Oroesophageal candidiasis is lethal for transgenic mice with combined natural killer and T-cell defects

Germfree transgenic epsilon 26 (Tgepsilon26) mice, which express the full-length human CD3epsilon gene, have combined defects in natural killer (NK) cells and T cells were found to be extremely susceptible to oroesophageal (palate, tongue, esophagus) and gastric (cardia-antrum section) candidiasis. The gnotobiotic Tgepsilon26 mice die, apparently from severe oroesophageal candidiasis, within 2-4 weeks after their alimentary tracts are colonized with Candida albicans. The Tgepsilon26 mice manifest resistance to acute systemic candidiasis (intravenous injection) and to systemic candidiasis of endogenous origin for the first 2 weeks after their alimentary tracts are colonized with C. albicans. Granulocyte depletion data suggest that granulocytes, in the absence of functional NK cells and T cells, can protect Tgepsilon26 mice from acute systemic candidiasis and from systemic candidiasis of endogenous origin, for at least 14 days after alimentary tract colonization. Granulocytes and macrophages, in the absence of NK cells and T cells, are unable to protect Tgepsilon26 mice from lethal oroesophageal candidiasis and systemic candidiasis of endogenous origin which was evident in moribund Tgepsilon26 mice 2-4 weeks after colonization. Thus, non-T cells (i.e., NK cells) and T cells play important roles in resistance to oroesophageal and systemic (acute and of endogenous origin) candidiasis.

Continuous stimulation by normal luminal bacteria is essential for the development and perpetuation of colitis in Tg(epsilon26) mice

BACKGROUND & AIMS

Normal resident bacteria are required for development of colitis in several rodent models. We determined whether bacterial stimulation is necessary for both induction and perpetuation of mucosal inflammation and T-cell activation in Tg(epsilon26) mice, in which transplantation of wild-type bone marrow (BM-->Tg(epsilon26)) causes colitis under specific pathogen-free (SPF) conditions.

METHODS

BM from (C57BL/6 X CBA/J) F1 mice was transplanted into germfree (GF) or SPF Tg(epsilon26) mice. Mesenteric lymph node (MLN) cells from these mice were then transferred into SPF or GF recipients. Colitis and activation of MLN cells were measured by histologic scores, membrane marker analysis, and intracellular cytokine staining. Cytokine secretion by MLN cells stimulated by anti-CD3 or by luminal or epithelial antigens was measured by ELISA.

RESULTS

Colitis did not develop when BM was transferred into GF recipient mice (BM-->GF Tg(epsilon26)). T lymphocytes that secreted interferon gamma upon activation were present in the MLN of BM-->GF Tg(epsilon26) mice, albeit in lower frequency than in control BM-->SPF Tg(epsilon26) mice. Furthermore, transfer of MLN cells from BM-->SPF Tg(epsilon26) mice into SPF Tg(epsilon26) recipients induced active colitis, but not if the same cells were transferred into GF Tg(epsilon26) recipients. Although CD4 T cells were detected in the colonic mucosa of GF recipients, no inflammation was observed for at least 31 weeks. In a reciprocal experiment, MLN cells from BM-->GF Tg(epsilon26) mice without colitis transferred disease to SPF Tg(epsilon26) recipients within 2-4 weeks.

CONCLUSIONS

Activated T cells are present in the mucosa of BM-->GF Tg(epsilon26) mice but are incapable of inducing disease unless colonic bacteria are present. Moreover, pathogenic T cells require the continuous presence of colonic bacteria to sustain colitis.

Helicobacter hepaticus does not induce or potentiate colitis in interleukin-10-deficient mice

Helicobacter hepaticus has been reported to induce colitis, hepatitis, and hepatocellular carcinoma in several different murine models. The aim of this study was to determine if H. hepaticus will cause colitis in monoassociated mice lacking the interleukin-10 gene (IL-10(-/-) mice) and potentiate colitis in specific-pathogen-free (SPF) IL-10(-/-) mice. Germfree IL-10(-/-) mice on either a mixed (C57BL/6 x 129/Ola) or inbred (129/SvEv) genetic background were monoassociated with H. hepaticus ATCC 51448 by oral feeding and rectal enemas. In a second experiment, germfree IL-10(-/-) mice were colonized with stool from SPF mice that harbored or did not harbor endogenous H. hepaticus. After 7 to 9 weeks of colonization, weight loss and mortality were assessed, the colon was isolated for histology and IL-12 secretion, and mesenteric lymph node cells were assessed for T-cell activation markers. It was found that IL-10(-/-) mice monoassociated with H. hepaticus for up to 16 weeks showed almost no histologic colitis or increased IL-12 production. SPF IL-10-knockout mice had no significant difference in weight loss, mortality rate, histologic scores, colonic IL-12 secretion, or T-cell activation with or without H. hepaticus. We conclude that H. hepaticus does not induce or potentiate disease in our IL-10(-/-) mice and therefore is not required to induce colitis in genetically susceptible hosts.

Effects of probiotic bacteria on humoral immunity to Candida albicans in immunodeficient bg/bg-nu/nu and bg/bg-nu/+ mice

Germfree beige-nude ( bg/bg-nu/nu) and beige-heterozygous ( bg/bg-nu/+) mice were colonized with a pure culture of Candida albicans or with a probiotic bacterium (Lactobacillus acidophilus, Lactobacillus reuteri, Lactobacillus casei, or Bifidobacterium infantis). Probiotic-colonized mice were subsequently challenged orally with C. albicans. The effect of prior colonization with probiotic bacteria on the antibody responses of the immunodeficient mice to alimentary tract colonization with C. albicans was compared to the antibody responses of the gnotobiotic mice colonized only with C. albicans. This study demonstrated that, although the probiotic bacteria did not induce a vigorous antibody response to their own antigens, they altered the antibody responses of mice to C. albicans. In T cell competent bg/bg-nu/+mice, B. infantis enhanced and focused IgG1, IgG2A, and IgA responses to C. albicans antigens. Some of the probiotic bacteria also enhanced the IgG1 and IgG2A antibody responses of bg/bg-nu/nu mice to C. albicans antigens. This study not only shows the value of gnotobiotic animal models in demonstrating that probiotic bacteria can affect the capacity of mice to form antibodies to C. albicans, but it also points out their usefulness in comparing the capacity of different probiotic bacteria to produce beneficial health effects in mice.

Cytokine and endothelial cell adhesion molecule expression in interleukin-10-deficient mice

The objectives of this study were to quantify cytokine mRNA levels and endothelial cell adhesion molecule message and protein expression in healthy wild-type and interleukin-10-deficient (IL-10(-/-)) mice that develop spontaneous and chronic colitis. We found that colonic message levels of IL-1, IL-6, tumor necrosis factor-alpha, interferon-gamma, lymphotoxin-beta, and transforming growth factor-beta were elevated in colitic mice 10- to 35-fold compared with their healthy wild-type controls. In addition, colonic message levels of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) were found to be increased 10-, 5-, and 23-fold, respectively, in colitic IL-10(-/-) mice compared with their wild-type controls. Immunoradiolabeling as well as immunohistochemistry revealed large and significant increases in vascular surface expression of colonic ICAM-1, VCAM-1, and MAdCAM-1 in the mucosa as well as the submucosa of the colons of colitic mice. These data are consistent with the hypothesis that deletion of IL-10 results in the sustained production of proinflammatory cytokines, leading to the upregulation of adhesion molecules and infiltration of mononuclear and polymorphonuclear leukocytes into the cecal and colonic interstitium.

