Natural selection results in conservation of HIV-1 integrase activity despite sequence variability

Background: Integration of the HIV genome by integrase is absolutely requir ed for productive infection. Objective: To determine the role of natural selection on HIV integrase biol ogy. Design: To study the activities of HIV integrases from a limited panel of N orth American clinical isolates from HIV-infected patients and to compare t hese proteins with integrases from two laboratory adapted reference strains (HIVIIIRF and HIVNL4-3) Methods: HIV was isolated and the particle-associated RNA was reverse trans cribed and sequenced. Replication kinetics of molecularly cloned viruses co ntaining each variant integrase were studied in tissue culture. The mutant integrase proteins were expressed, purified and specific activities of the enzymes were derived for both 3' end-processing and disintegration reaction s. Results: Despite 3-5% variability in integrase at the amino acid level, vir uses showed no statistically significant differences in growth kinetics com pared with the reference HIVNL4-3 virus and only minor differences were obs erved in 3' end-processing and disintegration activities. All integrase pro teins demonstrated similar sensitivity to an integrase inhibitor L-chicoric acid. Conclusions: These results demonstrate that integrase genes derived from HI V-infected individuals can differ from reference sequences but these mutati ons do not result in loss of function, including susceptibility to an integ rase inhibitor; therefore, integrase remains an attractive target for antiv iral drug design, as mutability appears to be restricted by function. (C) 2 001 Lippincott Williams & Wilkins.