Production and properties of adhesin-free gingipain proteinase RgpA.

The Arg-specific gingipains of Porphyromonas gingivalis RgpA and RgpB have 97% identical sequences in their catalytic domains yet their propeptides are only 76% identical. RgpA isolates as a proteinase-adhesin complex (HRgpA) which hinders direct kinetic comparison of RgpAcat as a monomer with monomeric RgpB. We tested modifications of rgpA identifying a variant that enabled us to isolate histidine-tagged monomeric RgpA (rRgpAH). Kinetic comparisons between rRgpAH and RgpB used benzoyl-L-Arg-4-nitroanilide with and without cysteine and glycylglycine acceptor molecules. With no glycylglycine, values of Km, Vmax, kcat and kcat/Km for each enzyme were similar, but with glycylglycine Km decreased, Vmax increased and kcat increased ~ twofold for RgpB but ~ sixfold for rRgpAH. The kcat/Km for rRgpAH was unchanged whereas that of RgpB more than halved. Recombinant RgpA propeptide inhibited rRgpAH and RgpB with Ki 13 nM and 15 nM Ki respectively slightly more effectively than RgpB propeptide which inhibited rRgpAH and RgpB with Ki 22 nM and 29 nM respectively (p < 0.0001); a result that may be attributable to the divergent propeptide sequences. Overall, the data for rRgpAH reflected observations previously made by others using HRgpA, indicating rRgpAH fidelity and confirming the first production and isolation of functional affinity tagged RgpA.

An ELISA-based assay for determining haemagglutinin potency in egg, cell, or recombinant protein derived influenza vaccines.

Background: The current compendial assay for haemagglutinin antigen potency in influenza vaccine is the single radial immunodiffusion (SRID) which is time consuming and can lead to delays in release of vaccine. We previously described an alternate capture and detection enzyme linked immunoassay (ELISA) that utilizes sub-type specific, sub-clade cross-reactive monoclonal antibodies (mAbs) that are haemagglutination inhibiting (HAI) and correlate with SRID. The aim of this study is to determine the applicability of ELISA across current platforms for quantitation of seasonal quadrivalent vaccine. Methods: A single mAb capture and detection ELISA was employed to quantitate hemagglutinin (HA) derived from different vaccine platforms and host organisms and compared to SRID and a polyclonal antibody based ELISA. Results: We selected mAbs that displayed appropriate characteristics for a stability indicating potency assay which reacted to avian, insect and mammalian derived HA. Qualification of the homologous mAb assay against egg and cell derived HA demonstrated performance similar to that of the SRID however, superiority in sensitivity and specificity against strains from both influenza B/Victoria and B/Yamagata lineages. Analysis of drifted strains across multiple seasons demonstrated continued utility of this approach, reducing the need to develop reagents each season. With modification of the assay, we were able to accurately measure HA from different platforms and process stages using a single calibrated reference standard. We demonstrated the accuracy of ELISA when testing vaccine formulations containing selected adjuvants at standard and higher concentrations. Accelerated stability analysis indicated a strong correlation in the rate of degradation between the homologous mAb ELISA and SRID but not with ELISA utilizing polyclonal antisera. Further, we demonstrated specificity was restricted to the trimeric and oligomeric forms of HA but not monomeric HA. Conclusion: We believe this homologous mAb ELISA is a suitable replacement for the SRID compendial assay for HA antigen quantitation and stability assessment. Identification of suitable mAbs that are applicable across multiple vaccine platforms with extended sub-type reactivity across a number of influenza seasons, indicate that this assay has broad applicability, leading to earlier availability of seasonal and pandemic vaccines without frequent replacement of polyclonal antisera that is required with SRID.

Molecular engineering of a minimal E-cadherin inhibitor protein derived from Clostridium botulinum hemagglutinin.

