- Open Access
Engineered biomaterials for development of nucleic acid vaccines
© Yang et al.; licensee BioMed Central. 2015
Received: 23 August 2014
Accepted: 23 December 2014
Published: 19 February 2015
Nucleic acid vaccines have attracted many attentions since they have presented some superiority over traditional vaccines. However, they could only induce moderate immunogenicity. The route and formulation of nucleic acid vaccines have strong effects on the immune response and efficiency. Numerous biomaterials are used as a tool to enhance the immunogenicity of antigens. They deliver the antigens into the cells through particle- and non-particle-mediated pathway. However, challenges remain due to lack of comprehensive understanding of the actions of these biomaterials as a carrier/adjuvant. Herein, this review focuses on the evolution of biomaterials used for nucleic acid vaccines, discusses the advantages and disadvantages for gene delivery and immunostimulation of variety of structures of the biomaterials, in order to provide new thought on rational design of carrier/adjuvant and better understanding of mechanism of action in both immunostimulatory and delivery methods.
Since Edward Jenner developed the first cowpox vaccine as a prophylactic treatment for smallpox in 1796 [1,2], vaccines have gained remarkable achievements from then on. Nowadays, vaccines are defined as biological agents, which are prepared by disease-causing bacteria, viruses and so on, to stimulate the host’s immune system for protection from a disease and for treatment. Conventional vaccines, including inactivated, live attenuated viruses, have made great progress, and some of them have been used in clinical use [3-6]. However, these vaccines could also pose potential risks, which highlighted the need for novel vaccine strategies.
For past two decades, nucleic acid vaccines, including DNA and RNA, had exhibited a great promise in immunotherapy for infectious diseases [7,8], cancers [9,10], autoimmune diseases  and allergy . Nucleic acid vaccines, namely genetic vaccines, is to deliver genetic materials encoding the antigens of interest into host cells and directly express antigen protein in suit, finally initiating an immune responses of the host to protect from following challenge and disease therapy. Early administration of DNA vaccines in mice were through gene gun technology and naked DNA injection [13,14]. Comparing with conventional vaccines, the nucleic acid vaccines have represented superiorities, such as good safety, specific to induce the immune response for the antigen of interest, induction of both B- and T-cell responses, relatively low cost of production, and ease of manufacturing [9,10,15]. Numerous clinical trials of DNA vaccines have been made, and they have shown promise in animal models. Like the West Nile Virus DNA vaccine, safe and well tolerated, has been used to protect wild Californian condors and licensed for use in horses [16,17]. However, they have initiated poorly immunogenic effects in clinic trials and have not yet used in human as commercial products . The inherent barriers of the body limits DNA entering into cells to a great extent, which results in few antigens produced after using large scale of DNA, and finally exhibits low efficiency of immune response. Moreover, the poor stability and in vivo distribution of the naked form and the lack of clinical feasible delivery methods hinder the efficiency for nucleic acid vaccines.
For administration of these nucleic acid vaccines to the target cells, there are many extra- and intracellular barriers that must be conquered to promote expression of antigens, including effective transportation, prevention from degradation, association with APCs, endosomal escape, release of nucleic acids to express antigen efficiently. Gene delivery should occur in proper routes with sufficient expression to initiate efficient innate and adaptive immune responses and generate strong immunity. Considering with these, recent studies for biomaterial development applying for nucleic acid vaccines are reviewed in this work for better understanding the role of biomaterials as carriers or adjuvant, and discuss the barriers to antigen expression and immune responses generation in gene delivery systems, which will provide new thoughts toward development of rational design of biomaterials for nucleic acid vaccines. In this review, the most studied delivery biomaterials for DNA vaccines will be represented in detail, from the inorganic biomaterials, polymer, and peptide to lipid-based formulation. The recent reported self-amplifying RNA formulation is also included since it uses the lipid-based formulation for gene delivery, which is very helpful for development of delivery vectors for nucleic acid vaccines.
DNA has distinctive features as vaccine, such as it needs to express the antigenic protein after entering the nuclei, which demands reasonable design of delivery vectors for the DNA vaccines. In order to efficiently deliver DNA antigen into cell nuclei and enhance the immunogenicity of DNA vaccines, several strategies on biomaterials have been investigated.
