Gangliosides are not essential for influenza virus infection

α2,3-Linked Sialic Acids Are the Potential Attachment Receptor for Shaan Virus Infection in MARC-145 Cells

Shaan virus (ShaV), a novel species of the genus Jeilongvirus, family Paramyxoviridae, was isolated from an insectivore bat (Miniopterus schreibersii) in Korea in 2016. ShaV particles contain a hemagglutinin-neuraminidase (HN) glycoprotein in their envelope that allows the virus to target cells. Typically, diverse paramyxoviruses with HN glycoprotein are reported to interact predominantly with sialic acids, but there are no studies of receptors for ShaV. In this study, the identification of potential receptors for ShaV was demonstrated using sialidase treatments, glycan microarray, magnetic bead-based virus binding assay, and neuraminidase inhibitor treatments. Pretreatment of MARC-145 cells with sialidase, which cleaves α2,3-linked sialic acids, showed higher inhibition of viral infection than α2,6-linked-specific sialidase. These data were supported by the binding of ShaV to predominantly α2,3-linked sialylated glycans in the screening of sialyl linkage patterns through glycan microarray. To further confirm the direct interaction between ShaV and α2,3-linked sialic acids, ShaV was incubated with α2,3- or α2,6-linked sialylated glycans conjugated to magnetic beads, and binding signals were detected only for α2,3-linked sialylated glycans. In addition, the potential of sialic acids as a receptor was demonstrated by the viral replication inhibitory effect of the neuraminidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminicacid (DANA) in the mature virion release steps. Collectively, these results support that α2,3-linked sialic acids are the potential receptor for ShaV infection in MARC-145 cells. IMPORTANCE Bats host major mammalian paramyxoviruses, and novel paramyxoviruses are increasingly being reported around the world. Shaan virus (ShaV), from the genus Jeilongvirus, family Paramyxoviridae, has a potential attachment glycoprotein, HN. Here, we identify that ShaV binds to sialic acid and demonstrate that α2,3-linked sialic acids are the potential receptor for ShaV infection. The presented data regarding ShaV receptor specificity will enable studies into the viral tropism for the host and contribute to the development of new antiviral strategies targeting viral receptors.

Functionality of the putative surface glycoproteins of the Wuhan spiny eel influenza virus

A panel of influenza virus-like sequences were recently documented in fish and amphibians. Of these, the Wuhan spiny eel influenza virus (WSEIV) was found to phylogenetically cluster with influenza B viruses as a sister clade. Influenza B viruses have been documented to circulate only in humans, with certain virus isolates found in harbor seals. It is therefore interesting that a similar virus was potentially found in fish. Here we characterize the putative hemagglutinin (HA) and neuraminidase (NA) surface glycoproteins of the WSEIV. Functionally, we show that the WSEIV NA-like protein has sialidase activity comparable to B/Malaysia/2506/2004 influenza B virus NA, making it a bona fide neuraminidase that is sensitive to NA inhibitors. We tested the functionality of the HA by addressing the receptor specificity, stability, preferential airway protease cleavage, and fusogenicity. We show highly specific binding to monosialic ganglioside 2 (GM2) and fusogenicity at a range of different pH conditions. In addition, we found limited antigenic conservation of the WSEIV HA and NA relative to the B/Malaysia/2506/2004 virus HA and NA. In summary, we perform a functional and antigenic characterization of the glycoproteins of WSEIV to assess if it is indeed a bona fide influenza virus potentially circulating in ray-finned fish.

A Dynamic, Supramolecular View on the Multivalent Interaction between Influenza Virus and Host Cell

Understanding how influenza viruses traverse the mucus and recognize host cells is critical for evaluating their zoonotic potential, and for prevention and treatment of the disease. The surface of the influenza A virus is covered with the receptor-binding protein hemagglutinin and the receptor-cleaving enzyme neuraminidase, which jointly control the interactions between the virus and the host cell. These proteins are organized in closely spaced trimers and tetramers to facilitate multivalent interactions with sialic acid-terminated glycans. This review shows that the individually weak multivalent interactions of influenza viruses allow superselective binding, virus-induced recruitment of receptors, and the formation of dynamic complexes that facilitate molecular walking. Techniques to measure the avidity and receptor specificity of influenza viruses are reviewed, and the pivotal role of multivalent interactions with their emergent properties in crossing the mucus and entering host cells is discussed. A model is proposed for the initiation of cell entry through virus-induced receptor clustering. The multivalent interactions of influenza viruses are maintained in a dynamic regime by a functional balance between binding and cleaving.

