Cross-sectional evaluation of circulating hepatitis B virus RNA and DNA: Different quasispecies?

BACKGROUND Different forms of pregenomic and other hepatitis B virus(HBV)RNA have been detected in patients’sera.These circulating HBV-RNAs may be useful for monitoring covalently closed circular DNA activity,and predicting hepatitis B eantigen seroconversion or viral rebound after nucleos(t)ide analog cessation.Data on serum HBV-RNA quasispecies,however,is scarce.It is therefore important to develop methodologies to thoroughly analyze this quasispecies,ensuring the elimination of any residual HBV-DNA.Studying circulating HBV-RNA quasispecies may facilitate achieving functional cure of HBV infection.AIM To establish a next-generation sequencing(NGS)methodology for analyzing serum HBV-RNA and comparing it with DNA quasispecies.METHODS Thirteen untreated chronic hepatitis B patients,showing different HBV-genotypes and degrees of severity of liver disease were enrolled in the study and a serum sample with HBV-DNA>5 Log10 IU/mL and HBV-RNA>4 Log10 copies/mL was taken from each patient.HBV-RNA was treated with DNAse I to remove any residual DNA,and the region between nucleotides(nt)1255-1611 was amplified using a 3-nested polymerase chain reaction protocol,and analyzed with NGS.Variability/conservation and complexity was compared between HBV-DNA and RNA quasispecies.RESULTS No HBV-DNA contamination was detected in cDNA samples from HBV-RNA quasispecies.HBV quasispecies complexity showed heterogeneous behavior among patients.The Rare Haplotype Load at 1%was greater in DNA than in RNA quasispecies,with no statistically significant differences(P=0.1641).Regarding conservation,information content was equal in RNA and DNA quasispecies in most nt positions[218/357(61.06%)].In 102 of the remaining 139(73.38%),HBV-RNA showed slightly higher variability.Sliding window analysis identified 4 hyper-conserved sequence fragments in each quasispecies,3 of them coincided between the 2 quasispecies:nts 1258-1286,1545-1573 and 1575-1604.The 2 hyper-variable sequence fragments also coincided:nts 1311-1344 and 1461-1485.Sequences between nts 1519-1543 and 1559-1587 were only hyper-conserved in HBV-DNA and RNA,respectively.CONCLUSION Our methodology allowed analyzing HBV-RNA quasispecies complexity and conservation without interference from HBV-DNA.Thanks to this,we have been able to compare both quasispecies in the present study.