Direct microbicidal activity of cytotoxic T-lymphocytes

Imaging-Based Efficacy Evaluation of Cancer Immunotherapy in Engineered Tumor Platforms and Tumor Organoids

Cancer immunotherapy is used to treat tumors by modulating the immune system. Although the anticancer efficacy of cancer immunotherapy has been evaluated prior to clinical trials, conventional in vivo animal and endpoint models inadequately replicate the intricate process of tumor elimination and reflect human-specific immune systems. Therefore, more sophisticated models that mimic the complex tumor-immune microenvironment must be employed to assess the effectiveness of immunotherapy. Additionally, using real-time imaging technology, a step-by-step evaluation can be applied, allowing for a more precise assessment of treatment efficacy. Here, an overview of the various imaging-based evaluation platforms recently developed for cancer immunotherapeutic applications is presented. Specifically, a fundamental technique is discussed for stably observing immune cell-based tumor cell killing using direct imaging, a microwell that reproduces a confined space for spatial observation, a droplet assay that facilitates cell-cell interactions, and a 3D microphysiological system that reconstructs the vascular environment. Furthermore, it is suggested that future evaluation platforms pursue more human-like immune systems.

Immunoinformatic design of a putative multi-epitope vaccine candidate against Trypanosoma brucei gambiense

Human African trypanosomiasis (HAT) is a neglected tropical disease that is caused by flagellated parasites of the genus Trypanosoma. HAT imposes a significant socio-economic burden on many countries in sub-Saharan Africa and its control is hampered by several drawbacks ranging from the ineffectiveness of drugs, complex dosing regimens, drug resistance, and lack of a vaccine. Despite more than a century of research and investigations, the development of a vaccine to tackle HAT is still challenging due to the complex biology of the pathogens. Advancements in computational modeling coupled with the availability of an unprecedented amount of omics data from different organisms have allowed the design of new generation vaccines that offer better antigenicity and safety profile. One of such new generation approaches is a multi-epitope vaccine (MEV) designed from a collection of antigenic peptides. A MEV can stimulate both cellular and humoral immune responses as well as avoiding possible allergenic reactions. Herein, we take advantage of this approach to design a MEV from conserved hypothetical plasma membrane proteins of Trypanosoma brucei gambiense, the trypanosome subspecies that is responsible for the west and central African forms of HAT. The designed MEV is 402 amino acids long (41.5 kDa). It is predicted to be antigenic, non-toxic, to assume a stable 3D conformation, and to interact with a key immune receptor. In addition, immune simulation foresaw adequate immune stimulation by the putative antigen and a lasting memory. Therefore, the designed chimeric vaccine represents a potential candidate that could be used to target HAT.

Comparison of Therapeutic Antibiotics, Probiotics, and Synthetic CpG-ODNs for Protective Efficacy Against Escherichia coli Lethal Infection and Impact on the Immune System in Neonatal Broiler Chickens

The poultry industry needs alternatives to antibiotics, as there are growing public concerns about the emergence of antimicrobial resistance owing to antimicrobial use in animal production. We have reported that the administration of neonatal chicks with synthetic DNA oligodeoxynucleotides containing unmethylated cytosine guanine dinucleotide (CpG) motifs (CpG-ODN) can protect against bacterial pathogens in chickens. The objective of this study was to compare the immunoprotective effects of CpG-ODN and probiotics against Escherichia coli infection vs. commonly used therapeutic antibiotics. Day-old broiler chicks were divided into five groups (n = 35/group; 30 for the challenge experiment and 5 for the flow cytometry analysis). The chicks in Group 1 received a single dose of CpG-ODN by the intramuscular route on day 4 (D4) posthatch (PH), and Group 2 received drinking water (DW) with a probiotic product (D1-D15 PH, DW). The Group 3 chicks received tetracycline antibiotics during D9-D13 in DW; the Group 4 chicks got sodium sulfamethazine on D9, D10, and D15 PH in DW; and the Group 5 chicks were administered intramuscular (IM) saline D4 PH, DW. We challenged all the groups (n = 30/group) with E. coli (1 × 10⁵ or 1 × 10⁶ colony-forming units/bird) on D8 PH through the subcutaneous route. Our data demonstrated that the CpG-ODNs, but not the probiotics, could protect neonatal broiler chickens against lethal E. coli septicemia, as would the tetracycline or sodium sulfamethazine. The flow cytometry analysis (n = 5/group) revealed enrichment of immune cells in the CpG-ODN group and a marked decrease in macrophages and T-cell numbers in antibiotics-treated groups, indicating immunosuppressive effects. Our data showed that, like therapeutic antibiotics, CpG-ODNs reduced clinical signs, decreased bacterial loads, and induced protection in chicks against E. coli septicemia. Unlike therapeutic antibiotics-induced immunosuppressive effects, CpG-ODN caused immune enrichment by increasing chicken immune cells recruitment. Furthermore, this study highlights that, although therapeutic antibiotics can treat bacterial infections, the ensuing immunosuppressive effects may negatively impact the overall chicken health.

