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A duck enteritis virus-vectored bivalent live vaccine provides fast and complete protection against H5N1 avian influenza virus infection in ducks.

ABSTRACT: Ducks play an important role in the maintenance of highly pathogenic H5N1 avian influenza viruses (AIVs) in nature, and the successful control of AIVs in ducks has important implications for the eradication of the disease in poultry and its prevention in humans. The inactivated influenza vaccine is expensive, labor-intensive, and usually needs 2 to 3 weeks to induce protective immunity in ducks. Live attenuated duck enteritis virus (DEV; a herpesvirus) vaccine is used routinely to control lethal DEV infections in many duck-producing areas. Here, we first established a system to generate the DEV vaccine strain by using the transfection of overlapping fosmid DNAs. Using this system, we constructed two recombinant viruses, rDEV-ul41HA and rDEV-us78HA, in which the hemagglutinin (HA) gene of the H5N1 virus A/duck/Anhui/1/06 was inserted and stably maintained within the ul41 gene or between the us7 and us8 genes of the DEV genome. Duck studies indicated that rDEV-us78HA had protective efficacy similar to that of the live DEV vaccine against lethal DEV challenge; importantly, a single dose of 10(6) PFU of rDEV-us78HA induced complete protection against a lethal H5N1 virus challenge in as little as 3 days postvaccination. The protective efficacy against both lethal DEV and H5N1 challenge provided by rDEV-ul41HA inoculation in ducks was slightly weaker than that provided by rDEV-us78HA. These results demonstrate, for the first time, that recombinant DEV is suitable for use as a bivalent live attenuated vaccine, providing rapid protection against both DEV and H5N1 virus infection in ducks.

SUBMITTER: Liu J

PROVIDER: S-EPMC3194986 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundHighly pathogenic avian influenza virus (AIV) subtype H5N1 remains a threat to poultry. Duck enteritis virus (DEV)-vectored vaccines expressing AIV H5N1 hemagglutinin (HA) may be viable AIV and DEV vaccine candidates.MethodsTo facilitate the generation and further improvement of DEV-vectored HA(H5) vaccines, we first constructed an infectious clone of DEV Chinese vaccine strain C-KCE (DEV(C-KCE)). Then, we generated a DEV-vectored HA(H5) vaccine (DEV-H5(UL55)) based on the bacterial artificial chromosome (BAC) by inserting a synthesized HA(H5) expression cassette with a pMCMV IE promoter and a consensus HA sequence into the noncoding area between UL55 and LORF11. The immunogenicity and protective efficacy of the resulting recombinant vaccine against DEV and AIV H5N1 were evaluated in both ducks and chickens.ResultsThe successful construction of DEV BAC and DEV-H5(UL55) was verified by restriction fragment length polymorphism analysis. Recovered virus from the BAC or mutants showed similar growth kinetics to their parental viruses. The robust expression of HA in chicken embryo fibroblasts infected with the DEV-vectored vaccine was confirmed by indirect immunofluorescence and western blotting analyses. A single dose of 10(6) TCID50 DEV-vectored vaccine provided 100 % protection against duck viral enteritis in ducks, and the hemagglutination inhibition (HI) antibody titer of AIV H5N1 with a peak of 8.2 log2 was detected in 3-week-old layer chickens. In contrast, only very weak HI titers were observed in ducks immunized with 10(7) TCID50 DEV-vectored vaccine. A mortality rate of 60 % (6/10) was observed in 1-week-old specific pathogen free chickens inoculated with 10(6) TCID50 DEV-vectored vaccine.ConclusionsWe demonstrate the following in this study. (i) The constructed BAC is a whole genome clone of DEV(C-KCE). (ii) The insertion of an HA expression cassette sequence into the noncoding area between UL55 and LORF11 of DEV(C-KCE) affects neither the growth kinetics of the virus nor its protection against DEV. (iii) DEV-H5(UL55) can generate a strong humoral immune response in 3-week-old chickens, despite the virulence of this virus observed in 1-week-old chickens. (iv) DEV-H5(UL55) induces a weak HI titer in ducks. An increase in the HI titers induced by DEV-vectored HA(H5) will be required prior to its wide application.

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A duck enteritis virus-vectored bivalent live vaccine provides fast and complete protection against H5N1 avian influenza virus infection in ducks.

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