Single immunization with the attenuated strain “Volgograd/14c” of the ASF virus does not protect piglets from infection with the homologous strain “Stavropol 01/08”

After the introduction of the ASF virus to Georgia in 2007, the disease spread to many countries in Europe and Asia. In present time, ASF has been registered in 42 countries of the Eurasian continent. Strict anti-epizootic measures are used to eradicate the disease, including stamping out policies, bans on import and export of all types of animals, trade bans, etc. In order to prevent the disease, different vaccine candidates have been developed, such as inactivated, live attenuated, subunit, vector and DNA vaccines. Unfortunately, in many cases, trials of these vaccine candidates have been unsuccessful. The aim of the work was to study the immunobiological and protective properties of the attenuated ASF virus strain “Volgograd/14c” against infection with the homologous virulent strain “Stavropol 01/08” in vivo. A single intramuscular inoculation of the attenuated strain “Volgograd/14s” at a dose of 10^3,0HAU₅₀см³ to six pigs caused 1–4 day hyperthermia (40.0-40.8^oC) without the development of other clinical signs. Viremia in the blood of inoculated pigs was detected from day 3–7 in titers of 2.0-3.0 lg HAU₅₀см³, with a maximum accumulation of 3.75 lg HAU₅₀см³ on day 10, a decrease on days 14–21 to 1.75–2.75 lg HAU₅₀см³ and loss of infectivity by day 28. Virus-specific antibodies to the ASF virus were detected in the serum of vaccinated animals from day 10. Challenge with the homologous virulent strain “Stavropol 01/08” caused the development of clinical signs and the growth of viremia in the blood to 6.0–7.5 lg HAU₅₀см³ in all pigs of the experimental and control groups. The course of the disease was hyperacute, acute, subacute and chronic with the death of all control animals and 5 of 6 experimental pigs with clinical signs and pathological changes characteristic to ASF.

1. Blome S., Franzke K., Beer M. African swine fever – A review of current knowledge. Virus Research. 2020;287:198099. DOI: https://doi.org/10.1016/j.virusres.2020.198099

2. Tran X. H., Le T. T. P., Nguyen Q. H., Do T. T., Nguyen V. D., Gay C. G., et al. African swine fever virus vaccine candidate ASFV-G-ΔI177L efficiently protects European and native pig breeds against circulating Vietnamese field strain. Transboundary and Emerging Diseases. 2022;69(4):e497–e504. DOI: https://doi.org/10.1111/tbed.14329

3. Chathuranga K., Lee J-S. African swine fever virus (ASFV): Immunity and vaccine development. Vaccines. 2023;11(2):199. DOI: https://doi.org/10.3390/vaccines11020199

4. Argilaguet J. M., Perez-Martin E., Nofrarias M., Gallardo C., Accensi F., Lacasta A., et al.   DNA vaccination partially protects against African swine fever virus lethal challenge in the absence of antibodies. PLos One. 2012;7(9):e40942. DOI: https://doi.org/10.1371/journal.pone.0040942

5. Cadenas-Fernández E., Sánchez-Vizcaíno J. M., Born E., Kosowska A., Kilsdonk E., Fernández-Pacheco P. et al. High Doses of Inactivated African Swine Fever Virus Are Safe, but Do Not Confer Protection against a Virulent Challenge. Vaccines   (Basel). 2021;9(3):242. DOI: https://doi.org/10.3390/vaccines9030242

6. Blome S., Gabriel C., Beer M. Modern adjuvants do not enhance the efficacy of an inactivated African swine fever virus vaccine preparation. Vaccine. 2014;32(31):3879–3882. DOI: https://doi.org/10.1016/j.vaccine.2014.05.051

7. Stone S., Hess W. Antibody response to inactivated preparations of African swine fever virus in pigs. American Journal of Veterinary Research. 1967;28:475–481.

