Introduction
African swine fever virus is one of the most threatening diseases for
swine industry of the world. World Organization for Animal Health (OIE)
list ASFV as a notifiable disease(Sanchez-Vizcaino, Mur,
Gomez-Villamandos, & Carrasco, 2015). Since ASFV was first identified
in Kenya in 1921, it has spread to most sub-Saharan countries, Europe,
the Caribbean, South America and China(Muñoz-Moreno, Galindo,
Cuesta-Geijo, Barrado-Gil, & Alonso, 2015).. African swine fever is a
highly contagious and lethal viral disease of swine has had a
significant socioeconomic impact in the developed and developing word,
making it a global animal health priority(Agüero et al., 2003). African
swine fever caused by African swine fever virus has caused huge economic
losses to the world pig industry. Since it was first found in Portugal,
up to now, there have been three transcontinental spreading. On the
third transcontinental spread occurred into China in 2018, from 2018 to
2019, more than 169,000 pigs were slaughtered(Zhou et al., 2018).
African swine fever virus (ASFV) is the only one of theAsfarviridae family, it belongs to a 170-194 kb double-stranded
DNA virus(Chapman et al., 2011). The genome encodes for more than 150
polypeptides, at least 50 of which result in production of the
structural proteins that comprise the different domains of the viral
particles(Heimerman et al., 2018). ASFV has more than 100 unique
proteins, such as p30, p54, p72,
pp220, p17, CD2V, p10, p12(Jia, Ou, Pejsak, Zhang, & Zhang, 2017). ASFV
contains at least 68 different structural proteins and 21 cellular
proteins(Alí, Tania, Milagros, & Germán, 2018). Among the structural
proteins, p30 also named p32 which appears early during ASFV
infection(Alonso et al., 2001; Barderas et al., 2001). P30 protein was
determined to be a highly immunogenic protein and stimulates the highest
level of antibody response during ASFV post infection in pig
(Giménez-Lirola et al., 2016).
ASFV p30 protein is an early phosphorylated protein encoded byCP204L gene which is one of the most immunogenic proteins(Afonso
et al., 1992; Prados, Viñuela, & Alcamí, 1993). P30 protein located in
the inner membrane of the viral envelope(Kolontsov, Ustin, Shubina,
Piria, & Makarov, 1992). ASFV p30 protein could induce neutralizing
antibodies in immunized pigs, and p30 was shown to be involved in
various steps of virus attachment and internalization(Giménez-Lirola et
al., 2016). P30 protein is highly immunogenic, which can be expressed at
2 to 4 hours after infection, and then continue the whole infection
cycle(Gómez-Puertas et al., 1998). Therefore, the expression of ASFV p30
indicates that the virus has entered but not coated, and the virus gene
has been expressed. Related studies have shown that p30 protein is the
most diagnostic antigen. So, the diagnosis based on monoclonal antibody
of p30 is of great significance for early prevention and control of
ASF(Petrovan et al., 2019).
In our study, we expressed and purified p30 protein, then produced three
mAbs against p30 protein. Two novel linear p30 B cell epitopes,1MDFILNISMKMEVIFKTDLR20 and26VFHAGSLYNW35 were subsequently
identified using these three mAbs. All of them could be recognized by
anti-ASFV positive sera. Moreover,1MDFILNISMKMEVIFKTDLR20 and26VFHAGSLYNW35 are highly conserved
among 19 genotypes. These findings provide valuable information for
virus diagnosis.