Epitope diversity of F strain Mycoplasma gallisepticum detected by flow cytometry
1997
Brown, J.E. | Branton, S.L. | May, J.D.
A culture of F strain Mycoplasma gallisepticum (F-MG) that exhibited an epitope identified by monoclonal antibody (MAb) 6F10 was used to inoculate leghorn hens in two different trials. In Trial 1, mature hens chronically infected with F-MG were swabbed at intervals from 230 to 345 days postinoculation (PI). The F-MG isolates were tested with an agar plate fluorescent antibody (APFA) method that used a polyclonal antibody and with a flow cytometry (FC) technique that used MAb 6F10. Primary cultures of swabs taken at 258, 272, 293, 318, and 345 days PI were all identified as positive by APFA, whereas FC identified 23%-41% as positive. Subsequently, MAb 6B11 was found, which reacted positively with isolates negative to MAb 6F10. Both 6F10 and 6B11 were used in the second trial, which was designed to identify F-MG isolates that were negative to 6F10. In Trial 2, naive birds were inoculated with F-MG when they were 9 wk old and were sampled at six intervals from 13 to 154 days PI. The APFA method was used to identify primary isolation (P0) cultures, and FC was performed on P0 cultures and the same cultures after they had been passed three times (third serial passage [P3] cultures). The APFA test identified 100% of the P0 cultures as F-MG. The FC results on P0 cultures showed 34.5% as 6F10 positive and 85.1% as 6B11 positive. Results for FC on P3 cultures showed 92.3% 6F10 positive and 96.3% 6B11 positive. These results suggest that the microenvironment of the colonization site in the hen induced an epitope diversity in F-MG, as evidenced by the loss in the expression of MAb 6F10-defined epitope. Isolation of the organism from hens and propagation for several in vitro passages resulted in the re-expression of the epitope defined by MAb 6F10.
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