A Single Mutation at Position 120 in the Envelope Protein Attenuates Tembusu Virus in Ducks.

Dawei Yan,Xiaogang Wu,Xingpo Liu,Jianmei Yang,Qinfang Liu,Ying Shi,Xin Su,Zejun Li,Binbin Wang,Qiaoyang Teng,Xuesong Li,Xintao Ni,Haiwang Wang

doi:10.3390/v14030447

Abstract

A live attenuated duck Tembusu virus (TMUV) vaccine FX2010-180P (180P) was successfully utilized to prevent TMUV infections in ducks in China. Compared with wild-type TMUV, 180P was highly attenuated and lost transmissibility in ducks. However, the mechanism of the attenuation of 180P remains poorly understood. To explore the key molecular basis of attenuation, chimeric and site mutant viruses in the background of the wild-type TMUV-FX2010 (FX) strain were rescued, and the replication, tissue tropism, and transmissibility were characterized in ducks. The results show that the envelope (E) protein was responsible for attenuation and loss of transmission in ducks. Further studies showed that a D120N amino acid mutation located in domain II of the E protein was responsible for the attenuation and transmissibility loss of 180P in ducks. The D120N substitution resulted in an extra high-mannose type N-linked glycosylation (NLG) in the E protein of 180P compared with the wild-type TMUV, which might restrict the tissue tropism and transmissibility of TMUV in ducks. Our findings elucidate that N120 in the E protein is a key molecular basis of TMUV attenuation in ducks and provide new insight into the role of NLG in TMUV tissue tropism and transmissibility.

Highlights

Published: 22 February 2022Tembusu virus (TMUV) belongs to the Ntaya virus group within the genus Flavivirus, family Flaviviridae [1]
To identify whether the E protein was critical to the attenuation and transmissibility of TMUV in vitro and in ducks, the chimeric virus FX/180PE with switched 180P E gene in the background of FX was rescued (Figure 1A)
Significantly lower viral titers were found in spleens of ducks inoculated with FX-ED120N, and no virus was detected in lungs, kidneys, and ovaries of ducks in the FX-ED120N group (Figure 3D). These results indicate that the ED120N mutation restricted the tissue tropism of FX in ducks

Summary

Introduction

TMUV belongs to the Ntaya virus group within the genus Flavivirus, family Flaviviridae [1]. TMUV has quickly spread in ducks through the country and has become endemic in China since. Most of the viruses in the genus Flavivirus, family Flaviviridae, are arboviruses, transmitted by mosquitoes or other arthropods, such as Dengue virus (DENV), Zika virus (ZIKV), Japanese encephalitis virus (JEV), West Nile virus (WNV), etc. Our previous study showed that the newly emerged TMUV obtained direct-contact and aerosol transmissibility in ducks, which made the virus spread quickly among ducks even in the winter season in Northern China [8]. TMUV is the first flavivirus in the family Flaviviridae that has aerosol transmissibility among the host, while the underlying mechanism remains unclear

Methods

Results

Conclusion