Next-generation nanovaccine induces durable immunity and protects against SARS-CoV-2

While first generation SARS-CoV-2 vaccines were effective in slowing the spread and severity of disease during the COVID-19 pandemic, there is a need for vaccines capable of inducing durable and broad immunity against emerging variants of concern. Nanoparticle-based vaccines (i.e., "nanovaccines") composed of polyanhydride nanoparticles and pentablock copolymer micelles have previously been shown to protect against respiratory pathogens, including influenza A virus, respiratory syncytial virus, and Yersinia pestis. In this work, a nanovaccine containing SARS-CoV-2 spike and nucleocapsid antigens was designed and optimized. The optimized nanovaccine induced long-lived systemic IgG antibody responses against wild-type SARS-CoV-2 virus. In addition, the nanovaccine induced antibody responses capable of neutralization and cross-reactivity to multiple SARS-CoV-2 variants (including B.1.1.529) and antigen-specific CD4+ and CD8+ T cell responses. Finally, the nanovaccine protected mice against a lethal SARS-CoV-2 challenge, setting the stage for advancing particle-based SARS-CoV-2 nanovaccines. STATEMENT OF SIGNIFICANCE: First-generation SARS-CoV-2 vaccines were effective in slowing the spread and limiting the severity of COVID-19. However, current vaccines target only one antigen of the virus (i.e., spike protein) and focus on the generation of neutralizing antibodies, which may be less effective against new, circulating strains. In this work, we demonstrated the ability of a novel nanovaccine platform, based on polyanhydride nanoparticles and pentablock copolymer micelles, to generate durable and broad immunity against SARS-CoV-2. These nanovaccines induced long-lasting (> 62 weeks) serum antibody responses which neutralized binding to ACE2 receptors and were cross-reactive to multiple SARS-CoV-2 variants. Additionally, mice immunized with the SARS-CoV-2 nanovaccine showed a significant increase of antigen-specific T cell responses in the draining lymph nodes and spleens. Together, these nanovaccine-induced immune responses contributed to the protection of mice against a lethal challenge of live SARS-CoV-2 virus, indicating that this nanovaccine platform is a promising next-generation SARS-CoV-2 vaccine.

Nanovaccines: A game changing approach in the fight against infectious diseases

The field of nanotechnology has revolutionised global attempts to prevent, treat, and eradicate infectious diseases in the foreseen future. Nanovaccines have proven to be a valuable pawn in this novel technology. Nanovaccines are made up of nanoparticles that are associated with or prepared with components that can stimulate the host's immune system. In addition to their delivery capabilities, the nanocarriers have been demonstrated to possess intrinsic adjuvant properties, working as immune cell stimulators. Thus, nanovaccines have the potential to promote rapid as well as long-lasting humoral and cellular immunity. The nanovaccines have several possible benefits, including site-specific antigen delivery, increased antigen bioavailability, and a diminished adverse effect profile. To avail these benefits, several nanoparticle-based vaccines are being developed, including virus-like particles, liposomes, polymeric nanoparticles, nanogels, lipid nanoparticles, emulsion vaccines, exomes, and inorganic nanoparticles. Inspired by their distinctive properties, researchers are working on the development of nanovaccines for a variety of applications, such as cancer immunotherapy and infectious diseases. Although a few challenges still need to be overcome, such as modulation of the nanoparticle pharmacokinetics to avoid rapid elimination from the bloodstream by the reticuloendothelial system, The future prospects of this technology are also assuring, with multiple options such as personalised vaccines, needle-free formulations, and combination nanovaccines with several promising candidates.

Broad and Durable Humoral Responses Following Single Hydrogel Immunization of SARS-CoV-2 Subunit Vaccine

Most vaccines require several immunizations to induce robust immunity, and indeed, most SARS-CoV-2 vaccines require an initial two-shot regimen followed by several boosters to maintain efficacy. Such a complex series of immunizations unfortunately increases the cost and complexity of populations-scale vaccination and reduces overall compliance and vaccination rate. In a rapidly evolving pandemic affected by the spread of immune-escaping variants, there is an urgent need to develop vaccines capable of providing robust and durable immunity. In this work, a single immunization SARS-CoV-2 subunit vaccine is developed that can rapidly generate potent, broad, and durable humoral immunity. Injectable polymer-nanoparticle (PNP) hydrogels are leveraged as a depot technology for the sustained delivery of a nanoparticle antigen (RND-NP) displaying multiple copies of the SARS-CoV-2 receptor-binding domain (RBD) and potent adjuvants including CpG and 3M-052. Compared to a clinically relevant prime-boost regimen with soluble vaccines formulated with CpG/alum or 3M-052/alum adjuvants, PNP hydrogel vaccines more rapidly generated higher, broader, and more durable antibody responses. Additionally, these single-immunization hydrogel-based vaccines elicit potent and consistent neutralizing responses. Overall, it is shown that PNP hydrogels elicit improved anti-COVID immune responses with only a single administration, demonstrating their potential as critical technologies to enhance overall pandemic readiness.