Probiotic effects of feeding heat-killed Lactobacillus acidophilus and Lactobacillus casei to Candida albicans-colonized immunodeficient mice

Probiotic bacteria can protect immunodeficient mice from orogastric candidiasis but cause some pathology of their own. Severely immunodeficient patients may be at risk if fed viable probiotics, so this study evaluated the probiotic potential of nonviable probiotic bacteria to protect immunodeficient mice from Candida albicans infections. Heat-killed probiotic bacteria were fed to gnotobiotic bg/bg-nu/nu and bg/bg-nu/+ mice to ascertain if they could protect the mice from mucosal and systemic candidiasis. Both heat-killed Lactobacillus acidophilus (HKLA) and heat-killed Lactobacillus casei (HKLC), in comparison to control mice not fed the probiotic bacteria but challenged (oral) with C. albicans, suppressed the severity of orogastric candidiasis in bg/bg-nu/nu mice at 2 weeks after colonization with C. albicans, inhibited disseminated candidiasis in C. albicans-colonized bg/bg-nu/+ mice at 4 weeks after colonization, and suppressed the number of viable C. albicans in the alimentary tract. HKLA, but not HKLC, treatment inhibited disseminated candidiasis in bg/bg-nu/nu mice at 2 weeks after oral challenge and enhanced the proliferative responses of splenocytes from C. albicans-colonized bg/bg-nu/+ mice to C. albicans antigens. Neither HKLA nor HKLC were able to prolong the survival of gnotobiotic bg/bg-nu/nu mice after oral challenge with C. albicans. These results demonstrate that heat-killed lactobacilli can induce some (limited) protection (probiotic effect) against candidiasis in mice.

Disparate requirement for T cells in resistance to mucosal and acute systemic candidiasis

Although highly susceptible to orogastric candidiasis, T-cell receptor delta- and alpha-chain knockout mice, deficient in gammadelta and alphabeta T cells, respectively, were found to be resistant to disseminated candidiasis of endogenous origin and to acute systemic candidiasis (resulting from intravenous injection).

Unaltered phenotype, tissue distribution and function of Valpha14(+) NKT cells in germ-free mice

The expression pattern of mouse CD1d and the tissue distribution of CD1d-restricted Valpha14-Jalpha281 NKT cells suggest that the liver and the marginal zone of the spleen might be preferred sites of activation of this potent innate pathway of early cytokine secretion. Because these tissues are particularly involved with the filtration of blood-borne pathogens, and because NKT cells with an activated / memory phenotype accumulate over the first weeks of life and their CD1 ligands bind microbial glycolipids, it has been hypothesized that expansion of the NKT cell subset may be driven by exposure to the microbial environment. To test this hypothesis, we analyzed the frequency, surface phenotype and functional properties of NKT cells in normal and in germ-free C57BL / 6 mice. Surprisingly, we found that the NKT cell subset develops in the presence or absence of a microbial environment. Although these results do not rule out the possibility that NKT cells exert a protective function against some microbial agents, they demonstrate that non microbial ligands, possibly self-antigens are sufficient for the generation, maturation and peripheral accumulation of NKT cells.

Unaltered phenotype, tissue distribution and function of Valpha14(+) NKT cells in germ-free mice

The expression pattern of mouse CD1d and the tissue distribution of CD1d-restricted Valpha14-Jalpha281 NKT cells suggest that the liver and the marginal zone of the spleen might be preferred sites of activation of this potent innate pathway of early cytokine secretion. Because these tissues are particularly involved with the filtration of blood-borne pathogens, and because NKT cells with an activated / memory phenotype accumulate over the first weeks of life and their CD1 ligands bind microbial glycolipids, it has been hypothesized that expansion of the NKT cell subset may be driven by exposure to the microbial environment. To test this hypothesis, we analyzed the frequency, surface phenotype and functional properties of NKT cells in normal and in germ-free C57BL / 6 mice. Surprisingly, we found that the NKT cell subset develops in the presence or absence of a microbial environment. Although these results do not rule out the possibility that NKT cells exert a protective function against some microbial agents, they demonstrate that non microbial ligands, possibly self-antigens are sufficient for the generation, maturation and peripheral accumulation of NKT cells.

Mucosal and systemic candidiasis in IL-8Rh-/- BALB/c mice

Germ-free BALB/c mice, genetically engineered to be deficient for interleukin-8 (IL-8) receptor homolog (IL-8Rh-/-), were more susceptible to gastric candidiasis after oral challenge and to acute systemic candidiasis after intravenous challenge than IL-8Rh+/+ controls. In comparison to IL-8Rh+/+ mice, the IL-8Rh-/- mice had slower influx of polymorphonuclear neutrophils (PMN) into Candida albicans-infected tissues and a lower percentage of PMN in peritoneal exudate cells (PEC) elicited with heat-killed C. albicans. PEC from IL-8Rh-/- mice exhibited less luminol-dependent chemiluminescence in response to C. albicans and did not kill C. albicans hyphae as well as PEC from IL-8Rh+/+ mice. C. albicans-colonized IL-8Rh-/- mice showed no histological evidence of systemic candidiasis. These results suggest a role for the IL-8Rh in murine resistance to gastric and acute systemic candidiasis, but not in resistance to systemic candidiasis of endogenous origin.

The role of environmental antigens in the spontaneous development of autoimmunity in MRL-lpr mice

It has been proposed that the "normal" stimulation of the immune system that occurs from interactions with environmental stimuli, whether infectious or dietary, is necessary for the initiation and/or continuation of autoimmunity. We tested this hypothesis by deriving a group of MRL-lpr mice into a germfree (GF) environment. At 5 mo of age, no differences between GF and conventional MRL-lpr mice were noted in lymphoproliferation, flow cytometric analysis of lymph node cells (LN), or histologic analysis of the kidneys. Autoantibody levels were comparably elevated in both groups. A second experiment tested the role of residual environmental stimuli by contrasting GF mice fed either a low m.w., ultrafiltered Ag-free (GF-AF) diet or an autoclaved natural ingredient diet (GF-NI). At 4 mo of age, both groups showed extensive lymphoproliferation and aberrant T cell formation, although the GF-AF mice had approximately 50% smaller LNs compared with sex-matched GF-NI controls. Autoantibody formation was present in both groups. Histologic analysis of the kidneys revealed that GF-AF mice had much lower levels of nephritis, while immunofluorescence analysis demonstrated no difference in Ig deposits but did reveal a paucity of C3 deposition in the kidneys of GF-AF mice. These data do not support a role for infectious agents in the induction of lymphoproliferation and B cell autoimmunity in MRL-lpr mice. Furthermore, they suggest that autoantibodies do not originate from B cells that were initially committed to exogenous Ags. They do suggest a possible contributory role for dietary exposure in the extent of lymphoproliferation and development of nephritis in this strain.

