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Abbasi S, Uchida S. Multifunctional Immunoadjuvants for Use in Minimalist Nucleic Acid Vaccines. Pharmaceutics 2021; 13:644. [PMID: 34062771 PMCID: PMC8147386 DOI: 10.3390/pharmaceutics13050644] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/25/2021] [Accepted: 04/27/2021] [Indexed: 12/13/2022] Open
Abstract
Subunit vaccines based on antigen-encoding nucleic acids have shown great promise for antigen-specific immunization against cancer and infectious diseases. Vaccines require immunostimulatory adjuvants to activate the innate immune system and trigger specific adaptive immune responses. However, the incorporation of immunoadjuvants into nonviral nucleic acid delivery systems often results in fairly complex structures that are difficult to mass-produce and characterize. In recent years, minimalist approaches have emerged to reduce the number of components used in vaccines. In these approaches, delivery materials, such as lipids and polymers, and/or pDNA/mRNA are designed to simultaneously possess several functionalities of immunostimulatory adjuvants. Such multifunctional immunoadjuvants encode antigens, encapsulate nucleic acids, and control their pharmacokinetic or cellular fate. Herein, we review a diverse class of multifunctional immunoadjuvants in nucleic acid subunit vaccines and provide a detailed description of their mechanisms of adjuvanticity and induction of specific immune responses.
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Affiliation(s)
- Saed Abbasi
- Innovation Center of NanoMedicine, Kawasaki Institute of Industrial Promotion, 3-25-14 Tonomachi, Kawasaki-ku, Kawasaki 210-0821, Japan
| | - Satoshi Uchida
- Innovation Center of NanoMedicine, Kawasaki Institute of Industrial Promotion, 3-25-14 Tonomachi, Kawasaki-ku, Kawasaki 210-0821, Japan
- Medical Chemistry, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 1-5 Shimogamohangi-cho, Sakyo-ku, Kyoto 606-0823, Japan
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Zahm CD, Colluru VT, McIlwain SJ, Ong IM, McNeel DG. TLR Stimulation during T-cell Activation Lowers PD-1 Expression on CD8 + T Cells. Cancer Immunol Res 2018; 6:1364-1374. [PMID: 30201735 PMCID: PMC6215515 DOI: 10.1158/2326-6066.cir-18-0243] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 06/20/2018] [Accepted: 08/30/2018] [Indexed: 02/06/2023]
Abstract
Expression of T-cell checkpoint receptors can compromise antitumor immunity. Blockade of these receptors, notably PD-1 and LAG-3, which become expressed during T-cell activation with vaccination, can improve antitumor immunity. We evaluated whether T-cell checkpoint expression could be separated from T-cell activation in the context of innate immune stimulation with TLR agonists. We found that ligands for TLR1/2, TLR7, and TLR9 led to a decrease in expression of PD-1 on antigen-activated CD8+ T cells. These effects were mediated by IL12 released by professional antigen-presenting cells. In two separate tumor models, treatment with antitumor vaccines combined with TLR1/2 or TLR7 ligands induced antigen-specific CD8+ T cells with lower PD-1 expression and improved antitumor immunity. These findings highlight the role of innate immune activation during effector T-cell development and suggest that at least one mechanism by which specific TLR agonists can be strategically used as vaccine adjuvants is by modulating the expression of PD-1 during CD8+ T-cell activation. Cancer Immunol Res; 6(11); 1364-74. ©2018 AACR.
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Affiliation(s)
- Christopher D Zahm
- University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, Wisconsin
| | - Viswa T Colluru
- University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, Wisconsin
| | - Sean J McIlwain
- University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, Wisconsin
- Department of Biostatistics and Medical Informatics, University of Wisconsin, Madison, Wisconsin
| | - Irene M Ong
- University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, Wisconsin
- Department of Biostatistics and Medical Informatics, University of Wisconsin, Madison, Wisconsin
- Department of Obstetrics and Gynecology, University of Wisconsin, Madison, Wisconsin
| | - Douglas G McNeel
- University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, Wisconsin.
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Suschak JJ, Williams JA, Schmaljohn CS. Advancements in DNA vaccine vectors, non-mechanical delivery methods, and molecular adjuvants to increase immunogenicity. Hum Vaccin Immunother 2017. [PMID: 28604157 DOI: 10.1080/21645515.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023] Open
Abstract
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.