Synthesis and Optimization of Next-Generation Low-Molecular-Weight Pentablock Copolymer Nanoadjuvants

Polymeric nanomaterials such as Pluronic®-based pentablock copolymers offer important advantages over traditional vaccine adjuvants and have been increasingly investigated in an effort to develop more efficacious vaccines. Previous work with Pluronic® F127-based pentablock copolymers, functionalized with poly(diethyl aminoethyl methacrylate) (PDEAEM) blocks, demonstrated adjuvant capabilities through the antigen presentation and crosslinking of B cell receptors. In this work, we describe the synthesis and optimization of a new family of low-molecular-weight Pluronic®-based pentablock copolymer nanoadjuvants with high biocompatibility and improved adjuvanticity at low doses. We synthesized low-molecular-weight Pluronic® P123-based pentablock copolymers with PDEAEM blocks and investigated the relationship between polymer concentration, micellar size, and zeta potential, and measured the release kinetics of a model antigen, ovalbumin, from these nanomaterials. The Pluronic® P123-based pentablock copolymer nanoadjuvants showed higher biocompatibility than the first-generation Pluronic® F127-based pentablock copolymer nanoadjuvants. We assessed the adjuvant capabilities of the ovalbumin-containing Pluronic® P123-based pentablock copolymer-based nanovaccines in mice, and showed that animals immunized with these nanovaccines elicited high antibody titers, even when used at significantly reduced doses compared to Pluronic® F127-based pentablock copolymers. Collectively, these studies demonstrate the synthesis, self-assembly, biocompatibility, and adjuvant properties of a new family of low-molecular-weight Pluronic® P123-based pentablock copolymer nanomaterials, with the added benefits of more efficient renal clearance, high biocompatibility, and enhanced adjuvanticity at low polymer concentrations.

Current status of nano-vaccinology in veterinary medicine science

Vaccination programmes provide a safe, effective and cost-efficient strategy for maintaining population health. In veterinary medicine, vaccination not only reduces disease within animal populations but also serves to enhance public health by targeting zoonoses. Nevertheless, for many pathogens, an effective vaccine remains elusive. Recently, nanovaccines have proved to be successful for various infectious and non-infectious diseases of animals. These novel technologies, such as virus-like particles, self-assembling proteins, polymeric nanoparticles, liposomes and virosomes, offer great potential for solving many of the vaccine production challenges. Their benefits include low immunotoxicity, antigen stability, enhanced immunogenicity, flexibility sustained release and the ability to evoke both humoral and cellular immune responses. Nanovaccines are more efficient than traditional vaccines due to ease of control and plasticity in their physio-chemical properties. They use a highly targeted immunological approach which can provide strong and long-lasting immunity. This article reviews the currently available nanovaccine technology and considers its utility for both infectious diseases and non-infectious diseases such as auto-immunity and cancer. Future research opportunities and application challenges from bench to clinical usage are also discussed.

Novel nanoadjuvants balance immune activation with modest inflammation: implications for older adult vaccines

BACKGROUND

Age-associated impairments of immune response and inflammaging likely contribute to poor vaccine efficacy. An appropriate balance between activation of immune memory and inflammatory response may be more effective in vaccines for older adults; attempts to overcome reduced efficacy have included the addition of adjuvants or increased antigenic dose. Next generation vaccine formulations may also use biomaterials to both deliver and adjuvant vaccine antigens. In the context of aging, it is important to determine the degree to which new biomaterials may enhance antigen-presenting cell (APC) functions without inducing potent inflammatory responses of APCs or other immune cell types (e.g., T cells). However, the effect of newer biomaterials on these cell types from young and older adults remains unknown.

RESULTS

In this pilot study, cells from young and older adults were used to evaluate the effect of novel biomaterials such as polyanhydride nanoparticles (NP) and pentablock copolymer micelles (Mi) and cyclic dinucleotides (CDN; a STING agonist) on cytokine and chemokine secretion in comparison to standard immune activators such as lipopolysaccharide (LPS) and PMA/ionomycin. The NP treatment showed adjuvant-like activity with induction of inflammatory cytokines, growth factors, and select chemokines in peripheral blood mononuclear cells (PBMCs) of both young (n = 6) and older adults (n = 4), yet the degree of activation was generally less than LPS. Treatment with Mi or CDN resulted in minimal induction of cytokines and chemokine secretion with the exception of increased IFN-α and IL-12p70 by CDN. Age-related decreases were observed across multiple cytokines and chemokines, yet IFN-α, IL-12, and IL-7 production by NP or CDN stimulation was equal to or greater than in cells from younger adults. Consistent with these results in aged humans, a combination nanovaccine composed of NP, Mi, and CDN administered to aged mice resulted in a greater percentage of antigen-specific CD4+ T cells and greater effector memory cells in draining lymph nodes compared to an imiquimod-adjuvanted vaccine.

CONCLUSIONS

Overall, our novel biomaterials demonstrated a modest induction of cytokine secretion with a minimal inflammatory profile. These findings suggest a unique role for biomaterial nanoadjuvants in the development of next generation vaccines for older adults.

