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1.  Cytokine profiles associated with induction of the anticryptococcal cell-mediated immune response. 
Infection and Immunity  1993;61(11):4750-4759.
Previous studies with a murine model have shown that immunization with cryptococcal culture filtrate antigen (CneF) emulsified in complete Freund adjuvant (CFA) induces two populations of anticryptococcal reactive CD4+ T cells. One population (TDH cells) transfers anticryptococcal delayed-type hypersensitivity (DTH), and the other population (Tamp cells) amplifies the anticryptococcal DTH response of given to recipient mice at the time of immunization of the recipient. Treatment of mice with cyclosporin A (CsA) ablates the induction of Tamp cells but not TDH cells. The present study focused on assessing the cytokines produced by spleen cells taken from CsA-treated and control (solvent-treated) mice at days 1, 2, 4, and 6 after immunization. Supernatants from the spleen cells cultured in vitro for 24 or 48 h in medium alone or with CneF, concanavalin A, or phorbol 12-myristate 13-acetate plus calcium ionophore were assessed for the presence of interleukin-2 (IL-2), gamma interferon (IFN-gamma), IL-4, IL-5, and tumor necrosis factor. Spleen cells from CneF-CFA-treated mice produced IL-2 and IFN-gamma, but not IL-4 or IL-5, constitutively and in response to CneF, indicating that CneF-CFA induces a Th1 response. Tumor necrosis factor was not produced. Anticryptococcal TDH cells developed in spleens in which there were low levels of IFN-gamma and IL-2 (CsA-treated, immunized mice), whereas anticryptococcal Tamp cells along with TDH cells matured in spleens in which production of IFN-gamma and IL-2 was high (solvent-treated, immunized mice). The data also suggest that IL-2 and IFN-gamma produced by Tamp cells early after adoptive transfer are influential in the development of the amplified anticryptococcal DTH response that has been observed in Tamp cell-recipient mice.
PMCID: PMC281230  PMID: 8406874
2.  Effects of Cryptococcus neoformans-specific suppressor T cells on the amplified anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1991;59(1):29-35.
Cell-mediated immunity is an important host resistance mechanism against Cryptococcus neoformans, the etiological agent of cryptococcosis. Previous studies from our laboratory have shown that the anticryptococcal cell-mediated immune response as measured by delayed-type hypersensitivity (DTH) is down-regulated by a cascade of antigen-specific T suppressor (Ts) cells. Recently, we have identified a population of CD4 T cells that up-regulate the anticryptococcal DTH response (Tamp cells). The Tamp cells are found in the spleens of donor mice at 6 days after immunization with cryptococcal antigen, and they amplify the anticryptococcal DTH response when transferred to syngeneic recipients at the time of immunization of the recipients. In this study, we determined the effects of C. neoformans-specific Ts cells on the induction of the Tamp cells in the Tamp cell-donor mice and on the induction and expression of the amplified anticryptococcal DTH response in the Tamp cell-recipient mice. When cryptococcal-specific Ts1 cells were given at the time of immunization of the Tamp cell-donor mice, induction of Tamp cells was inhibited. In contrast, when Ts1 cells were given at the time of adoptive transfer of Tamp cells, the recipients displayed amplified DTH responses, indicating that Ts1 cells do not affect the Tamp cells' function once the Tamp cells have been produced. C. neoformans-specific Ts2 cells given at the time of either immunization or footpad challenge of the Tamp cell-recipient mice did not alter, to any measurable extent, the amplified DTH response. These results indicate that in addition to amplifying the anticryptococcal DTH response, Tamp cells may protect the anticryptococcal TDH cells from suppression by C. neoformans-specific Ts cells, much like contrasuppressor cells do in other systems. However, further characterization of the Tamp cells revealed that they are not adherent to Viscia villosa lectin, indicating that the anticryptococcal Tamp cells do not have this characteristic in common with contrasuppressor cells of other antigen systems.
PMCID: PMC257701  PMID: 1824761
3.  Characterization of a cell population which amplifies the anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1990;58(2):393-398.
Cell-mediated immunity to Cryptococcus neoformans can be detected by delayed-type hypersensitivity (DTH) to a culture filtrate antigen of C. neoformans. Recently, we have identified a population of cells in spleens of mice immunized with cryptococcal antigen that, when transferred to recipient mice at the time of immunization, amplifies the anticryptococcal DTH response. If the cell donor mice are treated with cyclosporin A during induction of the anticryptococcal DTH response, the amplifier cells are not induced, whereas the cells which transfer DTH (TDH cells) are induced. The purpose of this study was to characterize the amplifier cells with respect to their surface and functional properties and, in so doing, determine whether or not the amplifier cells are analogous to long-lived memory cells. We demonstrated that the amplifier cells were nylon-wool-nonadherent, antigen-specific, CD4 (L3T4+ Lyt-2-) T lymphocytes which appear in the spleens of mice 5 days postimmunization with cryptococcal culture filtrate antigen in complete Freund adjuvant. The amplifier T (Tamp) cells are not considered to be memory cells because they are relatively short-lived, being present 14 but not 18 days after the stimulating immunization. Moreover, the amplified anticryptococcal DTH response does not fulfill the criteria of the typical secondary immune (anamnestic) response in that the amplified response does not appear early relative to the appearance of the primary anticryptococcal DTH response, and it does not persist longer than the primary DTH response. We speculate that Tamp cells are not long-lived memory cells but rather act in a T-helper cell capacity to amplify the anticryptococcal DTH response.
PMCID: PMC258468  PMID: 2105273
4.  Antigen-Induced Protective and Nonprotective Cell-Mediated Immune Components against Cryptococcus neoformans 
Infection and Immunity  1998;66(6):2632-2639.
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.
PMCID: PMC108249  PMID: 9596727
5.  Characterization of cellular infiltrates and cytokine production during the expression phase of the anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1993;61(7):2854-2865.
