An anti-Gn glycoprotein antibody from a convalescent patient potently inhibits the infection of severe fever with thrombocytopenia syndrome virus

Abstract

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease localized to China, Japan, and Korea that is characterized by severe hemorrhage and a high fatality rate. Currently, no specific vaccine or treatment has been approved for this disease. To develop a therapeutic agent for SFTS, we isolated antibodies from a phage-displayed antibody library that was constructed from a patient who recovered from SFTS virus (SFTSV) infection. One antibody, designated as Ab10, was reactive to the Gn envelope glycoprotein of SFTSV and protected host cells and A129 mice from infection in both in vitro and in vivo experiments. Notably, Ab10 protected 80% of mice, even when injected 5 days after inoculation with a lethal dose of SFTSV. Using cross-linker assisted mass spectrometry and alanine scanning, we located the non-linear epitope of Ab10 on the Gn glycoprotein domain II and an unstructured stem region, suggesting that Ab10 may inhibit a conformational alteration that is critical for cell membrane fusion between the virus and host cell. Ab10 reacted to recombinant Gn glycoprotein in Gangwon/Korea/2012, HB28, and SD4 strains. Additionally, based on its epitope, we predict that Ab10 binds the Gn glycoprotein in 247 of 272 SFTSV isolates previously reported. Together, these data suggest that Ab10 has potential to be developed into a therapeutic agent that could protect against more than 90% of reported SFTSV isolates.

Vascular Leak and Hypercytokinemia Associated with Severe Fever with Thrombocytopenia Syndrome Virus Infection in Mice

“…In the present study, we describe the natural history of disease and pathogenesis of SFTSV infection in IFNAR -/mice with a focus on profiling the inflammatory cytokine response and resolving the onset of vascular leak to facilitate comparisons between recent reports correlating cytokine levels in human cases of SFTS with disease severity [17][18][19][20][21]. Similar to several recent reports with other strains of SFTSV [22,23], we found that IFNAR -/mice are highly sensitive to the virus with a single PFU challenge dose achieving uniform lethality. Consequently, we selected a 3 PFU SC challenge dose in our natural history study to resemble a low-dose human exposure.…”

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

“…Two anti-Gn SFTS neutralizing antibodies, Mab4-5 and Ab10, isolated from a phage display library of SFTS patient antibodies, were reported earlier (25,26). Only Ab10 was evaluated for the inhibition of SFTSV infection in an A129 mouse model without monitoring SFTSV titer in vivo during the treatment (26). In the current study, we reported the isolation of Gn-specific single-domain antibodies from an immunized camel and the comprehensive characterization of the neutralizing activity of the nanobody.…”

“…Therefore, there is an urgent need for therapeutics or vaccines for SFTSV infection in humans and animals. Two anti-Gn SFTS neutralizing antibodies, Mab4-5 and Ab10, isolated from a phage display library of SFTS patient antibodies, were reported earlier (25,26). Only Ab10 was evaluated for the inhibition of SFTSV infection in an A129 mouse model without monitoring SFTSV titer in vivo during the treatment (26).…”

Vaccination with single plasmid DNA encoding IL-12 and antigens of severe fever with thrombocytopenia syndrome virus elicits complete protection in IFNAR knockout mice

“…Following induction with 0.1 mM isopropyl β-D-thiogalactoside (IPTG) for 18 h at 16˚C, the protein was purified using HisTrap HP histidine-tagged protein columns (GE healthcare, Chicago, IL, USA) according to the manufacturer's instruction. Recombinant Gn and Gc glycoproteins fused to Fc region of human immunoglobulin heavy chain were purified as previously described [19]. Briefly, vectors cloned with gene encoding Gn or Gc were transfected into HEK293F cells (Thermo Fisher Scientific, Waltham, MA, USA) using polyethylenimine.…”