Hemagglutinin (HA), a nontoxic component of the botulinum neurotoxin (BoNT) complex, binds to E-cadherin and inhibits E-cadherin-mediated cell-cell adhesion. HA is a 470 kDa protein complex comprising six HA1, three HA2, and three HA3 subcomponents. Thus, to prepare recombinant full-length HA in vitro, it is necessary to reconstitute the macromolecular complex from purified HA subcomponents, which involves multiple purification steps. In this study, we developed NanoHA, a minimal E-cadherin inhibitor protein derived from Clostridium botulinum HA with a simple purification strategy needed for production. NanoHA, containing HA2 and a truncated mutant of HA3 (amino acids 380-626; termed as HA3mini), is a 47 kDa single polypeptide (one-tenth the molecular weight of full-length HA, 470 kDa) engineered with three types of modifications: (i) a short linker sequence between the C terminus of HA2 and N terminus of HA3; (ii) a chimeric complex composed of HA2 derived from the serotype C BoNT complex and HA3mini from the serotype B BoNT complex; and (iii) three amino acid substitutions from hydrophobic to hydrophilic residues on the protein surface. We demonstrated that NanoHA inhibits E-cadherin-mediated cell-cell adhesion of epithelial cells (e.g., Caco-2 and Madin-Darby canine kidney cells) and disrupts their epithelial barrier. Finally, unlike full-length HA, NanoHA can be transported from the basolateral side to adherens junctions via passive diffusion. Overall, these results indicate that the rational design of NanoHA provides a minimal E-cadherin inhibitor with a wide variety of applications as a lead molecule and for further molecular engineering.

Mechanistic dissection of antibody inhibition of influenza entry yields unexpected heterogeneity.

Neutralizing antibodies against influenza have generally been classified according to their recognition sites, with antibodies against the head domain of hemagglutinin thought to inhibit attachment and antibodies against the stalk region thought to inhibit fusion. Here, we report the development of a microfluidic assay to measure neutralization of viral entry that can clearly differentiate between effects on attachment and fusion. Testing multiple broadly neutralizing antibodies against the hemagglutinin stalk domain, we obtain a surprising result: some broadly neutralizing antibodies inhibit fusion only, while others inhibit both fusion and viral attachment. Antibodies binding the globular head domain primarily inhibit attachment but can also reduce the fusogenic capability of viral particles that nonetheless bind the receptor. These findings shed light on the unexpectedly heterogeneous mechanisms of antibody neutralization even within similar recognition sites. The assay we have developed also provides a tool to optimize vaccine design by permitting assessment of the elicited antibody response with greater mechanistic resolution.

Purification of RgpA from external outer membrane vesicles of Porphyromonas gingivalis.

INTRODUCTION: Purification of native gingipains is challenging because these proteases are frequently associated with the cell surface, which affects yield. This study aimed to purify native Arg-gingipain (RgpA) from Porphyromonas gingivalis Outer Membrane Vesicles (OMV). METHODS: Native RgpA was purified from P. gingivalis strain ATCC33277 OMV using a strategy including ultracentrifugation, sonication, and successive anionic and cationic fast protein liquid chromatography (FPLC). The presence and purity of the protease were confirmed by SDS-PAGE and detection of protease activity using fluorogenic substrates. Rat antibodies produced against the unique adhesin hemagglutinin (H1) domain of RgpA (amino acids 719-865) were titrated by ELISA at a 1:100 dilution using whole P. gingivalis lysate as an antigen and western blotting to detect a 75 kDa band corresponding to RgpA. RESULTS: Double anionic-cationic FLPC yielded prominent peaks with evident amidolytic gingipain activity of the appropriate molecular weight, as confirmed by western blotting. The final RgpA yield from 1 L of bacterial culture with colony forming unit (CFU) (Log10) 7.4 ± 0.08/mL was of 12.6% (2 mg/mL), with 3.2 FU/µg of amidolytic activity. CONCLUSIONS: This protocol allows purification of native RgpA from OMV that retains protease activity.

A cell-based multiplex immunoassay platform using fluorescent protein-barcoded reporter cell lines.

Multiplex immunoassays with acellular antigens are well-established based on solid-phase platforms such as the Luminex® technology. Cell barcoding by amine-reactive fluorescent dyes enables analogous cell-based multiplex assays, but requires multiple labeling reactions and quality checks prior to every assay. Here we describe generation of stable, fluorescent protein-barcoded reporter cell lines suitable for multiplex screening of antibody to membrane proteins. The utility of this cell-based system, with the potential of a 256-plex cell panel, is demonstrated by flow cytometry deconvolution of barcoded cell panels expressing influenza A hemagglutinin trimers, or native human CCR2 or CCR5 multi-span proteins and their epitope-defining mutants. This platform will prove useful for characterizing immunity and discovering antibodies to membrane-associated proteins.

Pre-existing immunity and vaccine history determine hemagglutinin-specific CD4 T cell and IgG response following seasonal influenza vaccination.

