One method is an indirect ELISA based on recombinant NSPs, peptides or epitopes [1, 8, 10C15]

One method is an indirect ELISA based on recombinant NSPs, peptides or epitopes [1, 8, 10C15]. of contamination, certifying animals for trade and controlling the disease. Methods In this study, a competitive chemiluminescence immunoassay (3B-cCLIA) was developed for the rapid detection of antibodies against NSPs in different species of livestock animals using the monoclonal antibody (mAb) 9E2 as a competitive antibody that recognizes NSP 3B. Results The cut-off value (50%), diagnostic sensitivity (Dsn) (97.20%, 95.71%, and 96.15%) and diagnostic specificity (Dsp) (99.51%, 99.43%, and 98.36) of the assay were estimated by testing a panel of known-background sera from swine, cattle and sheep, respectively. The accuracy rate of the 3B-cCLIA was further validated and subsequently compared with that of two commercial diagnostic kits. The early diagnostic results showed that antibodies recognizing NSPs developed later (approximately 1C2?days) than antibodies recognizing structural proteins. Furthermore, anti-NSP antibody presence in animals vaccinated multiple times (false positives), especially cattle and sheep, was confirmed, and the false-positive rate increased with the number of vaccinations. Conclusions These results indicate that this 3B-cCLIA is suitable for the rapid detection of antibodies against FMDV NSP 3B in a wide range of species. Supplementary Information The online version contains supplementary material available at 10.1186/s12985-021-01663-4. Keywords: Chemiluminescence immunoassay, Diagnosis, Foot-and-mouth disease virus, Monoclonal antibody, Non-structural protein Background Foot-and-mouth disease (FMD) is usually a highly contagious and FRAX597 economically FRAX597 damaging viral disease that affects cloven-hoofed animals. FMD virus (FMDV) has positive-sense, single-stranded RNA genome that encodes four structural proteins (SPs: VP4, VP2, VP3 and VP1) and ten non-structural proteins (NSPs: L, 2A, 2B, 2C, 3A, 3B, 3C, 3D, 3AB and 3ABC) [1C3]. FMDV exists in the form of seven serotypes (A, O, C, Asia 1, SAT 1, SAT 2, and SAT 3); serotypes O and A are currently prevalent in China [4, 5]. To date, slaughtering infected and contacted animals and prohibiting the importation of animals and animal products from FMD-endemic countries are practised to prevent the disease in FMD-free nations. Considering the economic costs, vaccination policies have been adopted for the control and eradication of the disease in endemic countries FRAX597 [6, 7]. However, vaccination with inactivated vaccines creates other issues, such as the differentiation between FMDV-infected and vaccinated animals (DIVA) and the creation of carrier animals that shed the virus [6, 7]. Therefore, the detection of antibodies against NSPs has become a widely preferred and applied diagnostic method for DIVA that is helpful in identifying subclinical infections, evaluating the prevalence of contamination and controlling the disease [8] because a series of purifying techniques remove the majority of NSPs from the inactivated vaccine during production [3, 9]. There are two main diagnostic methods S1PR5 for the detection of antibodies against NSPs. One method is an indirect ELISA based on recombinant NSPs, peptides or epitopes [1, 8, 10C15]. Species-specific conjugates are needed for indirect ELISAs, which makes simultaneous examination of sera from different species difficult [16]. Another method is a blocking or competitive ELISA using polyclonal antibodies or monoclonal antibodies (mAbs) [6, 9, 16C20]. In contrast to indirect ELISAs, blocking or competitive ELISAs can be used to detect antibodies in each species that is susceptible to FMD. Most commercial ELISAs are blocking ELISAs, such as the 3ABC monoclonal antibody blocking ELISA (3ABC-bELISA, LVRI, China) and PrioCHECK FMDV NSP ELISA. In a previous study, the mAb 9E2 recognizing NSP 3B that can be used to develop a diagnostic method was preliminarily verified. However, the mAb 2G5 recognizing NSP 3A alone is not suitable for.