Background and aims Deletion of 15-nucleotide or 18-nucleotide (nt) covering preS1 ATG frequently arises during chronic infection with HBV genotypes B and C. Since the second ATG is 33nt downstream, they truncate large (L) envelope protein by 11 residues like wild-type genotype D. This study characterised their functional consequences.
Methods HBV genomes with or without deletion were amplified from a patient with advanced liver fibrosis and assembled into replication competent 1.1mer construct. Deletion, insertion or point mutation was introduced to additional clones of different genotypes. Viral particles concentrated from transfected HepG2 cells were inoculated to sodium taurocholate cotransporting polypeptide (NTCP)-reconstituted HepG2 (HepG2/NTCP) cells or differentiated HepaRG cells, and HBV RNA, DNA, proteins were monitored.
Results From transfected HepG2 cells, the 15-nt and 18-nt deletions increased HBV RNA, replicative DNA and extracellular virions. When same number of viral particles was inoculated to HepG2/NTCP cells, the deletion mutants showed higher infectivity. Conversely, HBV infectivity was diminished by putting back the 18nt into naturally occurring genotype C deletion mutants and by adding 33nt to genotype D. Infectivity of full-length genotype C clones was also enhanced by mutating the first ATG codon of the preS1 region but diminished by mutating the second in-frame ATG. Removing N-terminal 11 residues from preS1 peptide 2–59 of genotype C potentiated inhibition of HBV infection and enhanced binding to HepG2/NTCP cells.
Conclusions The 15-nt and 18-nt deletions somehow increase HBV RNA, replicative DNA and virion production. Shortened L protein is more efficient at mediating HBV infection.
- antiviral therapy
- hepatitis B
- receptor binding
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Correction notice This article has been corrected since it published Online First. Typographical errors in the significance of this study box, table 1, figure 6 legend and funding statement have been corrected.
Author contributions: ST, JZ, JSL and QY designed the experiments. JL, JSL, SC, JZ, JW, QJ and QW performed the experiments. JL and JSL performed statistical analysis and interpretation of data. NSX and QY provided significant resources. JL drafted the manuscript. JSL, JZ and ST revised the manuscript.
Funding This work was supported by NIH grants R21AI142456, R01AI116639, the National Natural Science Foundation of China (81672009, 81672064, 81871640), and the Major Science and Technology Special Project of China (2017ZX10202202 and 2017ZX10202203). Jing Li was supported by China Scholarship Council.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.