A new vaccine escape mutant of hepatitis B virus causes occult infection

There is growing public concern regarding assay sensitivity to HBsAg mutants in clinical diagnosis and vaccine escape. The aim of this study is to introduce a new HBsAg mutant strain. The serum samples were those of patient X at the age of 3 months and 3 years respectively, and of her mother immediately before parturition, which were used to amplify the HBsAg-coding DNA fragments by PCR. The HBsAg DNA sequences were translated into their corresponding amino acid sequences and then aligned in pubmed with nucleotide blast. The sequencing data of S coding regions shows that patient X has been infected by a new HBV variant with an A to C substitution at nt431, resulting in an Asp (GAC) to Ala(GCC) substitution at aa144 of major protein; CC to AA substitution at nt359 and nt360, resulting in an Pro (CCC) to Gln(CAA) substitution at aa120 of pre a epitope; A to G substitution at nt491, resulting in an Glu(GAG) to Gly (GGG) substitution at aa164 of post a epitope. Three new mutations (S171F, S174N and Q181R) at the antigenic epitopes of HBV presented by HLA class I molecules are found. The HBV mutant strain causes vaccine escape and occult infection.