Abstract
Suid Herpesvirus 1 (SHV-1) is the etiological agent of Aujeszky’s disease (AD), which affects swine herds worldwide and causes substantial economic losses due to animal mortality and lost productivity. In order to eradicate SHV-1, vaccination programs using viruses lacking the gene encoding glycoprotein E (gE) are ongoing in several countries. These eradication programs have generated a currently unmet demand for affordable and sensitive tests that can detect SHV-1 infection, yet distinguish between infected and vaccinated pigs. To meet this demand, we used the baculovirus-insect cell system to produce immunologically authentic full-length recombinant gE protein for use in a serum ELISA assay. As previous efforts to clone the gE gene had failed due to its extremely high GC-content (75% average), we used betaine as a PCR enhancer to facilitate amplification of the entire gE gene from the Argentinian CL15 strain of SHV-1. The cloned gE gene was expressed at high levels in recombinant baculovirus-infected insect cells and reacted strongly with sera from SHV-1 infected pigs. We used the recombinant gE protein to develop a local indirect ELISA test with sensitivity and specificity comparable to currently available commercial tests. Thus, recombinant gE produced in baculovirus-infected insect cells is a viable source of antigen for the detection of SHV-1 in ELISA tests. We also provide evidence supporting a potential application of this recombinant form of gE as a SHV-1 subunit vaccine.
Highlights
Suid Herpesvirus 1 (SHV-11), known as Pseudorabies virus (PRV), is a double-stranded DNA virus that is the etiologic agent of Aujeszky’s disease (AD) in swine [1]
The SHV-1 glycoprotein E (gE) open reading frame (ORF) is extremely GC-rich, with an average of 74.8%, a low of approximately 56%, and a high of approximately 94% GC when analyzed by a sliding window approach (50 base pair window, Fig. 1a)
BLASTp analysis revealed that the CL-15 gE protein is similar to gE proteins encoded by several other SHV-1 strains isolated across the world (Table 1)
Summary
Suid Herpesvirus 1 (SHV-11), known as Pseudorabies virus (PRV), is a double-stranded DNA virus that is the etiologic agent of Aujeszky’s disease (AD) in swine [1]. A major development in the control of this disease has been the use of marker vaccines consisting of viral particles lacking specific structural proteins in combination with serological tests that detect serum antibodies against these structural proteins, which enable differentiation between infected and vaccinated pigs [6]. In Argentina, a voluntary vaccination program was implemented in 1998, using a gE-deleted imported vaccine. The vaccine and differential test were discontinued between 2001 and 2002 due to an economic crisis and the use of this vaccine is currently prohibited by Argentinian authorities (Resolution 474/2009 SENASA (National Service of Animal Health) (www.senasa.gov.ar)
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