Transmission of Drug-resistant HIV Strains in Canada

While suboptimal therapy, poor adherence, and treatment failure can lead to the emergence of drug-resistant HIV, individuals may also be newly infected with HIV strains that are already resistant to antiretroviral medications.

Researchers with the Public Health Agency of Canada in Ottawa sought to determine the frequency of transmission of primary drug-resistant virus. They conducted a representative population-based study of drug resistance among newly diagnosed HIV cases in Canada.

The authors tested stored blood samples from all treatment-naïve HIV positive individuals who were newly diagnosed between 2000 and 2001, using a modified "detuned" antibody test (Organon Teknika Vironostika HIV-1-LS assay) to distinguish recent infections from infections that occurred in the past but were only recently diagnosed. They then compared differences in drug-resistance profiles between the recent and longer-established infections.

Results

In this study population, 8.1% had genotypic evidence of transmitted drug resistance mutations:

- 4.1% with resistance to nucleoside reverse transcriptase inhibitors (NRTIs);

- 1.4% with resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs);

- 1.5% with resistance to protease inhibitors (PIs);

- 1% with resistance to two or more classes of drugs.

A higher proportion of recent infections had genotypic evidence of transmitted drug resistance compared with longer-established infections (12.2% vs 6.1; P = 0.005).

Transmitted drug resistance was identified mainly among recently infected Caucasian men who have sex with men, but it was not limited to this group.

Compared with the year 2000, a higher proportion of recently infected individuals with resistance-conferring mutations were diagnosed during the year 2001 (66.7% vs 46.6%).

Conclusion

In Canada, "transmitted drug resistance is occurring within all three drug classes and across different population groups," the authors concluded. "The results suggest that the prevalence rates may be higher among recent versus established infections." Given the public health implications of transmission of drug-resistant HIV, they added, "it is important to continue population-based drug resistance surveillance to guide optimum prevention and treatment of HIV infection."

7/28/06

Reference
G C Jayaraman, C P Archibald, J Kim, and others. A population-based approach to determine the prevalence of transmitted drug-resistant HIV among recent versus established HIV infections: results from the Canadian HIV strain and drug resistance surveillance program. Journal of Acquired Immune Deficiency Syndromes 42(1): 86-90. May 2006.