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Journal of Clinical Microbiology, June 2006, p. 2191-2198, Vol. 44, No. 6
0095-1137/06/$08.00+0     doi:10.1128/JCM.00057-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Unusual Naturally Occurring Humoral and Cellular Mutated Epitopes of Hepatitis B Virus in a Chronically Infected Argentine Patient with Anti-HBs Antibodies

Dto. Microbiología, Fac. de Medicina, UBA,¹ Servicio de Huellas Digitales Genéticas y Cátedra de Genética y Biología Molecular, Fac. de Farmacia y Bioquímica, UBA,² Div. Clínica Médica-Hepatología, Hospital Argerich, Buenos Aires, Argentina³

Received 10 January 2006/ Returned for modification 11 February 2006/ Accepted 10 March 2006

Serum hepatitis B virus (HBV) DNA was extracted from a chronically infected patient with cocirculation of hepatitis B surface antigen (HBsAg) and anti-HBs antibodies. Direct PCR and clone-derived sequences of the S and overlapped P genes were obtained. DNA sequences and phylogenetic analysis ascribed this isolate to genotype A (serotype adw2). Five of six HBV DNA clones exhibited point mutations inside and outside the major hydrophilic region, while the sixth clone exhibited a genotype A "wild-type" amino acid sequence. Observed replacements included both humoral and/or cellular (major histocompatibility complex class I [MHC-I] and MHC-II) HBV mutated epitopes, such as S45A, P46H, L49H, C107R, T125A, M133K, I152F, P153T, T161S, G185E, A194T, G202R, and I213L. None of these mutants were individually present within a given clone. The I213L replacement was the only one observed in the five clones carrying nonsynonymous mutations in the S gene. Some of the amino acid substitutions are reportedly known to be responsible for the emergence of immune escape mutants. C107R replacement prevents disulfide bonding, thus disrupting the first loop of the HBsAg. Circulation of some of these mutants may represent a potential risk for the community, since neither current hepatitis B vaccines nor hyperimmune hepatitis B immune globulin are effectively prevent the liver disease thereto associated. Moreover, some of the recorded HBsAg variants may influence the accuracy of the results obtained with currently used diagnostic tests.