Location: Foreign Animal Disease Research
Project Number: 3022-32000-063-046-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2025
End Date: Jun 30, 2027
Objective:
The objectives of this agreement is the evaluation of the effect of vaccination with the ARS developed Classical Swine Fever (CSF) FlagT4G strain on the reproductive capacity of sows as well as the efficacy of vaccination in protecting these animals against the infection with the parental virulent field strain. FlagT4G is a recombinant live attenuated DIVA compatible vaccine developed by ARS which has been shown to be safe and efficacious in growing pigs. The potential negative effect of CSF live attenuated vaccines in the reproductive performance of sows is a World Organization for Animal Health (WOAH) requirement for the regulatory approval for the commercial use of any live attenuated vaccine.
Approach:
Classical swine fever (CSF) remains one of the most significant challenges to swine health worldwide, being endemic in many countries in Central and South America, as well as in Southeast Asia, including China and Russia. Due to its severe economic and public health impact, CSF is notifiable to the World Organization for Animal Health (WOAH). FlagT4G is a recombinant live attenuated DIVA compatible vaccine developed by ARS which has been shown to be safe and efficacious in growing pigs. Controlling CSF requires a DIVA-capable vaccine capable of conferring early protection against all forms of the disease, including protection against trans placental transmission of the virus. It is proposed to evaluate first the safety of FlagT4G vaccination in pregnant sows and the second, the capacity of CSFV FlagT4G vaccine to confer protection in pregnant sows against trans placental transmission of a highly virulent CSFV strain using a vaccine dose suitable for large-scale production and commercial scaling. To this end, vaccine efficacy will be evaluated at both 44 and 72 days of gestation. Trials will be conducted in parallel with the C-strain vaccine. Pregnant sows will be vaccinated with FlagT4G at 44 days into gestation with a dose which is feasible for future commercial scaling. In parallel, a group vaccinated with commercial C strain will be included as control. At 65 days of gestation, half of the animals will be challenged with a highly virulent CSFV. The non challenged reminding animals will be evaluated for the detection of potential reproductive abnormalities induced by vacciation. After vaccination and CSFV challenge recorded clinical signs and virological and immunological parameters will be determined.
In addition, new DIVA and molecular diagnostic tools will be developed to differentiate FlagT4G-vaccinated animals from those vaccinated with C-strain or animals infected with field strains of CSFV. Both molecular and serological DIVA tools will be designed and validated. A genomic test will be developed to identify and differentiate animals vaccinated with FlagT4G from animals vaccinated with other vaccines such as C-strain, and from animals infected with field strains of CSFV. Likewise, a new DIVA serological test will be developed with the aim of positively marking the specific antibody response generated exclusively by FlagT4G, as a positive DIVA test.