H7 Hemagglutinin nanoparticles retain immunogenicity after >3 months of 25°C storage

Gold Nanoparticle-based Biosensors for Point-of-Care Diagnostics: A Review of Sensing Nanoparticle Applications and Future Prospects

Point of Care Diagnostics (POCD) is quintessential in hospitals and the healthcare sector as the secants uplift the quality of medical care and the life of a patient by facilitating quick identification of the underlying pathological condition. Nanotechnology can provide opportunities and has potential in the development of new-age sensing/diagnostic tools. Owing to extraordinary features (e.g., higher density, effective catalysis, good conduction, biocompatibility, inertness, and greater surface-to-volume ratio), gold nanoparticles (AuNPs) are frequently employed in POCT (Point-of-Care-Testing). Gold nanoparticles-based colorimetric methods are widely used in the rapid, sensitive, and selective detection of analytes/target molecules. AuNPs description is critical for their possible utility in prophylaxis, diagnostics, and treatment of an ailment. AuNPs interact with organic/inorganic target molecules to generate colorimetric shift that enables the accurate, precise, and subtle recognition of biologicals (e.g., microorganisms, cellular components, and proteins) and metal ions. This review focused on the need for AuNPs-based colorimetric application in prophylaxis, diagnostics, and treatment in healthcare and reviewed the future outlook of these AuNPs for biological applications. Different synthesis methods of AuNPs, their morphology, and characterization, including their surface functionalization, will be discussed in detail. AuNPs are very much preferable nanomaterials owing to exclusive optical, electrical, and photothermal features. AuNPsbased colorimetric biosensors are simple and possess great utility, yet these offer a robust technique to enable visual, quantitative analysis.

Designed nanoparticles elicit cross-reactive antibody responses to conserved influenza virus hemagglutinin stem epitopes

Despite the availability of seasonal vaccines and antiviral medications, influenza virus continues to be a major health concern and pandemic threat due to the continually changing antigenic regions of the major surface glycoprotein, hemagglutinin (HA). One emerging strategy for the development of more efficacious seasonal and universal influenza vaccines is structure-guided design of nanoparticles that display conserved regions of HA, such as the stem. Using the H1 HA subtype to establish proof of concept, we found that tandem copies of an alpha-helical fragment from the conserved stem region (helix-A) can be displayed on the protruding spikes structures of a capsid scaffold. The stem region of HA on these designed chimeric nanoparticles is immunogenic and the nanoparticles are biochemically robust in that heat exposure did not destroy the particles and immunogenicity was retained. Furthermore, mice vaccinated with H1-nanoparticles were protected from lethal challenge with H1N1 influenza virus. By using a nanoparticle library approach with this helix-A nanoparticle design, we show that this vaccine nanoparticle construct design could be applicable to different influenza HA subtypes. Importantly, antibodies elicited by H1, H5, and H7 nanoparticles demonstrated homosubtypic and heterosubtypic cross-reactivity binding to different HA subtypes. Also, helix-A nanoparticle immunizations were used to isolate mouse monoclonal antibodies that demonstrated heterosubtypic cross-reactivity and provided protection to mice from viral challenge via passive-transfer. This tandem helix-A nanoparticle construct represents a novel design to display several hundred copies of non-trimeric conserved HA stem epitopes on vaccine nanoparticles. This design concept provides a new approach to universal influenza vaccine development strategies and opens opportunities for the development of nanoparticles with broad coverage over many antigenically diverse influenza HA subtypes.

Chemical and biological conjugation strategies for the development of multivalent protein vaccine nanoparticles

The development of subunit vaccine platforms has been of considerable interest due to their good safety profile and ability to be adapted to new antigens, compared to other vaccine typess. Nevertheless, subunit vaccines often lack sufficient immunogenicity to fully protect against infectious diseases. A wide variety of subunit vaccines have been developed to enhance antigen immunogenicity by increasing antigen multivalency, as well as stability and delivery properties, via presentation of antigens on protein nanoparticles. Increasing multivalency can be an effective approach to provide a potent humoral immune response by more strongly engaging and clustering B cell receptors (BCRs) to induce activation, as well as increased uptake by antigen presenting cells and their subsequent T cell activation. Proper orientation of antigen on protein nanoparticles is also considered a crucial factor for enhanced BCR engagement and subsequent immune responses. Therefore, various strategies have been reported to decorate highly repetitive surfaces of protein nanoparticle scaffolds with multiple copies of antigens, arrange antigens in proper orientation, or combinations thereof. In this review, we describe different chemical bioconjugation methods, approaches for genetic fusion of recombinant antigens, biological affinity tags, and enzymatic conjugation methods to effectively present antigens on the surface of protein nanoparticle vaccine scaffolds.

