In vitro inhibition of rubella virus by 1-adamantanamine hydrochloride

Summary The effect of 1-adamantanamine hydrochloride (1-AH) on the multiplication of three strains of rubella virus in RK-13 tissue cultures was studied. At a concentration of 25g/ml. the compound depressed the yield of infective virus, reduced the cytopathic end-point titres and inhibited the formation of rubella virus microplaques. The inhibition of microplaques was the most sensitive method of detecting the antiviral activity of 1-AH and concentrations as low as 10g/ml. were effective. Whilst 25g/ml. of 1-AH did not produce obvious toxic effects, 40g/ml. caused cytoplasmic vacuolation and decreased the rate of cell divison of RK-13 cultures.Inhibition of rubella virus CPE by 1-AH was more marked in virus strains poorly adapted to growth in RK-13 cultures.Studies on the mode of action of 1-AH indicate the absence of direct virucidal action and the compound neither decreased the rate of adsorption of virus to RK-13 cells nor inhibited release of intracellular virus from infected cells. The compound appeared to act at an early stage in the growth cycle and was not effective in inhibiting subsequent virus multiplication if added later than 5 hours after infecting tissue cultures with rubella virus.