Photosensitization Screening Assay Using an Enhanced (Flow Cytometry-based)
Local Lymph Node Assay (PHOTO-LLNA)

What is the Photo-LLNA?

Until recently, modified guinea pig sensitization assays were used to test the photoallergenic potential of chemicals.  However, the EPA, OECD and other international regulatory authorities have disallowed or replaced these tests with the mouse Local Lymph Node Assay (LLNA).

Currently, there exist no validated alternative photoallergy (photosensitization) assays.  The pharmaceutical, chemical, consumer product and cosmetics industries have increasing concerns about protecting consumers from UVR- and chemically-induced allergic contact dermatitis and urgently need rapid, cost-effective photoallergenicity assays. 

To address this need, we have adapted the LLNA protocol to include UV irradiation and the use of flow cytometry to measure lymphocyte proliferation and activation markers, which correlate with an allergenic response and improve the accuracy and predictivity of Photo-LLNA.  Phase I results and other preliminary data demonstrate the technical feasibility of the assay, and since our assay uses BrdU incorporation to measure lymphocyte proliferation, there is an added bonus of eliminating the need for radioisotopes, reducing hazardous waste. 

 >>Back to the top<<

Photo-LLNA Study Outline

Applications

MB Research offers alternative photoallergenicity screening assay to members of the pharmaceutical, biotech, cosmetic, and chemical industry to assess the photoallergenic potential of chemicals in consumer products.

A survey of our clients indicates there is an increased demand for rapid and cost-effective (photo)sensitization tests, as well as for mechanistic-based tests, which provide both qualitative and quantitative information at a reduced cost when compared to currently accepted screening tests.

For more information, please contact us here.

 >>Back to the top<<

Background Information

Worldwide regulatory agencies including the EPA and OECD are phasing out acceptance of sensitization assays in the Guinea Pig to determine (photo)allergic potential of chemicals.  A major disadvantage of these assays is that it uses a large number of guinea pigs as the test model.  As an alternative to the Guinea Pig model, we offer the Photo-LLNA to meet industrial demand and a government mandate to develop and validate alternative test models that refine, reduce, or replace the use of animal models in toxicology testing. 

Development of alternative assays in toxicological evaluations is a major interest and goal for companies that produce consumer products because of the societal and political pressures.  This proposed Photo-LLNA is an adaptation of the ICCVAM accepted alternative - Local Lymph Node Assay to screen for possible photoallergens in consumer products.  This assay will fulfill the growing need for a rapid, cost-effective assay that predicts not only sensitization but also photoallergenicity. 

 Originally designed to screen irritants and allergens, the Enhanced Local Lymph Node Assay Using Flow Cytometry (SBIR Grant R44-10234-04) was adapted to investigate photoreactive chemicals, which can be found all around us in such substances as medications, soaps, cosmetics, deodorants, hair dyes, lotions, food, and artificial sweeteners.  In order to test for these photoallergens, expensive, time-consuming photo safety studies must be performed.  It is noteworthy that there are no validated alternative photoallergenicity methodologies available.  Pharmaceutical, chemical, consumer product and cosmetics industries have increasing concerns about UVR- and chemically-induced allergic contact dermatitis and urgently need cost-effective photoallergenicity assays that reduce the use of animals in product safety testing. 

The lack of capable laboratories in the United States to perform alternative photosensitization studies is troubling, since exposure to UVR is increasing due to the depletion of the protective ozone layer, while more cosmetics, pharmaceuticals, and consumer products are produced each year.  The Photo-LLNA offers product safety stewards an alternative to guinea pig tests with a high-throughput photoallergy screening assay utilizing alternative testing.  The feasibility of this murine alternative testing method to identify substances with photoallergic properties was demonstrated in Phase I.  With the continued development of the Photo-LLNA, we plan on further representing the functionality of Photo-LLNA as a refinement of the existing LLNA and a replacement of guinea pig test models. 

The guinea pig assays generally require 10 animals per concentration and several weeks for the induction and elicitation phases.  In comparison, the Photo-LLNA requires only 5 animals per group and the length of a standard screening assay is shortened to only 6 days with a reduction of pain and distress due to the need for only an induction phase and no subsequent exposures.  The reduction in the number of animals, use of mice versus guinea pigs or rabbits, and the reduction of the amount of time, which equates to less pain and distress, clearly adheres to the 3-Rs philosophy of Reduce, Refine and Replace the use of animals in scientific research.

 >>Back to the top<<

Serving the chemical, agricultural, cosmetic and pharmaceutical industries
 since 1972 and a leader in the use and development of
alternative toxicology test methods.

MB RESEARCH LABORATORIES
PO Box 178
Spinnerstown, PA  18968
Tel:  215-536-4110
Fax:  215-536-1816