Thiosialoside-decorated polymers use a two-step mechanism to inhibit both early and late stages of influenza virus infection

Preparation of a thioxoimidazolidin-linked sialoside BSA conjugate for the inhibition of influenza virus

A novel thioxoimidazolidin-linked sialoside bovine serum albumin (WM-BSA) conjugate was synthesized and evaluated as an inhibitor of influenza virus hemagglutinin (HA) and neuraminidase (NA). The multivalent conjugate was prepared by the attachment of thioxoimidazolidin-sialoside monomer (WM) to BSA via adipate linker. Surface plasmon resonance analysis revealed that WM-BSA exhibited potent binding to recombinant influenza HA and NA proteins, with dissociation constants in the submicromolar range. WM-BSA also demonstrated inhibitory activities in the low micromolar range against HA and NA proteins from multiple influenza strains. Investigation of cytopathic effects in infected MDCK cells indicated that WM-BSA possessed antiviral activity with EC50 values of 35-55 μM. The multivalent presentation of sialosides on the BSA scaffold significantly enhanced both the binding affinity and degree of inhibition compared to the monomeric compound WM. These results demonstrate the potential of multivalent sialoside-protein conjugate as a platform for developing novel anti-influenza agent.

A Zanamivir-protein conjugate mimicking mucin for trapping influenza virion particles and inhibiting neuraminidase activity

Influenza viruses contribute significantly to the global health burden, necessitating the development of strategies against transmission as well as effective antiviral treatments. The present study reports a biomimetic strategy inspired by the natural antiviral properties of mucins. A bovine serum albumin (BSA) conjugate decorated with the multivalent neuraminidase inhibitor Zanamivir (ZA-BSA) was synthesized using copper-free click chemistry. This synthetic pseudo-mucin exhibited potent neuraminidase inhibitory activity against several influenza strains. Virus capture and growth inhibition assays demonstrated its effective absorption of virion particles and ability to prevent viral infection in nanomolar concentrations. Investigation of the underlying antiviral mechanism of ZA-BSA revealed a dual mode of action, involving disruption of the initial stages of host-cell binding and fusion by inducing viral aggregation, followed by blocking the release of newly assembled virions by targeting neuraminidase activity. Notably, the conjugate also exhibited potent inhibitory activity against Oseltamivir-resistant neuraminidase variant comparable to the monomeric Zanamivir. These findings highlight the application of multivalent drug presentation on protein scaffold to mimic mucin adsorption of viruses, together with counteracting drug resistance. This innovative approach has potential for the creation of antiviral agents against influenza and other viral infections.

Progress in Treatment and Diagnostics of Infectious Disease with Polymers

In this era of advanced technology and innovation, infectious diseases still cause significant morbidity and mortality, which need to be addressed. Despite overwhelming success in the development of vaccines, transmittable diseases such as tuberculosis and AIDS remain unprotected, and the treatment is challenging due to frequent mutations of the pathogens. Formulations of new or existing drugs with polymeric materials have been explored as a promising new approach. Variations in shape, size, surface charge, internal morphology, and functionalization position polymer particles as a revolutionary material in healthcare. Here, an overview is provided of major diseases along with statistics on infection and death rates, focusing on polymer-based treatments and modes of action. Key issues are discussed in this review pertaining to current challenges and future perspectives.

Antiviral Compounds to Address Influenza Pandemics: An Update from 2016-2022

In recent decades, the world has gained experience of the dangerous effects of pandemic events caused by emerging respiratory viruses. In particular, annual epidemics of influenza are responsible for severe illness and deaths. Even if conventional influenza vaccines represent the most effective tool for preventing virus infections, they are not completely effective in patients with severe chronic disease and immunocompromised and new small molecules have emerged to prevent and control the influenza viruses. Thus, the attention of chemists is continuously focused on the synthesis of new antiviral drugs able to interact with the different molecular targets involved in the virus replication cycle. To date, different classes of influenza viruses inhibitors able to target neuraminidase enzyme, hemagglutinin protein, Matrix-2 (M2) protein ion channel, nucleoprotein or RNAdependent RNA polymerase have been synthesized using several synthetic strategies comprising the chemical modification of currently used drugs. The best results, in terms of inhibitory activity, are in the nanomolar range and have been obtained from the chemical modification of clinically used drugs such as Peramivir, Zanamivir, Oseltamir, Rimantadine, as well as sialylated molecules, and hydroxypyridinone derivatives. The aim of this review is to report, covering the period 2016-2022, the most recent routes related to the synthesis of effective influenza virus inhibitors.