Zebrafish Syndromic Albinism Models as Tools for Understanding and Treating Pigment Cell Disease in Humans

Simple Summary

Zebrafish (Danio rerio) is an emerging model for studying many diseases, including disorders originating in black pigment cells, melanocytes. In this review of the melanocyte literature, we discuss the current knowledge of melanocyte biology relevant to understanding different forms of albinism and the potential of the zebrafish model system for finding novel mechanisms and treatments.

Abstract

Melanin is the pigment that protects DNA from ultraviolet (UV) damage by absorbing excess energy. Melanin is produced in a process called melanogenesis. When melanogenesis is altered, diseases such as albinism result. Albinism can result in an increased skin cancer risk. Conversely, black pigment cell (melanocyte) development pathways can be misregulated, causing excessive melanocyte growth that leads to melanoma (cancer of melanocytes). Zebrafish is an emerging model organism used to study pigment disorders due to their high fecundity, visible melanin development in melanophores (melanocytes in mammals) from 24 h post-fertilization, and conserved melanogenesis pathways. Here, we reviewed the conserved developmental pathways in zebrafish melanophores and mammalian melanocytes. Additionally, we summarized the progress made in understanding pigment cell disease and evidence supporting the strong potential for using zebrafish to find novel treatment options for albinism.

The Role of B-Cells and Antibodies against Candida Vaccine Antigens in Invasive Candidiasis

Systemic candidiasis is an invasive fungal infection caused by members of the genus Candida. The recent emergence of antifungal drug resistance and increased incidences of infections caused by non-albicans Candida species merit the need for developing immune therapies against Candida infections. Although the role of cellular immune responses in anti-Candida immunity is well established, less is known about the role of humoral immunity against systemic candidiasis. This review summarizes currently available information on humoral immune responses induced by several promising Candida vaccine candidates, which have been identified in the past few decades. The protective antibody and B-cell responses generated by polysaccharide antigens such as mannan, β-glucan, and laminarin, as well as protein antigens like agglutinin-like sequence gene (Als3), secreted aspartyl proteinase (Sap2), heat shock protein (Hsp90), hyphally-regulated protein (Hyr1), hyphal wall protein (Hwp1), enolase (Eno), phospholipase (PLB), pyruvate kinase (Pk), fructose bisphosphate aldolase (Fba1), superoxide dismutase gene (Sod5) and malate dehydrogenase (Mdh1), are outlined. As per studies reviewed, antibodies induced in response to leading Candida vaccine candidates contribute to protection against systemic candidiasis by utilizing a variety of mechanisms such as opsonization, complement fixation, neutralization, biofilm inhibition, direct candidacidal activity, etc. The contributions of B-cells in controlling fungal infections are also discussed. Promising results using anti-Candida monoclonal antibodies for passive antibody therapy reinforces the need for developing antibody-based therapeutics including anti-idiotypic antibodies, single-chain variable fragments, peptide mimotopes, and antibody-derived peptides. Future research involving combinatorial immunotherapies using humanized monoclonal antibodies along with antifungal drugs/cytokines may prove beneficial for treating invasive fungal infections.

