EVIDENCE FOR SELECTION OF HEPATITIS-B MUTANTS AFTER LIVER-TRANSPLANTATION THROUGH PERIPHERAL-BLOOD MONONUCLEAR CELL INFECTION

Background/Aims: Despite anti-HBs immunoglobulin therapy, hepatitis B virus (HBV) infection recurs in a high proportion of patients transpla nted for HBsAg positive and serum HBV DNA negative chronic liver disea se, The contribution of HBV genetic variability to disease recurrence has not been yet thoroughly addressed, We have therefore undertaken a detailed comparison of preS/S and preC/C sequences in two selected pat ients with recurrence of HBsAg and HBV DIVA after transplantation. Met hods: PreS/S and preC/C regions were amplified by PCR from the serum, peripheral blood mononuclear cell (PBMC) and liver tissues of two pati ents transplanted for end stage HBV-related cirrhosis, Samples were ta ken both pre- and post-transplantation, HBV-sequences from four to nin e clones were determined and compared. Results: A mixing of different HBV DNA molecules was observed within and between serum, liver and PBM C samples, Sequences from both patients showed mutations in the preC r egion which abolished HBeAg secretion, and in the preS2 initiation cod on which prevented preS2 envelope protein production, In addition, for both patients, deletions in the preS2 domain (3 and 21 base pairs) le d to the expression of modified preS1 envelope protein. For one patien t, the predominant HBs protein sequence found in the PBMC before trans plantation showed four specific mutations, One of these mutations was in the ''a'' determinant (codon 144, asparagine to glycine change) of the major envelope protein, These mutations were not detected, as pred ominant mutations, in the liver and serum pre-orthotopic liver transpl ant samples. In contrast, after liver transplantation, this was the ma jor form identified in serum, liver and PBMC. Conclusions: Our results have shown the selection of different HBV DNA molecules in liver and mononuclear cells, In addition, they provide direct evidence for the r ole of PBMC in the infection of liver grafts and support the hypothesi s that infection of PBMC might lead to selection of HBV variants which would escape immune therapy Finally, we provide in vivo evidence for reinfection of the liver by HBV particles lacking preS2 envelope prote in expression.