A single-domain antibody inhibits SFTSV and mitigates virus-induced pathogenesis in vivo
Xilin Wu, Yanlei Li, Bilian Huang, Xiaohua Ma, Linjing Zhu, Nan Zheng, Shijie Xu, Waqas Nawaz, Changping Xu, Zhiwei Wu
Xilin Wu, Yanlei Li, Bilian Huang, Xiaohua Ma, Linjing Zhu, Nan Zheng, Shijie Xu, Waqas Nawaz, Changping Xu, Zhiwei Wu
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Research Article Infectious disease Therapeutics

A single-domain antibody inhibits SFTSV and mitigates virus-induced pathogenesis in vivo

Abstract

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel tick-borne bunyavirus that recently emerged in East Asian countries. SFTS is characterized by high fever, thrombocytopenia, leukopenia, multiorgan failure, and hemorrhage with case fatality rates of 6.3% to 30%. Neither antivirals nor vaccines are available at present. We previously demonstrated that neutralizing antibodies specific for SFTSV glycoprotein (Gn) played a vital role in the survival of patients with SFTS. Nanobodies from camels present unique properties, such as thermostability, high affinity, and low immunogenicity. In the current study, mammalian expressed SFTSV Gn was used to immunize a camel, and functional nanobodies were isolated from the B cell nanobody library constructed from the immunized animal. Clone SNB02 was selected for in-depth analysis for its inhibition of SFTSV replication both in vitro and in vivo. We showed that SNB02 potently inhibited SFTSV infection and prevented thrombocytopenia in a humanized mouse model and is a potential candidate for therapeutics.

Authors

Xilin Wu, Yanlei Li, Bilian Huang, Xiaohua Ma, Linjing Zhu, Nan Zheng, Shijie Xu, Waqas Nawaz, Changping Xu, Zhiwei Wu

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Figure 5

Protection of NCG-HuPBL mice against challenges of live SFTSV.

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Protection of NCG-HuPBL mice against challenges of live SFTSV. (A) Exper...
(A) Experimental schedule of SNB02 in the treatment of SFTSV infection. (B) Plasma viral loads among 3 groups of color-coded NCG-HuPBL mice including SFTSV challenge with PBS treatment as control (black, n = 8, 4 M + 4 F), SNB02 treatment 1 hour after SFTSV challenge (red, n = 8, 4 M + 4 F), and SNB02 treatment 1 day after SFTSV challenge (green, n = 8 4 M + 4 F). Each line represents data from 1 group. Data represent median + range. The limit of detection was 1000 genome copies/mL. Two-way ANOVA with Tukey’s test was performed to compare treatment group with control group. ns, no significance; ***P < 0.001. Red ***, the results of SNB02-1h compared with PBS control group; SNB02-24h compared with PBS had no significant difference. (C) Platelet cell counts were calculated among the same color-coded groups of animals. The normal range is between the 2 dashed lines. Each dot represents data from 1 mouse. Data represent mean ± SEM; 1-way ANOVA with Bonferroni’s multiple comparison was used for statistical analysis. (D) The correlation between plasma viral load and platelet counts at 12 dpi among the same color-coded groups of animals. Correlation analyses were performed by linear regression using the GraphPad Prism 5.01 program. (E) Humanized SFTSV-infected NCG mice were treated with SNB02 or sham treatment. Humanized NCG mice without SFTSV infection were taken as a mock control. These mice were then given an intravenous injection of Evan’s blue. Evan’s blue accumulation was measured in lung to assess vascular permeability (n = 2). Data represent mean ± SEM; 1-way ANOVA with Bonferroni’s multiple comparison was used for statistical analysis. ns, no significance; ***P < 0.001.