"Just right" combinations of adjuvants with nanoscale carriers activate aged dendritic cells without overt inflammation

BACKGROUND

The loss in age-related immunological markers, known as immunosenescence, is caused by a combination of factors, one of which is inflammaging. Inflammaging is associated with the continuous basal generation of proinflammatory cytokines. Studies have demonstrated that inflammaging reduces the effectiveness of vaccines. Strategies aimed at modifying baseline inflammation are being developed to improve vaccination responses in older adults. Dendritic cells have attracted attention as an age-specific target because of their significance in immunization as antigen presenting cells that stimulate T lymphocytes.

RESULTS

In this study, bone marrow derived dendritic cells (BMDCs) were generated from aged mice and used to investigate the effects of combinations of adjuvants, including Toll-like receptor, NOD2, and STING agonists with polyanhydride nanoparticles and pentablock copolymer micelles under in vitro conditions. Cellular stimulation was characterized via expression of costimulatory molecules, T cell-activating cytokines, proinflammatory cytokines, and chemokines. Our results indicate that multiple TLR agonists substantially increase costimulatory molecule expression and cytokines associated with T cell activation and inflammation in culture. In contrast, NOD2 and STING agonists had only a moderate effect on BMDC activation, while nanoparticles and micelles had no effect by themselves. However, when nanoparticles and micelles were combined with a TLR9 agonist, a reduction in the production of proinflammatory cytokines was observed while maintaining increased production of T cell activating cytokines and enhancing cell surface marker expression. Additionally, combining nanoparticles and micelles with a STING agonist resulted in a synergistic impact on the upregulation of costimulatory molecules and an increase in cytokine secretion from BMDCs linked with T cell activation without excessive secretion of proinflammatory cytokines.

CONCLUSIONS

These studies provide new insights into rational adjuvant selection for vaccines for older adults. Combining appropriate adjuvants with nanoparticles and micelles may lead to balanced immune activation characterized by low inflammation, setting the stage for designing next generation vaccines that can induce mucosal immunity in older adults.

Immunologically effective biomaterials-enhanced vaccines against infection of pathogenic microorganisms

Infectious diseases are severe public health events that threaten global health. Prophylactic vaccines have been considered as the most effective strategy to train the immune system to recognize and clear pathogenic infections. However, the existing vaccines against infectious diseases have several limitations, such as difficulties in mass manufacturing and storage, weak immunogenicity, and low efficiency of available adjuvants. Biomaterials, especially functional polymers, are expected to break through these bottlenecks based on the advantages of biocompatibility, degradability, controlled synthesis, easy modification, precise targeting, and immune modulation, which are excellent carriers and adjuvants of vaccines. This review mainly summarizes the application of immunologically effective polymers-enhanced vaccines against viruses- and bacteria-related infectious diseases and predicted their potential improvements.

Immunomodulation in age-related disorders and nanotechnology interventions

Recently, the aging population has increased exponentially around the globe bringing more challenges to improve quality of life in those populations while reducing the economic burden on healthcare systems. Aging is associated with changes in the immune system culminating in detrimental effects such as immune dysfunction, immunosenescence, and chronic inflammation. Age-related decline of immune functions is associated with various pathologies including cardiovascular, autoimmune, neurodegenerative, and infectious diseases to name a few. Conventional treatment addresses the onset of age-related diseases by early detection of risk factors, administration of vaccines as preventive care, immunomodulatory treatment, and other dietary supplements. However, these approaches often come with systemic side-effects, low bioavailability of therapeutic agents, and poor outcomes seen in the elderly. Recent innovations in nanotechnology have led to the development of novel biomaterials/nanomaterials, which explore targeted drug delivery and immunomodulatory interactions in vivo. Current nanotechnology-based immunomodulatory approaches that have the potential to be used as therapeutic interventions for some prominent age-related diseases are discussed here. Finally, we explore challenges and future aspects of nanotechnology in the treatments of age-related disorders to improve quality of life in the elderly. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Polyanhydride Chemistry

Polyanhydrides (PAs) are a class of synthetic biodegradable polymers employed as controlled drug delivery vehicles. They can be synthesized and scaled up from low-cost starting materials. The structure of PAs can be manipulated synthetically to meet desirable characteristics. PAs are biocompatible, biodegradable, and generate nontoxic metabolites upon degradation, which are easily eliminated from the body. The rate of water penetrating into the polyanhydride (PA) matrix is slower than the anhydride bond cleavage. This phenomenon sets PAs as "surface-eroding drug delivery carriers." Consequently, a variety of PA-based drug delivery carriers in the form of solid implants, pasty injectable formulations, microspheres, nanoparticles, etc. have been developed for the sustained release of small molecule drugs, and vaccines, peptide drugs, and nucleic acid-based active agents. The rate of drug delivery is often controlled by the polymer erosion rate, which is influenced by the polymer structure and composition, crystallinity, hydrophobicity, pH of the release medium, device size, configuration, etc. Owing to the above-mentioned interesting physicochemical and mechanical properties of PAs, the present review focuses on the advancements made in the domain of synthetic biodegradable biomedical PAs for therapeutic delivery applications. Various classes of PAs, their structures, their unique characteristics, their physicochemical and mechanical properties, and factors influencing surface erosion are discussed in detail. The review also summarizes various methods involved in the synthesis of PAs and their utility in the biomedical domain as drug, vaccine, and peptide delivery carriers in different formulations are reviewed.

