Prevalence of primary resistance to antivirals used in the treatment of hepatitis B among treatment-naïve patients with chronic hepatitis B

Author(s)

Michele Soares Gomes Gouvêa

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2014-06-27

Examining board members

João Renato Rebello Pinho; Maria Lúcia Cardoso Gomes Ferraz; Paulo Roberto Abrão Ferreira; Luiz Fernando Onuchic

• Advisor: João Renato Rebello Pinho; Maria Cassia Jacintho Mendes Corrêa

Abstract

The main aim of this study was to evaluate the frequency of HBV strains harboring mutations that confer resistance to nucleos(t)ide analogues (NA) used to hepatitis B treatment among treatment-naïve patients with chronic hepatitis B from different Brazilian region. Furthermore, we evaluated the presence of mutations that alter the antigenicity of HBsAg causing anti-HBs escape; mutations in genes pre-core/core and the association of different subgenotypes with the mutations detected and demographic and laboratory characteristics of the patients. Serum samples from 779 treatment-naïve patients with chronic HBV infection were included in this study. The samples were collected between 2006 to 2011 and the patients were from the following states: Pará, Maranhão, Bahia, Minas Gerais, São Paulo, Paraná and Rio Grande do Sul. HBV DNA was extracted from serum samples using the QIAamp DNA Blood Mini Kit (Qiagen) and amplification of S/polymerase (S/Pol) and pre-core/core (PCC) regions were performed by nested PCR. The amplified PCR products were submitted to sequencing in an automatic DNA sequencer (ABI 3500). The sequences obtained were analyzed to classify HBV genotypes/subgenotypes and to analyze the presence of mutations. S/Pol region was amplified and sequenced successfully from 702 samples, which were included in this study. Among these 702 samples, seven genotypes and 12 subgenotypes have been identified. HBV subgenotype A1 was the most frequent (63.7%, 447/702), followed by HBV/D3 (14.5%; 102/ 702). The remaining genotypes and subgenotypes identified and their frequencies were as follows: A2 (3.3%, 23/702), A3 (0.1%, 1/702), B1 (0.1%, 1/702), B2 (0.1%, 1/702), C2 (0.9%, 6/702), D1 (0.9%, 6/702), D2 (4.6%, 32/702), D4 (5.1%, 36/702), D unclassified subgenotype (0.7%, 5/702), E (0.6%, 4/702), F2a (4.6%, 32/702), F4 (0.4%, 3/702), and G (0.4%, 3/702). HBV strains harboring mutations conferring NA resistance alone (rtS202G, rtM204V/I, rtA194T, rtM250I, rtA181T/S, rtT184S) or combined with compensatory mutations (rtL80I, rtV173L, rtL180M, rtV207I) were identified in 1.6% (11/702) of the patients. Isolates harboring mutations potentially associated with adefovir resistance (rtS85A, rtL217R, rtI233V, rtN238T, rtN238D, rtN248H, rtV214A, and rtQ215S) or entecavir resistance (rtS219A) were identified in 7.7% (54/702) and 2.6% (16/702) of the patients, respectively. HBV with HBsAg mutations previous related with anti-HBs escape or impaired secretion were detected in 8.5% (57/702) of the samples. Statistical analyzes were performed to assess the correlation between the more frequent HBV subgenotypes found in this study (A1, A2, D1, D2, D3, D4 and F2a ) and mutations in PCC genes. Among the mutations found in these genes that were associated with reduction or failure in HBeAg synthesis, A1762T/T1764A mutations were associated to subgenotypes A1 and F2a; G1862T and mutations at positions 1809-1812 to subgenotype A1; G1896A and/or G1899A to subgenotypes D2, D3 and D4. Other mutations associated with disease progression were found: C1766T and T1768A mutations were associated with subgenotypes A1 and F2a, and the G1888A mutation was associated with subgenotype A1. HBV strains circulating in different Brazilian regions studied showed high genetic variability and distribution of genotypes and subgenotypes reflects the population formation history of each region and the occurrence of recent events of migration. The frequency of HBV strains with NA resistance mutations circulating among treatment-naive patients in different regions of Brazil studied is low and the profile of mutations that confer total resistance to lamivudine and partial resistance to entecavir is more widespread. Although some cases of infection have been detected with HBV strains carrying mutations associated with major impact on the antigenicity of this protein, all samples had detectable HBsAg. HBeAg negative cases were more frequent in the studied population, regardless of subgenotype. Different pattern of mutations were found in PCC genes, suggesting that different mechanisms are involved in HBeAg negativity for each subgenotype (AU)

• FAPESP's process: 10/50081-9 - Prevalence of primary resistance to antiviral therapy against hepatitis B in patients with chronic hepatitis B virus infection and not submitted to treatment
• Grantee: Michele Soares Gomes Gouvêa
• Support Opportunities: Scholarships in Brazil - Doctorate