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Affiliation(s)
- John J Suschak
- a U.S. Army Medical Research Institute of Infectious Diseases , Fort Detrick , MD , USA
| | | | - Connie S Schmaljohn
- a U.S. Army Medical Research Institute of Infectious Diseases , Fort Detrick , MD , USA
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Ma Z, Liu J, Wu W, Zhang E, Zhang X, Li Q, Zelinskyy G, Buer J, Dittmer U, Kirschning CJ, Lu M. The IL-1R/TLR signaling pathway is essential for efficient CD8 + T-cell responses against hepatitis B virus in the hydrodynamic injection mouse model. Cell Mol Immunol 2017; 14:997-1008. [PMID: 28757610 PMCID: PMC5719144 DOI: 10.1038/cmi.2017.43] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 05/13/2017] [Accepted: 05/13/2017] [Indexed: 12/18/2022] Open
Abstract
The outcome of hepatitis B viral (HBV) infection is determined by the complex interactions between replicating HBV and the immune system. While the role of the adaptive immune system in the resolution of HBV infection has been studied extensively, the contribution of innate immune mechanisms remains to be defined. Here we examined the role of the interleukin-1 receptor/Toll-like receptor (IL-1R/TLR) signaling pathway in adaptive immune responses and viral clearance by exploring the HBV mouse model. Hydrodynamic injection with a replication-competent HBV genome was performed in wild-type mice (WT) and a panel of mouse strains lacking specific innate immunity component expression. We found higher levels of HBV protein production and replication in Tlr2−/−, Tlr23479−/−, 3d/Tlr24−/−, Myd88/Trif−/− and Irak4−/− mice, which was associated with reduced HBV-specific CD8+ T-cell responses in these mice. Importantly, HBV clearance was delayed for more than 2 weeks in 3d/Tlr24−/−, Myd88/Trif−/− and Irak4−/− mice compared to WT mice. HBV-specific CD8+ T-cell responses were functionally impaired for producing the cytokines IFN-γ, TNF-α and IL-2 in TLR signaling-deficient mice compared to WT mice. In conclusion, the IL-1R/TLR signaling pathway might contribute to controlling HBV infection by augmenting HBV-specific CD8+ T-cell responses.
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Affiliation(s)
- Zhiyong Ma
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Jia Liu
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Weimin Wu
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Ejuan Zhang
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Xiaoyong Zhang
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Qian Li
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Gennadiy Zelinskyy
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Jan Buer
- Institute of Medical Microbiology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Ulf Dittmer
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Carsten J Kirschning
- Institute of Medical Microbiology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Mengji Lu
- Institute of Virology, University Hospital of Essen, University of Duisburg-Essen, 45122 Essen, Germany
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Suschak JJ, Williams JA, Schmaljohn CS. Advancements in DNA vaccine vectors, non-mechanical delivery methods, and molecular adjuvants to increase immunogenicity. Hum Vaccin Immunother 2017; 13:2837-2848. [PMID: 28604157 PMCID: PMC5718814 DOI: 10.1080/21645515.2017.1330236] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
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.
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Affiliation(s)
- John J Suschak
- a U.S. Army Medical Research Institute of Infectious Diseases , Fort Detrick , MD , USA
| | | | - Connie S Schmaljohn
- a U.S. Army Medical Research Institute of Infectious Diseases , Fort Detrick , MD , USA
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Abstract
DNA vaccines offer many advantages over other anti-tumor vaccine approaches due to their simplicity, ease of manufacturing, and safety. Results from several clinical trials in patients with cancer have demonstrated that DNA vaccines are safe and can elicit immune responses. However, to date few DNA vaccines have progressed beyond phase I clinical trial evaluation. Studies into the mechanism of action of DNA vaccines in terms of antigen-presenting cell types able to directly present or cross-present DNA-encoded antigens, and the activation of innate immune responses due to DNA itself, have suggested opportunities to increase the immunogenicity of these vaccines. In addition, studies into the mechanisms of tumor resistance to anti-tumor vaccination have suggested combination approaches that can increase the anti-tumor effect of DNA vaccines. This review focuses on these mechanisms of action and mechanisms of resistance using DNA vaccines, and how this information is being used to improve the anti-tumor effect of DNA vaccines. These approaches are then specifically discussed in the context of human prostate cancer, a disease for which DNA vaccines have been and continue to be explored as treatments.
