Summary of the properties of the SIV Nef mutants lacking anti-tetherin activity.

aThe percentage of BST-2 antagonism was calculated as the amount of SIV p27 released into the culture supernatant of 293T cells transfected with constructs expressing each of the Nef mutants in the presence of rhesus tetherin relative to the amounts of SIV p27 released in the absence of tetherin.
bBinding to BST-2 was calculated as the relative band intensity of Nef to the band intensity of tetherin in immunoprecipitated samples.
cSteady-state levels of Nef protein in cell lysates were estimated by calculating the relative band intensity of each of the Nef mutant proteins compared to wild-type Nef.
dCD4 levels were calculated as the percentage of CD4 staining (MFI) on cells transfected with each of the indicated Nef-expression constructs relative to CD4 staining (MFI) on cells transfected with an empty vector.
eMHC class I levels were calculated as the percentage of MHC I staining (MFI) on cells transfected with each of the indicated Nef-expression constructs relative to MHC I staining (MFI) on cells transfected an with empty vector.
fGHOST X4/R5 cells were infected with SIV Δnef trans-complemented with the indicated wild-type or mutant Nef proteins, and the relative infectivity was calculated as the frequency of infected cells obtained for each of the mutants relative to wild-type Nef at 48-hours post-inoculation.
Nef mutants that retain wild-type levels of CD4-downregulation, MHC class I-downregulation or infectivity enhancement are indicated in bold and italics. For CD4− and MHC class I-downregulation, one asterisk indicates activity within 5 standard deviations of wild-type Nef and two asterisks indicate activity within 3 standard deviations of wild-type Nef. For infectivity enhancement, two asterisks indicate infectivity 5 standard deviations or more over SIV Δnef trans-complemented with empty vector.