Multivalent neuraminidase hydrolysis resistant triazole-sialoside protein conjugates as influenza-adsorbents

Triazole-sialoside tailored proteins with high hemagglutinin (HA) and neuraminidase (NA) binding affinity are prepared. Dynamic light scattering shows that these pseudo-sialylated proteins are ideal virus capture macromolecules.     

Design,Synthesis, and Biomedical Applications of Glycotripods for Targeting Trimeric Lectins

In the last decades, various efforts have been made to synthesize optimal glycotripods for targeting trimeric glycoproteins like asialoglycoprotein receptor, hemagglutinin, and langerin. All these trimeric glycoproteins have sugar binding pockets which are highly selective for a particular carbohydrate ligand. Optimized glycotripods are high affinity binders and have been used for delivering drugs or even applied as drug candidates. The selection of the tripodal base scaffold together with the length and flexibility of the linker between the scaffold and sugar residue, as important design parameters are discussed in this review.     

Apoferritin nanoparticle based dual-antigen influenza conjugate vaccine with potential cross-protective efficacy against heterosubtypic influenza virus

Ferritin nanoparticles with self-assembling properties have been widely explored as vaccine carrier by displaying foreign antigens through genetic fusion strategy. In the present work, an apoferritin (AFt) nanoparticle was tested as influenza vaccine carrier by chemically conjugating a matrix protein 2 ectodomain (M2e) antigen peptide or/and the full-length hemagglutinin (HA) antigen on the outer surface of the AFt, with heterobifunctional sSMCC or SM(PEG)24 containing PEG chain as linkers. To each AFt nanoparticle, about 30–32 M2e or 1.8 HA antigen could be coupled. The AFt-(PEG)₂₄-M2e, in which the M2e was coupled through SM(PEG)24 containing PEG chain, conferred higher protective efficacy in immunized mice than AFt-M2e did, but was less effective than AFt-(PEG)₂₄-HA. When both M2e and HA were coupled, the synthesized dual-antigen vaccine candidate AFt-(PEG)₂₄-M2e/HA elicited high level of M2e and HA antigen-specific antibodies and conferred 100% protection against lethal infection of homologous PR8 H1N1 virus strain and 70% protection against a heterologous A/FM/1/47 (FM1, H1N1) strain, which was more effective than the M2e or HA single antigen vaccine candidates. The potential cross-protective effect of the dual-antigen vaccine was further demonstrated by significant specific hemagglutination inhibition (HAI) titers in serum of the immunized mice against three other heterologous viral strains including A/Singapore/GP1908/2015 (IVR-180) H1N1, A/Anhui/1/2005 H5N1, and A/Hong Kong H3N2.     

Detection of avian influenza virus using an interferometric biosensor

An interferometric biosensor immunoassay for direct and label-less detection of avian influenza through whole virus capture on a planar optical waveguide is described. The assay response is based on index of refraction changes that occur upon binding of virus particles to unique antigen-specific (hemagglutinin) antibodies on the waveguide surface. Three virus subtypes (two H7 and one H8) in buffer solution were tested using both monoclonal and polyclonal capture antibodies. The real-time response of the antigen-antibody interaction was measured and was shown to be concentration-dependent, with detection limits as low as 0.0005 hemagglutination units per milliliter. A simple sandwich assay was shown to further increase the biosensor response.     

Theoretical analysis of binding specificity of influenza viral hemagglutinin to avian and human receptors based on the fragment molecular orbital method

The hemagglutinin (HA) protein of the influenza virus binds to the host cell receptor in the early stage of viral infection. A change in binding specificity from avian 2-3 to human 2-6 receptor is essential for optimal human-to-human transmission and pandemics. Therefore, it is important to reveal the key factors governing the binding affinity of HA-receptor complex at the molecular level for the understanding and prediction of influenza pandemics. In this work, on the basis of ab initio fragment molecular orbital (FMO) method, we have carried out the interaction energy analysis of HA-receptor complexes to quantitatively elucidate the binding specificity of HAs to avian and human receptors. To discuss the binding property of influenza HA comprehensively, a number of HAs from human H1, swine H1, avian H3 and avian H5 viruses were analyzed. We performed detailed investigations about the interaction patterns of complexes of various HAs and receptor analogues, and revealed that intra-molecular interactions between conserved residues in HA play an important role for HA-receptor binding. These results may provide a hint to understand the role of conserved acidic residues at the receptor binding site which are destabilized by the electrostatic repulsion with sialic acid. The calculated binding energies and interaction patterns between receptor and HAs are consistent with the binding specificities of each HA and thus explain the receptor binding mechanism. The calculated results in the present analysis have provided a number of viewpoints regarding the models for the HA-receptor binding specificity associated with mutated residues. Examples include the role of Glu190 and Gln226 for the binding specificity of H5 HA. Since H5 HA has not yet been adapted to human receptor and the mechanism of the specificity change is unknown, this result is helpful for the prediction of the change in receptor specificity associated with forthcoming possible pandemics.     