Hierarchical assembly of foldable polymers and applications in organic optoelectronics and antibacterial or antiviral materials

Aggregation of amphiphilic polymers in block-selective solvents produces different nanostructures, which have been studied extensively for wide-ranging applications. Nevertheless, such immiscibility-driven aggregation does not endow them with the desired structural precision, predictability or surface functional group exposure, which significantly impact their functional applications. More recently, biomimetic folded structures of synthetic macromolecules (mostly oligomers) have come to the fore, but such studies have been limited to probe the secondary structures. In this article, we have collated hierarchical structures of foldamers, especially highlighting our recent contribution to the field of chain-folding regulated assembly of segmented polyurethanes (PUs) and their functional applications. A series of such PUs have been discussed, which contain a segmented hydrocarbon backbone and alternately placed pendant solvophilic groups. In either water or highly non-polar solvents (TCE, MCH), depending on the nature of the pendant group, they exhibit folded structures stabilized by intra-chain H-bonding. Hierarchical assembly of such folded chains by inter-chain H-bonding and/or π-stacking leads to the formation of well-defined nanostructures with functional applications ranging from organic optoelectronics to biomaterials. For example, a segmented PU with appended naphthalene-diimide (NDI) chromophores showed a pleated structure in MCH, which helped in organization of the NDI chromophores within π-stacking distance. Such folded polymer chains eventually produced nanotubular structures with excellent electron mobility. They also showed efficient intercalation of the pyrene (Py) donor by NDI-Py charge-transfer interaction and in this case the mixed nanotubular structure exhibited prominent room-temperature ferroelectricity. On the other hand, having cationic functionalities as the pendant groups such chain-folding regulated assembly produced unilamellar polymersomes with excellent antibacterial activity with very low minimum inhibitory concentrations (<10 μg mL-1). Replacing the pendant amine functionality with sulphate groups made these polyurethanes highly potent antiviral materials. In the absence of the alternating connectivity of the solvophobic and solvophilic segments or rigid hydrocarbon backbone, such folding propensity is destroyed, leading to structural collapse. While significant efforts have been made in correlating primary structures of wide-ranging polymers with their functional applications, this article demonstrates the direct correlation between the secondary structures of polymers and their functional properties.

Synthetic pentatrideca-valent triazolylsialoside inhibits influenza virus hemagglutinin/neuraminidase and aggregates virion particles

A synthetic multivalent hemagglutinin and neuraminidase inhibitor was developed by the conjugation of a septa-valent triazolylsialoside to bovine serum albumin using di-(N-succinimidyl) adipate. Matrixassisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) confirmed the attachment of five septa-valent sialyl lactosides to the protein backbone, resulting in a pentatrideca-valent sialyl conjugate. This pseudo-glycoprotein demonstrated a high affinity for hemagglutinin/neuraminidase as well as for the drug-resistant NA mutation on the influenza virus surface due to the cluster effect. The conjugate also exhibited potent antiviral activity against a wide range of virus strains without cytotoxicity at high concentrations. Mechanistic studies revealed that the pentatrideca-valent sialyl conjugate bound strongly to the influenza virion particles through interactions with HA/NA on the virion surfaces. The KD of the interaction was approximately 1 μM, as determined by isothermal calorimetric titration, allowing the capture and trapping of the influenza virions and preventing their further infection of host cells. These findings provide insight into the development of new antiviral agents using multivalent sialic acid clusters.

