Role of mast cells as IL10 producing cells in paracoccidioidomycosis skin lesions

Recent works have demonstrated that mast cells may have an important role in immunologic reactions and inflammation once they synthesize and secrete many cytokines including IL4, IL5, IL6 and TNF-α. We have conducted research in order to verify if mast cells would participate in the local inflammatory immune response against Paracoccidioides brasiliensis in skin lesions characterized by a Th2 pattern of cytokines. Fifty-nine skin biopsies with previous histopathological diagnosis of paracoccidioidomycosis and immunohistochemical characterization of cytokines present in the inflammatory infiltrate were classified in three groups: group 1 (G1), with compact granuloma and a Th1 pattern of cytokines; group 2 (G2), with loose granuloma and a Th2 pattern of cytokines; group 3 (G3), both kind of granuloma in the same lesion, characterized by cytokines from Th1 and Th2 patterns. Ten biopsies from normal skin were used as control group. Mast cells were visualized and quantified by a toluidine blue/HCl staining and a double immunostaining was performed to detect a co-localization of mast cells and IL10. G2 presented an increased number of mast cells when compared to G1, G3 and control group and we frequently could find mast cells expressing IL10 in G2. The data obtained suggest that mast cells participate in the immune response against P. brasiliensis in skin lesions with loose granuloma and a Th2 pattern of cytokines. Considering these results, mast cells could constitute a source of IL10, contributing to a non-effective response against fungal antigens.     

Phylogeographic patterns in the Philippine archipelago influence symbiont diversity in the bobtail squid–Vibrio mutualism

Marine microbes encounter a myriad of biotic and abiotic factors that can impact fitness by limiting their range and capacity to move between habitats. This is especially true for environmentally transmitted bacteria that cycle between their hosts and the surrounding habitat. As geologic history, biogeography, and other factors such as water temperature, salinity, and physical barriers can inhibit bacterial movement to novel environments, we chose to examine the genetic architecture of Euprymna albatrossae (Mollusca: Cephalopoda) and their Vibrio fischeri symbionts in the Philippine archipelago using a combined phylogeographic approach. Eleven separate sites in the Philippine islands were examined using haplotype estimates that were examined via nested clade analysis to determine the relationship between E. albatrossae and V. fischeri populations and their geographic location. Identical analyses of molecular variance (AMOVA) were used to estimate variation within and between populations for host and symbiont genetic data. Host animals demonstrated a significant amount of variation within island groups, while symbiont variation was found within individual populations. Nested clade phylogenetic analysis revealed that hosts and symbionts may have colonized this area at different times, with a sudden change in habitat. Additionally, host data indicate restricted gene flow, whereas symbionts show range expansion, followed by periodic restriction to genetic flow. These differences between host and symbiont networks indicate that factors “outside the squid” influence distribution of Philippine V. fischeri. Our results shed light on how geography and changing environmental factors can impact marine symbiotic associations at both local and global scales.     

The effects of ionizing radiation on stem cells and hematopoietic progenitors: the place of apoptosis and the therapeutic potential of anti-apoptosis treatments

Abstract: Bone marrow aplasia observed following ionizing radiation exposure (Total Body Irradiation; gamma dose range: 2-10 Gy) is a result, in particular, of the radiation-induced (RI) apoptosis in hematopoietic stem and progenitor cells (HSPC). We have previously shown in a baboon model of mobilized peripheral blood CD34+ cell irradiation in vitro that RI apoptosis in HSPC was an early event, mostly occurring within the first 24 hours, which involves the CD95 Fas pathway. Apoptosis may be significantly reduced with a combination of 4 cytokines (4F): Stem Cell Factor (SCF), FLT-3 Ligand (FL), thrombopoietin (TPO), and interleukin-3 (IL-3), each at 50 ng x mL(-1) (15% survival versus <3% untreated cells, 24 h post-irradiation at 2.5 Gy). In this study we show that addition of TNF-alpha(800 IU/ml) induces an increase in 4F efficacy in terms of cell survival 24 h after incubation (26% survival after 24 h irradiation exposure at 2.5 Gy) and amplification (k) of CD34+ cells after 6 days in a serum free culture medium (SFM) (kCD34+ = 4.3 and 6.3 respectively for 4F and successive 4F + TNF-a/ 4F treatments). In addition, the 4F combination allows culture on pre-established allogenic irradiated stromal cells in vitro at 4 Gy (kCD34+ = 4.5). Overall this study suggests (i) the potential therapeutic interest for an early administration of anti-apoptotic cytokines with or without hematopoiesis inhibitors (emergency cytokine therapy) and (ii) the feasibility in the accidentally irradiated individual, of autologous cell therapy based on ex vivo expansion in order to perform autograft of residual HSPC collected after the accident.     

