br Discussion By using ultra deep sequencing we

Discussion By using ultra-deep sequencing, we conducted a thorough assessment of HCV-NS3 protease variants in chronic PI-naïve patients infected with HCV-1a and HCV-1b under telaprevir-based triple therapy at baseline and after 4weeks of treatment. Several synonymous and non-synonymous substitutions, including those at very low frequencies, were detected for both genotypes at both time points. However, there was no correspondence between resistance variants detected at baseline and at 4weeks. Our results showed that triple therapy was effective for 11 patients (69%) since they showed SVR or had undetected HCV RNA level at 48weeks of treatment (final sustained response will be available at 6months after the end of treatment). The observation that resistance mutations at baseline were not identified at 4weeks is in Kifunensine to previous suggestions that the widespread natural occurrence of HCV-resistant variants could explain the detection of resistance variants following PI monotherapy [16]. Non-synonymous resistance variants were detected at baseline in the peripheral blood of all patients, supporting the existence of circulating viral populations. The improved detection capacity of the NGS method used here may explain the observation of more highly prevalent and variable mutations at baseline in the peripheral blood than those detected by previous studies in Brazil [11], [15], [24], [25] and other countries [12], [18], [26], [27]. Our results therefore confirm and expand previous research, providing a comprehensive databank of non-synonymous HCV-NS3 variants induced by short-term therapy, which can be of potential importance for future drug resistance association studies involving approved and newly developed PI agents. The predictive potential of baseline resistance variants remains controversial. Some authors still support routine baseline resistance mutation detection before PI therapy [18], while others report that resistant variants emerging during PI therapy are the same as those identified at baseline [19], [20]. However, most studies have investigated emerging resistance mutations late in treatment or post-treatment, i.e., at the time of viral load re-elevation [19]. Although in our study only six patients had detectable HCV RNA level under treatment, resistance variants were detected already at 4weeks, yielding early virus-diversity information that could be important for understanding viral-variant dynamics and guiding treatment. Recent studies showed no association between the presence of resistance mutations before treatment and treatment outcome in samples of non-cirrhotic patients [7], [21]. Our data potentially support and expand the previous observation to patients with severe liver fibrosis and cirrhosis since emerging resistance variants at 4weeks were different from those present at baseline (see also [28]). On the other hand, recent study suggested that baseline variants profile could be predictive of outcome when accompanied by previous failure to classical PEG-IFN/RBV treatment [22]. Moreover, since resistance variants identified early in treatment were not concordant with baseline profile, the predictive prognostic power of those therapy-induced substitutions should be replicate in other cohorts to further support our interpretation.
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Acknowledgments We thank Claudio Nunes Pereira, César Félix Schmidt, and Fabianne Santolin de Aguiar for their technical support. This work was supported by grants from Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro—FAPERJ; Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq; and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES.
Introduction The retroviral human immunodeficiency virus type-1 (HIV-1), is a causative agent of acquired immunodeficiency syndrome (AIDS). One important enzyme necessary for the maturation and infectivity of this virus is the aspartic protease, HIV-1 protease (HIV-1 PR), which functions in the dimeric form composed of monomers of 99 amino acids. Thus, HIV-1 PR is an important target of searches for anti-HIV drugs.