IN-VIVO INHIBITION OF HEPATITIS-B VIRAL GENE-EXPRESSION BY ANTISENSE PHOSPHOROTHIOATE OLIGODEOXYNUCLEOTIDES IN ATHYMIC NUDE-MICE

Antisense oligodeoxynucleotides strategies have been used both to stud y normal gene function and to block gene expression therapeutically. W e have previously shown that a number of antisense oligonucleotides ag ainst hepatitis B virus (HBV) mRNA are able to inhibit viral gene expr ession in vitro, Here we report the establishment of an animal model p roducing HBV markers in athymic nude mice and inhibition of HBV gene e xpression and replication by antisense DNA in vivo. 2.2.15 cells (Hep- G2 cell line transfected with HBV genomes) were injected subcutaneousl y (s.c.) into athymic BALB/c nude mice at a total cell number of 0.5-1 x10(8) per mouse. Transplanted tumours developed about 2 weeks after i noculation. Hepatitis B surface and e antigens (HBsAg and HBeAg), as w ell as HBV DNA, could be detected in the circulation of tumour-bearing mice, Hepatitis B surface antigen and hepatitis B core antigen (HBcAg ) were demonstrated in tumour cells, After 10 days of tumour growth, a ntisense phosphorothioate oligonucleotide, complementary to the cap si te of the SP II promoter of HBV mRNA, were injected by infiltration in to or around the tumour as a daily dose of 20 mu g per gram body weigh t. Treatment for a total of 10 days resulted in an effective inhibitio n of viral replication and gene expression, These results suggest ther apeutic potential for antisense oligomers in the treatment of patients who are chronically infected with HBV.