Fig 1.
HIV-1 bnAbs cross-react with the receptor binding domain of SARS-CoV-2.
(A–B) Cross-reactivity of anti-HIV-1 broadly neutralizing antibodies targeting diverse epitopes on HIV-1 Env and non-neutralizing antibodies were assessed by ELISA using SARS-CoV-2RBD and SARS-CoV-2 S2Pecto. CR3022, a SARS-CoV neutralizing antibody, was used as positive control. Two antibodies targeting SIV Env were used as negative control. Area under curve (AUC) of OD450 values of a 12-point binding curve (range, 0.0048 to 10 μg/ml) from three independent experiments are shown. (C) Two-tailed Spearman’s correlation was calculated using the area under curve (AUC) values. A significant positive correlation was observed between RBD and S2Pecto (spearman r = 0.8879, p <0.0001). (D) Binding of HIV-1 bnAbs that showed cross-reactivity to S2P and RBD domain of SARS-CoV-2 in ELISA to full-length SARS-CoV-2 S glycoprotein expressed on the surface of HEK293T cells. Average median fluorescence intensity values of a 12-point binding curve (range, 0.0048 to 10 μg/ml) from three independent experiments were used to draw the curve. CR3022, a SARS-CoV neutralizing antibody, and CC12.1, a SARS-CoV-2 neutralizing antibody, were used as positive control.
Fig 2.
Somatically engineered VRC07.523LS cross-reacts with SARS-CoV-2.
Cross-reactivity of anti-HIV-1 broadly neutralizing antibodies, VRC07.523LS, VRC01 and VRC03, targeting the CD4-binding site on HIV-1 Env. Cross-reactivity was assessed by ELISA using (a) SARS-CoV-2RBD and (b) SARS-CoV-2 S2Pecto. OD450, optical density at 450 nm. OD450 values are from a 12-point binding curve (range, 0.0048 to 10 μg/ml).
Fig 3.
Lentiviral (HIV-1) particles pseudotyped with SARS-CoV-2 spike productively infect 293T/ACE2 and Vero-E6 cells.
(A–D) Infectivity measurements of SARS-CoV-2 pseudoviruses on the indicated cell lines. Infectivity was quantified by measuring luciferase activity (relative light units, RLU) following infection of cells in 96-well plates with the indicated volume (inoculum, μl/well) of pseudotyped viruses. Pseudoviruses were generated by using two plasmid system (HIV-1 proviral backbone containing luciferase gene and SARS-CoV-2 spike) or three plasmid system (HIV-1 proviral backbone, Luciferase reporter plasmid and SARS-CoV-2 spike). Infectivity assays were performed twice in triplicates and average RLU are shown. (E–F) Amphoteric VSV-G and MLV pseudoviruses were used as positive virus infection controls.
Fig 4.
Neutralization of SARS-CoV-2 by HIV-1 bnAbs.
(A) The bnAbs were tested for neutralization of pseudotyped SARS-CoV-2 virions. Percent neutralization was calculated by assessing relative luminescence units (RLU) in cell lysates of HEK293T-ACE2 cells 48 hours after infection with SARS-CoV-2 pseudoviruses in the presence of increasing amounts of bnAbs (range, 0.0048 to 10 μg/ml). N6, an anti-HIV-1 CD4-binding site bnAb, showed cross-neutralization of SARS-CoV-2. Dotted line corresponds to 50% neutralization. Graphs were plotted using average values (percent neutralization) from three independent experiments. (B) Affinity of N6 against SARS-CoV-2 RBD was measured using biolayer interferometry. (C) Competition ELISA was performed for RBD binding to ACE2 in presence and absence of N6. Average OD450 value from three independent experiments are shown. CR3022, a SARS-CoV neutralizing antibody, and CC12.1, a SARS-CoV-2 neutralizing antibody, were used as positive control.
Fig 5.
N6 failed to neutralize authentic SARS-CoV-2 virus.
A) SARS-CoV-2 infected Vero-E6 cells monolayer after 72 hours post infection is shown as virus control B) Uninfected Vero-E6 cells monolayer after 72 hours showing complete absence of CPE is shown as representative cell control. Incubation of SARS-CoV-2 virus with 20 μg/ml of C) N6, D) II62 scFv-Fc and E) Anti-RBD IgG respectively, followed by adsorption for 60 minutes on Vero E6 cells. CPE was observed after 72 hours. No significant reduction in the CPE (neutralizing activity) was observed for N6 & II62 mAb which indicates these antibodies did not block SARS-CoV-2 infection. The purified Anti-RBD IgG was used as assay positive control and no CPE was observed (upto 0.1μg/ml) which means virus is completely blocked by neutralizing antibodies and did not show infection on Vero-E6 cells Scale, 500px.
Fig 6.
Polyclonal plasma of HIV-1 infected children neutralizes SARS-CoV-2.
(A) Cross-reactivity of anti-HIV-1 neutralizing plasma antibodies from ten children with chronic HIV-1 infection against SARS-CoV-2RBD and SARS-CoV-2 S2Pecto was assessed by ELISA. Plasma antibodies from three seronegative healthy donors were used as negative control. Area under the curve (AUC) of OD450 values of a 12-point binding curve (range, inverse plasma dilution of 100 to 51200), from three independent experiments are shown. (B) Plasma samples were tested for their neutralization of pseudotyped SARS-CoV-2 virions. Percent neutralization was calculated by assessing relative luminescence units (RLU) in cell lysates of HEK293T-ACE2 cells 48 hours after infection with SARS-CoV-2 pseudoviruses in the presence of increasing dilution of plasma samples (range, inverse plasma dilution of 100 to 51200). (C) Respective ID50 (50% inhibitory dilution) for plasma from all ten children are shown. (D) ID50 titres against lentiviral pseudoviruses of all seven coronaviruses from all five children that cross-neutralized SARS-CoV-2 (range, inverse plasma dilution of 100 to 51200). (E) Maximum percent neutralization of all seven pseudotyped coronaviruses at the fixed plasma dilution of 1:100.