CD4⁺-T-Cell-Mediated Resistance to Systemic Murine Candidiasis Induced by a Membrane Fraction ofCandida albicans

Abstract

We induced resistance to systemic Candida albicansinfection through CD4+-cell-mediated immunity in mice by immunization with subcutaneous injections of live C. albicans cells emulsified in incomplete Freund adjuvant. Using the resistant mice, we tested subcellular fractions of C. albicans cells for antigenicity. The fractions were derived from digested surface cell walls, insoluble membranes, or soluble and insoluble cytoplasmic materials, which were prepared by treatment with cell wall-digesting enzymes followed by lysis of the consequent protoplasts. Interestingly, the live-cell-immunized mice showed strong cell-mediated immune responses to the membrane fraction (C. albicans membrane antigen [CMA]). In addition, immunization with CMA induced resistance to systemic candidiasis, which disappeared upon administration of anti-CD4 monoclonal antibody. Infusion of splenocytes from the CMA-immunized mice conferred resistance on SCID mice, whereas infusion of CD4+-T-cell-depleted splenocytes was unable to induce resistance, indicating the importance of CD4+ lymphocytes for resistance. These results suggest a potential for the membrane fraction to act as an antigen conferring resistance to systemic candidiasis in place of live cells and also as a source for the isolation of a new antigen.

Protection of Mice from Lethal Endogenous Candida albicans Infection by Immunization with Candida Membrane Antigen

“…Therefore this immunizing procedure can be assumed to be protective for patients facing the risk of systemic candidiasis with endogenous Candida dissemination. This assumption is reasonable because this procedure is highly protective against the intravenous challenge of Candida cells in mice, as reported previously (9,10).…”

“…The anti-fungal activity of these phagocytes was reported to be augmented by the cytokines, such as IFN-γ, GM-CSF, and TNF (12). In another study, a similar CMA immunization, which had protective action against the Candida infection in an intravenous inoculation model, activated CD4 cells to secrete IFN-γ, though the mice received no immunosuppressive treatment (10). Therefore CMA immunization may also augment the protective immunological function of a host against disseminated systemic infection, perhaps through the activation of a cytokine-phagocyte network.…”

“…The precipitate was washed, suspended in saline, boiled in water for 15 min, and resuspended to form a uniform homogenate with the use of a sonicator (Insonator Model 200 M, Kubota, Tokyo), yielding a purified preparation of CMA. A 2-liter culture containing approximately 2 10 12 cells yielded 1.5 g protein of CMA (9,10). CMA consisted of 60% protein, 8% carbohydrate, and 30% lipid.…”

“…We prepared CMA as previously described (9,10). Briefly, C. albicans TIMM 1768 (1,12,13) was cultured in YPD medium (yeast extract 1%, polypeptone 2%, and glucose 2%) at 35 C overnight with shaking.…”

“…In a preceding paper, Mizutani et al (9,10) reported that a purified cell membrane fraction called Candida membrane antigen (CMA) was a powerful antigen providing protection to mice against experimental candidiasis resulting from the intravenous inoculation of C. albicans.…”