8. Pérez-Núñez D., Sunwoo S. Y., García-Belmonte R., Kim C., Vigara-Astillero G., Riera E. et al. Recombinant African swine fever virus Arm/07/CBM/c2 lacking CD2v and A238L Is attenuated and protects pigs against virulent Korean Paju strain. Vaccines. 2022;10(12):1992. DOI: https://doi.org/10.3390/vaccines10121992

9. Abkallo H. M., Svitek N., Oduor B., Awino E., Henson S. P., Oyola S. O. et al. Rapid CRISPR/Cas9 editing of genotype IX African swine fever virus circulating in eastern and central Africa. Frontiers in Genetics. 2021;12:733674. DOI: https://doi.org/10.3389/fgene.2021.733674

10. Borca M. V., Holinka L. G., Berggren K. A., Gladue D. P. CRISPR-Cas9,   a tool to efficiently increase the development of recombinant African swine fever viruses. Scientific Reports. 2018;8(1):3154. DOI: https://doi.org/10.1038/s41598-018-21575-8

11. Krug P. W., Holinka L. G., O'Donnell V., Reese B., Sanford B., Fernandez-Sainz I. et al. The progressive adaptation of a Georgian isolate of African swine fever virus to Vero cells leads to a gradual attenuation of virulence in swine corresponding to major modifications of the viral genome. Journal of Virology. 2015;89(4):2324–2332. DOI: https://doi.org/10.1128/JVI.03250-14

12. Vlasov М. Е., Nefedeva М. V., Kudryashov D. A.,   Titov I. A. Determination of the 1L-5-6L MGF110 genes influence on the biological properties of the African swine fever virus (Asfarviridae; Asfivirus) “Volgograd/14C” in vivo. Acta Veterinaria. 2024;74(2):210–221. DOI: https://doi.org/10.2478/acve-2024-0014

13. Sereda A. D., Vlasov M. E., Koltsova G. S., Morgunov S. Y., Kudrjashov D. A., Sindryakova I. P. et al. Immunobiological characteristics of the attenuated African swine fever vitus strain Katanga-350. Viruses. 2022;14(8):1630. DOI: https://doi.org/10.3390/v14081630

14. Borca M., Ramirez-Medina E., Silva E., Vuono E., Rai A., Pruitt S. et al. Development of a Highly Effective African Swine Fever Virus Vaccine by Deletion of the I177L Gene Results in Sterile Immunity against the Current Epidemic Eurasia Strain. Journal Virology. 2020;94(7):e02017-19. DOI: https://doi.org/10.1128/JVI.02017-19

15. Guide for the Care and Use of Laboratory Animals: Eighth Edition. Washington, DC: The National Academies Press, 2011. 246 p. URL: https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf

16. King K., Chapman D., Argilaguet J. M., Fishbourne E., Hutet E., Cariolet R. et al. Protection of European domestic pigs from virulent African isolates of African swine fever virus by experimental immunisation. Vaccine. 2011;29(28): 4593–4600. DOI: https://doi.org/10.1016/j.vaccine.2011.04.052

17. Fernández-Pinero J., Gallardo C., Elizalde M., Robles A., Gómez C., Bishop R. et al. Molecular diagnosis of African Swine Fever by a new real-time PCR using universal probe library. Transboundary and Emerging Diseases. 2013;60(1):48–58. DOI: https://doi.org/10.1111/j.1865-1682.2012.01317.x

18. Sereda A. D, Namsrayn S., Balyshev V. M., Vlasov M. E, Sindryakova I. P., Koltsova G., Kolbasov D. V. Seroimmunotyping of African swine fever virus. FrontiersMicrobiology. 2023;14:1225587. DOI: https://doi.org/10.3389/fmicb.2023.1225587

19. Morgunov Yu. P., Morgunov S. Yu., Burmakina G. S., Malogolovkin A. S., Kushnir S. D., Titov I. A., Mima K. A., Kolbasov D. V. Strain of African swine fever virus of the 8th serotype adapted to the transplanted culture of COS-1 cells: Patent RF no.  2575079, 2016. URL: https://patents.s3.yandex.net/RU2575079C1_20160210.pdf

20. Sereda A. D., Vlasov M. E., Koltsova G. S., Morgunov S. Y., Kudrjashov D. A., Sindryakova I. P. et al. Immunobiological Characteristics of the Attenuated African Swine Fever Virus Strain Katanga-350. Viruses. 2022;14(8):1630. DOI: https://doi.org/10.3390/v14081630