IL-2-deficient mice raised under germfree conditions develop delayed mild focal intestinal inflammation

Interleukin-2 (IL-2) amplifies immune stimuli and influences B cell differentiation. IL-2-deficient mice spontaneously develop intestinal inflammation if raised under specific pathogen-free (SPF) conditions. We quantitatively determined the aggressiveness and kinetics of gastrointestinal and hepatic inflammation in the presence or absence of viable bacteria in IL-2-deficient mice. Breeding colonies were maintained under SPF and germfree (GF) conditions. Intestinal tissues, serum, and mesenteric lymph nodes were obtained from mice at different ages for blind histological scoring, immunoglobulin measurements, mucosal T cell infiltration, and cytokine secretion. GF IL-2 -/- mice developed mild, focal, and nonlethal intestinal inflammation with delayed onset, whereas the more aggressive inflammation in SPF IL-2 -/- mice led to their death between 28 and 32 wk. Periportal hepatic inflammation was equal in the presence or absence of bacterial colonization. Intestinal immunoglobulin secretion decreased significantly by 13 wk of age in IL-2 -/- mice in both GF and SPF environments. In contrast to other genetically engineered rodents, IL-2 -/- mice develop mild focal gastrointestinal and active portal tract inflammation in the absence of viable bacteria.

Expression of the neutrophil chemokine KC in the colon of mice with enterocolitis and by intestinal epithelial cell lines: effects of flora and proinflammatory cytokines

IL-10 plays an important role in preventing excessive inflammation to the normal flora in the intestinal lumen. The purpose of this study was to compare the effect of normal flora on inflammation in mice in which the IL-10 gene was disrupted. IL-10 knock-out mice housed in germfree conditions remained healthy while those housed in conventional conditions developed colitis after weaning, suggesting that IL-10 inhibits the adverse responses to luminal Ag. Crypt abscesses were present in virtually all of the diseased animals as evidenced by flattening of the epithelial cells and a large number of neutrophils in the lumen of the crypt. Since KC is a chemokine that is capable of recruiting neutrophils in mice, mRNA and protein for KC was measured. Increased levels of both KC mRNA and protein were detected in the colon of diseased mice. To determine whether the epithelial cells were capable of synthesizing KC and contributing to neutrophil accumulation in the crypts, a murine intestinal epithelial cell line (Mode-K) was shown to express mRNA and protein for KC. Two cytokines induced in association with colitis in these mice, TNF-alpha and IFN-gamma, increased the expression of KC mRNA and protein in murine epithelial cells. However, IL-10 was incapable of decreasing the induction of KC, even though the cells expressed the IL-10 receptor. These results suggest that the neutrophil chemokine KC is produced by gastrointestinal epithelial cells in response to inflammatory mediators that are expressed following exposure to normal flora in animals lacking IL-10.

Early resistance of interleukin-10 knockout mice to acute systemic candidiasis

In contrast to immunocompetent controls, interleukin-10 (IL-10) knockout (KO) mice eliminated an experimental intravenous inoculation with Candida albicans from their kidneys. Improved clearance of C. albicans from the kidneys of IL-10 KO mice was evident at 24 h after intravenous challenge with the fungus. Conversely, mice with a deletion of the IL-4 cytokine gene were more susceptible to systemic candidiasis than were immunocompetent controls. The hyperresistance of IL-10 KO mice to acute systemic candidiasis did not seem to correlate with nitric oxide-mediated immunity, but rather, it appeared to be associated with more efficient effector function of innate cells, possibly neutrophils. In support of the latter hypothesis, we observed that neutrophils from IL-10 KO mice were more efficient at killing C. albicans blastoconidia and hyphae than were neutrophils from immunocompetent control mice. Neither IL-10 KO nor IL-4 KO mice that were monoassociated with C. albicans for 4 weeks showed any histologic evidence of systemic candidiasis of endogenous origin. In contrast to systemic candidiasis, we observed no significant (P < 0.05) differences in susceptibility among IL-10 KO, IL-4 KO, and wild-type (immunocompetent) mice to orogastric candidiasis. Our results suggest that IL-10 exerts a negative effect on the early, innate response to acute systemic candidiasis; however, in comparison to immunocompetent control (wild-type) mice, neither IL-10 nor IL-4 deficiency enhanced susceptibility to orogastric candidiasis.

Susceptibility of immunodeficient gene-knockout mice to urinary tract infection

PURPOSE

Clinical and experimental evidence indicates that mucosal immunity to urinary tract infection involves B and T-cell functions. The present study was conducted to assess the susceptibility of immunocompetent and immunodeficient mice with genetically engineered deletions in T and B-cell functions to experimentally induced urinary tract infections (UTI) with Escherichia coli.

MATERIALS AND METHODS

Interferon-gamma (IFN-gamma), interleukin-4 (IL-4), IL-10, inducible nitric oxide synthase, T cell receptor (TCR) delta-chain and JHD B cell-deficient gene knockout mice and their immunocompetent controls were challenged with uropathogenic Escherichia coli. The bladders and kidneys were cultured for viable E. coli at time intervals after intraurethral challenge to assess susceptibility to an experimentally induced UTI.

RESULTS

Knockout mice with gammadelta-T cell or IFN-gamma deficiencies were more susceptible to UTI than immunocompetent mice or mice with immunodeficiencies in IL-10, IL-4, inducible nitric oxide synthase or antibody production (JHD).

CONCLUSIONS

These data support an important role for gammadelta-T cells and IFN-gamma in resistance to UTI in mice.

Variable biotherapeutic effects of Lactobacillus acidophilus isolates on orogastric and systemic candidiasis in immunodeficient mice

Two commercially available isolates of Lactobacillus acidophilus (NCFM and LA-1) were compared for their capacities to protect immunodeficient bg/bg-nu/un and bg/bg-nu/+ mice from candidiasis. L. acidophilus NCFM prolonged survival of adult and neonatal bg/bg-nu/nu mice, inhibited disseminated candidiasis in both mouse strains, suppressed weight loss associated with Candida albicans infection in bg/bg-nu/nu females, but did not decrease the severity or the incidente of orogastric candidiasis in gnotobiotic mice. L. acidophilus LA-1 suppressed numbers of C. albicans in the alimentary tracts of bg/bg-nu/+ mice and reduced the severity of mucosal candidiasis in bg/bg-nu/nuand bg/bg-nu/+ mice; however, L. acidophilus LA-1 did not improve the survival of bg/bg-nu/nu mice after oral challenge (colonization) with C. albicansand it was associated with lethality in gnotobiotic adult female bg/bg-nu/nu mice. These results demonstrate that the two isolates of L. acidophilus differed in their capacity to protect immunodeficient mice from candidiasis.

Biotherapeutic effects of Bifidobacterium spp. on orogastric and systemic candidiasis in immunodeficient mice

Two commercially available Bifidobacterium spp. (Bifidobacterium infantis and Bifidobacterium lactis) were compared for their capacities to protect immunodeficient bg/bg-nu/nuand bg/bg-nu/+mice from orogastric and lethal candidiasis. Both Bifidobacterium spp. prolonged the survival of Candida albicans-colonized adult and neonatal bg/bg-nu/numice. The bifidobacteria affected the production of antibodies to C. albicans, inhibited disseminated candidiasis, suppressed weight loss associated with C. albicans infection, inhibited the growth of C. albicans in the alimentary tract, inhibited systemic candidiasis of endogenous origin, and decreased the severity of gastric candidiasis in both mouse strains. B. infantis inhibited systemic candidiasis of endogenous origin better than B. lactis; however, B. lactis was significantly more effective at inhibiting C. albicans colonization of the alimentary tract, suppressing gastric candidiasis, and protecting bg/bg-nu/numice from lethal candidiasis than B. infantis. These results show that Bifidobacterium spp. can protect immunodeficient mice from candidiasis but different species manifest quantitative and qualitative differences in their probiotic and biotherapeutic effects.

