Innate Immune Evasion Strategies by Human Immunodeficiency Virus Type 1
Table 1
Role of HIV-1 viral proteins in innate immune evasion.
HIV-1 accessory proteins
Function in innate immune evasion
gp41
(i) Activates classical pathway of complement system (ii) Enhances viral entry and spread through interaction with complement receptor CR3 (iii) Stimulates synthesis of C3 in neurons and astrocytes (iv) Recruits factor H responsible for protecting from complement dependent lysis (v) Induces expression of NKp44L on CD4+ T cells and results in their depletion
gp120
(i) Recruits factor H (ii) Induces production of inflammatory cytokines and the CC chemokines (iii) Suppresses pDC activation and produces IFN and other cytokines (iv) Inhibits cytolytic activity of NK cells by interfering with TLR9
Tat
(i) Substrate homologue for eIF2 and competes for PKR mediated phosphorylation (ii) Mimics -chemokines and functions as chemoattractant for monocytes and macrophages (iii) Inhibits LFA-I mediated Ca2+ influx and impairs NK cell cytotoxicity (iv) Interacts with Dicer and inhibits its activity, suppresses miRNA synthesis
Nef
(i) Increases expression of proinflammatory cytokines (ii) Downregulates HLA-A, HLA-B on target cells and inhibits NK cell cytotoxicity (iii) Helps in budding of HIV-1 (iv) Produces viral miRNA in HIV-1 persistently infected cells
Vpr
(i) Alters the levels of proinflammatory cytokines (ii) Upregulates NKG2D receptor on NK cells
Vpu
(i) Causes detachment of viral particle from cell membrane through interaction with tetherin
Vif
(i) Inhibits the packaging of APOBEC3G in virus producer cells causes proteosomal degradation of APOBEC3G
