Development of Diagnostic Tests Provides Technical Support for the Control of African Swine Fever

A highly efficient blocking ELISA based on p72 monoclonal antibody for the detection of African swine fever virus antibodies and identification of its linear B cell epitope

Due to the absence of effective vaccine and treatment, African swine fever virus (ASFV) control is entirely dependent on accurate and early diagnosis, along with culling of infected pigs. The B646L/p72 is the major capsid protein of ASFV and is an important target for developing a diagnostic assays and vaccines. Herein, we generated a monoclonal antibody (mAb) (designated as 2F11) against the trimeric p72 protein, and a blocking ELISA (bELISA) was established for the detection of both genotype I and II ASFV antibodies. To evaluate the performance of the diagnostic test, a total of 506 porcine serum samples were tested. The average value of percent of inhibition (PI) of 133 negative pig serum was 8.4 % with standard deviation (SD) 6.5 %. Accordingly, the cut-off value of the newly established method was set at 28 % (mean + 3SD). Similarly, a receiver operating characteristic (ROC) was applied to determine the cut off value and the p72-bELISA exhibited a sensitivity of 100 % and a specificity of 99.33 % when the detection threshold was set at 28 %. The bELISA was also able to specifically recognize anti-ASFV sera without cross-reacting with other positive serums for other major swine pathogens. Moreover, by designing a series of overlapped p72 truncated proteins, the linear B cell epitope recognized by 2F11 mAb was defined to be 283NSHNIQ288. Amino acid sequence comparison revealed that the amino acid sequence 283NSHNIQ288 is highly conserved between different ASFV isolates. Our findings indicate that the newly established mAb based blocking ELISA may have a great potential in improving the detection of ASFV antibodies and provides solid foundation for further studies.

Development of high-concentration labeled colloidal gold immunochromatographic test strips for detecting african swine fever virus p30 protein antibodies

African Swine Fever (ASF), caused by the African swine fever virus (ASFV), has inflicted significant economic losses on the pig industry in China. The key to mitigating its impact lies in accurate screening and strict biosecurity measures. In this regard, the development of colloidal gold immunochromatographic test strips (CGITS) has proven to be an effective method for detecting ASFV antibodies. These test strips are based on the ASFV p30 recombinant protein and corresponding monoclonal antibodies. The design of the test strip incorporates a high-concentration colloidal gold-labeled p30 recombinant protein as the detection sensor, utilizing Staphylococcal Protein A (SPA) as the test line (T line), and p30 monoclonal antibody as the control line (C line). The sensitivity and specificity of the test strip were evaluated after optimizing the labeling concentration, pH, and protein dosage. The research findings revealed that the optimal colloidal gold labeling concentration was 0.05 %, the optimal pH was 8.4, and the optimal protein dosage was 10 μg/mL. Under these conditions, the CGITS demonstrated a detection limit of 1:512 dilution of ASFV standard positive serum, without exhibiting cross-reactivity with antibodies against other viral pathogens. Furthermore, the test strips remained stable for up to 20 days when stored at 50 °C and 4 °C. Comparatively, the CGITS outperformed commercial ELISA kits, displaying a sensitivity of 90.9 % and a specificity of 96.2 %. Subsequently, 108 clinical sera were tested to assess its performance. The data showed that the coincidence rate between the CGITS and ELISA was 93.5 %. In conclusion, the rapid colloidal gold test strip provides an efficient and reliable screening tool for on-site clinical detection of ASF in China. Its accuracy, stability, and simplicity make it a valuable asset in combating the spread of ASF and limiting its impact on the pig industry.