IgD+ age-associated B cells are the progenitors of the main T-independent B cell response to infection that generates protective Ab and can be induced by an inactivated vaccine in the aged

Age-associated B cells (ABC) accumulate with age and are associated with autoimmunity and chronic infection. However, their contributions to acute infection in the aged and their developmental pathways are unclear. We find that the response against influenza A virus infection in aged mice is dominated by a Fas+ GL7- effector B cell population we call infection-induced ABC (iABC). Most iABC express IgM and include antibody-secreting cells in the spleen, lung, and bone marrow. We find that in response to influenza, IgD+ CD21- CD23- ABC are the precursors of iABC and become memory B cells. These IgD+ ABC develop in germ-free mice, so are independent of foreign antigen recognition. The response of ABC to influenza infection, resulting in iABC, is T cell independent and requires both extrinsic TLR7 and TLR9 signals. In response to influenza infection, IgD+ ABC can induce a faster recovery of weight and higher total anti-influenza IgG and IgM titers that can neutralize virus. Immunization with whole inactivated virus also generates iABC in aged mice. Thus, in unimmunized aged mice, whose other B and T cell responses have waned, IgD+ ABC are likely the naive B cells with the potential to become Ab-secreting cells and to provide protection from infection in the aged.

Vaccines platforms and COVID-19: what you need to know

BACKGROUND

The novel SARS-CoV-2, responsible for the COVID-19 pandemic, is the third zoonotic coronavirus since the beginning of the 21 first century, and it has taken more than 6 million human lives because of the lack of immunity causing global economic losses. Consequently, developing a vaccine against the virus represents the fastest way to finish the threat and regain some "normality."

OBJECTIVE

Here, we provide information about the main features of the most important vaccine platforms, some of them already approved, to clear common doubts fostered by widespread misinformation and to reassure the public of the safety of the vaccination process and the different alternatives presented.

METHODS

Articles published in open access databases until January 2022 were identified using the search terms "SARS-CoV-2," "COVID-19," "Coronavirus," "COVID-19 Vaccines," "Pandemic," COVID-19, and LMICs or their combinations.

DISCUSSION

Traditional first-generation vaccine platforms, such as whole virus vaccines (live attenuated and inactivated virus vaccines), as well as second-generation vaccines, like protein-based vaccines (subunit and viral vector vaccines), and third-generation vaccines, such as nanoparticle and genetic vaccines (mRNA vaccines), are described.

CONCLUSIONS

SARS-CoV-2 sequence information obtained in a record time provided the basis for the fast development of a COVID-19 vaccine. The adaptability characteristic of the new generation of vaccines is changing our capability to react to emerging threats to future pandemics. Nevertheless, the slow and unfair distribution of vaccines to low- and middle-income countries and the spread of misinformation are a menace to global health since the unvaccinated will increase the chances for resurgences and the surge of new variants that can escape the current vaccines.

Structural Stability and Antigenicity of Universal Equine H3N8 Hemagglutinin Trimer upon Release from Polyanhydride Nanoparticles and Pentablock Copolymer Hydrogels

Seasonal influenza A virus infections present substantial costs to both health and economic resources each year. Current seasonal influenza vaccines provide suboptimal protection and require annual reformulation to match circulating strains. In this work, a recombinant equine H3N8 hemagglutinin trimer (rH3₃) known to generate cross-protective antibodies and protect animals against sublethal, heterologous virus challenge was used as a candidate vaccine antigen. Nanoadjuvants such as polyanhydride nanoparticles and pentablock copolymer hydrogels have been shown to be effective adjuvants, inducing both rapid and long-lived protective immunity against influenza A virus. In this work, polyanhydride nanoparticles and pentablock copolymer hydrogels were used to provide sustained release of the novel rH3₃ while also facilitating the retention of its structure and antigenicity. These studies lay the groundwork for the development of a novel universal influenza A virus nanovaccine by combining the equine H3N8 rH3₃ and polymeric nanoadjuvant platforms.

The Fate of Sialic Acid and PEG Modified Epirubicin Liposomes in Aged versus Young Cells and Tumor Mice Models

In preclinical studies of young mice, nanoparticles showed excellent anti-tumor therapeutic effects by harnessing Peripheral Blood Monocytes (PBMs) and evading the immune system. However, the changes of age will inevitably affect PBMs and the immune system, and there is a serious lack of relevant research. Sialic acid (SA)-octadecylamine (ODA) was synthesized, and SA- or polyethylene glycol (PEG)-modified epirubicin (EPI) liposomes (EPI-SL and EPI-PL, respectively) were prepared to explore differences in antitumor treatment using 8-month-old and 8-week-old Kunming mice. Based on presented data, 8-month-old mice had more PBMs in peripheral blood than 8-week-old mice, and age differences resulted in different anti-tumor treatment effects following EPI-SL and EPI-PL treatment. Following EPI-PL administration, the tumor volume was significantly smaller in 8-week-old mice than in 8-month-old mice (* p < 0.05). Eight-month-old mice treated with EPI-SL (8M-SL) presented no damage to healthy tissue, with a 100% survival rate, and 50% mice in 8M-SL showed ‘shedding’ of tumor tissues from the growth site. Accordingly, 8-month-old mice treated with EPI-SL achieved the best therapeutic effect at different ages and with different liposomes. EPI-SL could improve the antitumor effect of 8-week-old and 8-month-old mice.

