Sellwood R, Walton F, Thomas W, Burrows M R, Chesham J
A.F.R.C. Institute for Animal Health Compton Newbury, Berks, UK.
Vet Microbiol. 1995 Apr;44(1):25-35. doi: 10.1016/0378-1135(94)00108-9.
An ELISA has been developed using a monoclonal antibody (F325 AC4) to the SmpA surface lipoprotein of Serpulina hyodysenteriae strain P18A when grown in vitro. The lower level of detection of the ELISA was approximately 5 x 10(6) spirochaetes/ml when spirochaetes were either resuspended in phosphate buffered saline or in pig faeces. When pigs were challenged with S. hyodysenteriae strain P18A the lipoprotein was detected in the faeces of pigs by ELISA when the numbers of spirochaetes excreted was greater than 10(6) per g of faeces. After onset of clinical signs in the pig, expression of SmpA was not detected by ELISA or by Western blotting using either monoclonal antibody F325 AC4 or polyclonal antiserum B50 against the SmpA antigen. However, when the in vivo grown spirochaetes were subsequently cultured in vitro expression of SmpA was detected by Western blotting. In the mouse model of swine dysentery S. hyodysenteriae spirochaetes obtained from mice with gross lesions also did not express SmpA. It was concluded that the apparent lack of expression may have been the result of environmental regulation of gene expression or antigenic variation and was not due to denaturation of the antigen in vivo.