Baseline iron status and presence of anaemia determine the course of systemic Salmonella infection following oral iron supplementation in mice

BACKGROUND

Iron deficiency anaemia (IDA) is a major health concern. However, preventive iron supplementation in regions with high burden of infectious diseases resulted in an increase of infection related morbidity and mortality.

METHODS

We fed male C57BL/6N mice with either an iron deficient or an iron adequate diet. Next, they received oral iron supplementation or placebo followed by intraperitoneal infection with Salmonella Typhimurium (S.Tm).

FINDINGS

We found that mice with IDA had a poorer clinical outcome than mice on an iron adequate diet. Interestingly, iron supplementation of IDA mice resulted in higher bacterial burden in organs and shortened survival. Increased transferrin saturation and non-transferrin bound iron in the circulation together with low expression of ferroportin facilitated the access of the pathogen to iron and promoted bacterial growth. Anaemia, independent of iron supplementation, was correlated with reduced neutrophil counts and cytotoxic T cells. With iron supplementation, anaemia additionally correlated with increased splenic levels of the cytokine IL-10, which is suggestive for a weakened immune control to S.Tm infection.

INTERPRETATION

Supplementing iron to anaemic mice worsens the clinical course of bacterial infection. This can be traced back to increased iron delivery to bacteria along with an impaired anti-microbial immune response. Our findings may have important implications for iron supplementation strategies in areas with high endemic burden of infections, putting those individuals, who potentially profit most from iron supplementation for anaemia, at the highest risk for infections.

FUNDING

Financial support by the Christian Doppler Laboratory for Iron Metabolism and Anemia Research.

Keeping the peace: commensal Cutibacterium acnes trains CD4+ TH17 cells to trap and kill

Commensal or pathogenic bacterial communities of the skin interact with the host immune system to preserve homeostasis or sustain disease. In this issue of the JCI, Agak et al. substantially advance our conceptual understanding of TH17 cell biology. The researchers identified IL-26-independent mechanisms by which CD4+ TH17 clones directly kill bacteria. These CD4+ TH17 clones share antimicrobial properties with cytotoxic T cells and granulocytes as evidenced by secretion of granulysin, granzyme B, and histone-laden DNA extracellular traps. Interestingly, these clones emerged following monocyte education by Cutibacterium acnes strains associated with healthy skin, but not those associated with acne. Overall, the antimicrobial mechanisms employed by these TH17 subsets suggest a unique link between innate and adaptive immune responses.

Immune Cell Degranulation in Fungal Host Defence

Humans have developed complex immune systems that defend against invading microbes, including fungal pathogens. Many highly specialized cells of the immune system share the ability to store antimicrobial compounds in membrane bound organelles that can be immediately deployed to eradicate or inhibit growth of invading pathogens. These membrane-bound organelles consist of secretory vesicles or granules, which move to the surface of the cell, where they fuse with the plasma membrane to release their contents in the process of degranulation. Lymphocytes, macrophages, neutrophils, mast cells, eosinophils, and basophils all degranulate in fungal host defence. While anti-microbial secretory vesicles are shared among different immune cell types, information about each cell type has emerged independently leading to an uncoordinated and confusing classification of granules and incomplete description of the mechanism by which they are deployed. While there are important differences, there are many similarities in granule morphology, granule content, stimulus for degranulation, granule trafficking, and release of granules against fungal pathogens. In this review, we describe the similarities and differences in an attempt to translate knowledge from one immune cell to another that may facilitate further studies in the context of fungal host defence.

Glucuronoxylomannan in the Cryptococcus species capsule as a target for Chimeric Antigen Receptor T-cell therapy