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Affiliation(s)
- Christopher D Zahm
- Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI 53705, United States
| | - Viswa Teja Colluru
- Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI 53705, United States
| | - Douglas G McNeel
- Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI 53705, United States.
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Abstract
INTRODUCTION Tuberculosis (TB) remains a major health problem and novel vaccination regimens are urgently needed. AREAS COVERED DNA vaccines against TB have been tested in various preclinical models and strategies have been developed to increase their immunogenicity in large animal species. DNA vaccines are able to induce a wide variety of immune responses, including CD8(+) T-cell-mediated cytolytic and IFN-γ responses. DNA vaccination may be valuable in heterologous prime-boost strategies with the currently used bacillus Calmette-Guérin (BCG) vaccine. This approach could broaden the antigenic repertoire of BCG and enhance its weak induction of MHC class I-restricted immune responses. EXPERT OPINION DNA vaccines offer a number of advantages over certain other types of vaccines, such as the induction of robust MHC class I-restricted cytotoxic T lymphocyte (CTL), their generic manufacturing platform and their relatively low manufacturing costs. Because of their strong potential for inducing memory responses, DNA vaccines are particularly suited for priming immune responses. Furthermore, DNA vaccine technology may help antigen discovery by facilitating screening of candidate vaccines. Co-administration of BCG with plasmid DNA coding for immunodominant, subdominant and phase-specific antigens, poorly expressed by BCG, may lead to the development of improved TB vaccines.
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Affiliation(s)
- Nicolas Bruffaerts
- Scientific Institute of Public Health, O.D. CID-Immunology , Engelandstraat 642, Brussels, B1180 , Belgium
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Bruffaerts N, Romano M, Denis O, Jurion F, Huygen K. Increasing the Vaccine Potential of Live M. bovis BCG by Coadministration with Plasmid DNA Encoding a Tuberculosis Prototype Antigen. Vaccines (Basel) 2014; 2:181-95. [PMID: 26344474 PMCID: PMC4494193 DOI: 10.3390/vaccines2010181] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 02/12/2014] [Accepted: 02/19/2014] [Indexed: 02/07/2023] Open
Abstract
The attenuated live M. bovis Bacille-Calmette-Guérin (BCG) is still the sole vaccine used against tuberculosis, but confers only variable efficacy against adult pulmonary tuberculosis (TB). Though no clear explanation for this limited efficacy has been given, different hypotheses have been advanced, such as the waning of memory T-cell responses, a reduced antigenic repertoire and the inability to induce effective CD8+ T-cell responses, which are known to be essential for latent tuberculosis control. In this study, a new BCG-based vaccination protocol was studied, in which BCG was formulated in combination with a plasmid DNA vaccine. As BCG is routinely administered to neonates, we have evaluated a more realistic approach of a simultaneous intradermal coadministration of BCG with pDNA encoding the prototype antigen, PPE44. Strongly increased T- and B-cell responses were observed with this protocol in C57BL/6 mice when compared to the administration of only BCG or in combination with an empty pDNA vector, as measured by Th1-type spleen cell cytokine secretion, specific IgG antibodies, as well as specific IFN-γ producing/cytolytic-CD8+ T-cells. Moreover, we observed a bystander activation induced by the coding plasmid, resulting in increased immune responses against other non-plasmid encoded, but BCG-expressed, antigens. In all, these results provide a proof of concept for a new TB vaccine, based on a BCG-plasmid DNA combination.
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Affiliation(s)
- Nicolas Bruffaerts
- Scientific Institute of Public Health, Communicable and Infectious Diseases, Immunology, Brussels 1180, Belgium.
| | - Marta Romano
- Scientific Institute of Public Health, Communicable and Infectious Diseases, Immunology, Brussels 1180, Belgium.
| | - Olivier Denis
- Scientific Institute of Public Health, Communicable and Infectious Diseases, Immunology, Brussels 1180, Belgium.
| | - Fabienne Jurion
- Scientific Institute of Public Health, Communicable and Infectious Diseases, Immunology, Brussels 1180, Belgium.
| | - Kris Huygen
- Scientific Institute of Public Health, Communicable and Infectious Diseases, Immunology, Brussels 1180, Belgium.
