Table 1.

Comparison of HIV-1 and HIV-2 regarding SAMHD1 degradation and potential disease consequences.

Lentiviruses	HIV-1	SIVsm/HIV-2 #
Vpx protein expression	No	Yes
Human SAMHD1 degradation	No	Yes
Efficient infection of myeloid cells	No	Yes
Triggering myeloid-cell-mediated innate anti-viral immunity through type I interferon	No	Yes
Potential disease outcome	Spread of infection and AIDS	Confined infection, no AIDS in natural hosts

^# It is known that cross-species transmission of sooty mangabey SIV (SIVsm) to humans has given rise to HIV-2 [6].