What is Human Leukocyte Antigen B57(01)?

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Last updated: March 24, 2025 • View editorial policy

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From the Guidelines

HLA-B*57:01 is a genetic marker that indicates a high risk of severe hypersensitivity reactions to the HIV medication abacavir, and patients who test positive for this allele should not be prescribed abacavir due to the risk of a potentially life-threatening reaction.

Definition and Importance of HLA-B*57:01

HLA-B57:01 is a specific allele of the Human Leukocyte Antigen (HLA) system, which plays a crucial role in the immune system by distinguishing between proteins made by the body and proteins made by foreign invaders, such as viruses and bacteria. The presence of HLA-B57:01 is significant in the context of HIV treatment because it is associated with an increased risk of hypersensitivity reactions to abacavir, a medication used in combination with other antiretroviral drugs to treat HIV infection.

Clinical Implications and Recommendations

According to the most recent and highest quality evidence, including the study published in the American Journal of Kidney Diseases 1 and recommendations from the International Antiviral Society-USA panel published in JAMA 1, testing for the HLA-B*57:01 allele is recommended before initiating abacavir therapy. This is because the hypersensitivity reaction associated with abacavir in individuals with HLA-B*57:01 can be severe and potentially life-threatening, typically occurring within the first six weeks of treatment. Symptoms of this reaction can include fever, rash, gastrointestinal issues, and respiratory symptoms.

Screening and Ethnic Variations

The screening test for HLA-B57:01 is a simple blood test that is highly sensitive and specific, effectively identifying patients at risk of a hypersensitivity reaction to abacavir. It's worth noting that the presence of HLA-B57:01 varies by ethnicity, being more common in Caucasians than in African populations. However, this variation does not diminish the importance of universal screening before abacavir use, as recommended by current guidelines.

Pharmacogenetics and Personalized Medicine

The use of HLA-B*57:01 screening to guide the selection of antiretroviral therapy represents an important example of pharmacogenetics, where genetic information is used to predict an individual's response to certain medications and to prevent adverse drug reactions. This approach is a key component of personalized medicine, aiming to provide the most effective and safest treatment for each patient based on their unique genetic profile.

From the FDA Drug Label

Risk Factor: HLA-B5701 Allele: Studies have shown that carriage of the HLA-B5701 allele is associated with a significantly increased risk of a hypersensitivity reaction to abacavir Human Leukocyte Antigen B57(01), also referred to as HLA-B*5701 allele, is a genetic marker that is associated with a significantly increased risk of a hypersensitivity reaction to abacavir 2.

  • It is a specific allele of the HLA-B gene that codes for a protein involved in the immune system.
  • The presence of this allele can increase the risk of a severe and potentially life-threatening hypersensitivity reaction to abacavir.
  • Screening for the HLA-B*5701 allele is recommended prior to initiating treatment with abacavir to minimize the risk of a hypersensitivity reaction 2.

From the Research

Definition of Human Leukocyte Antigen B57(01)

  • Human Leukocyte Antigen B57(01), also known as HLA-B*57:01, is a specific allele of the HLA-B gene that plays a crucial role in the immune system 3, 4, 5, 6, 7.
  • It is a protein found on the surface of white blood cells and is involved in the presentation of peptides to T-cells, which helps to trigger an immune response.

Association with Abacavir Hypersensitivity

  • HLA-B*57:01 has been strongly associated with an increased risk of hypersensitivity reactions to the antiretroviral drug abacavir, which is used to treat HIV-1 infection 3, 4, 5, 7.
  • Studies have shown that individuals who carry the HLA-B*57:01 allele are more likely to experience a hypersensitivity reaction to abacavir, which can be life-threatening in some cases 3, 4, 7.

Screening and Diagnosis

  • Screening for HLA-B*57:01 is recommended before initiating abacavir therapy to reduce the risk of hypersensitivity reactions 3, 5, 6.
  • Several methods are available for detecting the HLA-B*57:01 allele, including allele-specific polymerase chain reaction (AS-PCR) and melting curve analysis 6.

Clinical Implications

  • The presence of HLA-B*57:01 is a strong predictor of hypersensitivity to abacavir, and withholding abacavir in individuals who carry this allele can reduce the prevalence of hypersensitivity reactions 7.
  • However, not all individuals who experience hypersensitivity reactions to abacavir carry the HLA-B*57:01 allele, and clinical vigilance is still necessary to diagnose and manage hypersensitivity reactions in all patients treated with abacavir 3, 4, 5.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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