Up to 30 %of GenBank HBV genome sequences are recombinations between genotypes (1), a fact that could influence clinical outcomes and antiviral treatment response in chronic HBV (CHB) patients. Our aim was to study the evolution of the HBV genotypic pattern in the absence and presence of lamivudine (LAM) and identify possible genotypic recombinations. METHODS Thirty sequential serum samples from 10 CHB patients failing LAM were included: baseline (BA), after a treatment-free period (TF), and after LAM. In each sample, 2 HBV genome fragments were analyzed by ultra-deep pyrosequenc-ing (GS-FLX, Roche): nucleotides (nt) 1596-1912 (overlapping the X and pre-core [PC] regions) and nt 615-969

(overlapping the polymerase [P] and surface [S] regions). In variants

at frequencies >0.25%, HBV genotype was determined by phylogenesis using an in-house bioinformatics algorithm. RESULTS We obtained 379 438 sequences in the X-PC region and 864 944 BMS-777607 mouse in P-S. Genotype mixtures differed between the two regions (Table), and both regions showed genotype mixture variations over time (BA-TF-LAM), CONCLUSIONS Discrepancies between genotype HM781-36B mouse mixtures in the P-S and X-PC regions suggest inter-genotypic recombination that questions the current classification of HBV genotypes. Changes over time in genotype mixtures evidence the complex dynamics of the HBV quasi-species to adapt to new situations, as was shown by dominant selection of genotype A polymerase after LAM. (1)Weifeng Shi, Virology 2012;427:51-59 Funding: FIS-PI12/1893 (Insti-tuto de Salud Carlos III, European Regional Development Fund) ID: Patient. S-P region (nucleotides [nt] 615-969). X-PC region {nt 1596-1912], in this region genotypes D and E are too similar to be distinguished Tolmetin therefore are classified as D/E. BA: Basal sample; UT: Sample after 1-2 years without treatment,

LAM: Sample after 1-4 years treatment with Lamivudine. *Patient 9-UT: viral load level did not allow ultra-deep pyrosequencing analysis. Disclosures: Rafael Esteban – Speaking and Teaching: MSD, BMS, Novartis, Gilead, Glaxo, MSD, BMS, Novartis, Gilead, Glaxo, Janssen Maria Buti – Advisory Committees or Review Panels: Gilead, Janssen, Vertex, MSD; Grant/Research Support: Gilead, Janssen; Speaking and Teaching: Gil-ead, Janssen, Vertex, Novartis The following people have nothing to disclose: Andrea Caballero, Josep Gregori, Maria Homs, David Tabernero, Maria Blasi, Rosario Casillas, Josep Quer, Leonardo Nieto, Henar Valbuena, Francisco Rodriguez-Frias Background and aim: In HBV infection, interferon and other antiviral drugs can control HBV replication. However it is still difficult to eradicate HBV completely because covalently closed circular DNA (cccDNA) stably remains in the nucleus of hepato-cytes as mini-chromosomes. cccDNA works as a template for transcription for viral mRNAs after removal of nucleoside analogues and viral replication and worsening of hepatitis often occurs.