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Primary HIV drug resistance surveillance in Canada
Presented by Chris Archibald, Canada.
M. Ofner1, J. Brooks2, N. Goedhuis1, R. Pilon2, P. Sandstrom2, C. Archibald1
1Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, Ottawa, Canada, 2National HIV and Retrovirology Laboratories, Public Health Agency of Canada, Ottawa, Canada
Background: The Canadian HIV Strain and Drug Resistance Surveillance Program is a national, collaborative project that monitors strain type and genetic drug resistance characteristics for newly diagnosed HIV-1 cases in Canada. We describe here the prevalence of and factors associated with HIV drug resistance in treatment-naïve individuals, newly diagnosed with HIV between 1998 and 2005.
Methods: HIV subtype and genotypic resistance testing was carried out using population based sequencing on diagnostic sera and plasma collected from treatment-naïve, newly diagnosed HIV cases between 1998 and 2005. Drug resistance mutations were identified and interpreted using the Stanford HIV DR Database and IAS guidelines. Samples were identified as recent (infected within approximately previous 6 months) or established (>6 months) infections using the Abbott 3A11-LS and Organon Teknika Vironostika HIV-1-LS assays.
Results: Drug resistance information was available for 3,374 cases diagnosed between 1998 and 2005. Of these, 9.2% were found to have mutations associated with resistance to one or more classes of antiretroviral drugs; resistance to >=2 drug classes were found in 1.0% of cases. The most frequently identified NRTI, NNRTI and PI mutations were M41L, K103N, and L90M, respectively. The proportion of drug resistance was slightly higher in women (9.8%) than men (9.0%) (p=0.57) and was significantly higher in recent (11.5%) than established (8.2%) HIV infections (p=0.01). There was no change in the overall proportion of cases that showed drug resistance during the period 2000-2005, although there was an increasing trend in the proportion resistant to NNRTI drugs and a decreasing trend for NRTI drugs.
Conclusions: The assessment of primary HIV drug resistance is a new and evolving field and has the potential to contribute to the development of population recommendations for initial therapy and to serve as an indicator to help evaluate the effectiveness of prevention programs.
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