Cell-penetrating peptide-linked polymers as carriers for mucosal vaccine delivery

Validation of the Absorption-Enhancing Ability of Oligoarginines Grafted onto a Backbone of Hyaluronic Acid through Animal Studies from Rodents to Primates

The purpose of our research is to develop functional additives that enhance mucosal absorption of biologics, such as peptide/protein and antibody drugs, to provide their non-to-poor invasive dosage forms self-managed by patients. Our previous in vivo and in vitro studies demonstrated that the intranasal absorption of biologics in mice was significantly improved when coadministered with oligoarginines anchored chemically to hyaluronic acid via a glycine spacer, presumably through syndecan-4-mediated macropinocytosis under activation by oligoarginines. The present mouse experiments first revealed that diglycine-L-tetraarginine-linked hyaluronic acid significantly enhanced the intranasal absorption of sulpiride, which is a poor-absorptive organic compound with a low molecular weight. However, similar enhancement was not observed for levofloxacin, which has a similarly low molecular weight but is a well-absorptive organic compound, probably because its absorption was mostly dominated by passive diffusion. The subsequent monkey experiments revealed that there was no species difference in the absorption-enhancing ability of diglycine-L-tetraarginine-linked hyaluronic acid for not only organic compounds but also biologics. This was presumably because the expression levels of endocytosis-associated membrane proteins on the nasal mucosa in monkeys were almost equivalent to those in mice, and poorly membrane-permeable/membrane-impermeable drugs were mainly absorbed via syndecan-4-mediated macropinocytosis, regardless of animal species. Drug concentrations in the brain assessed in mice and monkeys and those in the cerebral spinal fluids (CSFs) assessed in monkeys indicated that drugs would be delivered from the systemic circulation to the central nervous system by crossing the blood-brain and the blood-CSF barriers under coadministration with the hyaluronic acid derivative. In line with our original hypothesis, this new set of data supported that our oligoarginine-linked hyaluronic acid would locally perform on the mucosal surface and enhance the membrane permeation of drugs under its colocalization.

Mucosal absorption of antibody drugs enhanced by cell-penetrating peptides anchored to a platform of polysaccharides

Our previous studies demonstrated that L-octaarginine grafted onto hyaluronic acid via a tetraglycine spacer significantly enhanced intranasal absorption of protein drugs with a molecular weight (Mw) of 22 kDa or less. The present study focused on its potential as an absorption enhancer for antibody drugs with a larger Mw and the enhancement mechanism. When ranibizumab (48 kDa) alone was intranasally administered in mice, its absolute bioavailability was 0.67% on average. The mean bioavailability elevated to 6.2% under coadministration with tetraglycine-L-octaarginine-linked hyaluronic acid. A similar result was observed under substitution of ranibizumab with certolizumab pegol (91 kDa), although bioavailability itself decreased with the Mw increase, irrespective of coadministration with the hyaluronic acid derivative. Rat experiments also revealed that coadministration with the polysaccharide derivative resulted in significant enhancement of intranasal absorption of trastuzumab (148 kDa). In vitro studies using gene-knocked down cells indicated that syndecan-4-induced macropinocytosis played a crucial role on acceleration of antibody uptake into epithelial cells on the nasal mucosa, irrespective of their Mw. It appeared that neither clathrin heavy chain nor caveolin-1 involved in cellular uptake of antibodies. Tetraglycine-L-octaarginine-linked hyaluronic acid was concluded to be a promising delivery tool that possessed universal absorption-enhancing abilities independent to Mw of biologics.

Overcoming the cellular barriers and beyond: Recent progress on cell penetrating peptide modified nanomedicine in combating physiological and pathological barriers

The complex physiological and pathological conditions form barriers against efficient drug delivery. Cell penetrating peptides (CPPs), a class of short peptides which translocate drugs across cell membranes with various mechanisms, provide feasible solutions for efficient delivery of biologically active agents to circumvent biological barriers. After years of development, the function of CPPs is beyond cell penetrating. Multifunctional CPPs with bioactivity or active targeting capacity have been designed and successfully utilized in delivery of various cargoes against tumor, myocardial ischemia, ocular posterior segment disorders, etc. In this review, we summarize recent progress in CPP-functionalized nano-drug delivery systems to overcome the physiological and pathological barriers for the applications in cardiology, ophtalmology, mucus, neurology and cancer, etc. We also highlight the prospect of clinical translation of CPP-functionalized drug delivery systems in these areas.

