IgG3 shows greater HIV-1 virion internalization than IgG1, independent of Env protein binding.

<p><b>A-D.</b> Wild type CH31 IgG3 and IgG1 were tested for internalization of ConSgp140-conjugated 1 μm fluorescent beads (N = 8 independent experiments representing 6 different donors) (A), HIV-1_BaL-Tomato virions (N = 19 independent experiments representing 11 different donors) (B) and HIV-1_92TH023-Tomato virions (N = 12 independent experiments representing 6 different donors) (C) in human primary monocytes. Anti-influenza mAb CH65 in each subclass backbone were also tested as negative controls. Box-and-whisker plots indicate 25^th and 75^th percentiles by box, and minimum and maximum scores by whisker. Horizontal black dashed line indicates limit of detection, as calculated using the mean + 3 SD of negative controls in the corresponding assays. The differences in phagocytosis score were compared between IgG1 and IgG3 using a Sign test (D). <b>E-H.</b> To examine if differences in phagocytosis were due to different binding to HIV-1 Env, antibody binding to HIV-1 Env protein was tested using biolayer interferometry. Antibodies (CH31 and CH65 IgG1 and IgG3) were loaded on a Human IgG Capture sensor, and binding to HIV-1_92Th023 gDneg gp120 monomer protein in solution was tested (E). Specific binding curves of gp120 binding to CH31 IgG1 and IgG3 (light blue and dark blue lines respectively) are shown along with 1:1 Langmuir model fitted curves (red lines) (F). Dissociation constant (K_D), association rate (k_on), and dissociation rate (k_off) are shown for 3 independent experiments (G), and their respective median values are also shown (H).