BACKGROUND AIMS

The genus Cryptococcus comprises two major fungal species that cause clinical infections in humans: Cryptococcus gattii and Cryptococcus neoformans. To establish invasive human disease, inhaled cryptococci must penetrate the lung tissue and reproduce. Each year, about 1 million cases of Cryptococcus infection are reported worldwide, and the infection's mortality rate ranges from 20% to 70%. Many HIV+/AIDS patients are affected by Cryptococcus infections, with 220,000 cases of cryptococcal meningitis reported worldwide in this population every year (C. neoformans infection statistics, via the Centers for Disease Control and Prevention, https://www.cdc.gov/fungal/diseases/cryptococcosis-neoformans/statistics.html). To escape from host immune cell attack, Cryptococcus covers itself in a sugar-based capsule composed primarily of glucuronoxylomannan (GXM). To evade phagocytosis, yeast cells increase to a >45-µm perimeter and become titan, or giant, cells. Cryptococci virulence is directly proportional to the percentage of titan/giant cells present during Cryptococcus infection. To combat cryptococcosis, the authors propose the redirection of CD8+ T cells to target the GXM in the capsule via expression of a GXM-specific chimeric antigen receptor (GXMR-CAR).

RESULTS

GXMR-CAR has an anti-GXM single-chain variable fragment followed by an IgG4 stalk in the extracellular domain, a CD28 transmembrane domain and CD28 and CD3-ς signaling domains. After lentiviral transduction of human T cells with the GXMR-CAR construct, flow cytometry demonstrated that 82.4% of the cells expressed GXMR-CAR on their surface. To determine whether the GXMR-CAR+ T cells exhibited GXM-specific recognition, these cells were incubated with GXM for 24 h and examined with the use of brightfield microscopy. Large clusters of proliferating GXMR-CAR+ T cells were observed in GXM-treated cells, whereas no clusters were observed in control cells. Moreover, the interaction of GXM with GXMR-CAR+ T cells was detected via flow cytometry by using a GXM-specific antibody, and the recognition of GXM by GXMR-CAR T cells triggered the secretion of granzyme and interferon gamma (IFN-γ). The ability of GXMR-CAR T cells to bind to the yeast form of C. neoformans was detected by fluorescent microscopy, but no binding was detected in mock-transduced control T cells (NoDNA T cells). Moreover, lung tissue sections were stained with Gomori Methenamine Silver and evaluated by NanoZoomer (Hamamatsu), revealing a significantly lower number of titan cells, with perimeters ranging from 50 to 130 µm and giant cells >130 µm in the CAR T-cell treated group when compared with other groups. Therefore, the authors validated the study's hypothesis by the redirection of GXMR-CAR+ T cells to target GXM, which induces the secretion of cytotoxic granules and IFN-γ that will aid in the control of cryptococcosis CONCLUSIONS: Thus, these findings reveal that GXMR-CAR+ T cells can target C. neoformans. Future studies will be focused on determining the therapeutic efficacy of GXMR-CAR+ T cells in an animal model of cryptococcosis.

Defining the Mechanistic Correlates of Protection Conferred by Whole-Cell Vaccination against Pseudomonas aeruginosa Acute Murine Pneumonia

Pseudomonas aeruginosa is a Gram-negative pathogen that causes severe pulmonary infections associated with high morbidity and mortality in immunocompromised patients. The development of a vaccine against P. aeruginosa could help prevent infections caused by this highly antibiotic-resistant microorganism.

Pseudomonas aeruginosa is a Gram-negative pathogen that causes severe pulmonary infections associated with high morbidity and mortality in immunocompromised patients. The development of a vaccine against P. aeruginosa could help prevent infections caused by this highly antibiotic-resistant microorganism. We propose that identifying the vaccine-induced correlates of protection against P. aeruginosa will facilitate the development of a vaccine against this pathogen. In this study, we investigated the mechanistic correlates of protection of a curdlan-adjuvanted P. aeruginosa whole-cell vaccine (WCV) delivered intranasally. The WCV significantly decreased bacterial loads in the respiratory tract after intranasal P. aeruginosa challenge and raised antigen-specific antibody titers. To study the role of B and T cells during vaccination, anti-CD4, -CD8, and -CD20 depletions were performed prior to WCV vaccination and boosting. The depletion of CD4⁺, CD8⁺, or CD20⁺ cells had no impact on the bacterial burden in mock-vaccinated animals. However, depletion of CD20⁺ B cells, but not CD8⁺ or CD4⁺ T cells, led to the loss of vaccine-mediated bacterial clearance. Also, passive immunization with serum from WCV group mice alone protected naive mice against P. aeruginosa, supporting the role of antibodies in clearing P. aeruginosa. We observed that in the absence of T cell-dependent antibody production, mice vaccinated with the WCV were still able to reduce bacterial loads. Our results collectively highlight the importance of the humoral immune response for protection against P. aeruginosa and suggest that the production of T cell-independent antibodies may be sufficient for bacterial clearance induced by whole-cell P. aeruginosa vaccination.

