Of the seven serotypes of foot-and-mouth disease virus (FMDV) strains circulating globally, serotype Asia1 has been effectively eradicated in China through systematic vaccination in livestock. The structural characteristics of serotype Asia1 may enhance its immunogenicity compared to other serotypes. Herein, we present a preliminary exploration of Asia1-binding B-cell receptor repertoire, containing 3571 clones, and identified 17 porcine-derived neutralizing monoclonal antibodies (pnAbs) from the top 33 high-frequency clonotypes. The majority of pnAbs (14/17) recognized the epitopes on VP2, with a common determinant at residue 72 (D) on the B-C loop; two pnAbs (2/17) recognized a novel epitope spanning VP2 and VP3; and the remaining one (1/17) bound to the C-terminus of VP1. Furthermore, the antigenic structures on VP2 and spanning VP2 and VP3 were respectively elucidated by determining the cryo-EM structures of FMDV serotype Asia1 in complexes with two pnAbs, PAS5 and PAS12. The light chain of PAS5, forming the majority of contact sites with the viral particle, focuses on the βB, B-C loop, βC and H-I loop of VP2, with key determinants at residues 68, 72 and 77 around the three-fold axis, corresponding to antigenic site 2. The contact sites of both VH and VL of PAS12 uncover a novel antigenic structure comprising the B-C, and H-I loops on VP2, and the B-B knob and βB on VP3, with key determinants at residue 73 on VP2 and 59 on VP3. Subsequently, site-directed competitive ELISA analysis of sera from primary and booster vaccinated pigs revealed a balanced antibody response profile, suggesting a potentially even immunodominance among antigenic site 2, VP1 G-H loop, and the novel antigenic structure spanning VP2 and VP3 on FMDV serotype Asia1. Compared to the focused immunodominance observed in other serotypes, this balanced antigenic recognition across VP1, VP2, and VP3 of FMDV serotype Asia1 reflects a diversified antibody response that may contribute to effective neutralization and protection.

The whole life cycle of the highly pathogenic foot-and-mouth disease virus (FMDV) significantly depends on the host determinants to achieve its infection. ATG16L1 is well known to be required to form the autophagosomes membrane at the early steps of autophagy, while its non-autophagic roles in FMDV infection remain unclear. We found that following entry, FMDV O/Fujian/CHA/5/99 trafficked to early endosomes (EEs) and the trans-Golgi network (TGN), bypassing late endosomes (LEs) /lysosome and recycling endosomes (REs). This specific intracellular distribution mirrored the vesicular sorting pathway involving ATG16L1 that had been reported previously. Further analyses showed that ATG16L1 increased the internalization of FMDV and recruited EEs to facilitate the initial phase of FMDV infection. However, ATG16L1 degraded FMDV 2BC protein in the Golgi via its non-autophagic function to inhibit late stages of FMDV infection. To counteract this, membrane-associated 2BC interacted with ATG16L1 and mediated its reduction via the caspase pathway, thereby sustaining FMDV replication. In conclusion, our evidence suggested that ATG16L1 played dual roles in regulating the life cycle of FMDV.

Recently, serotype O foot-and-mouth disease viruses (FMDVs) belonging to four lineages (O/ME-SA/PanAsia, O/ME-SA/Ind2001, O/SEA/Mya-98, and O/Cathay) co-circulate in China, and the emergence of new variant viruses belonging to the Cathay lineage renders the existing vaccines less effective, which poses a serious threat to the livestock industries. The surface-exposed G-H loop of the VP1 structural protein of FMDV plays an important role in inducing neutralizing antibodies, generation of antigenic variants, and virus attachment. Here, we generated three recombinant FMDVs in which the G-H loops have been substituted with the corresponding sequences from the circulating strains of the PanAsia, Mya-98, and Cathay lineages based on an infectious cDNA clone of a chimeric FMDV, which carries amino acid substitutions in the leader protein and all surface proteins of FMDV O/XJ/CHA/2017. All mutant viruses exhibited a significantly improved replication capacity in BHK-21 cells and displayed relatively larger plaque morphologies compared with the parental virus. Chemically inactivated vaccines prepared from the parental virus and the mutant viruses all induced protective liquid-phase blocking ELISA (LPBE) antibodies against FMDVs in pigs after 28 days post vaccination (dpv), but only the vaccine with the substitution of the G-H loop of the Cathay strain induced protective neutralizing antibodies against the viruses of four lineages, while other vaccines exhibited excellent immunological cross-reactivity to the viruses of Ind2001, PanAsia, and Mya-98 lineages but did not for the Cathay virus at 28 dpv. Our studies indicated that the G-H loop of the Cathay virus plays a critical role in the antigenic drift of FMDV, which will provide key insights for designing porcinophilic FMDV vaccines in the future. • The swapping of the G-H loops of FMDVs notably improved replication capacity of FMDV in BHK-21 cells. • The swapping of the G-H loop of the Cathay virus obviously broadens antigenic coverage of FMDV vaccine. • The study showed that the G-H loop of the Cathay virus plays a critical role in antigenic drift of FMDV.

