Compositional and functional alterations of intestinal microbiota in different clinical settings of chronic hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a public health problem worldwide that may progress to advanced stages of disease, such as liver cirrhosis and hepatocellular carcinoma (HCC). Gut microbiota dysbiosis has been observed and studied in early-stage and in the late stage of chronic HBV infection. Whereas, alterations of intestinal microbiota at different clinical phases of chronic HBV infection have not been comprehensively evaluated and compared. The aim of this study is to characterize the structural and functional alterations of the intestinal microbiota at different clinical settings of chronic HBV infection and try to elucidate the role of gut dysbiosis in disease progression. Microbiota of 37 fecal samples obtained from 13 chronic hepatitis B (CHB), 11 liver cirrhosis (CIR), 9 HCC patients and 5 normal controls (CN) were perspectively analyzed by 16S rRNA gene sequencing. Microbiota diversity and abundance at different taxonomy levels between groups and correlations between the taxa abundance and biochemical parameters were assessed. Compared with the CNs, α-diversity of microbiota in CHB and HCC groups decreased significantly (Shannon index, p<0.05). The microbial abundance increased in HBV infected subjects, especially the CIR patients, compared with CNs (Chao index, p<0.05). HBV infection and CNs samples were separated clearly in PCOA plot using unweighted UniFrac (ADONIS analysis: R2=0.166, p=0.004) at operational taxonomic units (OTU) level. Four genera, Blautia, Dorea, Ruminococcus_1 and Ruminococcus_2 that negatively correlated with serum level of HBsAg titers, total bile acid (TBA) and high-sensitivity C reactive protein (hs-CRP) were enriched in CNs, and were in low abundance in HBV infection groups. The abundance of Prevotella_9 and Megamonas genera that correlated positively with serum HBsAg titers (p<0.01) was enriched in HBV infection groups. Inferred functions of the microbiota in HBV infection groups are involved in down-regulated arginine and proline metabolism, glycolysis/gluconeogenesis and pyruvate metabolism, and up-regulated pyrimidine metabolism at KEGG level 3 pathway. Microbiota hierarchical clustering showed that HCC group is clustered with other three groups. Thus, gut dysbiosis resultant metabolic dysfunction of bile acid, amino acid and carbohydrate, over activated systemic inflammation, suppressed systemic immunity and energy metabolism that drive HBV infection related liver disease progression