Recombinant linear multiple epitopes of σB protein protect Muscovy ducks against novel duck reovirus infection

Abstract

Infection by the novel duck reovirus (NDRV) in ducklings causes high mortality, which leads to substantial economic losses in the duck industry in China. To date, no commercial vaccine is available for this disease. In this study, linear B cell epitopes of the σB protein of the NDRV were predicted and recombinant multiple linear B cell epitopes (MLBEs) were constructed through linkers. The recombinant MLBEs were then expressed and purified. One-day-old Muscovy ducklings were immunized with different doses of MLBEs and challenged with 5 × 10⁴ ELD₅₀ of the virulent CHY strain of NDRV 14 days after immunization. The ducklings vaccinated with 20 and 40 μg of MLBE performed no clinical signs or gross or histopathological lesions, indicating 100% protection against infection. The viral load in the liver and spleens of these birds was significantly lower than that in the control group. Additionally, these ducklings exhibited positive seroconversion at 7 days after vaccination on enzyme-linked immunosorbent assay. These results indicate that MLBE of σB could be used as a candidate for developing vaccines against NDRV infection.

Keywords: immunization; linear B cell epitopes; novel duck reovirus (NDRV); vaccine; σB protein.

Figure 1

BepiPred linear prediction. Areas above the red line (threshold) are epitopes suggested to be binding to the B cells while the green areas are not.

Figure 2

Expression and purification of MLEB of NDRV σB protein (A) and western-blotting analysis of the purified MLEB protein (B).

Figure 3

Antibodies analysis (A) and survival rate (B). IgY antibodies post MLEB of σB protein were detected by indirect ELISA (A). ns means no significant, *** means p < 0.001.

Figure 4

(A–D) Clinical changes of the livers on 3 DPC. (E–H) Clinical changes of the livers on 5 DPC. (I–L) Clinical changes of the livers on 7 DPC. Red arrowheads means Lesion spots.

Figure 5

(A–D) Clinical changes of the spleens on 3 DPC. (E–H) Clinical changes of the spleens on 5 DPC. (I–L) Clinical changes of the spleens on 7 DPC.

Figure 6

(A–D) Histological changes of the livers on 3 DPC. (E–H) Histological changes of the livers on 5 DPC. (I–L) Histological changes of the livers on 7 DPC.

Figure 7

(A–D) Histological changes of the spleens on 3 DPC. (E–H) Histological changes of the spleens on 5 DPC. (I–L) Histological changes of the spleens on 7 DPC.

Figure 8

The viral RNA amount in the livers (A) and spleens (B) after NDRV challenge. Data are represented as means ± SD. ns means no significant, *means p ≤ 0.05, **means p ≤ 0.01.