Candida Allbicans | Delayed Type Hypersensitivity (DTH) Assay | Immune Suppressive Agent Assay

Delayed Type Hypersensitivity (DTH) Reactions


(Purified Candida albicans, Chitin, Recall Antigen) Many agents, such as drugs, microbial and viral infections, exposure to radiation, etc. have the effect of locally or systematically suppressing Cell-Mediated (delayed, Type IC) immune responses. A common method developed for the in vivo determination of delayed type hypersensitivity (DTH) developed for humans has been adapted for many types of laboratory animals.

DTH assays usually incorporate the use of formalin fixed whole microbes as a priming and post challenge (recall antigen(s)). In mice Candida albicans is commonly used. Unfortunately, for numerous reasons using whole formalin fixed microbes as a recall antigen(2) can result in spurious or difficult to interpret results.

Fortunately, Candida albicans produces a species specific form of the N-acetyl-D-glucosamine polysaccharide, (chitin) particularly when it converts to its pathogenic form (e.g. in the disease systemic candidiasis, a disease commonly associated with immune suppressed patients). It is believed that this form of chitin is used by Candida as a type of cellular cement so as to allow for cellular attachment for the purpose of colonizing the host's organs. ALerCHEK, Inc. has developed a method for purifying and solubalizing this form of chitin in physiological saline. More recently, via cooperation with scientists at MD Anderson Cancer Center this purified for of chitin has been demonstrated to be a superior DTH recall antigen in mice as compared to formalin fixed Candida a. It is postulated that this polysacharide elicits a very high and definitive T-cell response resulting in better resolution of the assay. Additionally, immune suppressive agents known to be present on Candida's cell wall are absent.

ALerCHEK, Inc. is making this polysaccharide commercially available to institutions which are currently performing or are considering performing DTH assays. This polysaccharide may also have value for the purpose of improving T-cell immune responses to vaccines, e.g. chemically coupling the polysaccharide to viral antigens.