Different types of viral‑host junction found in HBV integration breakpoints in HBV‑infected patients

The present study surveyed the characteristics of hepatitis B virus (HBV) integration in the liver genomes of patients with acute hepatitis B (AHB), carriers of inactive hepatitis B surface antigen (HBsAg), and patients with chronic hepatitis B (CHB) receiving antiviral treatment. 'Short‑read' whole genome sequencing (WGS) with an average of 4,879x coverage for HBV integration was performed in three patients with AHB, two carriers of inactive HBsAg, and 13 patients with CHB receiving antiviral treatment. Conventional polymerase chain reaction and Sanger sequencing were used to verify integration breakpoints supported by at least two paired‑end reads, and viral‑host chimeric transcripts were surveyed simultaneously. HBV integration breakpoints were 100% identified with an average of 138.2±379.9 breakpoints per sample. The numbers of HBV integration breakpoints were positively associated with the sequencing depth coverage numbers and levels of intrahepatic covalently closed circular DNA, respectively (P<0.0001 and P<0.0001). Four types of viral‑host junction in 14 HBV integration breakpoints were detected (two viral junctions mapped in the HBs gene, one in the Precore gene, and others within the HBx gene): Forward simple junction, reverse simple junction, forward and reverse complicated junction, and microhomology were found in many of the junctions. Expression of viral‑human chimeric transcripts was observed in several breakpoints, including the HBs gene. As a result, HBV can integrate into the host gene in the same manner as non‑homologous end joining and microhomology‑mediated end joining with numerous sites, and a close association may exist between HBV integration and patient prognosis. HBx integration may be indispensable for viral‑host chimeric transcription and HBsAg may be produced from integrated DNA.