Colorimetric detection of African swine fever (ASF)-associated microRNA based on rolling circle amplification and salt-induced gold nanoparticle aggregation

African swine fever (ASF) is a severe viral disease with a high mortality rate in domestic and wild pigs, for which no effective vaccine and antiviral drugs are available. The great infectivity of the ASF virus highlights the need for sensitive, simple, and on-site detection assays of ASF. We herein developed a colorimetric sensing strategy for the detection of an ASF-associated miRNA, based on isothermal rolling circle amplification (RCA) and salt-induced gold nanoparticle aggregation. Ssc-miR-451 was selected as the target ASF biomarker due to its high expression in ASF virus-infected pigs. With a red-purple-blue color shifting, this biosensing platform offers convenient detection of ssc-miR-451 with a UV-Vis spectrometer or the naked eye. The proposed assay exhibits a dose-response relationship between the optical absorbance ratio (A525/A640) and the amounts of ssc-miR-451, with a detection limit calculated as 3.56 fmol (equivalent to 11.86 pM in 300 μL reaction mixture). This assay's coefficient of variation (CV%) was determined to be less than 5.95%, revealing its reproducibility is satisfactory. In addition, the newly developed method was successfully applied in the detection of spiked ssc-miR-451 in pig serum samples. In light of its simplicity, convenience (colorimetric), sensitivity, and energy efficiency (isothermal amplification), this biosensing strategy presents great potential to be applied in the local swine industry and pig farming for screening of viral diseases affecting pigs.

Current detection methods of African swine fever virus

African swine fever (ASF), caused by the African swine fever virus (ASFV), is a highly contagious and notifiable animal disease in domestic pigs and wild boars, as designated by the World Organization for Animal Health (WOAH). The effective diagnosis of ASF holds great importance in promptly controlling its spread due to its increasing prevalence and the continuous emergence of variant strains. This paper offers a comprehensive review of the most common and up-to-date methods established for various genes/proteins associated with ASFV. The discussed methods primarily focus on the detection of viral genomes or particles, as well as the detection of ASFV associated antibodies. It is anticipated that this paper will serve as a reference for choosing appropriate diagnostic methods in diverse application scenarios, while also provide direction for the development of innovative technologies in the future.

Brequinar inhibits African swine fever virus replication in vitro by activating ferroptosis

BACKGROUND

African swine fever virus (ASFV) is one of the most fatal swine etiological agents and has a huge economic impact on the global pork industry. Given that no effective vaccines or anti-ASFV drugs are available, there remains a pressing need for novel anti-ASFV drugs. This study aimed to investigate the anti-African swine fever virus (ASFV) activity of brequinar, a DHODH inhibitor.

METHODS

The anti-ASFV activity of brequinar was investigated using IFA, HAD, HAD50, qRT-PCR, and western blotting assays. The western blotting assay was used to investigate whether brequinar inhibits ASFV replication by killing ASFV particles directly or by acting on cell factors. The confocal microscopy and western blotting assays were used to investigate whether brequinar inhibits ASFV replication by activating ferroptosis.

RESULTS

In this study, brequinar was found to effectively inhibit ASFV replication ex vivo in porcine alveolar macrophages (PAMs) in a dose-dependent manner. In kinetic studies, brequinar was found to maintain ASFV inhibition from 24 to 72 hpi. Mechanistically, the time-of-addition assay showed that brequinar exerted anti-ASFV activity in all treatment modes, including pre-, co-, and post-treatment rather than directly killing ASFV particles. Notably, FerroOrange, Mito-FerroGreen, and Liperfluo staining experiments showed that brequinar increased the accumulation of intracellular iron, mitochondrial iron, and lipid peroxides, respectively. Furthermore, we also found that ferroptosis agonist cisplatin treatment inhibited ASFV replication in a dose-dependent manner and the inhibitory effect of brequinar on ASFV was partially reversed by the ferroptosis inhibitor ferrostatin-1, suggesting that brequinar activates ferroptosis to inhibit ASFV replication. Interestingly, exogenous uridine supplementation attenuated the anti-ASFV activity of brequinar, indicating that brequinar inhibits ASFV replication by inhibiting DHODH activity and the depletion of intracellular pyrimidine pools; however, the induction of ferroptosis by brequinar treatment was not reversed by exogenous uridine supplementation, suggesting that brequinar activation of ferroptosis is not related to the metabolic function of pyrimidines.