Evaluation of a D-Octaarginine-linked polymer as a transfection tool for transient and stable transgene expression in human and murine cell lines

Poly(N-vinylacetamide-co-acrylic acid) coupled with d-octaarginine (VP-R8) promotes the cellular uptake of peptides/proteins in vitro; however, details of the transfection efficacy of VP-R8, such as the cell types possessing high gene transfer, are not known. Herein, we compared the ability of VP-R8 to induce the cellular uptake of plasmid DNA in mouse and human cell lines from different tissues and organs. A green fluorescent protein (GFP)-expression plasmid was used as model genetic material, and fluorescence as an indicator of uptake and plasmid-derived protein expression. Three mouse and three human cell lines were incubated with a mixture of plasmid and VP-R8, and fluorescence analysis were performed two days after transfection. To confirm stable transgene expression, we performed drug selection three days after transfection. A commercially available polymer-based DNA transfection reagent (PTR) was used as the transfection control and standard for comparing transgene expression efficiency. In the case of transient transgene expression, slight-to-moderate GFP expression was observed in all cell lines transfected with plasmid via VP-R8; however, transfection efficiency was lower using the PTR for gene delivery. In the case of stable transgene expression, VP-R8 promoted drug-resistance acquisition more efficiently than the PTR did. Cells that developed drug resistance after VP-R8‒mediated gene transfection expressed GFP more efficiently than cells that developed drug resistance after transfection with the PTR. Thus, VP-R8 shows potential as an in vitro or ex vivo nonviral transfection tool for generating cell lines with stable transgene expression.

Core-shell lipoplexes inducing active macropinocytosis promote intranasal delivery of c-Myc siRNA for treatment of glioblastoma

Glioblastoma is the most common and aggressive primary brain tumor, whose malignancy is closely correlated with elevated proto-oncogene c-myc. Intranasal administration emerges as a potential approach to deliver gene into the brain and interfere c-Myc expression. However, powerful permeability in nasal mucosa, selective delivery to glioma and avoidance of premature release during remote transport are imperative to ensure the therapeutic effectiveness. To address the above concerns, herein we constructed a lipoplex based on pre-compression of c-Myc-targeting siRNA (sic-Myc) by octaarginine and subsequent encapsulation by liposome modified with a selected peptide derived from penetratin, named 89WP. It was found that the lipoplex exhibited a stable core-shell structure and could be preferentially internalized along with cell debris by glioma cells via active macropinocytosis. Through this cellular uptake pathway, the lipoplex avoided being entrapped by lysosome and released siRNA in cytoplasm within 4 h, inducing substantial downregulation of c-Myc mRNA and protein expression of glioma cells. Furthermore, due to significantly enhanced permeability in tumor spheroids and nasal mucosa, the lipoplex was competent to deliver more siRNA to orthotopic glioma after intranasal administration, and therefore prolonged the survival time of glioma-bearing mice by inducing apoptosis. STATEMENT OF SIGNIFICANCE: In the present work, a lipoplex was designed to address the unmet demands on intranasal siRNA delivery to the brain for treatment of glioma. First, a powerful peptide was selected to enable the lipoplex to penetrate nasal mucosa. Second, we found the lipoplex could be selectively internalized along with cell debris by glioma cells via active macropinocytosis, and recorded the entire process. This cellular uptake pathway not only prevented the lipoplex being entrapped by lysosome, but also increased distribution of the lipoplex in orthotopic glioma. Third, this lipoplex provided additional protection for siRNA to avoid premature release during transport from nasal to brain. Overall, this lipoplex improved the gene delivery efficiency of intranasal administration and was promising in the perspective of selectively silencing disease-related genes in intracranial tumor.

