A Single Vaccination of IBDV Subviral Particles Generated by Kluyveromyces marxianus Efficiently Protects Chickens against Novel Variant and Classical IBDV Strains

Deqiang Yang,Lixia Zhang,Jinkun Duan,Jungang Zhou,Yao Yu,Hong Lu,Qiang Huang

doi:10.3390/vaccines9121443

Abstract

Infectious bursal disease (IBD), caused by the infectious bursal disease virus (IBDV), is a highly contagious and immunosuppressive disease in chickens worldwide. The novel variant IBDV (nvIBDV) has been emerging in Chinese chicken farms since 2017, but there are no available vaccines that can provide effective protection. Herein, the capsid protein VP2 from nvIBDV strain FJ-18 was expressed in Kluyveromyces marxianus with the aim to produce nvIBDV subviral particles (SVPs). Two recombinant strains constructed for expression of nvIBDV VP2 (nvVP2) and His-tagged VP2 (nvHVP2) formed two types of nvIBDV subviral particles (SVPs), namely nvVP2-SVPs and nvHVP2-SVPs. TEM scans showed that both SVPs were about 25 nm in diameter, but there was a large portion of nvVP2-SVPs showing non-spherical particles. Molecular dynamics simulations indicate that an N-terminal His tag strengthened the interaction of the nvHVP2 monomer and contributed to the assembly of SVPs. Vaccination of chicks with the nvHVP2-SVPs provided 100% protection against novel variant IBDV infection when challenged with the FJ-18 strain, as well as the classical strain BC6/85. By contrast, vaccination with the nvVP2-SVPs only provided 60% protection against their parent FJ-18 strain, suggesting that the stable conformation of subviral particles posed a great impact on their protective efficacy. Our results showed that the nvHVP2-SVPs produced by the recombinant K. marxianus strain is an ideal vaccine candidate for IBDV eradication.

Highlights

Infectious bursal disease is a highly contagious infectious disease caused by the infectious bursal disease virus that leads to severe immunosuppression in chicks and causes huge economic losses to the poultry industry worldwide [1]
The hypervariable region of the FJ-18 VP2 protein was aligned with the same region of other representative strains belonging to the novel variant IBDV (nvIBDV), variant IBDV (vIBDV), very virulent IBDV (vvIBDV), and classical IBDV (cIBDV)
The result showed that the homologies of FJ-18 strain to other nvIBDV isolates were 98.6–100%

Summary

Introduction

Infectious bursal disease is a highly contagious infectious disease caused by the infectious bursal disease virus that leads to severe immunosuppression in chicks and causes huge economic losses to the poultry industry worldwide [1]. Since 2017, a novel variant IBDV (nvIBDV) with a distinct antigenicity from the earlier vIBDV, which gave rise to severe immunosuppression in chicken flocks and that is often associated with secondary infections of virus and pathogenic bacteria, has been emerging in many provinces in China and has brought about great economic losses [6,7,8]. This nvIBDV has been identified in Japan [9] and South Korea [10]. The available commercial vaccines cannot provide complete protection against the nvIBDV infection, and this may be the main reason why nvIBDV spreads so fast among immunized flocks [7]

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Results

Discussion

Conclusion