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Title: Functionalisation of gold nanoparticles with short synthetic peptides and their potential therapeutic use against the influenza virus infections
Author: Alghrair, Zaid Khalaf
ISNI:       0000 0004 7658 1649
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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Influenza ('flu) virus is a major health concern for humans and animals. The mode of transmission is predominantly by the respiratory route. 'Flu infection occurs seasonally and can cause global pandemics, with the most recent 'flu pandemic, the 2009 H1N1 Swine 'flu, resulted in more than 18,000 deaths worldwide. 'Flu poses major challenges, because the virus has an RNA genome, which has a high potential to recombine and produce new strains through a mechanism termed re-assortment. The constant appearance of new strains requires new vaccines; the time between virus identification and the deployment of the vaccine is an important challenge in 'flu control. Therefore, anti-influenza drugs, which can control the virus infection irrespective the virus strain are important. Such antivirals are usually cheaper compared to vaccination and can be self-administered. However, drug treatment is usually less effective over time due to the rapid evolution of the virus genome and the acquisition by the virus of drug resistance. The approval of the first peptide anti-viral, Enfuvirtidie, by the Food and Drug Administration (USA) illustrates the potential of peptides to combat infectious diseases. 'Flupep', a peptide originally identified as a mimic of the suppressor of cytokine signalling (SOCS) protein, was subsequently found to inhibit the infectivity of influenza A virus, including the H1N1 subtype. To understand how Flupep exerts its effects, it has been incorporated into the ligand shell of gold nanoparticles. The gold nanoparticles provide a very sensitive probe that can be detected optically, and are a model for a potential future nanoparticle formulations. The results demonstrate that the nanoparticle-Flupep conjugates have enhanced anti-'flu virus activity compared to free peptide in a cell-based plaque assay. Nanoparticle-Flupep conjugates do not bind to influenza virus in vitro. However, the nanoparticle-Flupep conjugates bind to cells and, following binding, remain cell-associated and able to inhibit 'flu virus infectivity. The cell bound nanoparticle-Flupep conjugates may be removed by washing the cells with 1 M NaCl, indicating that ionic interactions are likely to underpin their binding to cells. Treatment of cells with heparinases I and II neuraminidases, but not chondroitinase ABC reduces binding of Flupep-nanoparticle conjugates, indicating that heparan sulfate and sialic acid are major cellular binding sites of the peptide. Since the Flupep sequence has a basic C-terminus likely to be involved in binding these polysaccharides, heparan sulfate binding sequences from growth factors were added to the FluPep sequence. These additions enhanced its anti-viral activity, showing that engineering extracellular matrix binding of peptides inhibiting 'flu virus is a route to increasing their effective potency. Overall the thesis demonstrates that Flupep, contrary to published work, exerts its anti-viral effects by binding to cells, and FluPep binding sites include heparan sulfate and sialic acid. Other binding sites are likely involved, since the IC50 of Flupep and its derivatives is orders of magnitude lower than the likely affinity of the peptides for polysaccharide binding sites. Thus, the hypothesis is put forward that Flupep interacts with one of more dual receptor systems consisting of polysaccharide and protein(s) and that this underlies the efficacy and mode of action of the peptide.
Supervisor: Fernig, David ; Ebrahimi, Bahram Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral