423   Prevalence of Drug- Resistant HIV-1 Variants in Newly Infected Individuals during 1999- 2000.

V. Simon*¹, J. Vanderhoeven¹, A. Hurley¹, B. Ramratnam¹, D. Boden¹, M. Louie¹, R. Kost¹, K. Dawson², N. Parkin², J. P. Routy^3,5, R. P. Sekaly^4,5, and M. Markowitz¹.
¹Aaron Diamond AIDS Res. Ctr., New York, NY;²ViroLogic Inc., San Francisco, CA;³McGill Univ., Montreal, Canada;⁴Univ. of Montreal;⁵the AIEDRP Group, Montreal, Quebec, Canada.

Background:We have continued to track the prevalence of transmitted drug-resistant variants of HIV-1. Here we characterize 61 newly infected individuals (NIs) referred to the Aaron Diamond AIDS Research Center (New York City [NYC]) and recruited in Montreal, Canada during the period from April 1st 1999 to September 31st 2000.

Methods:Pre-treatment plasma samples were analyzed both by population sequencing of RT-PCR products and by phenotypic assay (PhenoSense, ViroLogic, CA).

Results:61 NIs were identified (55 NYC/6 Montreal, Canada; 29 NI in 1999/32 in 2000). To date 61 protease (PR) sequences, 59 RT sequences, and 49 phenotypic assays have been evaluated. Primary PR-resistance- conferring mutations (M46I, V82A/T, I84V, L90M) were detected in 4 cases (6.5%; 3 in 2000). In 2 viral variants, the PR gene revealed 2 or more primary mutations (MDR#1: M46I + L90M/MDR-2: V82A + I84V + L90M) and was associated with both NRTI- and NNRTI-resistance-conferring mutations. The genotype of MDR#3 showed L90M in PR in combination with the NNRTI-resistance-associated key mutation K103N in RT. Additionally we observed a high degree of polymorphisms in the PR gene: L63P/Q/C/S (56%; 34/61), V77I (26%; 16/61), I93L (21%; 13/61); M36I (15%; 9/61) and L10F/I (8%; 5/61). Isolated primary mutations in RT associated with a >10-fold-reduced susceptibility were observed in only one subject (K103N). Frequencies of resistance-conferring mutations in RT were: M41L (2/59), K70R (2/59), K103N (3/59), V179I (4/59), Y181C (1/ 59), T215Y (1/59), T215S/A (4/59), and K219Q/L (2/59). Overall prevalence (primary PR mutations and the RT mutations above mentioned) was 26% (16/61).

Conclusions:As compared to previous years (1995—98) we have documented an increasing prevalence of viruses harboring resistance-conferring amino acid substitutions (16% vs. 26%). Of note, 2 out of 3 individuals with MDR virus isolates were infected in 2000. Continued characterization of transmitted viruses is critical to achieve large enough numbers of observations to reach statistical significance.