Cryptococcosis, an increasingly important opportunistic infection caused by the encapsulated yeast-like organism Cryptococcus neoformans, is limited by an anticryptococcal cell-mediated immune (CMI) response. Gaining a thorough understanding of the complex anticryptococcal CMI response is essential for developing means of controlling infections with C. neoformans. The murine cryptococcosis model utilizing footpad swelling to cryptococcal antigen (delayed-type hypersensitivity [DTH]) has proven to be a valuable tool for studying the induction and regulation of the anticryptococcal CMI response, but this technique has limitations with regard to evaluating the role of the final effector cells recruited by an ongoing CMI response. The purpose of this study was to assess the types of cells and cytokines induced into the site of cryptococcal antigen deposition in C. neoformans-infected and -immunized mice compared with those for control mice. We used a gelatin sponge implant model to examine the cells and cytokines present at the site of an anticryptococcal DTH response. Sponges implanted in infected mice and injected with cryptococcal culture filtrate antigen (CneF) 24 h before assessment had significantly increased numbers of infiltrating leukocytes compared with saline-injected sponges in the same animals. Exaggerated influxes of neutrophils and mononuclear cells were the major contributors to the increase in total numbers of cells in the DTH-reactive sponges. The numbers of CD4+ and LFA-1+ cells were found to be significantly increased in the CneF-injected sponges of infected and immunized mice over the numbers in control sponges. The numbers of large granular lymphocytes were also increased in DTH-reactive sponges compared with control sponges. Gamma interferon, interleukin 2 (IL-2), and IL-5 are clearly relevant cytokines in the anticryptococcal CMI response, since they were produced in greater amounts in the CneF-injected sponges from C. neoformans-infected and -immunized mice than in control sponges. IL-4 was not associated with the expression of DTH to cryptococcal antigen. The gelatin sponge model is an excellent tool for studying cells and cytokines involved in specific CMI responses.
PMCID: PMC280931  PMID: 8514388
6.  Differences in Components at Delayed-Type Hypersensitivity Reaction Sites in Mice Immunized with Either a Protective or a Nonprotective Immunogen of Cryptococcus neoformans 
Infection and Immunity  2002;70(2):591-600.
Cell-mediated immunity is the major protective mechanism against Cryptococcus neoformans. Delayed swelling reactions, i.e., delayed-type hypersensitivity (DTH), in response to an intradermal injection of specific antigen are used as a means of detecting a cell-mediated immune (CMI) response to the antigen. We have found previously that the presence of an anticryptococcal DTH response in mice is not always indicative of protection against a cryptococcal infection. Using one immunogen that induces a protective anticryptococcal CMI response and one that induces a nonprotective response, we have shown that mice immunized with the protective immunogen undergo a classical DTH response characterized by mononuclear cell and neutrophil infiltrates and the presence of gamma interferon and NO. In contrast, immunization with the nonprotective immunogen results in an influx of primarily neutrophils and production of tumor necrosis factor alpha (TNF-α) at the DTH reaction site. Even when the anticryptococcal DTH response was augmented by blocking the down-regulator, CTLA-4 (CD152), on T cells in the mice given the nonprotective immunogen, the main leukocyte population infiltrating the DTH reaction site is the neutrophil. Although TNF-α is increased at the DTH reaction site in mice immunized with the nonprotective immunogen, it is unlikely that TNF-α activates the neutrophils, because the density of TNF receptors on the neutrophils is reduced below control levels. Uncoupling of DTH reactivity and protection has been demonstrated in other infectious-disease models; however, the mechanisms differ from our model. These findings stress the importance of defining the cascade of events occurring in response to various immunogens and establishing the relationships between protection and DTH reactions.
PMCID: PMC127722  PMID: 11796587
7.  CTLA-4 Down-Regulates the Protective Anticryptococcal Cell-Mediated Immune Response 
Infection and Immunity  2000;68(8):4624-4630.
Cell-mediated immune (CMI) responses defined by delayed-type hypersensitivity (DTH) reactivity to cryptococcal culture filtrate antigen (CneF) can be either protective or nonprotective against an infection with Cryptococcus neoformans. The protective and nonprotective anticryptococcal DTH responses are induced by different immunogens and have differing activated-T-cell profiles. This study examined the effects of blockade of the interaction between cytotoxic T lymphocyte antigen 4 (CTLA-4) and its ligands B7-1 (CD80) and B7-2 (CD86) on the anticryptococcal DTH responses and protection. We found that CTLA-4 blockade at the time of immunization with the immunogen that induces the protective response, CneF, in complete Freund's adjuvant (CFA) or the immunogen that induces the nonprotective response, heat-killed cryptococcal cells (HKC), enhanced anticryptococcal DTH reactivity. In contrast, blocking CTLA-4 after the immune response was induced failed to enhance responses. Blockade of CTLA-4 in an infection model resulted in earlier development of the anticryptococcal CMI response than in control mice. Concomitant with increases in DTH reactivity in mice treated with anti-CTLA-4 Fab fragments at the time of immunization, there were decreases in cryptococcal CFU in lungs, spleens, and brains compared to controls. Blockade of CTLA-4 resulted in long-term protection, as measured by significantly increased survival times, only in mice given the protective immunogen, CneF-CFA. Anti-CTLA-4 treatment did not shift the response induced by the nonprotective immunogen, HKC, to a long-term protective one. Our data indicate that blockade of CTLA-4 interactions with its ligands may be useful in enhancing host defenses against C. neoformans.
PMCID: PMC98393  PMID: 10899865
8.  Clearance of Cryptococcus neoformans from immunologically suppressed mice. 
Infection and Immunity  1989;57(7):1946-1952.
