The hemagglutination-positive phenotype of Mycoplasma synoviae induces experimental infectious synovitis in chickens more frequently than does the hemagglutination-negative phenotype

Inoculation with hemagglutination-positive (HA(+)) cultures of Mycoplasma s ynoviae AAY-4 induced acute synovitis significantly more frequently (P = 0. 001) in chicken tibiotarsal-tarsometatarsal joints than did inoculation wit h RA-negative (HA(-)) cultures derived from the same clone of AAY-4 Immunob lotting analyses showed that HA(+) cultures abundantly expressed two phase- variable hemadherence-associated surface membrane proteins of 53 kDa and 48 to 50 kDa defined by monoclonal antibodies. HA(-) cultures lacked the 53-k Da proteins and synthesized truncated 27- to 30-kDa forms of the 48- to 50- kDa proteins. Inoculation of cyclosporin A (CsA) into infected joints signi ficantly decreased the frequency of acute synovitis (P = 0.001). Moreover, repeated intra-articular inoculation of CsA (three doses of 1 mg at 2-day i ntervals) significantly reduced the local antibody response to M. synoviae in the joints treated with CsA.