Influenza virus entry via the GM3 ganglioside-mediated platelet-derived growth factor receptor β signalling pathway

The possible resistance of influenza virus against existing antiviral drugs calls for new therapeutic concepts. One appealing strategy is to inhibit virus entry, in particular at the stage of internalization. This requires a better understanding of virus-host interactions during the entry process, including the role of receptor tyrosine kinases (RTKs). To search for cellular targets, we evaluated a panel of 276 protein kinase inhibitors in a multicycle antiviral assay in Madin-Darby canine kidney cells. The RTK inhibitor Ki8751 displayed robust anti-influenza A and B virus activity and was selected for mechanistic investigations. Ki8751 efficiently disrupted the endocytic process of influenza virus in different cell lines carrying platelet-derived growth factor receptor β (PDGFRβ), an RTK that is known to act at GM3 ganglioside-positive lipid rafts. The more efficient virus entry in CHO-K1 cells compared to the wild-type ancestor (CHO-wt) cells indicated a positive effect of GM3, which is abundant in CHO-K1 but not in CHO-wt cells. Entering virus localized to GM3-positive lipid rafts and the PDGFRβ-containing endosomal compartment. PDGFRβ/GM3-dependent virus internalization involved PDGFRβ phosphorylation, which was potently inhibited by Ki8751, and desialylation of activated PDGFRβ by the viral neuraminidase. Virus uptake coincided with strong activation of the Raf/MEK/Erk cascade, but not of PI3K/Akt or phospholipase C-γ. We conclude that influenza virus efficiently hijacks the GM3-enhanced PDGFRβ signalling pathway for cell penetration, providing an opportunity for host cell-targeting antiviral intervention.

Unraveling the role of membrane microdomains during microbial infections

Infectious diseases pose major socioeconomic and health-related threats to millions of people across the globe. Strategies to combat infectious diseases derive from our understanding of the complex interactions between the host and specific bacterial, viral, and fungal pathogens. Lipid rafts are membrane microdomains that play important role in life cycle of microbes. Interaction of microbial pathogens with host membrane rafts influences not only their initial colonization but also their spread and the induction of inflammation. Therefore, intervention strategies aimed at modulating the assembly of membrane rafts and/or regulating raft-directed signaling pathways are attractive approaches for the. management of infectious diseases. The current review discusses the latest advances in terms of techniques used to study the role of membrane microdomains in various pathological conditions and provides updated information regarding the role of membrane rafts during bacterial, viral and fungal infections.

Avian Influenza A Viruses: Evolution and Zoonotic Infection

Although efficient human-to-human transmission of avian influenza virus has yet to be seen, in the past two decades avian-to-human transmission of influenza A viruses has been reported. Influenza A/H5N1, in particular, has repeatedly caused human infections associated with high mortality, and since 1998 the virus has evolved into many clades of variants with significant antigenic diversity. In 2013, three (A/H7N9, A/H6N1, and A/H10N8) novel avian influenza viruses (AIVs) breached the animal-human host species barrier in Asia. In humans, roughly 35% of A/H7N9-infected patients succumbed to the zoonotic infection, and two of three A/H10N8 human infections were also lethal; however, neither of these viruses cause influenza-like symptoms in poultry. While most of these cases were associated with direct contact with infected poultry, some involved sustained human-to-human transmission. Thus, these events elicited concern regarding potential AIV pandemics. This article reviews the human incursions associated with AIV variants and the potential role of pigs as an intermediate host that may hasten AIV evolution. In addition, we discuss the known influenza A virus virulence and transmission factors and their evaluation in animal models. With the growing number of human AIV infections, constant vigilance for the emergence of novel viruses is of utmost importance. In addition, careful characterization and pathobiological assessment of these novel variants will help to identify strains of particular concern for future pandemics.