CONCLUSIONS

Our data confirm that brequinar displays potent antiviral activity against ASFV in vitro and reveal the mechanism by which brequinar inhibits ASFV replication by activating ferroptosis, independent of inhibiting pyrimidine synthesis, providing novel targets for the development of anti-ASFV drugs.

Bridging the Gap: Can COVID-19 Research Help Combat African Swine Fever?

African swine fever (ASF) is a highly contagious and economically devastating disease affecting domestic pigs and wild boar, caused by African swine fever virus (ASFV). Despite being harmless to humans, ASF poses significant challenges to the swine industry, due to sudden losses and trade restrictions. The ongoing COVID-19 pandemic has spurred an unparalleled global research effort, yielding remarkable advancements across scientific disciplines. In this review, we explore the potential technological spillover from COVID-19 research into ASF. Specifically, we assess the applicability of the diagnostic tools, vaccine development strategies, and biosecurity measures developed for COVID-19 for combating ASF. Additionally, we discuss the lessons learned from the pandemic in terms of surveillance systems and their implications for managing ASF. By bridging the gap between COVID-19 and ASF research, we highlight the potential for interdisciplinary collaboration and technological spillovers in the battle against ASF.

A quadruple fluorescence quantitative PCR method for the identification of wild strains of african swine fever and gene-deficient strains

BACKGROUND

Originating in Africa, African swine fever (ASF) was introduced to China in 2018. This acute and highly virulent infectious disease affects domestic pigs. The World Organization for Animal Health has listed it as a statutory reportable disease, and China has listed it as a category A infectious disease.

METHODS

Primers and probes were designed for four ASFV genes (B646L, EP402R, MGF505-3R, and A137R). The primers/probes were highly conserved compared with the gene sequences of 21 ASFV strains.

RESULTS

After optimization, the calibration curve showed good linearity (R2 > 0.99), the minimum concentration of positive plasmids that could be detected was 50 copies/µL, and the minimum viral load detection limit was 102 HAD50/mL. Furthermore, quadruple quantitative polymerase chain reaction (qPCR) with nucleic acids from three porcine-derived DNA viruses and cDNAs from eight RNA viruses did not show amplification curves, indicating that the method was specific. In addition, 1 × 106, 1 × 105, and 1 × 104 copies/µL of mixed plasmids were used for the quadruple qPCR; the coefficient of variation for triplicate determination between groups was < 2%, indicating the method was reproducible.

CONCLUSIONS

The results obtained by testing clinical samples containing detectable EP402R, MGF505-3R, and A137R strains with different combinations of gene deletions were as expected. Therefore, the established quadruple qPCR method was validated for the molecular diagnosis of ASF using gene-deleted ASFV strains.

A Novel Linear B-Cell Epitope on the P54 Protein of African Swine Fever Virus Identified Using Monoclonal Antibodies

The African swine fever virus (ASFV) is a highly infectious viral pathogen that presents a major threat to the global pig industry. No effective vaccine is available for the virus. The p54 protein, a major structural component of ASFV, is involved in virus adsorption and entry to target cells and also plays a key role in ASFV vaccine development and disease prevention. Here, we generated species-specific monoclonal antibodies (mAbs), namely 7G10A7F7, 6E8G8E1, 6C3A6D12, and 8D10C12C8 (subtype IgG1/kappa type), against the ASFV p54 protein and characterized the specificity of these mAbs. Peptide scanning techniques were used to determine the epitopes that are recognized by the mAbs, which defined a new B-cell epitope, TMSAIENLR. Amino acid sequence comparison showed that this epitope is conserved among all reference ASFV strains from different regions of China, including the widely prevalent, highly pathogenic strain Georgia 2007/1 (NC_044959.2). This study reveals important signposts for the design and development of ASFV vaccines and also provides critical information for the functional studies of the p54 protein via deletion analysis.