Particle-mediated DNA vaccine
Inorganic biomaterial-based formulation
Many inorganic biomaterials have been exploited as carriers/adjuvants for vaccines. Aluminium salts are the most broadly used immune adjuvants for vaccines by adsorbing the antigen onto their surfaces . They have been approved for use in humans. The formulation of aluminium adjuvants with DNA vaccines could enhance the antibody responses up to 10–100 folds in small model of animals [25,26]. However, the aluminium salts exhibited strong adjuvant effects only when the adjuvant did not bind to the plasmid DNA. Moreover, they exhibited potential adverse local reactions, easy degradation during freeze-drying, and demand multiple administrations to gain long-lasting protection [27,28]. Most importantly, the adsorption of DNA antigen on the alum surface could not effectively protect the genetic materials from digestion by nucleases during the delivery process.
PEI, as a very efficient gene delivery vector, has attracted much more attention since it has high cationic charge potential and facilitates endosomal escape through the hypothesized “proton sponge” mechanism [43,44]. The costimulatory effect of PEI as adjuvants could enhance the class I-mediated tumor-specific cytotoxic T lymphocytes (CTLs) and class II-mediated Th1/Th2 activation when administrated as PEI-mediated DNA cancer vaccines, which resulted in suppressed tumor growth and prolonged survival rate. Branched PEI, especially branched PEI25k, is widely used as its excellent performance for gene delivery. However, the severe cytotoxicity inhibits its further application. Hence, balance between efficiency and toxicity should be well considered during construction of delivery system. Some strategies were exploited to prompt their applications as adjuvants, such as adopting low-molecular weight PEI or combination with other biomaterials, which expressed excellent biocompatibility and biodegradability [45,46]. A mannosylated PEI/DNA complex was constructed with low-molecular weight PEI and used to induce upregulation of surface markers for DC maturation, which expressed large scale of mannose receptor on the surface [47,48]. This modified PEI exhibited similar condensing properties with branched PEI25k, whereas had less cytotoxicity and better transfection. These studies demonstrated that rational modification of the structures of PEI was very important to regulate the balance between transfection efficiency and toxicity of the polymers.
Poly(L-lysine) (PLL), as a synthesized polypeptide biomaterial, could be protonated at the primary amino groups of lysine to interact with DNA. However, it was limited for use as gene carriers since it had high cationic toxicity and sufficient escape from endosomes . Herein, though PLL was biodegradable, additional agents needed to help DNA release from endosomes. Poly(β-amino ester) (PBAE) could be facile synthesized by amine and diacrylates to form large scales of combinatorial biomaterials. This made they had variable structures and tunable properties. A combinatorial library of over 2000 PBAE was studied and end-modified PBAE generated significant enhancement in gene tranfection in vitro and in vivo . This approach provided comparable gene delivery in vitro in comparison with adenovirus.
Synthesized biomaterials could effectively load the nucleic acid in abundance since they always contained a large amount of positively charged ions. However, these cations brought them high toxicity. Considering with the high and efficient cellular uptake and gene transfection, strategies to minimize toxicity of these synthesized biomaterials were very crucial for their application as adjuvant towards clinic use.
Natural polymers, like chitosan, have been exploited to act as vaccine carriers and adjuvants due to their natural nontoxicity and excellent biocompatibility, and they could be used as an alternative through oral or mucosal routes to delivery nucleic acid vaccine for protection [51,52]. Nano-chitosan could help enhance the vaccination effects of Esat-6/3e-FL DNA vaccine containing Esat-6 three T cell epitopes and fms-like tyrosine kinase 3 ligand genes against Mycobacterium tuberculosis (M.tb) by prompting cellular uptake and protective ability of the vaccine . To enhance the delivery efficiency, mannose receptor-mediated endocytosis was applied in chitosan-DNA vaccine (MCS/pGRP) for nasal mucosal delivery by Zong et al. . Intranasal immunization with this targeting nanoparticles elicited strong systemic responses and significantly higher specific anti-GRP antibody levels comparing with non-targeting one, and the IgG levels were 3-fold higher at 7th week.
The linear cationic polysaccharide was facilitated the mucosal administration method due to the natural mucoadhesive properties. They represented sustained-release as nanogels and were a promise delivering carrier for DNA vaccine. It was worth noting that a proper targeting could effectively enhance specific delivery to APC and lymph node.