Effect of Antigen Structure in Subunit Vaccine Nanoparticles on Humoral Immune Responses

Subunit vaccines offer numerous attractive features, including good safety profiles and well-defined components with highly characterized properties because they do not contain whole pathogens. However, vaccine platforms based on one or few selected antigens are often poorly immunogenic. Several advances have been made in improving the effectiveness of subunit vaccines, including nanoparticle formulation and/or co-administration with adjuvants. Desolvation of antigens into nanoparticles is one approach that has been successful in eliciting protective immune responses. Despite this advance, damage to the antigen structure by desolvation can compromise the recognition of conformational antigens by B cells and the subsequent humoral response. Here, we used ovalbumin as a model antigen to demonstrate enhanced efficacy of subunit vaccines by preserving antigen structures in nanoparticles. An altered antigen structure due to desolvation was first validated by GROMACS and circular dichroism. Desolvant-free nanoparticles with a stable ovalbumin structure were successfully synthesized by directly cross-linking ovalbumin or using ammonium sulfate to form nanoclusters. Alternatively, desolvated OVA nanoparticles were coated with a layer of OVA after desolvation. Vaccination with salt-precipitated nanoparticles increased OVA-specific IgG titers 4.2- and 22-fold compared to the desolvated and coated nanoparticles, respectively. In addition, enhanced affinity maturation by both salt precipitated and coated nanoparticles was displayed in contrast to desolvated nanoparticles. These results demonstrate both that salt-precipitated antigen nanoparticles are a potential new vaccine platform with significantly improved humoral immunity and a functional value of preserving antigen structures in vaccine nanoparticle design.

Monophosphoryl lipid A-adjuvanted nucleoprotein-neuraminidase nanoparticles improve immune protection against divergent influenza viruses

Universal influenza vaccines are urgently needed to prevent recurrent influenza epidemics and inevitable pandemics. We generated double-layered protein nanoparticles incorporating two conserved influenza antigens-nucleoprotein and neuraminidase-through a two-step desolvation-crosslinking method. These protein nanoparticles displayed immunostimulatory properties to antigen-presenting cells by promoting inflammatory cytokine (IL-6 and TNF-α) secretion from JAWS II dendric cells. The nanoparticle immunization induced significant antigen-specific humoral and cellular responses, including antigen-binding and neutralizing antibodies, antibody- and cytokine (IFN-γ and IL-4)-secreting cells, and NP147-155 tetramer-specific cytotoxic T lymphocyte (CTL) responses. Co-administration of monophosphoryl lipid A (MPLA, a toll-like receptor 4 agonist) with the protein nanoparticles further improved immune responses and conferred heterologous and heterosubtypic influenza protection. The MPLA-adjuvanted nanoparticles reduced lung inflammation post-infection. The results demonstrated that the combination of MPLA and conserved protein nanoparticles could be developed into an improved universal influenza vaccine strategy.

Skin vaccination with dissolvable microneedle patches incorporating influenza neuraminidase and flagellin protein nanoparticles induces broad immune protection against multiple influenza viruses

