Recombinant duck enteritis viruses expressing the Newcastle disease virus (NDV) F gene protects chickens from lethal NDV challenge

Highlights

• The first report of recombinant duck enteritis virus (DEV) expressing the F or HN protein of the Newcastle disease virus.

• rDEV-F provides 100% survival protection against NDV challenge in chickens.

• 104TCID50 dose of rDEV-F is sufficient for inducing protection against lethal NDV challenge.

Abstract

Newcastle disease virus (NDV) is a major threat to poultry worldwide. Virulent Newcastle disease virus infection can cause 100% morbidity and mortality in chickens. Vaccination is the most effective way to prevent and control NDV outbreaks in poultry. Previously, we demonstrated that a duck enteritis virus (DEV) vaccine strain is a promising vector to generate recombinant vaccines in chickens. Here, we constructed two recombinant DEVs expressing the F protein (rDEV-F) or HN protein (rDEV-HN) of NDV. We then evaluated the protective efficacy of these recombinant DEVs in specific-pathogen-free chickens. rDEV-F induced 100% protection of chickens from lethal NDV challenge after a single dose of 10⁴ TCID₅₀, whereas rDEV-HN did not induce effective protection. rDEV-F may therefore serve as a promising vaccine candidate for chickens. This is the first report of a DEV-vectored vaccine providing robust protection against lethal NDV infection in chickens.

Introduction

Newcastle disease (ND) is caused by virulent strains of ND viruses (NDVs), ND is a highly contagious and pathogenic disease in chickens leading to major economic losses in the poultry industry worldwide, and is classified by the World Organization for Animal Health (OIE) as a notifiable disease (Dimitrov et al., 2016). NDV is a single-stranded, negative-sense, non-segmented RNA virus that belongs to the genus Avulavirus of the family Paramyxoviridae. The NDV genome is approximately 15.2 kb in length, containing six genes that encode six structural proteins in the order 3’-NP, (nucleocapsid)-P, (phosphoprotein)-M, (matrix)–F, (fusion)-HN (hemagglutinin-neuraminidase)-L, and (large polymerase)-5’, and the nonstructural protein V (Chambers and Samson, 1982).

The F and HN proteins of NDV are surface glycoproteins. The F protein mediates the fusion of the viral envelope to the host cell membrane (Nagai et al., 1989). The HN protein possesses both receptor recognition and neuraminidase activities (Morrison et al., 1991). The F and HN proteins play important roles in virus attachment, entry, and release (Yusoff and Tan, 2001). Hence, the F and HN proteins are neutralizing and protective antigens of NDV, which makes them primary targets for anti-viral vaccine development (Boursnell et al., 1990; Ge et al., 2016; Lee et al., 2008; Loke et al., 2005; Park et al., 2014).

Vaccination is the most effective way to prevent and control ND in poultry, especially in regions where ND is endemic (Dimitrov et al., 2017). Live attenuated vaccine, such as that derived from the LaSota strain developed in the 1940’s, has been widely used to prevent NDV infection (Miller et al., 2010). Although these kinds of vaccine were very effective, they raised biosafety concerns. More recently, recombinant vaccines have shown promise polyvalent or antigen-delivery vaccines. Recombinant vaccines expressing F or HN of NDV have been developed by using different viral vectors such as Vaccinia virus (Meulemans et al., 1988), Fowlpox virus (Boursnell et al., 1990; Karaca et al., 1998), Pigeonpox virus (Letellier et al., 1991), Herpesvirus of turkeys (Reddy et al., 1996), Marek’s disease virus (Sakaguchi et al., 1998) and avian adeno-associated virus (Perozo et al., 2008). Several of these recombinant virus vaccines have been licensed in certain countries for use in poultry.

As a member of the family Herpesviridae, Duck enteritis virus (DEV) possesses a large genome (approximately 158 kb), composed of a unique long (UL) region and a unique short (US) region, with the US region flanked by inverted repeat sequences (IRS and TRS) (Li et al., 2009). Previously, we successfully constructed a new recombinant duck enteritis virus, rDEV-re6, by inserting the HA gene of H5N1 influenza virus between the US7 and US8 genes of the DEV vaccine strain. rDEV-re6 is safe for chickens and induced a solid immune response in them after a single dose (Liu et al., 2013). The DEV vaccine strain is therefore a promising vector to generate recombinant vaccines expressing other antigens of infectious disease pathogens of chickens.

In this study, we generated two recombinant DEVs containing the F or HN gene of the NDV LaSota strain inserted between the US7 and US8 genes of the DEV vaccine strain and evaluated their protective efficacy in specific-pathogen-free (SPF) chickens against lethal NDV challenge.