Granulysin: killer lymphocyte safeguard against microbes

Primary T cell immunodeficiency and HIV-infected patients are plagued by non-viral infections caused by bacteria, fungi, and parasites, suggesting an important and underappreciated role for T lymphocytes in controlling microbes. Here, we review recent studies showing that killer lymphocytes use the antimicrobial cytotoxic granule pore-forming peptide granulysin, induced by microbial exposure, to permeabilize cholesterol-poor microbial membranes and deliver death-inducing granzymes into these pathogens. Granulysin and granzymes cause microptosis, programmed cell death in microbes, by inducing reactive oxygen species and destroying microbial antioxidant defenses and disrupting biosynthetic and central metabolism pathways required for their survival, including protein synthesis, glycolysis, and the Krebs cycle.

Inflammatory response under zinc deficiency is exacerbated by dysfunction of the T helper type 2 lymphocyte-M2 macrophage pathway

Nutritional zinc deficiency leads to immune dysfunction and aggravates inflammation. However, the underlying mechanism remains unknown. In this study, the relationship between macrophage subtypes (M1 and M2) and helper T lymphocytes (Th1 and Th2) was investigated using the spleen from rats fed zinc-deficient or standard diet. In experiment I, 5-week-old male Sprague-Dawley rats were fed a zinc-deficient diet (without zinc additives) or a standard diet (containing 0·01% zinc) for 6 weeks. In experiment II, the rats were divided into four groups: one group was fed a standard diet for 6 weeks; two groups were fed zinc-deficient diets and were injected three times a week with either saline or interleukin-4 (IL-4) (zinc-deficient/IL-4 i.p.); a fourth group (zinc-deficient/standard) was fed a zinc-deficient diet for 6 weeks followed by a standard diet for 4 weeks. In experiment I; GATA-binding protein 3 (GATA-3) protein level, M2 macrophage, CD3⁺  CD8⁺ cells, and IL-4/IL-13-positive cells significantly decreased in the spleens of the zinc-deficient group. Additionally, IL-1β and macrophage inflammatory protein-1α (MIP-1α) mRNA levels significantly increased in the splenic macrophages of the zinc-deficient group. In experiment II; M2 macrophages, CD3⁺  CD8⁺ cells, IL-4/IL-13-positive cells, and GATA-3 protein levels significantly increased in the spleens of the zinc-deficient/IL-4 i.p. and zinc-deficient/standard groups. Furthermore, IL-1β and MIP-1α mRNA levels decreased in the splenic macrophages of the zinc-deficient/IL-4 i.p. and zinc-deficient/standard groups. Zinc deficiency-induced aggravated inflammation is related to Th2 lymphocytes and followed by the association with loss of GATA-3, IL-4 and anti-inflammatory M2 macrophages. Importantly, IL-4 injection or zinc supplementation can reverse the effects of zinc deficiency on immune function.

Early CD8+-recovery independently predicts low probability of disease relapse but also associates with severe GVHD after allogeneic HSCT

In this single-center study we retrospectively evaluated the impact of early reconstitution of different lymphocyte subsets on patient outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We found that CD8+ T-cell counts exceeding 50x10(6)/l as early as on day 28 post-transplantation correlated significantly with decreased relapse risk, with three-year relapse rates of 17.0% and 55.6% (P = 0.002), but were also associated with severe acute and chronic GVHD. Incidence of grade III-IV acute GVHD was 30.5% for those with early CD8+ T-cell recovery compared to 2.1% for those with lower CD8+ T-cell counts on day 28 post-transplant (HR = 20.24, P = 0.004). Early CD8+ T-cell reconstitution did not, however, affect the overall survival. Multivariate analysis showed that slow CD8+ T-cell reconstitution was strongly associated with increased risk of relapse (HR = 3.44, P = 0.026). A weaker correlation was found between CD4+ reconstitution and relapse-risk, but there was no such association with CD19+ B-cells or NK-cells. In conclusion, the early CD8+ T-cell recovery on day 28 post-transplant is associated with the lower risk of relapse but also predicts the impending severe GVHD, and thus could be useful in guiding timely treatment decisions.

