Genetic markers

CCR5 co-receptor mutation

Over a decade ago, scientists found that a 32-base pair deletion in the gene for CCR5 has a protective effect against the development of HIV. Individuals carrying this deletion are either heterozygous (deletion from one parent) or homozygous (deletion from both parents) for delta 32. Testing for this deletion is normally done only in research settings. See Receptors, co-receptors and immunity to HIV for further information on this topic.

HLA-B*5701 screening

A close association between abacavir hypersensitivity reaction and the presence of the class 1 HLA-B*5701 allele has led to recommended screening before starting an abacavir-containing regimen.1 2 

Anyone who is positive for HLA-B*5701 should never take abacavir and this status should be recorded in the medical chart. A negative test does not rule out the possibility of a hypersensitivity reaction, so patients about to begin abacavir therapy should be informed about possible reactions to the drug.

If a reaction is to occur, it will usually happen within the first six weeks of treatment. The risk of occurrence is higher in white patients (5 to 8%) than it is in black patients (2 to 3%).2 A negative skin patch test for HLA-B*5701 does not rule out a need for clinical vigilance for hypersensitivity reaction.3 4 5  



  1. Mallal S et al. HLA-B*5701 screening for hypersensitivity to abacavir. NEMJ 358(6): 568-579, 2008
  2. Saag M et al. High sensitivity of human leukocyte antigen-B*5701 as a marker of immunologically confirmed abacavir hypersensitivity in white and black patients. Clin Infect Dis 46: 1111-1118, 2008
  3. Fox J et al. An unusual abacavir reaction. AIDS 22: 1520–1522, 2008
  4. Bonta P et al. Severe abacavir hypersensitivity reaction in a patient tested HLA-B*5701 negative. AIDS 22: 1522-1523, 2008
  5. Phillips E et al. Pharmacogenetics and clinical characteristics of patch-test confirmed patients with abacavir hypersensitivity. Seventh International Workshop on the Clinical Pharmacology of HIV Therapy, Lisbon, abstract 33, 2006
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.