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Research Project: Development of Safe Vaccination Protocols for Pregnant Sows, Piglets and Boars Using ASFV-G-DI177L

Location: Foreign Animal Disease Research

Project Number: 3022-32000-063-039-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2023
End Date: Aug 31, 2026

(i) Conduct studies to evaluate the safety and efficacy of ASFV-G-DI177L in pregnant sows developing vaccination protocols to immunize sows without affecting pregnancy, fetal viability and the development of the newborn piglets. (ii) Assess the influence of maternal immunity in the ability of piglets to develop an efficacious protective immune response after vaccination.

Experiment 1: Detection of the presence of potential residual virulence in pregnant sows after administration of vaccine candidate ASFV-G-DI177L. The objective of this experiment is to determine the presence of potential adverse effects in the reproductive efficacy of pregnant sows by the vaccination with ASFV-G-DI177L. 1.a Sows (n=8/time point) will be IM inoculated with 103.5 HAD50 (target expected maximum release dose for the vaccine – see VS Memorandum 800.207) of ASFV-G-DI177L to test the safety of 1) a one dose regimen at each period of pregnancy and 2) the safety of a two dose regimen with the booster dose given during the estimated most sensitive period, as follows: 1) one dose administered (i) first, (ii) second, and (iii) third period of pregnancy and 2) one dose administered right before insemination and a second booster dose administered in the third period of pregnancy. Control sham vaccinated (i.e., not vaccinated) groups for each vaccine regimen should be included. 1.b Pregnant sows will be evaluated on daily basis for a minimum of 21 days post-vaccination and held until parturition to determine their clinical status and their reproductive efficiency in delivering healthy litters (1). 1.c Presence of viremia (2), virus shedding (2), and virus specific antibodies (3) in sows will be evaluated at the time of vaccination and parturition, and the piglets until 21 days after partum (see Experiment 2: efficacy of maternally-derived antibodies in protecting piglets from ASFV). (1) Number, body weight and daily weight gain of the newborn piglets. (2) Titer the presence of infectious virus in primary swine macrophage cultures. (3) Determine virus specific antibody titers by PIADC ELISA. Results will indicate if vaccination with ASFV-G-DI177L is responsible of producing adverse reproductive effect when administered at any specific time during the pregnancy. In addition, this experiment will provide information if there is a safe/optimal time for ASFV-G-DI177L vaccination in terms of inducing strong ASFV specific antibody responses. Experiment 2: Efficacy of ASFV-G-DI177L induced maternally derived antibodies in protecting piglets from ASF. 2.a Piglets 21 days old obtained from Experiment 1 above (non-vaccinated controls and vaccinated sows from each of the three periods of pregnancy, including the one dose versus two dose vaccine regimen in the third period will be challenged IM with 102.0 HAD50 highly virulent Vietnamese strain TTKN/ASFV/DN/2019. A litter of piglets born from a mock vaccinated sow will be included as control. 2.b All piglets will be observed for ASF clinical signs for a period of a minimum of 21 days post-challenge and tested at the end of the observation period for the presence of viremia , virus shedding, and virus specific antibodies, as performed in Experiment 1.c, pregnant sow safety study.