Clade homogeneity and low rate of delta virus despite hyperendemicity of hepatitis B virus in Ethiopia

BACKGROUND: Although hepatitis B virus (HBV) is hyperendemic and heterogeneous in its genetic diversity in Ethiopia, little is known about hepatitis D virus (HDV) circulating genotypes and molecular diversity. METHODS: A total of 321 hepatitis B surface antigen (HBsAg) positives (125 HIV co-infected, 102 liver disease patients and 94 blood donors) were screened for anti-HDV antibody. The anti-HDV positive sera were subjected to Real time PCR for HDV-RNA confirmation. The non coding genome region (spanning from 467 to 834 nucleotides) commonly used for HDV genotyping as well as complete HDV genome were sequenced for genotyping and molecular analysis. RESULTS: The anti-HDV antibody was found to be 3.2% (3) in blood donors, 8.0% (10) in HIV co-infected individuals and 12.7% (13) in liver disease patients. None of the HIV co-infected patients who revealed HBV lamivudine (3TC) resistance at tyrosine-methionine/isoleucine-aspartate-aspartate (YM(I)DD) reverse transcriptase (RT) motif with concomitant vaccine escape gene mutants was positive for anti-HDV antibody. The HDV viremia rate was 33.3%, 30.0% and 23.1% in respect to the above study groups. All the six isolates sequenced were phylogenetically classified as HDV genotype 1 (HDV-1) and grouped into two monophyletic clusters. Amino acid (aa) residues analysis of clathrin heavy chain (CHC) domain and the isoprenylation signal site (Py) at 19 carboxyl (C)-terminal amino acids (aa 196–214) and the HDV RNA binding domain (aa 79–107) were highly conserved and showed a very little nucleotide variations. All the sequenced isolates showed serine at amino acid position 202. The RNA editing targets of the anti-genomic HDV RNA (nt1012) and its corresponding genomic RNA (nt 580) showed nucleotides A and C, respectively. CONCLUSIONS: The low seroprevalence and viraemic rates of HDV in particular during HIV-confection might be highly affected by HBV drug resistance selected HBsAg mutant variants in this setting, although HDV-1 sequences analysis revealed clade homogeneity and highly conserved structural and functional domains. Thus, the potential role of HBV drug resistance associated polymerase mutations and concomitant HBsAg protein variability on HDV viral assembly, secretion and infectivity needs further investigation.