Nanodelivery of STING agonists against cancer and infectious diseases

Vaccination is a modality that has been widely explored for the treatment of various diseases. To increase the potency of vaccine formulations, immunostimulatory adjuvants have been regularly exploited, and the stimulator of interferon genes (STING) signaling pathway has recently emerged as a remarkable therapeutic target. STING is an endogenous protein on the endoplasmic reticulum that is a downstream sensor to cytosolic DNA. Upon activation, STING initiates a series of intracellular signaling cascades that ultimately generate potent type I interferon-mediated immune responses. Both natural and synthetic agonists have been used to stimulate the STING pathway, but they are usually administered locally due to low bioavailability, instability, and difficulty in bypassing the plasma membrane. With excellent pharmacokinetic profiles and versatility, nanocarriers can address many of these challenges and broaden the application of STING vaccines. Along these lines, STING-inducing nanovaccines are being developed to address a wide range of diseases. In this review, we discuss the recent advances in STING nanovaccines for anticancer, antiviral, and antibacterial applications.

Nanovaccines against Animal Pathogens: The Latest Findings

Nowadays, safe and efficacious vaccines represent powerful and cost-effective tools for global health and economic growth. In the veterinary field, these are undoubtedly key tools for improving productivity and fighting zoonoses. However, cases of persistent infections, rapidly evolving pathogens having high variability or emerging/re-emerging pathogens for which no effective vaccines have been developed point out the continuing need for new vaccine alternatives to control outbreaks. Most licensed vaccines have been successfully used for many years now; however, they have intrinsic limitations, such as variable efficacy, adverse effects, and some shortcomings. More effective adjuvants and novel delivery systems may foster real vaccine effectiveness and timely implementation. Emerging vaccine technologies involving nanoparticles such as self-assembling proteins, virus-like particles, liposomes, virosomes, and polymeric nanoparticles offer novel, safe, and high-potential approaches to address many vaccine development-related challenges. Nanotechnology is accelerating the evolution of vaccines because nanomaterials having encapsulation ability and very advantageous properties due to their size and surface area serve as effective vehicles for antigen delivery and immunostimulatory agents. This review discusses the requirements for an effective, broad-coverage-elicited immune response, the main nanoplatforms for producing it, and the latest nanovaccine applications for fighting animal pathogens.

Biomedical Applications of Antiviral Nanohybrid Materials Relating to the COVID-19 Pandemic and Other Viral Crises

The COVID-19 pandemic has driven a global research to uncover novel, effective therapeutical and diagnosis approaches. In addition, control of spread of infection has been targeted through development of preventive tools and measures. In this regard, nanomaterials, particularly, those combining two or even several constituting materials possessing dissimilar physicochemical (or even biological) properties, i.e., nanohybrid materials play a significant role. Nanoparticulate nanohybrids have gained a widespread reputation for prevention of viral crises, thanks to their promising antimicrobial properties as well as their potential to act as a carrier for vaccines. On the other hand, they can perform well as a photo-driven killer for viruses when they release reactive oxygen species (ROS) or photothermally damage the virus membrane. The nanofibers can also play a crucial protective role when integrated into face masks and personal protective equipment, particularly as hybridized with antiviral nanoparticles. In this draft, we review the antiviral nanohybrids that could potentially be applied to control, diagnose, and treat the consequences of COVID-19 pandemic. Considering the short age of this health problem, trivially the relevant technologies are not that many and are handful. Therefore, still progressing, older technologies with antiviral potential are also included and discussed. To conclude, nanohybrid nanomaterials with their high engineering potential and ability to inactivate pathogens including viruses will contribute decisively to the future of nanomedicine tackling the current and future pandemics.

Self-assembling synthetic nanoadjuvant scaffolds cross-link B cell receptors and represent new platform technology for therapeutic antibody production

Host antibody responses are pivotal for providing protection against infectious agents. We have pioneered a new class of self-assembling micelles based on pentablock copolymers that enhance antibody responses while providing a low inflammatory environment compared to traditional adjuvants. This type of "just-right" immune response is critical in the rational design of vaccines for older adults. Here, we report on the mechanism of enhancement of antibody responses by pentablock copolymer micelles, which act as scaffolds for antigen presentation to B cells and cross-link B cell receptors, unlike other micelle-forming synthetic block copolymers. We exploited this unique mechanism and developed these scaffolds as a platform technology to produce antibodies in vitro. We show that this novel approach can be used to generate laboratory-scale quantities of therapeutic antibodies against multiple antigens, including those associated with SARS-CoV-2 and Yersinia pestis, further expanding the value of these nanomaterials to rapidly develop countermeasures against infectious diseases.

