AUTHOR=Xiao Ning , Li Jiannan , Li Minxue , Hu Yuting , Lin Huixing , Fan Hongjie 

TITLE=Preparation and Characterization of a New Monoclonal Antibody Specific Against Lawsonia intracellularis and Its Application in Indirect Immunofluorescence and Immunocytochemistry Assay

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.753610

DOI=10.3389/fvets.2021.753610

ISSN=2297-1769

ABSTRACT=<p>Proliferative enteropathy (PE) is an infectious enteric disease caused by <italic>Lawsonia intracellularis</italic> (<italic>L. intracellularis</italic>) and is endemic in pig herds worldwide. However, a <italic>L. intracellularis</italic>-specific monoclonal antibody plays an important role in the evaluation of <italic>L. intracellularis</italic> infection <italic>in vitro</italic>. Therefore, the objective of this study was to produce and identify the characteristics of a new monoclonal antibody against the outer membrane protein (Omp2) of <italic>L. intracellularis</italic> and apply it in an indirect immunofluorescence assay (IFA) and immunocytochemistry (IHC). The results indicated that three highly specific monoclonal antibodies against the Omp2 protein (4D9, 3G2, and 7G5) of <italic>L. intracellularis</italic> were obtained by using purified Omp2 as an immunogen, the titers of ascitic fluids of 4D9, 3G2, and 7G5 cells were 1:2,048,000, 1:512,000, and 1:256,000, respectively. IFA analysis showed that the 4D9, 3G2, and 7G5 have no cross-reactivity with other enteric bacteria commonly found in the ilea of pigs or closely related to <italic>L. intracellularis</italic>, such as <italic>Desulfovibrio, Bilophila wadsworthia</italic> (<italic>B. wadsworthia</italic>), <italic>Salmonella choleraesuis</italic> (<italic>S. choleraesuis</italic>), <italic>Salmonella typhimurium</italic> (<italic>S. typhimurium</italic>), <italic>Escherichia coli</italic> (<italic>E. coli</italic>), and <italic>Brachyspira hyodysenteriae</italic> (<italic>B. hyodysenteriae</italic>). IFA and IHC results indicated that the monoclonal antibodies can be successfully used as primary antibodies to detect <italic>L. intracellularis</italic> in infected cells and in the crypt of the ileum from infected tissues of PE. Our findings suggested that the new monoclonal antibody specific against <italic>L. intracellularis</italic> will be useful for the evaluation of <italic>L. intracellularis</italic> infection <italic>in vivo</italic> and <italic>in vitro</italic>.</p>