We generated self-adjuvanted protein nanoparticles of conserved influenza antigens and immunized mice via skin vaccination with dissolvable microneedle patches (MNPs) to increase the strength and breadth of immune responses. We produced M2e nanoparticles via ethanol desolvation, and double-layered NA1/M2e (shell/core), NA1-FliC/M2e, NA2/M2e, and NA2-FliC/M2e protein nanoparticles by chemically crosslinking influenza NA and flagellin (FliC) onto the surfaces of the M2e nanoparticles. The resulting nanoparticles retained FliC TLR5 innate signaling activity and significantly increased antigen-uptake and dendritic cell maturation in vitro. We incorporated the nanoparticles into MNPs for skin vaccination in mice. The nanoparticle MNPs significantly increased M2e and NA-specific antibody levels, the numbers of germinal center B cells, and IL-4 positive splenocytes. Double-layered nanoparticle MNP skin vaccination protected mice against homologous and heterosubtypic influenza viruses. Our results demonstrated that MNP skin vaccination of NA-FliC/M2e nanoparticles could be developed into a standalone or synergistic component of a universal influenza vaccine strategy.

Measuring the concentration of protein nanoparticles synthesized by desolvation method: Comparison of Bradford assay, BCA assay, hydrolysis/UV spectroscopy and gravimetric analysis

The desolvation technique is one of the most popular methods for preparing protein nanoparticles for medicine, biotechnology, and food applications. We fabricated 11 batches of BSA nanoparticles and 2 batches of gelatin nanoparticles by desolvation method. BSA nanoparticles from 2 batches were cross-linked by heating at +70 °C for 2 h; other nanoparticles were stabilized by glutaraldehyde. We compared several analytical approaches to measuring their concentration: gravimetric analysis, bicinchoninic acid assay, Bradford assay, and alkaline hydrolysis combined with UV spectroscopy. We revealed that the cross-linking degree and method of cross-linking affect both Bradford and BCA assay. Direct measurement of protein concentration in the suspension of purified nanoparticles by dye-binding assays can lead to significant (up to 50-60%) underestimation of nanoparticle concentration. Quantification of non-desolvated protein (indirect method) is affected by the presence of small nanoparticles in supernatants and can be inaccurate when the yield of desolvation is low. The reaction of cross-linker with protein changes UV absorbance of the latter. Therefore pure protein solution is an inappropriate calibrator when applying UV spectroscopy for the determination of nanoparticle concentration. Our recommendation is to determine the concentration of protein nanoparticles by at least two different methods, including gravimetric analysis.

Protein and Peptide Nanocluster Vaccines

Recombinant protein- and peptide-based vaccines can deliver large amounts of specific antigens for tailored immune responses. One class of these are protein and peptide nanoclusters (PNCs), which are made entirely from the crosslinked antigen. PNCs leverage the inherent immunogenicity of nanoparticulate antigens while minimizing the use of excipients normally used to create them. In this chapter, we discuss PNC fabrication methods, immunostimulatory properties of nanoclusters observed in vitro and in vivo, and protective benefits of PNC vaccines against influenza and cancer mouse models. We conclude with an outlook on future studies of PNCs and PNC design strategies, as well as their use in future vaccine formulations.

Double-Layered M2e-NA Protein Nanoparticle Immunization Induces Broad Cross-Protection against Different Influenza Viruses in Mice

The development of a universal influenza vaccine is an ideal strategy to eliminate public health threats from influenza epidemics and pandemics. This ultimate goal is restricted by the low immunogenicity of conserved influenza epitopes. Layered protein nanoparticles composed of well-designed conserved influenza structures have shown improved immunogenicity with new physical and biochemical features. Herein, structure-stabilized influenza matrix protein 2 ectodomain (M2e) and M2e-neuraminidase fusion (M2e-NA) recombinant proteins are generated and M2e protein nanoparticles and double-layered M2e-NA protein nanoparticles are produced by ethanol desolvation and chemical crosslinking. Immunizations with these protein nanoparticles induce immune protection against different viruses of homologous and heterosubtypic NA in mice. Double-layered M2e-NA protein nanoparticles induce higher levels of humoral and cellular responses compared with their comprising protein mixture or M2e nanoparticles. Strong cytotoxic T cell responses are induced in the layered M2e-NA protein nanoparticle groups. Antibody responses contribute to the heterosubtypic NA immune protection. The protective immunity is long lasting. These results demonstrate that double-layered protein nanoparticles containing structure-stabilized M2e and NA can be developed into a universal influenza vaccine or a synergistic component of such vaccines. Layered protein nanoparticles can be a general vaccine platform for different pathogens.