AIM: To study the hepatitis B virus(HBV) and hepatitis D virus(HDV) replication interferences in patients with chronic hepatitis delta infected with different HBV genotypes.METHODS: We conducted a transversal study including 68 chronic hepatitis delta(CHD)(37 HIVpositive) patients and a control group of 49 chronic hepatitis B(CHB)(22 HIV-positive) patients. In addition, a dynamic follow-up was performed in 16 CHD patients. In all the samples, the surface antigen of hepatitis B(HBs Ag) serum titers were analyzed with the Monolisa HBs Ag Ultra system(Bio-Rad), using as quantification standard a serial dilution curve of an international HBs Ag standard. Serum HBV-DNA titers were analyzed using the Roche Cobas Taq Man(Roche, Barcelona, Spain), and the serum HDV-RNA using an in-house real-time q RT-PCR method, with Taq Man probes. HBV genotype was determined with the line immunoassay Li PA HBV genotyping system(Innogenetics, Ghent, Belgium). In those patients negative for Li PA assay, a nested PCR method of complete HBs Ag coding region, followed by sequence analysis was applied.RESULTS: No differences in the HBV-DNA levels were found in CHB patients infected with different HBV genotypes. However, in CHD patients the HBV-DNA levels were lower in those infected with HBV-A than in those with HBV-D, both in HIV negative [median(IQR): 1.25(1.00-1.35) vs 2.95(2.07-3.93) log10(copies/m L), P = 0.013] and HIV positive patients [2.63(1.24-2.69) vs 7.25(4.61-7.55) log10(copies/m L), P < 0.001]. This was confirmed in the dynamic study of the HBV/HDV patients. These differences induce an under-estimation of HBV-A incidence in patients with CHD analyzed with Li PA assay. Finally, the HBs Ag titers reflected no significant differences in CHD patients infected with HBV-A or D.CONCLUSION: Viral replication interference between HBV and HDV is HBV-genotype dependent, and more evident in patients infected with HBV-genotype A, than with HBV-D or E. AIM: To study the hepatitis B virus (HBV) and hepatitis D virus (HDV) replication interferences in patients with chronic hepatitis delta infected with different HBV genotypes. METHODS: We conducted a transversal study including 68 chronic hepatitis delta (CHD) (37 HIV positive ) patients and a control group of 49 chronic hepatitis B (CHB) (22 HIV-positive) patients. In addition, a dynamic follow-up was performed in 16 CHD patients. In all the samples, the surface antigen of hepatitis B Ag) serum titers were analyzed with the Monolisa HBs Ag Ultra system (Bio-Rad) using a serial dilution curve of an international HBs Ag standard. Serum HBV-DNA titers were analyzed using the Roche Cobas Taq Man (Roche, Barcelona, ​​Spain), and the serum HDV-RNA using an in-house real-time q RT-PCR method with Taq Man probes. HBV genotype was determined with the line immunoassay Li PA HBV genotyping system (Innogenetics, Ghent, Belgium) In those patients negative for Li PA assay, a nes PCR products of the HBV-DNA levels were found in CHB patients infected with different HBV genotypes. However, in CHD patients the HBV-DNA levels were lower in those infected with HBV-A than in those with HBV-D, both in HIV negative [median (IQR): 1.25 (1.00-1.35) vs 2.95 (2.07-3.93) loglO copies / ml, P = 0.013] and HIV positive patients [2.63 (1.24-2.69) vs 7.25 (4.61-7.55) log10 (copies / mL), P <0.001]. This was confirmed in the dynamic study of the HBV / HDV patients. These differences induce an under -estimation of HBV-A incidence in patients with CHD analyzed with Li PA assay. Finally, the HBs Ag titers were detected no significant differences in CHD patients infected with HBV-A or D. CONCLUSION: Viral replication interference between HBV and HDV is HBV- genotype dependent, and more evident in patients infected with HBV-genotype A, than with HBV-D or E.