| Summary: | Summary: Approximately 50% of the mass of the Envelope (Env) glycoprotein surface subunit (gp120) of human immunodeficiency virus type 1 (HIV-1) is composed of N-linked carbohydrate. Until now, the dogma has been that HIV-1 lacks O-linked carbohydrate on Env. Here we show that a subset of patient-derived HIV-1 isolates contain O-linked carbohydrate on the variable 1 (V1) domain of Env gp120. We demonstrate the presence of this O-glycosylation both on virions and on gp120 expressed as a secreted protein. Further, we establish that these O-linked glycans can confer a more than 1,000-fold decrease in neutralization sensitivity (IC50) to V3-glycan broadly neutralizing antibodies. These findings uncover a structural modification to the HIV-1 Env and suggest a functional role in promoting viral escape from one category of broadly neutralizing antibodies. : Silver et al. demonstrate that certain HIV-1 isolates possess O-linked carbohydrate on their Envelope glycoprotein. These sugars allow the virus to evade V3-glycan broadly neutralizing antibodies. This work identifies a post-translational modification to the HIV-1 Envelope and sheds light on its role in shielding against the host antibody response. Keywords: HIV-1, Envelope, gp120, V1 domain, O-glycosylation, broadly neutralizing antibodies, immune evasion, escape mechanism
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