CPP Applications in Immune Modulation and Disease Therapy

About 30 years ago, the discovery of CPP improved the therapeutic approach to treat diseases and extended the range of potential targets to intracellular molecules. There are potential drug candidates for FDA approval based on active studies in basic research, preclinical, and clinical trials. Various attempts by CPP application to control the diseases such as allergy, autoimmunity, cancer, and infection demonstrated a strategy to make a new drug pipeline for successful discovery of a biologic drug for immune modulation. However, there are still no CPP-based drug candidates for immune-related diseases in the clinical stage. To control immune responses successfully, not only increasing delivery efficiency of CPPs but also selecting potential target cells and cargoes could be important issues. In particular, as it becomes possible to control intracellular targets, efforts to find various novel potential target are being attempted. In this chapter, we focused on CPP-based approaches to treat diseases through modulation of immune responses and discussed for perspectives on future direction of the research for successful application of CPP technology to immune modulation and disease therapy in clinical trial.

Mechanism on antigen delivery under mucosal vaccination using cell-penetrating peptides immobilized at multiple points on polymeric platforms

We have developed an aggregate of D-octaarginine immobilized at multiple points on a co-polymer of N-vinylacetamide and acrylic acid. Previous studies revealed that immunoglobulin G and A were induced when mice were inoculated with influenza virus antigens under coadministration with the D-octaarginine-immobilized polymers as a mucosal vaccine adjuvant. Infection experiments demonstrated that mice vaccinated with a mixture of inactivated influenza viruses and the polymers were protected from infection with mouse-adapted infectious viruses. In the present study, we investigated the mechanism on antigen delivery under mucosal vaccination using the polymers. Two-hour retention of fluorescein-labeled ovalbumin (F-OVA) on the nasal mucosa was observed when applied with the polymers; nevertheless F-OVA was eliminated less than 10 min under polymer-free conditions. F-OVA mixed with the polymers was vigorously taken up into murine dendritic cells. Electrophoresis and dynamic light scattering analysis indicated that OVA interacted with the polymers. The uptake of F-OVA was hardly ever inhibited by the addition of an excess amount of intact OVA. The results suggested that viral antigens were accumulated on the mucosa and delivered into dendritic cells under basolateral membranes via dendrites extending to the mucosal surface and/or subsequent to their permeation through epithelial cells, when they were coadministered with D-octaarginine-immobilized polymers.

Evaluation of Cell-Penetrating Peptides as Mucosal Immune Enhancers for Nasal Vaccination

Cell-penetrating peptides (CPPs) have been evaluated as enhancers in drug delivery, their addition in medical formulations favors drug absorption allowing obtaining the pharmacological effect with lower doses. In vaccine formulations their inclusion has been also explored with interesting results. Currently mucosal vaccination constitutes a promising alternative with the main advantage of inducing both systemic and mucosal immune responses, which are crucial for control tumors and infections at mucosal tissues. In the present work the nasal immune-enhancing effect of four CPPs was evaluated in Balb/c mice. Animals were intranasally immunized with CPP and the recombinant hepatitis B surface protein (HBsAg) as model antigen. The antibody response in sera and mucosal tissue was measured by ELISA. The IFN-γ secretion response at spleen was also evaluated by ELISPOT and ELISA. Among the CPPs studied one novel peptide stand out by its ability to potentiate the humoral and cellular immune response against the co-administered antigen. Considering that the use of mucosal routes is a promising strategy in vaccination, which are gaining special relevance nowadays in the development of novel candidates against SARS-CoV-2 and other potential emerging respiratory virus, the searching and development of safe mucosal adjuvants constitute a current need.

Cell-penetrating Peptide-mediated Nanovaccine Delivery

Vaccination with small antigens, such as proteins, peptides, or nucleic acids, is used to activate the immune system and trigger the protective immune responses against a pathogen. Currently, nanovaccines are undergoing development instead of conventional vaccines. The size of nanovaccines is in the range of 10-500 nm, which enables them to be readily taken up by cells and exhibit improved safety profiles. However, low-level immune responses, as the removal of redundant pathogens, trigger counter-effective activation of the immune system invalidly and present a challenging obstacle to antigen recognition and its uptake via antigen-presenting cells (APCs). In addition, toxicity can be substantial. To overcome these problems, a variety of cell-penetrating peptide (CPP)-mediated vaccine delivery systems based on nanotechnology have been proposed, most of which are designed to improve the stability of antigens in vivo and their delivery into immune cells. CPPs are particularly attractive components of antigen delivery. Thus, the unique translocation property of CPPs ensures that they remain an attractive carrier with the capacity to deliver cargo in an efficient manner for the application of drugs, gene transfer, protein, and DNA/RNA vaccination delivery. CPP-mediated nanovaccines can enhance antigen uptake, processing, and presentation by APCs, which are the fundamental steps in initiating an immune response. This review describes the different types of CPP-based nanovaccines delivery strategies.