Preparation of eicosavalent triazolylsialoside-conjugated human serum albumin as a dual hemagglutinin/neuraminidase inhibitor and virion adsorbent for the prevention of influenza infection

A triazolylsialoside-human serum albumin conjugate was prepared as a multivalent hemagglutinin and neuraminidase inhibitor using a di-(N-succinimidyl) adipate strategy. Matrix-Assisted Laser Desorption/Ionization-Time of Flight-Mass Spectrometry (MALDI-TOF-MS) indicated that five tetravalent sialyl galactosides were grafted onto the protein backbone resulting in an eicosavalent triazolylsialoside-protein complex. Compared with monomeric sialic acid, molecular interaction studies showed that the synthetic pseudo-glycoprotein bound tightly not only to hemagglutinin (HA)/neuraminidase (NA) but also to mutated drug-resistant NA on the surface of the influenza virus with a dissociation constant (KD) in the 1 μM range, attributed to the cluster effect. Moreover, this glycoconjugate exhibited potent antiviral activity against a broad spectrum of virus strains and showed no cytotoxicity towards Human Umbilical Vein Endothelial Cells (HUVECs) and Madin-Darby canine kidney (MDCK) cells at high concentrations. Further mechanistic studies demonstrated this multivalent sialyl conjugate showed strong capture and trapping of influenza virions, thus disrupting the ability of the influenza virus to infect host cells. This research lays the experimental foundation for the development of new antiviral agents based on multivalent sialic acid-protein conjugates.

Nine-valent oleanolic acid conjugates as potent inhibitors blocking the entry of influenza A virus

The influenza pandemic remains a major public health challenge that endangers the lives of many vulnerable and immune-compromised individuals worldwide. The high infectivity and genetic variability of influenza virus make it particularly challenging to design effective drugs to inhibit the virus. In previous studies, we determined that oleanolic acid (OA) and its derivatives block interactions between influenza and host cells, thus endowing OA with anti-viral efficacy. Inspired by the role of cluster glycosides in the interactions between hemagglutinins (HA) and sialic acid receptors (SA), we designed and synthesized a series of OA nonamers via the CuAAC reaction, and evaluated their anti-viral activities in vitro. We determined that among these nonamers, compound 15 displayed the highest potency (IC₅₀ = 5.23 μM), equivalent to the antiviral drug oseltamivir which is routinely prescribed for influenza A virus strain A/WSN/33 (H1N1). In addition, these compounds also displayed antiviral activity against influenza B. Mechanistic experiments indicated that OA nonamers can effectively target the influenza HA protein. This study collectively demonstrates that multivalent structure-activity binding strategy is an effective method for designing influenza virus inhibitors.

Conformationally locked sugar derivatives and analogues as potential neuraminidase inhibitors

The influenza virus remains a major health concern for mankind because it tends to mutate frequently and cause high morbidity. Influenza prevention and treatment are greatly aided by the use of antivirals. One such class of antivirals is neuraminidase inhibitors (NAIs), effective against influenza viruses. A neuraminidase on the virus's surface serves a vital function in viral propogation by assisting in the release of viruses from infected host cells. Neuraminidase inhibitors are the backbone in stoping such virus propagation thus helps in the treatment of influenza viruses infections. Two NAI medicines are licensed globally: Oseltamivir (Tamiflu™) and Zanamivir (Relanza™). There are two molecules that have acquired Japanese approval recently: Peramivir and Laninamivir, whereas Laninamivir octanoate is in Phase III clinical trials. The need for novel NAIs is due to frequent mutations in viruses and the rise in resistance against existing medication. The NA inhibitors (NAIs) are designed to have (oxa)cyclohexene scaffolds (a sugar scaffold) to mimic the oxonium transition state in the enzymatic cleavage of sialic acid. This review discusses in details and comprises all such conformationally locked (oxa)cyclohexene scaffolds and their analogues which have been recently designed and synthesized as potential neuraminidase inhibitors, thus as antiviral molecules. The structure-activity relationship of such diverese molecules has also been discussed in this review.