Hints on T cell responses in a fish-parasite model: Enteromyxum leei induces differential expression of T cell signature molecules depending on the organ and the infection status

BACKGROUD

Enteromyxum leei is a myxozoan parasite that produces a slow-progressing intestinal disease. This parasite invades the paracellular space of the intestinal epithelium and progresses from the posterior to the anterior intestine. The aim of the present study was to gain insights into fish T cell responses in the gilthead sea bream-E. leei infection model using a PCR-array with 30 signature molecules for different leukocyte responses in head kidney, spleen, anterior and posterior intestine.

RESULTS

The PCR-array results suggest that E. leei induced migration of T cells from head kidney to intestines where T_H1, CTL and T_H17 profiles were activated and kept in balance by the upregulation of regulatory cytokines. These results were partially validated by the use of cross-reacting antibodies and BrdU immunostaining to monitor proliferation. Zap70 immunostaining supported the increased number of T cells in the anterior intestine detected by gene expression, but double staining with BrdU did not show active proliferation of this cell type at a local level, supporting the migration from lymphohaematopoietic tissues to the site of infection. Global analyses of the expression profiles revealed a clear separation between infected and exposed, but non-infected fish, more evident in the target organ. Exposed, non-infected animals showed an intermediate phenotype closer to the control fish.

CONCLUSIONS

These results evidence a clear modulation of the T cell response of gilthead sea bream upon E. leei infection. The effects occurred both at local and systemic levels, but the response was stronger and more specific at the site of infection, the intestine. Altogether, this research poses a promising basis to understand the response against this important parasite and establish effective preventive or palliative measures.

Immune Mechanisms Involved in Schistosoma mansoni-Cathepsin B Vaccine Induced Protection in Mice

A vaccine against schistosomiasis would contribute to a long-lasting decrease in disease spectrum and transmission. Our previous protection studies in mice using Schistosoma mansoni Cathepsin B (Sm-Cathepsin B) resulted in 59 and 60% worm burden reduction with CpG oligodeoxynucleotides and Montanide ISA720 VG as adjuvants, respectively. While both formulations resulted in significant protection in a mouse model of schistosomiasis, the elicited immune responses differed. Therefore, in this study, we aimed to decipher the mechanisms involved in Sm-Cathepsin B vaccine-mediated protection. We performed in vitro killing assays using schistosomula stage parasites as targets for lung-derived leukocytes and serum obtained from mice immunized with Sm-Cathepsin B adjuvanted with either Montanide ISA 720 VG or CpG and from non-vaccinated controls. Lung cells and immune sera from the Sm-Cathepsin B + Montanide group induced the highest killing (63%) suggesting the importance of antibodies in cell-mediated parasite killing. By contrast, incubation with lung cells from Sm-Cathepsin B + CpG immunized animals induced significant parasite killing (53%) independent of the addition of immune serum. Significant parasite killing was also observed in the animals immunized with Sm-Cathepsin B alone (41%). For the Sm-Cathepsin B + Montanide group, the high level killing effect was lost after the depletion of CD4⁺ T cells or natural killer (NK) cells from the lung cell preparation. For the Sm-Cathepsin B + CpG group, high parasite killing was lost after CD8⁺ T cell depletion, and a reduction to 39% was observed upon depletion of NK cells. Finally, the parasite killing in the Sm-Cathepsin B alone group was lost after the depletion of CD4⁺ T cells. Our results demonstrate how the different Sm-Cathepsin B formulations influence the immune mechanisms involved in parasite killing and protection against schistosomiasis.

