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Title: The role of airway epithelial cell and natural killer cell interactions during RSV infection
Author: Davies, Jennifer Claire
ISNI:       0000 0004 7656 964X
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Little is known about the early interactions that occur between respiratory syncytial virus (RSV) infected airway epithelium and NK cells. This includes airway epithelial cell (AEC) surface expression of IL-15/IL-15Ra complex, which could be a potent inducer of NK cell activation via trans-presentation. The work here describes the hypothesis that AECs after infection can activate NK cells which in turn influence immune and inflammatory responses including AEC activity. Human bronchial epithelium cell line, BEAS-2B, and human nasal airway epithelial cells (HNAECs) were used in vitro to characterise the expression of IL-12, IL-15, IL-18 and IL-15Ra during RSV infection. IL-12 protein was not expressed. RSV infection significantly increased expression of cell surface IL-15Ra on BEAS-2B cells and HNAECs. BEAS-2B cells also expressed cell surface IL-15 indicating complex expression. IL-15 protein was only detected in infected BEAS-2B cell culture supernatants and not HNAECs. Soluble IL-18 protein was only expressed by HNAECs and significantly increased with infection. The RSV infected airway epithelium has the potential to activate NK cells with IL-15 signalling predominantly occurring through the IL-15/IL-15Ra complex. A co-culture model was then established to examine AEC-NK cell interaction. Co-culture of peripheral blood NK cells with RSV infected BEAS-2B cells or HNAECs increased expression of IFN-? from NK cells. IFN-? expression was dependent on direct cell-to-cell contact with infected BEAS-2B cells. To further characterise AEC-NK cell interactions and how this may influence the wider inflammatory response to RSV, expression of AEC-derived CXCL9, CXCL10, CXCL11, TARC and BAFF during co-culture was characterised. CXCL10 was significantly increased from infected AEC-NK cell co-cultures compared to those without NK cells. BAFF mRNA was significantly increased in BEAS-2B cell-NK cell co-cultures however, soluble protein remained the same. Treatment of non-infected BEAS-2B cells with IFN-? significantly increased cell surface expression of IL-15 and IL-15Ra and this response was not observed after infection. NK cells co-cultured with Th2 cytokine pre-treated and infected BEAS-2B cells had significantly increased IFN-? expression compared to those from cocultures with no cytokine or IFN-? treatment pre-treatment. Nasopharyngeal aspirates from RSV and rhinovirus (RV) infected infants were analysed for IL-15, IL-15/IL-15Ra complex and IL-18 to add in vivo relevance to the in vitro findings. IL-15 and IL-18 protein levels were significantly higher in NPAs from RSV infected infants who required oxygen treatment compared to those who did not. IL-15 and IL-18 were significantly higher in NPAs from those with RV infection compared to RSV. Collectively, the in vivo relevance of these findings suggest that RSV infected AECs can alone activate NK cells. This is dependent on direct cell-to-cell contact of which the IL-15/IL-15Ra complex may be an essential method of NK cell activation. Activated NK cells may then aid in an increase in AEC-derived CXCL10 protein expression and possibly membrane-bound BAFF during contact with infected airway epithelium. NK cells may therefore contribute to adaptive immune responses through enhancing airway epithelial responses.
Supervisor: Flanagan, Brian ; McNamara, Paul Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral