Nasal delivery of broadly neutralizing antibodies protects mice from lethal challenge with SARS-CoV-2 delta and omicron variants

Abstract

Multiple new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have constantly emerged, as the delta and omicron variants, which have developed resistance to currently gained neutralizing antibodies. This highlights a critical need to discover new therapeutic agents to overcome the variants mutations. Despite the availability of vaccines against coronavirus disease 2019 (COVID-19), the use of broadly neutralizing antibodies has been considered as an alternative way for the prevention or treatment of SARS-CoV-2 variants infection. Here, we show that the nasal delivery of two previously characterized broadly neutralizing antibodies (F61 and H121) protected K18-hACE2 mice against lethal challenge with SARS-CoV-2 variants. The broadly protective efficacy of the F61 or F61/F121 cocktail antibodies was evaluated by lethal challenge with the wild strain (WIV04) and multiple variants, including beta (B.1.351), delta (B.1.617.2), and omicron (B.1.1.529) at 200 or 1000 TCID₅₀, and the minimum antibody administration doses (5-1.25 ​mg/kg body weight) were also evaluated with delta and omicron challenge. Fully prophylactic protections were found in all challenged groups with both F61 and F61/H121 combination at the administration dose of 20 ​mg/kg body weight, and corresponding mice lung viral RNA showed negative, with almost all alveolar septa and cavities remaining normal. Furthermore, low-dose antibody treatment induced significant prophylactic protection against lethal challenge with delta and omicron variants, whereas the F61/H121 combination showed excellent results against omicron infection. Our findings indicated the potential use of broadly neutralizing monoclonal antibodies as prophylactic and therapeutic agent for protection of current emerged SARS-CoV-2 variants infection.

Keywords: Coronavirus disease 2019 (COVID-2019); K18-hACE2; Omicron variant; Prophylactic protection; Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Fig. 1

Evaluation of the biodistribution of F61 monoclonal antibodies in mice. A Representative whole-body images. B–D Quantification of fluorescence signals in mice after intranasal delivery of different doses and at different time points (B: 24 ​h, 10 ​mg/kg; C: 48 ​h, 5 ​mg/kg; D: 48 ​h, 1.25 ​mg/kg). E–J Representative ex vivo images. 24 ​h, 10 ​mg/kg (E, H); 48 ​h, 5 ​mg/kg (I, F); 48 ​h, 1.25 ​mg/kg (G, J). K–N Quantification of the average radiant efficiency of different organs at different time points (K: 2 ​h, L: 24 ​h, M: 48 ​h, N: 96 ​h) after nasal delivery of F61 (1.25 ​mg/kg). O–REx vivo imaging of different organs at different time points (O: 2 ​h, P: 24 ​h, Q: 48 ​h, R: 96 ​h) after nasal delivery of F61 (1.25 ​mg/kg). Br, brain; H, heart; K, kidney; Lu, lung; Lv, liver; NC, nasal cavity; S, spleen; J, jejunum; U, urocyst. Data are means ​± ​standard deviations in four mice, as determined by Student's t-test. Dashed line: average autofluorescence of organs.

Fig. 2

Body weights and survival in mice treated with F61 or F61+H121 monoclonal antibodies in a prophylactic analysis of challenge with the wild strain (WIV04) or beta variant (B.1.351). A–D Body weights and survival curves of K18-hACE2 mice treated with 20 ​mg/kg F61 or F61+H121 via intranasal route before infection with 200 TCID₅₀ (A, B) or 1000 TCID₅₀ (C, D) of the wild strain of SARS-CoV-2 (WIV04). E–H, Body weights and survival curves of K18-hACE2 mice treated with 20 ​mg/kg F61 or F61+H121 via intranasal route before infection with 200 TCID₅₀ (E, F) or 1000 TCID₅₀ (G, H) of the beta variant. As a negative control, PBS was administered via intranasal route 2 ​h before infection (A–H). Body weight curve values represent means ​± ​standard errors of the mean (n ​= ​3 mice/group). Significant differences between the antibody treatment group and negative control are shown. ns, P ​> ​0.05; ∗, P ​< ​0.05; ∗∗, P ​< ​0.0001, as determined by Student's t-test.

Fig. 3

Antibodies provided prophylactic protection against alterations in lung pathology following inoculation with the wild strain and B.1.351 variant of SARS-CoV-2. Mice were pretreated with 20 ​mg/kg F61 or F61+H121 cocktail via intranasal route 2 ​h before challenge with WIV04 or the beta variant. The same volume of PBS was administered via intranasal route in the negative control. Lungs were harvested from each group (n ​= ​3). A Viral RNA levels in the lungs were measured by qRT-PCR (copies/mL). (A-a) 200 TCID₅₀ WIV04, (A-b) 1000 TCID₅₀ WIV04, (A-c) 200 TCID₅₀ beta variant, and (A-d) 1000 TCID₅₀ beta variant. B Histopathological analyses of mice pretreated with or without monoclonal antibodies and infected with SARS-CoV-2 strains. Lungs were fixed for sectioning before staining with hematoxylin and eosin. (B-a–B-l) Lung sections from mice treated PBS, F61, and F61/H121 cocktail before challenge with 200 TCID₅₀ WIV04 (B-a–B-c), 1000 TCID₅₀ WIV04 (B-d–B-f), 200 TCID₅₀ beta variant (B-g–B-i), or 1000 TCID₅₀ beta variant (B-j–B-l). All data points are shown, along with medians. ns, P ​> ​0.05; ∗, P ​< ​0.05; ∗∗, P ​< ​0.0001, as determined by Student's t-test. Limit of detection (LOD), 500 copies/mL. Scale bars, 200 ​μm.

Fig. 4

Prophylatic effects of F61 or F61/H121 cocktail against delta SARS-CoV-2 (B.1.617.2) in K18-hACE2 mice. A–B Body weights, survival curves, and viral RNA loads in the lungs of K18-hACE2 mice treated with different doses of antibodies (1.25, 5, 10, and 20 ​mg/kg) F61 (A) or F61+H121 (B) cocktail via the intranasal route before infection with 200 TCID₅₀ delta variant. C Body weights, survival curves, and viral RNA loads in the lungs of K18-hACE2 mice treated with 20 ​mg/kg F61or F61+H121 cocktail via intranasal route before infection with 1000 TCID₅₀ delta variant. D–E Body weights, survival curves and lung virus RNA detected by qRT-PCR of K18-hACE2 mice treated with a low dose antibodies (5 ​mg/kg or 1.25 ​mg/kg; D for F61, E for F61+H121 cocktail) via intranasal route before infection with 1000 TCID₅₀ of delta variants. Viral RNA loads were determined using qRT-PCR. Body weight curve values represent means ​± ​standard errors of the means (n ​= ​3–6 mice/group). Significant differences between the antibody treatment group and negative control are shown. All data points of virus load in the lungs are shown, along with the medians. ns, P ​> ​0.05; ∗, P ​< ​0.05; ∗∗, P ​< ​0.0001, as determined by Student's t test. Limit of detection (LOD), 500 copies/mL.

Fig. 5

Prophylactic effects of F61 or F61/H121 antibodies against the omicron SARS-CoV-2 (B.1.1.529) variant in K18-hACE2 mice. Body weights, survival curves, and viral RNA loads in the lungs of K18-hACE2 mice treated with difference doses of antibodies (5, 20 ​mg/kg) F61 or F61+H121 via intranasal route before infection with 200 TCID₅₀ (A) or 1000 TCID₅₀ (B) omicron variant. As a negative control, PBS was administered (A, B). Body weight curve values represent means ​± ​standard errors of the means (n ​= ​3–4 mice/group). Significant differences between the antibody treatment group and negative control are shown. All data points for viral load in the lungs are shown, along with the medians. ns, P ​> ​0.05; ∗, P ​< ​0.05; ∗∗, P ​< ​0.0001, as determined by Student's t-test. Limit of detection (LOD), 500 copies/mL.