Recombinant Lactococcus Expressing a Novel Variant of Infectious Bursal Disease Virus VP2 Protein Can Induce Unique Specific Neutralizing Antibodies in Chickens and Provide Complete Protection.

Hongyu Cui,Changjun Liu,Li Gao,Xiaole Qi,Qing Pan,Xiaomei Wang,Kai Li,Jielan Mi,Yulong Gao,Tingting Wang,Yulong Wang,Yanping Zhang,Zhihao Wang

doi:10.3390/v12121350

Abstract

Recent reports of infectious bursal disease virus (IBDV) infections in China, Japan, and North America have indicated the presence of variant, and the current conventional IBDV vaccine cannot completely protect against variant IBDV. In this study, we constructed recombinant Lactococcus lactis (r-L. lactis) expressing a novel variant of IBDV VP2 (avVP2) protein along with the Salmonella resistance to complement killing (RCK) protein, and Western blotting analysis confirmed that r-L. lactis successfully expressed avVP2-RCK fusion protein. We immunized chickens with this vaccine and subsequently challenged them with the very virulent IBDV (vvIBDV) and a novel variant wild IBDV (avIBDV) to evaluate the immune effect of the vaccine. The results show that the r-L. lactis-avVP2-RCK-immunized group exhibited a 100% protection rate when challenged with avIBDV and 100% survival rate to vvIBDV. Furthermore, this immunization resulted in the production of unique neutralizing antibodies that cannot be detected by conventional ELISA. These results indicate that r-L. lactis-avVP2-RCK is a promising candidate vaccine against IBDV infections, which can produce unique neutralizing antibodies that cannot be produced by other vaccines and protect against IBDV infection, especially against the variant strain.

Highlights

Infectious bursal disease virus (IBDV), known as Gumboro, is the causative agent of a highly infectious disease in chickens
We found that r-L. lactis-a novel variant of IBDV VP2 (avVP2)-resistance to complement killing (RCK) could induce the body to produce a high level of unique specific neutralizing antibodies, which provided complete immune protection against a novel variant wild IBDV (avIBDV), and the survival rate could reach 100% after the challenge with very virulent IBDV (vvIBDV)
The index of the r-L. lactis-avVP2-RCK group chickens was not significantly different from that of the Gt live vaccine group and the blank control group chickens (p > 0.05) (Figure 4B). These results show that r-L. lactis-avVP2-RCK immunization can completely protect against avIBDV-SHG19

Summary

Introduction

Infectious bursal disease virus (IBDV), known as Gumboro, is the causative agent of a highly infectious disease in chickens. The main features of infectious bursal disease (IBD) is an infection of the central organ of the immune system and the damage of B lymphocytes in the bursa of Fabricius [1,2]. IBD can cause strong immunosuppression in chickens [3], affect the immunological effects of multiple vaccines, such as Newcastle disease, Avian infectious bronchitis, and Chicken. IBD has received significant attention from the poultry industry, where chickens are protected by vaccination [1]. Since conventional commercial vaccines cannot provide complete protection against such variant strains [9,12], there is an urgent need to develop a variant IBDV vaccine

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