prostvac in metastatic hormone-sensitive prostate cancer (mHSPC).

TPS192 Background: Despite robust advances in the use of immune checkpoint blockade (ICB) across multiple cancer types, responses in prostate cancer remain suboptimal. Overall response rates for single-agent ICB in prostate cancer are low, but recent modest gains have been made with ipilimumab and nivolumab combination therapy in metastatic castrate-resistant prostate cancer. Prostvac-VF Tricom is a therapeutic vaccine that incorporates DNA for the shared self-antigen PSA into the vaccinia (or fowlpox) virus strain. A large randomized phase III clinical trial recently showed no improvement in overall survival (OS) with Prostvac compared with placebo, suggesting that a combinatorial approach is warranted. Personalized neoantigen vaccines based on specific mutated epitopes may have the ability to overcome immunoresistance seen with self antigens. Even in low mutational burden tumors like prostate cancer, T cell responses against neoantigens are observed in patients with favorable clinical outcomes, supporting neoantigen vaccination as a promising therapeutic strategy. Improvements in computational genomics and predictive algorithms have allowed the incorporation of MHC class II neoepitopes and those from gene fusion events relevant in prostate cancer. We thus hypothesized that a strategy utilizing both shared antigen (Prostvac) and personalized MHC-I and MHC-II neoantigen vaccines combined with dual ICB would induce robust immune responses and improve clinical outcomes. To maximize tumor burden reduction and minimize tumor-mediated immunoresistence, we are evaluating this novel strategy in patients with metastatic hormone-sensitive prostate cancer (mHSPC) who have completed frontline docetaxel chemotherapy. Methods: This ongoing trial (NCT03532217) began accrual in September 2018. Eighteen of 20 planned patients have been enrolled to date. Eligible patients have histologically confirmed high risk/volume mHSPC defined as 4 or more sites of metastatic disease or visceral involvement. Patients receive continuous androgen deprivation therapy (ADT) and have completed upfront docetaxel chemotherapy. Patients begin treatment with Prostvac-VF in combination with ipilimumab (1 mg/kg every 3 weeks for 2 doses), and nivolumab (3 mg/kg every 3 weeks for 6 doses) within 60 days of the last dose of docetaxel. Subsequently, patients receive nivolumab 480 mg IV every 4 weeks in conjunction with a personalized neoantigen DNA vaccine administered monthly via intramuscular electroporation. The primary objective of this exploratory study is to assess the feasibility, safety/tolerability, and immune responses of this combination strategy. Key secondary objectives include failure-free survival and milestone survival at 2 years, PSA response, and radiographic progression-free survival. Clinical trial information: NCT03532217.

Immune Efficacy of different immunization doses of divalent combination DNA vaccine pOPRL+pOPRF of Pseudomonas aeruginosa.

At present, there is no vaccine available against Pseudomonas aeruginosa, a common zoonotic pathogenic bacterium. In a previous study, the authors prepared a divalent combination DNA vaccine, pOPRL+pOPRF, which exhibited good protective efficacy. To explore the optimal immunization dose of this divalent combination DNA vaccine, in the present study, chickens were vaccinated with 25, 50, 100, and 200 µg doses. The levels of serum antibody, interferon-γ (IFN-γ), and interleukin-2 (IL-2) were determined, and lymphocyte proliferation assays were performed. After challenge with virulent P. aeruginosa, the protective efficacy was evaluated. Following vaccination, the serum antibodies, stimulation index values, and concentrations of IFN-γ and IL-2 were significantly higher in chickens vaccinated with 100 and 200 µg vaccines than in those vaccinated with 25 and 50 µg doses (P<0.05). IFN-γ and IL-2 concentrations in chickens immunized with 100 µg vaccine were slightly higher than those in chickens immunized with 200 µg vaccine, although the difference was not statistically significant. The protective rates were 55%, 65%, 85%, and 85% with 25, 50, 100, and 200 µg of the pOPRL+pOPRF DNA vaccine, respectively. Thus, the immune efficacy of the pOPRL+pOPRF DNA vaccine increased with an increase in immunization dose, but this does not imply that a higher dose necessarily achieves a better outcome. The optimal immunization dose of pOPRL+pOPRF DNA vaccine in chickens was 100 µg.