The E2 subunit vaccine has been considered a promising alternative to an attenuated classical swine fever (CSF) vaccine. However, it fails to induce a good cellular immune response. Given that immunogenic adjuvants can regulate the cellular immunity to achieve a maximum efficacy against antigens, immunostimulatory effects of porcine IL-28B on the CSF virus (CSFV) E2 subunit vaccine were evaluated in the present study. We expressed recombinant proteins E2-IL28B, E2, and IL-28B using CHO-S mammalian cells as an antigen expression platform, and three types of CSFV E2 subunit vaccines based on antigens E2-IL28B, E2 + IL-28B, and E2 were prepared, respectively. We found that both E2-IL28B and E2 + IL-28B antigens exhibited superior immunogenicity with dramatically induced antibody titers and neutralizing antibody levels than the E2 alone. Moreover, E2-IL28B or E2 + IL-28B, instead of E2, boosted cellular immune responses via obviously increasing the percentages of CD3+CD4+ T lymphocytes, promoting the lymphocyte proliferations, and enhancing the release of Th1-type cytokines. All results revealed that the inclusion of IL-28B, whether fused or mixed with E2, significantly elevated E2-induced immune potencies, suggesting that IL-28B could be used as a molecular adjuvant to optimize the design of E2 subunit vaccine for more effective controls of the CSF disease. • New CSF E2 subunit vaccine candidates were developed in which IL-28B was an immunoadjuvant • IL-28B significantly elevated the E2-induced immune potency whether it was fused or mixed with E2 • This study provided novel insights into the immunoregulatory properties of IL-28B used for the optimized subunit vaccine design

Foot-and-mouth disease virus (FMDV) serotype A exhibits extensive genetic and antigenic diversity, complicating vaccine strain selection. Here, we identified two distinct panels of host-derived neutralizing antibodies (nAbs) specific to the SEA97 lineage. The majority of nAbs (10/11) targeted antigenic site 2, while one bovine-derived antibody recognized residue 138 in the VP1 G-H loop. Compared with the ancestral A/AF72 strain of the A22 lineage, the T138A substitution and 140 N deletion on VP1 significantly enhanced the cross-neutralizing activity of SEA97 lineage-specific antibodies against the VP1 G-H loop and antigenic site 2, extending their coverage to the mutated A/AF72 strain. Neutralization assays with porcine immune sera further demonstrated that these mutations are key contributors to antigenic divergence between the A22 and SEA97 lineages. Structural simulations indicated that the T138A substitution and 140 N deletion in VP1 shifted the G-H loop conformation of A/AF72 strain toward that of SEA97 lineages, implicating them as molecular determinants of lineage-specific antigenicity. These findings suggest that substitution or deletion of upstream polar residues of the RGD motif reshaped G-H loop orientation, thereby contributing to antigenic variation in Asia topotype of FMDV serotype A.

