Figure 1. Cumulative rate of complete viral suppression (HBV DNA <40-60 IU/mL) through 18 months in patients who continued initial ETV dose, increased ETV dose, and switch to ETV/TDF combination therapy after partial response to ETV monotherapy. 703 Multidrug-Resistant Chronic Hepatitis B - Impact on Therapy Outcome Filipe Vilas-Boas, Helder Cardoso, Rosa Coelho, Susana Rodrigues, Susana Lopes, José Alexandre Sarmento, Pedro Pereira, Ana Horta e Vale, Fernando Araújo, Guilherme Macedo BACKGROUND: The occurrence of Hepatitis B virus (HBV) polymerase mutations was a major limitation of chronic hepatitis B (CHB) treatment until the introduction of entecavir (ETV) and tenofovir (TDF). Cross-resistance to ETV is well documented in the presence lamivudine (LAM) resistance mutations and ETV specific mutations. To date, no mutations that confer resistance to TDF have been described, nevertheless adefovir (ADF)-associated resistance mutation N236T proved to confer low-level resistance to TDF in studies in vitro. METHODS AND AIMS: Retrospective analysis of HBV monoinfected patients treated with TDF or ETV that performed viral mutations testing (mostly INNO-LiPA hybridization assays, Innogenetics, Belgium) in a single center. Evaluation of the efficacy of antiviral therapy in the presence of multidrug-resistant mutants (MDR). RESULTS: In a group of 181 CHB patients treated with TDF or ETV (5% combination TDF+ETV), 89 (49%) had HBV polymerase gene mutation analysis. Sixty-eight patients (76% of tested) presented several mutations including N236T and 8% had only nucleoside resistant strains. MDR were detected in 9% of naïve patients and 49.5% of previously treated patients. Fifty-three (78%) of the MDR HBV patients were treated with TDF and 15 (22%) were taking ETV. MDR were more frequent in HBeAg positive hepatitis (p<0.001), in patients with previous failure of antiviral therapy (lamivudine, adefovir or interferon; p<0.001) and in patients under combination therapy (p=0.003). The presence of cirrhosis at start of therapy was associated with lower frequence of MDR (p= 0.018). Quantitative HBsAg>250 IU/mL at the beginning of therapy (p=0.002) and baseline HBV viral load >100000 IU/mL (p=0.008) were predictive of MDR presence. During therapy, patients without MDR achieved more HBeAg negativation (p=0.007), anti-HBe seroconver- sion (p=0.019) and more frequently achieved HBV DNA suppression (p=0.003). Globally, mean treatment duration until HBV DNA undetectability was 24.8 months with MDR versus 8.2 months without (p<0.001). In MDR CHB patients, treatment with TDF was associated with greater HBV DNA supression than ETV (p<0.001), and shorter time to undetectability (18.9 versus 45.2 months, p=0.001). In multivariate analysis, baseline MDR (p<0.001), HbeAg positive (p<0.001) and viremia (p=0.043) were independently associated with longer time to HBV DNA undetectability. CONCLUSIONS: Multidrug-resistant CHB was detected in 9% of naive patients and in half of those previously treated. Its occurrence was associated with more difficult to treat CHB and slower treatment response. TDF was more effective than ETV in MDR HBV patients. This impact in antiviral therapy could have implications in CHB management, particularly in severe cases with decompensated cirrhosis and/or indication for liver transplantation. 704 Impact of Active Hepatitis B Virus DNA Replication on Clinical Outcomes in Patients With Hepatitis C and B Co-Infection Robert Kruse, Jennifer R. Kramer, Zhigang Duan, Liang Chen, Hashem El-Serag, Fasiha Kanwal Background and Aim: Hepatitis C virus (HCV) and hepatitis B virus (HBV) can modulate each other when co-infecting the same host. Although viral dominance patterns are unpredict- able, it is believed that HCV is dominant in the majority of HCV-HBV co-infected patients as evidenced by low to absent HBV DNA levels in these patients. However, the impact of HBV or HCV viral dominance on clinical outcomes remains unclear. Methods: We conducted a retrospective cohort study of U.S. patients with confirmed HCV viremia who sought care at the national Veterans Administration between 1997 and 2005. We identified patients with HBV co-infection on the basis of a positive hepatitis B surface antigen, serum HBV DNA, or hepatitis B e antigen within one year of the HCV diagnosis date. We classified co- infected patients with "HBV dominance" if they had a positive test for HBV DNA in the serum; patients who were negative for HBV DNA were considered to have "HCV dominance". We used Cox proportional hazards regression models to compare the risk of cirrhosis, S-925 AASLD Abstracts hepatocellular cancer (HCC), and mortality in patients with HBV dominance (HCV RNA+ HBV DNA+) and those with HCV dominance (HCV