α2-3- and α2-6- N-linked sialic acids allow efficient interaction of Newcastle Disease Virus with target cells

Receptor recognition and binding is the first step in the viral cycle. It has been established that Newcastle Disease Virus (NDV) interacts with sialylated molecules such as gangliosides and glycoproteins at the cell surface. Nevertheless, the specific receptor(s) that mediate virus entry are not well known. We have analysed the role of the sialic acid linkage in the early steps of the viral infection cycle. Pretreatment of ELL-0 cells with both α2,3 and α2,6 specific sialidases led to the inhibition of NDV binding, fusion and infectivity, which were restored after α2,3(N)- and α2,6(N)-sialyltransferase incubation. Moreover, α2,6(N)-sialyltransferases also restored NDV activities in α2-6-linked sialic acid deficient cells. Competition with α2-6 sialic acid-binding lectins led to a reduction in the three NDV activities (binding, fusion and infectivity) suggesting a role for α2-6- linked sialic acid in NDV entry. We conclude that both α2-3- and α2-6- linked sialic acid containing glycoconjugates may be used for NDV infection. NDV was able to efficiently bind, fuse and infect the ganglioside-deficient cell line GM95 to a similar extent to that of its parental MEB4, suggesting that gangliosides are not essential for NDV binding, fusion and infectivity. Nevertheless, the fact that the interaction of NDV with cells deficient in N-glycoprotein expression such as Lec1 was less efficient prompted us to conclude that NDV requires N-linked glycoproteins for efficient attachment and entry into the host cell.

Function of membrane rafts in viral lifecycles and host cellular response

Membrane rafts are small (10–200 nm) sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts play an important role in viral infection cycles and viral virulence. Viruses are divided into four main classes, enveloped DNA virus, enveloped RNA virus, nonenveloped DNA virus, and nonenveloped RNA virus. General virus infection cycle is also classified into two sections, the early stage (entry process) and the late stage (assembly, budding, and release processes of virus particles). In the viral cycle, membrane rafts act as a scaffold of many cellular signal transductions, which are associated with symptoms caused by viral infections. In this paper, we describe the functions of membrane rafts in viral lifecycles and host cellular response according to each virus classification, each stage of the virus lifecycle, and each virus-induced signal transduction.

No evidence of a link between influenza vaccines and Guillain-Barre syndrome-associated antiganglioside antibodies

Please cite this paper as: Wang et al. (2011) No evidence of a link between influenza vaccines and Guillain–Barre syndrome–associated antiganglioside antibodies. Influenza and Other Respiratory Viruses 6(3), 159–166.

Background  Guillain–Barre syndrome (GBS) is a rare autoimmune disease characterized by acute, progressive peripheral neuropathy and is commonly associated with the presence of antiganglioside antibodies. Previously, influenza vaccination was linked with the increased incidence of GBS; however, whether antiganglioside antibodies are subsequently induced remains unresolved.

Methods  Sera from human subjects vaccinated with seasonal influenza vaccines from the 2007–2008, 2008–2009, or 1976–1977 influenza seasons were screened for the induction of immunity to influenza and the presence of antiganglioside antibodies pre‐ and post‐vaccination. Likewise, sera from mice vaccinated with seasonal influenza vaccines (1988–1989, 2007–2008) or “swine flu” pandemic vaccines (1976, 2009) were assessed in the same manner. Viruses were also screened for cross‐reacting ganglioside epitopes.

Results  Antiganglioside antibodies were found to recognize influenza viruses; this reactivity correlated with virus glycosylation. Antibodies to influenza viruses were detected in human and mouse sera, but the prevalence of antiganglioside antibodies was extremely low.

Conclusions  Although the correlation between antiganglioside antibody cross‐reactivity and glycosylation of viruses suggests the role of shared carbohydrate epitopes, no correlation was observed between hemagglutinin‐inhibition titers and the induction of antiganglioside antibodies after influenza vaccination.