Vaccination with inactivated whole-virus vaccines remains the most effective measure for controlling foot-and-mouth disease virus (FMDV) transmission and disease outbreaks. However, the existing type O FMDV vaccines show suboptimal efficacy and antigenic mismatch to the circulating Cathay viruses in China, thus requiring the development of a new vaccine. The VP1 G-H loop is a hypervariable region and plays a pivotal role in the protective immunity induced by FMDV vaccines. Here, we engineered four recombinant FMDVs with insertions of a 20-amino acid (aa) or a 24-aa G-H loop epitope of a prevalent Cathay strain upstream or downstream of the RGD (Arg-Gly-Asp) motif. The recombinant viruses with insertions upstream of the RGD motif retained parental virus-like plaque morphology and replication kinetics and maintained genetic stability even after 20 serial passages. In contrast, the downstream insertion variants exhibited small plaque morphology, reduced growth capacity, and acquired 1 or 2 aa mutations in the capsid proteins by passage 20. The parental virus vaccine induced high titer protective mean neutralizing antibodies (> 1:128) against viruses of the Mya98, PanAsia, and Ind-2001 lineages but failed to elicit protective mean neutralizing antibodies (< 1:22) to the Cathay virus after 28 days vaccination (dpv) in pigs. In contrast, vaccines containing upstream insertions both exhibited protective immune response to viruses of four lineages. Especially, pigs vaccinated with vaccine containing a 24-aa insertion produced significantly higher mean neutralizing antibody against the Cathay virus (p < 0.01), compared to those vaccinated with vaccine having a 20-aa insertion, indicating that the recombinant virus with 24-aa insertion has great potential as a vaccine candidate for serotype O FMD control. This study provides crucial insights for designing FMDV vaccines in the future. • This study firstly reported that FMDV can tolerate a 24-aa insertion in the VP1 G-H loop • The G-H loop insertions at different sites of FMDV VP1 have different impacts on viral replication capacity • Vaccines containing the G-H loop insertions can induce markedly high neutralizing antibodies to the Cathay virus

This study delves into the antiviral efficacy of Formononetin (FMN) and Mizoribine (MZR) against the Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), a virus with a considerable economic impact and a current void in effective treatments. FMN and MZR were found to inhibit various PRRSV strains in vitro, predominantly in the early stages of viral infection. Noteworthy was the observation of their synergistic effects when combined with Ribavirin. The study underscores the antiviral potential of FMN and MZR, particularly emphasizing their low cytotoxicity at specific concentrations. These results position FMN and MZR as promising antiviral agents against PRRSV, underscoring their low cytotoxicity and efficacy in early-stage viral inhibition. Such findings pave the way for their potential inclusion in future PRRSV management strategies.

Porcine reproductive and respiratory syndrome virus (PRRSV) remains one of the major threats to swine industry, resulting in huge economic losses worldwide. Currently, PRRSV has diversified into multiple lineages with characteristics of extensive recombination in China. In this research, three virus strains were isolated and four virus whole genome sequences were generated and analyzed from clinical samples collected in Gansu province of China in 2023. The four virus strains were designated GSTS4-2023, GSLX2-2023, GSFEI2-2023 and GSBY4-2023. Phylogenetic analysis based on ORF5 sequences showed that GSTS4-2023, GSLX2-2023, GSFEI2-2023 and GSBY4-2023 shared 91.7, 91.2, 93.2 and 92.9% homology with NADC30 strain respectively, and belonged to lineage 1 of PRRSV-2. In addition, one amino acid deletion was observed at position 33 in ORF5 of GSTS4-2023, GSLX2-2023 and GSFEI2-2023. Moreover, amino acid alignment of the four strains showed a typical discontinuous 131-amino acid (aa) deletion in NSP2 for NADC30-like virus strains. Recombination analysis revealed that all four strains originated from NADC30 (lineage 1), with their minor parents coming from JXA1-like strains (lineage 8), VR-2332-like strains (lineage5) and QYYZ-like strains (lineage3). Finally, the three isolated virus strains, GSTS4-2023, GSLX2-2023 and GSFEI2-2023 showed relatively low levels of replication in cell culture. Our findings provide important implications for the field epidemiology of PRRSV.

It is a great challenge to isolate the broadly neutralizing antibodies (bnAbs) against foot-and-mouth disease virus (FMDV) due to its existence as seven distinct serotypes without cross-protection. Here, by vaccination of pig with FMDV serotypes O and A whole virus antigens, we obtained 10 bnAbs against serotypes O, A and/or Asia1 by dissecting 216 common clonotypes of two serotypes O and A specific porcine B-cell receptor (BCR) gene repertoires containing total 12720 B cell clones, indicating the induction of cross-serotype bnAbs after sequential vaccination with serotypes O and A antigens. The majority of porcine bnAbs (9/10) were derived from terminally differentiated B cells of different clonal lineages, which convergently targeted the conserved “RGDL” motif on structural protein VP1 of FMDV by mimicking receptor recognition to inhibit viral attachment to cells. Cryo-EM complex structures revealed that the other bnAb pOA-2 specifically targets a novel inter-pentamer antigen structure surrounding the viral three-fold axis, with a highly conserved determinant at residue 68 on VP2. This unique binding pattern enabled cross-serotype neutralization by destabilizing the viral particle. The evolutionary analysis of pOA-2 demonstrated its origin from an intermediate B-cell, emphasizing the crucial role of somatic hypermutations (SHMs) in balancing the breadth and potency of neutralization. However, excessive SHMs may deviate from the trajectory of broad neutralization. This study provides a strategy to uncover bnAbs against highly mutable pathogens and the cross-serotype antigenic structures to explore broadly protective FMDV vaccine.

