Emergence of a novel lamivudine-resistant hepatitis B virus variant with a substitution outside the YMDD motif.
Lamivudine is a major drug approved for treatment of chronic hepatitis B virus (HBV) infection. Emergence of drug-resistant mutants with amino acid substitutions in the YMDD motif is a well-documented problem during long-term lamivudine therapy. Here we report a novel lamivudine-resistant strain of HBV with an intact YMDD motif, which included an amino acid substitution, rtA181T, in the reverse transcriptase (RT) domain of HBV polymerase. The substitution also induced a unique amino acid substitution (W172L) in the overlapping hepatitis B surface (HBs) protein. The YMDD mutant strains were not detected even by using the sensitive peptide nucleic acid-mediated PCR clamping method. The detected nucleotide substitution was accompanied by the emergence of an additional nucleotide substitution that induced amino acid change (S331C) in the spacer domain. The rtA181T mutant strain displayed a threefold decrease in susceptibility to lamivudine in in vitro experiments in comparison with the wild type. In vivo analysis using human hepatocyte-chimeric mice confirmed the resistance of this mutant strain to lamivudine. We developed a method to detect this novel rtA181T mutation and a previously reported rtA181T mutation with the HBs stop codon using restriction fragment length polymorphism PCR and identified one patient with the latter pattern among 40 patients with lamivudine resistance. In conclusion, although the incidence is not high, we have to be careful regarding the emergence of lamivudine-resistant mutant strains with intact YMDD motif.
Yatsuji
Hiromi
H
Department of Medical and Molecular Science, Division of Frontier Medical Science, Programs for Biomedical Research, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan. chayama@hiroshima-u.ac.jp
Noguchi
Chiemi
C
Hiraga
Nobuhiko
N
Mori
Nami
N
Tsuge
Masataka
M
Imamura
Michio
M
Takahashi
Shoichi
S
Iwao
Eiji
E
Fujimoto
Yoshifumi
Y
Ochi
Hidenori
H
Abe
Hiromi
H
Maekawa
Toshiro
T
Tateno
Chise
C
Yoshizato
Katsutoshi
K
Suzuki
Fumitaka
F
Kumada
Hiromitsu
H
Chayama
Kazuaki
K
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D020816:Amino Acid Motifs; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004279:DNA, Viral / Q000235:genetics; D024882:Drug Resistance, Viral / Q000235:genetics; D006514:Hepatitis B Surface Antigens / Q000378:metabolism; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics*; D022781:Hepatocytes / Q000821:virology; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology*; D051379:Mice; D009154:Mutation / Q000235:genetics; D063065:Organophosphonates / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D014162:Transfection; D014779:Virus Replication
D000998:Antiviral Agents; D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D063065:Organophosphonates; D012367:RNA, Viral; D019259:Lamivudine; C053001:adefovir; D000225:Adenine