Table 1.

Summary of anti-HIV restriction factors and their characteristics.

Restriction Factor	Mechanism	Viral evasion	Disadvantages	Exploitation
APOBEC	Cytidine deamination of viral genome	Vif mediated proteasomal degradation	APOBEC3G induced mutations may promote evolution of HIV	Modified APOBEC3G restricts HIV in T cells and macrophages [11]
SAMHD1	dNTP triphosphohydrolase activity depletes dNTPs and prevents reverse transcription	HIV-2 Vpx causes proteasomal degradation	Antiviral function limited to quiescent cells	Undefined
Tetherin	Prevents HIV release by anchoring budding virus particles	Lysosomal degradation is promoted by Vpu	Reduces, but does not abolish spread of virus.or establishment of reservoirs	Vpu resistant tetherin in cell lines [12]
TRIM5α/TRIMCyp	Targets virus for proteasomal degradation and disrupts uncoating	HIV-1 accessory proteins are unable to counteract TRIM restriction	Species specific restriction; human TRIM5α does not restrict HIV-1	Chimeric TRIM5α and humanised TRIMCyp restriction demonstrated in humanised mice [13,14]