[Elicitation of protective immune responses by a recombinant adenovirus expressing hemagglutinin of H3N2 SIV in swine]

Abstract

Objective: To evaluate the immunity of the adenovirus recombinant rAd-HA-GFP encoding an H3N2 swine influenza virus hemagglutinin.

Methods: Thee groups of 6-week-old pigs (5 pigs per group) were vaccinated intramuscularly with the recombinant, one group was immunized with 10(-8) TCID50 recombinant adenovirus rAd-HA-GFP, the other groups were vaccinated with 2 x 10(-8) TCID50 and 4 x 10(-8) TCID50. A control groups (5 pigs) were vaccinated with recombinant adenovirus rAd-GFP. Virus-specific hemagglutination-inhibition (HI) antibody was detected by 2-6 weeks post vaccination. Compared the difference of vaccinated intramuscularly, intragastric administration and intranasal inoculation, three groups of different HI antibody pigs and one control group were challenged with a virulent H3N2 field virus.

Results: The results showed that pigs in the groups given higher immunizing dose were developed higher levels HI antibody. All of vaccinated intramuscularly, intragastric administration and intranasal inoculation could produce HI antibody, but the titer of vaccinated intramuscularly was higher significantly (P < 0.01). Three groups of pigs (5 pigs per group) which HI titers were 1:80, 1:160, 1:320 respectively were challenged with a virulent H3N2 field virus, include the negative control group. The immunization efficacy was evaluated by clinical signs, the rate of virus isolation and HI titer. It suggested that immunological response induced by rAd-HA-GFP could resist attack of SIV effectively.

Conclusion: The adenovirus vaccines rAd-HA-GFP are efficacious for SIV and have the additional advantage over commercial vaccines that suckling piglets have no pre-existing maternally-derived antibody to block early life vaccination.