The Establishment and Application of Indirect 3AB-ELISA for The Detection of Antibodies against Senecavirus A

Senecavirus A (SVA) is an emerging pathogen that negatively affects the pig industry in China. Affected animals present vesicular lesions which are indistinguishable from other vesicular diseases. To date, there is no commercial vaccine that can be used to control SVA infection in China. In this study, recombinant SVA 3AB, 2C, 3C, 3D, L and VP1 proteins are expressed by using a prokaryotic expression system. The kinetics of the presence and levels of SVA antibodies with SVA-inoculated pig serum show that 3AB has the best antigenicity. An indirect enzyme-linked immunosorbent assay (ELISA) is developed with the 3AB protein, exhibiting a sensitivity of 91.3% and no cross-reaction with serum antibodies against PRRSV, CSFV, PRV, PCV2 or O-type FMDV. Given the high sensitivity and specificity of this approach, a nine-year (2014–2022) retrospective and prospective serological study is conducted to determine the epidemiological profile and dynamics of SVA in East China. Although SVA seropositivity declined markedly from 2016 (98.85%) to 2022 (62.40%), SVA transmission continues in China. Consequently, the SVA 3AB-based indirect ELISA has good sensitivity and specificity and is suitable for viral detection, field surveillance and epidemiological studies.

Dynamics of Serological and Mucosal Antibody Responses against African Swine Fever Viruses in Experimentally Infected Pigs

African swine fever virus (ASFV) is a lethal swine pathogen, and there is no effective vaccine or treatment available for ASFV infection. Recently, the occurrence of ASFV genotype I and genotype II natural mutants that manifest as subacute, longer-incubation, or persistent infections poses threats to preventing ASFV infection. The dynamics of antibody responses to ASFV are still completely unrevealed, especially the secretion of mucosal antibodies in oral fluid. Here, a systematic analysis was performed of serological and mucosal antibody secretion against 6 ASFV antigens after direct or indirect infection with four different ASFV strains or genotypes, namely, the field virulent genotype II isolate ASFV HLJ/18, the artificially attenuated genotype II strain HLJ/18-7GD, the naturally attenuated genotype II isolate HLJ/HRB1/20, and genotype I isolate SD/DY-I/21. Severe clinical signs of HLJ/18 infection were observed in pigs from 4 days postinoculation. However, no clinical signs were observed in HLJ/18-7GD-infected pigs. The contact pigs cohoused with the pigs intramuscularly infected with the isolate SD/DY-I/21 or HLJ/HRB1/20 only showed chronic clinical signs. Interestingly, the oral fluid sIgA responses to all the selected antigens were significantly stronger and earlier than the serum IgG responses in both HLJ/18- and HLJ/18-7GD-challenged pigs. Although significant fluctuations and individual differences appeared in oral swab sIgA responses in the contact transmission group, they were earlier than the corresponding serological IgG responses. Moreover, according to the comparative analysis of the three infection groups, P54 was proposed to be a dominant target for serological IgG diagnosis, while P30, CD2v, P54, P22, and P10 were more advantageous as mucosal sIgA diagnosis targets. These results highlight the important role of mucosal antibodies in the early diagnosis of ASFV infection and can provide references to screen appropriate targets for ASFV detection.

