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Clinical and Diagnostic Laboratory Immunology, January 2005, p. 180-186, Vol. 12, No. 1
1071-412X/05/$08.00+0     doi:10.1128/CDLI.12.1.180-186.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Antibody Responses of Pigs to Defined E^rns Fragments after Infection with Classical Swine Fever Virus

Min Lin,^1* Erin Trottier,¹ and John Pasick²

Animal Diseases Research Institute, Ottawa, Ontario,¹ National Centre for Foreign Animal Disease, Winnipeg, Manitoba, Canada²

Received 26 July 2004/ Returned for modification 8 September 2004/ Accepted 24 September 2004

Antibody responses of pigs to defined E^rns fragments, after classical swine fever virus (CSFV) infection, were studied by using an enzyme-linked immunosorbent assay (ELISA). Selection of various E^rns fragments was based on an immunodominant E^rns region encompassing three overlapping antigenic regions, amino acids 65 to 145 (E^rns_{aa 65-145}) (AR1), 84 to 160 (E^rns_{aa 84-160}) (AR2), and 109 to 220 (E^rns_{aa 109-220}) (AR3), identified earlier by our group (M. Lin, E. Trottier, J. Pasick, and M. Sabara, J. Biochem., in press). Defined E^rns fragments, including AR1, AR2, AR3, E^rns_{aa 65-160} (AR12), E^rns_{aa 84-220} (AR23), E^rns_{aa 65-220} (AR123), E^rns_{aa 109-145} (the consensus region defined by the three overlapping regions), and E^rns_{aa 109-160} (a fragment 15 amino acids larger than the consensus region), were expressed in Escherichia coli, purified by nickel chelate affinity chromatography, and used to measure antibody responses in 20 sera serially collected from pigs experimentally infected with CSFV. Based on the optimum cutoffs determined by receiver operating characteristic analysis after testing 238 negative field sera from Canadian sources, all the E^rns fragments were capable of distinguishing positive from negative antibody responses with sensitivities ranging between 75 and 90% and specificities ranging between 83.2 and 100%. Detection of antibody responses to refolded E^rns_{aa 109-145} and E^rns_{aa 109-160} by ELISA (this study) but not by Western blots (Lin et al., in press) indicated that the epitopes within the consensus region are conformational. When cutoff values were raised to give a specificity of 100%, four E^rns fragments (AR2, AR23, E^rns_{aa 109-145}, and E^rns_{aa 109-160}) offered much higher sensitivities (75 to 90%) than those obtained with other fragments (20 to 65%). E^rns_{aa 109-145} and E^rns_{aa 109-160} were capable of detecting antibody responses in infected pigs as early as 7 days postinfection. Demonstration of antibody responses to either one of the four fragments can thus be an alternative to use of the full-length protein in ELISA for serological diagnosis of CSFV infection. An advantage of such a test would be its utilization for serological survey in a classical swine fever-free country (e.g., Canada) in biocontainment level 2 laboratories.

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* Corresponding author. Mailing address: Canadian Food Inspection Agency, Animal Diseases Research Institute, 3851 Fallowfield Rd., Ottawa, Ontario, Canada K2H 8P9. Phone: (613) 228-6698. Fax: (613) 228-6667. E-mail: linm{at}inspection.gc.ca.

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Clinical and Diagnostic Laboratory Immunology, January 2005, p. 180-186, Vol. 12, No. 1
1071-412X/05/$08.00+0     doi:10.1128/CDLI.12.1.180-186.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Lin, M., Trottier, E., Mallory, M. (2005). Enzyme-Linked Immunosorbent Assay Based on a Chimeric Antigen Bearing Antigenic Regions of Structural Proteins Erns and E2 for Serodiagnosis of Classical Swine Fever Virus Infection. CVI 12: 877-881 [Abstract] [Full Text]