Abstract 1466: Combination immunotherapy successfully control tumor growth in a transgenic mouse model

Abstract The use of checkpoint inhibitor anti-PD1 has achieved significant clinical benefit, in recurrent and metastatic head and neck cancer patients, where the overall response rate is between 16-20%. The use of antigen-specific cancer vaccine to increase the level of cytotoxic T cells is believed to work synergistically with anti-PD1. In this study, we evaluated the efficacy of antigen-specific DNA vaccine when it’s used in combination with anti-PD1. The B6.Cg-Tg(HLA-A/H2-D)2Enge/J mice bearing established tumours overexpressing the tumour antigen were vaccinated either with anti-PD1, DNA vaccine or anti-PD1 in combination with DNA vaccine. Tumour volume was monitored and antigen-specific immune responses were evaluated at the endpoint. Our data demonstrated DNA vaccine induced antigen-specific immune responses and animals vaccinated with DNA vaccine harboured smaller tumour volume compared to controls. Significantly, animals that received DNA vaccine expressed consistently higher levels IFN-γ and resulted in the upregulation of PD1 compared to control animals. We then demonstrated mice vaccinated with both DNA vaccine and anti-PD1 had near to complete tumour control, indicating a synergistic effect of DNA vaccine with anti-PD1. Animals treated with DNA vaccine in combination with anti-PD1 also have better overall survival. Importantly, these animals showed increased antigen-specific responses by the ELISPOT assay. In summary, our data suggest antigen-specific DNA vaccine works synergistically with anti-PD1 and conferred an excellent tumour control; this opens up a new opportunity of combinatory immunotherapy that might benefit a wider population of patients in an antigen-specific manner. Citation Format: Kue Peng Lim, Syafinaz Zainal, Natasha Zulaziz, Chai Phei Gan, San Jiun Chai, Bryan Kit Weng Lye, Chuan Wang, Ruhcha V. Sutavani, Christian Ottensmeier, Emma King, Gareth Thomas, Natalia Savelyeva, Sok Ching Cheong. Combination immunotherapy successfully control tumor growth in a transgenic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1466.

Intradermal DNA vaccination combined with dual CTLA-4 and PD-1 blockade provides robust tumor immunity in murine melanoma.

We aimed to explore whether the combination of intradermal DNA vaccination, to boost immune response against melanoma antigens, and immune checkpoint blockade, to alleviate immunosuppression, improves antitumor effectiveness in a murine B16F10 melanoma tumor model. Compared to single treatments, a combination of intradermal DNA vaccination (ovalbumin or gp100 plasmid adjuvanted with IL12 plasmid) and immune checkpoint CTLA-4/PD-1 blockade resulted in a significant delay in tumor growth and prolonged survival of treated mice. Strong activation of the immune response induced by combined treatment resulted in a significant antigen-specific immune response, with elevated production of antigen-specific IgG antibodies and increased intratumoral CD8+ infiltration. These results indicate a potential application of the combined DNA vaccination and immune checkpoint blockade, specifically, to enhance the efficacy of DNA vaccines and to overcome the resistance to immune checkpoint inhibitors in certain cancer types.

Immune efficacy of single, bivalent fusion and combined DNA vaccines based on oprL and oprF genes of Pseudomonas aeruginosa

Immune efficacy of single, bivalent fusion and combined DNA vaccines based on oprL and oprF genes of Pseudomonas aeruginosa

Immune efficacy of DNA vaccines based on oprL and oprF genes of Pseudomonas aeruginosa in chickens

Pseudomonas aeruginosa (P. aeruginosa) is a zoonotic pathogen that can infect a variety of animals, including poultry. However, as there is no commercial vaccine available it is imperative that new and effective vaccines are developed. In this study, 2 monovalent DNA vaccines (pOPRL and pOPRF), one divalent combination DNA vaccine (pOPRL+pOPRF) and one fusion DNA vaccine (pOPRLF) were constructed based on the oprL and oprF genes of P. aeruginosa. These vaccines were administered to chickens, an outer membrane protein vaccine (OMP vaccine) and inactivated vaccine used as positive controls. The serum antibody, interferon-γ (IFN-γ), interleukin-2 (IL-2) and interleukin-4 (IL-4) concentrations were determined and lymphocyte proliferation assays were performed. After challenging with virulent P. aeruginosa, protective efficacy was evaluated. Following vaccination, serum antibodies, stimulation index (SI) values, concentrations of IL-2 and IFN-γ in chickens vaccinated with the bivalent combination DNA vaccine and fusion DNA vaccine were found to be significantly higher than in those chickens vaccinated with the 2 monovalent DNA vaccines. Moreover, the immune indexes in the bivalent combination DNA vaccine group were higher than those in the fusion DNA vaccine group. However, the concentrations of IL-4 in the 4 DNA vaccine groups were of no significant difference. The protective efficacy rate provided by pOPRL, pOPRF, pOPRLF, pOPRL+pOPRF, inactivated vaccine and OMP vaccine were 53.3%, 40%, 66.7%, 80%, 93.3%, and 80%, respectively. The results indicate that DNA vaccines constructed with the oprL and oprF genes of P. aeruginosa, particularly the divalent combination DNA vaccine, represent better potential vaccines. This study has laid a foundation for the design and application of future DNA vaccines of P. aeruginosa.

