Naslov
CHARACTERIZATION OF HEPATITIS B VIRUS STRAINS INFECTING BLOOD DONORS WITH HIGH HBSAG LEVELS AND INCONSISTENTLY DETECTABLE HBV DNA: IMPLICATIONS FOR BLOOD SAFETY AND SCREENING POLICY

Autori
D Candotti, M Vermeulen, A Kopacz, M Miletic, A Saville, P Grabarczyk, C Niederhauser, L Boizeau and S Laperche

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Vox Sanguinis 114 (Suppl.1), 5-240 / - , 2019, 28-28

Skup
29th Regional Congress of the ISBT

Mjesto i datum
Basel, Švicarska, 22.06.2019. - 26.06.2019

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
blood donors ; hepatitis B ; HBsAg high levels and HBV DNA inconsistently detectable

Sažetak
Background: The implementation of nucleic acid testing (NAT) and the development of sensitive and specific serologic assays to detect HBsAg and anti-HBc antibodies significantly reduced the risk of HBV transfusion-transmission. The apparent redundant testing for two direct viral markers prompted debates on maintaining HBsAg screening, particularly in low endemic countries where blood donations are screened for anti-HBc. However, frequencies of 2–20% of HBsAg-confirmed positive/NAT negative donations have been reported depending on the sensitivity limit of the molecular assays used. The nature of this discrepancy between HBsAg and DNA remains largely unknown and it is essential to evaluate any potential negative impact on blood safety before considering removing HBsAg testing. Aims: The prevalence in blood donors and the molecular mechanisms responsible for a persistent undetectable or barely detectable level of viral replication in the presence of a sustained HBsAg production were investigated in a collaborative study including five laboratories/blood centers in Europe and South Africa. Discrepancy between viral DNA and HBsAg levels suggested the presence of mutations that may negatively affect HBV replication and/or infectious viral particle production. Methods: Donor samples from France, South Africa, Poland, and Croatia were selected for having HBsAg levels ≥ 100 IU/ml and being ID-NAT (Procleix-Ultrio PlusTM [95% LOD: 3 IU/ml]) non-reactive/non-repeatable reactive (NR/NRR) with undetectable viral load (VL) or < 6 IU/ml (n = 44) or NAT repeat reactive (RR) with VL < 6 IU/ml (n = 32). French samples initially tested NAT NR/NRR with Procleix- Ultrio (LOD 95%: 11 IU/ml) were retested with Ultrio Plus prior inclusion in the study. HBV DNA load was quantified (Cobas TaqMan HBV [LOQ: 6 IU/ml]). HBV DNA was purified from 5 to 12 ml of plasma after ultracentrifugation. The whole HBV genome, Pre-S/S, PreCore/Core and BCP regions were amplified and sequenced. Results: Following viral concentration, HBV DNA presence was confirmed in 79% of all samples with undetectable or VL < 6 IU/ml. HBV genotypes were A1 (33.3%), A2 (18.4%), A3 (3.3%), B (3.3%), C (1.7%), D (25%), and E (15%). All samples were anti- HBc positive and 73% of Ultrio-negative samples tested positive with Ultrio Plus. Unusual 1–2 nt insertions/deletions identified in BCP regulatory elements (TATA boxes, pgInr, epsilon domain) suggest altered viral replication. Amino acid substitutions (n = 16) or deletions (n = 4) at positions reported involved in nucleocapsid formation, particle envelopment and virion formation were observed in the core protein of 30 samples. The replicative properties of the BCP and core variants are currently evaluated in vitro as a surrogate model for direct infectivity testing. Preliminary results indicate that the variants tested so far have replicative capabilities similar to those of control viruses. Analysis of Pol, S, and HBx proteins is ongoing. Summary/Conclusions: These data confirmed the presence of extremely low level of circulating DNA-containing viral particles in ID-NAT non-reactive or nonrepeated reactive blood donations with concomitant high HBsAg levels and anti-HBc reactivity. Despite the presence of mutations in the viral genomes potentially affecting virion production, preliminary data indicate that some of the viruses in plasma retain the ability to replicate in vitro and to constitute a potential infectious risk.

Izvorni jezik
Engleski

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