Lack of complex N -glycans on HIV-1 envelope glycoproteins preserves protein conformation and entry function

Abstract The HIV-1 envelope glycoprotein complex (Env) is the focus of vaccine development aimed at eliciting humoral immunity. Env's extensive and heterogeneous N -linked glycosylation affects folding, binding to lectin receptors, antigenicity and immunogenicity. We characterized recombinant Env proteins and virus particles produced in mammalian cells that lack N -acetylglucosaminyltransferase I (GnTI), an enzyme necessary for the conversion of oligomannose N -glycans to complex N -glycans. Carbohydrate analyses revealed that trimeric Env produced in GnTI−/− cells contained exclusively oligomannose N -glycans, with incompletely trimmed oligomannose glycans predominating. The folding and conformation of Env proteins was little affected by the manipulation of the glycosylation. Viruses produced in GnTI−/− cells were infectious, indicating that the conversion to complex glycans is not necessary for Env entry function, although virus binding to the C-type lectin DC-SIGN was enhanced. Manipulating Env's N -glycosylation may be useful for structural and functional studies and for vaccine design.