Modulation of host NK-cell activity by virus (kw:KW-1131)

Nks cells originate from the bone marrow and represent about 5 to 10 % of the lymphocytes in the blood. They belong to the first line of defenses against viruses and thus reprensent an important part of the innate immune system. Upon activation, NK cells lyse the infected cells or release cytokines such as interferon gamma, which activates macrophages and T-cells. Theses functions help to control infection during initial hours allowing the adaptive immune response to develop. Many viruses have evolved strategies to inhibit NK cells activity to allow efficient infection. For example, a lot of herpesvirus proteins function to evade NK cell activation. In addtion to the attenuation of the adaptive response, these proteins allow persistent infection within the host.

Table. Viruses modulating the activity of NK cells.

Virus	Family	Viral protein	Ation	References
HCMV	herpesviridae, Cytomegalovirus	US2, US11	Causes degradation of MHC class I by proteasomes
HCMV	herpesviridae, Cytomegalovirus	US3, US10	Retention of MHC class I in ER
HCMV	herpesviridae, Cytomegalovirus	US6	Prevents loading of peptide into MHC I molecules
HCMV	herpesviridae, Cytomegalovirus	gpUL40	Downregulates MHC I molecules from cell surface
HIV	Retroviridae, Lentivirus	Nef	Accelerates HLA-A and B endocytosis
MCMV	herpesviridae, Cytomegalovirus	m04	Binds MHC I on cell surface
MCMV	herpesviridae, Cytomegalovirus	m06	Targets MHC class I for degradation
MCMV	herpesviridae, Cytomegalovirus	m152	Downregulates MHC I form cell surface
MOCV	Poxviridae, Molluscipoxvirus	MC53L ,MC54L	Binds IL-18, blocks INF-gamma production
HCV	Flaviviridae, Hepacivirus	E2	Binds CD81 receptor on NK cells inhibition killing and cytokine production
KSHV	Herpesviridae, Rhadinovirus	K3, K5	Induces MHC class I endocytosis
HHV-1	Herpesviridae, Simplexvirus	ICP47	Prevents loading of peptides into MHC I