Discussion: In our study, despite the frequent association of the primary resistance mutations M204V/I with the compensatory L180M, V173L, and L80V/I mutations, lamivudine-resistant HBV strains tend to be associated with lower viral loads compared to wild-type strains; further characterization of the viral strains, using Next-Generation Sequencing (NGS), might reveal the presence of other mutations that alter viral replication.
Global prevalence and phylogeny of hepatitis B virus (HBV) drug and vaccine resistance mutations.
Method: ETV resistance: Two or more amino acid substitutions are required across the HBV RT protein to confer resistance to ETV which could occur as a combination of M204I/V with one or more of the following substitutions L80I/V, I163V, I169T, V173L, L180M, A181S/T/V, T184X, A186T, S202C/G/I/R, M250I/V and/or C256S/G.
Result: Genotype C had the highest prevalence of all of these mutations, apart from L80I/M/V which is most common in Genotype
Entecavir resistance in a patient with treatment-naive HBV: A case report.
PMID: 33903819
2021
Molecular and clinical oncology
Discussion: For example, Kim et al , by comparing frequencies and types of pre-existing RT mutations in treatment-naive patients, found a significantly higher rate of RT mutations in patients with HCC compared with patients with chronic hepatitis, and also identified three mutations that induced NA resistance (rtL80I, rtN139K/T/H and rtM204I/V) and were significantly associated with the progression of HCC.
Discussion: There were 8 mutations in the RT region, rt
High Prevalence of Preexisting HBV Polymerase Mutations in Pregnant Women Does Not Limit the Antiviral Therapy Efficacy.
PMID: 33986897
2021
The Canadian journal of infectious diseases & medical microbiology
Result: RtM204I/V + rtL80I/V and rtM204I + rtA181 T/V may affect the sensitivity to LAM, TBV, and ADV; they also presented but the proportions of the mutations were low (Table 3).
Result: At the compensatory mutation sites, 15.1% (11/73) participants had L80I/V mutation that is associated with resistance to LAM.
Discussion: Furthermore, some pregnant women had multibase mutations combined with rtM204I/V at baseline, including rtM204I + rtA181 T/V,
Prevalence of Potential Resistance Related Variants Among Chinese Chronic Hepatitis B Patients Not Receiving Nucleos(T)ide Analogues.
Abstract: Primary and secondary DR variants were found in 7.3% (15/206) of patients, including rtL80I/V, rtI169T, rtV173L rtL180M, rtA181T/V, rtM204I/V, and rtN236T.
Result: Primary and/or secondary DR variants were found in 7.3% (15/206) of patients, and included rtL80I/V, rtI169T, rt PMID: 32915862
2020
PloS one
Abstract: Resistance mutations included rtL80I, rtV173L, rtL180M, rtM204I/V and the overlapping sE164D, sW182*, sI195M and sW196LS variants.
Result: Amino acid changes including rtL80I, rtV173L, rtL180M,
Epidemiology, risk factors, and molecular characterization of occult hepatitis B infection among anti-hepatitis B core antigen alone subjects.
Discussion: M204I/V mutations are frequently accompanied by compensatory mutations in other domains such as 59 rtV173L, rtL180M, rtT184S/G, 58 rtI169T, rtS202I, rtL80V/I and rtQ215S which enhanced the replication efficiency of rt204I/V mutants without significantly affecting lamivudine resistance, by compensating the decrease in efficiency due to resistance-associated changes.
Naturally occurring core protein mutations compensate for the reduced replication fitness of a lamivudine-resistant HBV isolate.
Introduction: However, compensatory mutations have been reported to partially restore the viral replication capacity, including rtL80V/I, rtL82M, rtV173L and rtV207I, mostly in the RT region of pol.
HBV mutation literature information.
PMID: 
2022
Frontiers in microbiology
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