Pre-S mutations of hepatitis B virus affect genome replication and expression of surface antigens.
OBJECTIVE
In chronic hepatitis B virus (HBV) infection, quantitative HBV surface antigen (qHBsAg) is useful for monitoring viral replication and treatment responses. We aimed to determine whether pre-S mutations have any effect on circulating qHBsAg.


METHODS
Plasmids expressing 1–8 amino acid deletion in pre-S1 ("pre-S1Δ1-8") and 3-25 amino acid deletion in pre-S2 ("pre-S2Δ3-25") were constructed. At 72 h posttransfection into Huh7 cells, qHBsAg were measured using electrochemiluminescence immunoassay analyzer. To mimic milieus of quasispecies, we co-transfected either pre-S1Δ1-8 or pre-S2Δ3-25 with wild type (WT).


RESULTS
Pre-S mutations affected transcription and replication ability of HBV because of altered overlapping polymerase. Compared with WT, extracellular qHBsAg in pre-S1Δ1-8 and pre-S2Δ3-25 were on average 3.87-fold higher and 0.92-fold lower, respectively, whereas intracellular qHBsAg in pre-S1Δ1-8 and pre-S2Δ3-25 were 0.57-fold lower and 1.60-fold higher, respectively. Immunofluorescence staining of cellular HBsAg showed that pre-S1Δ1-8 had less staining and that pre-S2Δ3-25 had denser staining. As ratios of either pre-S1Δ1-8 or pre-S2Δ3-25:WT increased from 0:10 to 10:0 gradually, relative extracellular qHBsAg increased from 1.0 to 3.85 in pre-S1Δ1-8 co-transfection, whereas those decreased from 1.0 to 0.88 in pre-S2Δ3-25 co-transfection.


CONCLUSIONS
Pre-S mutations exhibit different phenotypes of genome replication and HBsAg expression according to their locations. Thus, qHBsAg level for diagnosis and prognostification in chronic HBV infection should be used more cautiously, considering emergences of pre-S deletion mutants.
Beom Kyung
BK
Kim
Sung Hoon
SH
Choi
Sung Hyun
SH
Ahn
Ae Ri
AR
Chung
Yong Kwang
YK
Park
Kwang-Hyub
KH
Han
Seungtaek
S
Kim
Hyon-Suk
HS
Kim
Jeon Han
JH
Park
Kyung Sik
KS
Kim
Hee Seung
HS
Lee
Yong Sang
YS
Cho
Kyun-Hwan
KH
Kim
Sang Hoon
SH
Ahn
D002478:Cells, Cultured; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D016679:Genome, Viral / Q000235:genetics*; D006514:Hepatitis B Surface Antigens / Q000235:genetics* / Q000378:metabolism; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D009154:Mutation; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D014779:Virus Replication / Q000235:genetics*
D006514:Hepatitis B Surface Antigens; D011498:Protein Precursors; C050806:presurface protein 1, hepatitis B surface antigen; C050807:presurface protein 2, hepatitis B surface antigen