Self-assembling ferritin nanoparticles coupled with linear sequences from canine distemper virus haemagglutinin protein elicit robust immune responses

Expression of recombinant swine ferritin heavy chain with enhanced solubility in Escherichia coli and simplified purification of ferritin nanoparticles

Ferritin is a versatile biomolecule used in various medical applications such as drug delivery, vaccines, biological imaging, and diagnostics. The purity and concentration of the ferritin nanoparticles are crucial for achieving excellent outcomes. In this study, we expressed and purified the recombinant swine ferritin heavy chain (rsFTH) as a new candidate for recombinant ferritin nanoparticles. We generated two types of plasmids that can express rsFTH in mammalian and prokaryotic systems. The myc-tagged rsFTH expressed in the mammalian system was purified and ferritin nanoparticles were validated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). A prokaryotic expression system was used to produce rsFTH on a large scale. Protein expression was optimized in Escherichia coli BL21 under varying temperatures and IPTG conditions, and solubility was enhanced by incubation at 25 °C for 18-22 h in auto-induction media, resulting in approximately >50 % protein content in the soluble fraction compared with the pellet. Protein purification was achieved using His-tag affinity chromatography and dialysis with Tris-HCl buffer, yielding adequately pure rsFTH without any apparent protein aggregates. SDS-PAGE and Western blot analysis confirmed the expected molecular weight of rsFTH, and Native-PAGE demonstrated polymerization into higher molecular weight forms. Particle size analysis of purified rsFTH revealed a mean diameter of 15.5 nm, with transmission electron microscopy (TEM) imaging confirming spherical ferritin particles with an iron core. These results suggest that rsFTH can be efficiently expressed and purified in both mammalian and bacterial systems, and has potential applications in nanotechnology and biotechnology.

Self-assembling nanoparticle vaccine elicits a robust protective immune response against avian influenza H5N6 virus in chickens

The continuous circulation and evolution of the H5N6 subtype highly pathogenic avian influenza virus (HPAIV) challenge the development of the global poultry industry and human public health security. To address the potential threat of the H5N6 virus, a secure and efficacious vaccine is urgent. In our research, a self-assembling nanoparticle vaccine presenting the hemagglutinin of the H5N6 AIV was developed based on the ferritin antigen display platform. The results showed that a single-dose vaccination of this nanoparticle vaccine elicited potent hemagglutination inhibition (HI) antibody responses and neutralizing antibody responses in the chickens. Meanwhile, the fused HA-ferritin nanoparticle vaccine induced significantly higher levels of Th1/Th2 immune responses. After a lethal attack with the H5N6 virus, the fused HA-ferritin nanoparticle vaccine conferred chickens with 100 % (10/10) challenge protection. Importantly, the fused HA-ferritin nanoparticle with only 28 hemagglutination units (HAU) provided chickens with immune protection comparable to commercial inactivated vaccines and protected the chickens from severe lung pathological damage. These results in our study support the superiority of ferritin as an antigen display platform and suggest that self-assembled nanoparticle vaccines based on this platform possess the potential as an avian influenza candidate vaccine.

Ferritin Vaccine Platform for Animal and Zoonotic Viruses

Viral infections in animals continue to pose a significant challenge, affecting livestock health, welfare, and food safety, and, in the case of zoonotic viruses, threatening global public health. The control of viral diseases currently relies on conventional approaches such as inactivated or attenuated vaccines produced via platforms with inherent limitations. Self-assembling ferritin nanocages represent a novel vaccine platform that has been utilized for several viruses, some of which are currently undergoing human clinical trials. Experimental evidence also supports the potential of this platform for developing commercial vaccines for veterinary viruses. In addition to improved stability and immunogenicity, ferritin-based vaccines are safe and DIVA-compatible, and can be rapidly deployed in response to emerging epidemics or pandemics. This review discusses the structural and functional properties of ferritin proteins, followed by an overview of the design and production of ferritin-based vaccines, the mechanisms of immune responses, and their applications in developing vaccines against animal and zoonotic viruses.

Self-Assembled Ferritin Nanoparticles for Delivery of Antigens and Development of Vaccines: From Structure and Property to Applications

Ferritin, an iron storage protein, is ubiquitously distributed across diverse life forms, fulfilling crucial roles encompassing iron retention, conversion, orchestration of cellular iron metabolism, and safeguarding cells against oxidative harm. Noteworthy attributes of ferritin include its innate amenability to facile modification, scalable mass production, as well as exceptional stability and safety. In addition, ferritin boasts unique physicochemical properties, including pH responsiveness, resilience to elevated temperatures, and resistance to a myriad of denaturing agents. Therefore, ferritin serves as the substrate for creating nanomaterials typified by uniform particle dimensions and exceptional biocompatibility. Comprising 24 subunits, each ferritin nanocage demonstrates self-assembly capabilities, culminating in the formation of nanostructures akin to intricate cages. Recent years have witnessed the ascendance of ferritin-based self-assembled nanoparticles, owing to their distinctive physicochemical traits, which confer substantial advantages and wide-ranging applications within the biomedical domain. Ferritin is highly appealing as a carrier for delivering drug molecules and antigen proteins due to its distinctive structural and biochemical properties. This review aims to highlight recent advances in the use of self-assembled ferritin as a novel carrier for antigen delivery and vaccine development, discussing the molecular mechanisms underlying its action, and presenting it as a promising and effective strategy for the future of vaccine development.

