The central nervous system is a potential reservoir and possible origin of drug resistance in HBV

The significance of HBV in cerebrospinal fluid (CSF) is unclear. In the present study, synchronous serum and CSF samples were collected from 13 patients. HBV-DNA, full-length genome, quasispecies, phylogenetic tree, compartmentalization and mutation of reverse transcriptase (RT) region analyses were performed based on PCR and sequencing methods. We found HBV-DNA was detected in the CSF of 3 antiviral-naive patients and one patient after successful antiviral therapy. Complete full-length HBV genomes were isolated from the CSF of 5 patients, including 2 patients with undetectable serum HBV-DNA. Ten patients exhibited distinct CSF-serum quasispecies, 8 harbored independent CSF-serum genetic compartmentalization and phylogenetic trees, and 5 patients presented lamivudine/entecavir-associated resistance mutations in only the CSF. The frequencies of rtL180M and rtM204I/V mutations in both serum and CSF were higher in HIV/HBV-coinfected patients than in HBV-monoinfected patients (serum: rtL180M: 3.9% vs. 0, P = 0.004; rtM204I/V: 21.3% vs. 0, P < 0.001; CSF: rtL180M: 7.6% vs. 0, P = 0.026; rtM204I/V 7.6% vs. 1.6%, P = 0.097). Our data suggested CSF is a potential HBV reservoir, and HBV in CSF harbors distinct evolution and mutation models from that in serum. HIV infection increases the possibility of HBV rtL180M and rtM204I/V mutations in both serum and CSF.