Probiotic bacteria for prophylaxis and therapy of candidiasis

A good deal of data support a role for probiotic intestinal bacteria in the prophylaxis and therapy of candidiasis. Candida spp. are highly infectious eukaryotes that can colonize and infect humans and other warm-blooded mammals, worldwide. Although most humans manifest antibody- and cell-mediated immune responses to Candida antigens a large percentage of the human population is colonized with Candida spp. in their alimentary and vaginal tracts. The bacterial flora plays a very important probiotic role in the prophylaxis of candidiasis by suppressing the growth of Candida spp. on mucosal and cutaneous surfaces; however, the specific bacteria and the mechanisms they use to inhibit Candida spp. and candidiasis are still poorly understood. The increased incidence of Candida infections, their increasing resistance to antifungal antibiotics and the fact that vaccines to protect against candidiasis are not yet available (and may not work in immunodeficient, Candida-susceptible, patients) provides a strong impetus for new research efforts to explore the use of probiotic, anti- Candida intestinal bacteria for the prophylaxis and therapy of candidiasis.

Resident enteric bacteria are necessary for development of spontaneous colitis and immune system activation in interleukin-10-deficient mice

Mice with targeted deletion of the gene for interleukin-10 (IL-10) spontaneously develop enterocolitis when maintained in conventional conditions but develop only colitis when kept in specific-pathogen-free (SPF) environments. This study tested the hypothesis that enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice. IL-10-deficient mice were maintained in either SPF conditions or germfree conditions or were populated with bacteria known to cause colitis in other rodent models. IL-10-deficient mice kept in SPF conditions developed colitis in all segments of the colon (cecum and proximal and distal colon). These mice exhibited immune system activation as evidenced by increased expression of CD44 on CD4(+) T cells; increased mesenteric lymph node cell numbers; and increased production of immunoglobulin A (IgA), IgG1, and IL-12 p40 from colon fragment cultures. Mice populated with bacterial strains, including Bacteroides vulgatus, known to induce colitis in other rodent models had minimal colitis. Germfree IL-10-deficient mice had no evidence of colitis or immune system activation. We conclude therefore that resident enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice.

Candidiasis in interferon-gamma knockout (IFN-gamma-/-) mice

Germ-free C57BL/6 x 129 interferon-gamma knockout (IFN-gamma(-/-)) mice and their immunocompetent (+/-, +/+) counterparts were colonized with a pure culture of Candida albicans to assess their natural susceptibility to mucosal and systemic candidiasis of endogenous origin. Colonization with a pure culture of C. albicans was not lethal for adult or neonatal IFN-gamma(-/-) gnotobiotic mice over the 15-week study. The IFN-gamma(-/-) mice were more susceptible to gastric (cardia-antrum section), anorectal, and acute systemic (intravenous challenge) candidiasis than immunocompetent controls, and some IFN-gamma(-/-) mice developed intestinal adenomas after colonization with C. albicans. The enhanced susceptibility of IFN-gamma(-/-) mice, compared with immunocompetent controls, may be associated with a poor proliferative response of spleen cells to C. albicans antigens and a T helper 2 (IgG1) serum antibody response to C. albicans antigens. Thus, IFN-gamma is important for murine resistance to gastric, anorectal, and acute systemic candidiasis.

Time course and host responses to Escherichia coli urinary tract infection in genetically distinct mouse strains

Recurrent urinary tract infections (UTIs) are a significant clinical problem for many women; however, host susceptibility factors have not been completely defined. The mouse model of induced UTI provides an experimental environment in which to identify specific host characteristics that are important in initial bacterial colonization of the urinary tract and in resolution of an infection. This study examined initial susceptibility, bacterial clearance, and host defense mechanisms during induction and resolution of Escherichia coli UTIs in genetically distinct strains of mice. Of the ten inbred strains tested, six (BALB/c, C3H/HeN, C57BL/6, DBA.1, DBA.2, and AKR) showed progressive resolution of bladder infections over a 14-day period. A constant, low-level bladder infection was observed in SWR and SJL mice. High bladder infection levels persisted over the 14-day study period in C3H/HeJ and C3H/OuJ mice. Kidney infection levels generally correlated with bladder infection levels, especially in C3H/HeJ and C3H/OuJ mice, the two most susceptible strains, in which infections became more severe with time after challenge. The degree of inflammation in bladder and kidneys, as well as antibody-forming cell responses, positively correlated with infection intensity in all strains except C3H/HeJ, which had minimal inflammation despite high infection levels. These results demonstrate two important aspects of host defense against UTI. First, the innate immune response to an infection in the bladder or kidneys consists primarily of local inflammation, which is followed by an adaptive response characterized in part by an antibody response to the infecting bacteria. Second, a UTI will be spontaneously resolved in most cases; however, in mice with specific genetic backgrounds, a UTI can persist for an extended length of time. The latter result strongly suggests that the presence or absence of specific host genes will determine how effectively an E. coli UTI will be resolved.

Biotherapeutic effects of probiotic bacteria on candidiasis in immunodeficient mice

Four species of probiotic bacteria were assessed for their capacities to protect athymic bg/bg-nu/nu and euthymic bg/bg-nu/+ mice from mucosal and systemic candidiasis. Each bacterial species and Candida albicans colonized the gastrointestinal tracts of both strains of mice. The presence of probiotic bacteria (Lactobacillus acidophilus, Lactobacillus reuteri, Lactobacillus casei GG, or Bifidobacterium animalis) in the gastrointestinal tracts prolonged the survival of adult and neonatal bg/bg-nu/nu mice compared to that of isogenic mice colonized with C. albicans alone. The incidence of systemic candidiasis in bg/bg-nu/nu mice was significantly reduced by each of the four probiotic bacterial species. The numbers of C. albicans present in the alimentary tracts of euthymic bg/bg-nu/+ mice were significantly reduced by L. casei GG and B. animalis. None of the probiotic bacteria species completely prevented mucosal candidiasis, but B. animalis reduced its incidence and severity. Probiotic bacteria also modulated antibody- and cell-mediated immune responses to C. albicans. The prolonged survival of mice, decreased severity of mucosal and systemic candidiasis, modulation of immune responses, decreased number of C. albicans in the alimentary tract, and reduced numbers of orogastric infections demonstrated not only that probiotic bacteria have biotherapeutic potential for prophylaxis against and therapy of this fungal disease but also that probiotic bacteria protect mice from candidiasis by a variety of immunologic (thymic and extrathymic) and nonimmunologic mechanisms in this model.

Colonization of congenitally immunodeficient mice with probiotic bacteria

We assessed the capacity of four probiotic bacteria (Lactobacillus acidophilus, Lactobacillus reuteri, Lactobacillus casei GG, and Bifidobacterium animalis) to colonize, infect, stimulate immune responses in, and affect the growth and survival of congenitally immunodeficient gnotobiotic beige-athymic (bg/bg-nu/nu) and beige-euthymic (bg/bg-nu/+) mice. The bacteria colonized and persisted, in pure culture, in the alimentary tracts of both mouse strains for the entire study period (12 weeks). Although all adult and neonatal beige-euthymic mice survived probiotic colonization, some infant mortality occurred in beige-athymic pups born to mothers colonized with pure cultures of L. reuteri or L. casei GG. The probiotic bacteria manifested different capacities to adhere to epithelial surfaces, disseminate to internal organs, affect the body weight of adult mice and the growth of neonatal mice, and stimulate immune responses. Although the probiotic species were innocuous for adults, these results suggest that caution and further studies to assess the safety of probiotic bacteria for immunodeficient hosts, especially neonates, are required.

