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Evaluation of the Applicability Domain for the LLNA

The murine local lymph node assay (LLNA) is used to assess the potential of a test substance to induce allergic contact dermatitis in humans. After an evaluation of data in an expanded LLNA database, ICCVAM recommended that the LLNA may be used to test any chemical or product unless the chemical or product to be tested has properties that may interfere with the ability of the LLNA to detect sensitizing substances. The ICCVAM recommendations on the applicability domain of the LLNA have been transmitted to Federal agencies, which accepted or endorsed the ICCVAM recommendations.

Test Method Evaluation Report (June 2010) containing ICCVAM recommendations

National and International Acceptance of the Expanded Applicability Domain of the LLNA

In April 2011, the U.S. Environmental Protection Agency announced that it was expanding the existing dermal sensitization test guideline to include testing of end-use pesticide products using the LLNA. The EPA policy notes the animal welfare advantages of the LLNA as well as the ability of the LLNA to provide a more quantitative assessment of dermal sensitization than traditional guinea pig methods for assessing allergic contact dermatitis hazard potential.

EPA policy document (April 2011)

NICEATM and the ICCVAM Immunotoxicity Working Group also developed a revision to the test guideline issued by the Organisation for Economic Co-operation and Development (OECD), OECD Test Guideline 429, that describes the conduct of the LLNA. The revised Test Guideline 429, which was adopted by OECD in July 2010, incorporates the updated applicability domain for the LLNA. It also includes the updated protocol for the LLNA and provides for the use of the reduced LLNA method when appropriate.

Updated OECD Test Guideline 429 — Skin Sensitization: Murine Local Lymph Node Assay

Background and ICCVAM Evaluation

Following its original evaluation of the LLNA in 1999, ICCVAM recommended the LLNA as a valid alternative to traditionally accepted guinea pig test methods for assessing allergic contact dermatitis hazard potential for most testing situations. In January 2007, the U.S. Consumer Product Safety Commission (CSPC) requested that NICEATM and ICCVAM assess the validation status of new versions and applications of the LLNA, including use of the LLNA to evaluate a wider range of substances (broaden the applicability domain of the LLNA). Substances to be considered in this evaluation included pesticide formulations, metals, substances in aqueous solutions, and other products updated from the original ICCVAM recommendation on the LLNA.

CPSC nomination letter

The ICCVAM interagency Immunotoxicity Working Group (IWG), working with NICEATM, prepared a draft background review document (BRD) and draft recommendations for application of the LLNA for evaluating pesticide formulations, metals, substances in aqueous solutions, and other products. The draft BRD and draft ICCVAM recommendations were reviewed in a public meeting of an international independent scientific peer review panel in March 2008. The Panel agreed with the ICCVAM assessment that more data were needed to evaluate these new applications of the LLNA. Additional data were submitted to NICEATM; NICEATM and the interagency IWG revised the BRD, and updated test method recommendations were developed by ICCVAM. A second Panel meeting to consider the revised documents was held in April 2009, and the Panel's report was made available in June 2009. ICCVAM considered the Panel’s report along with all public and SACATM comments as they prepared final test method recommendations, which were forwarded to Federal agencies for their consideration in June 2010.

2009 peer review panel report

Summary of the April 2009 panel meeting

Relevant references

ICCVAM recommended that the LLNA may be used to test any chemical or product, including pesticide formulations, metals (except for nickel), substances in aqueous solutions, and other products such as natural complex substances and dyes unless the chemical or product to be tested has properties that may interfere with the ability of the LLNA to detect skin-sensitizing substances. The expanded applicability domain of the LLNA is expected to result in broader use of the LLNA, enabling reduction and refinement of animal use for identification of potential allergic contact dermatitis hazards.

Transmittal of Recommendations to Federal Agencies and Agency Responses

The ICCVAM recommendations on the applicability domain of the LLNA were communicated to Federal agencies in letters from Dr. Linda Birnbaum, Director, NIEHS. These letters and the responses from ICCVAM member Federal agencies are posted below.