Furthermore, clone sequencing was performed in two samples showing heterogeneous indels. As demonstrated in Table 3, quasispecies analysis indicates that about half of the MCC950 nmr strains contain preS deletions in these two patients. Table 3 Occurrence of preS deletion mutants in serial samples during ADV treatment Patients (CH) Start End PCR direct sequencing PCR direct sequencing Clone sequencing ADV 1 N D aa 65–78 (peS1), (+) (Jan 24,
2005) (Mar 22, 2005) 3/5 clones 2 N D aa 132–141 (preS2), (Dec 15, 2004) (Mar 21, 2005) 2/5 clones ADV 3 N N – (−) (Dec 17, 2004) (Feb 28, 2005) 4 N N – (Jan 14, 2005) (Jun 7, 2005) N, no deletion detected; D, deletion detected. No antiviral resistance resulted from preS2 deletion alone Next, we investigated if deletions alone could directly lead to antiviral resistance. Two preS2 deletions with high occurrence rates were introduced into the wt strain in a plasmid followed by treatment with lamivudine, https://www.selleckchem.com/HDAC.html adefovir, entecavir and tenofovir. As shown in Figure 4 and Additional file 1: Figure S1A-D, both preS2Δ1 and preS2Δ2 showed similar sensitivity to the wt strain for all four drugs. Since the wt strain in the plasmid was genotype D whereas our data were mainly from genotype C strains, we further tested a similar preS2 mutant using the genotype C plasmid and obtained the same result (data not shown). Therefore,
these preS2 deletion mutants alone did not have antiviral resistance. Figure 4 Constructed preS2 mutants and their sensitivity to antiviral see more drugs. Two deletions illustrated at the top were introduced into the wt genome in a plasmid, respectively. Constructed mutants were transfected into Huh7 cells with or without antiviral drug treatment as indicated in each plot. The viral replication level in a culture medium without drugs was denoted as
100%. The curves indicate the decrease in viral replication with increasing drug concentrations and the preS2 deletion alone did not change the mutants’ sensitivity to antiviral drugs. The crossover points between the horizontal line and the curves indicate the IC50 for each strain. *similar viral replication data of the Δ2 mutant with Urocanase drug treatment is shown in Additional file 1: Figure S1. We further compared the replication abilities of these strains in the absence of antiviral drugs, using HBsAg as the internal standard. Compared to the wt strain (100%), both mutants demonstrated slightly higher replication capacities (preS2Δ1,117%; preS2Δ2, 107%), however, statistical significance was not reached (Additional file 1: Figure S1E). Discussion Deletion patterns in the preS region upon host response to viral infection We analyzed deletions in HBV genomes with respect to deletion hotspots and their boundaries, the correlation of mutations to antiviral medication, and the structural features in preS deletions. We compared preS deletions in our samples with those in immuno-suppressed patients reported by Preikschat et al. .