Macrophages in resistance to candidiasis

Candida albicans, an increasingly common opportunistic pathogenic fungus, frequently causes disease in immunodeficient but not immunocompetent hosts. Clarifying the role of the phagocytic cells that participate in resistance to candidiasis not only is basic to understanding how the host copes with this dimorphic pathogen but also will expedite the development of innovative prophylactic and therapeutic approaches for treating the multiple clinical presentations that candidiasis encompasses. In this review, we present evidence that a diverse population of mononuclear phagocytes, in different states of activation and differentiation and from a variety of host species, can phagocytize C. albicans blastoconidia via an array of opsonic and nonopsonic mechanisms and can kill C. albicans blastoconidia and hyphae by means of oxygen-dependent and -independent mechanisms. Reactive nitrogen intermediates should now be added to the well-established candidacidal reactive oxygen intermediates of macrophages. Furthermore, what were thought to be two independent pathways, i.e., nitric oxide and superoxide anion, have now been shown to combine to form a potent macrophage candidacidal molecule, peroxynitrite. In contrast to monocytes and neutrophils, which are important in resistance to early stages of C. albicans infections, more differentiated macrophages activated by cytokines such as gamma interferon participate in the acquired resistance of hosts with C. albicans-specific, cell-mediated immunity. Evidence presented in this review demonstrates that mononuclear phagocytes, in some instances in the absence of other professional phagocytes such as neutrophils, play an import role in resistance to systemic and mucosal candidiasis.

Vaginal mucosal immunization for recurrent urinary tract infection: phase II clinical trial

PURPOSE

Decreased local immunity to uropathogenic bacteria may be a factor predisposing women to recurrent urinary tract infections. Our phase I study demonstrated the safety of a multi-strain vaccine administered as a vaginal suppository. A phase II study was conducted to determine vaccine efficacy.

MATERIALS AND METHODS

A total of 91 women susceptible to recurrent urinary tract infections was entered into the study and the courses were analyzed in a randomized, double-blind, placebo controlled trial of vaginal mucosal immunization. Subjects received 3 vaginal suppositories at weekly intervals. Depending on the treatment group each suppository contained 1 of 2 vaccine doses or suppository material only. Each patient was followed for 5 months to record infection episodes, and obtain urine, vaginal irrigates and serum to measure immunological responses.

RESULTS

Immunogen treated women who were off antibiotic prophylaxis throughout the study had a significant delay in interval to reinfection during the first 8 weeks compared to women receiving placebo. Mean interval until reinfection was delayed from 8.7 weeks for placebo treated to 13 weeks for vaccine treated women. Immunological responses in serum, urine and vaginal fluid were variable. No serious adverse effects were observed.

CONCLUSIONS

These data demonstrate that vaginal mucosal immunization can enhance resistance to urinary tract infections in susceptible patients.

B cell-independent selection of memory T cells after mucosal immunization with Candida albicans

B cell-deficient mice have normal T cell responses to Ags inoculated systemically; however, it is not known whether they can mount systemic and mucosal T cell responses to Ags through normally B cell-enriched gastrointestinal mucosae. Mucosal colonization of germfree, B cell-deficient J(H)D mice with the pathogenic gastrointestinal fungus, Candida albicans selected splenic CD4+ and CD8+ TCR alphabeta memory T cells, as indicated by 1) increased numbers of splenic CD4+ and CD8+ TCR alphabeta expressing T cells of the CD45RB(low) CD44(high) phenotype, 2) early expansion followed by progressive decrease in the number of splenic CD4+ and CD8+ TCR alphabeta T cells, and 3) concomitant increases in the percentage of apoptosis and proliferation in the latter subsets. Although i.v. challenge of germfree or conventional J(H)D mice with C. albicans did not increase apoptosis or induce changes in the number of splenic memory T cells, i.v. challenge of mucosally immunized germfree J(H)D mice led to further proliferation and expansion of activated splenic CD4+ and CD8+ TCR alphabeta thymic-educated memory T cells, which were first evoked by mucosal immunization. Oral colonization with C. albicans also increased the number of gammadelta and thymic and extrathymic alphabeta T cells in gastrointestinal mucosae. In conclusion, our results are the first strong evidence that thymic and extrathymic T cells participate in mucosal immunity to C. albicans in the absence of B cells; however, CD4+ and thymic-educated CD8+ TCR alphabeta memory subsets evoked by mucosal, but not parenteral (i.v.), challenge contribute to protective immunity to systemic candidiasis.

B cell-independent selection of memory T cells after mucosal immunization with Candida albicans

B cell-deficient mice have normal T cell responses to Ags inoculated systemically; however, it is not known whether they can mount systemic and mucosal T cell responses to Ags through normally B cell-enriched gastrointestinal mucosae. Mucosal colonization of germfree, B cell-deficient J(H)D mice with the pathogenic gastrointestinal fungus, Candida albicans selected splenic CD4+ and CD8+ TCR alphabeta memory T cells, as indicated by 1) increased numbers of splenic CD4+ and CD8+ TCR alphabeta expressing T cells of the CD45RB(low) CD44(high) phenotype, 2) early expansion followed by progressive decrease in the number of splenic CD4+ and CD8+ TCR alphabeta T cells, and 3) concomitant increases in the percentage of apoptosis and proliferation in the latter subsets. Although i.v. challenge of germfree or conventional J(H)D mice with C. albicans did not increase apoptosis or induce changes in the number of splenic memory T cells, i.v. challenge of mucosally immunized germfree J(H)D mice led to further proliferation and expansion of activated splenic CD4+ and CD8+ TCR alphabeta thymic-educated memory T cells, which were first evoked by mucosal immunization. Oral colonization with C. albicans also increased the number of gammadelta and thymic and extrathymic alphabeta T cells in gastrointestinal mucosae. In conclusion, our results are the first strong evidence that thymic and extrathymic T cells participate in mucosal immunity to C. albicans in the absence of B cells; however, CD4+ and thymic-educated CD8+ TCR alphabeta memory subsets evoked by mucosal, but not parenteral (i.v.), challenge contribute to protective immunity to systemic candidiasis.

Importance of beta2-microglobulin in murine resistance to mucosal and systemic candidiasis

beta2-Microglobulin knockout (beta2m-/-) mice, which lack major histocompatibility complex class I expression and are deficient in CD8alpha/beta T-cell receptor alpha/beta (TcRalpha/beta) T cells, were as resistant to systemic (intravenous) challenge with Candida albicans as immunocompetent controls. Conversely, the beta2m-/- mutant mice were susceptible to systemic candidiasis of endogenous origin despite the induction of C. albicans-specific antibody and cell-mediated immune responses after colonization with a pure culture of C. albicans. Despite some superficial and transient infections of tongues and esophagi (detected by histology) at 1 to 2 weeks after oral colonization and gastric infections (cardia-antrum section) which were observed at 10 to 12 weeks after oral challenge, C. albicans-colonized beta2m-/- mice showed an overall resistance to candidiasis in other mucosal and cutaneous tissues. These data suggest that immune defects that accompany the loss of beta2-microglobulin play an important role in murine resistance to gastric and disseminated candidiasis of endogenous (intestinal tract) origin and that innate immunity and CD4 TcRalpha/beta as well as CD8alpha/alpha TcRalpha/beta (or -gamma/delta) T cells play an important role in resistance to systemic, cutaneous, and nongastric mucosal tissues.

