Current State of Global African Swine Fever Vaccine Development under the Prevalence and Transmission of ASF in China

Abstract

African swine fever (ASF) is a highly lethal contagious disease of swine caused by African swine fever virus (ASFV). At present, it is listed as a notifiable disease reported to the World Organization for Animal Health (OIE) and a class one animal disease ruled by Chinese government. ASF has brought significant economic losses to the pig industry since its outbreak in China in August 2018. In this review, we recapitulated the epidemic situation of ASF in China as of July 2020 and analyzed the influencing factors during its transmission. Since the situation facing the prevention, control, and eradication of ASF in China is not optimistic, safe and effective vaccines are urgently needed. In light of the continuous development of ASF vaccines in the world, the current scenarios and evolving trends of ASF vaccines are emphatically analyzed in the latter part of the review. The latest research outcomes showed that attempts on ASF gene-deleted vaccines and virus-vectored vaccines have proven to provide complete homologous protection with promising efficacy. Moreover, gaps and future research directions of ASF vaccine are also discussed.

Mechanism of interaction between virus and host is inferred from the changes of gene expression in macrophages infected with African swine fever virus CN/GS/2018 strain

“…ASFV is harmful pathogen to pigs. Since 2018, it has caused huge economic losses to the pig industry in China [ 9 ]. Macrophages are major target cells of ASFV, and they are also important immune cells of the host [ 26 ].…”

“…Since 2018, a highly virulent type II ASFV has spread to China. ASFV has dealt a heavy blow to China, the world's largest producer and consumer of pork [ 9 ]. Although the experimental vaccine was produced by a natural, cell culture attenuated, or genetically modified ASFV, no effective vaccine has yet been produced.…”

African Swine Fever Virus as a Difficult Opponent in the Fight for a Vaccine—Current Data

“…Finding an effective antigen for a subunit vaccine is not straightforward [ 80 ]. As previously thought, ASFV is unable to induce neutralizing antibodies, whereas many decades of research on convalescent pig serum have allowed for the discovery and description of several ASFV proteins (p30, p54, p72, CD2v, EP153R, p12, D117L, and pp62) [ 4 ]. P72, P30, and P54 are considered to be the most significant antigenic proteins that cause humoral immune responses during infection.…”

“…In these studies, two experiments were conducted in succession, with positive findings in the second experiment, where six out of six pigs were protected from lethal doses of the virulent genotype I of ASFV strain OUR T 88/1. The number of survivors after vaccination with the same antigen pool differed between the two experiments, possibly because the immune dosage of the recombinant viral vector was raised and an immune system overreaction was treated with flunixin meglumine (a non-steroidal anti-inflammatory drug) on day 5 after challenge, relative to experiment 1, which protected two out of six pigs from lethal doses of the virulent OUR T 88/1 isolate [ 4 ]. Although all vaccinated animals were viremic and developed disease symptoms, the proposed combination offers hope for the development of an efficacious subunit vaccine.…”

“…In China, which produces about 53% of the world’s pork, production dropped by 29.1%. Obviously, such losses from the ASF pandemic have tremendous consequences for the international trade of pig products [ 4 ].…”