Abstract
Access to combination antiretroviral treatment (ART) has improved greatly over recent years. At the end of 2011, more than eight million HIV-infected people were receiving ART in low-income and middle-income countries. ART generally works well in keeping the virus suppressed and the patient healthy. However, treatment only works as long as the virus is not resistant against the drugs used. In the last decades, HIV treatments have become better and better at slowing down the evolution of drug resistance, so that some patients are treated for many years without having any resistance problems. However, for some patients, especially in low-income countries, drug resistance is still a serious threat to their health. This essay will review what is known about transmitted and acquired drug resistance, multi-class drug resistance, resistance to newer drugs, resistance due to treatment for the prevention of mother-to-child transmission, the role of minority variants (low-frequency drug-resistance mutations), and resistance due to pre-exposure prophylaxis.
Highlights
Access to combination antiretroviral treat- practice in high-income countries, are almost ment (ART) has improved greatly over recent completely unavailable in low-income coun- Conflicts of interest: the author declares no years
The sim- presence of minority variants. This means that many resistance mutations and an uncommon plest option, which is no longer recommended, even if a mutation is present at high enough combination of three or more drugs needs to is to use nevirapine (NVP, an NNRTI)
Treatment could be started with a set of drugs that are not susceptible to drug-resistance and once the viral load is sufficiently reduced – and the abundance of any minority variant is reduced – the patient can switch to the treatment of choice, such as NNRTI-based treatment, which is cheaper and available as a coformulated one-pill-a-day regimen
Summary
Drug-resistant HIV strains can be transmitted from one patient to another. Due to such transmitted drug resistance, a newly infected patient may carry a drug-resistant virus even though he or she has not yet used antiretrovi-. A third option has been example, Lima et al.[11] show that drug resist- The Plato II study showed that, in Europe, added to the list of recommended combina- ance is more than twice as common in patients the prevalence of patients who had failed on all tions for treatment-naive individuals: two with 80-95% adherence when compared to three major drug classes (NRTI, NNRTI and NRTIs combined with an integrase strand patients with adherence levels of 95% or high- PI) increased steadily after 1996, but remained transfer inhibitor (INSTI). The probability of resistance is reduced if NVP monotherapy is avoided by adding a so-called NRTI tail, i.e., a combination of two NRTIs (ZDV and 3TC) for one week after delivery.[13,26] Alternatively, pregnant women may be treated with a three-drug combination therapy throughout their pregnancy and while they are breastfeeding, even if they are not eligible for treatment for their own health
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