Fig 1.
Structural analysis of the SFTSV Gn head–mAb 40C10 complex.
(A) Schematic diagram showing the experimental design. (B) The overall structure of the SFTSV Gn head–mAb 40C10 complex. The mAb 40C10 heavy chain and light chain are colored salmon and yellow, respectively. The SFTSV Gn head is colored gray and displayed in surface representation. (C) The binding region of mAb 40C10 on the SFTSV Gn head. The region binding to the heavy chain of mAb 40C10 on the SFTSV Gn head is colored salmon, and the region binding to the light chain of mAb 40C10 on the SFTSV Gn head is colored yellow. The CDR loops of mAb 40C10 are colored as above. (D) The detailed interactions between the SFTSV Gn head and the LCDRs, HCDR3 and LFR2. The residues are shown as sticks and colored limon (LCDRs), yellow (LFR2) and pink (HCDR3). The glycosylation site on the SFTSV Gn head and the sugar molecules are presented in stick form and are colored gray and cyan, respectively. The yellow dashed lines represent hydrogen bonds, and the blue dashed lines represent salt bridges.
Fig 2.
Analysis of the binding epitope of mAb 40C10 on the SFTSV Gn head.
(A) The binding epitopes of mAb 40C10, MAb 4–5, and Ab10 on the SFTSV Gn head are depicted. The three domains of the SFTSV Gn head are colored pale green, light blue and aquamarine. MAb 40C10 is colored gold, MAb 4–5 is colored red, and the binding sites of Ab10 on the SFTSV Gn head are colored purple. (B and C) MAb 40C10 bound to the surface of the SFTSV virion (5-fold local reconstruction of SFTSV virion, EMD-35178), with penton and hexon highlighted in color. The Gn and Gc of penton are colored in cornflower blue and medium purple, respectively, and the Gn and Gc of hexon are colored medium spring green and light pink, respectively. (D and E) MAb 40C10 and MAb 4–5 bind to either the hexon or penton Gn protein. Penton, hexon, mAb 40C10 and MAb 4–5 are colored as above (PDB: 8I4T, 7X6W, and 7X72).
Fig 3.
Evaluation of humanized antibodies.
(A) Flowchart of antibody humanization. (B) Humanness score of the heavy and light chains of the humanized antibodies. (C) The ratio of the KD value of the humanized antibodies to the KD value of mAb 40C10. (D) The determination of neutralizing activity of the humanized antibodies. (E) The KD values and IC50 values of the humanized antibodies.
Fig 4.
Evaluation of the prophylactic and therapeutic efficacy of the humanized antibody in vivo.
(A) Experimental design for determining the prophylactic and therapeutic efficacy of the humanized antibody in IFNAR-/- C57BL/6 mice. (B) Survival rate (top) and body weight changes (bottom) of infected mice. (C) The viral loads in the livers and spleens of infected mice were measured by qRT–PCR at 5 d.p.i. (D) Histopathological analyses of humanized antibody HAb-23 treated or untreated infected mice.