Nanovaccine Confers Dual Protection Against Influenza A Virus And Porcine Circovirus Type 2

Thiolated chitosan encapsulation constituted mucoadhesive nanovaccine confers broad protection against divergent influenza A viruses

Influenza A virus (IAV) poses a significant threat to human and animal health, necessitating the development of universal influenza vaccines that can effectively activate mucosal immunity. Intranasal immunization has attracted significant attention due to its capacity to induce triple immune responses, including mucosal secretory IgA. However, inducing mucosal immunity through vaccination is challenging due to the self-cleansing nature of the mucosal surface. Thiolated chitosan (TCS) were explored for mucosal vaccine delivery, capitalizing on biocompatibility and bioadhesive properties of chitosan, with thiol modification enhancing mucoadhesive capability. The focus was on developing a universal nanovaccine by utilizing TCS-encapsulated virus-like particles displaying conserved B-cell and T-cell epitopes from M2e and NP proteins of IAV. The optimal conditions for nanoparticle formation were investigated by adjusting the thiol groups content of TCS and the amount of sodium tripolyphosphate. The nanovaccine induced robust immune responses and provided complete protection against IAVs from different species following intranasal immunization. The broad protective effect of nanovaccines can be attributed to the synergistic effect of antibodies and T cells. This study developed a universal intranasal nanovaccine and demonstrated the potential of TCS in the development of mucosal vaccines for respiratory infectious diseases.

An experimental universal swine influenza a virus (IAV) vaccine candidate based on the M2 ectodomain (M2e) peptide does not provide protection against H1N1 IAV challenge in pigs

Swine flu is a common disease problem in North American pig populations and swine influenza A viruses (IAV) are extremely diverse and the lack of cross protection between heterologous strains is impacting vaccine efficacy in the field. The objective of this study was to design and test a novel swine flu vaccine targeting the M2 ectodomain (M2e) of IAV, a highly conserved region within the IAV proteome. In brief, an M2e peptide was designed to match the predominant swine IAV M2 sequence based on global analysis of sequences from pigs and humans. The resulting sequence was used to synthesize the M2e peptide coupled to a carrier protein. The final vaccine concentration was 200 µg per dose, and a commercial, microemulsion-based aqueous adjuvant was added. Nine 3-week-old IAV negative piglets were randomly assigned to three groups and rooms including non-vaccinated pigs (NEG-CONTROLs) and vaccinated pigs using the intramuscular (M2e-IM) or the intranasal route (M2e-IN). Vaccinations were done at weaning and again at 2 weeks later. An in-house enzyme-linked immunosorbent assay (ELISA) was developed and validated to study the M2e IgG antibody response and demonstrated M2e-IM pigs had a higher systemic antibody response compared to M2e-IN pigs. Subsequently, an IAV challenge study was conducted. The results indicated that M2e-IM vaccinated pigs were not protected from H1N1 (US pandemic clade, global clade 1A.3.3.2) challenge despite having a strong humoral anti-M2e immune response. In conclusion, while the experimental IAV vaccine was able to induce anti-M2e antibodies, when challenged with H1N1, the vaccinated pigs were not protected, perhaps indicating that reactivity to the M2e antigen alone is not sufficient to reduce clinical signs, lesions or shedding associated with experimental IAV challenge.

Construction, expression and assemble of EMCV VLPs and their potency evaluation

Encephalomycarditis virus (EMCV) is an essential pathogen with a broad host range and causes enormous economic losses to the pig industry worldwide. Here, we constructed and assembled the EMCV virus-like particles (VLPs) in vitro and verified high efficiency of virus protection. Results showed that the proteins auto-assembled into VLPs successfully in vitro. The animal experiments revealed that high-titer antibody production is triggered by VLPs. Meanwhile, the mice challenged with EMCV were obviously protected. The protection rate of group VLPs with the adjuvant was 75%, while that of the VLPs group was 62.5% compared to the control. These findings indicate that recombinant EMCV VLPs have a remarkable anti-EMCV effect and could be a new vaccine candidate for the control of EMCV infection.