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Williams JA. Vector Design for Improved DNA Vaccine Efficacy, Safety and Production. Vaccines (Basel) 2013; 1:225-49. [PMID: 26344110 PMCID: PMC4494225 DOI: 10.3390/vaccines1030225] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 06/12/2013] [Accepted: 06/18/2013] [Indexed: 12/25/2022] Open
Abstract
DNA vaccination is a disruptive technology that offers the promise of a new rapidly deployed vaccination platform to treat human and animal disease with gene-based materials. Innovations such as electroporation, needle free jet delivery and lipid-based carriers increase transgene expression and immunogenicity through more effective gene delivery. This review summarizes complementary vector design innovations that, when combined with leading delivery platforms, further enhance DNA vaccine performance. These next generation vectors also address potential safety issues such as antibiotic selection, and increase plasmid manufacturing quality and yield in exemplary fermentation production processes. Application of optimized constructs in combination with improved delivery platforms tangibly improves the prospect of successful application of DNA vaccination as prophylactic vaccines for diverse human infectious disease targets or as therapeutic vaccines for cancer and allergy.
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Affiliation(s)
- James A Williams
- Nature Technology Corporation/Suite 103, 4701 Innovation Drive, Lincoln, NE 68521, USA.
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Elnekave M, Furmanov K, Hovav AH. Intradermal naked plasmid DNA immunization: mechanisms of action. Expert Rev Vaccines 2012; 10:1169-82. [PMID: 21854310 DOI: 10.1586/erv.11.66] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Plasmid DNA is a promising vaccine modality that is regularly examined in prime-boost immunization regimens. Recent advances in skin immunity increased our understanding of the sophisticated cutaneous immune network, which revived scientific interest in delivering vaccines to the skin. Intradermal administration of plasmid DNA via needle injection is a simple and inexpensive procedure that exposes the plasmid and its encoded antigen to the dermal immune surveillance system. This triggers unique mechanisms for eliciting local and systemic immunity that can confer protection against pathogens and tumors. Understanding the mechanisms of intradermal plasmid DNA immunization is essential for enhancing and modulating its immunogenicity. With regard to vaccination, this is of greater importance as this routine injection technique is highly desirable for worldwide immunization. This article will focus on the current understanding of the mechanisms involved in antigen expression and presentation during primary and secondary syringe and needle intradermal plasmid DNA immunization.
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Affiliation(s)
- Mazal Elnekave
- Institute of Dental Sciences, Hebrew University-Hadassah School of Dental Medicine, PO Box 122722, Jerusalem 91120, Israel
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Sin JI. MyD88 signal is required for more efficient induction of Ag-specific adaptive immune responses and antitumor resistance in a human papillomavirus E7 DNA vaccine model. Vaccine 2011; 29:4125-31. [PMID: 21496466 DOI: 10.1016/j.vaccine.2011.03.098] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 03/17/2011] [Accepted: 03/25/2011] [Indexed: 11/29/2022]
Abstract
The function of MyD88 signals for induction of adaptive immunity is still controversial. Here we investigate using a human papillomavirus (HPV) 16 E7 DNA vaccine on MyD88 knock out mouse model whether MyD88 signals are required for induction of Ag-specific antibody and cellular responses, as well as antitumor resistance. When injected intramuscularly with E7 DNA vaccines, MyD88 deficient mice displayed antitumor protective responses to tumor cell challenges while having far lower responses than wild type mice. A similar finding was observed in antitumor therapeutic models by intramuscular-electroporation of E7 DNA vaccines. E7 DNA vaccines induced Ag-specific humoral and CD8+ CTL responses in MyD88 deficient mice. However, the levels were much less than those of wild type mice. These data suggest that the immune stimulatory sequence of E7 DNA vaccines and its signaling through MyD88 are not absolutely essential for induction of adaptive immune responses. However, MyD88 deficient mice co-delivered with MyD88 cDNA plus E7 DNA vaccines showed a recovery of Ag-specific IgG and CTL responses, and antitumor immunity to the levels of wild type mice, highlighting the importance of MyD88 signals for augmenting an adaptive immune response. Thus, these data clearly show that MyD88 signals are required only for more efficient induction of Ag-specific humoral and antitumor CD8+ CTL responses in this model.
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Affiliation(s)
- Jeong-Im Sin
- Department of Microbiology, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do 200-701, Republic of Korea.
