Antigenic diversity of ruminant Chlamydia psittaci strains demonstrated by the indirect microimmunofluorescence test with monoclonal antibodies.

Monoclonal antibodies (mAbs) were produced to find strain markers essential to the epidemiological study of chlamydial abortion of ruminants. Their specificity was tested on 53 C. psittaci strains including 35 ruminant strains isolated mainly from abortion, belonging to serotype 1 and which are invasive in our mouse model (Rodolakis et al., 1989), and 14 ruminant strains mostly intestinal, belonging to serotype 2 and non-invasive for mouse. One strain specific mAb was obtained reacting only with the non-invasive strain iB1. Six sub serotype 2 mAbs were found. They reacted only with some non-invasive strains. They allowed the distinction of 9 patterns of response among the 14 non-invasive strains. No serotype 2 specific mAbs reacting with all non-invasive serotype 2 strains were selected. In return all the invasive strains reacted with all the 18 serotype 1 specific mAbs produced. No cross-reactivities between invasive and non-invasive strains were observed, whereas common epitopes were demonstrated between invasive strains and avian or feline strains.