Characteristics of polyarthritis in rabbits by hyperimmunization with attenuated Enterococcus faecalis

To produce polyarthritis and rheumatoid factor like substance (RFLS), rabbits were hyperimmunized intravenously with 0.02% thimelosal (TMS)-treated Enterococcus faecalis (E. faecalis) as a persistent bacterial flora. Swelling of knee joints occurred at a rate of 41% (27/66), and of shoulder joints at a rate of 25% (17/66) while that of elbow joints occurred at a rate of 4.5% (3/66). On culturing of knee joint fluids, no colonies appeared while 2/4 fluid specimens from the shoulder joints gave positive colonies for 78 days after the first immunization; thereafter, no colonies appeared. On histological examination, in early stages, acute inflammatory reactions with degenerative changes of synovial tissue was observed. In later stages, chronic inflammatory changes, proliferation of synovial cells with pannus formation, destruction of articular cartilage and subchondral bone were observed. RFLS titer showed bi-phasic peaks at 11 days and 41 days after the first immunization. A high incidence of polyarthritis, particularly knee joints, occurred. Thus, hyperimmunization with attenuated E. faecalis as a normal intestinal flora may provide an animal model of chronic polyarthritis.