HCMV is the largest human virus characterised to date, encoding approximately 165 open reading frames (ORFs). Due to many years of serial passage, laboratory adapted strains of HCMV, such as strain AD 169, have lost a 13-15kb region of genome, designated UUb', compared with HCMV clinical strains (Cha et al, 1996). Loss of this 13-15kb UUb' region is correlated with decreased virulence and increased sensitivity to Natural Killer (NK) cell lysis, leading to the hypothesis that the UUb' region is harbouring one or more NK evasion functions. A comprehensive screen of the UUb * region of HCMV strain Merlin to identify novel NK evasion functions has formed the focus of this study. The UUb1 region encompasses 23 ORFs from UL128 through to UL150. In addition, UL14, a homologue of the UUb' resident ORF UL141, and UL141A, a newly identified UUb' ORF, were included in this study as potential NK evasion functions. Using the AdEasy system and the newly developed AdZ system, the generation of recombinant adenoviruses (RAds) encoding for each of the 24 UUb' ORFs, plus the UL141 homologue, UL14, has been successful and provides a complete resource for the study of these proteins. The majority of the UUb' proteins were previously uncharacterised, and the incorporation of a C-terminal Streptag II has enabled preliminary characterisation of these ORFs. Producing the bank of UUb' RAds has also enabled a functional screen of this region in order to identify novel NK evasion functions. As a result of the systematic functional NK screen of the UUb' region, two novel NK evasion functions have been identified the UL141 homologue, UL14 and the UUb' resident ORF, UL135. Their identification brings the total number of NK evasion functions encoded by HCMV up to eight: UL40, UL16, UL18, UL83 (pp65), UL141, UL142, UL14 and UL135. These provide HCMV with an impressive arsenal dedicated to evasion of NK lysis, and are further evidence for the importance of NK cells in the control of HCMV. Further analysis of the NK evasion function encoded by UL14 revealed that similar to UL141, UL14 encodes an EndoH sensitive glycoprotein and was observed to co-localise with the ER resident protein, calnexin, consistent with gpUL14 being ER- retained. The biochemical similarities of the UL141 and UL14 NK evasion ORFs may be of functional significance, indicating that gpUL14 may also be sequestering an NK activating ligand within the cell similar to gpUL141 (Tomasec et al, 2005).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:584183 |
| Date | January 2007 |
| Creators | Armstrong, Melanie |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/55696/ |
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