Abstract
Proliferative enteropathy (PE) is an infectious enteric disease caused by Lawsonia intracellularis (L. intracellularis) and is endemic in pig herds worldwide. However, a L. intracellularis-specific monoclonal antibody plays an important role in the evaluation of L. intracellularis infection in vitro. 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 L. intracellularis 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 L. intracellularis 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 L. intracellularis, such as Desulfovibrio, Bilophila wadsworthia (B. wadsworthia), Salmonella choleraesuis (S. choleraesuis), Salmonella typhimurium (S. typhimurium), Escherichia coli (E. coli), and Brachyspira hyodysenteriae (B. hyodysenteriae). IFA and IHC results indicated that the monoclonal antibodies can be successfully used as primary antibodies to detect L. intracellularis 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 L. intracellularis will be useful for the evaluation of L. intracellularis infection in vivo and in vitro.
Highlights
Proliferative enteropathy (PE) is an infectious enteric disease characterized by thickening of the ileal wall as a result of enterocyte proliferation associated with the presence of Lawsonia intracellularis [1, 2]
Our findings indicated that the L. intracellularis in the monolayer of eukaryotic cells could be detected at 3 h post infection (Figure 6A), and highly infected cells (HIC) may be observed once the bacteria are cultivated for up to 7 days post incubation
Monoclonal antibody plays an important role in the isolation and culture of L. intracellularis
Summary
Proliferative enteropathy (PE) is an infectious enteric disease characterized by thickening of the ileal wall as a result of enterocyte proliferation associated with the presence of Lawsonia intracellularis [1, 2]. Preparation of Antibody Against Lawsonia intracellularis intestinal adenomatosis (PIA) is considered to be the chronic form of PE, which leads to mild diarrhea and reduced growth in young pigs aged 8–20 weeks [7, 8]. Proliferative hemorrhagic enteropathy (PHE), an acute form of PE, often occurs in older finisher pigs, gilts, and sows, is characterized by bloody diarrhea, and often leads to sudden death [7, 8]. L. intracellularis has been widely spread in more than 20 countries, such as China, Canada, Brazil, Finland, France, South Africa, Greece, and India [9, 10], and the disease causes more than $1.63 per infected pig due to bloody diarrhea, sudden death, decreased body weight, stunted growth, and increased costs of feeding and medication worldwide [11,12,13]. To control the infection and spread of PPE effectively, it is crucial to obtain the L. intracellularis strain isolated from China and prepare an effective PPE vaccine, while the prerequisite for successful isolation of L. intracellular is to prepare the specific monoclonal antibody to monitor the bacteria in tissue sample and infected cell monolayer
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