Heterogeneity in glycan composition on the surface of HIV-1 envelope determines virus sensitivity to lectins

Lectins that target N-glycans on the surface of HIV-1 envelope (Env) glycoprotein have the potential for use as antiviral agents. Although progress has been made in deciphering the molecular details of lectin and Env glycan interaction, further studies are needed to better understand Env glycan heterogeneity among HIV-1 isolates and its influence on virus-neutralization sensitivity to lectins. This study evaluated a panel of lectins with fine specificity for distinct oligosaccharides and assessed their ability to inhibit infection of HIV-1 viruses known to have differing sensitivity to anti-HIV Env antibodies. The results showed that HIV-1 isolates have different sensitivity to lectins specific for alpha 1-3Man, alpha 1-6Man, and alpha 1-2Man binding lectins. Considering that lectins exclusively recognize the oligosaccharide components of virus Env, these data suggest that glycan heterogeneity among HIV-1 isolates may explain this differential sensitivity. To evaluate this further, chronic and acute viruses were produced in the presence of different glycosidase inhibitors to express more homogenous glycans. Viruses enriched for alpha 1-2Man terminating Man(5-9)GlcNAc(2) glycans became similarly sensitive to alpha 1-2Man-binding lectins. The alpha 1-3Man- and alpha 1-6Man-binding lectins also were more potent against viruses expressing predominantly Man(5)GlcNAc(2) and hybrid type glycans with terminal alpha 1-3Man and alpha 1-6Man. Furthermore, lectin-mediated inhibition was competitively alleviated by mannan and this effect was augmented by enrichment of man nose -type glycans on the virus. In addition, while Env of viruses enriched with mannosetype glycans were sensitive to Endo-H deglycosylation, Env of untreated viruses were partially resistant, indicating that HIV-1 Env glycans are heterogeneously comprised of complex, hybrid, and mannose types. Overall, our data demonstrate that HIV-1 isolates display differential sensitivity to lectins, in part due to the microheterogeneity of N-linked glycans expressed on the surface of the virus Env glycoprotein.