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The Viruses
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The neuraminidase enables influenza virus to penetrate mucous secretions by virtue of its enzymatic activity. Neuraminidase also promotes the release of the virions as they bud from the cell surface. The envelope hemagglutinin serves to attach the virus to cells by binding to cell receptors. The virus then enters the cell in an endosomal vesicle. As the pH of the vesicle becomes acidic, the hemagglutinin changes conformation and allows fusion of the viral envelope with the endosomal membrane, resulting in uncoating and release of the viral nucleocapsid into the cell cytoplasm. Influenza viruses, unlike most RNA viruses, replicate in the cell nucleus rather than in the cytoplasm. The influenza virus has a negative stranded RNA, which is not translated directly by the host cell. Initiation of replication is possible because the virus encodes and packages its own RNA-dependent RNA polymerase. The viral RNA consists of eight different single-stranded segments, each coding for at least one of the major viral proteins. If two strains of influenza A virus infect the same cell, an interchange of entire genomic segments can occur (reassortment). Unlike classical genetic recombination, splicing and rejoining of the nucleic acid is not required in this process. Related influenza A viruses also infect animals of a variety of species, including pigs and many types of birds. These viral strains represent potential pools of genetic material for pathogenic human influenza strains by reassortment of genomic segments between animal and human influenza strains that infect a common host.
Chest
Published in Henry J. Woodford, Essential Geriatrics, 2022
Neuraminidase inhibitors have been developed for the treatment of influenza. They include the orally-taken oseltamivir and the inhaled zanamivir. They are thought to be able to reduce viral exit from host cells. These drugs need to be started early in infectious episodes. A Cochrane review found that oseltamivir reduced the duration of influenza symptoms by around 17 hours (95% CI 8 to 25 hours), representing a symptom duration of 6.3 days compared to seven with placebo.58 Results with zanamivir were similar. There was no reduction in hospitalisations and uncertain effects on pneumonia. Nausea and vomiting were more common with oseltamivir. Prophylaxis with these drugs, for people exposed, reduced the risk of developing symptomatic influenza.
Infections
Published in Evelyne Jacqz-Aigrain, Imti Choonara, Paediatric Clinical Pharmacology, 2021
Evelyne Jacqz-Aigrain, Imti Choonara
The first molecules used in the treatment for flu, amantadine and rimantadine, were confirmed to have had a limiting effect on the A virus, but their effectiveness was limited because of the emergence of resistant strains. The design of a new class of inhibitors for viral neuraminidase has resulted in the creation of effective antiviral compounds free of toxicity [4]. Neuraminidase is an enzyme present in the envelope of the virus that facilitates its liberation after its budding. It does this by cleaving the residues of sialic acid (Neu5 Ac) that are present in the glucoconjugates of the viral receptor at the surface of the respiratory epithelium. Neuraminidase also facilitates the diffusion of the virus through the bronchial tree by modifying the structure of the mucus, rich in muccoploysaccharides. The blocking of this enzymatique activity leads to the inhibition of the formation of lysis zones and reduces the titre of viral particles in the animal and in humans. Two of these compounds have received market authorisation in several countries: zanamivir (Relenza®) and oseltamivir (Tamiflu®) [5].
Exploring the biomedical potential of a novel modified glass ionomer cement against the pandrug-resistant oral pathogen Candida albicans SYN-01
Published in Journal of Oral Microbiology, 2023
Nessma A. El Zawawy, Samy El-Safty, El-Refaie Kenawy, Sara Ibrahim Salem, Sameh S. Ali, Yehia A.-G. Mahmoud
Neuraminidase, or sialidase, is an exoglycosidase hydrolyzing α-linkage of the terminal sialic acids of various sialoglycoconjugates in diverse organisms, including viruses and microorganisms [31]. This enzyme modifies cell-surface-located sialoglycoconjugates, which play important roles in the regulation of cell-to-cell and cell-to-molecule interactions by mediating cell recognition or adhesion processes [32]. Neuraminidases are widely expressed as virulence factors by several mucosal pathogens [33]. Surprisingly, recent evidence suggests that neuraminidase activity may influence biofilm formation [34]. Although neuraminidase production of some microorganisms was considered the main virulence factor to cause infections, the mechanism of fungal neuraminidase in dental caries is not clearly defined [35,36]. Thus, our study may be, up to the moment, the first to provide an insight into the role of fungal neuraminidase enzyme in dental infections.
An overview of advancement in aptasensors for influenza detection
Published in Expert Review of Molecular Diagnostics, 2022
Varsha Gautam, Ramesh Kumar, Vinod Kumar Jain, Suman Nagpal
Influenza virus’s structure comprise of hemagglutinin (HA) and neuraminidase (NA), which are the two glycoproteins, the former helps in the attachment of the viral body to the Sialic acid on the target cell surface whereas, the latter enables the desialylation of HA therefore, able to complete the infectious cycle by allowing virion discharge and preventing virions from aggregating due to HA[10] Influenza A, B, and C are three different strains. The pandemics caused by influenza Type A are less most prevalent in causing human diseases as compared to influenza B and C, which primarily infect animals [11]. In 1940, during an outbreak in New York City, the first influenza B strain virus was isolated [12], causing pandemics [13]. The death toll due to such pandemics has continuously been rising in countries like the U.S, African countries, India, and others, and it is causing havoc.
The use of antiviral drugs in children
Published in Journal of Chemotherapy, 2022
Marco Antonio Motisi, Agnese Tamborino, Sara Parigi, Luisa Galli, Maurizio de Martino, Elena Chiappini
Neuraminidase promotes the release of the virion from the infected host cell. Neuraminidase inhibitors are active against influenza type A and B viruses. Zanamivir is approved by the EMA for inhalation by children over the age of five. The dose is similar to that indicated for adults: two 5 mg inhalations twice daily for five days. Oseltamivir is approved by the EMA from birth age, administered twice daily for five days. Both drugs are also approved for post-exposure prevention. A systematic review involving 74 studies carried out in 2012 showed a reduction in the duration of influenza symptoms, complication rates and mortality with zanamivir and oseltamivir [10]. This success and the presence of viral strains with neuraminidase mutations that may affect their binding to oseltamivir led to the subsequent development of two more drugs in this class: peramivir, which can be administered intravenously in a single dose and is approved by the EMA for treatment in children over the age of two but not for post-exposure prophylaxis, and laninamavir, which has been approved in Japan for use in adults and children since 2010 and can be administered by inhalation in a single dose. Laninamivir has also proven effective against oseltamivir-resistant virus strains in adults [11]. It is used by inhalation as a single dose (40 mg over the age of ten and 20 mg under the age of ten), and is also approved in Japan for post-exposure prophylaxis.