Location: Foreign Animal Disease Research2012 Annual Report
1a. Objectives (from AD-416):
The objective of this collaborative agreement is to gain a better understanding of specific immune response to Foot-and-Mouth Disease Virus (FMDV) infection and vaccination and to identify the genetic basis of animals with high and low responder phenotypes. The objectives are: 1. to describe the early steps of the specific immune response against FMDV infection, 2. to describe the immune response elicited by inactivated FMDV vaccination, and 3. to determine the heritability of the response to FMDV vaccination in cattle populations.
1b. Approach (from AD-416):
1. The early steps of specific immune response against FMDV infection will be done through infection by aerosol inoculation delivery route and subsequent virus detection of respiratory tissues through immunostaining and real-time RT-PCR will be done. Replication sites will be correlated to anti-FMDV antibody-producing cells and studied. 2. The immune response elicited by inactivated FMDV vaccination will be studied. Cells responsible for antibody production will be determined through ELISpot assay and analyzed for protective response elicted by inactivated FMDV vaccines. These cells will genotyped with the aim of correlating host genotype with host resistance/recovery after experimental infection or induction of protection post vaccination. Results obtained from in vivo experiments will then be compared to in vitro responses. 3. The heritability of response to FMDV vaccination will be conducted studies of vaccinated bovine populations in Argentina with known pedigree. Estimates of heritability will be calculated to assess host genetic influence to FMDV vaccination response. These estimates will be used to assess merit of further efforts to identify bovine strains purported to demonstrate enhanced levels of innate resistance to FMDV. This will determine if selection for host resistance is possible and if significant gentetic differentiation is possible to identify.
3. Progress Report:
The aim of this project is to better understand the specific immune response to Foot-and-Mouth Disease Virus (FMDV) infection and vaccination and to identify the genetic basis of animals with high and low responder phenotypes. In FY 2012 studies were conducted on the local adaptive responses induced in cattle vaccinated and further infected through the oronasal route. Animals were intramuscularly vaccinated with serotype O1 Campus monvalent FMD oil vaccine and studied at different times post-vaccination and post-oronasal challenge. Samples were collected and analyzed using FMDV-ASC ELISpot and Interferon-gamma (IFN-y) levels through IFN-y ELISpot. Analysis of the results indicated that even though none of the vaccinated animals showed FMD clinical symptoms after viral challenge, mucosal stimulation following intramuscular administration of a high-payload FMDV-inactivated oil vaccine was poor. A modest, though consistent stimulation in all mucosal-related lymphoid tissues was detected only at 29 days post vaccination. Results indicated that after 4 weeks, vaccination may induce a basal stimulation in lymphoid tissues associated to the cattle respiratory tract. This may be related to the circulation of viral antigens or FMDV primed-immune cells to other lymph nodes in the respiratory tract. In addition, studies were conducted on the heritability factors involved in the response to FMDV vaccination. Paired whole blood samples were obtained from 377 animals in the study herd. Samples were taken the same day prior to primo vaccination in the frame of the official FMD vaccination campaigns in Argentina and at 45 days post vaccination. The animals received commercial tetravalent FMD oil vaccines formulated with inactivated FMDV from A24 Cruzeiro/Brazil/55.A/Argentina/20012, 01 Campus/Brazil/58 and C3/Indaial/Brazil/71 strains. The total FMDV-specific antibody response were determined against 3 viral strains belonging to serotypes with recent regional circulation. Anti-FMD antibody titers were analyzed to discard calves with FMDV-specific colostral antibodies from their vaccinated dams before vaccination. Analysis of the results indicated that the antibody responses induced after primo-vaccination were homogenously high for all calves assayed. In addition, the hierarchical mixed regression models showed that the sire is a random effect, and did not improve the fit of the model for any of the three virus strains. However, the sire’s breed was a significant for the thee strains, resulting in an antibody response to FMD vaccination at 45 dpv significantly lower the progeny of Jersey compared to Holstein.