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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.
In Vivo Study of Anti-Influenza Effect of Silver Nanoparticles in a Mouse Model
Published in Devarajan Thangadurai, Saher Islam, Charles Oluwaseun Adetunji, Viral and Antiviral Nanomaterials, 2022
Ludmila Puchkova, Mohammad Al Farroukh, Ekaterina Ilyechova, Irina Kiseleva
In contrast, eukaryotic viruses of the families Orthomyxoviridae and Pneumoviridae, containing a membrane envelope, are highly sensitive to AgNP. Treatment of viruses with AgNP reduces their infectivity in vitro and in vivo (Xiang et al. 2011; Fatima et al. 2016; Park et al. 2018; Morris et al. 2019). This is since, upon direct contact of the IAV with AgNP, the structure of hemagglutinin and neuraminidase is disrupted by 80% and 20%, respectively. Dramatic disturbances in hemagglutinin prevent the virus from entering cells in vitro and in vivo. Another group of studies shows that AgNP-treated mice have increased resistance to influenza infection (Xiang et al. 2013; Kiseleva et al. 2020a). It is difficult to assume that intraperitoneally injected AgNP can enter the upper respiratory tract and directly contact the IAV in the upper respiratory tract. Therefore, it can be thought that the resistance of AgNP-treated mice to influenza infection is a consequence of the effect of AgNP on the mice. The mechanism of the antiviral activity of AgNP remains unexplored. There is also little information about how AgNP affects mammals. The issue under discussion is closely related to the problem of toxicity of AgNP to mammals and humans.
Order Ortervirales
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
Steel et al. (2010) generated a promising influenza vaccine candidate involving the conserved hemagglutinin (HA) stalk domain. While transient expression of the headless HA constructs alone in 293T cells was not found to result in VLP production, cotransfection with the HIV Gag-based construct did lead to the production of headless HA-containing particles. Specifically, when one of the headless HA constructs was coexpressed with a Gag-eGFP (enhanced green fluorescent protein) fusion protein, the appropriate VLPs were released into the cell culture medium (Steel et al. 2010).
Variant influenza: connecting the missing dots
Published in Expert Review of Anti-infective Therapy, 2022
Vivek Chavda, Rajashri Bezbaruah, Tutumoni Kalita, Anupam Sarma, Juti Rani Devi, Ratnali Bania, Vasso Apostolopoulos
Following virus infection of the airways, hemagglutinin interacts with sialic acid expressed in the alveolar epithelium or in the airways to facilitate viral genome endocytosis. The fusion of HA with the endosomal membrane acidifies the endosomes and activates the proton selective matrix protein-2 viral channel (M2), allowing protons to enter the viral core, causing the ribonucleoprotein complex to dissociate and be imported into the nucleus for viral replication. Virus assembly, gemmating, and scission all take place in lipid rafts in the plasma membrane [38]. Following the scission, the newly created virus was attached to the cell surface via the hemagglutinin contained in the newly formed virus and the cell surface’s sialic acid receptor. These connections are broken by NA, resulting in the release of viral offspring. As a result, the new offspring are ready to infect others via respiratory droplet release [39,40] .
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
Although there are many identification strategies available today, such as rapid influenza diagnostic tests (RIDTs). Enzyme linked immunosorbent assay (ELISA). Double immunodiffusion (DID). Complement fixation test (CF). Hemagglutinin inhibition (HI). Nucleic acid-based assays (NATs), and real time polymerase chain reaction (RT-PCR), but their specificity and time effectiveness still make them less applicable. The flu virus is a ‘form shifter.’ and new plans have to be drawn periodically to improve the vaccine for that year’s influenza outbreak. It has been challenging because of the variability of the influenza strain. Therefore, early identification is the only key available. Present viral diagnosis relies on viral nucleic acid or protein components being selectively identified. Because of specialized laboratory requirements, culture methods can be excluded. Additionally, serological testing is ineffective, requires two sufficient specimens, and takes time. Rapid tests can only detect nucleic acids or a few viral antigens and encourage practical and informative diagnosis. Moreover, RT-PCR is still regarded as costly and time consuming, and ELISA testing does not offer a high degree of sensitivity [14].
Identification of Linear Peptide Immunogens with Verified Broad-spectrum Immunogenicity from the Conserved Regions within the Hemagglutinin Stem Domain of H1N1 Influenza Virus
Published in Immunological Investigations, 2022
Shuang Li, Yongbo Qiao, Yan Xu, Pengju Li, Jiaojiao Nie, Qi Zhao, Wen Chai, Yuhua Shi, Wei Kong, Yaming Shan
Hemagglutinin (HA), a trimeric protein composed of a globular head domain and a stem domain, mediates receptor binding and membrane fusion during viral entry into the cell (Inn et al. 2014; Moon et al. 2019; Roald 2019; Wang et al. 2018). The head domain is highly mutable and variable, and therefore, current seasonal influenza vaccines that target the head domain confer resistance only against matched viruses (Boni 2008). In contrast, the stem domain contains highly conserved regions that may mediate the fusion of the influenza virus membrane with the host cell membrane (Stepanova et al. 2018; Vemula et al. 2017). Although several broadly neutralizing antibodies (bnAbs) specific for the stem region have been isolated, the anti-viral activity of many of these rely on binding non-linear or structural epitopes on the stem, which are not ideal candidates for designing immunogens (Ekiert et al. 2009; Vareckova et al. 2002).