Immune responses induced by Mycobacterium tuberculosis heat-resistant antigen (Mtb-HAg) upon co-administration with Bacillus Calmette-Guérin in mice

OBJECTIVES

To preliminarily assess the immunogenicity of Mtb-HAg in mice and the synergistic effect provided by HAg when co-immunised with BCG.

METHODS

Mice were randomly grouped for different immunisations and then spleens were aseptically removed and lymphocytes were extracted for immediate detection of cytokines transcript levels and stimulation index(SI), cytokine secretion and multifunctional antigen-specific T cells were detected after incubation for different times.

RESULTS

HAg extracted from active Mtb is a group of mixed polypeptides with molecular weights of (10-14) kDa. It can significantly stimulate lymphocytes proliferation and increase SI. Injection of HAg alone and in combination with BCG induced significantly higher numbers of multifunctional antigen-specific T cells including CD4+ IFN-γ+, CD4+ IL-2+, CD8+ IFN-γ+, and CD8+ IL-2+ cells than that in BCG-treated mice. Co-immunisation induced the secretion of higher levels of IFN-γ, TNF-α, IL-2 and IL-4 and increased their mRNA expression levels. Significant increases in the transcription levels of IL-10, IL-12 and IL-17 were observed in the co-immunised group with the assistance of HAg.

CONCLUSION

We demonstrated that HAg has favourable immunogenicity, triggers a stronger Th1-type immune response and proposed the hypothesis that HAg can be used as a BCG booster to further enhance the benefits of BCG.

Development of a Ferritin Protein Nanoparticle Vaccine with PRRSV GP5 Protein

Porcine reproductive and respiratory syndrome virus (PRRSV) presents a significant threat to the global swine industry. The development of highly effective subunit nanovaccines is a promising strategy for preventing PRRSV variant infections. In this study, two different types of ferritin (Ft) nanovaccines targeting the major glycoprotein GP5, named GP5m-Ft and (Bp-IVp)3-Ft, were constructed and evaluated as vaccine candidates for PRRSV. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) demonstrated that both purified GP5m-Ft and (Bp-IVp)3-Ft proteins could self-assemble into nanospheres. A comparison of the immunogenicity of GP5m-Ft and (Bp-IVp)3-Ft with an inactivated PRRSV vaccine in BALB/c mice revealed that mice immunized with GP5m-Ft exhibited the highest ELISA antibody levels, neutralizing antibody titers, the lymphocyte proliferation index, and IFN-γ levels. Furthermore, vaccination with the GP5m-Ft nanoparticle effectively protected piglets against a highly pathogenic PRRSV challenge. These findings suggest that GP5m-Ft is a promising vaccine candidate for controlling PRRS.

Epitope screening and self-assembled nanovaccine molecule design of PDCoV-S protein based on immunoinformatics

Based on the whole virus or spike protein of pigs, δ coronavirus (PDCoV) as an immunogen may have unrelated antigenic epitope interference. Therefore, it is essential for screening and identifying advantageous protective antigen epitopes. In addition, immunoinformatic tools are described as an important aid in determining protective antigenic epitopes. In this study, the primary, secondary, and tertiary structures of vaccines were measured using ExPASy, PSIPRED 4.0, and trRosetta servers. Meanwhile, the molecular docking analysis and vector of the candidate nanovaccine were constructed. The immune response of the candidate vaccine was simulated and predicted using the C-ImmSim server. This experiment screened B cell epitopes with strong immunogenicity and high conservation, CTL epitopes, and Th epitopes with IFN-γ and IL-4 positive spike proteins. Ferritin is used as a self-assembled nanoparticle element for designing candidate nanovaccine. After analysis, it has been found to be soluble, stable, non-allergenic, and has a high affinity for its target receptor, TLR-3. The preliminary simulation analysis results show that the candidate nanovaccine has the ability to induce a humoral and cellular immune response. Therefore, it may provide a new theoretical basis for research on coronavirus self-assembled nanovaccines. It may be an effective candidate vaccine for controlling and preventing PDCoV.