To assess the effects of cryptococcal antigen-induced immunosuppression on a Cryptococcus neoformans infection, CBA/J mice were injected intravenously with saline or suppressive doses of cryptococcal antigen (CneF) at weekly intervals and were then infected with viable C. neoformans cells. By the second week after infection, the cryptococcal antigen-injected mice had suppressed anticryptococcal delayed-type hypersensitivity (DTH) responses compared with the responses of the saline-treated, infected control mice. In addition, the immunosuppressed mice had higher numbers of cryptococcal CFU cultured from their lungs, livers, spleens, lymph nodes, and brains than did the control animals. A direct correlation of suppression of the anticryptococcal DTH response and reduced clearance of cryptococci from tissues was also observed after mice were given a single intravenous injection of CneF and infected. To determine whether or not the cryptococcal antigen was specifically reducing the clearance of C. neoformans or had a more generalized effect, mice were injected with saline or suppressive doses of CneF, infected with Listeria monocytogenes, and then followed daily for 7 days for the clearance of L. monocytogenes from spleens and on day 7 for DTH reactivity to Listeria antigen. There were no differences between the saline- and CneF-treated mice with respect to anti-Listeria DTH responses or clearance of L. monocytogenes from spleens, indicating that CneF was not altering natural resistance mechanisms responsible for early clearance of L. monocytogenes, nor was the CneF influencing the induction of the acquired immune response which was responsible for the late clearance of the bacteria. Together, these data indicate that the specific suppression of this cell-mediated immune response induced by cryptococcal antigen reduces the ability of the animals to eliminate the homologous organism (C. neoformans) but not a heterologous infectious agent, such as L. monocytogenes.
PMCID: PMC313825  PMID: 2499541
9.  Cyclosporine A Impairs Nucleotide Binding Oligomerization Domain (Nod1)-Mediated Innate Antibacterial Renal Defenses in Mice and Human Transplant Recipients 
PLoS Pathogens  2013;9(1):e1003152.
Acute pyelonephritis (APN), which is mainly caused by uropathogenic Escherichia coli (UPEC), is the most common bacterial complication in renal transplant recipients receiving immunosuppressive treatment. However, it remains unclear how immunosuppressive drugs, such as the calcineurin inhibitor cyclosporine A (CsA), decrease renal resistance to UPEC. Here, we investigated the effects of CsA in host defense against UPEC in an experimental model of APN. We show that CsA-treated mice exhibit impaired production of the chemoattractant chemokines CXCL2 and CXCL1, decreased intrarenal recruitment of neutrophils, and greater susceptibility to UPEC than vehicle-treated mice. Strikingly, renal expression of Toll-like receptor 4 (Tlr4) and nucleotide-binding oligomerization domain 1 (Nod1), neutrophil migration capacity, and phagocytic killing of E. coli were significantly reduced in CsA-treated mice. CsA inhibited lipopolysaccharide (LPS)-induced, Tlr4-mediated production of CXCL2 by epithelial collecting duct cells. In addition, CsA markedly inhibited Nod1 expression in neutrophils, macrophages, and renal dendritic cells. CsA, acting through inhibition of the nuclear factor of activated T-cells (NFATs), also markedly downregulated Nod1 in neutrophils and macrophages. Silencing the NFATc1 isoform mRNA, similar to CsA, downregulated Nod1 expression in macrophages, and administration of the 11R-VIVIT peptide inhibitor of NFATs to mice also reduced neutrophil bacterial phagocytosis and renal resistance to UPEC. Conversely, synthetic Nod1 stimulating agonists given to CsA-treated mice significantly increased renal resistance to UPEC. Renal transplant recipients receiving CsA exhibited similar decrease in NOD1 expression and neutrophil phagocytosis of E. coli. The findings suggest that such mechanism of NFATc1-dependent inhibition of Nod1-mediated innate immune response together with the decrease in Tlr4-mediated production of chemoattractant chemokines caused by CsA may contribute to sensitizing kidney grafts to APN.
Author Summary
Patients who have received a kidney graft are treated with immunosuppressive drugs, such as the cyclosporine A (CsA). Transplanted patients under CsA are prone to bacterial infections. In this study, we used an experimental mouse model of kidney infection with Escherichia coli (E. coli) bacteria to study the effect of CsA. We show that CsA treatment of mice reduced their renal defense against E. coli. We found that CsA, in addition to its inhibitory action on the TLR4-mediated production of chemoattractant chemokines, also inhibited the expression of nucleotide-binding oligomerization domain 1 (Nod1), an intracellular receptor involved in the innate immune response against bacteria, in phagocytic cells. CsA acts by inhibiting the functions of the transcription factor NFAT. We show that NFAT is required for the proper expression of Nod1. Since Nod1 has already been reported to be involved in the phagocytic functions of polymorphonuclear neutrophils, we looked for and found a severe defect in neutrophil bacterial killing associated with reduced expression of Nod1 in both mice and patients treated by CsA. Interestingly, when mice treated with CsA are given synthetic molecules known to bind Nod1, this permitted the restoration of the Nod1 expression and renal defenses. This paper describes a novel mechanism which may explain, at least in part, why transplant patients receiving CsA have increased susceptibility to bacterial infection, and also provides a potential therapeutic strategy to restore renal antibacterial defenses.
PMCID: PMC3561241  PMID: 23382681
10.  Polysaccharide antigens of the capsule of Cryptococcus neoformans. 
Infection and Immunity  1994;62(5):1507-1512.
