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  21st Conference on Retroviruses and
Opportunistic Infections
Boston, MA March 3 - 6, 2014
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Transmitted HIV Resistance Rate Close to 20% in Large Study of US MSM
  CROI 2014, March 3-6, 2014, Boston
Mark Mascolini
More than 17% of antiretroviral-naive men who have sex with men (MSM) in a large US study carried antiretroviral-resistant virus, according to a nationwide analysis by the Centers for Disease Control and Prevention (CDC) [1]. MSM under 30 years old had close to a 19% prevalence of transmitted resistant HIV.
MSM accounted for an estimated two thirds of new HIV infections in the United States in 2011, the CDC team observed. Condom-free sex largely accounts for the persistently high HIV incidence in US MSM. Antiretroviral-treated men with poorly controlled viral replication pose a risk of transmitting resistant HIV to sex partners when they have sex without condoms.
To get a better understanding of transmitted resistant HIV prevalence and patterns among MSM, CDC investigators analyzed data from the US National HIV Surveillance System, through which regions submit HIV case data, including demographics, transmission risk, and laboratory and clinical results. Some regions also conduct Molecular HIV Surveillance and HIV Incidence Surveillance, which respectively provide data on resistant virus and timing of newly diagnosed infections as recent or long-standing.
The CDC team analyzed HIV sequences in people newly diagnosed with HIV from 2008 through 2011 who had not taken antiretroviral therapy. The regions contributing were Los Angeles County, Colorado, Connecticut, Florida, Chicago, Louisiana, Michigan, New York City, South Carolina, Texas (excluding Houston), and Washington state. The researchers calculated prevalence ratios to compare resistance transmission prevalence between groups.
Prevalence of any transmitted resistance mutation in 2008-2011 measured 15.5% among 6091 HIV-positive people who were not MSM and 17.4% among 10,894 MSM studied. The rate in MSM was 12% higher than in non-MSM (prevalence ratio [PR] 1.12, 95% confidence interval 1.05 to 1.21). Among MSM, 9.0% of newly diagnosed infections involved nonnucleoside mutations, 6.6% nucleoside/nucleotide mutations, and 4.6% protease inhibitor mutations.
While 3083 newly diagnosed infections in MSM were judged recent, 7810 were judged long-standing. Chances of carrying any resistance mutation were 12% higher in MSM with recent infection (PR 1.12, 95% CI 1.02 to 1.22) and chances of carrying a nonnucleoside resistance mutation were 31% higher in men with recent infection (PR 1.31, 95% CI 1.16 to 1.53). These findings reflect the tendency of mutant virus to fade over time in a viral population.
Compared with MSM 40 to 49 years old, those 13 to 29 had a 17% higher prevalence of any transmitted resistance mutation (PR 1.17, 95% CI 1.04 to 1.32). Half of all transmitted resistance mutations (50.3%) occurred in 13- to 29-year-old men, though that group also represented almost half of the new HIV diagnoses in the analysis (5116 of 10,894 cases, or 47%). The resistance rate was not significantly higher in 30- to 39-year-old men than in 40- to 49-year-olds. Resistance mutation prevalence did not vary by race/ethnicity or by year of diagnosis from 2008 through 2011.
Among the cities studied, Seattle had the highest transmitted resistance rate at 22.0% of new diagnoses, followed by Chicago at 18.6%, Dallas and Detroit at 18.2% each, and New York City at 18.0%. Los Angeles (16.8%) and Miami (16.6%) had intermediate rates, and Denver (14.1%) and New Orleans (12.7%) had the lowest rates. The CDC investigators suggested these variations may reflect differences in the size of MSM populations, linkage to care, or adherence to antiretrovirals from one city to the next.
Regional differences in antiretroviral prescribing patterns may partly explain why three different cities had the highest rates of nonnucleoside mutations (14.6% in Seattle), nucleoside/nucleotide mutations (9.9% in Miami), and protease inhibitor mutations (7.5% in Dallas) in antiretroviral-naive MSM.
Prevalence of any transmitted resistance mutation or mutations to any of the three classes analyzed did not change significantly--up or down--from 2008 to 2011.
"Timely resistance testing among MSM to identify drug resistance early in infection," the researchers stress, "is crucial for optimal ART provision, viral suppression, and reduced HIV transmission."
1. Banez Ocfemia MC, Saduvala N, Oster AM, et al. Transmitted HIV-1 drug resistance among men who have sex with men, 11 US jurisdictions, 2008-2011. CROI 2014. Conference on Retroviruses and Opportunistic Infections. March 3-6, 2014. Boston. Abstract 579