Implications for lipids during replication of enveloped viruses

Enveloped viruses, which include many medically important viruses such as human immunodeficiency virus, influenza virus and hepatitis C virus, are intracellular parasites that acquire lipid envelopes from their host cells. Success of replication is intimately linked to their ability to hijack host cell mechanisms, particularly those related to membrane dynamics and lipid metabolism. Despite recent progress, our knowledge of lipid mediated virus-host interactions remains highly incomplete. In addition, diverse experimental systems are used to study different stages of virus replication thus complicating comparisons. This review aims to present a unifying view of the widely diverse strategies used by enveloped viruses at distinct stages of their replication cycles.

Anti-ganglioside antibody induction by swine (A/NJ/1976/H1N1) and other influenza vaccines: insights into vaccine-associated Guillain-Barré syndrome

BACKGROUND

Receipt of an A/NJ/1976/H1N1 "swine flu" vaccine in 1976, unlike receipt of influenza vaccines used in subsequent years, was strongly associated with the development of the neurologic disorder Guillain-Barré syndrome (GBS). Anti-ganglioside antibodies (e.g., anti-GM(1)) are associated with the development of GBS, and we hypothesized that the swine flu vaccine contained contaminating moieties (such as Campylobacter jejuni antigens that mimic human gangliosides or other vaccine components) that elicited an anti-GM(1) antibody response in susceptible recipients.

METHODS

Surviving samples of monovalent and bivalent 1976 vaccine, comprising those from 3 manufacturers and 11 lot numbers, along with several contemporary vaccines were tested for hemagglutinin (HA) activity, the presence of Campylobacter DNA, and the ability to induce anti-Campylobacter and anti-GM(1) antibodies after inoculation into C3H/HeN mice.

RESULTS

We found that, although C. jejuni was not detected in 1976 swine flu vaccines, these vaccines induced anti-GM(1) antibodies in mice, as did vaccines from 1991-1992 and 2004-2005. Preliminary studies suggest that the influenza HA induces anti-GM(1) antibodies.

CONCLUSIONS

Influenza vaccines contain structures that can induce anti-GM(1) antibodies after inoculation into mice. Further research into influenza vaccine components that elicit anti-ganglioside responses and the role played by these antibodies (if any) in vaccine-associated GBS is warranted.

Effective replication of human influenza viruses in mice lacking a major alpha2,6 sialyltransferase

The hemagglutinins of influenza viruses isolated from humans typically prefer binding to sialic acid in an alpha2,6 linkage. Presumably, the virus uses the presence of these receptors on the respiratory tract to gain entrance into the host cell. The ST6Gal I sialyltransferase knock-out mouse lacks the main enzyme necessary for the attachment of alpha2,6 sialic acid to N-linked glycoproteins on the cell surface. Yet even in the absence of detectable alpha2,6 sialic acid in the mouse respiratory tract, human influenza viruses can still infect these mice and grow to similar titers in the lung and trachea as compared to wild-type animals. This work demonstrates that the presence of a major alpha2,6 sialic acid on N-linked glycoproteins is not essential for human influenza virus infection in mice.

Virus infection and lipid rafts

Virus entry, assembly, and budding are important processes in the replication cycle of a virus. Viruses are dependent on host living cells for their replication. Viruses use the proliferative mechanism of host cells for replication of viral components. Lipid rafts, specific membrane microdomains play a critical role in virus replication because localizing and concentrating viral components in the microdomains for entry, assembly, and budding of various types of virus. In this review, we describe the involvement of membrane lipid rafts in the virus replication cycle with our current findings for understanding the role of membrane lipid rafts in virus infection.

Entry of influenza virus

As a major pathogen of human and certain animal species, influenza virus causes wide spread and potentially devastating disease. To initiate infection, the virus first binds to cellular receptors comprising either -(2,3 ) or -(2,6) linked sialic acid. Recent advances in our understanding of the influenza virus receptor and viral host species involved have shed light on the molecular mechanism of how influenza virus transmits across species and adapts to a new host. Following receptor binding, influenza viruses are internalized through multiple endocytic pathways, including both clathrin- and non-clathrin-dependent routes, which have recently been visualized at single viral particle level. The viral envelope then fuses with the endosomal membrane in a low pH-dependent manner and the viral genome is released into the cytosol, followed by further transport to the nucleus where genome replication occurs.