Non-nucleoside resistance is efficiently transmitted within infection ‘clusters’
HIV that is resistant to the non-nucleoside drugs (NNRTIs) efavirenz and nevirapine is efficiently transmitted between members of sexual networks, a study from Canada has found. The proportion of NNRTI-resistant HIV could even be amplified by rapid, ‘chain reaction’ transmission between members of large networks, the study finds.
In contrast, other types of HIV drug resistance are more likely to appear within isolated cases of infection and seem to be ‘filtered out’ by such chain transmission.
An important study last year of HIV transmission in Quebec, Canada, in which people (largely gay men) recently infected with HIV had their virus subjected to extremely precise analysis of its entire polymerase gene, found that half of HIV infections in the province occurred in smaller or larger clusters of anything between two and 17 people, where a ‘cluster’ was defined as the occurrence of HIV viruses that were genetically identical or near-identical in different people.
Estimating the dates of transmission and the rate of change in the HIV polymerase gene showed that about half of all infections were transmitted by people in primary HIV infection, in the first six weeks or so when people’s viral loads are high.
Subsequent studies from other parts of the world have confirmed that a high proportion (25%-50%) of HIV infections is acquired from people who are themselves in primary infection.
Dr Mark Wainberg of the team at the McGill AIDS Centre in Montreal that conducted the initial study undertook a further evaluation of the same cohort to establish the frequency of transmission of drug-resistant virus.
They found worrying evidence that clustering of transmissions and therefore rapid-fire ‘cascades’ of transmission were getting more common
Gus Cairns’s article for Aidsmap gives further details as well as links to Aidsmap’s information about the transmission of drug-resistant HIV
Link to Aidsmap article
HIV 9 - Ninth International Congress on Drug Therapy in HIV Infection, Glasgow.
Link to HIV 9.com
Reference
O114.NNRTI mutations are efficiently transmitted within clusters of new infections. Abstract Journal of the International
BG Brenner
Journal of the International AIDS Society 2008, 11(Suppl 1):O4 doi:10.1186/1758-2652-11-S1-O4
Link to abstract 0114
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