Single-dose combination nanovaccine induces both rapid and durable humoral immunity and toxin neutralizing antibody responses against Bacillus anthracis

Bacillus anthracis, the causative agent of anthrax, continues to be a prominent biological warfare and bioterrorism threat. Vaccination is likely to remain the most effective and user-friendly public health measure to counter this threat in the foreseeable future. The commercially available AVA BioThrax vaccine has a number of shortcomings where improvement would lead to a more practical and effective vaccine for use in the case of an exposure event. Identification of more effective adjuvants and novel delivery platforms is necessary to improve not only the effectiveness of the anthrax vaccine, but also enhance its shelf stability and ease-of-use. Polyanhydride particles have proven to be an effective platform at adjuvanting the vaccine-associated adaptive immune response as well as enhancing stability of encapsulated antigens. Another class of adjuvants, the STING pathway-targeting cyclic dinucleotides, have proven to be uniquely effective at inducing a beneficial inflammatory response that leads to the rapid induction of high titer antibodies post-vaccination capable of providing protection against bacterial pathogens. In this work, we evaluate the individual contributions of cyclic di-GMP (CDG), polyanhydride nanoparticles, and a combination thereof towards inducing neutralizing antibody (nAb) against the secreted protective antigen (PA) from B. anthracis. Our results show that the combination nanovaccine elicited rapid, high titer, and neutralizing IgG anti-PA antibody following single dose immunization that persisted for at least 108 DPI.

Polyanhydride nanoparticles stabilize pancreatic cancer antigen MUC4β

Pancreatic cancer (PC) is one of the most lethal malignancies and represents an increasing and challenging threat, especially with an aging population. The identification of immunogenic PC-specific upregulated antigens and an enhanced understanding of the immunosuppressive tumor microenvironment have provided opportunities to enable the immune system to recognize cancer cells. Due to its differential upregulation and functional role in PC, the transmembrane mucin MUC4 is an attractive target for immunotherapy. In the current study we characterized the antigen stability, antigenicity and release kinetics of a MUC4β-nanovaccine to guide further optimization and, in vivo evaluation. Amphiphilic polyanhydride copolymers based on 20 mol % 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane and 80 mol % 1,6-bis(p-carboxyphenoxy)hexane were used to synthesize nanoparticles. Structurally stable MUC4β protein was released from the particles in a sustained manner and characterized by gel electrophoresis and fluorescence spectroscopy. Modest levels of protein degradation were observed upon release. The released protein was also analyzed by MUC4β-specific monoclonal antibodies using ELISA and showed no significant loss of epitope availability. Further, mice immunized with multiple formulations of combination vaccines containing MUC4β-loaded nanoparticles generated MUC4β-specific antibody responses. These results indicate that polyanhydride nanoparticles are viable MUC4β vaccine carriers, laying the foundation for evaluation of this platform for PC immunotherapy.

Prefusion F-Based Polyanhydride Nanovaccine Induces Both Humoral and Cell-Mediated Immunity Resulting in Long-Lasting Protection against Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection in both young children and in older adults. Despite the morbidity, mortality, and high economic burden caused by RSV worldwide, no licensed vaccine is currently available. We have developed a novel RSV vaccine composed of a prefusion-stabilized variant of the fusion (F) protein (DS-Cav1) and a CpG oligodeoxynucleotide adjuvant encapsulated within polyanhydride nanoparticles, termed RSVNanoVax. A prime-boost intranasal administration of RSVNanoVax in BALB/c mice significantly alleviated weight loss and pulmonary dysfunction in response to an RSV challenge, with protection maintained up to at least 6 mo postvaccination. In addition, vaccinated mice exhibited rapid viral clearance in the lungs as early as 2 d after RSV infection in both inbred and outbred populations. Vaccination induced tissue-resident memory CD4 and CD8 T cells in the lungs, as well as RSV F-directed neutralizing Abs. Based on the robust immune response elicited and the high level of durable protection observed, our prefusion RSV F nanovaccine is a promising new RSV vaccine candidate.

Biomaterials-based formulations and surfaces to combat viral infectious diseases

Rapidly growing viral infections are potent risks to public health worldwide. Accessible virus-specific antiviral vaccines and drugs are therapeutically inert to emerging viruses, such as Zika, Ebola, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, discovering ways to prevent and control viral infections is among the foremost medical challenge of our time. Recently, innovative technologies are emerging that involve the development of new biomaterial-based formulations and surfaces endowed with broad-spectrum antiviral properties. Here, we review emerging biomaterials technologies for controlling viral infections. Relevant advances in biomaterials employed with nanotechnology to inactivate viruses or to inhibit virus replication and further their translation in safe and effective antiviral formulations in clinical trials are discussed. We have included antiviral approaches based on both organic and inorganic nanoparticles (NPs), which offer many advantages over molecular medicine. An insight into the development of immunomodulatory scaffolds in designing new platforms for personalized vaccines is also considered. Substantial research on natural products and herbal medicines and their potential in novel antiviral drugs are discussed. Furthermore, to control contagious viral infections, i.e., to reduce the viral load on surfaces, current strategies focusing on biomimetic anti-adhesive surfaces through nanostructured topography and hydrophobic surface modification techniques are introduced. Biomaterial surfaces functionalized with antimicrobial polymers and nanoparticles against viral infections are also discussed. We recognize the importance of research on antiviral biomaterials and present potential strategies for future directions in applying these biomaterial-based approaches to control viral infections and SARS-CoV-2.