Novel sensitive isothermal-based diagnostic technique for the detection of African swine fever virus

A rapid, simple, and sensitive diagnostic technique for the detection of African swine fever virus (ASFV) nucleic acid was developed for testing clinical samples in the field or resource-constrained settings. In the current study, the saltatory rolling-circle amplification (SRCA) technique was used for the first time to detect ASFV. The technique was developed using World Organization for Animal Health (WOAH)-approved primers targeting the p72 gene of the ASFV genome. The assay can be performed within 90 minutes at an isothermal temperature of 58°C without a requirement for sophisticated instrumentation. The results can be interpreted by examination with the naked eye with the aid of SYBR Green dye. This assay exhibited 100% specificity, producing amplicons only from ASFV-positive samples, and there was no cross-reactivity with other pathogenic viruses and bacteria of pigs that were tested. The lower limits of detection of SRCA, endpoint PCR, and real-time PCR assays were 48.4 copies/µL, 4.84 × 10³ copies/µL, and 4.84 × 10³ copies/µL, respectively. Thus, the newly developed SRCA assay was found to be 100 times more sensitive than endpoint and real-time PCR assays. Clinical tissue samples obtained from ASFV-infected domestic pigs and other clinical samples collected during 2020-22 from animals with suspected ASFV infection were tested using the SRCA assay, and a 100% accuracy rate, negative predictive value, and positive predictive value were demonstrated. The results indicate that the SRCA assay is a simple yet sensitive method for the detection of ASFV that may improve the diagnostic capacity of field laboratories, especially during outbreaks. This novel diagnostic technique is completely compliant with the World Health Organization's "ASSURED" criteria advocated for disease diagnosis, as it is affordable, specific, sensitive, user-friendly, rapid and robust, equipment-free, and deliverable. Therefore, this SRCA assay may be preferable to other complex molecular techniques for diagnosing African swine fever.

Preparation of Monoclonal Antibodies against the Viral p54 Protein and a Blocking ELISA for Detection of the Antibody against African Swine Fever Virus

African swine fever virus (ASFV) causes a highly contagious viral disease in domestic and wild pigs, leading to serious economic losses. As there are no vaccines or drugs available, early accurate diagnosis and eradiation of infected animals are the most important measures for ASFV prevention and control. Therefore, improvement of available diagnostic assays and development of novel effective techniques are required. This study is devoted to generating a new detection platform of blocking monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) against ASFV p54 protein. Seven monoclonal antibodies against recombinant p54 protein were produced and four epitopes were identified. Three blocking ELISAs were developed with 6A5 and 6F9 mAbs labeled with HRP, respectively, of which the 6A5/6F9-based blocking ELISA displayed the best detection performance, with an AUC of 0.986, sensitivity of 98.36% and specificity of 92.36% in ROC analysis. Moreover, it has an excellent agreement at 96.59% (198/205) when compared to the commercial blocking ELISA (kappa value = 0.920). The method also has high repeatability, with CV <10%, and no cross reaction with the serum antibodies against PRV, PRRSV, CSFV, PCV2 or SVA. This indicates that the 6A5/6F9-based blocking ELISA has high accuracy with good sensitivity and specificity, suitable for viral detection, field surveillance and epidemiological studies.

An improved luciferase immunosorbent assay for ultrasensitive detection of antibodies against African swine fever virus

African swine fever (ASF), caused by African swine fever virus (ASFV), is a fatal infectious disease of pigs and causes great socioeconomic losses globally. The reliable diagnostic method is critical for prevention and control of the disease. In this study, an improved Luciferase immunosorbent assay (LISA) for detecting ASF was developed using the cell lysates containing ASFV p35 protein fused with a reporter Nano-luciferase (p35-Luc protein). The improved method avoids the complicate procedures of immobilizing the serum samples with protein G in the normal LISA method, and replaced by directly coating the serum samples with carbonate buffer, therefore reduces the productive cost and simplifies the operation procedures. The p35-Luc LISA exhibited high specificity for anti-ASFV sera while no cross-reactions with the sera against other swine viruses. The detection limit of the p35-Luc LISA was shown to be at least four times higher than that of the p35 based indirect ELISA established in our lab. The receiver operating characteristic (ROC) analysis showed the 96.36% relative specificity and 96.97% relative sensitivity of the p35-Luc LISA with the cutoff values of 3.55 as compared to the commercial Ingezim p72-ELISA kit. Furthermore, a total of 248 serum samples were tested by both the p35-Luc LISA and commercial Ingezim p72-ELISA kit, and there was a high degree of agreement (97.6%, kappa = 0.9753) in the performance of the two assays. Collectively, the improved LISA based on the p35-Luc protein could be used as a rapid, ultrasensitive, cost-effective and reliable diagnostic tool for serological survey of ASF in pig farms.

