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ICCVAM has evaluated several new versions of the murine local lymph node assay (LLNA), an
alternative test method used to identify substances that could cause allergic contact
dermatitis in humans.
The LLNA uses fewer animals than the traditional guinea pig test methods used for this purpose,
requires less time to perform, provides dose-response information, and
in most cases eliminates the potential for pain and distress in the test animal.
- ICCVAM originally made recommendations on the use of the LLNA in 1999. In 2009, ICCVAM
re-evaluated the use of the LLNA for testing pesticide formulations, metals, substances in aqueous
solutions, and other products, and in 2010 made recommendations on an expanded
applicability domain
for the LLNA.
- Internationally harmonized
performance standards for the LLNA recommended by ICCVAM and accepted by Federal agencies in
2010 enable more rapid evaluation of modified versions of the
LLNA by providing a minimum list of reference substances and accuracy and reliability criteria.
An updated LLNA protocol
included with the ICCVAM-recommended LLNA performance standards reduces animal use by 20% compared
to the original LLNA protocol.
- The reduced LLNA method recommended by ICCVAM and
accepted by Federal agencies in 2010 is a version
of the LLNA that uses 40% fewer animals than the updated LLNA to provide a “yes-no” result.
- The traditional LLNA uses a radioactive marker to assess cell proliferation. In 2010,
ICCVAM recommended
nonradioactive versions of the LLNA that allow use of the LLNA without the
hazards, environmental disadvantages, and costs associated with the use of radioactive
materials.
- ICCVAM has also recommended that the LLNA can be used to categorize substances as
strong sensitizers, although it cannot be considered a stand-alone assay to categorize skin
sensitization potency for other than strong sensitizers.
Strong sensitizers are those substances considered to have a significant potential for causing
hypersensitivity.
NICEATM and ICCVAM are also working with U.S. and international collaborators to evaluate methods for
assessment of allergic contact dermatitis hazard potential that do not use animals.
Please see below for more information about these activities; click on heading links for more
information and links to relevant ICCVAM documents,
Federal Register notices, and peer review information.
View publications and presentations on ICCVAM evaluations of the murine local
lymph node assay for identification and classification of sensitizers
View guidelines and regulations relevant to assessment of allergic contact
dermatitis hazards
NICEATM has requested public comment and submission of relevant data on an ICCVAM test method
nomination for validation studies proposed to determine the usefulness and limitations of an in
vitro test method to identify substances that have the potential to produce allergic contact
dermatitis. This method, the electrophilic allergen screening assay, assesses test substance
activity in a key step in the biochemical pathway leading to skin sensitization.
In 2007, the U.S. Consumer Product Safety Commission (CPSC) requested that NICEATM and ICCVAM
assess the validation status of new versions and applications of the LLNA. One activity conducted by
ICCVAM in response to this request was an evaluation of the use of the LLNA for potency
categorization of chemicals causing allergic contact dermatitis in humans. ICCVAM concluded that the LLNA can be used to
categorize substances as strong skin sensitizers (Globally Harmonized System of Classification and
Labelling of Chemicals Subcategory 1A). However, substances that are not
identified as strong sensitizers using the LLNA require additional information to categorize
them as other than strong sensitizers (Globally Harmonized System of Classification and
Labelling of Chemicals Subcategory 1B). Acceptance of the LLNA for categorization of substances as
strong skin sensitizers could broaden the use of the LLNA in place of guinea pig tests, reducing and
refining animal use for this purpose.
The endorsement of several ICCVAM-recommended alternative testing methods has provided Federal public health
agencies and regulated industries with important new tools for assessing potential allergic contact dermatitis hazards presented by chemicals
and products. The recommended test methods were the topic of a January 2011 workshop organized by
NICEATM and ICCVAM. The workshop provided information on current best practices for safety testing to determine whether
chemicals and products may cause allergic contact dermatitis in humans
using methods and approaches that reduce, refine, and replace animal use.
ICCVAM has made recommendations to Federal agencies on
the use of two nonradioactive versions of the LLNA. The availability of LLNA methods that do not
use radioactivity is expected to allow more institutions to take advantage of the animal welfare
benefits of the LLNA, and provides environmental benefits as well.
Following its original evaluation of the LLNA in 1999 (see last paragraph below), ICCVAM
recommended the LLNA as a valid alternative to traditionally accepted guinea pig test methods for
assessing the allergic contact dermatitis hazard potential of substances for most testing
situations. The CPSC nomination noted above requested that NICEATM and ICCVAM evaluate the
applicability of the LLNA for testing formulations, metals, substances in aqueous solutions, and
other products with the expectation that a wider applicability domain for the LLNA would enable
wider use. ICCVAM has recommended that the LLNA
may be used to test any chemical or product for allergic contact dermatitis hazard potential unless
the chemical or product to be tested has properties that may interfere with the ability of the LLNA
to detect sensitizing substances.
NICEATM and ICCVAM actively participate in the development of OECD Guidelines for the Testing of
Chemicals and OECD Guidance Documents relevant to toxicology and safety testing. OECD Test
Guidelines are based on the most relevant internationally agreed-upon testing methods used by government,
industry, and independent laboratories.
NICEATM and the ICCVAM interagency Immunotoxicity Working Group contributed to the development of
a number of OECD Test Guidelines and Guidance Documents.
Click on the heading above to view summaries of these activities.
There is a growing international need for non-animal test methods that can identify substances with the
potential to cause allergic contact dermatitis in humans. Working with U.S. and
international collaborators, NICEATM and ICCVAM are evaluating the application of in vitro test methods
as part of integrated decision strategies for the regulatory safety assessment of allergic contact
dermatitis hazards.
ICCVAM has prepared performance standards for the LLNA, which can be used to evaluate the
accuracy and reliability of new versions of the LLNA that are considered functionally and
mechanistically similar to the accepted LLNA test method. These performance standards reflect
extensive international discussions and represent a set of
internationally harmonized standards for the conduct of the LLNA
(essential test method components, a minimum list of reference substances,
and accuracy and reliability criteria). The ICCVAM-recommended LLNA
performance standards also include a updated LLNA test method protocol that reduces animal use by
20% compared to the original ICCVAM-recommended LLNA test method protocol by decreasing the minimum
number of animals per dose group from five to four.
One of the modifications of the LLNA evaluated by NICEATM and ICCVAM in response to the CPSC
nomination was the “reduced” LLNA (rLLNA). When used to test a substance for the potential to cause
allergic contact dermatitis, the rLLNA uses fewer animals than the LLNA to provide a “yes-no”
result. ICCVAM has
recommended that the rLLNA be used routinely to determine the allergic contact dermatitis hazard
potential of chemicals and products before conducting the multidose LLNA in testing situations
in which a negative result is expected or dose-response information is not required.
Since the rLLNA uses only a single high-dose
group along with concurrent negative and positive control groups, use of the rLLNA can reduce the number of animals needed for each test by 40% compared to the
multidose LLNA.
In September 1998, NICEATM hosted a meeting of an independent peer review panel
to review the validity of the LLNA as an alternative test method to guinea pig tests for
assessing the allergic contact dermatitis potential of chemicals.
The panel concluded that the LLNA is a valid alternative to
currently accepted guinea pig test methods, and that the LLNA reduces the number of animals required
for testing, eliminates animal pain and distress, requires less time to perform, and provides dose-response information.
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