Oseltamivir modified bovine serum albumin inhibits neuraminidase activity and accumulates virion particles to disturb influenza virus replication

The preparation of oseltamivir-bovine serum albumin conjugate (OS-BSA) for use as a multivalent influenza neuraminidase (NA) inhibitor is reported. Briefly, the oseltamivir azidohexyl ester was synthesized and covalently bound via an orthogonal attachment to bicyclononyne-modified BSA using copper-free click chemistry. Primary antiviral assays on NA protein and cellular levels showed that the synthetic multivalent OS-BSA conjugate was a more effective inhibitor than monomeric OS azidohexyl ester. Further investigation of the antiviral mechanism found that the prepared OS-BSA could not only be used as a multivalent NA inhibitor but also acted as an adsorbent for the aggregation of virion particles, contributing to the inhibition of the influenza viral replication cycle. Our findings provide insight into the antiviral mechanism of multivalent NA inhibitors and form a basis for the development of novel antiviral agents.

Antiviral Polymers: A Review

Polymers, due to their high molecular weight, tunable architecture, functionality, and buffering effect for endosomal escape, possess unique properties as a carrier or prophylactic agent in preventing pandemic outbreak of new viruses. Polymers are used as a carrier to reduce the minimum required dose, bioavailability, and therapeutic effectiveness of antiviral agents. Polymers are also used as multifunctional nanomaterials to, directly or indirectly, inhibit viral infections. Multifunctional polymers can interact directly with envelope glycoproteins on the viral surface to block fusion and entry of the virus in the host cell. Polymers can indirectly mobilize the immune system by activating macrophages and natural killer cells against the invading virus. This review covers natural and synthetic polymers that possess antiviral activity, their mechanism of action, and the effect of material properties like chemical composition, molecular weight, functional groups, and charge density on antiviral activity. Natural polymers like carrageenan, chitosan, fucoidan, and phosphorothioate oligonucleotides, and synthetic polymers like dendrimers and sialylated polymers are reviewed. This review discusses the steps in the viral replication cycle from binding to cell surface receptors to viral-cell fusion, replication, assembly, and release of the virus from the host cell that antiviral polymers interfere with to block viral infections.

Multivalent peptide dendrimers inhibit the fusion of viral-cellular membranes and the cellular NF-κB signaling pathway

The binding of the influenza A virus (IAV) to host cells is multivalent interactions between the hemagglutinin (HA) trimer and sialic acid residues on the cell surface, which present a challenge for the development of efficient antiviral drugs interfering with the entry of IAV into host cells. In this study, a number of multivalent peptide dendrimers targeting the HA2 subunit of HA to block the fusion between viral-cellular membranes have been created, of which FMOC-4-KKWK showed the lowest cytotoxicity, while in the nanomolar concentration range of antiviral effects. In addition to being active against a panel of various subtypes of influenza viruses, these dendrimers reduced the levels of NF-κB in RAW 264.7 cells and inhibited the overexpression of proinflammatory cytokines of TNF-α, IL-1β, and IL-6 that are associated with the influenza infection. Further tests in mice infected with a lethal dose of PR8 virus showed that these dendrimers increased the survival rate of mice, and reduced the viral load in the lungs. Significantly, this is the first report describing peptide dendrimers that target the HA2 subunit of IAV, differing from those using carbohydrates as ligands to block the adsorption of viruses to host cells.

Influenza A Virus Neuraminidase Inhibitors

Depending on the strain, influenza A virus causes animal, zoonotic, pandemic, or seasonal influenza with varying degrees of severity. Two surface glycoprotein spikes, hemagglutinin (HA) and neuraminidase (NA), are the most important influenza A virus antigens. NA plays an important role in the propagation of influenza virus by removing terminal sialic acid from sialyl decoy receptors and thereby facilitating the release of viruses from traps such as in mucus and on infected cells. Some NA inhibitors have become widely used drugs for treatment of influenza. However, attempts to develop effective and safe NA inhibitors that can be used for treatment of anti-NA drugs-resistant influenza viruses have continued. In this chapter, we describe the following updates on influenza A NA inhibitor development: (i) N-acetylneuraminic acid (Neu5Ac)-based derivatives, (ii) covalent NA inhibitors, (iii) sulfo-sialic acid analogs, (iv) N-acetyl-6-sulfo-β-D-glucosaminide-based inhibitors, (v) inhibitors targeting the 150-loop of group 1 NAs, (vi) conjugation inhibitors, (vii) acylhydrazone derivatives, (viii) monoclonal antibodies, (ix) PVP-I, and (x) natural products. Finally, we provide future perspectives on the next-generation anti-NA drugs.