Moreover, adjuvant was combined for potent and continuous immunity. Stephen J. Kent and Frank Caruso’s group designed redox-responsive polypeptide particles (poly(L-glutamic acid), PGA) with controlled loading capacity by covalently conjugating an oligonucleotide adjuvant (CpG) with a disulfide bond . The particles elicited different levels of activation of primary human blood pDCs population through simply tuning of the loading capacity governed by controlling the cross-linking density. The mechanically tunable and self-adjuvanting particles provided a relatively stable and high antigen loading system for improved vaccine immunogenicity.
Cationic lipids are widely used and recognized as one of the most promising delivery vectors for nucleic acids as they could condense nucleic acids to form lipid/nucleic acids complexes, which protects them from being digested by nucleases. For gene delivery, nucleic acids are usually encapsulated into cationic lipid-based liposomes. They can easily merge with the cell membrane since they are both made of a phospholipid bilayer. Liposomes could be modified to suit any antigen by changing their physical properties, like sizes, surface charge, lipid compositions, targeting, etc. [59-61], and they could mimic the pathogens and exert potent long-lasting immune responses . Moreover, cationic liposomes could prompt dendritic cell maturation and induce a series of cytokines and chemokines, and some of them have been entered into clinical trials [63,64].
The rational design of liposomes for DNA vaccines should consider the influence factors for antigen uptake and trafficking to draining lymph nodes. The lipid composition, size and surface charge of liposomes, and membrane fluidity are the structural factors that affect immune responses. Though there have been made huge efforts to explore lipid-based formulation, only a few of them have been approved for clinical use . The clinical applications of liposomes remain limited due to in vivo instability, difficulty in generating reproducible formulation and large-scale of production, and relatively higher cost. Also, some important questions need to be addressed, such as the mechanism of cationic lipids as adjuvants and the real interaction between lipids and antigens in vivo. These all require deep investigation in the interconnection of lipid and vaccines.
Non-particle-mediated DNA vaccines
Comparing with DNA vaccine, the investigation of RNA vaccine was relatively less, which might due to the properties of RNA, such as difficult preparation and less stability. However, the RNA still attracted many attentions as a promising alternative in prophylactic and therapeutic vaccines. They exhibited several advantages over the DNA vaccines. For example, they could avoid the nuclear membranous barriers since they exerted their functions in the cytoplasm. The most studied RNA vaccines were with naked RNA, electroporation and lipid-based formulations .
Comparing with DNA vaccine, these RNA vaccines could bypass the rate-limiting barrier for pDNA delivery by self-amplifying and expressing in cytoplasm. However, the in vivo stability and storage strategies of RNA vaccines will require further studies to improve the current status of vaccine development.
Gene-based vaccines have become a favored strategy for inducing immunity. However, the lower immunogenicity of nucleic acid vaccines has hindered their progress in humans. Long-lasting stability and controlled release of the nucleic acid antigens are crucial for the development of much more efficient vaccines. From the review of the development of biomaterials, some important issues should consider to design the delivering vectors for vaccines. Firstly, considering the stability of nucleic acid antigens in vivo, ideal nucleic acid carriers should provide protection during the delivery process and specific target to immune tissues. This will greatly enhance the accumulation of nucleic acid antigens in targeting cells, especially the antigen presenting cells in draining lymph nodes, which are very crucial for inducing strong immune response. Secondly, the delivery vectors could act as costimulators for vaccines. Like discussion in this review, numerous biomaterial vectors exhibit potential immune responses due to their tunable mechanical properties and adjusted multifunction for combining with other costimulators, such as CpG and cytokines. This multifunctional delivery vector will improve the immunogenicity of nucleic acid vaccines. Thirdly, the delivery vectors should provide sustained release of nucleic acid antigens, which will establish the immunological memory for prolonged surveillance against pathogens or cancer cells.
Herein, diversified and multifunctional biomaterials provide us numerous strategies for improving the nucleic acid vaccine performance. However, challenges remain due to a lack of deep and comprehensive understanding the in vivo behavior of delivery vectors and immunostimulative mechanism. Therefore, intensive and comprehensive understanding of the mechanism of biomaterial vector on both delivery routes and immunostimulatory are very crucial for rational design of delivery vectors for vaccines, and will accelerate the development of nucleic acid vaccine for clinical application.