Contribution of APCs to mucosal-associated invariant T cell activation in infectious disease and cancer

APCs such as monocytes and dendritic cells are among the first cells to recognize invading pathogens and initiate an immune response. The innate response can either eliminate the pathogen directly, or through presentation of Ags to T cells, which can help to clear the infection. Mucosal-associated invariant T (MAIT) cells are among the unconventional T cells whose activation does not involve the classical co-stimulation during Ag presentation. MAIT cells can be activated either via presentation of unconventional Ags (such as riboflavin metabolites) through the evolutionarily conserved major histocompatibility class I-like molecule, MR1, or directly by cytokines such as IL-12 and IL-18. Given that APCs produce cytokines and can express MR1, these cells can play an important role in both pathways of MAIT cell activation. In this review, we summarize evidence on the role of APCs in MAIT cell activation in infectious disease and cancer. A better understanding of the interactions between APCs and MAIT cells is important in further elucidating the role of MAIT cells in infectious diseases, which may facilitate the design of novel interventions such as vaccines.

In vitro lymphoproliferative response and cytokine production in mice with experimental disseminated candidiasis

Objective(s):

Systemic candidiasis is an infection of Candida albicans (C. albicans) causing disseminated disease and sepsis, invariably when host defenses are compromised. We investigated the histopathological changes as well as the lymphoproliferative responses and cytokine production of splenic cells after stimulation with Concanavalin A (Con A) and Pokeweed mitogen (PWM) in mice with disseminated candidiasis.

Materials and Methods:

Lymphoproliferative responses were stimulated in vitro with Con A (1 µg/ml) and PWM (1 µg/ml) mitogens in Roswell Park Memorial Institute (RPMI) 1640 media, and the production of interferon (IFN)-γ and interleukin-4 (IL-4) in the supernatants was measured by enzyme-linked immunosorbent assay (ELISA).

Results:

The results revealed that C. albicans organisms multiplied to a greater extent in the kidneys than in the liver and spleen of infected mice. The most predominant forms of C. albicans in different parts of the kidneys were yeast mixed with hyphal forms. Infected mice had a significantly increased proliferative response when splenocytes were stimulated with PWM (2.0±0.16) and Con A (1.9±0.19) (P<0.05). PWM and Con A-stimulated production of IFN-γ significantly tended to be higher in infected mice (PWM: 68.4±14.0 pg/ml; Con A: 53.7±17.3 pg/ml) when compared to controls (P<0.05). Stimulation with PWM and Con A showed no differences in IL-4 production between infected mice and controls.

Conclusion:

These findings demonstrated a significant increase in both cell proliferation and IFN-γ secretion in supernatants of PWM and Con A- stimulated splenocyte cultures obtained from mice with disseminated candidiasis.

New insights on the development of fungal vaccines: from immunity to recent challenges

Fungal infections are emerging as a major problem in part due to high mortality associated with systemic infections, especially in the case of immunocompromised patients. With the development of new treatments for diseases such as cancer and the acquired immune deficiency syndrome pandemic, the number of immunosuppressed patients has increased and, as a consequence, also the number of invasive fungal infections has increased. Several studies have proposed new strategies for the development of effective fungal vaccines. In addition, better understanding of how the immune system works against fungal pathogens has improved the further development of these new vaccination strategies. As a result, some fungal vaccines have advanced through clinical trials. However, there are still many challenges that prevent the clinical development of fungal vaccines that can efficiently immunise subjects at risk of developing invasive fungal infections. In this review, we will discuss these new vaccination strategies and the challenges that they present. In the future with proper investments, fungal vaccines may soon become a reality.

T Cells in Fish

Cartilaginous and bony fish are the most primitive vertebrates with a thymus, and possess T cells equivalent to those in mammals. There are a number of studies in fish demonstrating that the thymus is the essential organ for development of T lymphocytes from early thymocyte progenitors to functionally competent T cells. A high number of T cells in the intestine and gills has been reported in several fish species. Involvement of CD4⁺ and CD8α⁺ T cells in allograft rejection and graft-versus-host reaction (GVHR) has been demonstrated using monoclonal antibodies. Conservation of CD4⁺ helper T cell functions among teleost fishes has been suggested in a number studies employing mixed leukocyte culture (MLC) and hapten/carrier effect. Alloantigen- and virus-specific cytotoxicity has also been demonstrated in ginbuna and rainbow trout. Furthermore, the important role of cell-mediated immunity rather than humoral immunity has been reported in the protection against intracellular bacterial infection. Recently, the direct antibacterial activity of CD8α⁺, CD4⁺ T-cells and sIgM⁺ cells in fish has been reported. In this review, we summarize the recent progress in T cell research focusing on the tissue distribution and function of fish T cells.

