17th International HIV Drug Resistance Workshop 10-14 June 2008, Sitges, Spain

RALTEGRAVIR RESISTANCE MUTATIONS AFFECT STRONGLY THE INTEGRASE ACTIVITIES AND THE REPLICATIVE CAPACITY OF VIRUSES HARBOURING SUCH MUTATIONS

Antivir Ther. 2008; 13(Suppl. 3):A19 (abstract no. 17)

AG Marcelin¹, I Malet¹, O Delelis², MA Valantin³, B Montes⁴, L Tchertanov², C Soulie¹, M Wirden¹, G Peytavin¹, J Reynes⁴, C Katlama³, JF Mouscadet² and V Calvez^1
1Laboratoire de Virologie, Hôpital Pitié-Salpêtrière, Paris, France; ²LBPA, CNRS, Ecole Normale Supérieure de Cachan, France; ³Service des Maladies Infectieuses, Hôpital Pitié-Salpêtrière, Paris, France; ⁴Pole Infectiologie, CHU de Montpellier, Montpellier, France

BACKGROUND: Raltegravir (MK-0518) is a potent inhibitor of HIV integrase (IN) and is clinically effective against viruses resistant to other antiretroviral classes. However, it can select mutations in HIV IN gene. It was demonstrated that most of these mutations altered both 3′-processing and strand transfer activities of IN. The aim of this study was to evaluate in vitro the effect of some of these mutations on the replicative capacity (RC) of mutated viruses.

METHODS: The two most prevalent profiles of raltegravir mutations were studied (N155H and G140S+Q148H). The entire IN genes (288 amino acids) from plasma samples corresponding to baseline (before raltegravir treatment) and to failure to raltegravir with IN mutations were amplified. These PCR products were cloned into a plasmid pNL4-3 deleted for IN gene. Recombinant viruses were obtained after plasmid transfection. The production of recombinant viruses was measured using AgP24 quantification up to 22 days.

RESULTS: In vitro, there were strong differences of virus production comparing recombinant viruses harbouring baseline IN (wild type) and mutated IN with N155H or G140S+Q148H mutations. At days 5, 10 and 22, the Ag P24 quantification was 7.10³ pg/ml versus 6.10² pg/ml, 2.10⁵ pg/ml versus 10³ pg/ml and 2.10⁶ pg/ml versus 10³ pg/ml for the wild type versus mutant viruses, respectively. Thus, the kinetics of replication and the total amount of produced viruses are strongly decreased in viruses with raltegravir resistance mutations. However, in vivo, patients harbouring viruses with these raltegravir mutations showed HIV viral load rebound corresponding to baseline values.

CONCLUSIONS: These results show that recombinant viruses with raltegravir resistance mutations have a very low RC. This is in accordance with biochemical results showing that these mutated IN have both 3′-processing and strand transfer altered activities and with the high difficulty to select such mutations using in vitro passages under raltegravir progressive pressure. Discrepancy between in vitro low RC and in vivo high level of HIV viral load rebound after selection of raltegravir mutations raises the question of other genetic determinants located outside of the IN gene that could be needed to get failure and resistance to raltegravir.

2008-06-10
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