The major significance of the capsular polysaccharide of C. neoformans is its role in potentiating opportunistic infections by the yeast. It has the ability to exert a broad spectrum of influences on the immune response, from activation of phagocytic cells and complement components of the alternative pathway, to the induction of specific antibody, T-suppressor cells, DTH responses, and cytokines (51). These biological properties along with the serotype specificities are all determined by the physical properties and chemical structures of the polysaccharide antigens that compose the capsule. There is evidence not only for an association of lethal infections with serotype A in patients with advanced AIDS (34, 56), but also for a role for the capsule in directly influencing the infection of CD4+ cells by HIV (57). Together, these phenomena raise intriguing questions about the possible connection between the chemistry of these capsular antigens and cryptococcal infections in AIDS patients. One speculation is that AIDS creates the optimal physiological conditions for the establishment and spread of cryptococcosis. It has been observed that during the progression of AIDS there is a shift towards a T-2 response (14). This could lead to conditions that would inhibit the cellular immune responses that block dissemination of cryptococcal infections. Thus, an important consideration in the application of vaccine or immune modulation therapies in the treatment of cryptococcosis in AIDS victims would be the design of vaccines that could boost the T-1 immune response. It has been shown that the form and dose of an antigenic challenge can influence the induction of a T-1 or T-2 immune response (61). Recently, Murphy has reported that gamma interferon and interleukin 2 are up-regulated in the spleens of mice that produce anticryptococcal TDH and TAMP cells in response to immunogenic doses of cryptococcal culture filtrate antigen given with Freund's complete adjuvant (49). Perhaps purified cryptococcal antigens (e.g., MP) conjugated to an appropriate carrier or adjuvant could be used in therapeutic strategies to limit cryptococcosis in immunocompromised individuals. Future investigations of virulence and pathogenicity in the context of defined polysaccharide antigens from encapsulated strains of C. neoformans will contribute to a better understanding of the regulation of cryptococcal infection and immunity at the cellular and molecular levels.(ABSTRACT TRUNCATED AT 400 WORDS)
PMCID: PMC186341  PMID: 8168912
11.  Effects of first-order Cryptococcus-specific T-suppressor cells on induction of cells responsible for delayed-type hypersensitivity. 
Infection and Immunity  1985;48(2):439-445.
Cell-mediated immunity is an important aspect of host resistance against Cryptococcus neoformans. Using a CBA/J murine model, we demonstrated that injection of cryptococcal antigen (CneF) at dosages sufficient to stimulate the antigenemia observed in cryptococcosis patients induces specific T-cell-mediated suppression of the cryptococcal delayed-type hypersensitivity response. The purpose of this study was to establish whether Lyt 1+, first-order T-suppressor (Ts1) cells block the induction of T cells responsible for delayed-type hypersensitivity (TDH cells) or whether they function by inducing Lyt 2+, efferent suppressor (Ts2) cells. In one set of experiments, suppression was observed when Ts1 cells were adoptively transferred to recipient animals the day before, the day of, or the day after immunization; however, when Ts1 cells were transferred after TDH cells were present, no suppression occurred. In other experiments, putative TDH cells from lymph nodes (LN) or spleens were adoptively transferred from mice after immunization or after a suppressive dose of CneF or adoptive transfer of Ts1 cells and immunization. Delayed-type hypersensitivity could not be transferred with LN or spleen cells from mice receiving the suppressive dose of CneF or the Ts1 cells, even when the LN or spleen cells were treated with anti-Lyt 2.1 antibody and complement to remove any Ts2 cells. Delayed-type hypersensitivity was readily transferred with LN or spleen cells from immunized mice whether the cells were or were not treated with anti-Lyt 2 and complement. Furthermore, the cells in the tolerized LN cell pools responsible for suppression of TDH cell induction were Lyt 1+ 2-, I-J+ cells, which is the phenotype of the Ts1 cells. Taken together, these data indicate that Ts1 cells inhibit the induction of TDH cells. This finding, coupled with the previous demonstration that Ts1 cells or a Ts1 cell-derived soluble factor (TsF1) induces Ts2 cells, establishes that the cryptococcal Ts1 cells are bifunctional in the suppressive pathway.
PMCID: PMC261339  PMID: 3157646
12.  Characterization of a third-order suppressor T cell (Ts3) induced by cryptococcal antigen(s). 
Infection and Immunity  1987;55(7):1657-1662.
Previous studies from our laboratory have shown that a high dose of cryptococcal culture filtrate antigen (CneF) administered intravenously induces a complex suppressor cell cascade which down-regulates the cell-mediated immune response to Cryptococcus neoformans antigens. The primary objective of this investigation was to determine whether a suppressor cell induced by immunization is required for efferent suppression of the cryptococcal delayed-type hypersensitivity (DTH) response. Our approach to this problem was to immunize CBA/J mice with CneF emulsified in complete Freund adjuvant and then 6 days later to collect spleen cells from the immunized mice and adoptively transfer these cells along with C. neoformans-specific second-order suppressor T cells (Ts2) to naive syngeneic recipients at the time of footpad challenge of the recipients with CneF. To establish which populations of cells in the spleens of immunized mice play a suppressive role, mass cytolysis with specific antibodies and complement was performed before the spleen cells were transferred to naive animals. Since the phenotype of the cells responsible for the transfer of the cryptococcal DTH response had not been completely determined, we first demonstrated that the cells responsible for DTH were L3T4+ Lyt-2- cells. Subsequently, we established that a Thy-1+ L3T4- Lyt-2+ I-J+ cell population induced by immunization was required along with C. neoformans-specific Ts2 cells for efferent suppression of the cryptococcal DTH response. In addition, we demonstrated that the suppressor cells in the immune cell population were derived from cyclophosphamide-sensitive precursors. These data indicate that a third suppressor cell population is required for efferent suppression of the cryptococcal DTH response. As in the azobenzenearsonate and 4-hydroxy-3-nitrophenyl acetyl hapten suppressor models, the Ts2 cells in the circuit mediate their effects through this third suppressor component. Since the mode of induction and the phenotype of the third C. neoformans-specific suppressor cells are similar to those reported for Ts3 cells in other antigen-specific suppression models, we referred to this third suppressor cell in the C. neoformans-specific suppressor cell cascade as a Ts3 cell.
PMCID: PMC260574  PMID: 2954914
13.  Effects of Tumor Necrosis Factor Alpha on Dendritic Cell Accumulation in Lymph Nodes Draining the Immunization Site and the Impact on the Anticryptococcal Cell-Mediated Immune Response  
Infection and Immunity  2003;71(1):68-74.