RNA- HBV DNA-) to patients with HCV mono-infection after adjusting for demographic (age, gender, race), clinical (diabetes, HIV co-infection, alcohol use, Deyo comorbidity score), and antiviral treatment (interferon, lamivudine, adefovir, entecavir, telbivudine or tenofovir) factors. Results: We identified 102,971 patients with HCV viremia (HCV RNA+). Of these, 1,431 patients had HCV-HBV co-infection (mean age=48.8 years, 98.3% male, 53.3% Caucasian, 35.6% African American). A total of 695 co-infected (48.5%) patients underwent testing for serum HBV DNA; of these 314 (45.1%) patients were HBV DNA+, whereas 381 (54.8%) were HBV DNA-. As shown in the Table, co-infected patients with HBV dominance had the highest relative risk of cirrhosis, HCC and mortality compared with mono-infected patients. After adjusting for covariates in the multivariable models, patients with HBV dominance (HCV RNA+ and HBV DNA+) were more likely to develop cirrhosis (adjusted hazard ratio [HR]= HR=2.15, 95%CI= 1.66-2.79), develop HCC (adjusted HR=1.97, 95%CI=1.16-3.33), and die (adjusted HR= 1.37, 95%=1.12-1.67) than HCV mono-infected patients. There were no differences in the risk of cirrhosis, HCC, or overall mortality between co-infected patients with HCV dominance (HCV RNA+ but HBV DNA-) and those with HCV mono-infection. Conclusions: In patients with HCV-HBV co-infection, HBV was dominant in approximately 50% of the patients who were tested for HBV DNA. Presence of active HBV replication resulted in significantly worse outcomes in HCV-HBV co-infected patients. In contrast, absence of HBV replication was associated with a clinical course similar to that of HCV mono-infected patients. 760 vFLIP, a Viral Regulator of Caspase-8, Induces Acute, Death Mediated Liver Damage That Promotes Chronic Fibrotic Liver Disease Claudia Günther, Stefan J. Wirtz, Markus F. Neurath, Helmut Neumann, Christoph Becker Background: Cell death mechanisms are frequently involved in virus mediated acute and chronic liver disease. Receptor mediated programmed cell death is initiated by activation of caspase-8. The viral protein vFLIP, which is expressed by certain herpesviruses, can interact with caspase-8 thereby inhibiting its activation. Therefore vFLIP may reprogram cell death towards programmed necrosis that causes inflammation. Aims: In this study we investigated for the first time the impact of vFLIP for the development of acute and chronic liver disease. Methods: In vivo overexpression of vFLIP in hepatocytes was achieved by hydrodynamic delivery (HD) of a vector encoding the Kaposi sarcoma herpesvirus vFLIP, controlled by liver-specific regulatory elements. The vector was injected in wildtype, Rag- deficient (Rag-/-) and Rip3 deficient (Rip3-/-) adult mice. Results: Four days after HD, vFLIP vector-injected wildtype mice (vFLIPHD) but not control vector-injected mice showed excessive cell death and massive inflammatory immune infiltrates. The inflammatory pheno- type of vFLIPHD was further confirmed by increased serum transaminases, suggesting that expression of vFLIP in hepatocytes results in acute liver inflammation. In order to characterize the contribution of lymphocytes in vFLIP induced liver disease, the vFLIP vector was injected in Rag-/- mice. These mice developed similar liver pathologies to wildtype animals, suggesting that lymphocytes are not involved in vFLIP induced cell death and inflammation. Gene expression analysis revealed a strong upregulation of death receptor ligands in vFLIP express- ing hepatocytes. Moreover it was observed that vFLIPHD mice were highly susceptible to Tnf-α administration. Whereas all control vector injected mice were still alive after 5 h, vFLIPHD mice showed significantly more pronounced hypothermia and lethality of 95%. We could identify an excessive number of TUNEL positive dying hepatocytes in vFLIPHD mice, suggesting necrotic rather than apoptotic cell death. To investigate whether vFLIP induce Rip-mediated necroptosis in hepatocytes, we injected the vFLIP vector into mice lacking the necroptosis mediator Rip3 (Rip3-/- mice). Injection of vFLIP into Rip3-/- animals caused liver damage comparable to wildtype animals. Moreover Rip3-/- and wildytpe animals showed same levels of serum transaminases, suggesting that Rip3 is not involved in vFLIP induced cell death and inflammation. Notable, 4 weeks after HD, vFLIPHD mice showed increased hepatic collagen as demonstrated by H&E and Sirius Red staining, indicating that vFLIP induced liver damage promotes liver fibrosis. Conclusion: The study has shown for the first time, that overexpression of the viral protein vFLIP in hepatocytes induces acute, death mediated liver inflammation that promotes chronic fibrotic liver disease. AASLD Abstracts