Zebrafish Nk-lysins: First insights about their cellular and functional diversification

Nk-lysins are antimicrobial proteins produced by cytotoxic T lymphocytes and natural killer cells with a broad antimicrobial spectrum (including bacteria, fungi and parasites). Nevertheless, the implication of these proteins in the protection against viral infections is still poorly understood. In this work, four different Nk-lysin genes (nkla, nklb, nklc and nkld) were identified in the zebrafish genome. That means that zebrafish is the species with the higher repertoire of Nk-lysin genes described so far. The differential expression pattern of the Nk-lysins in several tissues, during ontogeny, among the different kidney cell populations, as well as between Rag1(-/-) and Rag1(+/+) individuals, could suggest a certain specialization of different cell types in the production of different Nk-lysin. Moreover, only two of these genes (nkla and nkld) were significantly up-regulated after viral infection, and this observation could be also a consequence of a functional diversification of the zebrafish Nk-lysins.

Direct antibacterial activity of CD8+/CD4+ T-cells in ginbuna crucian carp, Carassius auratus langsdorfii

Cytotoxic T cells (CTLs) constitute an important component of the specific effector mechanism in killing against microbial-infected or transformed cells. In addition to these activities, recent studies in mammals have suggested that CTLs can exhibit direct antimicrobial activity. Therefore, the present investigation was conducted to find out the microbicidal activity of CD8α(+) T cells of ginbuna crucian carp, Carassius auratus langsdorfii. The CD8α(+) T cells from immunised ginbuna exhibited the antibacterial activity against both facultative intracellular bacteria and extracellular bacteria. The maximum reduction of viable count of pathogens was recorded with effector (sensitized) cells and target (bacteria) ratio of 10:1 co-incubated for a period of 1-2 h at 26 °C when effector cells were derived from ginbuna 7 days after one booster dose at 15th day of primary sensitization/immunisation. Sensitized CD8α(+) T cells are found to kill 92.1 and 98.9% of Lactococcus garvieae and Edwardsiella tarda, respectively. No significant difference in the bacterial killing activity could be recorded against facultative intracellular bacteria and extracellular bacteria. The specificity study indicated the non-specific killing of bacteria. CD8α(+) T cells from E. tarda immunised ginbuna exhibited 40% of non-specific killing activity against L. garvieae and those from L. garvieae immunised ginbuna showed 42.7% of non-specific killing activity against E. tarda. Furthermore, CD4(+) T cells also killed 88% and 95.7% of L. garvieae and E. tarda, respectively. In addition to T cell subsets, surface IgM(+) cells also killed both types of pathogens. Therefore, the present study demonstrated the direct antibacterial activity of CD8α(+), CD4(+) T-cells and surface IgM(+) cells in fish.

Functionality of CD4+ and CD8+ T cells from tonsillar tissue

For many years, tonsillectomy has been used routinely in children to treat chronic or recurrent acute tonsillitis. Palatine tonsils are secondary lymphoid organs and the major barrier protecting the digestive and respiratory tracts from potential invasive microorganisms. They have been used as sources of lymphoid tissue; however, despite the hundreds of papers published on tonsillectomy, no studies addressing the functionality of the CD4(+) and CD8(+) T cells from chronically infected tonsils have yet been published. The aim of this study was to analyse the functionality of the CD4(+) and CD8(+) T cells with respect to tonsillar tissue. We used an affordable approach to measure the frequency of antigen-specific CD4(+) T cells, the direct ex-vivo cytotoxicity of CD8(+) T cells, memory T cell phenotype, cytokine profile and DC phenotype. Our results demonstrate that CD4(+) and CD8(+) T cells from tonsillar tissue are totally functional, as shown by their ability to produce cytokines, to degranulate and to differentiate into effector-memory T cells.