Effectiveness of seasonal influenza vaccination varies between individuals and might be affected by vaccination history among other factors. Here we show, by monitoring frequencies of CD4 T cells specific to the conserved hemagglutinin epitope HA118-132 and titres of IgG against the corresponding recombinant hemagglutinin protein, that antigen-specific CD4 T cell and antibody responses are closely linked to pre-existing immunity and vaccine history. Upon immunization, a strong early reaction is observed in all vaccine naïve participants and also in vaccine experienced individuals who have not received the respective seasonal vaccine in the previous year. This response is characterized by HA118-132 specific CD4 T cells with a follicular helper T cell phenotype and by ascending titers of hemagglutinin-specific antibodies from baseline to day 28 following vaccination. This trend was observed in only a proportion of those participants who received the seasonal vaccine the year preceding the study. Regardless of history, levels of pre-existing antibodies and CD127 expression on CD4 T cells at baseline were the strongest predictors of robust early response. Thus, both pre-existing immunity and vaccine history contribute to the response to seasonal influenza vaccines.

Glycan detecting tools developed from the Clostridium botulinum whole hemagglutinin complex.

Lectins are proteins with the ability to recognize and bind to specific glycan structures. These molecules play important roles in many biological systems and are actively being studied because of their ability to detect glycan biomarkers for many diseases. Hemagglutinin (HA) proteins from Clostridium botulinum type C neurotoxin complex; HA1, HA2, and HA3 are lectins that aid in the internalization of the toxin complex by binding to glycoproteins on the cell surface. HA1 mutants have been previously reported, namely HA1 W176A/D271F and HA1 N278A/Q279A which are specific to galactose (Gal)/N-acetylgalactosamine (GalNAc) and N-acetylneuraminic acid (Neu5Ac) sugars, respectively. In this study, we utilized HA1 mutants and expressed them in complex with HA2 WT and HA3 WT to produce glycan detecting tools with high binding affinity. Particularly, two types were made: Gg and Rn. Gg is an Alexa 488 conjugated lectin complex specific to Gal and GalNAc, while Rn is an Alexa 594 conjugated lectin complex specific to Neu5Ac. The specificities of these lectins were identified using a glycan microarray followed by competitive sugar inhibition experiments on cells. In addition, we confirmed that Gg and Rn staining is clearly different depending on cell type, and the staining pattern of these lectins reflects the glycans present on the cell surface as shown in enzyme treatment experiments. The availability of Gg and Rn provide us with new promising tools to study Gal, GalNAc, and Neu5Ac terminal epitopes which can aid in understanding the functional role of glycans in physiological and pathological events.

Hemagglutinin Nanoparticulate Vaccine with Controlled Photochemical Immunomodulation for Pathogenic Influenza-Specific Immunity.

Recently, viral infectious diseases, including COVID-19 and Influenza, are the subjects of major concerns worldwide. One strategy for addressing these concerns focuses on nasal vaccines, which have great potential for achieving successful immunization via safe, easy, and affordable approaches. However, conventional nasal vaccines have major limitations resulting from fast removal when pass through nasal mucosa and mucociliary clearance hindering their effectiveness. Herein a nanoparticulate vaccine (NanoVac) exhibiting photochemical immunomodulation and constituting a new self-assembled immunization system of a photoactivatable polymeric adjuvant with influenza virus hemagglutinin for efficient nasal delivery and antigen-specific immunity against pathogenic influenza viruses is described. NanoVac increases the residence period of antigens and further enhances by spatiotemporal photochemical modulation in the nasal cavity. As a consequence, photochemical immunomodulation of NanoVacs successfully induces humoral and cellular immune responses followed by stimulation of mature dendritic cells, plasma cells, memory B cells, and CD4+ and CD8+ T cells, resulting in secretion of antigen-specific immunoglobulins, cytokines, and CD8+ T cells. Notably, challenge with influenza virus after nasal immunization with NanoVacs demonstrates robust prevention of viral infection. Thus, this newly designed vaccine system can serve as a promising strategy for developing vaccines that are active against current hazardous pathogen outbreaks and pandemics.

Evaluation of Multivalent Sialylated Polyglycerols for Resistance Induction in and Broad Antiviral Activity against Influenza A Viruses.

