Antigen-Induced Protective and Nonprotective Cell-Mediated Immune Components againstCryptococcus neoformans

Abstract

Mice immunized with two different cryptococcal antigen preparations, one a soluble culture filtrate antigen (CneF) in complete Freund’s adjuvant (CFA) and the other heat-killed Cryptococcus neoformans cells (HKC), develop two different profiles of activated T cells. CneF-CFA induces CD4+ T cells responsible for delayed-type hypersensitivity (DTH) reactivity and for amplification of the anticryptococcal DTH response, whereas HKC induce CD4+ and CD8+ T cells involved in anticryptococcal DTH reactivity and activated T cells which directly kill C. neoformans cells. The main purpose of this study was to assess the level of protection afforded by each of the two different T-cell profiles against challenge with viable C. neoformans cells, thereby identifying which activated T-cell profile provides better protection. CBA/J mice immunized with CneF-CFA had significantly better protective responses, based on better clearance of C. neoformans from tissues, on longer survival times, and on fewer and smaller lesions in the brain, than HKC-immunized mice or control mice similarly infected with C. neoformans. Both immunization protocols induced an anticryptococcal DTH response, but neither induced serum antibodies to glucuronoxylmannan, so the protection observed in the CneF-CFA immunized mice was due to the activated T-cell profile induced by that protocol. HKC-immunized mice, which displayed no greater protection than controls, did not have the amplifier cells. Based on our findings, we propose that the protective anticryptococcal T cells are the CD4+ T cells which have been shown to be responsible for DTH reactivity and/or the CD4+ T cells which amplify the DTH response and which have been previously shown to produce high levels of gamma interferon and interleukin 2. Our results imply that there are protective and nonprotective cell-mediated immune responses and highlight the complexity of the immune response to C. neoformans antigens.

The Cryptococcus neoformans GeneDHA1 Encodes an Antigen That Elicits a Delayed-Type Hypersensitivity Reaction in Immune Mice

“…cDNA synthesis. First-strand cDNA was synthesized using 500 ng of Cap-67 RNA, 500 ng of oligo(dT) [12][13][14][15][16][17][18] , and the SuperScript II RNase H Ϫ reverse transcriptase kit (Life Technologies, Gaithersburg, Md.) as specified by the manufacturer.…”

“…There is considerable experimental support for this concept from the murine model of cryptococcosis (3,6). For example, vaccination with a C. neoformans culture filtrate antigen (CneF) in complete Freund's adjuvant (CFA) induces protection against a subsequent cryptococcal infection as well as dermal delayed-type hypersensitivity (DTH) response(s) to cryptococcal antigen (17). CneF can be used in vitro to detect anticryptococcal cell-mediated immune (CMI) responses of lymphocytes from Cryptococcus-infected patients (7).…”

Identification of major proteins secreted byCryptococcus neoformans

“…Cryptococcus neoformans is an opportunistic pathogenic fungus that causes life-threatening diseases, most often meningoencephalitis, in patients with T-cell deficiencies, such as HIV-infected patients (Powderly, 1993;Mitchell & Perfect, 1995). Accordingly, previous studies with experimental models have shown that cell-mediated immunity (CMI) responses play a crucial role in controlling the outcome of cryptococcosis (Mitchell & Perfect, 1995;Murphy et al, 1998). Immunization with concentrated cryptococcal culture supernatants, designated CneF, induces Th1 lymphocyte responses that confer host protection against C. neoformans (Murphy et al, 1998;Nichols et al, 2002).…”

“…Accordingly, previous studies with experimental models have shown that cell-mediated immunity (CMI) responses play a crucial role in controlling the outcome of cryptococcosis (Mitchell & Perfect, 1995;Murphy et al, 1998). Immunization with concentrated cryptococcal culture supernatants, designated CneF, induces Th1 lymphocyte responses that confer host protection against C. neoformans (Murphy et al, 1998;Nichols et al, 2002). In contrast, immunization with heat-killed cryptococci does not protect mice and may even accelerate disease progression (Murphy et al, 1998;Nichols et al, 2002).…”

Stimulation via Toll‐like receptor 9 reduces Cryptococcus neoformans‐induced pulmonary inflammation in an IL‐12‐dependent manner

“…Moreover, a protective human vaccine against this pathogen is not available. An immune response to C. neoformans can be induced in mice by injecting heat‐killed yeast or cryptococcal filtrate antigen (CneF) with Freund's complete adjuvant 17. Immunization with heat‐killed cryptococci has produced variable degrees of protection depending on the method of delivery 18, 19.…”