Combination of two pathways involved in raltegravir resistance confers dolutegravir resistance

OBJECTIVES: HIV-1 integration can be efficiently inhibited by strand-transfer inhibitors such as raltegravir, elvitegravir or dolutegravir. Three pathways conferring raltegravir/elvitegravir cross-resistance (involving integrase residues Q148, N155 and Y143) were identified. Dolutegravir, belonging to the second generation of strand-transfer compounds, inhibits the Y143 and N155 pathways, but is less efficient at inhibiting the Q148 pathway. The aim of this study was to characterize the combination of two pathways involved in raltegravir resistance described in one patient failing a dolutegravir regimen for their propensity to confer dolutegravir resistance. METHODS: In this study, a patient first failing a regimen including raltegravir was treated with dolutegravir and showed an increase in viruses carrying a combination of two pathways (N155 and Q148). Impacts of these mutations on integrase activity and resistance to strand-transfer inhibitors were characterized using both in vitro and virological assays. RESULTS: Our data showed that the combination of N155H, G140S and Q148H mutations led to strong resistance to dolutegravir. CONCLUSIONS: Combination of N155H, G140S and Q148H mutations originating from two distinct resistance pathways to raltegravir or elvitegravir led to a high level of dolutegravir resistance. Due to its high genetic barrier of resistance, it would be reasonable to use dolutegravir in first-line therapy before emergence of raltegravir or elvitegravir resistance.