Ross River virus infection of human synovial cells in vitro

Ross River virus (RRV) strains T48 and SC18006 produced a self-limited cytopathic infection of primary and passaged human synovial cell culture. Extracellular (EC) virus titres reached peak levels at 2 days in cell lines and at 4 days in primary cultures, ranging between 10(4.5) and 10(6.6) fluorescent focus-forming units (ffu)/ml. Thereafter titres declined rapidly to undetectable levels at 10-12 days. The proportion of adherent cells showing virus antigen exceeded 60% at 3 days and decreased in all cultures to less than 1/500 after 12 days. Cytopathic effects (CPE) were greatest at 4-8 days and destroyed between 25 and 75% of the cell layer, with subsequent partial regeneration by division of surviving cells. In contrast to rubella virus infection of synovial cells, cultures at 32 degrees and 37 degrees revealed only minor differences and persistent infection was not established. CPE were more extensive at 37 degrees in nearly all synovial cell cultures and in Vero cultures. At 37 degrees synovial cells infected with T48 strain produced higher maximum titres and were more extensively infected than at 32 degrees.