This study was financially supported by the National Natural Science Foundation of China (Grants NO. 21304099, 30970784, 31170873, 51103159, 51203162, 51373177 and 81171455), the National High Technology Research and Development Program (Grants NO. 2012AA022703, 2012AA020804, 2014AA020708), the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YZ201253, YZ201313), the Open Funding Project of the National Key Laboratory of Biochemical Engineering (Grant No. Y22504A169), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09030301, XDA09030301-3), the National Key Basic Research Program of China (2009CB930200), National Distinguished Young Scholars grant (31225009) from the National Natural Science Foundation of China and Chinese Academy of Sciences (CAS) “Hundred Talents Program” (07165111ZX).
- Jenner E. An inquiry into the causes and effects of the variolae vaccinae, a disease discovered in some of the western counties of England, particularly Gloucestershire, and known by the name of the cow pox. 1798, New York: General Books.Google Scholar
- Behbehani AM. The smallpox story: life and death of an old disease. Microbiol Rev. 1983;47(4):455–509.Google Scholar
- Peek LJ, Middaugh CR, Berkland C. Nanotechnology in vaccine delivery. Adv Drug Deliv Rev. 2008;60(8):915–28.View ArticleGoogle Scholar
- Kubba AK, Taylor P, Graneek B, Strobel S. Non-responders to hepatitis B vaccination: a review. Commun Dis Public Health. 2003;6:106–12.Google Scholar
- Plotkin SA. Vaccines: past, present and future. Nat Med. 2005;11(4 Suppl):S5–11.View ArticleGoogle Scholar
- Plotkin SA, Orenstein WA, Offit PA. Vaccines. Philadelphia: Saunders; 2008.Google Scholar
- Laddy DJ, Weiner DB. From plasmids to protection: a review of DNA vaccines against infectious diseases. Int Rev Immunol. 2006;25(3–4):99–123.View ArticleGoogle Scholar
- Chiarella P, Massi E, Robertis MD, Fazio VM, Signori E. Strategies for effective naked-DNA vaccination against infectious diseases. Recent Pat Antiinfect Drug Discov. 2008;3(2):93–101.View ArticleGoogle Scholar
- Rice J, Ottensmeier CH, Stevenson FK. DNA vaccines: precision tools for activating effective immunity against cancer. Nat Rev Cancer. 2008;8(2):108–20.View ArticleGoogle Scholar
- Stevenson FK, Ottensmeier CH, Johnson P, Zhu D, Buchan SL, McCann KJ, et al. DNA vaccines to attack cancer. Proc Natl Acad Sci U S A. 2004;101 Suppl 2:14646–52.View ArticleGoogle Scholar
- Ferrera F, Lacava A, Rizzi M, Hahn BH, Indiveri F, Filaci G. Gene vaccination for the induction of immune tolerance. Ann N Y Acad Sci. 2007;1110:99–111.View ArticleGoogle Scholar
- Richard W, Sandra S, Elisabeth R, Fatima F, Josef T. Prophylactic mRNA vaccination against allergy. Curr Opin Allergy Clin Immunol. 2010;10(6):567–74.View ArticleGoogle Scholar
- Sardesai NY, Weiner DB. Electroporation delivery of DNA vaccines: prospects for success. Curr Opin Immunol. 2011;23(3):421–9.View ArticleGoogle Scholar
- Porgador A, Irvine KR, Iwasaki A, Barber BH, Restifo NP, Germain RN. Predominant role for directly transfected dendritic cells in antigen presentation to CD8+ T cells after gene gun immunization. J Exp Med. 1998;188(6):1075–82.View ArticleGoogle Scholar
- Kutzler MA, Weiner DB. DNA vaccines: ready for prime time? Nat Rev Genet. 2008;9(10):776–88.View ArticleGoogle Scholar
- Ledgerwood JE, Pierson TC, Hubka SA, Desai N, Rucker S, Gordon IJ, et al. A West Nile virus DNA vaccine utilizing a modified promoter induces neutralizing antibody in younger and older healthy adults in a phase I clinical trial. J Infect Dis. 2011;203(10):1396–404.View ArticleGoogle Scholar