Cross-Protective Abilities of Hyaluronic Acid Modified with Tetraglycine-l-octaarginine as a Mucosal Adjuvant against Infection with Heterologous Influenza Viruses

Mucosal vaccination, which secretion of immunoglobulin A (IgA) on the mucosa is accompanied by induction of immunoglobulin G (IgG) in the blood, is one of the most effective ways to circumvent influenza epidemics caused by incorrect prediction of epidemic viral strains or viral mutation. Secreted IgA is expected to prevent hosts from being infected with heterologous viruses because this antibody cross-reacts to strains other than those used for immunization. Our previous mouse experiments revealed that intranasal IgA with cross-reactivity was induced through nasal inoculation with inactivated whole viral particles of the H1N1 A/New Caledonia/20/99 IVR116 (NCL) strain in the presence of hyaluronic acid modified with tetraglycine-l-octaarginine. In the present study, heterologous influenza virus challenge was performed to validate a potential of the hyaluronic acid derivative as a mucosal adjuvant with cross-protective abilities. Serious weight loss was observed when mice were nasally inoculated with inactivated NCL viruses alone and subsequently exposed to mouse-adapted infectious viruses of the H1N1 A/Puerto Rico/8/34 (PR8) strain. The symptom associated with virus infection was hardly ever observed for mice inoculated with a mixture of the viral antigens and tetraglycine-l-octaarginine-linked hyaluronic acid, presumably due to high induction of IgG and IgA capable of cross-reacting to PR8 viruses. Less proliferation of PR8 viruses in those mice was also supported by an insignificant elevation of antibody levels through virus exposure. Our polysaccharide derivative enabled hosts to acquire adaptive immunity with cross-protective abilities against heterologous virus infection.

Innovative Mucosal Vaccine Formulations Against Influenza A Virus Infections

Despite efforts made to develop efficient preventive strategies, infections with influenza A viruses (IAV) continue to cause serious clinical and economic problems. Current licensed human vaccines are mainly inactivated whole virus particles or split-virion administered via the parenteral route. These vaccines provide incomplete protection against IAV in high-risk groups and are poorly/not effective against the constant antigenic drift/shift occurring in circulating strains. Advances in mucosal vaccinology and in the understanding of the protective anti-influenza immune mechanisms suggest that intranasal immunization is a promising strategy to fight against IAV. To date, human mucosal anti-influenza vaccines consist of live attenuated strains administered intranasally, which elicit higher local humoral and cellular immune responses than conventional parenteral vaccines. However, because of inconsistent protective efficacy and safety concerns regarding the use of live viral strains, new vaccine candidates are urgently needed. To prime and induce potent and long-lived protective immune responses, mucosal vaccine formulations need to ensure the immunoavailability and the immunostimulating capacity of the vaccine antigen(s) at the mucosal surfaces, while being minimally reactogenic/toxic. The purpose of this review is to compile innovative delivery/adjuvant systems tested for intranasal administration of inactivated influenza vaccines, including micro/nanosized particulate carriers such as lipid-based particles, virus-like particles and polymers associated or not with immunopotentiatory molecules including microorganism-derived toxins, Toll-like receptor ligands and cytokines. The capacity of these vaccines to trigger specific mucosal and systemic humoral and cellular responses against IAV and their (cross)-protective potential are considered.