Virus-like Particle Vaccines and Platforms for Vaccine Development

Virus-like particles (VLPs) have gained a lot of interest within the past two decades. The use of VLP-based vaccines to protect against three infectious agents-hepatitis B virus, human papillomavirus, and hepatitis E virus-has been approved; they are very efficacious and offer long-lasting immune responses. Besides these, VLPs from other viral infectious agents (that infect humans, animals, plants, and bacteria) are under development. These VLPs, especially those from human and animal viruses, serve as stand-alone vaccines to protect against viruses from which the VLPs were derived. Additionally, VLPs, including those derived from plant and bacterial viruses, serve as platforms upon which to display foreign peptide antigens from other infectious agents or metabolic diseases such as cancer, i.e., they can be used to develop chimeric VLPs. The goal of chimeric VLPs is to enhance the immunogenicity of foreign peptides displayed on VLPs and not necessarily the platforms. This review provides a summary of VLP vaccines for human and veterinary use that have been approved and those that are under development. Furthermore, this review summarizes chimeric VLP vaccines that have been developed and tested in pre-clinical studies. Finally, the review concludes with a snapshot of the advantages of VLP-based vaccines such as hybrid/mosaic VLPs over conventional vaccine approaches such as live-attenuated and inactivated vaccines.

A mini review for lipid-based nanovaccines: from their design to their applications

Nanovaccines have shown to be effective, and this is the reason they are preferred than conventional vaccines. The scope of this review is to describe the role, mechanisms, and advantages of nano vaccines based on lipids, and present the most important types, their physicochemical characteristics, as well as their challenges. The most important categories of lipid nano-vaccines are liposomal nano vaccines and (virus-lipid nanoparticles (NPs)/virosomes. Examples of vaccine formulations from each category are presented and analyzed below, focusing on their structure and physicochemical characteristics. In all cases, a nanoscale platform is used, enriched with adjuvants, antigens, and other helping agents to trigger immune response process and achieve cell targeting, and eventually immunity against the desired disease. The exact mechanism of action of each vaccine is not always completely known or understood. Physicochemical characteristics, such as particle size, morphology/shape, and zeta potential are also mentioned as they seem to affect the properties and mechanism of action of the vaccine formulation.

Multiepitope Subunit Peptide-Based Nanovaccine against Porcine Circovirus Type 2 (PCV2) Elicited High Antibody Titers in Vaccinated Mice

Porcine circovirus 2 (PCV2) infection is one of the most serious threats to the swine industry. While the disease can be prevented, to some extent, by commercial PCV2a vaccines, the evolving nature of PCV2 necessitates the development of a novel vaccine that can compete with the mutations of the virus. Thus, we have developed novel multiepitope vaccines based on the PCV2b variant. Three PCV2b capsid protein epitopes, together with a universal T helper epitope, were synthesized and formulated with five delivery systems/adjuvants: complete Freund's adjuvant, poly(methyl acrylate) (PMA), poly(hydrophobic amino acid), liposomes and rod-shaped polymeric nanoparticles built from polystyrene-poly(N-isopropylacrylamide)-poly(N-dimethylacrylamide). Mice were subcutaneously immunized with the vaccine candidates three times at three-week intervals. All vaccinated mice produced high antibody titters after three immunizations as analyzed by the enzyme-linked immunosorbent assay (ELISA), while mice vaccinated with PMA-adjuvanted vaccine elicited high antibody titers even after a single immunization. Thus, the multiepitope PCV2 vaccine candidates designed and examined here show strong potential for further development.