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The innate immune adaptor molecule MyD88 restricts West Nile virus replication and spread in neurons of the central nervous system. J Virol 2010; 84:12125-38. [PMID: 20881045 DOI: 10.1128/jvi.01026-10] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Type I interferons (IFN-α/β) control viral infection by triggering the expression of genes that restrict transcription, translation, replication, and assembly. Many viruses induce IFN responses after recognition by cytoplasmic or endosomal RNA sensors (RIG-I-like RNA helicases [RLR] and Toll-like receptors [TLR]), which signal through the cognate adaptor signaling molecules IPS-1, TRIF, and MyD88. Recent studies have demonstrated that IPS-1-dependent induction of IFN-α/β downstream of RLR recognition restricts West Nile virus (WNV) infection in many cell types, whereas TRIF-dependent TLR3 signaling limits WNV replication in neurons. Here, we examined the contribution of MyD88 signaling to the control of WNV by evaluating IFN induction and virus replication in genetically deficient cells and mice. MyD88(-/-) mice showed increased lethality after WNV infection and elevated viral burden primarily in the brain, even though little effect on the systemic type I IFN response was observed. Intracranial inoculation studies corroborated these findings, as WNV spread more rapidly in the central nervous system of MyD88(-/-) mice, and this phenotype preceded the recruitment of inflammatory leukocytes. In vitro, increased WNV replication was observed in MyD88(-/-) macrophages and subsets of neurons but not in myeloid dendritic cells. MyD88 had an independent effect on recruitment of monocyte-derived macrophages and T cells into the brain that was associated with blunted induction of the chemokines that attract leukocytes. Our experiments suggest that MyD88 restricts WNV by inhibiting replication in subsets of cells and modulating expression of chemokines that regulate immune cell migration into the central nervous system.
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Rottembourg D, Filippi CM, Bresson D, Ehrhardt K, Estes EA, Oldham JE, von Herrath MG. Essential role for TLR9 in prime but not prime-boost plasmid DNA vaccination to activate dendritic cells and protect from lethal viral infection. THE JOURNAL OF IMMUNOLOGY 2010; 184:7100-7. [PMID: 20483769 DOI: 10.4049/jimmunol.0803935] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
One of the requirements for efficient vaccination against infection is to achieve the best combination of an adequate adjuvant with the antigenic information to deliver. Although plasmid DNA is a promising tool bearing the unique potential to activate humoral and cellular immunity, an actual challenge is to increase plasmid immunogenicity in human vaccination protocols in which efficacy has proven rather limited. Previous work showed that the bacterial DNA backbone of the plasmid has potent adjuvant properties because it contains CpG motifs that are particular activating nucleotidic sequences. Among TLRs, which are key sensors of microbial products, TLR9 can detect CpG motifs and confer activation of APCs, such as dendritic cells. However, whether the immunogenic properties of plasmid DNA involve TLR9 signaling has not been clearly established. In the current study, we demonstrate that TLR9 determines the effectiveness of vaccination against lethal lymphocytic choriomeningitis virus infection using plasmid DNA in a prime, but not prime-boost, vaccination regimen. Furthermore, we provide evidence that the presence of TLR9 in dendritic cells is necessary for effective and functional priming of virus-specific CD8+ T cells upon plasmid exposure in vitro or single-dose vaccination in vivo. Therefore, at single or low vaccine doses that are often used in human-vaccination protocols, CpG/TLR9 interactions participate in the immunogenicity of plasmid DNA. These results suggest that the TLR9 signaling pathway is involved in the efficacy of plasmid vaccination; therefore, it should remain a focus in the development or amelioration of vaccines to treat infections in humans.
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Affiliation(s)
- Diane Rottembourg
- La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA
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Abstract
Adjuvants are substances that boost the immunogenicity of vaccines. However, most successful vaccines have been derived empirically and are capable of inducing robust T- and B-cell immunity without any adjuvant additives. Emerging evidence suggests that such live vaccines induce innate immune activation via a range of stimuli, including ligands specific for Toll-like receptors, which, in effect, serve as their own adjuvants. In contrast to these live vaccines, subunit vaccines need to be supplemented with adjuvants to boost their immunogenicity. However, there is a paucity of licensed adjuvants for clinical use and, thus, there is a critical need to develop safe and effective adjuvants. In this context, recent advances in innate immunity are beginning to offer new insights into how empiric vaccines and adjuvants mediate their efficacy. In this article, we review the latest progress and emerging concepts in adjuvant development, which includes novel findings in innate immune biology and their impact on vaccinology.
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Affiliation(s)
- Marcin Kwissa
- Emory Vaccine Center, Emory University, 954 Gatewood Rd, Atlanta, GA 30329, USA.
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