Maguire, Paula (2019) The role and mechanism of immunomodulation by influenza virus and its components in the predisposition to bacterial disease during influenza infection. PhD thesis, Dublin City University.
Abstract
Influenza A virus (IAV) infection predisposes individuals to severe infections with bacteria
such as Streptococcus pneumoniae (S.p.). Research shows that influenza infection
impairs the T helper 17 (Th17) immune response, which is critical in the clearance of
S.p. infections. Studies have demonstrated a role for type I Interferons in the impaired
Th17 immunity associated with IAV. The results presented in this thesis demonstrate
that IAV infection significantly impairs S.p. driven innate and adaptive cytokines.
However, this inhibition occurred in the absence of type I Interferons, suggesting an
additional mechanism of Th17 immunomodulation associated with IAV. To establish how
IAV inhibits these responses, we investigated the effect of IAV infection on specific innate
immune Toll Like Receptors (TLRs), which are triggered by S.p. infection. We have
identified that IAV targets TLRs (TLR2, TLR4, TLR9) in human monocytes, resulting in
a reduction in TLR-induced cytokines. The effect of IAV is more profound on the TLR2
and TLR9 pathways. We established IAV may be inhibiting the TLR9 pathway by
targeting RORC, a Th17-specific transcription factor. We investigated if TLR5 agonism
could restore IAV-inhibited immune responses. Levels of pneumococcus driven
cytokines, which had previously been inhibited by IAV were not reduced in the presence
of the TLR5 agonist, suggesting this may restore immune responses despite IAV
inhibition. Finally, we sought to investigate the role of the influenza surface glycoprotein,
haemagglutinin (HA) in innate and adaptive responses to S.p. and innate responses to
TLR agonism. Pneumococcus driven innate and adaptive cytokines were significantly
inhibited by HA, whilst certain TLR agonist driven cytokines were also inhibited by HA.
Novel findings include determining that immune inhibition by IAV is not solely due to type
I IFNs, and demonstrating that TLR5 agonism may be beneficial in circumventing
immune inhibition by IAV and restoring Th17 responses.
Metadata
Item Type: | Thesis (PhD) |
---|---|
Date of Award: | 19 November 2019 |
Refereed: | No |
Supervisor(s): | Johnson, Patricia and Loughran, Sinéad T. |
Subjects: | Biological Sciences > Immunology |
DCU Faculties and Centres: | DCU Faculties and Schools > Faculty of Science and Health > School of Nursing and Human Sciences |
Use License: | This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License |
ID Code: | 23951 |
Deposited On: | 08 Apr 2020 18:56 by Patricia Johnson . Last Modified 08 Apr 2020 18:56 |
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