Schiff base forming drugs: mechanisms of immune potentiation and therapeutic potential.

Abstract

CD4 T-lymphocytes, which orchestrate immune responses, receive a cognitive signal when clonally distributed receptors are occupied by MHC class II bound peptides on antigen-presenting cells. The latter provide costimulatory or accessory signals through macromolecules such as B7.1 and B7.2 which interact with coreceptors on T-cells to regulate outcomes in terms of T-cell activation or specific non-responsiveness. Complementary studies at the chemical level have implicated Schiff base formation between specialised carbonyls and amines, constitutively expressed on antigen-presenting cell and T-cell surfaces, as an essential element in specific T-cell activation. The small xenobiotic Schiff base forming molecule tucaresol, which substitutes for the physiological donor of carbonyl groups to provide a costimulatory signal to CD4 T-helper lymphocytes (Th-cells), has been developed for testing as an immunopotentiatory drug. Tucaresol, which is orally bioavailable and systemically active, enhances CD4 Th-cell and CD8 cytotoxic T-cell responses in vivo and selectively favours a Th1-type profile of cytokine production. In murine models of virus infection and syngeneic tumour growth it has substantial therapeutic activity. Schiff base formation by tucaresol on T-cell surface amines provides a costimulatory signal to the T-cell through a mechanism that activates clofilium-sensitive K+ and Na+ transport. The signalling pathway utilised by tucaresol converges with T-cell receptor signalling at the level of MAP kinase, promoting the tyrosyl phosphorylation of ERK2 by MEK (mitogen-activated protein kinase kinase). The Schiff base forming class of immunopotentiatory drug provides the first orally active, mechanism-based immunopotentiatory agents for therapeutic testing. Tucaresol is currently undergoing pilot phase I/II clinical trials as an immunopotentiator in chronic hepatitis B virus infection, HIV infection and malignant melanoma.

• Authors: H Chen, J Rhodes
• Journal: Journal of molecular medicine (Berlin, Germany) (J Mol Med (Berl)) Vol. 74 Issue 9 Pg. 497-504 (Sep 1996) ISSN: 0946-2716 [Print] Germany
• PMID: 8892054 (Publication Type: Journal Article, Review)

Chemical References

• Amines
• Benzaldehydes
• Benzoates
• Schiff Bases
• tucaresol

Topics

• Amines (metabolism)
• Benzaldehydes (metabolism, pharmacology)
• Benzoates (metabolism, pharmacology)
• CD4-Positive T-Lymphocytes (immunology, metabolism)
• Chemical Phenomena
• Chemistry
• Immunity (drug effects)
• Models, Biological
• Schiff Bases (metabolism, pharmacology, therapeutic use)