Polymeric Nanoparticle-Based Vaccine Adjuvants and Delivery Vehicles

As vaccine formulations have progressed from including live or attenuated strains of pathogenic components for enhanced safety, developing new adjuvants to more effectively generate adaptive immune responses has become necessary. In this context, polymeric nanoparticles have emerged as a promising platform with multiple advantages, including the dual capability of adjuvant and delivery vehicle, administration via multiple routes, induction of rapid and long-lived immunity, greater shelf-life at elevated temperatures, and enhanced patient compliance. This comprehensive review describes advances in nanoparticle-based vaccines (i.e., nanovaccines) with a particular focus on polymeric particles as adjuvants and delivery vehicles. Examples of the nanovaccine approach in respiratory infections, biodefense, and cancer are discussed.

Anti-Influenza Strategies Based on Nanoparticle Applications

Influenza virus has the potential for being one of the deadliest viruses, as we know from the pandemic's history. The influenza virus, with a constantly mutating genome, is becoming resistant to existing antiviral drugs and vaccines. For that reason, there is an urgent need for developing new therapeutics and therapies. Despite the fact that a new generation of universal vaccines or anti-influenza drugs are being developed, the perfect remedy has still not been found. In this review, various strategies for using nanoparticles (NPs) to defeat influenza virus infections are presented. Several categories of NP applications are highlighted: NPs as immuno-inducing vaccines, NPs used in gene silencing approaches, bare NPs influencing influenza virus life cycle and the use of NPs for drug delivery. This rapidly growing field of anti-influenza methods based on nanotechnology is very promising. Although profound research must be conducted to fully understand and control the potential side effects of the new generation of antivirals, the presented and discussed studies show that nanotechnology methods can effectively induce the immune responses or inhibit influenza virus activity both in vitro and in vivo. Moreover, with its variety of modification possibilities, nanotechnology has great potential for applications and may be helpful not only in anti-influenza but also in the general antiviral approaches.

COVID-19 vaccine development and a potential nanomaterial path forward

The COVID-19 pandemic has infected millions of people with no clear signs of abatement owing to the high prevalence, long incubation period and lack of established treatments or vaccines. Vaccines are the most promising solution to mitigate new viral strains. The genome sequence and protein structure of the 2019-novel coronavirus (nCoV or SARS-CoV-2) were made available in record time, allowing the development of inactivated or attenuated viral vaccines along with subunit vaccines for prophylaxis and treatment. Nanotechnology benefits modern vaccine design since nanomaterials are ideal for antigen delivery, as adjuvants, and as mimics of viral structures. In fact, the first vaccine candidate launched into clinical trials is an mRNA vaccine delivered via lipid nanoparticles. To eradicate pandemics, present and future, a successful vaccine platform must enable rapid discovery, scalable manufacturing and global distribution. Here, we review current approaches to COVID-19 vaccine development and highlight the role of nanotechnology and advanced manufacturing.

Controlling timing and location in vaccines

Vaccines are one of the most powerful technologies supporting public health. The adaptive immune response induced by immunization arises following appropriate activation and differentiation of T and B cells in lymph nodes. Among many parameters impacting the resulting immune response, the presence of antigen and inflammatory cues for an appropriate temporal duration within the lymph nodes, and further within appropriate subcompartments of the lymph nodes- the right timing and location- play a critical role in shaping cellular and humoral immunity. Here we review recent advances in our understanding of how vaccine kinetics and biodistribution impact adaptive immunity, and the underlying immunological mechanisms that govern these responses. We discuss emerging approaches to engineer these properties for future vaccines, with a focus on subunit vaccines.

Synthesis and Characterization of Rapidly Degrading Polyanhydrides as Vaccine Adjuvants

There is a currently a need to develop adjuvants that are best suited to simultaneously enhance immune responses, induce immunologic memory, improve patient compliance (i.e., reduce doses and inflammation), and provide vaccine shelf stability for stockpiling and global deployment to challenging environments. Biodegradable polyanhydrides have been investigated extensively to overcome such challenges. It has been shown that controlling copolymer composition can result in chemistry-dependent immunomodulatory capabilities. These studies have revealed that copolymers rich in sebacic acid (SA) are highly internalized by antigen presenting cells and confer improved shelf stability of encapsulated proteins, while copolymers rich in 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) also exhibit enhanced internalization by and activation of antigen presenting cells (APCs), in addition to providing superior retention of protein stability following encapsulation and release. However, to date, CPTEG:SA copolymers have not been synthesized and described. In this work, we hypothesized that new copolymers composed of CPTEG and SA would combine the advantages of both monomers in terms of enhanced thermal properties, maintaining antigenicity of encapsulated proteins following nanoparticle synthesis, and superior cellular internalization and activation by APCs, demonstrated by the upregulation of costimulatory markers CD80, CD86, and CD40, as well as the secretion of proinflammatory cytokines IL-6, IL-1β, and TNF-α. Herein, we describe the synthesis and design of novel CPTEG:SA nanoparticles with improved thermal properties, payload stability, and internalization by antigen presenting cells for applications in vaccine delivery. The performance of these new CPTEG:SA formulations was compared to that of traditional polyanhydride copolymers.