Biodegradable Hyaluronic Acid Modified with Tetraglycine-l-octaarginine as a Safe Adjuvant for Mucosal Vaccination

We have been investigating the potential use of polymers modified with cell-penetrating peptides as an adjuvant for mucosal vaccination and have already developed nondegradable poly( N-vinylacetamide- co-acrylic acid) (PNVA- co-AA) with which d-octaarginine, a typical cell-penetrating peptide, was grafted. Our previous murine infection experiments demonstrated that immunoglobulin G (IgG) and immunoglobulin A (IgA) were induced in systemic circulation and secreted on nasal mucosa, respectively, through 4-time nasal inoculations with a mixture of influenza viral antigens and d-octaarginine-linked PNVA- co-AA at 7-day intervals, and that immunized mice were perfectly protected from homologous virus infection. In the present study, we designed novel biodegradable polymers bearing cell-penetrating peptides from a perspective of clinical application. Hyaluronic acid whose glucuronic acid was modified with tetraglycine-l-octaarginine at a monosaccharide unit ratio of 30% was successfully developed. The hyaluronic acid derivative exhibited adjuvant activities identical to PNVA- co-AA bearing either d-octaarginine or tetraglycine-d-octaarginine under the above-mentioned inoculation schedule. We further found that there was no difference in humoral immunity between the 4-time inoculations at 7-day intervals and the 2-time inoculations at 28-day intervals. Intranasal IgA induced through the latter schedule with a smaller number of inoculations, which is clinically practical, exhibited cross-reactivity beyond the subtype of viral strains. In vitro toxicity studies demonstrated that the hyaluronic acid derivative was much less toxic than the corresponding PNVA- co-AA derivatives, and that both the polymers and their metabolites did not exhibit genotoxicity. Our results suggested that tetraglycine-l-octaarginine-linked hyaluronic acid would be a clinically valuable and safe adjuvant for mucosal vaccination.

Cell-penetrating Peptides: Efficient Vectors for Vaccine Delivery

Subunit vaccines are composed of pathogen fragments that, on their own, are generally poorly immunogenic. Therefore, the incorporation of an immunostimulating agent, e.g. adjuvant, into vaccine formulation is required. However, there are only a limited number of licenced adjuvants and their immunostimulating ability is often limited, while their toxicity can be substantial. To overcome these problems, a variety of vaccine delivery systems have been proposed. Most of them are designed to improve the stability of antigen in vivo and its delivery into immune cells. Cell-penetrating peptides (CPPs) are especially attractive component of antigen delivery systems as they have been widely used to enhance drug transport into the cells. Fusing or co-delivery of antigen with CPPs can enhance antigen uptake, processing and presentation by antigen presenting cells (APCs), which are the fundamental steps in initiating an immune response. This review describes the different mechanisms of CPP intercellular uptake and various CPP-based vaccine delivery strategies.

Biocompatible Polymers Modified with d-Octaarginine as an Absorption Enhancer for Nasal Peptide Delivery

Peptide and protein drugs, which are categorized as biologics, exhibit poor membrane permeability. This pharmacokinetic disadvantage has largely restricted the development of noninvasive dosage forms of biologics that deliver into systemic circulation. We have been investigating the potential use of cell-penetrating peptide-linked polymers as a novel absorption enhancer to overcome this challenge. Since our previous study revealed that biocompatible poly( N-vinylacetamide- co-acrylic acid) modified with d-octaarginine, a typical cell-penetrating peptide, enhanced in vitro permeation of biomolecules such as plasmid DNA and bovine serum albumin through cell membranes, the present study evaluated whether the polymers enhanced in vivo absorption of biologics applied on the mucosa. Mouse experiments demonstrated that d-octaarginine-linked polymers drastically enhanced nasal absorption of exendin-4, whose injection is clinically used. The mean bioavailability was 20% relative to subcutaneous administration, even though it fell short of 1% when exendin-4 alone was administered nasally. The absorption-enhancing function of the polymers was superior to that of sodium caprate and sodium N-(8-(2-hydroxybenzoyl)amino) caprylate, which have been used for humans as an absorption enhancer. In vitro experiments using several biologics with different characteristics revealed that biologics interacted with d-octaarginine-linked polymers and were taken up into cells when incubated with the polymers. The interaction and cellular uptake were enhanced as molecular weights of the biologics increased; however, their charge-dependent in vitro performance was not clearly observed. The current data suggested that biologics formulated with our polymers became an alternative to their conventional invasive parenteral formulations.

