Characteristics of HBV infection in 705 HIV-infected patients under lamivudine-based antiretroviral treatment from three regions in China Mingze Su,1 Lingjie Liao,2 Hui Xing,2 Shuai Wang,1,3 Yutang Li,4 Wei Lu,1,5 Lingyuan He,1 Juan Deng,1 Yiming Shao,2 Tong Li,1 Hui Zhuang1 1Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China; 2State Key Laboratory of Infectious Disease Prevention and Control, National Centre for AIDS/STD Control and Prevention, Chinese Centre for Disease Control and Prevention, Collaborative Innovation Centre for Diagnosis and Treatment of Infectious Diseases, Beijing 102206, China; 3Department of Laboratorial Science and Technology, School of Public Health, Peking University, Beijing 100191, China; 4Key Laboratory of Medical Molecular Virology of Ministries of Health and Education, Shanghai Medical College, Fudan University, Shanghai 200032, China; 5Department of Laboratory, The Second Affiliated Hospital of Medical College of Xi’an Jiaotong University, Xi’an, Shaanxi 710004, China Purpose: This study aimed to investigate the HIV and hepatitis B virus (HBV) co-infection in three HIV high endemic areas with different modes of HIV transmission and explore the HBV nucleos(t)ide analogue resistance (NUCr) substitutions in this cohort receiving antiretroviral therapy (ART). Patients and methods: The enrolled 705 HIV-infected patients were from three different regions in China and received lamivudine-based ART for at least 1 year. After screening for hepatitis B surface antigen (HBsAg), the hepatitis B e antigen (HBeAg), and antibody against hepatitis B core antigen (anti-HBc and anti-HBc IgM), HBV DNA in plasma of patients positive for HBsAg was tested. The reverse transcriptase (RT) sequences of HBV were analyzed by direct sequencing. Results: The overall HBsAg-positive rate was 7.1% (50/705) (Guangxi [25/170, 14.7%], ­Xinjiang [13/257, 5.1%], and Henan [12/278, 4.3%]). The age, transmission route, and ethnic status were found to be associated with HIV/HBV co-infection. We obtained 23 HBV RT sequences belonging to genotypes B (9/23, 39.1%), C (13/23, 56.5%), and D (1/23, 4.4%). About 65.2% (15/23) of RT sequences harbored NUCr substitutions, all of which had combination substitution patterns. Patients with HBV NUCr had significantly higher HBV DNA level and ratio of HBeAg-positive than those without NUCr. None of the patients was found to have both lamivudine-resistant HBV and HIV. Conclusion: Our results suggested that HBsAg-positive rate in the studied patients was similar to that of the general population in each of the studied regions, where the age, transmission route, and ethnic status might also play roles in HIV/HBV co-infection. The HBV combination NUCr substitutions were common in co-infected patients under ART. Monitoring of HBV infection and NUCr substitutions in HIV-infected patients would help in providing better clinical decisions and management, thus lowering patients’ risks to develop end-stage liver diseases. Keywords: human immunodeficiency virus, hepatitis B virus, co-infection, nucleos(t)ide analogue resistance, hepatitis B surface antigen