ANTIBODY-DEPENDENT ENHANCEMENT AND PERSISTENCE IN MACROPHAGES OF AN ARBOVIRUS ASSOCIATED WITH ARTHRITIS

Ross River virus (RRV) is the aetiological agent of epidemic polyarthr itis (EPA) a predominantly rheumatic disease afflicting up to 5000 Aus tralians annually. We show here for the first time that macrophages ca n be productively infected by RRV. Subneutralizing titres of anti-RRV IgG (but not IgM) also showed classical antibody-dependent enhancement (ADE) of RRV infection in macrophage and monocyte cell lines. No corr elation between development of EPA and the preexistence of AIDE titres was apparent, nor could sera raised against a related arbovirus, Barm ah Forest, enhance RRV infection. Tumour necrosis factor-alpha, implic ated in the immunopathogenesis of rheumatoid arthritis, was not secret ed by RRV-infected monocytes or macrophages. Macrophage cell lines inf ected with RRV were, however, capable of producing virus for over 50 d ays. RRV-induced arthritis may therefore be due to the persistent prod uctive infection of macrophages, perhaps established by a brief period of ADE early in infection.