Combination of STING Pathway Agonist With Saponin Is an Effective Adjuvant in Immunosenescent Mice

There is an urgent need to improve protective responses to influenza vaccination in the elderly population, which is at especially high risk for adverse outcomes from influenza infection. Currently available inactivated vaccines provide limited protection, even when a 4-fold higher dose of the vaccine is administered. Adjuvants are often added to vaccines to boost protective efficacy. Here we describe a novel combination of an activator of the STING pathway, 2′,3′-cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) with a saponin adjuvant, that we found to be highly effective in boosting protective immunity from vaccination in an aged mouse model. Using this combination with a subunit influenza vaccine, we observed that survival of vaccinated 20 month-old mice after lethal challenge increased from 0 to 20% with unadjuvanted vaccine to 80–100%, depending on the vaccination route. Compared to unadjuvanted vaccine, the levels of vaccine-specific IgG and IgG2a increased by almost two orders of magnitude as early as 2 weeks after a single immunization with the adjuvanted formulation. By analyzing phosphorylation of interferon regulatory factor 3 (IRF3) in cell culture, we provide evidence that the saponin component increases access of exogenous cGAMP to the intracellular STING pathway. Our findings suggest that combining a STING activator with a saponin-based adjuvant increases the effectiveness of influenza vaccine in aged hosts, without having to increase dose or perform additional vaccinations. This study reports a novel adjuvant combination that (a) is more effective than current methods of boosting vaccine efficacy, (b) can be used to enhance efficacy of licensed influenza vaccines, and (c) results in effective protection using a single vaccine dose.

Safety and biocompatibility of injectable vaccine adjuvants composed of thermogelling block copolymer gels

Injectable thermogelling polymers have been recently investigated as novel adjuvants and delivery systems for next generation vaccines. As research into natural and synthetic biocompatible polymers progresses, the safety and biocompatibility of these compounds is of paramount importance. We have developed cationic pentablock copolymer (PBC) vaccine adjuvants based on Pluronic F127, a thermogelling triblock copolymer that has been approved by the FDA for multiple applications, and methacrylated poly(diethyl amino)ethyl methacrylate outer blocks. These novel materials have been demonstrated to effectively create an antigen depot, minimally impact antigen stability, and enhance the immune response to antigens (i.e., adjuvanticity) in mice. In this work, we investigated the safety and biocompatibility of the parent triblock Pluronic gels and the cationic PBC gels in mice. Histological analysis showed no injection site reactions and no damage to the liver or kidneys was observed upon administering the block copolymer formulations. However, the subcutaneous injection of a thermogelling Pluronic solution induced increased levels of lipids in the blood, with no further deleterious effects observed from the addition of the cationic outer blocks. This hyperlipidemia resolved within 30 days after the administration of the Pluronic formulation. To mitigate this adverse effect, the vaccine adjuvant formulations were modified by adding poly(vinyl alcohol), which allowed gelation, while reducing the amount of Pluronic in the formulation. This modified formulation abrogated the observed hyperlipidemia and no adverse effects were observed in the serum through biomarker analysis or at the injection site (i.e., inflammation) in comparison to the responses induced by administration of saline or incomplete Freund's adjuvant. These studies provide a foundation to developing these gels as adjuvants for next generation vaccines. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1754-1762, 2019.

Pentablock Copolymer Micelle Nanoadjuvants Enhance Cytosolic Delivery of Antigen and Improve Vaccine Efficacy while Inducing Low Inflammation

As the focus has shifted from traditional killed or live, attenuated vaccines toward subunit vaccines, improvements in vaccine safety have been confronted with low immunogenicity of protein antigens. This issue has been addressed by synthesizing and designing a wide variety of antigen carriers and adjuvants, such as Toll-like receptor agonists (e.g., MPLA, CpG). Studies have focused on optimizing adjuvants for improved cellular trafficking, cytosolic availability, and improved antigen presentation. In this work, we describe the design of novel amphiphilic pentablock copolymer (PBC) adjuvants that exhibit high biocompatibility and reversible pH- and temperature-sensitive micelle formation. We demonstrate improved humoral immunity in mice in response to single-dose immunization with PBC micelle adjuvants compared with soluble antigen alone. With the motive of exploring the mechanism of action of these PBC micelles, we studied intracellular trafficking of these PBC micelles with a model antigen and demonstrated that the PBC micelles associate with the antigen and enhance its cytosolic delivery to antigen-presenting cells. We posit that these PBC micelles operate via immune-enhancing mechanisms that are different from that of traditional Toll-like receptor activating adjuvants. The metabolic profile of antigen-presenting cells stimulated with traditional adjuvants and the PBC micelles also suggests distinct mechanisms of action. A key finding from this study is the low production of nitric oxide and reactive oxygen species by antigen-presenting cells when stimulated by PBC micelle adjuvants in sharp contrast to TLR adjuvants. Together, these studies provide a basis for rationally developing novel vaccine adjuvants that are safe, that induce low inflammation, and that can efficiently deliver antigen to the cytosol.