21. Vlasov M. E., Sindryakova I. P., Kudrjashov D. A., Morgunov S. Y., Kolbasova O. L., Lyska V. M. et al. Inoculation with ASFV-Katanga-350 Partially Protects Pigs from Death during Subsequent Infection with Heterologous Type ASFV-Stavropol 01/08. Viruses. 2023;15(2):430. DOI: https://doi.org/10.3390/v15020430

22. Vlasov M., Sindryakova I., Kudryashov D., Morgunov S., Kolbasova O., Lyska V., et al. Administration Routes and Doses of the Attenuated African Swine Fever Virus Strain PSA-1NH Influence Cross-Protection of Pigs against Heterologous Challenge. Animals. 2024;14(9):1277. DOI: https://doi.org/10.3390/ani14091277

23. Abrams C. C., Goatley L., Fishbourne E., Chapman D., Cooke L., Oura Ch. A. et al. Deletion of virulence associated genes from attenuated African swine fever virus isolate OUR T88/3 decreases its ability to protect against challenge with virulent virus. Virology. 2013;443(1):99–105. DOI: https://doi.org/10.1016/j.virol.2013.04.028

24. Leitão A., Cartaxeiro C., Coelho R., Cruz B., Parkhouse R. M. E., Portugal F. C. et al. The non-haemadsorbing African swine fever virus isolate ASFV/NH/P68 provides a model for defining the protective anti-virus immune response. Journal of General Virology. 2001;82(3):513–523. DOI: https://doi.org/10.1099/0022-1317-82-3-513

25. Yang X., Zhang X., Zhao X., Yuan M., Zhang K., Dai J. et al. Antibody-Dependent Enhancement: ″Evil″ Antibodies Favorable for Viral Infections. Viruses. 2022;14(8):1739. DOI: https://doi.org/10.3390/v14081739

26. Chen W., Zhao D., He X., Liu R., Wang Z., Zhang X. et al. A seven-gene-deleted African swine fever virus is safe and effective as a live attenuated vaccine in pigs. Science China Life Sciences. 2020;63:623–634. DOI: https://doi.org/10.1007/s11427-020-1657-9

27. O’Donnell V., Holinka L. G., Gladue D. P., Sanford B., Krug P. W., Lu X. et al. African Swine Fever Virus Georgia Isolate Harboring Deletions of MGF360 and MGF505 Genes Is Attenuated in Swine and Confers Protection against Challenge with Virulent Parental Virus. Journal of Virology. 2015;89(11):6048–6056. DOI: https://doi.org/10.1128/JVI.00554-15

28. Koltsov A., Sukher M., Krutko S., Belov S., Korotin A., Rudakova S. et al. Construction of the First Russian Recombinant Live Attenuated Vaccine Strain and Evaluation of Its Protection Efficacy Against Two African Swine Fever Virus Heterologous Strains of Serotype 8. Vaccines (Basel). 2024;12(12):1443. DOI: https://doi.org/10.3390/vaccines12121443

29. Zheng L., Yan Z., Qi X., Ren J., Ma Z., Liu H. et al. The Deletion of the MGF360-10L/505-7R Genes of African Swine Fever Virus Results in High Attenuation but No Protection Against Homologous Challenge in Pigs. Viruses. 2025;17(2):283. DOI: https://doi.org/10.3390/v17020283

30. Sawant J., Patil A., Kurle S. A Review: Understanding Molecular Mechanisms of Antibody-Dependent Enhancement in Viral Infections. Vaccines (Basel). 2023;11(7):1240. DOI: https://doi.org/10.3390/vaccines11071240

31. Gaudreault N. N., Richt J. A. Subunit Vaccine Approaches for African Swine Fever Virus. Vaccines (Basel). 2019;7(2):56. DOI: https://doi.org/10.3390/vaccines7020056

32. Yang X., Sun E., Zhai H., Wang T., Wang S., Gao Yu. et al. The antibodies against the A137R protein drive antibody-dependent enhancement of African swine fever virus infection in porcine alveolar macrophages. Emerging Microbes & Infections. 2024;13(1):2377599. DOI: https://doi.org/10.1080/22221751.2024.2377599