The Immunogenicity and Protective Efficacy of DNA Vaccine Coding For NA1 Gene of Highly Pathogenic Avian Influenza H5N1 Subtype

Abstract

Control of avian influenza infection depends mainly on biosafety measures and vaccination, DNA vaccination is a novel method to generate antigen-specific antibody and cell-mediated immunity. In the current study, a DNA vaccine for full-length N1 gene was developed in a trial to decrease the severity of avian influenza virus spread and shedding. Full-length N1 gene was cloned in entry clone pENTER SD/TOPO, followed by homologous recombination with the destination mammalian expression vector (PDEST 40). The PDEST 40-N1 was used in the immunization of SPF chickens. Potency was evaluated through the survival rate that reaches 65%, which was far less than the commercially available inactivated vaccine. Meanwhile, the shedding of the virus from dead birds was 0.46 Log 10 EID50. At the same time, the most surprising result was the shedding level of the vaccinated live birds that were zero shedding ;on the other hand, the inactivated vaccine could not reduce the shedding level which remains very high (3.2 Log 10 EID50 ). IFN-γ transcript level in the DNA vaccinated group was detected by the 3rd-day post-vaccination and remained upregulated till the 28th post-vaccination. After the challenge, the level of IFN-γ was much higher until 14 days post-challenge. The inactivated vaccine could not stimulate any detectable level post-vaccination. These data suggested the ability of DNA vaccine coding for N1 gene of avian influenza to combat the virus shedding from live birds and could be used in combination with DNA vaccine coding for H5 to produce maximum protection with zero shedding.

Keywords

• avian influenza
• haemagglutinin gene
• neuraminidase gene
• dna vaccine
• n1