Multivalent glycans for biological and biomedical applications

Recognition of glycans by proteins plays a crucial role in a variety of physiological processes in cells and living organisms. In addition, interactions of glycans with proteins are involved in the development of diverse diseases, such as pathogen infection, inflammation and tumor metastasis. It is well-known that multivalent glycans bind to proteins much more strongly than do their monomeric counterparts. Owing to this property, numerous multivalent glycans have been utilized to elucidate glycan-mediated biological processes and to discover glycan-based biomedical agents. In this review, we discuss recent advances (2014-2020) made in the development and biological and biomedical applications of synthetic multivalent glycans, including neoglycopeptides, neoglycoproteins, glycodendrimers, glycopolymers, glyconanoparticles and glycoliposomes. We hope this review assists researchers in the design and development of novel multivalent glycans with predictable activities.

Development and application of reverse genetic technology for the influenza virus

Influenza virus is a common virus in people's daily lives, and it has certain infectivity in humans and animals. Influenza viruses have the characteristics of a high mutation rate and wide distribution. Reverse genetic technology is primarily used to modify viruses at the DNA level through targeted modification of the virus cDNA. Genetically modified influenza viruses have a unique advantage when researching the transmission and pathogenicity of influenza. With the continuous development of oncolytic viruses in recent years, studies have found that influenza viruses also have certain oncolytic activity. Influenza viruses can specifically recognize tumor cells; activate cytotoxic T cells, NK cells, dendritic cells, etc.; and stimulate the body to produce an immune response, thereby killing tumor cells. This article will review the development and application of influenza virus reverse genetic technology.

Guanidinothiosialoside-Human Serum Albumin Conjugate Mimics mucin Barrier to Restrict Influenza Infection

A guanidinothiosialoside-human serum albumin conjugate as mucin mimic was prepared via a copper-free click reaction. Matrix-Assisted Laser Desorption/Ionization-Time of Flight-Mass Spectrometry (MALDI-TOF-MS) indicated that three sialoside groups were grafted onto the protein backbone. The synthetic glycoconjugate exhibited strong influenza virion capture and trapping capability. Further mechanistic studies showed that this neomucin bound tightly to neuraminidase on the surface of influenza virus with a dissociation constant (K_D) in the nanomolar range and had potent antiviral activity against a broad spectrum of virus strains. Most notably, the glycoconjugate acted as a biobarrier was able to protect Madin-Darby canine kidney (MDCK) cells from influenza viral infection with 50% effective concentrations (EC₅₀) in the nanomolar range and showed no cytotoxicity towards Human Umbilical Vein Endothelial Cells (HUVEC) at high concentrations. This research establishes an attractive strategy for the development of new multivalent antiviral agents based on mucin structure. Moreover, the method for the functionalization of the natural biological macromolecular scaffold with bioactive small molecules also lays the experimental foundation for potential biomedical and biomaterial applications.

Efficient chemoenzymatic synthesis of fluorinated sialyl Thomsen-Friedenreich antigens and investigation of their characteristics

A set of fluorinated sialyl-T derivatives were efficiently synthesized using one-pot multi-enzyme (OPME) chemoenzymatic approach. The P. multocida α2-3-sialyltransferase (PmST1) involved in the synthesis showed extremely flexible donor and acceptor substrate specificities. These sialosides have been successfully investigated with stability towards Clostridium perfringens sialidase substrate specificity assay using ¹H NMR spectroscopy. Hydrolysis studies monitored by ¹H NMR clearly demonstrated that the fluorine substitution obviously reduced hydrolysis rate of Clostridium perfringens sialidase. To further investigate the fluorine influence, structure-dependent variation of sialoside-lectin binding was observed for MAL and different sialoside-immobilized surfaces. Subtle changes on the ligand of carbohydrate-binding protein were distinguished by SPR. These fluorinated sialyl-T derivatives obtained are valuable probes for further biological studies or antitumor drug design.