Combination therapy with lamivudine and adenovirus causes transient suppression of chronic woodchuck hepatitis virus infections

Treatment of hepatitis B virus carriers with the nucleoside analog lamivudi ne suppresses virus replication. However, rather than completely eliminatin g the virus, long-term treatment often ends in the outgrowth of drug-resist ant variants. Using woodchucks chronically infected with woodchuck hepatiti s virus (WHV), we investigated the consequences of combining lamivudine tre atment with immunotherapy mediated by an adenovirus superinfection. Eight i nfected woodchucks were treated with lamivudine and four were infected with similar to 10(13) particles of an adenovirus type 5 vector expressing beta -galactosidase. Serum samples and liver biopsies collected following the c ombination therapy revealed a 10- to 20-fold reduction in DNA replication i ntermediates in three of four woodchucks at 2 weeks after adenovirus infect ion. At the same time, covalently closed circular DNA (cccDNA) and viral mR NA levels both declined about two- to threefold in those woodchucks, while mRNA levels for gamma interferon and tumor necrosis factor alpha as well as for the T-cell markers CD4 and CD8 were elevated about twofold. Recovery f rom adenovirus infection was marked by elevation of sorbitol dehydrogenase, a marker for hepatocyte necrosis, as well as an 8- to 10-fold increase in expression of proliferating cell nuclear antigen, a marker for DNA synthesi s, indicating significant hepatocyte turnover. The fact that replicative DN A levels declined more than cccDNA and mRNA levels following adenovirus inf ection suggests that the former decline either was cytokine induced or refl ects instability of replicative DNA in regenerating hepatocytes. Virus tite rs in all four woodchucks were only transiently suppressed, suggesting that the effect of combination therapy is transient and, at least under the con ditions used, does not cure chronic WHV infections.