The generation of defective interfering rubella virus particles

Rubella virus (RV) particles produced under varying degrees of autointerference have been studied. RV has been purified from these stocks and studied by isopycnic centrifugation. RNA was extracted from the purified virions, labeled with ¹²⁵I, electrophoresed on 5% polyacrylamide slab gels, and subjected to autoradiography. The viral particles varied considerably with respect to their density and their RNA content. Virions present in low-interference stocks were contained in one band at ? = 1.19 g/ml³. Two single-stranded RNA species could be extracted from this band with molecular weights of 2.95 and 2.80 × 10⁶. Virions present in high-interference stocks were contained in at least three bands with densities of 1.19, 1.17, and 1.15 g/ml³. The molecular weights of the RNA molecules extracted from these three bands were 2.95, 2.80, 1.25, and 1.05 × 10⁶. Therefore, defective RV particles have been detected which possessed a density less than 1.19 g/ml³, contained a smaller RNA, and elicited autointerference.