The development of multivalent sialic acid-based inhibitors active against a variety of influenza A virus (IAV) strains has been hampered by high genetic and structural variability of the targeted viral hemagglutinin (HA). Here, we addressed this challenge by employing sialylated polyglycerols (PGs). Efficacy of prototypic PGs was restricted to a narrow spectrum of IAV strains. To understand this restriction, we selected IAV mutants resistant to a prototypic multivalent sialylated PG by serial passaging. Resistance mutations mapped to the receptor binding site of HA, which was accompanied by altered receptor binding profiles of mutant viruses as detected by glycan array analysis. Specifying the inhibitor functionalization to 2,6-α-sialyllactose (SL) and adjusting the linker yielded a rationally designed inhibitor covering an extended spectrum of inhibited IAV strains. These results highlight the importance of integrating virological data with chemical synthesis and structural data for the development of sialylated PGs toward broad anti-influenza compounds.

Influenza A Virus Hemagglutinin Is Produced in Different Disulfide-Bonded States.

Aims: Influenza A virus hemagglutinin (HA) binding to sialic acid on lung epithelial cells triggers membrane fusion and infection. Host thiol isomerases have been shown to play a role in influenza A virus infection, and we hypothesized that this role involved manipulation of disulfide bonds in HA. Results: Analysis of HA crystal structures revealed that three of the six HA disulfides occur in high-energy conformations and four of the six bonds can exist in unformed states, suggesting that the disulfide landscape of HA is generally strained and the bonds may be labile. We measured the redox state of influenza A virus HA disulfide bonds and their susceptibility to cleavage by vascular thiol isomerases. Using differential cysteine alkylation and mass spectrometry, we show that all six HA disulfide bonds exist in unformed states in ∼1 in 10 recombinant and viral surface HA molecules. Four of the six H1 and H3 HA bonds are cleaved by the vascular thiol isomerases, thioredoxin and protein disulphide isomerase, in recombinant proteins, which correlated with surface exposure of the disulfides in crystal structures. In contrast, viral surface HA disulfide bonds are impervious to five different vascular thiol isomerases. Innovation: It has been assumed that the disulfide bonds in mature HA protein are intact and inert. We show that all six HA disulfide bonds can exist in unformed states. Conclusion: These findings indicate that influenza A virus HA disulfides are naturally labile but not substrates for thiol isomerases when expressed on the viral surface.

Plant-based, adjuvant-free, potent multivalent vaccines for avian influenza virus via Lactococcus surface display.

Influenza epidemics frequently and unpredictably break out all over the world, and seriously affect the breeding industry and human activity. Inactivated and live attenuated viruses have been used as protective vaccines but exhibit high risks for biosafety. Subunit vaccines enjoy high biosafety and specificity but have a few weak points compared to inactivated virus or live attenuated virus vaccines, especially in low immunogenicity. In this study, we developed a new subunit vaccine platform for a potent, adjuvant-free, and multivalent vaccination. The ectodomains of hemagglutinins (HAs) of influenza viruses were expressed in plants as trimers (tHAs) to mimic their native forms. tHAs in plant extracts were directly used without purification for binding to inactivated Lactococcus (iLact) to produce iLact-tHAs, an antigen-carrying bacteria-like particle (BLP). tHAs BLP showed strong immune responses in mice and chickens without adjuvants. Moreover, simultaneous injection of two different antigens by two different formulas, tHAH5N6 + H9N2 BLP or a combination of tHAH5N6 BLP and tHAH9N2 BLP, led to strong immune responses to both antigens. Based on these results, we propose combinations of plant-based antigen production and BLP-based delivery as a highly potent and cost-effective platform for multivalent vaccination for subunit vaccines.

An influenza HA stalk reactive polymeric IgA antibody exhibits anti-viral function regulated by binary interaction between HA and the antibody.

IgA antibodies, which are secreted onto the mucosal surface as secretory IgA antibodies (SIgAs), play an important role in preventing influenza virus infection. A recent study reported that anti-hemagglutinin (HA) head-targeting antibodies increase anti-viral functions such as hemagglutination inhibition (HI) and virus neutralization (NT), in addition to HA binding activity (reactivity) via IgA polymerization. However, the functional properties of anti-viral IgA antibodies with mechanisms of action distinct from those of anti-HA head-targeting antibodies remain elusive. Here, we characterized the functional properties of IgG, monomeric IgA, and polymeric IgA anti-HA stalk-binding clones F11 and FI6, and B12 (a low affinity anti-HA stalk clone), as well as Fab-deficient (ΔFab) IgA antibodies. We found that IgA polymerization impacts the functional properties of anti-HA stalk antibodies. Unlike anti-HA head antibodies, the anti-viral functions of anti-HA stalk antibodies were not simply enhanced by IgA polymerization. The data suggest that two modes of binding (Fab paratope-mediated binding to the HA stalk, and IgA Fc glycan-mediated binding to the HA receptor binding site (RBS)) occur during interaction between anti-stalk HA IgA antibodies and HA. In situations where Fab paratope-mediated binding to the HA stalk exceeded IgA Fc glycan-mediated binding to HA RBS, IgA polymerization increased anti-viral functions. By contrast, when IgA Fc glycan-mediated binding to the HA RBS was dominant, anti-viral activity will fall upon IgA polymerization. In summary, the results suggest that coordination between these two independent binding modules determines whether IgA polymerization has a negative or positive effect on the anti-viral functions of anti-HA stalk IgA antibodies.

