The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize / published_or_final_version / abstract / toc / Microbiology / Doctoral / Doctor of Philosophy

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Influenza virus is a globally significant infectious agent with the potential to cause catastrophic pandemic outbreaks. Present treatment of influenza infections is restricted to only four anti-viral drugs, but there are increasing global reports of anti-viral resistance in several seasonal strains and also the 2009 pandemic swine-origin influenza virus H1N1. Possible future pandemic outbreaks, emerging new strains and drug resistance underscore the need to understand this complex virus and its pathogenicity with the goal that novel targets can be uncovered for future therapeutic development. Extensive lung tissue damage during influenza virus infection is proposed to contribute to the development of aberrant host immune responses. Strong evidence now demonstrates the significance of the cellular death pathway in promoting efficient influenza virus replication and disease progression. Viruses rely heavily on the machinery of their host for productive replication, which is also an Achilles’ heel that could be targeted for treatment. In pursuit of unraveling the complex nature of influenza virus replication, I carried out a global shRNA screen to identify specific host factors and signaling pathways that are involved in influenza-induced cell death and replication. In this study I identified 138 genes required for influenza viruses to induce infected host cell death. These genes were found to be involved in Protein Kinase A, NF-kB and PI3K signaling cascades. These signaling pathways are well known regulators of cell death and survival, which suggests influenza viruses may carefully regulate these pathways to reach a balance that suit their requirements for efficient proliferation, eventually at the cost of the host cell. I chose five candidate genes—BAD, MxB, TNFSF12-13,TNFSF13, and USP47—that were associated with apoptosis and the major signaling pathways determined in my network analysis to further verify the genome-wide screen as well as elucidate the role of these potentially novel host factors in influenza virus replication. I show in my study that influenza virus-induced cytopathology and cell death are considerably inhibited in BAD knockdown cells and both virus replication and viral protein production also are dramatically reduced. I also report here that MxB depletion protected cells from virus-mediated cytopathology and resulted in significant inhibition of influenza virus replication for H1N1 and H3N2 subtypes. Additionally, I report that TNFSF12-13, TFNSF13, and USP47, similarly, are required for efficient influenza virus replication and induction of cell death. Depletion of these proteins resulted in significant inhibition of viral propagation and conferred protection of host cells to virus killing. Overall, my study has provided a list of novel host factors that play significant roles during influenza virus infection. Further studies on these potential genes and their encoded protein products may uncover possible new targets for drug development for future therapeutic treatment. In addition to providing greater understanding of influenza virus infection, these studies will also highlight important fundamentals of cellular processes that may be broadly applicable to other fields of research.

Multivariable linear and negative binomial models were produced to assess relationships among socioeconomic and influenza rate data with the use of macrolide and fluoroquinolone antimicrobials by Canadians. Varying results were found both among and between the macrolide and fluoroquinolone groups; however, a pattern of accessibility to care was apparent. Cheaper antimicrobials were used most often in the most disadvantaged populations, and more expensive antimicrobials were used most frequently in advantaged populations. Significant interactions were found between influenza and socioeconomic variables relating to unemployment, education, and degree of poverty in a population. Results suggest that antimicrobials are being prescribed and consumed at inappropriate rates in both disadvantaged and affluent populations in Canada. In order to reduce antimicrobial use and the further development of antimicrobial resistance in Canada, we suggest that responsible antimicrobial stewardship be practiced and promoted by all physicians in community and hospital settings, particularly during the influenza season. / Public Health Agency of Canada

