Differentiation of Foot-and-Mouth Disease Virus-Infected from Vaccinated Pigs by Enzyme-Linked Immunosorbent Assay Using Nonstructural Protein 3AB as the Antigen and Application to an Eradication Program

Abstract

Baculovirus-expressed foot-and-mouth disease virus (FMDV) nonstructural protein 3AB was used as the antigen in an enzyme-linked immunosorbent assay. This assay allowed the differentiation of vaccinated from infected pigs. Serial studies were performed using sera collected from pigs in the field. Positive reactions were found in sera from fattening pigs and sows 16 weeks and 3.5 years postoutbreak, respectively. There was, however, no positive reaction in sows with at least 10 vaccinations. Maternally derived antibodies to the 3AB antigen persisted in piglets up to 13 weeks of age. A high correlation coefficient (r ‫؍‬ 0.93) was found between the test results from sow sera and those from their offspring. Therefore, piglet serum was a good substitute for sow serum to monitor the infection status of the dam. The application of this assay to serological surveillance in an FMD eradication program in Taiwan showed that the positive reactors steadily decreased over time in both finishers and sows, indicating that the pig population risk of infection by FMDV has decreased.

Differentiation of Foot-and-Mouth Disease-Infected Pigs from Vaccinated Pigs Using Antibody-Detecting Sandwich ELISA

“…In countries and areas where FMD vaccination is implemented, the serological differential diagnosis of FMD can be difficult because vaccinated animals cannot be distinguished from infected animals simply by the VNT, since neutralizing antibodies are elicited by vaccination, natural infection or both. Several countries that vaccinate against FMD now use antibodies against NSP of FMDV as replaced serological markers for identifying FMDV-infected animals [9,26]. Developing novel serological methods or improving the currently available ones, especially ELISA, is a crucial step toward the eradication of FMD [1,13,25,35].…”

“…During the last decade, the use of immunoenzymatic tests based on the detection of antibodies to NSPs to assess viral circulation in susceptible populations has been extensively studied and has allowed for a "vaccination to live" policy, and this approach can be supported by testing vaccinated animals for the presence of antibodies to certain NSPs of FMDV, which are induced by infection with the virus, but not by vaccination with purified FMD vaccines [5,29]. Many assay technologies, such as the latex bead agglutination test [37], enzyme-linked immunoelectrotransfer blotting [4], enzyme-linked immunosorbent assay [1,5,9,11,13,19,23,25,[34][35][36], multiplexed Luminex assay [12] and chromatographic strip assay [8] have been employed, and several NSPs have been expressed or synthesized artificially for these assays.…”

Development of a Chromatographic Strip Assay for Detection of Porcine Antibodies to 3ABC Non-Structural Protein of Foot-and-Mouth Disease Virus Serotype O

“…During the last decade, the use of immuno-enzymatic tests to detect anti-NSP antibodies and thus to assess virus circulation in susceptible populations has been studied extensively. Methods such as the latex beads agglutination test [26], enzyme-linked immunoelectrotransfer blot assay [2], enzyme-linked immunosorbent assay [2,3,5,8,9,10,12,16,17,19,[23][24][25] and multiplexed Luminex assay [9] have been employed for this purpose. These assays all need to be performed in the laboratory with different instrument and technical requirements, which restricts the use of these methods in the field and hence prolongs the time between diagnosis and response to this rapidly transmitted disease.…”

Development and Evaluation of an Indirect Enzyme-Linked Immunosorbent Assay for Detection of Foot-and-Mouth Disease Virus Nonstructural Protein Antibody using a Chemically Synthesized 2B Peptide as Antigen

“…Antibody to 2B was detectable from the end of the first week to the second week after infection in most of the nonvaccinated animals and by the second to third week in vaccinated-and-challenged animals. The sensitivity of the 2B peptide ELISA was comparable to the 3ABC Ceditest (CeditestH FMDV-NS, Cedi Diagnostics B.V.; Chung et al, 2002). With some modification and further validation, this 2B test could be useful as a screening or conformational NSP test in postvaccination surveillance for FMD.…”