Methods
The two most prevalent profiles of raltegravir mutations were studied (N155H and G140S + Q148H). Recombinant viruses harbouring the mutations N155H, E92Q, G140S/Q148H were constructed by site directed mutagenesis. To study the influence of each mutation on the residues G140 and Q148, viruses harbouring these mutations were constructed. All these mutations were also introduced in a plasmid encoding proteins in order to obtain recombinant mutated IN.