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) poses a major threat to the global swine industry, yet effective prevention and control measures remain elusive. This study unveils Nitazoxanide (NTZ) as a potent inhibitor of PRRSV both in vitro and in vivo. Through High-Throughput Screening techniques, 16 potential anti-PRRSV compounds are identified from a library comprising FDA-approved and pharmacopeial drugs. We show that NTZ displays strong efficacy in reducing PRRSV proliferation and transmission in a swine model, alleviating viremia and lung damage. Additionally, Tizoxanide (TIZ), the primary metabolite of NTZ, has been identified as a facilitator of NMRAL1 dimerization. This finding potentially sheds light on the underlying mechanism contributing to TIZ's role in augmenting the sensitivity of the IFN-β pathway. These results indicate the promising potential of NTZ as a repurposed therapeutic agent for Porcine Reproductive and Respiratory Syndrome (PRRS). Additionally, they provide valuable insights into the antiviral mechanisms underlying NTZ's effectiveness.

AbstractAs a RIG-I-like receptor, MDA5 plays a critical role in antiviral innate immunity by acting as a cytoplasmic double-stranded RNA sensor capable of initiating type I interferon pathways. Here, we show that RNF144B specifically interacts with MDA5 and promotes K27/K33-linked polyubiquitination of MDA5 at lysine 23 and lysine 43, which promotes autophagic degradation of MDA5 by p62. Rnf144b deficiency greatly promotes IFN production and inhibits EMCV replication in vivo. Importantly, Rnf144b−/− mice has a significantly higher overall survival rate than wild-type mice upon EMCV infection. Collectively, our results identify RNF144B as a negative regulator of innate antiviral response by targeting CARDs of MDA5 and mediating autophagic degradation of MDA5.

Non-structural protein 2 (NSP2) of PRRSV is highly variable and plays crucial roles in the virus’s life cycle. To elucidate the function of NSP2 during PRRSV infection, we identified SH3KBP1 as an NSP2-interacting host protein using mass spectrometry. Exogenous SH3KBP1 expression significantly inhibited PRRSV replication by enhancing IFN-I and related ISGs production. Conversely, SH3KBP1 knockdown promoted viral replication by downregulating IFN-I and ISGs levels. In vivo experiments revealed that Sh3kbp1-/- mice were more susceptible to VSV infection, exhibiting reduced serum IFN-β levels. Further investigation showed that SH3KBP1 enhances RIG-I signal transduction by increasing K63-linked polyubiquitination through interaction with the E3 ubiquitin ligase TRIM25. We also found that PRRSV infection and NSP2 overexpression induce the autophagic degradation of SH3KBP1, counteracting the host’s innate immune response. A critical interaction site was identified within the third polyproline-arginine motif in NSP2 (453PVPAPR458). Recombinant PRRSV lacking this motif displayed reduced virulence and decreased SH3KBP1 degradation. This study advances our understanding of how PRRSV interferes with the host immune response and offers valuable insights for developing novel attenuated vaccines against PRRSV.

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Porcine Reproductive and Respiratory Syndrome (PRRS) presents a formidable viral challenge in swine husbandry. Confronting the constraints of existing veterinary pharmaceuticals and vaccines, this investigation centers on Caffeic Acid Phenethyl Ester (CAPE) as a prospective clinical suppressant for the Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). The study adopts an integrated methodology to evaluate CAPE's antiviral attributes. This encompasses a dual-phase analysis of CAPE's interaction with PRRSV, both in vitro and in vivo, and an examination of its influence on viral replication. Varied dosages of CAPE were subjected to empirical testing in animal models to quantify its efficacy in combating PRRSV infections. The findings reveal a pronounced antiviral potency, notably in prophylactic scenarios. As a predominant component of propolis, CAPE stands out as a promising candidate for clinical suppression, showing exceptional effectiveness in pre-exposure prophylaxis regimes. This highlights the potential of CAPE in spearheading cutting-edge strategies for the management of future PRRSV outbreaks.

