Generation and structural analysis of soluble oligomeric gp140 envelope proteins derived from neutralization-resistant and neutralization-susceptibleprimary HIV type 1 isolates
L. Stamatatos et al., Generation and structural analysis of soluble oligomeric gp140 envelope proteins derived from neutralization-resistant and neutralization-susceptibleprimary HIV type 1 isolates, AIDS RES H, 16(10), 2000, pp. 981-994
We generated DNA constructs expressing soluble truncated forms of the envel
ope of SF162, a neutralization-resistant primary human immunodeficiency vir
us type 1 isolate, and SF162 Delta V2, a neutralization-susceptible virus d
erived from SF162 after the deletion of 30 amino acids from the V2 loop. Th
e constructs express the entire gp120 subunit and the extracellular region
of the gp41 subunit, with either the presence ("cleaved" forms, designated
gp140C) or the absence ("fused" forms, designated gp140F) of the gp120-gp41
cleavage site. Both gp140 forms derived from SF162 and SF162 Delta V2 are
secreted in the cell medium and are recognized by the oligomer-specific ant
i-gp41 MAb T4. As is the case for the corresponding virion-associated envel
ope molecules, the CD4-binding region is occluded within both gp140F and gp
140C forms. However, structural differences exist between these two forms.
The gp140F proteins are less efficiently recognized than the gp140C protein
s by antibodies present in the sera of HIV-infected patients with neutraliz
ing activities against SF162 and SF162 Delta V2. Also, the V3 loop is more
exposed on gp140F than gp140C. As is the case for intact virions, on CD4 bi
nding both the gp140F and gp140C proteins undergo conformational changes th
at result in the exposure of the epitope recognized by MAb 17b, which has b
een implicated in coreceptor binding. In contrast, during these structural
changes the exposure of specific V3 loop epitopes is not increased on eithe
r gp140C or gp140F. Taken together, our data indicate that although these g
p140 forms differ structurally from the native envelope, their similarities
, in particular that of gp140C, outweigh their differences.