Effectiveness of a Vaccine Composed of Heat-KilledCandida albicansand a Novel Mucosal Adjuvant, LT(R192G), against Systemic Candidiasis

Abstract

The incidence of fungal infections caused by the opportunistic yeast Candida albicans has increased significantly in recent years. The ability to vaccinate selected patients against the organism would be advantageous. In this paper we describe a potential anti-C. albicans vaccine consisting of heat-killed C. albicans (HK-CA) in combination with the novel mucosal adjuvant LT(R192G), a genetically detoxified form of the heat-labile toxin of enterotoxigenic Escherichia coli. Groups of male CBA/J mice were immunized intranasally on three occasions at weekly intervals with 2 × 107 HK-CA per dose, alone or in conjunction with 10 μg of LT(R192G) per dose. Two weeks following the last application of antigen, some animals were challenged intravenously (i.v.) with 104, 105, or 106 viable C. albicans to assess protection as measured by survival and/or culture. Some groups of animals were footpad tested withC. albicans mannan to assess delayed-type hypersensitivity (DTH), and all the animals were bled for antibody assays. In two independent studies, all the animals immunized with HK-CA plus LT(R192G) were able to eradicate 104 C. albicans completely, as determined by kidney culture 4 weeks after challenge. Animals immunized with HK-CA only had reduced levels of C. albicans compared to the adjuvant or saline-only control. Greatly enhanced survival was observed when mice immunized with HK-CA plus LT(R192G) were challenged with 105 live C. albicans as well. Animals immunized with HK-CA plus LT(R192G) developed a significant DH response, while those given HK-CA alone developed only marginal DH responses. High immunoglobulin G (IgG) levels to cytoplasmic antigens developed in mice immunized with HK-CA plus LT(R192G), but they were found only after i.v. challenge. Addition of adjuvant shifted the antibody isotype production in i.v.-challenged animals to a response dominated by IgG2a. Clearly, intranasal immunization with killedC. albicans in conjunction with LT(R192G) afforded significant levels of protection. This novel approach offers new possibilities for the development of an effective vaccine against candidiasis for use in humans.

Evaluation of combinatorial vaccines against anthrax and plague in a murine model

“…Since a primary consideration for development of an effective vaccine against these and other potential biological warfare agents is aerosol delivery [1,42], we measured BAL fluids as well as serum samples for the presence of antigen specific antibodies. Antigen(s) were administered either subcutaneously adsorbed to an aluminum hydroxide adjuvant, the only adjuvant currently approved for human use in the United States, or mucosally in combination with LT (R192G), a derivative of the heat-labile toxin produced by some enteropathogenic strains of Escherichia coli and potent mucosal adjuvant in a variety of animal models and humans [3,4,[25][26][27][28][29][30][31][32][33][34].…”

“…Groups of 8-10 week old female BALB/c mice (Charles River Laboratories) were immunized intranasally (IN) or subcutaneously (SC) with 5 μg rPA, 5 μg F1-V, or 5 μg each of rPA and F1-V three times at weekly intervals. Mice immunized IN received the vaccine formulation admixed with 5 μg of the mucosal adjuvant LT(R192G) [3,4,[25][26][27][28][29][30][31][32][33][34] in a final volume of 8 μl in one nostril following brief exposure to Isofluorane. Mice immunized SC received the vaccine formulation adsorbed to 0.19 mg of an aluminum hydroxide adjuvant (2.0% Alhydrogel batch no.…”

Immunoproteomic analysis of the protective response obtained from vaccination with Candida albicans ecm33 cell wall mutant in mice

“…On one hand, we have observed an antibody response in sera from vaccinated mice with RML2U mutant including different antibodies against fungal proteins, some of them already described as protective (as antibodies against Hsp90 protein) [45] and, on the other hand, the isotype of all these antibodies was IgG2a, which has been described to be mainly promoted by T helper1 cells (Th1) directly related to a cellular response [48]. The relationship of the IgG2a isotype with protection (fixing complement and increasing phagocytosis) has also been described [39,40].…”

“…The other gel was blotted onto NC membrane and used for analyses with sera from vaccinated mice. As secondary antibodies we used both anti-Igs and anti-IgG2a, since the IgG2a isotype has been reported to be associated with protection (fixing complement and increasing phagocytosis) [39,40]. To ensure the reproducibility of the technique, pooled sera were assayed at least twice in different blots.…”

Immunological basis of anti‐Candida vaccines focused on synthetically prepared cell wall mannan‐derived manno‐oligomers

“…The tested fungal vaccines have a wide range of compositions ranging from whole fungal cells and inactivated organisms to subcellular vaccines based on Candida cell wall mannan , synthetically prepared oligomannosides conjugated to carrier protein or oligomannoside conjugated to single recombinant peptide fragment . Advanced trends in prophylactic and therapeutic possibilities for fungal infections are directed to development of subunit vaccines composed from single specific and immunologically active cell wall‐derived antigens.…”