Examination of immunogenic properties of recombinant antigens based on p22 protein from African swine fever virus

Introduction

The single member of the Asfarviridae family is African swine fever virus (ASFV). This double-stranded DNA virus infects wild and farmed swine and loses the pig industry large sums of money. An inner envelope, capsid, and outer envelope are parts of the ASFV particle containing structural proteins playing different roles in the process of infection or host immune defence evasion. When expressed by the baculovirus system, the p22 protein from the inner envelope was found to induce partial protection against a virulent virus strain. This study aimed to express a part of this protein in a different system and evaluate its immunogenicity.

Material and Methods

We designed two proteins, the extracellular (C terminal) part of the p22 protein (p22Ct) and its fusion with the heat-labile enterotoxin B subunit from Escherichia coli (LTB-p22Ct), which is supposed to be a potent enhancer of the immune response. Both proteins were produced in the E. coli expression system and subsequently used for mice immunisation to analyse their safety and immunogenicity.

Results

The protein fused with LTB did not show the expected adjuvant properties and did not prove safe, because abscess formation was observed after immunisation. In contrast, immunisation with the p22Ct protein alone induced a higher antibody titre but caused no adverse symptoms.

Conclusion

These results show the high potential of the p22Ct region as an immunogenic protein for ASFV serological detection purposes.

Cell Lines for the Development of African Swine Fever Virus Vaccine Candidates: An Update

African swine fever virus (ASFV) is the etiological agent of a highly lethal disease in both domestic and wild pigs. The virus has rapidly spread worldwide and has no available licensed vaccine. An obstacle to the construction of a safe and efficient vaccine is the lack of a suitable cell line for ASFV isolation and propagation. Macrophages are the main targets for ASFV, and they have been widely used to study virus–host interactions; nevertheless, obtaining these cells is time-consuming and expensive, and they are not ethically suitable for the production of large-scale vaccines. To overcome these issues, different virulent field isolates have been adapted on monkey or human continuous cells lines; however, several culture passages often lead to significant genetic modifications and the loss of immunogenicity of the adapted strain. Thus, several groups have attempted to establish a porcine cell line able to sustain ASFV growth. Preliminary data suggested that some porcine continuous cell lines might be an alternative to primary macrophages for ASFV research and for large-scale vaccine production, although further studies are still needed. In this review, we summarize the research to investigate the most suitable cell line for ASFV isolation and propagation.

Stem cell-derived porcine macrophages as a new platform for studying host-pathogen interactions

BACKGROUND

Infectious diseases of farmed and wild animals pose a recurrent threat to food security and human health. The macrophage, a key component of the innate immune system, is the first line of defence against many infectious agents and plays a major role in shaping the adaptive immune response. However, this phagocyte is a target and host for many pathogens. Understanding the molecular basis of interactions between macrophages and pathogens is therefore crucial for the development of effective strategies to combat important infectious diseases.

RESULTS

We explored how porcine pluripotent stem cells (PSCs) can provide a limitless in vitro supply of genetically and experimentally tractable macrophages. Porcine PSC-derived macrophages (PSCdMs) exhibited molecular and functional characteristics of ex vivo primary macrophages and were productively infected by pig pathogens, including porcine reproductive and respiratory syndrome virus (PRRSV) and African swine fever virus (ASFV), two of the most economically important and devastating viruses in pig farming. Moreover, porcine PSCdMs were readily amenable to genetic modification by CRISPR/Cas9 gene editing applied either in parental stem cells or directly in the macrophages by lentiviral vector transduction.