A modular and self-adjuvanted multivalent vaccine platform based on porcine circovirus virus-like nanoparticles

BACKGROUND

Virus-like particles (VLPs) are supramolecular structures composed of multiple protein subunits and resemble natural virus particles in structure and size, making them highly immunogenic materials for the development of next-generation subunit vaccines. The orderly and repetitive display of antigenic epitopes on particle surface allows efficient recognition and cross-link by B cell receptors (BCRs), thereby inducing higher levels of neutralizing antibodies and cellular immune responses than regular subunit vaccines. Here, we present a novel multiple antigen delivery system using SpyCatcher/Spytag strategy and self-assembled VLPs formed by porcine circovirus type 2 (PCV2) Cap, a widely used swine vaccine in solo.

RESULTS

Cap-SC, recombinant Cap with a truncated SpyCatcher polypeptide at its C-terminal, self-assembled into 26-nm VLPs. Based on isopeptide bonds formed between SpyCatcher and SpyTag, classical swine fever virus (CSFV) E2, the antigen of interest, was linked to SpyTag and readily surface-displayed on SpyCatcher decorated Cap-SC via in vitro covalent conjugation. E2-conjugated Cap VLPs (Cap-E2 NPs) could be preferentially captured by antigen presenting cells (APCs) and effectively stimulate APC maturation and cytokine production. In vivo studies confirmed that Cap-E2 NPs elicited an enhanced E2 specific IgG response, which was significantly higher than soluble E2, or the admixture of Cap VLPs and E2. Moreover, E2 displayed on the surface did not mask the immunodominant epitopes of Cap-SC VLPs, and Cap-E2 NPs induced Cap-specific antibody levels and neutralizing antibody levels comparable to native Cap VLPs.

CONCLUSION

These results demonstrate that this modularly assembled Cap-E2 NPs retains the immune potential of Cap VLP backbone, while the surface-displayed antigen significantly elevated E2-induced immune potency. This immune strategy provides distinctly improved efficacy than conventional vaccine combination. It can be further applied to the development of dual or multiple nanoparticle vaccines to prevent co-infection of PCV2 and other swine pathogens.

The truncated form of flagellin (tFlic) provides the 2dCap subunit vaccine with better immunogenicity and protective effects in mice

Porcine circovirus type 2 (PCV2) is the main causative agent of porcine circovirus-associated diseases, and it causes substantial economic losses in the swine industry each year. It is crucial to develop an effective vaccine against the circulating strain PCV2d, which is prone to substantial degrees of mutation. In this study, a truncated form of flagellin (tFlic: 85-111 aa) was inserted into the C-terminal sequence of 2dCap, and Western blotting results showed that recombinant Cap-tFlic VLPs were successfully expressed. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) data indicated that purified recombinant Cap-tFlic fusion proteins existed in the form of polymers and that tFlic could not affect the formation and internalization of VLPs. Integrated Cap-tFlic VLPs induced the expression of antigen presentation-related factors (MHC-II and CD86) by bone marrow-derived dendritic cells (BM-DCs), and the expression of TLR5-related factors (TNF-α) was dramatically elevated. Mice intramuscularly immunized with Cap-tFlic VLPs exhibited significantly higher levels of Cap-specific antibodies and neutralizing antibodies than mice immunized with wild-type Cap VLPs. The data obtained in the current study indicate that Cap-tFlic may be a candidate for a subunit vaccine against PCV2 in the future.

Nanoparticles in allergen immunotherapy

PURPOSE OF REVIEW

Allergen immunotherapy is the only recognized causal treatment for allergic disease that modulates the immune system toward a tolerogenic or desensitized state. Allergens or their derivative preparations are formulated with adjuvants of different origin and having diverse immunological functions, such as prolonged tissue release and specific immunomodulatory properties. In the last 2 decades, thanks to developments in the field of nanotechnology, more biosafe nanoscale materials have become available for use as pharmaceutical adjuvants in medical research.