Cell-mediated immune (CMI) responses and tumor necrosis factor alpha (TNF-α) have been shown to be essential in acquired protection against Cryptococcus neoformans. Induction of a protective anticryptococcal CMI response includes increases in dendritic cells (DC) and activated CD4+ T cells in draining lymph nodes (DLN). During the expression phase, activated CD4+ T cells accumulate at a peripheral site where cryptococcal antigen is injected, resulting in a classical delayed-type hypersensitivity (DTH) reaction. Induction of a nonprotective anticryptococcal CMI response results in no significant increases in the numbers of DC or activated CD4+ T cells in DLN. This study focuses on examining the role of TNF-α in induction of protective and nonprotective anticryptococcal CMI responses. We found that neutralization of TNF-α at the time of immunization with the protective immunogen (i) reduces the numbers of Langerhans cells, myeloid and lymphoid DC, and activated CD4+ T cells in DLN and (ii) diminishes the total numbers of cells, the numbers of activated CD4+ T cells, and amount of gamma interferon at the DTH reaction site. Although TNF-α neutralization during induction of the nonprotective CMI response had little effect on cellular and cytokine parameters measured, it did cause a reduction in footpad swelling when mice received challenge in the footpad. Our findings show that TNF-α functions during induction of the protective CMI response by influencing the accumulation of all three DC subsets into DLN. Without antigen stimulated DC in DLN, activated CD4+ T cells are not induced and thus not available for the expression phase of the CMI response.
PMCID: PMC143367  PMID: 12496150
14.  Regulation of cytokine production during the expression phase of the anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1994;62(7):2930-2939.
Effects of both positive and negative regulatory T cells on cellular infiltration and cytokine production during the expression phase of the anticryptococcal immune response were examined. Tamp cells, which are induced by cryptococcal antigen, significantly amplify the anticryptococcal delayed-type hypersensitivity response, whereas a cascade of T suppressor (Ts) cells inhibits the response and decreases the clearance of Cryptococcus neoformans during an infection. By using the gelatin sponge implantation model, we found that Tamp cells do not stimulate a significant increase in cellular infiltration into the sponges in response to cryptococcal antigen compared with that into delayed-type hypersensitivity-reactive sponges in immune control mice. However, Tamp cells do stimulate significant increases in the production of gamma interferon and interleukin-2 (IL-2) in the antigen-injected sponges over the level of the representative cytokine in antigen-injected sponges from the immune control mice. Likewise, Ts1 cells, induced with cryptococcal antigen, do not significantly affect antigen-induced cellular infiltration into sponges in immune mice. In contrast, decreased levels of gamma interferon and IL-2 are observed in antigen-injected sponges from Ts1-cell-recipient, immunized mice compared with those of the positive immune controls. The presence of either Tamp or Ts1 cells in immunized mice stimulates increased production of IL-5 but not IL-4 over that of the positive immune controls.
PMCID: PMC302900  PMID: 7911788
15.  Effects of immunization with Cryptococcus neoformans cells or cryptococcal culture filtrate antigen on direct anticryptococcal activities of murine T lymphocytes. 
Infection and Immunity  1995;63(5):1645-1651.
Immunizing CBA/J mice with intact Cryptococcus neoformans cells or with a cryptococcal culture filtrate antigen (CneF) induces an anticryptococcal delayed-type hypersensitivity response. Recently, it has been shown that two phenotypically different T-cell populations are responsible for delayed-type hypersensitivity reactivity in mice immunized with intact cryptococcal cells, whereas only one of those populations is present in mice immunized with soluble cryptococcal antigens in complete Freund's adjuvant (CFA). The purpose of this study was to determine if differences occur with regard to direct anticryptococcal activity between T-lymphocyte-enriched populations from mice immunized with intact viable or dead cryptococcal cells and similar cell populations from mice immunized with the soluble cryptococcal culture filtrate antigen, CneF, emulsified in CFA. The percentage of lymphocytes which form conjugates with C. neoformans and the percentage of cryptococcal growth inhibition in vitro are greater with T-lymphocyte-enriched populations from mice sublethally infected with C. neoformans or from mice immunized with intact heat-killed cryptococcal cells in the presence or absence of CFA than with lymphocyte populations from mice immunized with CneF-CFA. Enhanced anticryptococcal activity of T lymphocytes could be induced by immunizing mice with heat-killed C. neoformans cells of serotype A, B, C, or D as well as by immunizing with a similar preparation of an acapsular C. neoformans mutant but not by immunizing with CFA emulsified with CneF prepared from any one of the C. neoformans isolates. These data indicate that the soluble cryptococcal culture filtrate antigens do not induce the same array of functional T lymphocytes as whole cryptococcal cells.
PMCID: PMC173204  PMID: 7729868
16.  Differential Regulation of Immune Responses by Highly and Weakly Virulent Cryptococcus neoformans Isolates 
Infection and Immunity  1999;67(7):3601-3609.
Early inflammatory responses, delayed-type hypersensitivity (DTH) responses, and cytokine profiles were studied in mice infected by the pulmonary route with either a highly virulent isolate (NU-2) or a weakly virulent isolate (184A) of Cryptococcus neoformans. After infection, NU-2 remained in the lungs and the capsule became more pronounced during the first 24 h, whereas 184A induced an immediate inflammatory reaction and was rapidly cleared from the lungs. Cryptococcal antigen (GXM) appeared in sera early after infection with NU-2 and increased over the entire observation period. There was no detectable GXM in sera from 184A-infected mice. Both C. neoformans isolates induced anticryptococcal cell-mediated immune responses, but the responses had different profiles. DTH in NU-2-infected mice appeared at day 15 after infection and waned by day 21, whereas DTH in 184A-infected mice was present by day 5 and continued to increase. T helper 1 (Th1) cytokines (interleukin 2 [IL-2] and gamma interferon) were made by spleen cells early after infection with either isolate. NU-2-infected mice lost their ability to produce these cytokines, but 184A-infected mice retained it. IL-4, a Th2 cytokine, was not detected in infected mice. The regulatory cytokine IL-10 was made by spleen cells early but not later after infection with the highly virulent isolate and was not produced by spleen cells from 184A-infected mice. IL-10-deficient mice survived an NU-2 infection significantly longer than wild-type mice, suggesting that IL-10 is important in down-regulating the protective immune response. The induction of anergy appears to be responsible for the inability of NU-2-infected mice to control a C. neoformans infection.
