Deep sequencing analysis of hepatitis B virus in patients with incomplete response to tenofovir alafenamide fumarate treatment.

BACKGROUND

Tenofovir alafenamide fumarate (TAF) is one of the first-line treatments used to treat chronic hepatitis B patients; TAF has strong antiviral activity and a high barrier to resistance. Although virological breakthroughs in patients during TAF treatment are rare, patients with incomplete responses to TAF are occasionally observed.

AIM

To investigate responsible mutations in the reverse transcriptase region of hepatitis B virus (HBV) for TAF-incomplete responses.

METHODS

Thirteen chronic hepatitis B patients who received TAF monotherapy were included. A TAF-incomplete responder was defined as one who was continuously positive for HBV DNA over 2 years after TAF treatment initiation. The emergences of mutations in TAF-incomplete responders were evaluated before, one year after, and two years after treatment by deep sequencing of HBV DNA and RNA.

RESULTS

Two patients were continuously positive for HBV DNA over two years. The rtL269I mutation, one of the CYEI mutations linked to tenofovir resistance, was detected in both patients by direct sequencing. The deep sequencing analysis revealed that a combination of rtT118A and rtL220I mutations and the rtL269I mutation were predominantly detected in HBV DNA even when these mutations were barely detected in HBV RNA. This suggests a superior replication capability of the HBV variants with these mutations under TAF treatment.

CONCLUSION

The deep sequencing analysis of HBV DNA and RNA and comparing the detection rates of mutations were useful for estimating responsible mutations for TAF-incomplete responses. Such analysis is needed to evaluate the association between mutations that emerge during TAF treatment and incomplete responses to TAF.