Potential of Translationally Controlled Tumor Protein-Derived Protein Transduction Domains as Antigen Carriers for Nasal Vaccine Delivery

Nasal vaccination offers a promising alternative to intramuscular (i.m.) vaccination because it can induce both mucosal and systemic immunity. However, its major drawback is poor absorption of large antigens in the nasal epithelium. Protein transduction domains (PTDs), also called cell-penetrating peptides, have been proposed as vehicles for nasal delivery of therapeutic peptides and proteins. Here, we evaluated the potential of a mutant PTD derived from translationally controlled tumor protein (designated TCTP-PTD 13) as an antigen carrier for nasal vaccines. We first compared the l- and d-forms of TCTP-PTD 13 isomers (l- or d-TCTP-PTD 13) as antigen carriers. Studies in mice demonstrated that nasally administered mixtures of the model antigen ovalbumin (OVA) and d-TCTP-PTD 13 induced higher plasma IgG titers and secretory IgA levels in nasal washes than nasally administered OVA alone, OVA/l-TCTP-PTD 13, or i.m.-injected OVA. Plasma IgG subclass responses (IgG1 and IgG2a) of mice nasally administered OVA/d-TCTP-PTD 13 showed that the predominant IgG subclass was IgG1, indicating a Th2-biased immune response. We also used synthetic CpG oligonucleotides (CpG) as a Th1 immune response-inducing adjuvant. Nasally administered CpG plus OVA/d-TCTP-PTD 13 was superior in eliciting systemic and mucosal immune responses compared to those induced by nasally administered OVA/d-TCTP-PTD 13. Furthermore, the OVA/CpG/d-TCTP-PTD 13 combination skewed IgG1 and IgG2a profiles of humoral immune responses toward a Th1 profile. These findings suggest that TCTP-derived PTD is a suitable vehicle to efficiently carry antigens and to induce more powerful antigen-specific immune responses and a more balanced Th1/Th2 response when combined with a DNA adjuvant.

Engineering nanoparticles to overcome barriers to immunotherapy

Advances in immunotherapy have led to the development of a variety of promising therapeutics, including small molecules, proteins and peptides, monoclonal antibodies, and cellular therapies. Despite this wealth of new therapeutics, the efficacy of immunotherapy has been limited by challenges in targeted delivery and controlled release, that is, spatial and temporal control on delivery. Particulate carriers, especially nanoparticles have been widely studied in drug delivery and vaccine research and are being increasingly investigated as vehicles to deliver immunotherapies. Nanoparticle-mediated drug delivery could provide several benefits, including control of biodistribution and transport kinetics, the potential for site-specific targeting, immunogenicity, tracking capability using medical imaging, and multitherapeutic loading. There are also a unique set of challenges, which include nonspecific uptake by phagocytic cells, off-target biodistribution, permeation through tissue (transport limitation), nonspecific immune-activation, and poor control over intracellular localization. This review highlights the importance of understanding the relationship between a nanoparticle's size, shape, charge, ligand density and elasticity to its vascular transport, biodistribution, cellular internalization, and immunogenicity. For the design of an effective immunotherapy, we highlight the importance of selecting a nanoparticle's physical characteristics (e.g., size, shape, elasticity) and its surface functionalization (e.g., chemical or polymer modifications, targeting or tissue-penetrating peptides) with consideration of its reactivity to the targeted microenvironment (e.g., targeted cell types, use of stimuli-sensitive biomaterials, immunogenicity). Applications of this rational nanoparticle design process in vaccine development and cancer immunotherapy are discussed.

Cell Type Preference of a Novel Human Derived Cell-Permeable Peptide dNP2 and TAT in Murine Splenic Immune Cells