PMCID: PMC116550  PMID: 10377145
17.  Immunoadsorption of Cryptococcus-specific suppressor T-cell factors. 
Infection and Immunity  1986;51(3):844-850.
In the murine cryptococcal suppressor cell circuit, two different T-cell suppressor factors, TsF1 and TsF2, have been identified which specifically suppress the delayed-type hypersensitivity (DTH) response to cryptococcal culture filtrate antigen (CneF). TsF1 is produced by a first-order T suppressor (Ts1) cell population and suppresses the afferent limb of the DTH response, whereas TsF2 is produced by a second-order T suppressor (Ts2) cell population and suppresses the efferent limb of the cryptococcal DTH response. The objective of this study was to ascertain whether TsF1 or TsF2 could bind to cryptococcal antigen. To assess this, adsorption of TsF1 and TsF2 was performed with heat-killed Cryptococcus neoformans cells and by solid-phase immunoadsorption (SPIA) on columns containing cryptococcal antigens, i.e., CneF covalently bound to Sepharose 4B. The suppressive effect of TsF1 was removed by adsorption with intact heat-killed cryptococci and by SPIA on CneF-Sepharose 4B. The binding of cryptococcal TsF1 to the cryptococcal SPIA column was shown to be specific since Sepharose 4B columns either coupled with Saccharomyces cerevisiae mannan or blocked with glycine did not adsorb the suppressor activity. In contrast, the suppressive component of TsF2 did not bind to heat-killed cryptococci, CneF-Sepharose 4B, S. cerevisiae mannan-Sepharose 4B, or glycine-Sepharose 4B columns. These results, together with the finding that cryptococcal antigen, anticryptococcal antibody, and C1q-binding immune complexes were not demonstrated in either TsF1 or TsF2, establish that TsF1 and TsF2 can be differentiated on the basis of their affinity for cryptococcal antigen.
PMCID: PMC260975  PMID: 2936685
18.  Age-Related Resistance of C57BL/6 Mice to Cryptococcus neoformans Is Dependent on Maturation of NKT Cells  
Infection and Immunity  2004;72(9):5175-5180.
Conflicting results have been reported regarding the ability of C57BL/6 mice to clear infections due to Cryptococcus neoformans. Examination of the various experimental protocols used suggested that C57BL/6 mice might develop the ability to resist infection as they mature. We analyzed the ability of C57BL/6 mice of different ages to respond to immunization with cryptococcal antigen or to clear a cryptococcal infection. Mice were immunized with a soluble cryptococcal culture filtrate antigen (CneF) emulsified in complete Freund's adjuvant (CneF-CFA). Delayed-type hypersensitivity (DTH) reactions elicited by the immunization were significantly stronger in 15-week-old C57BL/6 mice than in 7-week-old mice. Analysis of cryptococcal CFU 8 weeks following intratracheal infection of 7-week-old mice or 15-week-old mice revealed a relative inability of the younger animals to control the infection. Six-week-old immunized and infected mice cleared cryptococci from brain, spleen, and liver in a manner similar to that of immunized and infected 15-week-old mice. However, the older mice cleared cryptococci much more efficiently from the lungs. The possible role for NKT cells was determined by passive transfer of thymocytes from 10-week-old mice (containing mature NKT cells) or 2-week-old mice (containing immature NKT cells) to 6-week-old mice. The 10-week-old thymocytes significantly enhanced the ability of the mice to develop a DTH response after immunization with CneF-CFA, while animals treated with 2-week-old thymocytes did not improve their DTH response after immunization. The cells in the 10-week-old thymocyte population responsible for improvement of DTH responses were identified as being NK1.1 positive.
PMCID: PMC517463  PMID: 15322012
19.  Regulation of Cytokine Expression in Mice Immunized with Cryptococcal Polysaccharide, a Glucuronoxylomannan (GXM), Associated with Peritoneal Antigen-Presenting Cells (APC): Requirements for GXM, APC Activation, and Interleukin-12 
Infection and Immunity  2000;68(9):5146-5153.
Mice immunized with peritoneal exudate cells (PEC; used as antigen-presenting cells [APC]) that are pulsed ex vivo with cryptococcal capsular polysaccharide, a glucuronoxylomannan (GXM), exhibit increased survival times and delayed-type hypersensitivity reactions when they are infected with Cryptococcus neoformans. These responses are GXM specific. The present study revealed that GXM-APC immunization enhanced development of anticryptococcal type-1 cytokine responses (interleukin-2 [IL-2] and gamma interferon) in mice infected with C. neoformans. The enhancement was not GXM specific, because immunization with GXM-APC and immunization with APC alone had similar effects. GXM-APC (or APC) immunization caused small increases in the expression of type-2 cytokines (IL-4 and IL-5), but the increases were not always statistically significant. IL-10 levels were not regulated by immunization with GXM-APC or APC. GXM-APC prepared with PEC harvested from mice injected with complete Freund's adjuvant (CFA) enhanced type-1 cytokine responses, while GXM-APC prepared with PEC induced with incomplete Freund's adjuvant were ineffective. The CFA-induced PEC had an activated phenotype characterized by increased numbers of F4/80+ cells that expressed CD40, B7-1, and B7-2 on their membranes. The immunomodulatory activity of the CFA-induced APC population was not attributed to their production of IL-12 because GXM-APC prepared with peritoneal cells harvested from IL-12 knockout mice or their wild-type counterparts were equally effective in augmenting the type-1 response. Blocking of IL-12 in the recipients of GXM-APC early after APC infusion revealed that early induction of IL-12 secretion was not responsible for the immunomodulatory response elicited by GXM-APC. These data, considered together with previously reported data, reveal that the protective activity of GXM-APC immunization involves both antigen-specific and nonspecific activities of GXM-APC.