Foot-and-mouth disease virus (FMDV) serotype A is antigenically most variable within serotypes. The structures of conserved and variable antigenic sites were not well resolved. Here, a historical A/AF72 strain from A22 lineage and a latest A/GDMM/2013 strain from G2 genotype of Sea97 lineage were respectively used as bait antigen to screen single B cell antibodies from bovine sequentially vaccinated with A/WH/CHA/09 (G1 genotype of Sea97 lineage), A/GDMM/2013 and A/AF72 antigens. Total of 39 strain-specific and 5 broad neutralizing antibodies (bnAbs) were isolated and characterized. Two conserved antigenic sites were revealed by the Cryo-EM structures of FMDV serotype A with two bnAbs W2 and W125. The contact sites with both VH and VL of W125 were closely around icosahedral threefold axis and covered the B-C, E-F, and H-I loops on VP2 and the B-B knob and H-I loop on VP3; while contact sites with only VH of W2 concentrated on B-B knob, B-C and E-F loops on VP3 scattering around the three-fold axis of viral particle. Additional highly conserved epitopes also involved key residues of VP158, VP1147 and both VP272 / VP1147 as determined respectively by bnAb W153, W145 and W151-resistant mutants. Furthermore, the epitopes recognized by 20 strain-specific neutralization antibodies involved the key residues located on VP3 68 for A/AF72 (11/20) and VP3 175 position for A/GDMM/2013 (9/19), respectively, which revealed antigenic variation between different strains of serotype A. Analysis of antibody-driven variations on capsid of two virus strains showed a relatively stable VP2 and more variable VP3 and VP1. This study provided important information on conserve and variable antigen structures to design broad-spectrum molecular vaccine against FMDV serotype A.

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease of cloven-hoofed animals. Vaccination and surveillance against non-structure protein (NSP) are the most efficacious and cost-effective strategy to control this disease. Therefore, vaccine purity control is vital for successful prevention. Currently, vaccine purity is tested by an in-vivo test that recommended in the World Organization for Animal Health (WOAH), but it is time consuming and costly. Herein, we develop a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for quantitative detection of residual NSPs in inactivated FMD virus (FMDV) vaccines. In this assay, the monoclonal antibody 3A24 was selected as capture antibody and biotinylated 3B4B1 (Biotin-3B4B1) as detection antibody. A standard curve was developed using the NSP 3AB concentration versus OD value with the linear range of concentration of 2.5-160 ng/mL. The lowest limit of detection was 2.5 ng/mL. In addition, we determined 2.5 ng/mL of NSP as an acceptable threshold value of FMD vaccine purity using a dose-response experiment in cattle. The DAS-ELISA combined with the threshold value of FMD vaccine purity could provide a quick and simple tool for evaluation the antigenic purity of FMD vaccine during the manufacturing process.

为了鉴定湖北省某猪场水疱性疾病的病原,本研究采用RT-P C R、细胞分离培养、间接免疫荧光检测、电镜观察、病毒基因序列测定及分子进化分析的方法对湖北省某猪场采集的具有水疱样病变的猪水疱皮样品进行了病毒的分离和鉴定及全基因组序列的测定.结果表明:成功分离到1株A型塞内卡病毒(SVA),命名为HBWH/1/2018株.该毒株接种BHK-21细胞培养能够引起明显的致细胞病变效应;免疫荧光试验结果为阳性;病毒滴度为109.35 TCID50/0.1mL;该毒株基因组全长7281 bp(不包括Poly A),开放阅读框为6546 bp,编码2181个氨基酸;VP1核苷酸序列的遗传进化分析表明HBWH/1/2018株与HN01/2017株亲缘关系最近(相似性高达99.4％),而与SVA原型毒株SVV-001株的亲缘关系最远(相似性为91.3％).本研究不仅丰富了SVA的分子流行病学数据,也为进一步研究SVA的致病机理及相关疫苗的研发奠定了基础.