Immunogenicity and protective efficacy of a novel bacterium-like particle-based vaccine displaying canine distemper virus antigens in mice and dogs

Canine distemper virus (CDV) poses a severe threat to both domesticated and wild animals, including multiple carnivores. With the continued expansion of its host range, there is an urgent need for the development of a safer and more effective vaccine. In this study, we developed subunit vaccines based on a bacterium-like particle (BLP) delivery platform containing BLPs-F and BLPs-H, which display the CDV F and H glycoprotein antigens, respectively, using the antigen-protein anchor fusions produced by a recombinant baculovirus insect cell expression system. The combination of BLPs-F and BLPs-H (CDV-BLPs), formulated with colloidal manganese salt [Mn jelly (MnJ)] adjuvant, triggered robust CDV-specific antibody responses and a substantial increase in the number of interferon gamma (IFN-γ)-secreting CD4+ and CD8+ T cells in mice. Dogs immunized intramuscularly with this vaccine not only produced CDV-specific IgG but also displayed elevated concentrations of IFN-γ and interleukin 6 in their serum, along with an increase of the CD3+CD4+ and CD3+CD8+ T cell subsets. Consequently, this heightened immune response provided effective protection against disease development and reduced viral shedding levels following challenge with a virulent strain. These findings suggest that this BLP-based subunit vaccine has the potential to become a novel canine distemper vaccine.

IMPORTANCE

Many sensitive species require a safe and effective distemper vaccine. Non-replicating vaccines are preferred. We constructed subunit particles displaying canine distemper virus (CDV) antigens based on a bacterium-like particle (BLP) delivery platform. The CDV-BLPs formulated with theMn jelly adjuvant induced robust humoral and cell-mediated immune responses to CDV in mice and dogs, thereby providing effective protection against a virulent virus challenge. This work is an important step in developing a CDV subunit vaccine.

Self-Assembled Multiepitope Nanovaccine Provides Long-Lasting Cross-Protection against Influenza Virus

Seasonal influenza vaccines typically provide strain-specific protection and are reformulated annually, which is a complex and time-consuming process. Multiepitope vaccines, combining multiple conserved antigenic epitopes from a pathogen, can trigger more robust, diverse, and effective immune responses, providing a potential solution. However, their practical application is hindered by low immunogenicity and short-term effectiveness. In this study, multiple linear epitopes from the conserved stem domain of hemagglutinin and the ectodomain of matrix protein 2 are combined with the Helicobacter pylori ferritin, a stable self-assembled nanoplatform, to develop an influenza multiepitope nanovaccine, named MHF. MHF is prokaryotically expressed in a soluble form and self-assembles into uniform nanoparticles. The subcutaneous immunization of mice with adjuvanted MHF induces cross-reactive neutralizing antibodies, antibody-dependent cell-mediated cytotoxicity, and cellular immunity, offering complete protection against H3N2 as well as partial protection against H1N1. Importantly, the vaccine cargo delivered by ferritin triggers epitope-specific memory B-cell responses, with antibody level persisting for over 6 months post-immunization. These findings indicate that self-assembled multiepitope nanovaccines elicit potent and long-lasting immune responses while significantly reducing the risk of vaccine escape mutants, and offer greater practicality in terms of scalable manufacturing and genetic manipulability, presenting a promising and effective strategy for future vaccine development.

Self-adjuvant multiepitope nanovaccine based on ferritin induced long-lasting and effective mucosal immunity against H3N2 and H1N1 viruses in mice

The influenza A virus (IAV) is a ubiquitous and continuously evolving respiratory pathogen. The intranasal vaccination mimicking natural infections is an attractive strategy for controlling IAVs. Multiepitope vaccines accurately targeting multiple conserved domains have the potential to broaden the protective scope of current seasonal influenza vaccines and reduce the risk of generating escape mutants. Here, multiple linear epitopes from the matrix protein 2 ectodomain (M2e) and the hemagglutinin stem domain (HA2) are fused with the Helicobacter pylori ferritin, a self-assembled nanocarrier and mucosal adjuvant, to develop a multiepitope nanovaccine. Through intranasal delivery, the prokaryotically expressed multiepitope nanovaccine elicits long-lasting mucosal immunity, broad humoral immunity, and robust cellular immunity without any adjuvants, and confers complete protection against H3N2 and H1N1 subtypes of IAV in mice. Importantly, this intranasal multiepitope nanovaccine triggers memory B-cell responses, resulting in secretory immunoglobulin A (sIgA) and serum immunoglobulin G (IgG) levels persisting for more than five months post-immunization. Therefore, this intranasal ferritin-based multiepitope nanovaccine represents a promising approach to combating respiratory pathogens.

