TITLE:
Effect of Viral Antigen Levels on the Serological Response and Efficiency of the Binary Ethylenimine-Inactivated Bluetongue Virus Serotype-16 Vaccine
AUTHORS:
Le Li, Haisheng Miao, Defang Liao, Meiling Kou, Lin Gao, Huachun Li
KEYWORDS:
Blue-Tongue Virus Serotype-16, Binary Ethylenimine-Inactivated Vaccine, Viral Antigen Level, Antibody, Efficiency
JOURNAL NAME:
World Journal of Vaccines,
Vol.6 No.4,
November
30,
2016
ABSTRACT: Bluetongue (BT) is a serious hemorrhagic disease of ruminants caused by bluetongue
virus (BTV). Inactive BTV vaccines have been successful in field trials
in some areas, and inactivated vaccines are considered safer. However, information
about the effect of the viral antigen level on the serological response
and efficiency of the inactive BTV-16 vaccine is lacking. In the present study,
the serological response and efficiency of the viral antigen concentration in
the binary ethylenimine-inactivated Chinese BTV serotype-16 vaccine were
investigated. The viral antigens in the viral suspension (VS) were quantified
using a modified BTV AC-ELISA method. Four batches of vaccine containing
1, 5, 10, and 50 μg/ml of viral antigen were generated from the VS. Four
groups of naive Chinese sheep were vaccinated with the different vaccine
batches, and the serological response and vaccine efficiency were investigated
before and after challenge infection. The vaccines containing 10 and 50 μg/ml
of viral antigen induced significant ELISA and neutralizing antibody titers 14
days after vaccination, whereas the vaccines containing 1 and 5 μg/ml of viral
antigen did not have these effects. A booster immunization at 21 days enhanced
all groups’ antibody titers; however, the increased titer was related to
the viral antigen level. In contrast to the serological response, the viral antigen
level of the vaccines did not have a significant effect on the vaccine efficiency.
With the exception of one sheep from the 5 μg/ml viral antigen group, all vaccinated
sheep from the four antigen level groups showed strong resistance to
infection based on their clinical symptoms, rectal temperatures and viremia.
Collectively, these data suggested that viral antigen levels from 1 to 50 μg/ml had a significant effect on the serological response of the animals but a limited
effect on the vaccine efficiency. The BTV-16 vaccine containing 1 μg/ml of
viral antigen was sufficient to achieve high efficiency, but only the vaccines
with more than 10 μg/ml of antigen induced a significant antibody response.
To obtain a better serological response, we suggest the use of vaccines with
more than 10 μg/ml of viral antigen. The findings in the study will be useful
for BTV vaccine production.