OCCULT HEPATITIS B VIRUS INFECTION AND ASSOCIATED GENOTYPES AMONG HBSAG-NEGATIVE SUBJECTS IN BURKINA FASO

Background: Occult Hepatitis B virus infection (OBI), is characterized by the absence of detectable HBsAg in the blood of a person assumed to be healthy. It remains a potential transmission threat and risk to HBV chronic infection. The purpose of this study was to determine the OBI prevalence among HBsAg negative subjects and to characterize associated genotypes. Methods: Blood samples of 219 HBsAg-negative subjects tested by ELISA were collected. HBV DNA was investigated in all samples. Viral loads were determined using quantitative real-time PCR. All samples were screened for HBV markers (anti-HBc, anti-HBe, HBsAg). The Pre-S/S region of the HBV genome was sequenced. The database was analyzed using the SPSS and Epi info softwares. Phylogenetic analysis was performed using the BioEdit and MEGA softwares. Results: Of the 219 samples, 20.1 % were anti-HBc positive, 1.8 % HBeAg and 22.8 % were anti-HBe positive. Fifty-six 56 (25.6 %) of the samples had a detectable HBV DNA and viral loads ranging from 4 IU/mL to 13.6 106 IU/mL. Sixteen of them (16/56) had a viral load < 200 IU/mL, resulting in an OBI prevalence of 7.3 % (16/219) in our study. The remaining 40 subjects had viral loads ˃ 200 IU/mL, resulting in a “false OBI” prevalence of 18.3% (40/219). HBV genotype E was predominant followed by the quasi-sub-genotype A3. A single "false OBI" strain had the characteristic mutation G145R. Other mutations were observed and all located in the major hydrophilic region (MHR) of the S gene. Conclusion: The study reported a prevalence of 7.3% of occult hepatitis B infection. It confirms the predominance of genotype E and the existence of a subgroup of quasi-sub-genotype A3 of HBV in Burkina Faso. It further provides information on the existence of “false OBI “. This study has found mutations in the major hydrophilic region (MHR) of the pre-S/S gene of HBV. Key words: HBV, OBI, Genotypes, Real-time PCR, Sequencin