- Martin JE, Pierson TC, Hubka S, Rucker S, Gordon IJ, Enama ME, et al. A West Nile virus DNA vaccine induces neutralizing antibody in healthy adults during a phase 1 clinical trial. J Infect Dis. 2007;196(12):1732–40.View ArticleGoogle Scholar
- Liu MA, Ulmer JB. Human clinical trials of plasmid DNA vaccines. Adv Genet. 2005;55:25–40.View ArticleGoogle Scholar
- Buchan S, Grønevik E, Mathiesen I, King CA, Stevenson FK, Rice J. Electroporation as a “prime/boost” strategy for naked DNA vaccination against a tumor antigen. J Immunol. 2005;174(10):6292–8.View ArticleGoogle Scholar
- Johansson DX, Ljungberg K, Kakoulidou M, Liljeström P. Intradermal electroporation of naked replicon RNA elicits strong immune responses. PLoS One. 2012;7(1):e29732.View ArticleGoogle Scholar
- Yang J, Liu H, Zhang X. Design, preparation and application of nucleic acid delivery carriers. Biotechnol Adv. 2014;32(4):804–917.View ArticleGoogle Scholar
- Mora-Solano C, Collier JH. Engaging adaptive immunity with biomaterials. J Mater Chem B Mater Biol Med. 2014;2(17):2409–21.View ArticleGoogle Scholar
- Rodríguez-Gascón A, Pozo-Rodríguez A, Solinís MÁ. Development of nucleic acid vaccines: use of self-amplifying RNA in lipid nanoparticles. Int J Nanomedicine. 2014;9:1833–43.View ArticleGoogle Scholar
- Marrack P, McKee AS, Munks MW. Towards an understanding of the adjuvant action of aluminium. Nat Rev Immunol. 2009;9(4):287–93.View ArticleGoogle Scholar
- Ulmer JB, DeWitt CM, Chastain M, Friedman A, Donnelly JJ, McClements WL, et al. Enhancement of DNA vaccine potency using conventional aluminum adjuvants. Vaccine. 2000;18:18–28.View ArticleGoogle Scholar
- Wang S, Liu X, Fisher K, Smith JG, Chen F, Tobery TW, et al. Enhanced type I immune response to a hepatitis B DNA vaccine by formulation with calcium- or aluminum phosphate. Vaccine. 2000;18:1227–35.View ArticleGoogle Scholar
- Correia-Pintoa JF, Csaba N, Alonso MJ. Vaccine delivery carriers: insights and future perspectives. Int J Pharm. 2013;440(1):27–38.View ArticleGoogle Scholar
- Tomljenovic L, Shaw CA. Aluminum vaccine adjuvants: are they safe? Curr Med Chem. 2011;18(17):2630–7.View ArticleGoogle Scholar
- Chakravarthy KV, Bonoiu AC, Davis WG, Ranjan P, Ding H, Hu R, et al. Gold nanorod delivery of an ssRNA immune activator inhibits pandemic H1N1 influenza viral replication. Proc Natl Acad Sci U S A. 2010;107(22):10172–7.View ArticleGoogle Scholar
- Salem AK, Searson PC, Leong KW. Multifunctional nanorods for gene delivery. Nat Mater. 2003;2(10):668–71.View ArticleGoogle Scholar
- Almeida JPM, Figueroa ER, Drezek RA. Gold nanoparticle mediated cancer immunotherapy. Nanomedicine. 2014;10(3):503–14.View ArticleGoogle Scholar
- Xu L, Liu Y, Chen Z, Li W, Liu Y, Wang L, et al. Surface-Engineered Gold Nanorods: Promising DNA Vaccine Adjuvant for HIV-1 Treatment. Nano Lett. 2012;12:2003–12.View ArticleGoogle Scholar
- Grant EV, Thomas M, Fortune J, Klibanov AM, Letvin NL. Enhancement of plasmid DNA immunogenicity with linear polyethylenimine. Eur J Immunol. 2012;42:2937–48.View ArticleGoogle Scholar
- Patnaik S, Gupta KC. Novel polyethylenimine-derived nanoparticles for in vivo gene delivery. Expert Opin Drug Deliv. 2013;10(2):215–28.View ArticleGoogle Scholar
- Huang R, Liu S, Shao K, Han L, Ke W, Liu Y, et al. Evaluation and mechanism studies of PEGylated dendrigraft poly-L-lysines as novel gene delivery vectors. Nanotechnology. 2010;21(26):265101–11.View ArticleGoogle Scholar
