Classical swine fever (CSF) is a highly contagious disease caused by the classical swine fever virus (CSFV)[11]. The high incidence and mortaligy of CSF threatens the pig industry, and CSF is an acute and highly infectious disease among farmed animal industries worldwide[12, 13]. Vaccination against CSFV has controlled the epidemic of classical swine fever to a certain extent. However, because of the immune suppression caused by CSFV, the level of effective neutralized antibodies caused by the vaccine is low, so immunization cannot adequately prevent a CSF epidemic.
As an important tool in modern life science research, the monoclonal antibody technique covers the hybridoma technique, phage display technology, single B cell antibody preparation technique and so on[14]. Antibodies prepared by the hybridoma technique have high immunogenicity and a short half-life period, which leads to an unsatisfactory clinical efficacy[15]. Because of its simplicity and convenience, phage display technology is the most widely used method in antibody preparation. However, due to the random assortment of heavy and light chains, the native mating of heavy and light chains in antibodies cannot be maintained[16]. Currently, as an emerging technology, single B cell antibody preparation is a technique that clones and expresses single antigen-specific B cell antibody genes in vitro. This technique reserves the native mating of heavy and light chains, and has the advantages of good genetic diversity, high efficiency and low cell requirement[17]. Therefore, in this study, we used a B cell antibody was used for focus to acquire a single-chain antibody to CSFV.
A neutralizing antibody is an important factor in antiviral immunity and is also a key index to analyze the immune effect of vaccines[18]. Neutralizing antibodies kill viruses by neutralizing infectious virus particles, thus preventing viral infection and eliminating pathogens[19]. Currently, the vaccine is mainly developed by selecting protective antigens and inducing immune neutralizing antibodies to neutralize a viral infection. However, the protective antigens of viruses that can induce immunosuppression often fail to induce effective neutralizing antibodies, resulting in an unsatisfactory immune response. Therefore, designing the design of vaccines that can induce highly effective neutralizing antibodies has attracted more attention. Research on neutralizing antibodies in humans has developed rapidly, especially in the fields of AIDS, hepatitis A and hepatitis B. The current method is to establish an antibody gene library through a phage vector expression system, especially the pCom3 expression system, to screen and obtain anti-viral neutralizing and monoclonal antibodies, which can directly prepare antibodies or antibody vaccines in vitro for emergency immunoprophylaxis and treatment. Currently, human monoclonal antibodies against influenza virus, anti-HbsAg, anti-respiratory syncytial virus (RSV) F protein, anti-herpes simplex virus, anti-HIV gp120 and anti-hepatitis C virus have been successfully screened by this technology[20–24].
Currently, the idea of animal vaccine research is to express protective antigens of pathogens and to stimulate the body to produce antibodies. However, only some of these antibodies have a neutralizing viral activity, and can be identified as neutralizing antibodies, addition, the remaining antibodies have no neutralizing activity. Therefore, although the vaccine can induce a high level of antibodies, the immune effect is not ideal. In addition, pathogens with an immunosuppressive function can inhibit immunity. In that case, the immune system cannot arouse an effective immune response to eliminate pathogens, so the protective antigen cannot be used as an ideal vaccine to obtain an effective immune reaction.
In summary, the development of neutralizing antibodies and human vaccines has shown good prospects for their use. However, further research is needed for antibody vaccines. There are few studies on neutralizing antibodies in animal diseases, and no antibody vaccines have been reported. In this study, we renovated the design idea of vaccines using protective antigens as an immunogen and constructed a neutralizing antibody vaccine against CSF. The vaccine has the characteristics of producing a rapid neutralizing antibody and strong pertinence of antibodies. This method improves the effective immune levels and provides a new means for the immune prevention of CSF. On the one hand, neutralizing antibody production is effective and targeted; on the other hand, neutralizing antibodies can directly neutralize the virus without influencing the body's immune system.