Abstract
The HIV-1 envelope protein (Env) is heavily glycosylated, with approximately 50% of the Env molecular mass being contributed by N-glycans. HIV-1 Env N-glycans shield the protein backbone and have been shown to play key roles in determining Env structure, surface exposure, and, consequently, antigenicity, infectivity, antibody neutralization, and carbohydrate and receptor binding. Studies of HIV-1 glycosylation have focused mainly on the position of glycosylation, rather than the types of glycans. Also, the role of Env glycan moieties on HIV-1 transmission has not been systematically defined. Using viruses with modified Env glycan content and heterogeneity, we examined the effects of Env glycan moieties on the major events of HIV-1 transmission. Compared to viruses with less oligomannose and more complex Env glycans, viruses with more oligomannose and less complex glycans more efficiently (i) transcytosed across an epithelial cell monolayer, (ii) attached to monocyte-derived macrophages (MDMs), (iii) bound monocyte-derived dendritic cells (MoDCs), and (iv) trans-infected primary lymphocytes via MoDCs. However, viruses with more oligomannose and less complex glycans displayed impaired infectivity in TZMbl cells, MDMs, primary lymphocytes, and fresh human intestinal tissue. Thus, N-linked Env glycans display discordant effects on the major events of HIV-1 transmission, with mature oligosaccharide structures on Env playing a crucial role in HIV-1 infection. Env glycosylation should be taken into consideration in the development of vaccine strategies to interdict HIV-1 transmission. IMPORTANCE: HIV-1 Env N-glycans shield the protein backbone and play key roles in determining Env structure and surface exposure, thereby impacting Env antigenicity, infectivity, antibody neutralization, and carbohydrate and receptor binding. Studies of HIV-1 glycosylation have focused mainly on the position of glycosylation, rather than the types of glycans. In the study described in this report, we investigated systematically the role of Env glycan moieties on HIV-1 transmission. We show that N-linked Env glycans display discordant effects on the major events of HIV-1 transmission. These data indicate that Env glycan moieties impact HIV-1 transmission and that modulation of Env glycan moieties offers a potential strategy for the development of therapeutic or prophylactic vaccines against HIV-1.