N-glycan analysis by CGE-LIF: profiling influenza A virus hemagglutinin N-glycosylation during vaccine production

Glycoproteins, such as monoclonal antibodies as well as recombinant and viral proteins produced in mammalian cell culture play an important role in manufacturing of many biopharmaceuticals. To ensure consisting quality of the corresponding products, glycosylation profiles have to be tightly controlled, as glycosylation affects important properties of the corresponding proteins, including bioactivity and antigenicity. This study describes the establishment of a method for analyzing N-glycosylation patterns of mammalian cell culture-derived influenza A virus glycoproteins used in vaccine manufacturing. It comprises virus purification directly from cell culture supernatant, protein isolation, deglycosylation, and clean-up steps as well as "fingerprint" analysis of N-glycan pools by CGE-LIF, using a capillary DNA-sequencer. Reproducibility studies of CGE-LIF, virus purification, and sample preparation have been performed. For demonstrating its applicability, the method was exemplarily used for monitoring batch-to-batch reproducibility in vaccine production, with respect to the glycosylation pattern of the membrane protein hemagglutinin of influenza A/PR/8/34 (H1N1) virus. This method allows characterization of variations in protein glycosylation patterns, directly by N-glycan "fingerprint" alignment.     

A computational analysis of molecular evolution for virulence genes of zoonotic novel coronavirus (COVID-19)

Zoonotic Novel coronavirus disease 2019 (COVID-19) is highly pathogenic and transmissible considered as emerging pandemic disease. The virus belongs from a large virus Coronaviridae family affect respiratory tract of animal and human likely originated from bat and homology to SARA-CoV and MERS-CoV. The virus consists of single-stranded positive genomic RNA coated by nucleocapsid protein. The rate of mutation in any virulence gene may influence the phenomenon of host radiation. We have studied the molecular evolution of selected virulence genes (HA, N, RdRP and S) of novel COVID-19. We used a site-specific comparison of synonymous (silent) and non-synonymous (amino acid altering) nucleotide substitutions. Maximum Likelihood genealogies based on differential gamma distribution rates were used for the analysis of null and alternate hypothesis. The null hypothesis was found more suitable for the analysis using Likelihood Ratio Test (LRT) method, confirming higher rate of substitution. The analysis revealed that RdRP gene had the fastest rate evolution followed by HA gene. We have also reported the new motifs for different virulence genes, which are further useful to design new detection and diagnosis kit for COVID -19.     

Improved separation of glycosylated tryptic peptides by RP-HPLC

The potential of reverse-phase high-performance liquid chromatography (RP-HPLC) for the separation of the tryptic glycopeptides of the hemagglutinin (HA) glycoprotein of influenza virus has been investigated. Excellent separation was accomplished with sample recovery of at least 90-95% by the utilization of an octadecasilyl silica stationary phase and a phosphoric acid/n-propanol solvent system. Eight glycosylated tryptic peptide classes were resolved from the HA glycoprotein of the A/USSR/90/77 virus strain.     

Molecular mechanism by which residues at position 481 and 546 of measles virus hemagglutinin protein define CD46 receptor binding using a molecular docking approach

The hemagglutinin (H) protein of measles viruses (MeV) mediates binding to the cellular receptors, CD46,human signaling lymphocyte activation molecule and nectin-4. Vaccine strains primarily contain H-proteins possessing MeV-H: Y481 and can utilize CD46. Reports suggest that a single amino acid change in MeV-H at position 481 in wild type strains renders them inefficient in utilizing CD46. The in-depth molecular mechanism by which substitutions at 481 and another reported critical residue position 546 affects CD46 binding affinity however remains elusive. We used molecular docking studies of CD46 with MeV-H possessing Y481 N/D to understand the in-depth molecular mechanism involved. It was found that loss in either of the hydrogen bond (H-bond) contacts (MeV-H:481–CD46:65, MeV-H:546–CD46:63) in the central contact region prevented efficient CD46 binding. Y481 N could form the specific H-bond, while G546S H-bond could be formed only in conjunction with Y481, revealing the significance of these residues in determining CD46 receptor binding potential. Elucidating the underlying molecular mechanism of receptor usage by the MeV has implications to understanding cellular tropism, viral pathogenesis and therapy.     

Steady State and Time-Resolved Fluorescence Studies of a Hemagglutinin from Moringa oleifera

The saccharide binding and conformational characterization of a hemagglutinin, a low molecular weight protein from the seeds of Moringa oleifera was studied using steady state and time resolved fluorescence. The lectin binds sugars LacNAc (K _a = 1380 M⁻¹) and fructose (K _a = 975 M⁻¹), as determined by the fluorescence spectroscopy. It has a single tryptophan per monomer which is exposed on the surface and is in a strong electropositive environment as revealed by quenching with iodide. Quenching of the fluorescence by acrylamide involved both static (K _s = 0.216 M⁻¹) and collisional (K _sv = 8.19 M⁻¹) components. The native protein showed two different lifetimes, τ ₁ (1.6 ns) and τ ₂ (4.36 ns) which decrease and get converted into a single one, (2.21 ns) after quenching with 0.15 M acrylamide. The bimolecular quenching constant, k _q was 7.55 × 10¹¹ M⁻¹ s⁻¹. ANS binding studies showed that the native protein has exposed hydrophobic patches which get further exposed at extreme acidic or alkaline pH. However, they get buried in the interior of the protein in presence of 1 M GdnHCl or urea.