CONCLUSIONS

We show that porcine PSCdMs exhibit key macrophage characteristics, including infection by a range of commercially relevant pig pathogens. In addition, genetic engineering of PSCs and PSCdMs affords new opportunities for functional analysis of macrophage biology in an important livestock species. PSCs and differentiated derivatives should therefore represent a useful and ethical experimental platform to investigate the genetic and molecular basis of host-pathogen interactions in pigs, and also have wider applications in livestock.

One-pot platform for rapid detecting virus utilizing recombinase polymerase amplification and CRISPR/Cas12a

The livestock industry has been deeply affected by African swine fever virus (ASFV) and Capripoxvirus (CaPV), which caused an enormous economic damage. It is emergent to develop a reliable detection method. Here, we developed a rapid, ultra-sensitive, and one-pot DNA detection method combining recombinase polymerase amplification (RPA) and CRISPR/Cas12a for ASFV and CaPV, named one-pot-RPA-Cas12a (OpRCas) platform. It had the virtue of both RPA and CRISPR/Cas12a, such as high amplification efficiency, constant temperature reaction, and strict target selectivity, which made diagnosis simplified, accurate and easy to be operated without expensive equipment. Meanwhile, the reagents of RPA and CRISPR/Cas12a were added to the lid and bottom of tube in one go, which overcame the incompatibility of two reactions and aerosol contamination. To save cost, we only need a quarter of the amount of regular RPA per reaction which is enough to achieve clinical diagnosis. The OpRCas platform was 10 to 100 times more sensitive than qPCR; the limit of detection (LOD) was as low as 1.2 × 10^-6 ng/µL (3.07 copies/µL by ddPCR) of ASFV and 7.7 × 10^-5 ng/µL (1.02 copies/µL by ddPCR) of CaPV with the portable fluorometer in 40 min. In addition, the OpRCas platform combined with the lateral flow assay (LFA) strip to suit for point-of-care (POC) testing. It showed 93.3% consistency with qPCR for clinical sample analysis. Results prove that OpRCas platform is an easy-handling, ultra-sensitive, and rapid to achieve ASFV and CaPV POC testing. KEY POINTS: • The platform realizes one-pot reaction of RPA and Cas12a. • Sensitivity is 100 times more than qPCR. • Three output modes are suitable to be used to quantitative test or POC testing.

Current efforts towards safe and effective live attenuated vaccines against African swine fever: challenges and prospects

Background

African swine fever (ASF) is a fatal hemorrhagic disease in domestic pigs and wild boar caused by African swine fever virus (ASFV). Since ASF has been introduced into Europe and Asia, the major pig-raising areas, posing a huge threat to the pork industry worldwide. Currently, prevention and control of ASF are basically dependent on strict biosecurity measures and stamping-out policy once ASF occurs.

Main text

The major risks of ASF spread are insufficient biosecurity measures and human behaviors. Therefore, a safe and effective vaccine seems to be a reasonable demand for the prevention and control of ASF. Due to the efficacy advantage over other types of vaccines, live attenuated vaccines (LAVs), especially virulence-associated genes deleted vaccines, are likely to be put into emergency and conditional use in restricted areas if ASF is out of control in a country with a huge pig population and pork consumption, like China. However, the safety, efficacy, and genetic stability of current candidate ASF LAVs require comprehensive clinical evaluations prior to country-wide field application. Several critical issues need to be addressed to commercialize an ideal ASF LAV, including a stable cell line for manufacturing vaccines, differentiation of infected from vaccinated animals (DIVA), and cross-protection from different genotypes.

Conclusion

A safe and effective DIVA vaccine and an accompanying diagnostic assay will facilitate the prevention, control, and eradication of ASF, which is quite challenging in the near future.

Graphical Abstract