Immunogenicity and Therapeutic Effects of pVAX1-rv1419 DNA from Mycobacterium tuberculosis

Background The situation of tuberculosis (TB) is very severe in China. New therapeutic agents and regimens to treat TB are urgently needed. Objective In this study, a DNA vaccine expressing Mycobacterium tuberculosis (MTB) Rv1419 antigen was constructed and its immunogenicity and therapeutic effects were evaluated. Method Normal mice and TB model mice were immunized intramuscularly three times at two-week intervals with saline, plasmid vector pVAX1, M. vaccae vaccine, pVAX1- ag85a (rv3804c) DNA or pVAX1-rv1419 DNA, respectively. Results At three weeks after the last immunization, flow cytometry showed a higher proportion of CD4+ T cells expressing IFN-y (Th1) in response to Rv1419 protein in blood from the pVAX1- rv1419 DNA group compared with the saline and vector groups (P<0.05), suggesting a predominant Th1 immune response. Live bacterial loads in lungs and spleens were lower by 0.41 log10 in the pVAX1- rv1419 DNA group than in the saline controls. In addition, pathological changes in the lungs of the DNA vaccinated groups were less. These results suggest that pVAX1- rv1419 DNA could be effective for the treatment of TB, significantly increasing the Th1-type cellular immune response, and inhibiting the growth of MTB. Conclusion Therefore pVAX1- rv1419 DNA is a candidate for inclusion in a therapeutic combination DNA vaccine against TB.

Synergistic effect of programmed cell death protein1 blockade and secondary lymphoid tissue chemokine in the induction of anti-tumor immunity by a therapeutic cancer vaccine.

The use of DNA vaccineshas become anattractive approachfor generating antigen-specificcytotoxic CD8+ T lymphocytes (CTLs), which can mediate protective antitumor immunity. The potency of DNA vaccines encoding weakly immunogenic tumor-associated antigens (TAAs) can be improved by using an adjuvant injected together with checkpoint antibodies. In the current study, we evaluated whether the therapeutic effects of a DNA vaccine encoding human papillomavirus type 16 (HPV-16) E7 can be enhanced by combined application of an immune checkpoint blockadedirected against the programmed death-1 (PD-1) pathway and secondary lymphoid tissue chemokine (SLC) also known as CCL21 adjuvant, in a mouse cervical cancer model. The therapeutic effects of the DNA vaccine in combination with CCL21 adjuvant plus PD-1 blockade was evaluated using a tumor growth curve. To further investigate the mechanism underlying the antitumor response, cytolytic and lymphocyte proliferation responses in splenocytes were measured using non-radioactive cytotoxicity and MTT assays, respectively. Vascular endothelial growth factor (VEGF) and IL-10 expression in the tumor and the levels of IFN-γ and IL-4 in supernatants of spleno-lymphocyte cultures were measured using ELISA. The immune efficacy was evaluated by in vivotumor regression assay. The results showed that vaccination with a DNA vaccine in combination with the CCL21 adjuvant plus PD-1 blockade greatly enhanced cytotoxic T lymphocyte production and lymphocyte proliferation rates and greatly inhibited tumor progression. Moreover, the vaccine in combination with adjuvant and blockade significantly reduced intratumoral VEGF, IL-10 and splenic IL-4 but induced the expression of splenic IFN-γ. This formulation could be an effective candidate for a vaccine against cervical cancers and merits further investigation.

DNA vaccination based on pyolysin co-immunized with IL-1β enhances host antibacterial immunity against Trueperella pyogenes infection

Trueperella pyogenes is a commensal and opportunistic pathogen normally causes mastitis, liver abscesses and pneumonia of economically important livestock. To date, no specific control measure was reported to prevent T. pyogenes infections. In this study, we first constructed a recombinant plasmid pVAX1-PLO based on the main virulent factor pyolysin gene as DNA vaccine against T. pyogenes infection. Subsequently, transient expression of pVAX1-PLO and pcDNA3.1/V5-fIL-1β were identified in Human embryonic kidney cells (HEK293T) by immunofluorescence assay. Humoral and cellular immune responses were evaluated in mice to compare the immunogenicity between different immunized groups. The results showed that the successful expression of PLO or fIL-1β protein was detected by confocal microscopy for cells transfected with plasmid pVAX1-PLO and/or pcDNA3.1/V5-fIL-1β. The mice immunized with pVAX1-PLO elicited a higher titer of PLO-specific antibody than the control group. The levels of IFN-γ and IL-2 were significantly increased in the pVAX1-PLO immunized mice, while the expression level of IL-4 was slightly increased but not significant. These findings suggested that the DNA vaccine pVAX1-PLO can primarily induce Th1 immune response. The residual Colony-Forming Units (CFUs) from the liver and peritoneal fluid were decreased obviously in the pVAX1-PLO treated mice compared with the control. Importantly, co-immunization with pcDNA3.1/V5-fIL-1β and pVAX1-PLO could enhance host humoral and cellular immune responses and significantly protect mouse from T. pyogenes infection. In conclusion, our study provides a promising strategy against T. pyogenes infections and implies the potential clinical application of combined DNA vaccines in diseases control.