Self-assembling ferritin nanoplatform for the development of infectious hematopoietic necrosis virus vaccine

Self-assembling protein nanoparticles are used as a novel vaccine design platform to improve the stability and immunogenicity of safe subunit vaccines, while providing broader protection against viral infections. Infectious Hematopoietic Necrosis virus (IHNV) is the causative agent of the WOAH-listed IHN diseases for which there are currently no therapeutic treatments and no globally available commercial vaccine. In this study, by genetically fusing the virus glycoprotein to the H. pylori ferritin as a scaffold, we constructed a self-assembling IHNV nanovaccine (FerritVac). Despite the introduction of an exogenous fragment, the FerritVac NPs show excellent stability same as Ferritin NPs under different storage, pH, and temperature conditions, mimicking the harsh gastrointestinal condition of the virus main host (trout). MTT viability assays showed no cytotoxicity of FerritVac or Ferritin NPs in zebrafish cell culture (ZFL cells) incubated with different doses of up to 100 µg/mL for 14 hours. FerritVac NPs also upregulated expression of innate antiviral immunity, IHNV, and other fish rhabdovirus infection gene markers (mx, vig1, ifit5, and isg-15) in the macrophage cells of the host. In this study, we demonstrate the development of a soluble recombinant glycoprotein of IHNV in the E. coli system using the ferritin self-assembling nanoplatform, as a biocompatible, stable, and effective foundation to rescue and produce soluble protein and enable oral administration and antiviral induction for development of a complete IHNV vaccine. This self-assembling protein nanocages as novel vaccine approach offers significant commercial potential for non-mammalian and enveloped viruses.

Recombinant ferritins for multimodal nanomedicine

In all living organisms, ferritins are a group of proteins important for maintaining iron homeostasis. Increasing amount of studies has shown that recombinant ferritins can be widely used in multimodal nanomedicine, especially for anticancer treatment and vaccination. Recombinant particles prepared by fusing viral proteins and ferritin subunits produce a better immune response and higher antibody titres. Moreover, actively-targeted ferritin nanoparticles can recognise receptors and deliver natural or chemical drugs specifically to the tumour tissue. In addition, ferritin-linked or loaded with contrast agents or fluorescent dyes can be used as multimodal particles useful cancer theranostics. In this review, we fully summarised the unitisation of recombinant ferritins in multimodal nanomedicine. The research progress of using recombinant ferritins as nanovaccines, nanozymes, and bioengineered nanocarriers for targeted therapy and bioimaging is emphasised.

Protein-based Nanoparticle Vaccine Approaches Against Infectious Diseases

The field of vaccine development has seen an increase in the number of rationally designed technologies that increase effectiveness against vaccine-resistant pathogens, while not compromising safety. Yet, there is still an urgent need to expand and further understand these platforms against complex pathogens that often evade protective responses. Nanoscale platforms have been at the center of new studies, especially in the wake of the coronavirus disease 2019 (COVID-19), with the aim of deploying safe and effective vaccines in a short time period. The intrinsic properties of protein-based nanoparticles, such as biocompatibility, flexible physicochemical characteristics, and variety have made them an attractive platform against different infectious disease agents. In the past decade, several studies have tested both lumazine synthase-, ferritin-, and albumin-based nanoplatforms against a wide range of complex pathogens in pre-clinical studies. Owed to their success in pre-clinical studies, several studies are undergoing human clinical trials or are near an initial phase. In this review we highlight the different protein-based platforms, mechanisms of synthesis, and effectiveness of these over the past decade. In addition, some challenges, and future directions to increase their effectiveness are also highlighted. Taken together, protein-based nanoscaffolds have proven to be an effective means to design rationally designed vaccines, especially against complex pathogens and emerging infectious diseases.

A biepitope, adjuvant-free, self-assembled influenza nanovaccine provides cross-protection against H3N2 and H1N1 viruses in mice

Currently, the incorporation of multiple epitopes into vaccines is more desirable than the incorporation of a single antigen for universal influenza vaccine development. However, epitopes induce poor immune responses. Although the use of adjuvants can overcome this obstacle, it may raise new problems. Effective antigen delivery vehicles that can function as both antigen carriers and intrinsic adjuvants are highly desired for vaccine development. Here, we report a biepitope nanovaccine that provides complete protection in mice against H3N2 virus as well as partial protection against H1N1 virus. This vaccine (3MCD-f) consists of two conserved epitopes (matrix protein 2 ectodomain (M2e) and CDhelix), and these epitopes were presented on the surface of ferritin in a sequential tandem format. Subcutaneous immunization with 3MCD-f in the absence of adjuvant induces robust humoral and cellular immune responses. These results provide a proof of concept for the 3MCD-f nanovaccine that might be an ideal candidate for future influenza pandemics.