Human cytomegalovirus evasion of natural killer cell functions (360G-Wellcome-079591_Z_06_Z)

Human cytomegalovirus (HCMV) provides a paradigm for how a complex viral pathogen persists and evades immune responses. HCMV evades cytotoxic T cells by downregulating class I MHC, but then has to evade natural killer (NK) cells. We have recently described a novel MHC-like gene unique to clinical isolates that inhibits NK cell lysis in a clonally dependant manor. The specific goals of the work proposed are to: (i)Define the mechanism of action of the novel viral NK evasion gene product (UL142) by identifying its ligand and how this mediates evasion of NK cell cytotoxicity.(ii)Construct deletion mutants of HCMV, for UL142 and other NK evasion genes, using Bacterial Artificial Chromosome (BAC) methodology , and use NK cell clones to determine whether CMV encodes further proteins, which mediate NK cell evasion. We will use these BAC-HCMV mutants to determine if the known evasion genes are redundant or directed at NK clone subsets, (this might explain why HCMV encodes multiple mechanisms to evade NK cells). (iii) Investigate subjects with HCMV infection to determine whether infection with HCMV shapes the expressed NK cell receptor repertoire. (iv)Determine if HCMV proteins can functionaly interact with NK receptors on HCMV specific CD8+ cells impairing effector function.