title: Structure Determination of Human Parainfluenza Virus Type 1 Haemagglutinin-Neuraminidase and Antiviral Drug Design
Creators: name: Tan, Olivia C
Publisher: name: Griffith University
Year: 2023
Subjects: subject: hPIV-1 HN
subject: x-ray crystallography
subject: antiviral drug design
subject: structure determination

description: Viruses are a major global health issue and exert a substantial health and economic burden on society. The Paramyxoviridae family is comprised of viruses that are capable of causing serious illness in humans and includes respiratory pathogens such as, human parainfluenza viruses (hPIVs). This particular group of viruses are known to cause a range of upper and lower respiratory tract illnesses that predominantly affect infants, young children, elderly populations and immunocompromised individuals. There are four types of hPIVs and among them, human parainfluenza virus type 1 (hPIV-1), in particular, is a primary cause of croup in children under five years of age. Furthermore, despite ongoing research, there are no licensed drugs nor vaccines commercially available to treat hPIV-1 infections to date. Current treatment options are limited to supportive care and corticosteroids for alleviating symptoms of infection. Therefore, it is imperative to investigate new strategies to develop novel antiviral drugs to combat this virus. Current research efforts are focused on haemagglutinin-neuraminidase (HN), a key glycoprotein on viral surface, that is involved in three essential roles in the virus lifecycle. The HN protein is responsible for: 1) facilitating viral attachment by binding to α2,3 N-linked terminal sialic acids on host-cell receptors, 2) activating the fusion cascade mechanisms for viral entry and 3) initiating the release of newly formed virions by cleaving off sialic acid moieties on the virion progeny glycoproteins as well as the infected host-cell surface. Therefore, the multiple functionalities of the HN protein highlight its importance as a target for drug development. The work presented in this thesis is focused on the structure determination and characterisation of hPIV-1 HN to guide the design of anti-parainfluenza virus inhibitors. Here, we present the first hPIV-1 HN crystal structure in its ligand-free and complexed states and describe the strategies used to achieve these outcomes. We explored a variety of methods to crystallise the hPIV-1 HN protein for X-ray analysis and subsequent structure determination. To date, the crystal structure of hPIV-1 HN has not been solved, therefore, obtaining its crystal structure was a major outcome that allowed us to gain valuable insights into the distinct structural characteristics of the protein. Additionally, we investigated the dynamics of the hPIV-1 HN active site in complex with a potent inhibitor and characterised important protein-ligand interactions to guide future drug development endeavours. Furthermore, we explored additional avenues for novel drug design and identified several chemical scaffolds with potential to advance towards the hit-to-lead optimisation pipeline. We utilised the fragment-based drug discovery approach followed by X-ray crystallography for subsequent structural analysis. The combination of these strategies played a central role in the identification of an extended pocket within the C5-binding domain in the active site, which can be targeted to improve the design of current inhibitors. Overall, the key findings described in this thesis have provided the first insight into the hPIV-1 HN crystal structure and established a solid foundation to base future antiviral drug design strategies.