Human HLA-B27 gene enhances susceptibility of rats to oral infection by Listeria monocytogenes

Germfree rats transgenic for the human genes HLA-B27 and beta 2-microglobulin were colonized with hemolysin-positive (Hly+) or hemolysin-negative (Hly-) strains of Listeria monocytogenes. HLA-B27 rats were very susceptible to infection with Hly+ L monocytogenes none survived beyond 6 days. Conversely, nontransgenic control rats survived alimentary tract colonization with the Hly+ strain, and both transgenic and nontransgenic rats survived colonization with the Hly- strain of L monocytogenes. After colonization with Hly+ L monocytogenes, both transgenic and nontransgenic rats developed severe bowel inflammation which consisted histologically of microab scesses, granulomatous lesions, and ulcers; however, whereas the transgenic rats died within 6 days, only very mild intestinal lesions were seen in nontransgenic rats 10 to 42 days after colonization. Liver and splenic lesions were small and transient in nontransgenic rats. Transgenic and nontransgenic control rats infected with Hly- Listeria developed mild transient diarrhea but showed no histological changes in the intestine. This study thus documents an association between a particular bacterial product (hemolysin produced by L monocytogenes) and the induction of severe inflammatory disease and death in rats expressing HLA-B27 and beta 2-microglobulin.

B cell knockout mice are resistant to mucosal and systemic candidiasis of endogenous origin but susceptible to experimental systemic candidiasis

Germfree J(H)D mice, which lack functional B cells and antibodies, were as resistant to orogastric and disseminated candidiasis of endogenous origin as were immunocompetent controls. Newborn J(H)D mice, in contrast to adult mice, were resistant to alimentary tract colonization by Candida albicans for 5-7 days after birth. C. albicans-colonized J(H)D mice were more resistant to intravenous challenge with C. albicans and had greater splenocyte proliferative responses to C. albicans antigens than did germfree mice or conventional controls. Thus, innate and acquired T cell-mediated immune responses induced after oral immunization are sufficient to protect J(H)D mice from mucosal and systemic candidiasis of endogenous origin; however, functional B cells may be required to protect mice from a primary intravenous challenge with C. albicans.

Normal luminal bacteria, especially Bacteroides species, mediate chronic colitis, gastritis, and arthritis in HLA-B27/human beta2 microglobulin transgenic rats

Genetic and environmental factors are important in the pathogenesis of clinical and experimental chronic intestinal inflammation. We investigated the influence of normal luminal bacteria and several groups of selected bacterial strains on spontaneous gastrointestinal and systemic inflammation in HLA-B27 transgenic rats. Rats maintained germfree for 3-9 mo were compared with littermates conventionalized with specific pathogen-free bacteria. Subsequently, germfree transgenic rats were colonized with groups of five to eight bacteria that were either facultative or strictly anaerobic. Transgenic germfree rats had no gastroduodenitis, colitis, or arthritis, but developed epididymitis and dermatitis to the same degree as conventionalized rats. Colonic proinflammatory cytokine expression was increased in transgenic conventionalized rats but was undetectable in germfree and nontransgenic rats. Colitis progressively increased over the first 4 wk of bacterial exposure, then plateaued. Only transgenic rats colonized with defined bacterial cocktails which contained Bacteroides spp. had colitis and gastritis. Normal luminal bacteria predictably and uniformly induce chronic colonic, gastric and systemic inflammation in B27 transgenic F344 rats, but all bacterial species do not have equal activities.

Peroxynitrite contributes to the candidacidal activity of nitric oxide-producing macrophages

Nitric oxide (NO) is associated with functions as diverse as peristalsis, blood flow, neuroendosecretion, visual transduction, smooth muscle relaxation, and microbial killing (H. H. W. H. Schmidt and V. Walter, Cell 78:919-925, 1994). Despite the well-established role of NO in macrophage candidacidal activity (E. Cenci, L. Romani, A. Mancacci, R. Spaccapelo, E. Schiaffella, P. Puccetti, and F. Bistoni, Eur. J. Immunol. 23:1034-1038, 1993; J. Jones-Carson, A. Vazquez-Torres, H. Van der Heide, R. D. Wagner, T. Warner, and E. Balish, Nature Med. 1:552-557, 1995; and A. Vazquez-Torres, J. Jones-Carson, T. Warner, and E. Balish, J. Infect. Dis. 172:192-198, 1995), NO is not directly candidacidal for Candida albicans (A. Vazquez-Torres, J. Jones-Carson, and E. Balish, Infect. Immun. 63:1142-1144, 1995). Because macrophages can produce both NO and superoxide anion (02-), we postulated that peroxynitrite (ONOO-), a product of the dilution-limited reaction of NO and O2-, is the candidacidal molecule of activated macrophages. We now report that ONOO-, in addition to being candidacidal in vitro, is responsible for the candidacidal activity of NO-producing macrophages. ONOO- synthesis by NO-producing macrophages was triggered by two independent mechanisms: one was nonopsonic and dependent on fungal cell wall glucan moieties, and the other was dependent on opsonic antibodies. As we have demonstrated for the pathogenic fungus C. albicans, ONOO- may also be the molecule that enables macrophages to kill other microbes that are resistant to both O2- and NO.

Oral immunization of mice against candidiasis

Oral immunization with live Candida albicans evoked antibody- and cell-mediated immune responses in gnotobiotic C.B-17 and BALB/c mice. No deaths or systemic candidiasis of endogenous origin were evident in these C. albicans-colonized (pure culture) mice. Histologic examination showed minimal to no infection of the stomach, esophagus, or tongue by C. albicans. Not only were orally immunized mice more resistant to systemic candidiasis (intravenous challenge) than were germfree (nonimmunized) controls, but immunity could be transferred to susceptible mice with immune spleen cells. Oral immunization elicited a Th1-type response in spleen cells and a Th2 response in Peyer's patch lymphocytes. The alimentary tracts of these orally immunized mice remained chronically colonized with C. albicans in spite of the presence of both antibody- and cell-mediated immune responses to C. albicans.

Western blot analysis of anti-Escherichia coli serum immunoglobulins in women susceptible to recurrent urinary tract infections

The basis for increased susceptibility of some women to recurrent urinary tract infections (UTIs) is not clear; increased susceptibility may be due to host factors that promote increased colonization of the vaginal and bladder mucosa with uropathogens or to decreased immune responses to uropathogens. Anti-Escherichia coli antibody specificities in sera from UTI patients and controls were comprehensively assessed to determine whether UTI-susceptible and -nonsusceptible women differed in their capacities to make antibodies to individual E. coli antigens. Sera were analyzed by one-dimensional Western blots using antigens prepared from uropathogenic E. coli. The results showed that sera from subjects without a history of recurrent UTIs contained IgG antibodies to specific E. coli antigens more often than did sera from UTI-susceptible patients. These data suggest that hyporesponsiveness to specific E. coli antigens may be linked to increased UTI susceptibility in some women.

