Background: It is still unclear whether viral genetic variability influences response to interferon (IFN)-alpha treatment. Recent reports suggest that IFN-alpha effects may be associated with hepatitis B virus (HBV) post-transcriptional regulation. This study was designed to explore the heterogeneity of HBV post-transcriptional regulatory elements (HPRE) and the relationship between the diversity of HPRE and the response to IFN-alpha treatment.
Methods: The HPRE sequences from 31 Chinese patients infected with HBV were determined by directly sequencing of polymerase chain reaction (PCR) product, and comparing them to those from Caucasian patients. Subsequently, eukaryotic expression vectors containing HPRE at various points were constructed and transfected into HepG2 cells, which were then exposed to recombinant human cytokines.
Results: The T to C point mutation at nt 1504 and the C to T (G) at nt 1508 in HPRE were found in 21 and 19 patients with chronic hepatitis B, respectively; the C to T point mutation at nt 1509 was found in 17 patients. These point mutations did not exist in the HPRE of the Caucasian patients. The activity of the CAT gene obviously increased in the case of T to C point mutation at nt 1504, but did not change in the case of the C to T (G) mutations at nt 1508 and 1509. The activity of the CAT gene at these point mutations of HPRE could be inhibited by IFN-alpha/gamma and tumor necrosis factor (TNF)-alpha except for the point mutations at nt 1508 of HPRE which may escape the suppression role of IFN-alpha on HPRE.
Conclusions: There are point mutations between the HPRE of Chinese and Caucasian HBV patients, which might be correlated with response to IFN-alpha. The variation of HPRE might affect the function of HPRE and influence the regulative function of IFN-alpha other than that of IFN-gamma or TNF-alpha on HPRE.