ANALYSIS OF POL GENE HETEROGENEITY, VIRAL QUASI-SPECIES, AND DRUG-RESISTANCE IN INDIVIDUALS INFECTED WITH GROUP-O STRAINS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

Nucleotide sequences of the reverse transcriptase (RT) coding region h ave been compared in four new human immunodeficiency virus type 1 (HIV -1) group O isolates. Phylogenetic analysis of this pol region highlig hts a cluster of these four HIV-1 group O sequences with seven other g roup O isolates (5% intracluster nucleotide sequence diversity) simila r to clusters classified as subtypes in HIV-1 group M (an average of 4 .9% intrasubtype sequence diversity), Based on these analyses, this gr oup O cluster has been designated subtype A-O. A longitudinal study of a heterosexual couple infected with group O (ESP1 and ESP2) allowed a detailed analysis of RT sequences (amino acids 28 to 219). Directed e volution and a slightly higher mutation frequency was observed in the RT sequences of patient ESP2, treated with antiretroviral drugs, than that from time untreated patient ESP1. Antiretroviral treatment also s elected for specific substitutions, M184V and T215Y in the RT coding r egion, conferring resistance to 3'-dideoxy-3'-thiacytidine and zidovud ine, respectively. A Gly98 to Glu RT substitution identified in the tr eated patient suggests a possible reversion of a nonnucleoside PIT inh ibitor-resistant phenotype. Using RT clones from this longitudinal stu dy, both heteroduplex tracking assay and cloning-sequencing techniques were employed for an extensive genetic analysis of pol gene quasispec ies. Amino acid substitutions (i.e,, Phe-77 to Leu, Lys-101 to Glu, an d Val-106 tc, Iso) associated with antiretroviral resistance were iden tified in RT clones from HIV-1 group O-infected patients not subjected to drug therapy or treated with unrelated drugs. Finally, phylogeneti c relationships between RT clones of the treated ESP2 patient and thos e of the untreated ESPI patient show how drug pressure can direct evol ution of viral pol gene quasispecies independently of direct drug-resi stant substitutions.