Broadly neutralizing anti-HIV antibodies do not Inhibit HIV-1-mediated cell-cell fusion


Nejat Düzgüneş: 0000-0001-6159-1391


Biomedical Sciences

Document Type


Conference Title

Biophysical Society 62nd Annual Meeting


San Francisco, CA

Conference Dates

February 17-21, 2018

Date of Presentation


Journal Title

Biophysical Journal

Journal ISSN


First Page



Objective: An effective HIV vaccine must be able to block infection by a wide range of viral isolates. PG9, PG16, PGT121, and PGT145 antibodies were identified from culture media of activated memory B-cells of an infected donor and shown to neutralize many HIV strains (Walker et al. Science 326, 285; 2009), recognizing conserved epitopes on the viral envelope protein gp120. The PG9, PG16, and PGT145 antibodies recognize V1/V2 conformational epitopes, whereas PGT121 recognizes a V3 epitope involving carbohydrates. Since HIV-1 infection occurs via both free virions and cell-cell fusion, we examined the effect of the antibodies on HIV Env-mediated cell-cell fusion. Methods: We used the HIV fusion assay developed previously in our laboratory (Yee et al. Open Virol J 5, 12; 2011). Clone69TRevEnv cells (NIH AIDS Reagent Program) that express Env in the absence of tetracycline (“HIV-Env cells”) were plated, and then labeled with Calcein-AM Green (Invitrogen). Highly CD4+SupT1 cells were labeled with CellTrace™ Calcein Red-Orange (Invitrogen), and then incubated with the adherent HIV-Env cells, with or without antibodies. Antibodies were obtained from the International AIDS Vaccine Initiative and Polymune Scientific. Lectins were purchased from EY Labs. Syncytia were observed under a Nikon Diaphot inverted fluorescence microscope. Results: Monoclonal antibodies PG9, PG16, 2G12, PGT121, and PGT145 (at up to 20 µg/ml) had little or no inhibitory effect on fusion between HIV-Env and SupT1 cells. By contrast, Hippeastrum hybrid agglutinin at 1 µg/ml completely inhibited fusion.Conclusion: Antibodies PG9, PG16, PGT121, and PGT145 are ineffective against cell-cell fusion, indicating that transmission of the virus or viral genetic material would not be inhibited. Mannan-binding lectins, however, are highly inhibitory to HIV-induced cell-cell fusion, even at low concentrations.