EFFECT OF HEPATITIS-B VIRUS ON TUMOR-NECROSIS-FACTOR (TNF-ALPHA) GENE-EXPRESSION IN HUMAN THP-1 MONOCYTIC AND NAMALWA B-CELL LINES

In response to viruses, monocytes and B cells produce TNF alpha. There fore, we investigated TNF alpha gene expression and protein secretion in a human monocytic cell line, THP-1, and a Burkitt's lymphoma B-cell line, Namalwa, in response to hepatitis B virus (HBV). Stimulation by phorbol myristate acetate (PMA) (100 ng/ml for 48 h) induced TNF alph a secretion in THP-1 and Namalwa cells (100 to 300 pg/ml). In THP cell s, the optimum response (> 2000 pg/ml) was obtained in the presence of a second mitogenic signal such as lipopolysaccharide (LPS) (10 mu g/m l for 24 h). In our activation conditions, Northern blot analysis reve aled a marked accumulation of TNF alpha mRNA species at 1.7 kb in both cell lines. When PMA- or PMA+LPS-stimulated THP-1 cells were exposed to HBV, TNF alpha protein and mRNA significantly decreased (> 50%). In contrast, HBV exposure of PMA-activated Namalwa cells resulted in str ongly increased TNF alpha protein secretion (1 ng/ml). In this case, H BV induced TNF alpha mRNA accumulation that consisted of two types: a regular 1.7 kb and two novel high molecular weight (HMW) species at 3. 7 and 4.3 kb. Exposure of stimulated THP-1 and Namalwa cells to HBV re sulted in HBs and pre-S1 antigen production in the supernatants. In ad dition, HMW HBV DNA forms were detected in both cell lines, but with d istinct HindIII restriction patterns. These findings indicate that TNF alpha gene expression may be differently regulated by HBV in activate d human macrophages and B cells, and thus TNF alpha may be involved in the pathogenesis of HBV.