RECENT FINDINGS

Nanomaterials possess unique and versatile properties which can be employed to develop drug carriers with safer profiles, better stability in physiological conditions and immunomodulatory properties. Nanoparticles can have an adjuvant effect per se or also when they are packed in structures whose physical-chemical properties can be handled in a way that also influences its release dynamics. In particular, it has been suggested that nanoparticle preparations can be put in complexes or loaded with allergens or allergenic extracts, opening the way to innovative paradigms.

SUMMARY

In this review, we analyze allergen/nanoparticle properties in terms of cytotoxicity, stability and immunogenic reaction in in-vitro and animal systems.

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.

Displaying epitope B and epitope 7 of porcine reproductive and respiratory syndrome virus on virus like particles of porcine circovirus type 2 provides partial protection to pigs

The Cap of porcine circovirus type 2 (PCV2) can be assembled into virus like particles (VLPs) in vitro that have multiple loops located on the particle surface. This would make it a good vehicle for displaying exogenous proteins or epitopes. We derived two epitopes, epitope B (EpB, S³⁷HIQLIYNL⁴⁵) and epitope 7 (Ep7, Q¹⁹⁶WGRL²⁰⁰) from Gp5 of the highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV). We replaced the core region of Loop CD (L⁷⁵PPGGGSN⁸²) and the carboxyl terminus (K²²²DPPL²²⁶) of PCV2 Cap, respectively, to construct a bi-epitope chimeric PCV2 Cap. Its immunogenicity and protective effects were evaluated as one PRRSV subunit vaccine. The chimeric PCV2 Cap was soluble, efficiently expressed in an Escherichia coli expression system, and could be self-assembled into chimeric virus like particles (cVLPs) with a diameter of 12-15 nm. Western blotting confirmed that the cVLPs could be specifically recognized by anti-PCV2, anti-EpB and anti-Ep7 antibodies. The cVLPs vaccine could alleviate the clinical symptoms and reduce the viral loads after HP-PRRSV challenge in 100-120 days old pigs. These data suggest that the cVLPs vaccine could provide pigs with partial protection against homologous PRRSV strains, and it provides a new design for additional PRRSV subunit vaccines.

State-of-the-Art of Nanodiagnostics and Nanotherapeutics against SARS-CoV-2

The pandemic outbreak of SARS-CoV-2, with millions of infected patients worldwide, has severely challenged all aspects of public health. In this regard, early and rapid detection of infected cases and providing effective therapeutics against the virus are in urgent demand. Along with conventional clinical protocols, nanomaterial-based diagnostics and therapeutics hold a great potential against coronavirus disease 2019 (COVID-19). Indeed, nanoparticles with their outstanding characteristics would render additional advantages to the current approaches for rapid and accurate diagnosis and also developing prophylactic vaccines or antiviral therapeutics. In this review, besides presenting an overview of the coronaviruses and SARS-CoV-2, we discuss the introduced nanomaterial-based detection assays and devices and also antiviral formulations and vaccines for coronaviruses.

Reasonable permutation of M2e enhances the effect of universal influenza nanovaccine

Influenza A virus (IAV) occasionally cross-species transmission among humans, swine and avian. The ectodomain of matrix protein 2 (M2e) is highly conserved in IAV, and multi-copy M2e from different species are usually displayed on the surface of nanoparticles to improve immunogenicity and constitute universal IAV nanovaccines. In our previous study, three M2e were inserted into the C-terminal of Cap protein of porcine circovirus type 2 (PCV2) to form a universal nanovaccine that provides protection against PCV2 and different subtypes of IAV. However, M2e adopts at least two converted conformations, and the intermolecular linker of M2e enhances the conformational instability, which limits the recognition by B cell receptors and production of high-level antibodies. Here, we report that the permutation of M2e affects effectiveness of nanovaccines. Three M2e derived from humans, swine and avian IAV were inserted into the C-terminal of Cap protein to form nanovaccines. Immunoprotective effects of different M2e arrangements were explored in mice. Results showed that the M2e closest to the surface of nanoparticle induced the most efficient protection against IAV derived from corresponding species. The results will contribute to develop more effective PCV2 and universal IAV bivalent nanovaccines for pigs, as well as species-specific universal IAV vaccines.