- Hofman J, Buncek M, Haluza R, Ludvik S, Ledvina M, Cigler P. In vitro transfection mediated by dendrigraft poly(L-lysines): the effect of structure and molecule size. Macromol Biosci. 2013;13(2):167–76.View ArticleGoogle Scholar
- Little SR, Lynn DM, Puram SV, Langer R. Formulation and characterization of poly (beta amino ester) microparticles for genetic vaccine delivery. J Control Release. 2005;107(3):449–62.View ArticleGoogle Scholar
- Little SR, Lynn DM, Ge Q, Anderson DG, Puram SV, Chen J, et al. Poly-beta amino ester-containing microparticles enhance the activity of nonviral genetic vaccines. Proc Natl Acad Sci U S A. 2004;101(26):9534–9.View ArticleGoogle Scholar
- Shen Y, Tang H, Zhan Y, Kirk EAV, Murdoch WJ. Degradable Poly(β-amino ester) nanoparticles for cancer cytoplasmic drug delivery. Nanomedicine. 2009;5:192–201.View ArticleGoogle Scholar
- Zhang B, Ma X, Murdoch W, Radosz M, Shen Y. Bioreducible poly(amido amine)s with different branching degrees as gene delivery vectors. Biotechnol Bioeng. 2013;110:990–8.View ArticleGoogle Scholar
- Huang B, Kukowska-Latallo JF, Tang S, Zong H, Johnson KB, Desai A, et al. The facile synthesis of multifunctional PAMAM dendrimer conjugates through copper-free click chemistry. Bioorg Med Chem Lett. 2012;22(9):3152–6.View ArticleGoogle Scholar
- Zhang X, Sharma KK, Boeglin M, Ogier J, Mainard D, Voegel J-C, et al. Transfection ability and intracellular DNA pathway of nanostructured gene-delivery systems. Nano Lett. 2008;8(8):2432–6.View ArticleGoogle Scholar
- Ma Y-F, Yang Y-W. Delivery of DNA-based cancer vaccine with polyethylenimine. Eur J Pharm Sci. 2010;40(2):75–83.View ArticleGoogle Scholar
- Akinc A, Thomas M, Klibanov AM, Langer R. Exploring polyethylenimine-mediated DNA transfection and the proton sponge hypothesis. J Gene Med. 2005;7(5):657–63.View ArticleGoogle Scholar
- Negash T, Liman M, Rautenschlein S. Mucosal application of cationic poly(d, l-lactide-co-glycolide) microparticles as carriers of DNA vaccine and adjuvants to protect chickens against infectious bursal disease. Vaccine. 2013;31:3656–62.View ArticleGoogle Scholar
- Zhou X, Liu B, Yu X, Zha X, Zhang X, Chen Y, et al. Controlled release of PEI/DNA complexes from mannose-bearing chitosan microspheres as a potent delivery system to enhance immune response to HBV DNA vaccine. J Control Release. 2007;121(3):200–7.View ArticleGoogle Scholar
- Li M, Jiang Y, Xu C, Zhang Z, Sun X. Enhanced immune response against HIV-1 induced by a heterologous DNA prime-adenovirus boost vaccination using mannosylated polyethyleneimine as DNA vaccine adjuvant. Int J Nanomedicine. 2013;8:1843–54.Google Scholar
- Sun X, Chen S, Han J, Zhang Z. Mannosylated biodegradable polyethyleneimine for targeted DNA delivery to dendritic cells. Int J Nanomedicine. 2012;7:2929–42.View ArticleGoogle Scholar
- Männistö M, Vanderkerken S, Toncheva V, Elomaa M, Ruponen M, Schacht E, et al. Structure-activity relationships of poly(L-lysines): effects of pegylation and molecular shape on physicochemical and biological properties in gene delivery. J Control Release. 2002;83(1):169–82.View ArticleGoogle Scholar
- Green JJ, Zugates GT, Tedford NC, Huang Y-H, Griffith LG, Lauffenburger DA, et al. Combinatorial modification of degradable polymers enables transfection of human cells comparable to adenovirus. Adv Mater. 2007;19:2836–42.View ArticleGoogle Scholar
- Liu Z, Lv D, Liu S, Gong J, Wang D, Xiong M, et al. Alginic acid-coated chitosan nanoparticles loaded with legumain DNA vaccine: effect against breast cancer in mice. PLoS One. 2013;8(4):e60190.View ArticleGoogle Scholar
