A mutant of chikungunya virus isolated from a line of Singh's Aedes albopictus cells by plaque formation on virus-sensitive cloned cells obtained from another Singh's A. albopictus cell line

Abstract

A chikungunya (CHIK) virus-resistant line of Singh's Aedes albopictus (SAAK) cells released spontaneously two kinds of plaque-forming agents which could be distinguished by the plaque size on a sensitive clone C6/36 of another A. albopictus cell line (SAAR). Release of the large plaque (Lp) and the small plaque (sp) viruses into the culture medium occurred at different rates when the SAAK cells were subcultured. The Lp virus was removed from the SAAK cells by subculturing or cloning in the presence of anti-CHIK serum. Such Lp(-) cells continued to produce the sp virus, but were permissive for CHIK virus. The plaque-purified Lp virus, but not sp virus, interfered with the growth of CHIK virus in the C6/36 cells. The Lp virus resembled in physicochemical and serological properties CHIK virus grown in C6/36 cells. However the Lp virus was not pathogenic for suckling mice, was heat labile, and showed higher plating efficiency on the C6/36 cells than on BHK21 cells. The data indicate that the Lp virus is a mutant of CHIK virus and is responsible for the CHIK virus resistance of the SAAK cells.