Abstract
African swine fever virus (ASFV) is the causative agent of the epidemic of African swine fever (ASF), with virulent strains having a mortality rate of up to 100% and presenting devastating impacts on animal farming. Since ASF was first reported in China in 2018, ASFV still exists and poses a potential threat to the current pig industry. Low-virulence and genotype I strains of ASFV have been reported in China, and the prevention and control of ASF is more complicated. Insufficient understanding of the interaction of ASFV with the host immune system hinders vaccine development. Physical barriers, nonspecific immune response and acquired immunity are the three barriers of the host against infection. To escape the innate immune response, ASFV invades monocytes/macrophages and dendritic cells, thereby inhibiting IFN expression, regulating cytokine expression and the body’s inflammatory response process. Meanwhile, in order to evade the adaptive immune response, ASFV inhibits antigen presentation, induces the production of non-neutralizing antibodies, and inhibits apoptosis. Recently, significant advances have been achieved in vaccine development around the world. Live attenuated vaccines (LAVs) based on artificially deleting specific virulence genes can achieve 100% homologous protection and partial heterologous protection. The key of subunit vaccines is identifying the combination of antigens that can effectively provide protection and selecting carriers that can effectively deliver the antigens. In this review, we introduce the epidemic trend of ASF and the impact on the pig industry, analyze the interaction mechanism between ASFV and the body’s immune system, and compare the current status of potential vaccines in order to provide a reference for the development of effective ASF vaccines.
Highlights
In 1921, African swine fever virus (ASFV) was first reported in Kenya, which caused about an 100% mortality in infected domestic pigs [1]
ASFV infection of cells resulted in increased expression of SLA-DOA and SLA-DOB, which inhibited the binding of antigenic peptides to MHCII [40]
Low-virulence and genotype I strains of ASFV have been reported in China, and the prevention and control of ASF is more complicated
Summary
In 1921, ASFV was first reported in Kenya, which caused about an 100% mortality in infected domestic pigs [1]. The genotype II ASFV was introduced to Georgia in the Caucasus region and started a new round of transmission in 2007 [5] Afterwards, it spread to the Russian Federation, Ukraine and Belarus, and in 2014 it spread to Eastern European countries [4,5]. According to OIE, from January 2020 to January 2022, ASF outbreaks were reported in 35 countries or regions around the world, including 4767 cases (1043334 animals lost) in domestic pigs and 18,262 cases (29970 animals lost) in wild boars [9]. Since most pig farms in China are small-scale pig farms with very low biosecurity levels, the rapid spread of ASFV across the country has led to a serious reduction in the number of live pigs and caused heavy losses to the pig industry [11]. It is necessary to regularly collect and detect the presence of ASFV in pig herds, and to ensure the removal and safe destruction of positive pig herds to eliminate the source of infection [12]
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