African swine fever virus vaccine candidate ASFV-G-¿I177L efficiently protects European and native pig breeds against circulating Vietnamese field strain.

Authors: TRAN, XUAN HANH - Navetco National Veterinary Joint Stock Company; LE THI THU, PHUONG - Navetco National Veterinary Joint Stock Company; NGUYEN QUANG, HUY - Navetco National Veterinary Joint Stock Company; DO THANH, THUY - Navetco National Veterinary Joint Stock Company; NGUYEN VAN, DUNG - Navetco National Veterinary Joint Stock Company; Gay, Cyril; Borca, Manuel; Gladue, Douglas

Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2021
Publication Date: 9/28/2021
Citation: Tran, X., Le Thi Thu, P., Nguyen Quang, H., Do Thanh, T., Nguyen Van, D., Gay, C.G., Borca, M.V., Gladue, D.P. 2021. African swine fever virus vaccine candidate ASFV-G-I177L efficiently protects European and native pig breeds against circulating Vietnamese field strain. Transboundary and Emerging Diseases. https://doi.org//10.1111/tbed.14329.
DOI: https://doi.org/10.1111/tbed.14329

Interpretive Summary: African swine fever virus (ASFV) causes a devastating disease in swine, called African swine fever (ASF), that is currently spreading across Europe and Asia. There is no available vaccine for ASF, and currently only experimental live attenuated vaccines are derived from deletions of individual genes in the ASFV genome. In this study we were able to further evaluate a previously discovered experimental vaccine ASFV-G-dI177L, in Vietnam, using local Vietnamese pigs and a Vietnamese field strain of ASFV for challenge.

Technical Abstract: The recent spread of African swine fever (ASF) in the People’s Republic of China and neighboring countries in Asia has had significant economic consequences with an estimated direct cost of $55 billion - $130 billion (Weaver and Habib, 2020). This pandemic, originally detected in Republic of Georgia in 2007, has devastated the swine industry in large geographical areas of Southeast Asia with 14 countries reporting ASF outbreaks since the first documented case was confirmed in Liaoning Province, China, on 3 August 2018. In the absence of any available vaccines, the control of ASF relies on the detection and culling of infected animals. The United States Department of Agriculture, recently developed a recombinant experimental vaccine candidate, ASFV-G-'I177L, by deleting the I177L gene from the genome of the highly virulent pandemic ASFV strain Georgia, which efficaciouly protects pigs from the parental virus. Here, the initial studies were extended demonstrating that ASFV-G-'I177L is able to protect pigs against the virulent ASFV isolate currently circulating and producing disease in Vietnam with similar efficacy as reported against the Georgia strain. Comparative studies performed using a large number of pigs of European and Vietnamese origin demonstrated that a minimum protective dose of 102 HAD50 of ASFV-G-'I177L equally protects animals of both breeds. In concurrence with those results, onset of immunity in these animal breed showed appearance of protection in approximately one-third of the animals by the second week post vaccination, with full protection achieved by the fourth week post vaccination. Therefore, results presented here demonstrated that ASFV-G-'I177L is able to induce protection against virulent Vietnameese ASFV field strains and is effective in protecting local breeds of pigs as efficiently as previously shown for European cross-bred pigs. To our knowledge, this is the first report showing the efficacy of a Georgia 2007 based vaccine candidate in Asian breed of pigs or challenged with an Asian ASFV strain.