Evaluation of the Miniature Swine for Use in Immunotoxicity Assessment: I. Quantitation of Humoral Responses to Sheep Red Blood Cells and Effects of Cyclophosphamide

US FDA "Redbook II" immunotoxicity testing guidelines and research in immunotoxicity evaluations of food chemicals and new food proteins

The rapid advances in the field of immunology and an understanding of the potential adverse effects of xenobiotics on the immune system have resulted in the development of a discipline in toxicology now referred to as immunotoxicology. This discipline has evolved steadily over the last 2 decades as a result of research in the national and international communities. Various US, European, and Japanese regulatory agencies have recognized a need to promulgate testing guidelines for immunotoxicity in support of the approval process involving toxicological testing. The US Food and Drug Administration "Redbook II" guidelines and some of the research conducted in support of the concepts and testing strategies are presented here. Concerns raised with regard to these guidelines are included, as are on-going initiatives in development of experimental approaches for assessing allergic potential and/or hypersensitivity responses to new foods and food constituents.

Testing guidelines for evaluation of the immunotoxic potential of direct food additives

Immunotoxicity testing is a new addition to the safety assessment guidelines for direct food and color additives. The approaches and philosophy for this area of specialized testing are consistent with the case-by-case strategy applied in the regulatory approval process, which is based on structure-activity relationships, preexisting knowledge, and projected exposure estimates. Specialized testing such as immunotoxicity is not part of the basic testing requirements, but would be applied when indicators are positive. Concepts for immunotoxicity testing have evolved, in part, from research for evaluating various testing methods as well as specific study designs. This research, conducted over the last decade, has focused mainly on the rat as the rodent species of choice. The miniature swine was evaluated as a nonrodent model. Testing is defined by type 1 and type 2 tests, which differ in that type 1 tests are performed on the same animals used in the core study design. Sets of type 1 and type 2 tests, with reference to the indicators, define various testing levels. Retrospective testing, expansion of basic testing (such as histopathology and serum chemistry profiles), and alternative study designs, which include satellite groups for evaluation of the functional capacity of the immune system, can be considered in the evaluation of immunotoxic potential.