Current approaches to the vaccine development for African swine fever (review)

African swine fever (ASF), first described in 1921 by R.E. Montgomery (R.E. Montgomery, 1921), has been a major problem in pig production for over 100 years. The search for effective and universal specific vaccine variants started back in 1933 (J. Walker, 1933). This article presents a literature review on the most important and successful events in the history of ASF vaccine development, presenting the approaches on developing attenuated (C. Muñoz-Pérez et al, 2021), inactivated (E. Cadenas-Fernández et al., 2021), subunit (J.G. Neilan et al., 2004) and live vectored (J.K. Jancovich et al., 2018) vaccines. The widespread use of naturally attenuated non-hemadsorbing isolates as vaccines in the second half of the 20th century in European countries led to a persistent chronic ASF infection in a big number of pigs (J. Manso Ribeiro et al., 1963). Successive passages of field isolates of the ASF virus in many cell cultures did not show the proper result in weakening the virulent properties of the pathogen, despite genetic changes in the virus genome (I. Titov et al., 2017). Only modern technologies (e.g., homologous recombination and CRISPR-Cas9 genome editing) for obtaining genetically modified virus ASFV-G-ΔI177L by deleting specific genes in the genome led to the creation of effective candidate vaccines (M.V. Borca et al., 2020). Inactivated, as well as subunit vaccines based on recombinant proteins, caused the formation of specific humoral immune responses in high titers, but did not confer protective properties (G. Burmakina et al., 2016). Live vectored vaccines have become a new milestone in the fight against infectious animal diseases, in particular ASF; human adenovirus 5 (rAd) and modified vaccinia Ankara (MVA) are among the vectors for the development of such vaccines (L.C. Goatley et al., 2020). Attenuated vaccines based on genetically modified viruses with a deletion of specific genes I226R and 18-7GD require international expertise for further registration and use in veterinary practice.