ANTIVIRAL ACTIVITY OF AN EXTRACT FROM LEAVES OF THE TROPICAL PLANT ACANTHOSPERMUM-HISPIDUM

Incubation of the alphaherpesviruses pseudorabiesvirus (PRV) and bovin e herpesvirus 1 during infection of cell cultures with an extract prep ared from the leaves of Acanthospermum hispidum impaired productive re plication of these viruses in a concentration-dependent manner whereas propagation of classical swine fever virus, foot-and-mouth disease vi rus and vaccinia virus was not affected. The 50% inhibitory concentrat ion for cell growth (IC50) was 107 +/- 5 mu l/ml, and the concentratio n reducing PRV yield by 1 log(10) (90% effective concentration, EC90) was 8 +/- 3 mu l/ml. The selectivity index calculated as the IC50/EC90 ration was 13 +/- 4. Delineation of the mechanism of the antiviral ac tivity demonstrated inhibition of alphaherpesvirus attachment to and, to a lesser extent, penetration into the cells. In contrast, viral gen e expression was not inhibited by the extract when added after entry o f virions into the target cells. Reduced antiviral activity of A.h. ag ainst PRV deletion mutants lacking glycoprotein C (gC) or glycoprotein s gC, gE, gG and gI altogether indicated that gC alone and/or viral at tachment complexes of which gC is a component constitute the target st ructures for A. hispidtum. (C) 1997 Elsevier Science B.V.