PMCID: PMC101763  PMID: 10948138
20.  Mannoprotein from Cryptococcus neoformans Promotes T-Helper Type 1 Anticandidal Responses in Mice  
Infection and Immunity  2002;70(12):6621-6627.
We previously demonstrated that mannoprotein (MP) from Cryptococcus neoformans (CnMP) stimulates interleukin-12 production by human monocytes, thus fostering a T-helper type 1 (Th1) protective anticryptococcal response. In this paper we show that CnMP was also able to induce a Candida albicans-directed protective Th1 response. This was demonstrated for mice immunized with CnMP by induction of a delayed-type hypersensitivity (DTH) reaction to C. albicans MP (CaMP) as well as induction of gamma interferon production by CD4+ and CD8+ splenic T cells stimulated in vitro with CaMP. CnMP-immunized mice were also partially protected from lethal systemic challenge with C. albicans, as shown by prolonged median survival times and decreased fungal burden in the kidney. Much evidence supports the validity of these cross-reactive and functional Th1 responses: (i) a non-cross-reactive C. albicans antigen, such as enolase, did not produce a DTH response to CaMP; (ii) passive adoptive transfer of T cells primed with CnMP induced a DTH reaction; (iii) C. neoformans extract elicited a DTH response to CaMP; and (iv) a monoclonal antibody (7H6) directed against a major and immunodominant T-cell-stimulatory 65-kDa MP (MP65) of C. albicans also recognized discrete 100-kDa constituents of C. neoformans extracts, as well as secretory constituents of the fungus. These results suggest the presence of common Th1 antigenic determinants in the mannoproteic material of C. neoformans and C. albicans epitopes, which should be considered in devising common strategies for immunoprophylactic or immunotherapeutic control of the fungi.
PMCID: PMC132998  PMID: 12438334
21.  An early component of delayed-type hypersensitivity mediated by T cells and mast cells 
The Journal of Experimental Medicine  1983;157(5):1604-1617.
In four different systems it was shown that murine delayed-type hypersensitivity (DTH) responses at 18-48 h were preceded by early 2-h responses. CBA mice immunized with picryl chloride, BDF1 mice immunized with oxazolone, BALB/c mice immunized with dinitrofluorobenzene, and C57BL/6 mice immunized with L5178Y lymphoma cells, and challenged with the appropriate specific antigen, all gave rise to expected 18-48 h delayed-in-time hypersensitivity reactions, but all of these responses were preceded by early hypersensitivity reactions that peaked at 2 h. These early 2-h reactions are transferable with T cells or with a T cell-derived, antigen-binding factor and are antigen-specific. The early and late components of DTH reactions are mast cell dependent since neither are elicited in mast cell deficient W/Wv or Sl/Sld mice. The T cell activity mediating the early component of DTH is demonstrable as early as 24 h after immunization, while the classical late component of DTH is not demonstrable until days 3-4. The difference in onset after immunization of the early and late components of DTH, and the different kinetics of these components in recipients of cell transfers that were challenged immediately or 24 h after transfer, led to the hypothesis that immunization for DTH leads to rapid induction in lymphoid organs of a certain population of T cells to produce an antigen-binding factor. This factor sensitizes peripheral tissues, probably mast cells, and local challenge with appropriate antigen leads to mast cell activation and release of the vasoactive amine serotonin, resulting in increased permeability of the local vasculature. This allows other circulating antigen-specific T cells, which are induced later after immunization, to enter the tissues and interact with antigen, resulting in production of chemoattractant lymphokines that recruit accessory leukocytes such as monocytes and polymorphs to enter the tissues via gaps between endothelial cells. These inflammatory cells, that are recruited to the site via two different T cell activities, constitute the characteristic infiltrate of DTH responses. Identification of an early 2-h component of DTH that is T cell- and mast cell-dependent provides evidence that the tissue- sensitizing, antigen-binding, T cell factor probably functions in vivo in the early phases of DTH responses.
PMCID: PMC2187022  PMID: 6602201
22.  Cyclosporin A differentially inhibits multiple steps in VEGF induced angiogenesis in human microvascular endothelial cells through altered intracellular signaling 
The immunosuppressive agent cyclosporin A (CsA), a calcineurin inhibitor which blocks T cell activation has provided the pharmacologic foundation for organ transplantation. CsA exerts additional effects on non-immune cell populations and may adversely effect microvascular endothelial cells, contributing to chronic rejection, a long-term clinical complication and significant cause of mortality in solid-organ transplants, including patients with small bowel allografts. Growth of new blood vessels, or angiogenesis, is a critical homeostatic mechanism in organs and tissues, and regulates vascular populations in response to physiologic requirements. We hypothesized that CsA would inhibit the angiogenic capacity of human gut microvessels. Primary cultures of human intestinal microvascular endothelial cells (HIMEC) were used to evaluate CsA's effect on four in vitro measures of angiogenesis, including endothelial stress fiber assembly, migration, proliferation and tube formation, in response to the endothelial growth factor VEGF. We characterized the effect of CsA on intracellular signaling mechanisms following VEGF stimulation. CsA affected all VEGF induced angiogenic events assessed in HIMEC. CsA differentially inhibited signaling pathways which mediated distinct steps of the angiogenic process. CsA blocked VEGF induced nuclear translocation of the transcription factor NFAT, activation of p44/42 MAPK, and partially inhibited JNK and p38 MAPK. CsA differentially affected signaling cascades in a dose dependent fashion and completely blocked expression of COX-2, which was integrally linked to HIMEC angiogenesis. These data suggest that CsA inhibits the ability of microvascular endothelial cells to undergo angiogenesis, impairing vascular homeostatic mechanisms and contributing to the vasculopathy associated with chronic rejection.