Oral delivery of liraglutide-loaded Poly-N-(2-hydroxypropyl) methacrylamide/chitosan nanoparticles: Preparation, characterization, and pharmacokinetics.

The delivery of peptides or protein drugs via the oral route has always presented a significant challenge. Here, nanoparticles for the oral delivery of liraglutide are prepared. The nanoparticles are composed of the biodegradable carrier materials chitosan and poly-N-(2-hydroxypropyl) methacrylamide (pHPMA). In addition, CSKSSDYQC (CSK) and hemagglutinin-2 (HA2) are introduced into the particles to improve the in vivo bioavailability of liraglutide. The size of the nanoparticles is less than 200 nm, and the encapsulation efficiency is approximately 80%. Compared with the subcutaneously injected liraglutide solution group (100%), the relative bioavailability of the nanoparticle group modified with CSK and HA2 reached 10.12%, which is 2.53 times that of the oral liraglutide solution group. In vivo imaging results showed that pHPMA/HA2-CSK chitosan nanoparticles (pHPMA/HA-CCNPs) are retained in the gastrointestinal tract for up to 12 h, which is beneficial for oral absorption. CSK and HA2 modified pHPMA/chitosan nanoparticles significantly improved liraglutide oral bioavailability and therefore have the potential to be applied for oral administration of peptides and proteins.

Hemagglutinin stalk-based monoclonal antibody elicits broadly reactivity against group 1 influenza A virus.

BACKGROUND: Influenza virus remains a continuous and severe threat to public health worldwide, and its prevention and treatment have always been a major international issue. Because of its ability to evade immune surveillance through rapid antigenic drift and antigenic shift, broad-spectrum vaccines seem increasingly important. METHODS: A mAb named 3C12 from an immortalized hybrid cell was generated via immunizing mice with HA2 protein from A/chicken/Anhui/BRI99/2016 (AH/BRI99/16, H9N2) generated by prokaryotic expression. Then, its broad-spectrum activity was analyzed by WB and IFA. Next, the minimal linear epitope was identified via analyzing the reaction of a series of HA truncations with 3C12. Finally, the protective effects of 3C12 were evaluated in vitro and in vivo infection experiments. RESULTS: The mAb could react with the viruses of subtypes H1, H2, H5, H8, H9, H12, H13, H16, and HA protein of H18 in group 1, but failed to react with viruses in group 2. The minimal linear epitope targeted by the mAb was 433NAELLVL439 in full length of HA and localized in the C-helix region of HA2 (residue 95-101, HA2 numbering). What's more, the mAb 3C12 inhibited H1, H2, H5, H8, H9, H12, H13 and H16 virus-replication in vitro and also has shown effectiveness in preventing and treating disease in mice challenged with lethal dose of AH/BRI99/16 (H9N2) virus in vivo. These results suggested that the broadly reactive anti-HA stem mAb 3C12 exhibited prophylactic and therapeutic efficacy. CONCLUSIONS: Here, we have demonstrated that the linear epitope identified in this study could be a novel target for developing broad-spectrum influenza diagnostics or vaccine design, and the HA2-based monoclonal antibody is indeed a promising strategy for broad-spectrum protection against seasonal and pandemic influenza viruses.

Through-grid wicking enables high-speed cryoEM specimen preparation.

Blotting times for conventional cryoEM specimen preparation complicate time-resolved studies and lead to some specimens adopting preferred orientations or denaturing at the air-water interface. Here, it is shown that solution sprayed onto one side of a holey cryoEM grid can be wicked through the grid by a glass-fiber filter held against the opposite side, often called the `back', of the grid, producing a film suitable for vitrification. This process can be completed in tens of milliseconds. Ultrasonic specimen application and through-grid wicking were combined in a high-speed specimen-preparation device that was named `Back-it-up' or BIU. The high liquid-absorption capacity of the glass fiber compared with self-wicking grids makes the method relatively insensitive to the amount of sample applied. Consequently, through-grid wicking produces large areas of ice that are suitable for cryoEM for both soluble and detergent-solubilized protein complexes. The speed of the device increases the number of views for a specimen that suffers from preferred orientations.