Senecavirus A (SVA) is an emerging viral pathogen related to vesicular disease and neonatal mortality in swine, which results in enormous economic losses to the global swine industry. The clinical signs of SVA are indistinguishable from those of other vesicular diseases, such as foot-and-mouth disease, which is an economically devastating animal disease. Therefore, development of a rapid, sensitive, and specific diagnostic method for the detection of SVA infection is critical for the prevention and control of SVA and would help to rule out other exotic diseases. In this study, two whole-porcine anti-SVA antibodies (1M5 and 1M25) were produced using single B cell antibody technology. 1M5 and 1M25 possessed neutralizing activity against SVA but recognized different conformational epitopes that depended on the intact virion. Using 1M5 as the capture antibody and biotinylated 1M25 as the detection antibody, a reliable and rapid competitive enzyme-linked immunosorbent assay for detecting neutralizing antibodies (NAC-ELISA) against SVA was developed. Receiver-operating characteristic curve analysis showed that the sensitivity and specificity of the assay were 98.11% and 100%, respectively, with a cutoff percent inhibition value of 45%. The NAC-ELISA was specific for detecting SVA-specific antibodies, without cross-reactivity to other virus-infected sera. The results of the NAC-ELISA showed a strong agreement with the results of the virus neutralization test. Therefore, the NAC-ELISA developed in this study represents a sensitive, specific, and reliable tool for the detection of SVA-specific antibodies, which is applicable for serodiagnosis and serological surveillance of SVA and is conducive to the prevention and control of SVA.IMPORTANCE Senecavirus A (SVA) is an emerging picornavirus related to vesicular disease and neonatal mortality in swine, which results in enormous economic losses worldwide. Additionally, the clinical characteristics of the disease are indistinguishable from those of other vesicular diseases, such as foot-and-mouth disease. Therefore, developing tools for rapidly and accurately detecting SVA infection is critical and urgent. In this study, two porcine-derived monoclonal antibodies against SVA were generated, and a competitive ELISA for the detection of neutralizing antibodies (NAC-ELISA) against SVA was successfully developed using these two porcine monoclonal antibodies. The NAC-ELISA was SVA specific with no cross-reactivity to other related pathogens and had high sensitivity, specificity, and reproducibility for detecting SVA-specific antibody. Therefore, the NAC-ELISA developed in this study may be of great value as a simple and reliable tool for serodiagnosis or surveillance of SVA and may facilitate the prevention and control of SVA.

MicroRNAs are small non-coding RNA that regulate host anti-viral immune response. In this study, we used high-throughput sequencing to identify miRNAs that were differentially expressed upon PRRSV infection in porcine alveolar macrophages. We observed that the expression level of miR-122 was decreased upon PRRSV infection. Over-expression of miR-122 remarkably suppressed PRRSV replication, while blockage of endogenous miR-122 enhanced PRRSV replication. Moreover, over-expression of miR-122 reduced the protein level of porcine suppressor of cytokine signaling 3 (SOCS3), a negative regulator of JAK-STAT signaling, resulting in enhanced production of type Ⅰ IFN. Further analysis revealed that miR-122 decreased the expression of SOCS3 at the post-transcription level by targeting the 3' UTR region of SOCS3 mRNA. In conclusion, this study demonstrates that the expression of miR-122 was reduced during PRRSV infection. miR-122 impaired PRRSV replication by promoting the production of type I interferon. Our study may provide new insights into understanding PRRSV immune evasion mechanisms.

[目的]为评价O型口蹄疫病毒(foot-and-mouth disease virus,FMDV)灭活疫苗免疫后中和抗体(neutralizing antibodies,NA)水平,建立检测中和抗体的固相阻断ELISA(neutralizing antibodies solid-phase blocking ELISA,NA-SPBE)方法.[方法]本研究以本实验室前期制备的FMDV广谱反应性牛源单克隆抗体E32作为捕获抗体,以生物素标记的FMDV O型型内广谱中和牛源单克隆抗体C4作为检测抗体,经过条件优化建立了检测FMDV O型中和抗体的固相阻断ELISA方法,并对该方法进行了敏感性、特异性、重复性、交叉反应性与病毒中和试验(virus neutralization test,VNT)相关性等试验.[结果]抗体E32最佳包被浓度为0.5 μg/mL,O型FMDV灭活抗原最佳稀释浓度为0.25μg/mL,生物素标记抗体C4-Bio最佳工作浓度为0.06 μg/mL,链霉亲和素-HRP的最佳稀释度为1∶40 000.以1.35 log10作为效价判定临界值时,敏感性和特异性分别为97.14％和98.84％.利用该方法分别检测FMDV A型、FMDV Asial型、BVDV、PRRSV、CSFV、PPRV抗体阳性血清时,均为阴性,未出现交叉反应.该方法批内和批间重复试验的变异系数均＜10％,表明其重复性较好.利用该方法与VNT分别对160份血清样品进行检测,二者的相关系数r为0.807 5,P＜0.000 1,相关性显著.[结论]该方法可以检测FMDV O型中和抗体,为FMDVO型灭活疫苗免疫效果评价提供有力技术支撑.