What is Resistance?

Mutations & Resistance in HIV
- How Resistance Evolves

Managing Resistance to HIV Therapy

Resistance Quiz

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Mutations & Resistance in HIV

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How Resistance Evolves
Evolution in HIV, as in other organisms, is a matter of 'survival of the fittest' - a classic example of Darwin's principle of natural selection.

The strain of HIV that predominates (because it replicates fastest) is the one best suited to its environment. The introduction of antiretroviral drug therapy changes the environment, inhibiting sensitive strains and giving drug-resistant mutants a competitive advantage^9,10. When a drug alters the environment in this way it is exerting 'selection pressure', allowing one or more formerly uncommon HIV strains to multiply while inhibiting the previously dominant strain. With some drugs, resistance emerges very rapidly. For example, complete replacement of wild-type virus by drug-resistant strains has been reported within 14 days of the start of nevirapine monotherapy¹.

How quickly resistance develops in an infected person depends on the extent of genetic variation in the virus before treatment¹¹ and on when treatment is started; ie. sequential, or combined, first line or second line.