Natural variation of HIV-1 group M integrase: implications for a new class of antiretroviral inhibitors

Abstract

HIV-1 integrase is the third enzymatic target of antiretroviral (ARV) therapy. However, few data have been published on the distribution of naturally occurring amino acid variation in this enzyme. We therefore characterized the distribution of integrase variants among more than 1,800 published group M HIV-1 isolates from more than 1,500 integrase inhibitor (INI)-naïve individuals. Polymorphism rates equal or above 0.5% were found for 34% of the central core domain positions, 42% of the C-terminal domain positions, and 50% of the N-terminal domain positions. Among 727 ARV-naïve individuals in whom the complete pol gene was sequenced, integrase displayed significantly decreased inter- and intra-subtype diversity and a lower Shannon's entropy than protease or RT. All primary INI-resistance mutations with the exception of E157Q--which was present in 1.1% of sequences--were nonpolymorphic. Several accessory INI-resistance mutations including L74M, T97A, V151I, G163R, and S230N were also polymorphic with polymorphism rates ranging between 0.5% to 2.0%.

Figure 1

Distribution of variants among group M HIV-1 integrase sequences. The consensus subtype B sequence is shown at the top of each 40 amino acid section. Beneath the consensus B sequence is the number of annotated sequences containing an unambiguous amino acid at the indicated position with the number of such sequence ranging from 1183 to 1288. All variants reported at a level of ≥ 0.5% of sequences are indicated. The central core domain residues are surrounded by grey shading. The signature HHCC zinc-binding motif in the N-terminal domain and the DDE active site residues in the central core domain are indicated by boxes. Positions at which primary INI-resistance mutations for raltegravir and elvitegravir have been reported are indicated by "*". Positions at which accessory INI-resistance mutations for raltegravir and elvitegravir have been reported are indicated by "+". Positions at which INI-resistance mutations for other inhibitors have been reported are indicated by ".".

Figure 2

Level of Shannon's entropy across the 99 amino acids of protease, 560 amino acids of RT, and 288 amino acids of integrase for 727 isolates from the six subtypes for which the most isolates were available. A dotted line is drawn at an entropy level of 0.5 bits – a level at which the correct amino acid at a position could be predicted with nearly 90% certain.