Nitric oxide enhances resistance of SCID mice to mucosal candidiasis

The capacity of macrophages from SCID and C.B-17 mice to kill Candida albicans via a nitric oxide (NO)-dependent pathway and the contribution of NO in resistance to mucosal candidiasis were assessed. In vitro, an inhibitor of NO synthase (NOS) reduced the candidacidal activity and nitrite-producing capacity of activated resident peritoneal macrophages from immunocompetent C.B-17 and immunodeficient SCID mice. In vivo, stomachs from gnotobiotic SCID mice that were colonized with a pure culture of C. albicans had low-grade infections and expressed inducible NOS (iNOS) mRNA. C. albicans-monoassociated SCID mice treated with an inhibitor of NOS had more severe orogastric candidiasis than controls. These data suggest that NO contributes to the candidacidal capacity of activated macrophages from C.B-17 and SCID mice and that NO synthesized by iNOS may contribute to the resistance of SCID mice to mucosal candidiasis.

Gamma delta T cell-induced nitric oxide production enhances resistance to mucosal candidiasis

Despite the prevalence of gamma delta T cells in mucosae that are typically colonized by Candida albicans, little is known of the possible role of these cells in resistance to candidiasis. A sharp increase in the number of gamma delta T cells and macrophages following intraperitoneal inoculation of mice with C. albicans led us to examine the role of these cells in the immune response to C. albicans. We show that the gamma delta T cells enhance macrophage nitric oxide (NO) production and anti-candida activity, in vitro. We also propose that the gamma delta T cells regulate macrophage function during candidiasis in vivo as well, because depletion of these cells abrogated inducible NO synthase expression in mucosae and enhanced murine susceptibility to candidiasis.

Defective killing of Candida albicans hyphae by neutrophils from beige mice

The candidacidal activity of neutrophils from BALB/c, C.B-17 +/+, C.B-17 scid/scid, scid/scid-bg/bg, C57BL/6 bg/+, C57BL/6 bg/bg, NIH III bg/bg-nu/+, and bg/bg-nu/nu mice was assessed. Killing of blastoconidia was moderately deficient with neutrophils from 2 strains of homozygous beige mice; however, neutrophils from all homozygous beige strains had a significantly decreased capacity to kill Candida albicans hyphae. This is the first demonstration of a decreased capacity of beige mouse neutrophils to kill C. albicans hyphae. The latter defect could be related to the enhanced susceptibility of beige mice to candidiasis.

Pulmonary alveolar proteinosis. A spontaneous and inducible disease in immunodeficient germ-free mice

Spontaneous pulmonary alveolar proteinosis (PAP), which resembles human PAP, was found in aging (35 to 40 weeks) germ-free SCID-beige (scid/scid-bg/bg) mice. Spontaneous PAP was not observed in germ-free SCID mice. We describe the induction of PAP in SCID mice monoassociated with a pure culture of Candida albicans for 15 to 40 weeks. The gastrointestinal tracts only are colonized, and disseminated or pulmonary candidiasis does not occur. Another spontaneous form of PAP, designated type II, was discovered in germ-free beige (bg/bg and bg/+) mice and in beige-nude (bg/bg-nu/nu) mice. In this form of PAP, macrophages appear to be unable to digest the ingested phospholipoprotein complex and then accumulate in the alveolar spaces. These murine models should prove useful in elucidating the relationships between immune deficiencies, infections, and cytokine regulation of granulocyte and macrophage production and function in pulmonary alveolar proteinosis.

Nitric oxide production does not directly increase macrophage candidacidal activity

Some activated murine macrophages produced nitrite but were unable to kill Candida albicans. Furthermore, a nitric oxide (NO) generator inhibited C. albicans growth but was not candidacidal. Our results suggest that NO is candidastatic and that No is not directly involved but is associated with or induces other macrophage candidacidal mechanisms.

The germfree state prevents development of gut and joint inflammatory disease in HLA-B27 transgenic rats

A number of inflammatory disease states occur with greatly increased frequency in individuals inheriting the human major histocompatibility complex class I allele HLA-B27. In a minority of cases, namely those with B27-associated reactive arthritis, there is good evidence that the disease state is triggered by infection with an enteric or genitourinary bacterial pathogen. For the majority of B27-associated disease, no definite pathogenetic role for bacteria has been established. However, in these latter cases intestinal inflammation can often be demonstrated, and it sometimes occupies a major part of the clinical picture. Rats transgenic for B27 are known to develop a disorder resembling B27-associated human disease, with prominent intestinal, joint, skin, and male genital inflammatory lesions. We report here that B27 transgenic rats raised in a germfree environment do not develop inflammatory intestinal or peripheral joint disease, whereas the skin and genital inflammatory lesions are unaffected by the germfree state. These findings support the concept that gut and joint inflammation are pathogenetically closely related, and they provide direct evidence that the commensal gut flora play an important role in the pathogenesis of B27-associated gut and joint inflammation.

Phase I clinical trial of vaginal mucosal immunization for recurrent urinary tract infection

In a phase I clinical trial to test safety and patient acceptance 25 women with a history of recurrent urinary tract infections but no identifiable anatomic abnormality received a multivalent vaccine instilled into the vagina. The vaccine contained 6 heat-killed Escherichia coli strains and 4 nonE. coli uropathogens. Only minimal adverse reactions were observed in the 5-month period following immunization. Total vaginal and urinary IgG and IgA increased significantly (p < 0.01 by repeated measures analysis of variance). Serum antibodies to some of the nonE. coli strains but not to the E. coli strains increased after vaginal immunization. While efficacy is yet to be shown, this study indicates that this vaginally applied urinary tract infection vaccine is well tolerated, and capable of increasing vaginal and urinary antibody.

The role of phagocytic cells in resistance to disseminated candidiasis in granulocytopenic mice

This study assessed the involvement of phagocytic cells in murine resistance to disseminated candidiasis of endogenous origin. SCID mice and their immunocompetent CB.17 (BALB/c) counterparts were colonized with a pure culture of Candida albicans and treated with an antigranulocyte monoclonal antibody (anti-Gr-1), polyinosinic:polycytidylic acid (poly[I.C]), or both to impair macrophage function in vivo. Candida-colonized SCID mice were more susceptible to disseminated candidiasis after treatment with anti-Gr-1 or poly(I.C) than were CB.17 mice. Histopathology of orogastric tissues demonstrated that combined treatments with anti-Gr-1 and poly(I.C) also enhanced the susceptibility of SCID and CB.17 mice to orogastric candidiasis. These data indicate that macrophages as well as granulocytes play an important role in host resistance to mucosal and disseminated candidiasis of endogenous origin.

Humoral and cellular immune responses to enolase after alimentary tract colonization or intravenous immunization with Candida albicans

Immune responses to defined antigens of the AIDS opportunistic pathogen Candida albicans that arise as a consequence of alimentary tract colonization or induced candidemia were assessed. Lymphocyte activation and antibody production to the abundant immunodominant antigen enolase were evident in germfree mice colonized with C. albicans. Lymphocytes from colonized or intravenously challenged mice responded to a recombinant C. albicans enolase fusion protein (EFP). The responses to EFP were significantly higher than the responses to a control protein, glutathione S-transferase. In immunoblotting experiments, enolase was the immunodominant humoral immunogen in these mice. These results demonstrate that enolase stimulates cellular and humoral responses and that specific immune responses to enolase are sensitive indicators of the presence of proliferating C. albicans in mice.

