The envelope glycoprotein (Env) spike, a heterodimeric trimer consisting of three gp120 exterior subunits and three gp41 transmembrane subunits, is the only HIV-1-specific target for neutralizing antibodies (NAbs). The appropriate presentation of Env to the immune system may be an essential part of a successful vaccine strategy. Unfortunately, the Env trimer has evolved features to minimize the elicitation and impact of neutralizing antibodies, including a heavy coat of carbohydrate. Approximately 50% of the mass of gp120 consists of carbohydrate, with most of the more than 24 potential N-linked glycosylation sites (PNGSs) utilized in most HIV-1 variants
Env is highly glycosylated, and yet vaccine developers have lacked guidance on how to assess whether their immunogens have optimal glycosylation.