Study of resistance mutations to treatment with direct action drugs in patients infected with hepatitis C virus genotype 3

Author(s)

Guilherme Rodrigues Fernandes Campos

• Document type: Doctoral Thesis
• Press: São José do Rio Preto. 2020-08-19.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2020-07-01
• Advisor: Paula Rahal; Cintia Bittar Oliva

Abstract

The HCV treatment with direct acting antivirals (DAAs) results in a sustained virological response (SVR) that varies according to the viral genotype. Among all genotypes, genotype 3 is the second most prevalent in Brazil and the one that presents the lowest SVR. It is responsible for almost 24% of infected cases in the country, and literature does not have enough data that can explain this lower response and higher treatment failure rate. Thus, the aim of this study was to analyze genotype 3 viruses circulating in Brazilian patients, under treatment with Daclatasvir (DCV) and/or Sofosbuvir (SOF), to observe resistance associated substitutions (RAS) already described in literature and to identify novel mutations that could confer resistance inside NS5A and NS5B, investigating the in vitro behavior of these substitutions. Among the patients included in this work, the relapse rate was 11.9%, where the treatment failure was related with many factors, and RAS presence was one of them. Described RAS were observed inside NS5A in the sites 30, 62 and 93, where the last one presented mutations only after drug administration, indicating a possible selective pressure. For NS5B, substitutions were detected in positions 159, 421 and 554, where only the first one was maintained after treatment. Regarding undescribed mutations, S98G showed promising data due to its high frequency in relapsing patients, before and after treatment. In vitro analysis revealed that S98G presents a compensatory effect on viral replication, with no resistance phenotype when isolated, but when present concomitantly with Y93H, led to an increasing on resistance to DCV. Using a brand new in vitro tool, based on cloning of NS5A domain I derived from clinical samples, described RAS and undescribed novel mutations were selected after DCV selective pressure. The results of this study enable the comprehension of viral behavior under DAA treatment, leading to a better understanding on the dynamics of RAS selection. These approaches enable the frequency mapping of already known RAS and the description of possible novel resistance associated mutations, designing safer treatment strategies to avoid treatment failure. (AU)

• FAPESP's process: 16/03807-0 - Study of resistance mutations to treatment with Directly Acting antivirals in patients infected with hepatitis C virus genotype 3
• Grantee: Guilherme Rodrigues Fernandes Campos
• Support Opportunities: Scholarships in Brazil - Doctorate