A Bivalent Human Adenovirus Type 5 Vaccine Expressing the Rabies Virus Glycoprotein and Canine Distemper Virus Hemagglutinin Protein Confers Protective Immunity in Mice and Foxes.

Lina Yan,Hongbin He,Lele Liu,Tong Xu,Li Tian,Wenwen Zheng,Xianwei Wang,Xuexing Zheng,Xianghong Xue,Zhongxin Zhao

doi:10.3389/fmicb.2020.01070

Lina Yan, Hongbin He + Show 8 more

Open Access

https://doi.org/10.3389/fmicb.2020.01070

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Abstract

The development of a safe and efficient multivalent vaccine has great prospects for application. Both rabies virus (RABV) and canine distemper virus (CDV) are highly infectious antigens, causing lethal diseases in domestic dogs and other carnivores worldwide. In this study, a replication-deficient human adenovirus 5 (Ad5)-vectored vaccine, rAd5-G-H, expressing RABV glycoprotein (G) and CDV hemagglutinin (H) protein was constructed. The RABV G and CDV H protein of rAd5-G-H were expressed and confirmed in infected HEK-293 cells by indirect immunofluorescence assay. The rAd5-G-H retained a homogeneous icosahedral morphology similar to rAd5-GFP under an electron microscope. A single dose of 108 GFU of rAd5-G-H administered to mice by intramuscular injection elicited rapid and robust neutralizing antibodies against RABV and CDV. Flow cytometry assays indicated that the dendritic cells and B cells in inguinal lymph nodes were significantly recruited in rAd5-G-H-immunized mice in comparison with the mock and rAd5-GFP groups. rAd5-G-H also activated the Th1- and Th2-mediated cell immune responses against RABV and CDV in mice, which contributed to 100% survival of a lethal-dose RABV challenge without any clinical signs. In foxes, a single dose of 109 GFU of rAd5-G-H could elicit high levels of neutralizing antibodies against both RABV and CDV in comparison with the mock and rAd5-GFP groups. All foxes in the rAd5-GFP and mock groups died, while the foxes inoculated with rAd5-G-H all survived and showed no clinical signs of disease after being challenged with a lethal wild-type CDV strain. These results suggested that rAd5-G-H has great potential as a bivalent vaccine against rabies and canine distemper in highly susceptible dogs and wildlife animals.

Highlights

Both rabies virus (RABV) and canine distemper virus (CDV) cause fatal diseases in carnivores
The expressions of the RABV G and CDV H genes in HEK-293 cells infected with rAd5-G-H, rAd5-green fluorescence protein (GFP), or Dulbecco’s modified Eagle’s medium (DMEM) were detected by indirect immunofluorescence
Positive reaction signals against anti-RABV G monoclonal antibody and anti-CDV polyclonal serum were observed in rAd5-G-H-infected HEK293 cells, while negative red signals were seen in HEK-293 cells infected with rAd5-GFP (Figure 1B)

Summary

Introduction

Both rabies virus (RABV) and canine distemper virus (CDV) cause fatal diseases in carnivores. The majority (95%) of cases are transmitted from the bites or scratches of infected animals and occur in developing countries in Africa and Asia, especially in rural areas, where animal rabies vaccinations are not paid enough attention (Jackson, 2013; World Health Organization, 2013). The G protein of a nonpathogenic RABV, as a major antigen determinant, plays a critical role in eliciting virus-neutralizing antibodies (VNAs) and developing protective host immune responses (Jackson, 2013; Astray et al, 2017). Virus-neutralizing antibody levels higher than 0.5 IU/mL are considered to be sufficient to protect susceptible species from rabies infection, since the VNAs are mainly directed against the surface G protein of the RABV (Zhao et al, 2019). The design of a novel rabies vaccine focuses on the RABV G protein (Astray et al, 2017)

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