Occult Hepatitis B Virus Infection: Analysis Of HBV Gene Mutation

Objective: The prevalence of cryptogenic hepatitis in clinical practice was 5% to 10%. Recently, Hepatitis B virus was founded to be one of the etiologies of cryptogenic hepatitis and that kind of infection was called occult HBV infection and which was one of the big problems of medical practice and epidemiology. Occult HBV infection can affect the diagnosis of HBV infection and lead to the sprees of HBV and was related with chronic liver diseases, cirrhosis and hepatocellular carcinoma. So the study of the reason of HBV occult infection was so important that we aim to investigate the incidence of occult hepatitis among chronic liver diseases of unknown etiology to study the molecular mechanism of HBV occult infection by studying the HBV gene mutations.Methods: (1) collection of cases and serum: to collect the clinical information and serum of 104 patients who were diagnosed of cryptogenic hepatitis. (2)Treatment of samples:7 kinds of methods such as boiling , sodium octanote and phenol-chloroform, have been used. The results have been compared based on the obtaining rate , sensitivity of amplification and reproducibility to look for a method which was more suitable to detect HBV DNA in an occult infection.(3)Primers design: to design and compare the effectivity of different set of nested primers which were located at s gene , X gene and c gene respectively. (4)To check the occult HBV infection by nested PCR. (5)The positive PCR products were sequenced and analysed to find mutations.Results:(1)The treatment of samples with sodium octane–phenol-chloroform for the detection of HBV DAN is more sensitive than the other methods. (2)13 cases were infected with HBV in the 104 patients who were once diagnosed with hepatitis of unknown etiology. (3)Sequencing of the amplified fragments showed mutations in the region of X gene and the overlapping core promoter , enhancerⅡ.No significant mutations were founded in the region of s gene.Conclusion:(1)The octanoate-phenol-chloroform method may be the best choice of template preparation for PCR for occult HBV infection. (2)Occult HBV infections may account for a high proportion of chronic liver diseases of"unknown"etiology. The molecular mechanism of HBV occult infection was associated with mutations in X gene and the overlapping core promoter, enhancerⅡ.