Long-Acting BMS-378806 Analogues Stabilize the State-1 Conformation of the Human Immunodeficiency Virus Type 1 Envelope Glycoproteins

Abstract

During human immunodeficiency virus type 1 (HIV-1) entry into cells, the viral envelope glycoprotein (Env) trimer [(gp120/gp41)3] binds the receptors CD4 and CCR5 and fuses the viral and cell membranes. CD4 binding changes Env from a pretriggered (state-1) conformation to more open downstream conformations. BMS-378806 (here called BMS-806) blocks CD4-induced conformational changes in Env important for entry and is hypothesized to stabilize a state-1-like Env conformation, a key vaccine target. Here, we evaluated the effects of BMS-806 on the conformation of Env on the surface of cells and virus-like particles. BMS-806 strengthened the labile, noncovalent interaction of gp120 with the Env trimer, enhanced or maintained the binding of most broadly neutralizing antibodies, and decreased the binding of poorly neutralizing antibodies. Thus, in the presence of BMS-806, the cleaved Env on the surface of cells and virus-like particles exhibits an antigenic profile consistent with a state-1 conformation. We designed novel BMS-806 analogues that stabilized the Env conformation for several weeks after a single application. These long-acting BMS-806 analogues may facilitate enrichment of the metastable state-1 Env conformation for structural characterization and presentation to the immune system. IMPORTANCE The envelope glycoprotein (Env) spike on the surface of human immunodeficiency virus type 1 (HIV-1) mediates the entry of the virus into host cells and is also the target for antibodies. During virus entry, Env needs to change shape. Env flexibility also contributes to the ability of HIV-1 to evade the host immune response; many shapes of Env raise antibodies that cannot recognize the functional Env and therefore do not block virus infection. We found that an HIV-1 entry inhibitor, BMS-806, stabilizes the functional shape of Env. We developed new variants of BMS-806 that stabilize Env in its natural state for long periods of time. The availability of such long-acting stabilizers of Env shape will allow the natural Env conformation to be characterized and tested for efficacy as a vaccine.

Mechanistic Analysis of the Broad Antiretroviral Resistance Conferred by HIV-1 Envelope Glycoprotein Mutations

“…In contrast to the other classes of ARVs, the Env mutants we identified in NL4-3 and K3016 are sensitive to two types of Ent-Is: a fusion inhibitor (T-20) and a compound that blocks CD4-induced conformational changes in Env (BMS-378806) (19,(65)(66)(67). Previous studies have shown that Ent-Is targeting CD4 or a coreceptor are effective in blocking cell-cell transmission (34,60,93).…”

“…These findings raise the possibility that Env mutations selected in the presence of ARVs might alter the viral sensitivity to Env-targeted inhibitors. To examine this question, we measured replication kinetics in the presence of the fusion inhibitor T-20 and BMS-378806, which blocks CD4-induced conformational changes in Env (19,(65)(66)(67). Interestingly, these Ent-Is efficiently suppressed replication of both WT NL4-3 and Env-A539V with no statistically significant differences in antiviral IC 50 s in a multicycle spreading infection ( Fig.…”

Asymmetric structures and conformational plasticity of the uncleaved full-length human immunodeficiency virus (HIV-1) envelope glycoprotein trimer

“…Antibody or ligand binding and smFRET analyses indicate that the Env precursor can sample multiple conformations that resemble States 1, 2 and 3 of the mature viral Env spike (73)(74)(75)(76)(77)(78)(79)(80)(81). The conformational plasticity of the Env precursor contrasts with the behavior of the mature Env, which in the absence of ligands largely resides in State 1 (42,81).…”

“…The copyright holder for this preprint this version posted March 29, 2021. ; https://doi.org/10.1101/2021.03.28.437443 doi: bioRxiv preprint BMS-806 can enrich State 1 in the uncleaved membrane-anchored Env (79,81) and BS3 crosslinking could hypothetically help to stabilize this conformation.…”

“…Uncleaved Envs that assume State-2/3 conformations are abundant on the surface of HIV-1-infected cells, in some cases reaching the cell surface by bypassing the Golgi (72). Poorly neutralizing antibodies (pNAbs) with State-2/3 specificity typically recognize these uncleaved Envs more efficiently than cleaved Env (73)(74)(75)(76)(77)(78)(79). Crosslinking the uncleaved cell-surface Env exerted effects on Env antigenicity similar to those resulting from gp120-gp41 cleavage, suggesting that the uncleaved Env might be more flexible than mature Env (80).…”