Behaviour is often neglected when modelling vaccination policies. This thesis shows the importance of incorporating behaviour in vaccination models of the impact of vaccines on disease dynamics. This thesis consists of three projects pertaining to voluntary vaccination in a network setting. The first project focuses on the effectiveness of voluntary ring vaccination under the presence of imitation. The contacts of a single index case vaccinate when symptoms first appear. We assume the contacts are unable to transmit infection to one another; however, we assume they are able to share their vaccination strategies. Under the presence of strong imitation, the effectiveness of voluntary ring vaccination becomes unpredictable. The second project focuses on the impact of personal experiences on voluntary influenza vaccination in a uniform network. Vaccination behaviour is based upon past infection and vaccination experiences, which creates a feedback loop between incidence and behaviour. Long-term memory acts as a stabilizing factor; however, long-term memory also decreases perceived vaccine efficacy. Vaccines conferring slowly waning immunity decrease vaccination coverage, leading to sporadic outbreaks in the absence of non-influenzal influenza-like-illness (niILI). Our results show evidence of vaccination strategy correlations being formed in the absence of imitation through past experiences. Allowing niILI to be mistaken for true influenza breaks up the strategy correlations, while stabilizing dynamics. The final model focuses on vaccination strategies targeting superspreaders, with the option of distributing economic incentives. We take a more psychological approach to influenza vaccination behaviour, where transmission of influenza occurs on an empirically based network. On average, superspreaders view the vaccine to be less effective; however, superspreaders still find vaccination more appealing because they are at a greater risk of becoming infected. The incorporation of behaviour leads to superspreader strategies to become less effective due to policy resistance; neglecting behaviour can lead to an overestimation of reduction of incidence. Public health officials should be concerned about the policy resistance and decreased perceived vaccine efficacy among superspreaders. The effectiveness of the vaccination or control policies could be diminished by the presence of behaviour, even when pro-active preventative measures are implemented by public health. / Ontario Graduate Fellowship, Ontario Graduate Scholarship in Science and Technology

<p>Avian Influenza (AI) is a contagious viral zoonotic disease with great public health implications and negative socioeconomic impact (WHO, 2006a). The highly pathogenic avian influenza (HPAI) infection is transmitted from birds to man mostly through contact with contaminated poultry and objects (INFOSAN, 2005), hence people who come in contact with birds such as live bird sellers (LBS) are the more vulnerable population (WHO, 2006a). Inadequate knowledge of AI health risks and poor practice of AI preventive measures amongst LBS increases the risk of spread of the infection in both humans and animals.The aim of this study was to describe and quantify the knowledge and practice of LBS with regards to avian influenza health risks and preventive activities in Agege, an urban area in Lagos State, Nigeria.</p>

Influenza virus is a globally significant infectious agent with the potential to cause catastrophic pandemic outbreaks. Present treatment of influenza infections is restricted to only four anti-viral drugs, but there are increasing global reports of anti-viral resistance in several seasonal strains and also the 2009 pandemic swine-origin influenza virus H1N1. Possible future pandemic outbreaks, emerging new strains and drug resistance underscore the need to understand this complex virus and its pathogenicity with the goal that novel targets can be uncovered for future therapeutic development. Extensive lung tissue damage during influenza virus infection is proposed to contribute to the development of aberrant host immune responses. Strong evidence now demonstrates the significance of the cellular death pathway in promoting efficient influenza virus replication and disease progression. Viruses rely heavily on the machinery of their host for productive replication, which is also an Achilles’ heel that could be targeted for treatment. In pursuit of unraveling the complex nature of influenza virus replication, I carried out a global shRNA screen to identify specific host factors and signaling pathways that are involved in influenza-induced cell death and replication. In this study I identified 138 genes required for influenza viruses to induce infected host cell death. These genes were found to be involved in Protein Kinase A, NF-kB and PI3K signaling cascades. These signaling pathways are well known regulators of cell death and survival, which suggests influenza viruses may carefully regulate these pathways to reach a balance that suit their requirements for efficient proliferation, eventually at the cost of the host cell. I chose five candidate genes—BAD, MxB, TNFSF12-13,TNFSF13, and USP47—that were associated with apoptosis and the major signaling pathways determined in my network analysis to further verify the genome-wide screen as well as elucidate the role of these potentially novel host factors in influenza virus replication. I show in my study that influenza virus-induced cytopathology and cell death are considerably inhibited in BAD knockdown cells and both virus replication and viral protein production also are dramatically reduced. I also report here that MxB depletion protected cells from virus-mediated cytopathology and resulted in significant inhibition of influenza virus replication for H1N1 and H3N2 subtypes. Additionally, I report that TNFSF12-13, TFNSF13, and USP47, similarly, are required for efficient influenza virus replication and induction of cell death. Depletion of these proteins resulted in significant inhibition of viral propagation and conferred protection of host cells to virus killing. Overall, my study has provided a list of novel host factors that play significant roles during influenza virus infection. Further studies on these potential genes and their encoded protein products may uncover possible new targets for drug development for future therapeutic treatment. In addition to providing greater understanding of influenza virus infection, these studies will also highlight important fundamentals of cellular processes that may be broadly applicable to other fields of research.