Lymphoproliferative and cytotoxic responses of human peripheral blood mononuclear cells to mannoprotein constituents of Candida albicans

Abstract

Two major proteoglycan constituents (designated F1 and F2) of the cell wall of Candida albicans were separated by ion-exchange chromatography from a crude carbohydrate-rich extract (GMP), and investigated for their chemical and molecular composition, antigenicity and immunomodulatory properties in cultures of human peripheral blood mononuclear cells (PBMC). Both fractions consisted predominantly of Periodic acidSchitf (PAS) and concanavalin A (Con A)-reactive material consisting of > 90 % mannose, 3-5% protein and small amounts of phosphorus; each was recognized by an anti-Candida rabbit serum as well as by a monoclonal antibody (mAb AF1) directed against an oligosaccharide epitope present on the fungal cell surface. When F1 and F2 were subjected to SDS-PAGE, transblotted and stained with enzyme-conjugated mAb AF1 or Con A, most of the antibody or lectin bound to high molecular mass (> 200 kDa) polydisperse material, some of which was present in F2 (as in the starting GMP extract) but absent in F1. This difference was also observed in PAS-stained gels of the two fractions.The F2, but not the F1, constituent was as active as the unfractionated GMP extract in inducing lymphoproliferation, production of the cytokines interleukin-2 and interferon-y, and generation of cytotoxicity against a natural-killer-sensitive target cell line (K562). These immunomodulatory properties were, like those possessed by GMP, protease-sensitive and heat-stable. Treatment of PBMC cultures with a modulatory anti-Tcell receptor antibody abolished the lymphoproliferation induced by GMP and F2 but not that induced by phytohaemagglutinin, showing that the mannoprotein materials of C. albicans acted through interaction with the antigen receptor complex.

Mannoprotein fromCryptococcus neoformansPromotes T-Helper Type 1 Anticandidal Responses in Mice

“…In particular, Candida and Cryptococcus MPs were shown elsewhere to induce lymphoproliferation (19,23) and cytokine production (21,22,27). Previous data showed that interleukin-12 (IL-12) plays a pivotal role in induction of the Thelper type 1 (Th1) response against C. neoformans infection, this response being essential for protection (6).…”

Biochemical and Immunological Characterization of MP65, a Major Mannoprotein Antigen of the Opportunistic Human Pathogen Candida albicans

“…Despite the increased awareness of the important role that CMI plays in the defense against this fungal pathogen (reviewed in references 1 and 38), very few CMI antigen targets for it have so far been identified. These include heat shock proteins, enolase, and a number of as yet uncharacterized mannoproteins, some with adhesin function (6,12,15,27,29,30,40).We have long been studying a 65-kDa mannoprotein (designated MP65) which is present in both the structural and secretory mannoprotein material and which is recognized by T cells of peripheral blood of practically all healthy individuals (quasiuniversal antigen) (20,(42)(43)(44). In mice immunized with whole fungal cells or MP65-rich mannoprotein extract (MP-F2) (44), a vigorous lymphoproliferative response with a prevalent T-helper type 1 (Th1) cytokine pattern was elicited in in vitro MP65-stimulated lymphomonocyte cultures (31).…”

“…We have long been studying a 65-kDa mannoprotein (designated MP65) which is present in both the structural and secretory mannoprotein material and which is recognized by T cells of peripheral blood of practically all healthy individuals (quasiuniversal antigen) (20,(42)(43)(44). In mice immunized with whole fungal cells or MP65-rich mannoprotein extract (MP-F2) (44), a vigorous lymphoproliferative response with a prevalent T-helper type 1 (Th1) cytokine pattern was elicited in in vitro MP65-stimulated lymphomonocyte cultures (31).…”

Responsiveness of human polymorphonuclear cells (PMNL) to stimulation by a mannoprotein fraction (MP-F2) of Candida albicans; enhanced production of IL-6 and tumour necrosis factor-alpha (TNF-α) by MP-F2-stimulated PMNL from HIV-infected subjects

“…Moreover, and perhaps more importantly, this mannoproteic constituent is expressed on the cell surface of C. albicans [13], a microorganism endowed with a high rate of colonization and invasion of mucosal sites in AIDS patients. In HIV + subjects, the intense C. albicans colonization and spread of infection in several mucosal sites may lead to strong activation of PMNL, in addition to other cytokineproducing cells, such as macrophages and Candida-responsive lymphocytes [10,11]. Thus, activated PMNL should be considered as possible in vivo contributors to determine the state of chronic immune activation typical of the HIV + subject.…”

“…One of the most effective PMNL activators is a mannoprotein fraction of Candida albicans, designated MP-F2 [9][10][11], which induces lactoferrin secretion and causes growth inhibition of lactoferrin-sensitive microorganisms [8,12]. Candida albicans itself is a human commensal and opportunistic pathogen which causes very frequent, extensive infections of the mucosa (oropharingeal, oesophageal, vaginal) in subjects infected by HIV [13,15].…”