Molecular characterization of hepatitis B virus (HBV) isolated from a pediatric case of acute lymphoid leukemia, with a delayed response to antiviral treatment: a case report.

BACKGROUND: Tenofovir disoproxil fumarate (TDF) is effectively used as the first-line antiviral for chronic hepatitis B virus (HBV) infection in adults and children older than 12 years. To date, no confirmed case of virologic breakthrough (VBT) in a pediatric case has been reported. CASE PRESENTATION: Here we describe a case of a 5-year old, asymptomatically infected with HBV infection two months after chemotherapy for precursor B acute lymphoblastic leukemia (ALL). Although the 5-year old male is South African, his family originated from Guinea. At the end of the one-year follow-up, the infection progressed to chronic HBV infection, with a high viral load. At 36 weeks (8 months) post-treatment with lamivudine (LAM), there was a partial virologic response (PVR) and after 61 weeks (14 months), he was switched to TDF rescue monotherapy. Even with TDF treatment, he still experienced VBT and subsequent PVR. The full-length genome of HBV isolated 78 weeks after the switch to rescue TDF monotherapy was sequenced and belonged to genotype E. In addition to the LAM mutations (rtS256G and rtM267L), missense mutations in B-cell, T-cell, HLA class I and II-restricted epitopes emerged, which were to evade and escape host surveillance, leading to delayed viral clearance, persistence and disease progression. Two further events of VBT occurred between weeks 113 and 141 of TDF rescue-therapy. Viral loads and liver enzymes are normalizing progressively with long-term therapy. CONCLUSION: Although the host immune reconstitution may be delayed, prolonged TDF treatment was effective in treating this pediatric case of HBV infection with VBT and PVR.

Hepatitis B virus immunity prior to and after administration of a 'booster' dose of vaccine among health-care students at a South African university.

Background: Health-care students (HCSs) are at risk of occupational exposure to hepatitis B virus (HBV) infection despite an effective hepatitis B vaccine (HepB) being available. The majority of current HCSs are born after HepB was introduced into the South African Expanded Programme on Immunisation in 1995. Thus, it is assumed that having received HepB in infancy, a single 'booster' dose would suffice. This study aimed to investigate HBV immunity prior to and after administration of a HepB 'booster' dose. Methods: Hepatitis B surface antibody (anti-HBs) levels were determined in first year HCSs at the University of the Witwatersrand, before and after receiving the 'booster'. Participant demographics and HepB history were captured using a structured questionnaire. Results: Before receiving the 'booster', 56% (101/180) had anti-HBs < 10 mIU/mL and were non-immune. A further 35% had anti-HBs levels of 10 - 99 mIU/mL, and 9% had ≥100 mIU/mL. <30% of HCSs self-reported completion of a three-dose primary series, which was significantly associated with higher baseline anti-HBs levels compared to those with a partial schedule (p = 0.045). Following vaccination, 39% (71/180) returned for follow-up with a significant median (IQR) increase of 476 (151 - 966) mIU/mL (p < 0.001). Of the 45 students who had non-immune baseline levels, 73% (33/45) responded with ≥100 mIU/mL, 16% (7/45) with 10 - 99 mIU/mL and 11% (5/45) remained non-immune. Levels of ≥100 mIU/mL were achieved by 100% of students with baseline levels ≥10 mIU/mL (n = 26). Conclusion: More than half of the HCSs were not immune to HBV prior to receiving the recommended 'booster' vaccine. Following vaccination, 7% (5/71) remained unprotected. This study highlights that in the absence of vaccination records and without confirming the immune status of HCSs, it cannot be assumed that HCSs will be protected following a 'booster'. Policy reform and inclusion of serological tests for immunity prior to HCSs initiating clinical exposure are recommended.

Frequent detection of hepatitis B virus variants associated with lamivudine resistance in treated South African patients infected chronically with different HBV genotypes.

This retrospective study investigated and characterized the YMDD motif of the hepatitis B virus (HBV) reverse transcriptase (RT) gene, in sequential samples of 17 South African patients with chronic hepatitis B infection on lamivudine treatment. The profile of HBV genotypes as well as the genetic variability of pre-core (pre-C) and basal core promoter regions (BCP) were also determined in these patients. Mutations within the RT gene were determined by direct sequencing using SpectruMedix SCE 2410 genetic analyzer and INNO-LiPA HBV DR (Innogenetics), while the genetic variability of the pre-C/BCP and surface gene were determined by direct sequencing only. HBV genotypes were determined by analysis of the surface, core and RT genes using a web-based genotyping tool (NCBI). HBV DNA was quantified using Cobas Amplicor HBV Monitor assay (Roche Diagnostics). Of the 17 patients, 13 (76.5%) carried YMDD mutations: 7 with rtM204I (2 HBeAg-positive and 5 HBeAg-negative) and 6 with rtM204V (4 HBeAg-positive and 2 HBeAg-negative). Of the 13 patients with resistant HBV strains, 8 (61.5%) carried genotype A, 3 (23%) genotype B, and 2 (15.3%) genotype C. Overall, only 5 of 13 (38%) patients with YMDD mutations experienced genotypic viral drug resistance and treatment failure. Of the 17 patients, 3 carried both pre-C (G1896A) and BCP (A1762T/G1764A) mutants, 1 pre-C only and 1 BCP only. This study demonstrated frequent detection of mutations associated with lamivudine-resistance in therapy-experienced South African patients infected chronically with different HBV genotypes, and confirmed that these mutations are not always accompanied by clinical relapse.

Mutations associated with lamivudine-resistance in therapy-naïve hepatitis B virus (HBV) infected patients with and without HIV co-infection: implications for antiretroviral therapy in HBV and HIV co-infected South African patients.

This was an exploratory study to investigate lamivudine-resistant hepatitis B virus (HBV) strains in selected lamivudine-naïve HBV carriers with and without human immunodeficiency virus (HIV) co-infection in South African patients. Thirty-five lamivudine-naïve HBV infected patients with or without HIV co-infection were studied: 15 chronic HBV mono-infected patients and 20 HBV-HIV co-infected patients. The latter group was further sub-divided into 13 occult HBV (HBsAg-negative) and 7 overt HBV (HBsAg- positive) patients. HBsAg, anti-HBs, anti-HBc, and anti-HIV 1/2 were determined as part of routine diagnosis using Axsym assays (Abbott Laboratories, North Chicago, IL). Serum samples were PCR amplified with HBV reverse transcriptase (RT) primers, followed by direct sequencing across the tyrosine-methionine-aspartate-aspartate (YMDD) motif of the major catalytic region in the C domain of the HBV RT enzyme. HBV viral load was performed with Amplicor HBV Monitor test v2.0 (Roche Diagnostics, Penzberg, Germany). HBV lamivudine-resistant strains were detected in 3 of 15 mono-infected chronic hepatitis B patients and 10 of 20 HBV-HIV co-infected patients. To the best of our knowledge, this constitutes the first report of HBV lamivudine-resistant strains in therapy-naïve HBV-HIV co-infected patients. The HBV viral loads for mono-infected and co-infected patients ranged from 3.32 x 10(2) to 3.82 x 10(7) and <200 to 4.40 x 10(3) copies/ml, respectively. It remains to be seen whether such pre-existing antiviral mutations could result in widespread emergence of HBV resistant strains when lamivudine-containing highly active antiretroviral (ARV) treatment (HAART) regimens become widely applied in South Africa, as this is likely to have potential implications in the management of HBV-HIV co-infected patients.