Genetic sequencing of influenza A (H1N1) pdm09 isolates from South India, collected between 2011 and 2015 to detect mutations affecting virulence and resistance to oseltamivir.

Background: Influenza A viruses evolve continuously and the two surface antigens, hemagglutinin (HA) and neuraminidase (NA) have been the target proteins for research as they are vital components in determining the virulence, immune effectiveness, pathogenicity, transmission and resistance. Methods: Both HA and NA (partial genes) of 45 pandemic influenza A(H1N1)pdm09 isolates were sequenced. Phylogenetic analysis was performed with reference to representative global isolates retrieved from Influenza Virus Resource (IVR), GISAID EpiFluTM and GenBank and evolutionary analyses. Nucleotide and amino acid sequences were aligned using ClustalW/ Clustal Omega/MEGA version 6 with reference to vaccine strain (A/California/07/2009). Results: All the isolates clustered along with the clade 7 virus, irrespective of the year of isolation. The study isolates exhibited 98.5% and 98.8% nucleotide homology to the reference strain A/California/07/2009(H1N1) for HA and NA, respectively. Overall, there was limited genetic diversity observed over a period of 3 years (2012-2015). Two samples collected from expired patients had D239N (D222G or D225G) mutation in HA. This mutation which is associated with dual-binding specificity of the virus has been well-correlated with severe disease outcomes. All the study isolates possessed H274 residue and 7 strains had N295S, the next most common mutation found in oseltamivir-resistant variants. Conclusion: In this study, although H274Y mutation associated with oseltamivir resistance has not been noted, significant mutations have been noted in both HA and NA genes including D239N, N295S, V106I, Q136K, N248D, V267A. In both HA and NA gene analysis, multiple mutations were found more in 2015 strains when compared to 2012 strains. Hence such accumulation of mutations has to be monitored continuously to determine the efficacy of annual flu vaccines and anti-influenza drugs.

An Apoferritin-Hemagglutinin Conjugate Vaccine with Encapsulated Nucleoprotein Antigen Peptide from Influenza Virus Confers Enhanced Cross Protection.

Naturally occurring self-assembling ferritin nanoparticles have become widely appreciated for vaccine design. In this study, an apoferritin (AFt) nanocage was used as a carrier to construct a biomimetic influenza vaccine by encapsulating a conserved internal nucleoprotein (NP) antigen peptide inside the nanocage, followed by chemically conjugating the surface antigen hemagglutinin (HA) protein on the outer surface of the AFt. Benefiting from the excellent thermal stability and thermallyassociated structural flexibility of the AFt nanocages, a novel temperature shift based encapsulation process was proposed and proved efficient for encapsulation of the NP peptides. On average, about 18 NPs were encapsulated and 1.6 HA antigens were conjugated in each of the HA-AFt+NP dual-antigen influenza vaccines. Upon immunization in mice, the HA-AFt+NP vaccine elicited both HA and NP-specific antibodies, and conferred complete protection against a lethal infection of both homologous PR8 H1N1 and heterologous A/FM/1/47 (FM1, H1N1) strains, while the HA-AFt conjugate vaccine without encapsulated NP antigen only conferred 60% protection against the FM1 H1N1 viral challenge. The potential cross-protective effect of the HA-AFt+NP vaccine was further demonstrated by significant specific hemagglutination inhibition (HAI) titers in serum of the immunized mice against heterologous A/Hong Kong/4801/2014 (H3N2) viral strain, which was about 3-fold of that induced by HA antigen and 2-fold of the HA-AFt conjugate vaccine. This biomimetic HA-AFt+NP conjugate vaccine, therefore, may represent a new strategy for developing a potential universal influenza vaccine without the need of any adjuvant, and further broaden the application of AFt nanocages in the areas of vaccine development and delivery system.

SnapShot: Influenza by the Numbers.

Influenza is one of the best-studied viruses of all time, and as such, it serves as a testbed to extend our biological knowledge to the nanoscale. Many of the key processes underlying influenza infection and our antibody response against the virus have been thoroughly investigated. This SnapShot describes these key numbers for prototypical lab-adapted strains of the human influenza A virus. To view this SnapShot, open or download the PDF.