Future perspectives on swine viral vaccines: where are we headed?

Deliberate infection of humans with smallpox, also known as variolation, was a common practice in Asia and dates back to the fifteenth century. The world's first human vaccination was administered in 1796 by Edward Jenner, a British physician. One of the first pig vaccines, which targeted the bacterium Erysipelothrix rhusiopathiae, was introduced in 1883 in France by Louis Pasteur. Since then vaccination has become an essential part of pig production, and viral vaccines in particular are essential tools for pig producers and veterinarians to manage pig herd health. Traditionally, viral vaccines for pigs are either based on attenuated-live virus strains or inactivated viral antigens. With the advent of genomic sequencing and molecular engineering, novel vaccine strategies and tools, including subunit and nucleic acid vaccines, became available and are being increasingly used in pigs. This review aims to summarize recent trends and technologies available for the production and use of vaccines targeting pig viruses.

Topical review on nano-vaccinology: Biochemical promises and key challenges

Nanomaterials have wide-ranging biomedical applications in prevention, treatment and control of diseases. Nanoparticle based vaccines have proven prodigious prophylaxis of various infectious and non-infectious diseases of human and animal concern. Nano-vaccines outnumber the conventional vaccines by virtue of plasticity in physio-chemical properties and ease of administration. The efficacy of nano-based vaccines may be attributed to the improved antigen stability, minimum immuno-toxicity, sustained release, enhanced immunogenicity and the flexibility of physical features of nanoparticles. Based on these, the nano-based vaccines have potential to evoke both cellular and humoral immune responses. Targeted and highly specific immunological pathways required for solid and long lasting immunity may be achieved with specially engineered nano-vaccines. This review presents an insight into the prevention of infectious diseases (of bacterial, viral and parasitic origin) and non-infectious diseases (cancer, auto-immune diseases) using nano-vaccinology. Additionally, key challenges to the effective utilization of nano-vaccines from bench to clinical settings have been highlighted as research domains for future.

Advancements in prophylactic and therapeutic nanovaccines

Vaccines activate suitable immune responses to fight against diseases but can possess limitations such as compromised efficacy and immunogenic responses, poor stability, and requirement of adherence to multiple doses. ‘Nanovaccines’ have been explored to elicit a strong immune response with the advantages of nano-sized range, high antigen loading, enhanced immunogenicity, controlled antigen presentation, more retention in lymph nodes and promote patient compliance by a lower frequency of dosing. Various types of nanoparticles with diverse pathogenic or foreign antigens can help to overcome immunotolerance and alleviate the need of booster doses as required with conventional vaccines. Nanovaccines have the potential to induce both cell-mediated and antibody-mediated immunity and can render long-lasting immunogenic memory. With such properties, nanovaccines have shown high potential for the prevention of infectious diseases such as acquired immunodeficiency syndrome (AIDS), malaria, tuberculosis, influenza, and cancer. Their therapeutic potential has also been explored in the treatment of cancer. The various kinds of nanomaterials used for vaccine development and their effects on immune system activation have been discussed with special relevance to their implications in various pathological conditions.

Statement of Significance

Interaction of nanoparticles with the immune system has opened multiple avenues to combat a variety of infectious and non-infectious pathological conditions. Limitations of conventional vaccines have paved the path for nanomedicine associated benefits with a hope of producing effective nanovaccines. This review highlights the role of different types of nanovaccines and the role of nanoparticles in modulating the immune response of vaccines. The applications of nanovaccines in infectious and non-infectious diseases like malaria, tuberculosis, AIDS, influenza, and cancers have been discussed. It will help the readers develop an understanding of mechanisms of immune activation by nanovaccines and design appropriate strategies for novel nanovaccines.