- Yao W, Peng Y, Du M, Luo J, Zong L. Preventative vaccine-loaded mannosylated chitosan nanoparticles intended for nasal mucosal delivery enhance immune responses and potent tumor immunity. Mol Pharmaceutics. 2013;10:2904–14.View ArticleGoogle Scholar
- Feng G, Jiang Q, Xia M, Lu Y, Qiu W, Zhao D, et al. Enhanced immune response and protective effects of nano-chitosan-based DNA vaccine encoding T cell epitopes of Esat-6 and FL against mycobacterium tuberculosis infection. PLoS One. 2013;8(4):e61135.View ArticleGoogle Scholar
- Rudra JS, Tian YF, Jung JP, Collier JH. A self-assembling peptide acting as an immune adjuvant. Proc Natl Acad Sci U S A. 2010;107(2):622–7.View ArticleGoogle Scholar
- Rudra JS, Sun T, Bird KC, Daniels MD, Gasiorowski JZ, Chong AS, et al. Modulating Adaptive Immune Responses to Peptide Self-Assemblies. ACS Nano. 2012;6(2):1557–64.View ArticleGoogle Scholar
- Cui J, Rose RD, Best JP, Johnston APR, Alcantara S, Liang K, et al. Mechanically tunable, self-adjuvanting nanoengineered polypeptide particles. Adv Mater. 2013;25(25):3468–72.View ArticleGoogle Scholar
- Tian Y, Wang H, Liu Y, Mao L, Chen W, Zhu Z, et al. A peptide-based nanofibrous hydrogel as a promising DNA nanovector for optimizing the efficacy of HIV vaccine. Nano Lett. 2014;14:1439–45.View ArticleGoogle Scholar
- Minigo G, Scholzen A, Tang CK, Hanley JC, Kalkanidis M, Pietersz GA, et al. Poly-l-lysine-coated nanoparticles: a potent delivery system to enhance DNA vaccine efficacy. Vaccine. 2007;25:1316–27.View ArticleGoogle Scholar
- Henriksen-Lacey M, Korsholm KS, Andersen P, Perrie Y, Christensen D. Liposomal vaccine delivery systems. Expert Opin Drug Deliv. 2011;8(4):505–19.View ArticleGoogle Scholar
- Un K, Kawakami S, Suzuki R, Maruyama K, Yamashita F, Hashida M. Development of an ultrasound-responsive and mannose-modified gene carrier for DNA vaccine therapy. Biomaterials. 2010;31:7813–26.View ArticleGoogle Scholar
- Perrie Y, Frederik PM, Gregoriadis G. Liposome-mediated DNA vaccination: the effect of vesicle composition. Vaccine. 2001;19:3301–10.View ArticleGoogle Scholar
- Watson DS, Endsley AN, Huang L. Design considerations for liposomal vaccines: influence of formulation parameters on antibody and cell-mediated immune responses to liposome associated antigens. Vaccine. 2012;30(13):2256–72.View ArticleGoogle Scholar
- Ginn SL, Alexander IE, Edelstein ML, Abedi MR, Wixon J. Gene therapy clinical trials worldwide to 2012 - an update. J Gene Med. 2013;15:65–77.View ArticleGoogle Scholar
- Stopeck AT, Jones A, Hersh EM, Thompson JA, Finucane DM, Gutheil JC, et al. Phase II study of direct intralesional gene transfer of allovectin-7, an HLA-B7/beta2-microglobulin DNA-liposome complex, in patients with metastatic melanoma. Clin Cancer Res. 2001;7(8):2285–91.Google Scholar
- DeMuth PC, Min Y, Huang B, Kramer JA, Miller AD, Barouch DH, et al. Polymer multilayer tattooing for enhanced DNA vaccination. Nat Mater. 2013;12(4):367–76.View ArticleGoogle Scholar
- Pollard C, Rejman J, Haes WD, Verrier B, Gulck EV, Naessens T, et al. Type I IFN counteracts the induction of antigen-specific immune responses by lipid-based delivery of mRNA vaccines. Mol Ther. 2013;21(1):251–9.View ArticleGoogle Scholar
- Geall AJ, Verma A, Otten GR, Shaw CA, Hekele A, Banerjee K, et al. Nonviral delivery of self-amplifying RNA vaccines. Proc Natl Acad Sci U S A. 2012;109(36):14604–9.View ArticleGoogle Scholar
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.