PMCID: PMC441414  PMID: 15175101
23.  Identification and Cloning of a Cryptococcal Deacetylase That Produces Protective Immune Responses  
Infection and Immunity  2002;70(5):2383-2391.
Cell-mediated immunity plays a crucial role in host defenses against Cryptococcus (Filobasidiella) neoformans. Therefore, the identification of cryptococcal antigens capable of producing T-cell-mediated responses, such as delayed-type hypersensitivity (DTH) reactions, may be useful in the development of immune-based strategies to control cryptococcosis. In order to characterize DTH-producing antigens, culture supernatants from the unencapsulated Cap-67 strain were separated by anion-exchange chromatography. After further fractionation by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a purified protein with an apparent molecular mass of 25 kDa was found to produce DTH, as evidenced by increased footpad swelling in mice immunized with culture supernatants, relative to unimmunized mice. The 20-amino-acid N-terminal sequence of the 25-kDa protein was used to search data of the C. neoformans Genome Project. Based on the genomic DNA sequence, a DNA probe was used to screen a λ cDNA library prepared from strain B3501. Clones were isolated containing the full-length gene (d25), which showed homology with a number of polysaccharide deacetylases from fungi and bacteria. The recombinant d25 protein expressed in Escherichia coli was similar to the natural one in DTH-producing activity. Moreover, immunization with either the natural or the recombinant protein prolonged survival and decreased fungal burden in mice challenged with the highly virulent C. neoformans strain H99. In conclusion, we have described the first cryptococcal gene whose product, a 25-kDa extracellular polysaccharide deacetylase, has been shown to induce protective immunity responses.
PMCID: PMC127888  PMID: 11953374
24.  Suppression of hapten-specific delayed-type hypersensitivity responses in mice by idiotype-specific suppressor T cells after administration of anti-idiotypic antibodies 
Delayed-type hypersensitivity (DTH) responses specific for the phosphorylcholine (PC) hapten were induced in BALB/c mice by immunization with syngeneic peritoneal exudate cells (PEC) coupled with diazotized phenyl-phosphoryl-choline. PC-specific DTH responses were elicited in such immunized mice after footpad challenge with PC- derivatized syngeneic spleen cells. Moreover, PC-immune lymph node cells could passively transfer PC-specific DTH responses to naive BALB/c mice and it was possible to demonstrate that the cells responsible for such passively transferred responses were T lymphocytes. Because the T-15 idiotypic determinant displayed on the TEPC-15 PC-binding myeloma protein is known to be a dominant idiotype associated with anti-PC antibody responses in BALB/c mice, an analysis was made of the effects of anti-T-15 idiotypic antibodies on the induction and expression of murine PC-specific DTH responses. Repeated injections of anti-T-15 idiotypic antiserum, raised in A/J mice by immunization with TEPC-15 myeloma protein, into recipient BALB/c mice both immediately before and after sensitization with PC-PEC virtually abolished the development of PC-specific DTH responses. Although administration of anti-T-15 antiserum effectively inhibited the induction phase of PC-specific DTH responses, these anti-idiotypic antibodies had no suppressive activity at the effector phase of these responses. The inhibition observed with anti-T-15 antibodies was highly specific for the PC hapten, and for PC-specific DTH responses of BALB/c but not A/J mice. Studies were conducted to address the possibility that anti-Id treatment induced suppressor T lymphocytes capable of specifically inhibiting the activity of PC-specific T cells participating in DTH responses. The results demonstrate that idiotype- specific suppressor T cells are, indeed, induced by treatment with anti- Id; moreover, such suppressor T cells, once induced, are highly effective in abrogating both the induction and the effector phases of PC-specific T cell-mediated DTH responses in BALB/c mice.
PMCID: PMC2185684  PMID: 92519
25.  Differential Activation of Peritoneal Cells by Subcutaneous Treatment of Rats with Cryptococcal Antigens▿  
Previous studies in our laboratory have shown that the subcutaneous pretreatment of rats with heat-killed cells (HKC) of Cryptococcus neoformans emulsified in complete Freund adjuvant (CFA) promotes protective immunity against an intraperitoneal challenge with C. neoformans. In contrast, subcutaneous treatment with the capsular polysaccharide (PSC) emulsified in CFA exacerbates the cryptococcal infection. The purpose of this study was to analyze the mechanisms involved in these phenomena. Adherent peritoneal cells from rats treated with HKC-CFA showed upregulated ED2, CD80, and CD86 expression; an increase in the level of production of anticryptococcal metabolites; and the enhanced production of interleukin-12 (IL-12) in comparison with the findings for cells from rats treated with CFA-phosphate-buffered saline (PBS). Adherent peritoneal cells from rats treated with PSC-CFA, however, also presented upregulated ED2, CD80, and CD86 expression compared to the level of expression for peritoneal cells from controls, but these cells showed an increase in arginase activity and decreased levels of production of IL-12 and tumor necrosis factor (TNF) compared with the activity and levels of production by peritoneal cells from CFA-PBS-treated rats. In addition, treatment with HKC-CFA resulted in a rise in the phagocytic and anticryptococcal activities of adherent peritoneal cells compared to those for control rats. However, adherent peritoneal cells from rats treated with PSC-CFA presented a reduction in anticryptococcal activity in comparison with that for cells from animals treated with CFA-PBS. These results show the differential activation between adherent peritoneal cells from HKC-CFA- and PSC-CFA-treated rats, with this differential activation at the primary site of infection possibly being responsible, at least in part, for the phenomena of protection and exacerbation observed in our model.
PMCID: PMC2725545  PMID: 19494083

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