Candidacidal activity of macrophages from immunocompetent and congenitally immunodeficient mice

The chemotactic, phagocytic, and candidacidal activities of peritoneal exudate macrophages from immunocompetent heterozygous (bg/+) and immunodeficient homozygous (bg/bg, bg/bg-nu/+, and bg/bg-nu/nu) beige mice were assessed. Overall, macrophages from all strains of mice tested not only were able to migrate into the peritoneal cavity in response to several eliciting agents but showed a comparable capacity to phagocytize fluorescein isothiocyanate-labeled, heat-killed Candida albicans. However, some populations of peritoneal exudate macrophages from homozygous beige mice (e.g., thioglycollate-elicited) and resident peritoneal macrophages from bg/bg mice incubated in vitro with supernatants from concanavalin A-stimulated splenocytes had poorer candidacidal activity than did control macrophages from bg/+mice. Interferon-gamma enhanced the in vitro candidacidal activity of macrophages from homozygous and heterozygous beige mice. As indicated by inhibitors, poor macrophage candidacidal activity seemed to correlate better with deficient nitric oxide--than with superoxide anion-mediated killing. These data suggest that impaired candidacidal activity of macrophages from homozygous beige mice may explain their enhanced susceptibility to candidiasis.

Vaginal immunization of monkeys against urinary tract infection with a multi-strain vaccine

Cynomolgus monkeys were treated with a vaccine containing 10 heat-killed uropathogenic bacteria including 6 Escherichia coli strains. The multi-strain vaccine was administered either as a vaginal surface immunogen or intramuscularly. Following an induced E. coli cystitis, bladder infections were significantly reduced compared with controls at 1 and 2 weeks (intramuscular route) or 1 week (vaginal route) after UTI. This vaccine has been shown to be efficacious against cystitis in humans when given parenterally and has now proved efficacious in nonhuman primates by the vaginal mucosal route.

Enhancement of susceptibility of CB-17 mice to systemic candidiasis by poly(I . C)-induced interferon

Poly(I . C) enhanced the susceptibility of CB-17 (BALB/c) mice to acute systemic candidiasis. Poly(I . C), supernatants from poly(I . C)-treated macrophages, or alpha and beta interferons suppressed macrophage candidacidal activity in vitro. Thus, poly(I . C)-induced interferons may enhance the susceptibility of CB-17 mice to candidiasis by suppressing macrophage candidacidal activity in an autocrine fashion.

Resistance of SCID mice to Candida albicans administered intravenously or colonizing the gut: role of polymorphonuclear leukocytes and macrophages

SCID mice, which lack functional T and B cells, and their immunocompetent counterparts were treated with a monoclonal antibody to murine granulocytes (anti-Gr-1), silica, or carrageenan to assess the role of phagocytic cells (Polymorphonuclear leukocytes and macrophages) in resistance to candidiasis. SCID mice treated with anti-Gr-1 showed enhanced susceptibility to acute systemic candidiasis, disseminated candidiasis of endogenous origin, and orogastric candidiasis. Immunocompetent CB.17 and BALB/c mice treated with anti-Gr-1 showed enhanced susceptibility to acute systemic candidiasis but not to either orogastric or disseminated candidiasis of endogenous origin. Impairment of phagocytic cell functions with silica or carrageenan also enhanced the susceptibility of SCID mice to acute systemic candidiasis. These data in SCID and CB.17 mice support clinical studies in patients that point out the important role that granulocytes play in resistance to candidiasis. The resistance of granulocyte-depleted CB.17 mice to orogastric and disseminated candidiasis of endogenous origin also demonstrates that functional T and B cells play a role in controlling candidiasis.

Congenital immunodeficiencies in mice increase susceptibility to urinary tract infection

Severe combined immunodeficient (SCID), T cell deficient, and immunocompetent mice were challenged intravesically with viable uropathogenic Escherichia coli. In comparison to immunocompetent controls, SCID mice had significantly greater numbers of viable E. coli in their bladders and kidneys 7 days after inoculation. Splenic anti-E. coli antibody-forming cells (AFC) were virtually absent in SCID mice at 7.0 days after infection. Adoptive transfer of spleen cells from E. coli-immunized immunocompetent mice to SCID mice enhanced their resistance to urinary tract infection (UTI), as evidenced by lower bacterial counts in bladder and kidneys following an induced infection. Congenitally T cell deficient nude mice and immunocompetent heterozygous controls had equivalent bladder and kidney infection levels at 2 and 7 days after UTI. Immunocompetency thus appears to play a significant role in resistance to E. coli UTI in this animal model. Since mice deficient only in T cells did not show increased UTI susceptibility, T cell-independent antibody responses may be an important immunologic defense mechanism.

Mucosal and disseminated candidiasis in gnotobiotic SCID mice

The alimentary tracts of germ-free SCID (severe combined immunodeficient) mice were susceptible to colonization with Candida albicans. Large viable populations (10(6)-10(8) colony forming units g-1) of C. albicans, in pure culture, were present in all sections of the intestinal tract. Candida-colonized SCID mice, sacrificed at various time intervals over a 16 week study, manifested chronic superficial mucosal candidiasis of keratinized epithelial surfaces (tongue and stomach). Despite the continuous presence of large viable populations of C. albicans in their intestinal tract, only superficial mucosal candidiasis and no progressive disseminated candidiasis of endogenous origin was evident in these mice. Treatment with cyclophosphamide (100 mg kg-1, intraperitoneally) enhanced the susceptibility of SCID mice to mucosal (tongue and stomach) candidiasis. Gnotobiotic (C. albicans-colonized) SCID mice were also found to be as resistant as immunocompetent BALB/c mice to acute (intravenous challenge) renal candidiasis. Colonization of the alimentary tract with a bacterial flora appeared to enhance the resistance of SCID mice to disseminated candidiasis. This study demonstrates that innate immune mechanisms (phagocytic and/or NK cells), in the absence of functional T- and B-cells, play an important role in the resistance of SCID mice to mucosal and disseminated candidiasis of endogenous (intestinal tract) or acute (intravenous challenge) origin.

Poly(I.C)-induced interferons enhance susceptibility of SCID mice to systemic candidiasis

In the absence of any demonstrable T- or B-cell responses, gnotobiotic CB-17 SCID (severe combined immunodeficient) mice not only show innate resistance to acute systemic (intravenous challenge) candidiasis but also manifest innate resistance to systemic candidiasis of endogenous (gastrointestinal tract) origin. Poly(I. C), a potent inducer of interferons (IFNs) in vivo, enhanced the susceptibility of CB-17 SCID mice to acute systemic candidiasis and to systemic candidiasis of endogenous origin, as demonstrated by increased numbers of viable Candida albicans in internal organs after poly(I. C) treatment. The poly(I. C)-enhanced susceptibility of mice to candidiasis was abrogated by in vivo treatment with antibodies to IFN-alpha, -beta, and -gamma. In vivo depletion of natural killer cells from SCID mice did not significantly enhance their susceptibility to systemic candidiasis or abrogate poly(I. C)-enhanced susceptibility. In vivo and in vitro, treatment with poly(I. C) impaired the candidacidal and phagocytic activity of thioglycollate-elicited macrophages from SCID mice. Antibody to IFN-alpha/beta or IFN-beta alone interfered with the ability of poly(I. C) to impair the candidacidal activity of macrophages from SCID mice in vitro. These data suggest that poly(I. C)-induced interferons can impair the candidacidal activity of macrophages in SCID mice and decrease their innate resistance to acute systemic candidiasis and to systemic candidiasis of endogenous origin.