Individual contributions of mutant protease and reverse transcriptase to viral infectivity, replication, and protein maturation of antiretroviral drug-resistant human immunodeficiency virus type 1

Human immunodeficiency virus type 1 (HIV-1) variants resistant to protease (PR) and reverse transcriptase (RT) inhibitors may display impaired infecti vity and replication capacity. The individual contributions of mutated HIV- 1 PR and RT to infectivity, replication, RT activity, and protein maturatio n therein referred to as "fitness") in recombinant viruses were investigate d by separately cloning PR, RT, and PR-RT cassettes from drug-resistant mut ant viral isolates into the wild-type NL4-3 background. Both mutant PR and RT contributed to measurable deficits in fitness of viral constructs. In pe ripheral blood mononuclear cells, replication rates (means +/- standard dev iations) of RT recombinants were 72.5% +/- 27.3% and replication rates of P R recombinants were 60.5% +/- 33.6% of the rates of NL4-3. PR mutant defici ts were enhanced in CEM T cells, with relative replication rates of PR reco mbinants decreasing to 15.8% +/- 23.5% of NL4-3 replication rates, Cloning of the cognate RT improved fitness of some PR mutant clones. For a multidru g-resistant virus transmitted through sexual contact, RT constructs display ed a marked infectivity and replication deficit and diminished packaging of Pol proteins (RT content in virions diminished by 56.3% +/- 10.7%, and int egrase content diminished by 23.3% +/- 18.4%), a novel mechanism for a decr eased-fitness phenotype, Despite the identified impairment of recombinant c lones, fitness of two of the three drug-resistant isolates was comparable t o that of wild-type, susceptible viruses, suggestive of extensive compensat ion by genomic regions away from PR and RT, Only limited reversion of mutat ed positions to wild-type amino acids was observed for the native isolates over 100 viral replication cycles in the absence of drug selective pressure . These data underscore the complex relationship between PR and RT adaptive changes and viral evolution in antiretroviral drug-resistant HIV-1.