Hepatitis B virus (HBV) infection remains a major global health problem. Ten HBV genotypes have been identified and several studies have shown correlations between the actual HBV genotype and the course and effectiveness of infection treatment. HBV can be transmitted through transfusion of infected blood. With implementation of nucleic acid amplification technology testing (NAT) of all blood donors for the presence of HBV DNA, the possibility of viral transmission by blood components and products has significantly decreased. However, diagnostics of occult HBV infection (OBI) is still an important challenge in transfusion medicine.
In our study, ultracentrifugation was implemented in the HBV genotyping procedure. We performed ultracentrifugation on 24 plasma samples of 24 Slovenian blood donors which were diagnosed with OBI. Following ultracentrifugation, the resulting pellets were resuspended, HBV DNA was isolated and viral genotypes were successfully determined in all 24 samples.
As stated, HBV genotype was identified in all 24 (100 %) blood donors whose plasma samples were ultracentrifuged prior to DNA isolation and in only 5 (21 %) out of the same 24 plasma samples which were not ultracentrifuged before DNA isolation. HBV genotypes were identified in 21 out of 24 samples (88 %), where, after ultracentrifugation, the resulting pellets were resuspended in water, and in 15 out of 24 (63 %) where they were resuspended in lysis buffer. Our results revealed that the D genotype is predominant in Slovenian blood donors with OBI, as this genotype was identified in 21 out of 24 blood donors (88 %). The A genotype was detected in 2 blood donors (8 %), while in the remaining 1 (4 %), a mixed infection with the A and D genotypes was identified.
With the implementation of ultracentrifugation we improved the sensitivity of real-time polymerase chain reaction (qPCR) used for HBV genotyping. This is a step closer to even safer use of blood and blood components. However, laboratory diagnostics of HBV in samples with extremely low viral load (0,15 IU/ml) still remains a challenge for future.