Cell-permeable peptides (CPPs) have been widely studied as an attractive drug delivery system to deliver therapeutic macromolecules such as DNA, RNA, and protein into cells. However, its clinical application is still limited and controversial due to the lack of a complete understanding of delivery efficiency in target cells. Previously we identified and characterized the novel and superior CPP, named dNP2, and here we comparatively analyzed intracellular delivery efficiency of dNP2 and TAT in various immune cells of mouse spleen to demonstrate their cell type preference. dNP2- or TAT-conjugated fluorescent proteins were most efficiently taken up by phagocytic cells such as dendritic cells and macrophages while little protein uptake was seen by lymphocytes including T cells, B cells, and NK cells. Interestingly CD8⁺ lymphoid dendritic cells and CD62L^loCD44^hi memory like T cell subsets showed significantly better uptake efficiency in vitro and in vivo relative to other dendritic cells or T cells, respectively. In addition, activated macrophages, T cells, and B cells took up the proteins more efficiently relative to when in the resting state. Importantly, only dNP2, not TAT, shows significant intracellular protein delivery efficiency in vivo. Collectively, this study provides important information regarding heterogeneous intracellular delivery efficiency of CPPs such as dNP2 and TAT with cell type preference in the spleen needed for its application in phagocytic cells or activated immune cells.

Potential of D-Octaarginine-Linked Polymers as an in Vitro Transfection Tool for Biomolecules

We have been investigating the potential use of cell-penetrating peptide-linked polymers as a novel penetration enhancer. Since previous in vivo studies demonstrated that poly(N-vinylacetamide-co-acrylic acid) bearing D-octaarginine, a typical cell-penetrating peptide, enhanced membrane permeation of biomolecules, its potential as an in vitro transfection tool was evaluated in this study. A plasmid DNA encoding green fluorescent protein (pGFP-C1), β-galactosidase, and bovine serum albumin (BSA) were used as model biomolecules. Anionic pGFP-C1 interacted electrostatically with cationic d-octaarginine-linked polymers. When the ratio of mass concentration of polymers to that of pGFP-C1 reached 2.5, complexes whose size and zeta potential were approximately 200 nm and 15 mV, respectively, were obtained. GFP expression was observed in cells incubated with complexes prepared under conditions in which the polymer/pDNA concentration ratio exceeded 2.5. The expression level elevated with an increase in the concentration ratio, but physicochemical properties of the complexes remained unchanged. Results suggested that free polymers contributed to pGFP-C1 internalization. Another cell study demonstrated that β-galactosidase premixed with polymers was taken up into cells in its active tetrameric form. Similar electrostatic interaction-driven complex formation was observed for BSA charged negatively in neutral solution. However, it appeared that the internalization processes of BSA differed from those of pGFP-C1. A mass concentration-dependent increase in internalized BSA was observed, irrespective of the polymer/protein concentration ratio. Due to frail interactions, polymers that were released from the complexes and subsequently immobilized on cell membranes might also contribute to membrane permeation of BSA.

Cross-reactivity of immunoglobulin A secreted on the nasal mucosa in mice nasally inoculated with inactivated H1N1 influenza A viruses in the presence of D-octaarginine-linked polymers

We evaluated cross-reactivity of immunoglobulin A (IgA) secreted on the nasal mucosa in mice that were nasally inoculated 4 times with a mixture of inactivated H1N1 influenza A viruses and poly(N-vinylacetamide-co-acrylic acid) (PNVA-co-AA) bearing d-octaarginine at 7-day intervals. Three viral strains (A/Puerto Rico/8/34, A/New Caledonia/20/99 IVR116, and A/Solomon Islands/03/2006) and D-octaarginine-linked polymers with different molecular weights were used as antigens and their carriers, respectively. Secretion of intranasal IgA was barely observed when the inactivated virus alone was administered. The polymer induced the production of intranasal IgA specific to the inoculated viruses, irrespective of the viral strain and molecular weight of the polymer. The respective antibodies cross-reacted to recombinant hemagglutinin proteins of not only the viral strain used for immunization but also other H1N1 strains, including A/Puerto Rico/8/34 strain whose hemagglutinin proteins are diverse from those of other strains. Mice with high reactivity of IgA to the inoculated viruses tended to acquire clear cross-reactivity to other viral strains. Notably, IgA induced by inactivated H1N1 A/New Caledonia/20/99 IVR116 strain with the strongest immunogenicity between 3 antigens in the presence of the polymer cross-reacted to recombinant hemagglutinin proteins of the A/Brisbane/10/2007 and A/Viet Nam/1194/2004 strains, which are categorized into H3N2 and H5N1, respectively. Our polymer is a potential candidate for an efficient antigen carrier that induces mucosal IgA having cross-reactivity to antigenically drifted variants, irrespective of the subtype of viral strains.