Session 66Poster Presentations New Antiretrovirals Session Day and Time: Tuesday 1:30 - 3:30 pm Room: Hall A
559 Development of a Novel Fusion Inhibitor, SC34EK: High Susceptibility to HIV Variants Resistant to Fusion Inhibitors In Vitro E. Kodama*, D. Nameki, M. Ikeuchi, A. Otaka, H. Tamamura, N. Fujii, M. Matsuoka Kyoto Univ, Japan
Background: Peptide-based HIV fusion inhibitors derived from gp41 block entry of various HIV strains. To elucidate the inhibitory mechanism in detail, induction and analyses of the resistant variants were performed. Susceptibility of the synthesized peptides to the resistant variants was also investigated.
Methods: Fusion inhibitors-resistant HIV variants were selected in vitro by propagating HIV-1NL43 in the increasing doses of the peptides, N36 derived from the gp41 N-terminus heptad repeat (N-HR) and C34 derived from the C-HR. C34 derivatives were synthesized and were examined for their anti-HIV activities. Various recombinant HIV clones (HIV-1NL43 background) were generated with site directed mutagenesis. Antiviral activity was determined using HeLa CD4/LTR-beta-Gal cells.
Results: HIV variants selected against C34 showed reduced susceptibility to not only C34 but also T-20 and SC34 (C34 derivative). Sequence analyses of the gp41 coding region revealed that HIV acquired several mutations (D37G/I38K/N127K/L205I) in the gp41 coding region. The resistant variants containing I38T or I38K mutations showed reduced susceptibility to T-20 (13- and 212-fold, respectively) and C34 (11- and 13-fold, respectively). Other mutations e.g., N127K and L205I, exert little effect on the peptide susceptibility. However, N127K mutation combined with I38K enhanced the resistance to C34 (13- to 28-fold) and SC34 (10- to 60-fold). N127K mutation was also observed during selection with N36 (2-fold resistance to N36). G37S/V39M variant which was reported as a resistant variant to T-20 in vitro showed moderate resistance against T-20, C34 and SC34 (5-, 8- and 5-fold, respectively). In contrast, an SC34EK, which is a 69-fold potent inhibitor compared to T-20, maintained its anti-HIV activity against such resistant variants.
Conclusions: I38 amino acid substitution is considered as a key mutation for resistance to peptide inhibitors derived from C-HR. Other substitutions observed in the gp41 coding region, e.g., D37G and L205I, appear to serve as a secondary mutation that improves the reduced replication fitness. These results indicate that HIV may acquire cross resistance to such peptide inhibitors, whereas SC34EK with amino acid substitutions in C34 can suppress replication of C34 resistant variants without cross resistance.