A study by the UK HIV Drug Resistance Database (UK HDRD), published in HIV Medicine, has found that existing HIV drug resistance in the UK is likely to have little impact on a new HIV prevention strategy that uses antiretroviral drugs to reduce the risk of infection in HIV-negative people.
Recent research shows that a new HIV prevention strategy called pre-exposure prophylaxis (PrEP) could reduce the risk of HIV infection. This involves HIV-negative people at risk of acquiring HIV taking existing antiretroviral drugs before being exposed to HIV. However, research in macaque monkeys has indicated that current drug resistance in HIV-positive people could lead to the transmission of virus which PrEP cannot protect against.
The UK HDRD which is coordinated by CTU, gathers the results of most HIV drug resistance tests which are routinely performed in the UK, and is linked to the UK Collaborative HIV Cohort (UK CHIC) study which collects HIV-positive patient information. This analysis examined the resistance tests from 2,678 men who have sex with men for resistance to two HIV drugs, tenofovir and emtricitabine.
Looking specifically at 2008, the authors found that a man having a homosexual encounter with an HIV-infectious partner (viral load greater than 50 copies/ml) had between 0.9-4.1% chance of being exposed to virus which PrEP might not have worked against.
The study also found that since 2005, levels of potential resistance to PrEP have been declining and other research suggests that the current levels of drug resistance in HIV-positive people would have a limited impact on the effectiveness of PrEP.
The authors conclude that resistance should continue to be monitored in the HIV-positive population and future PrEP studies.