Background:  We have tracked the prevalence of transmitted HIV-1 variants resistant to antiretroviral drugs since 1996.  During 2003-2004 we observed increasing rates of non-nucleoside reverse transcriptase inhibitor (NNRTI) -resistant transmissions, as well as an increasing trend in multi-drug-resistant transmissions. Here we present resistance data generated during 2005-2006 in our cohort of acute and early HIV-1 infected individuals.

Methods:  We identified 92 patients as having acute or recent HIV-1 infection based on laboratory data documenting infection within 1 year between January 2005 and September 2006. Plasma viral RNA was used for nucleotide sequence analysis of the protease and reverse transcriptase using the TRUGENE HIV-1 genotyping kit.  Drug-resistance mutations were characterized using the August 2006 International AIDS Society-USA consensus guidelines.  Changes in drug-resistant-conferring mutation frequencies were analyzed using the Fisher’s exact test.

Results:  We identified and studied 90 male patients and 2 female patients, all of whom reported a history of having sex with men. The prevalence of transmitted resistance during the 2005-2006 period was 14 of 92, (15.2%), a decrease from 27 of 112 (24.1%) during the period 2003-2004 (p = 0.20).  NNRTI resistance also decreased to 9 of 92 (9.8%) in 2005-2006 from 15 of 112 (13.4%) in 2003-2004 (p = 0.5). However, of the NNRTI-resistant viruses, 6 of 9 harbored the K103N mutation—6.5% of all patients versus 3 of 112 (2.7%) during the prior period (p = 0.18). Unlike the previous interval, transmission of variants harboring the M184V mutation was observed in 2 patients, both with multi-drug-resistant HIV-1. The total number of thymidine analog-associated mutations (TAM) decreased from 15 of 112 (13.4%) in 2003-2004 to 7 of 92 (7.6%) (p = 0.26), and the number of patients harboring major protease mutations also dropped from 8 of 112 (7.1%) to 2 of 92 (2.1%) (p = 0.12). Transmission of multi-drug-resistant HIV-1 decreased from 9.8% in 2003-2004 to 4.3% in 2005-2006 (p = 0.18). No K65R mutations were seen during this period, despite the increasing use of tenofovir-containing regimens.

Conclusions:  The transmission of drug resistant virus in this homogenous cohort is trending downward, possibly due to better adherence to current regimens in the local HIV-1-infected population. However, transmitted NNRTI-resistance continues at comparable rates, and the most common mutation identified is K103N. Initial treatment options for these individuals are affected, mainly depriving them of the now available 1-pill-once-daily option.