Mesenchymal stem cells support expansion of in vitro irradiated CD34(+) cells in the presence of SCF, FLT3 ligand, TPO and IL3: potential application to autologous cell therapy in accidentally irradiated victims

Ex vivo expansion of residual autologous hematopoietic stem and progenitor cells collected from victims soon after accidental irradiation (autologous cell therapy) may represent an additional or alternative approach to cytokine therapy or allogeneic transplantation. Peripheral blood CD34+ cells could be a useful source of cells for this process provided that collection and ex vivo expansion of hematopoietic stem and progenitor cells could be optimized. Here we investigated whether mesenchymal stem cells could sustain culture of irradiated peripheral blood CD34+ cells. In vitro irradiated (4 Gy 60Co gamma rays) or nonirradiated mobilized peripheral blood CD34+ cells from baboons were cultured for 7 days in a serum-free medium supplemented with stem cell factor+thrombopoietin+interleukin 3+FLT3 ligand (50 ng/ml each) in the presence or absence of mesenchymal stem cells. In contrast to cultures without mesenchymal stem cells, irradiated CD34+ cells cultured with mesenchymal stem cells displayed cell amplification, i.e. CD34+ (4.9-fold), CD34++ (3.8-fold), CD34++/Thy-1+ (8.1-fold), CD41+ (12.4-fold) and MPO+ (50.6-fold), although at lower levels than in nonirradiated CD34+ cells. Fourteen times more clonogenic cells, especially BFU-E, were preserved when irradiated cells were cultured on mesenchymal stem cells. Moreover, we showed that the effect of mesenchymal stem cells is related mainly to the reduction of apoptosis and involves cell-cell contact rather than production of soluble factor(s). This experimental model suggests that mesenchymal stem cells could provide a crucial tool for autologous cell therapy applied to accidentally irradiated victims.     

In vivo and in vitro modulation of HLA-DM and HLA-DO is induced by B lymphocyte activation.

Ag presentation via HLA class II molecules in B lymphocytes depends on the coordinated action of HLA-DM, the catalyst of class II-peptide loading, and HLA-DO, a pH-dependent modulator of DM, the expression of which is almost completely restricted to B lymphocytes. The relative expression levels of both class II modulators are critical for the composition of the HLA class II peptide repertoire. The data in this work demonstrate that DO and DM expression are both dependent on the cellular activation status in primary human B lymphocytes. In vivo low-density activated primary human B lymphocytes show a prominent reduction in DO and DM expression when compared with high-density resting primary B lymphocytes. In vitro, reduction of DO and DM expression can be induced by B lymphocyte activation via the B cell receptor or by use of the phorbol ester, PMA. Specific inhibition of protein kinase C resulted in a significant reduction of HLA-DO and is potentially due to protein degradation in lysosomal compartments as the phenomenon is reversed by chloroquine. Thus, the expression of the dedicated HLA class II chaperone DM and its pH-dependent modulator DO is regulated and tightly controlled by the activation status of the B lymphocyte.     

M2-Polarized Macrophages Determine Human Cutaneous Lesions in Lacaziosis

Lacaziosis is a cutaneous chronic mycosis caused by Lacazia loboi. Macrophages are important cells in the host immune response in fungal infections. The macrophage population exhibits strong plasticity that varies according to the stimuli in the microenvironment of lesions M1 profile promotes a Th1 pattern of cytokines and a microbicidal function and M2 is related to Th2 cytokines and immunomodulatory response. We investigated the population of M1 and M2 polarized macrophages in human cutaneous lesions. A total of 27 biopsies from human lesions were submitted to an immunohistochemistry protocol using antibodies to detect M1 and M2 macrophages (Arginase-1, CD163, iNOS, RBP-J and cMAF). We could observe high number of cells expressing Arginase1, CD163 and c-MAF that correspond to elements of the M2 profile of macrophage, over iNOS and RBP-J (elements of the M1 profile). The results suggest a predominant phenotype of M2 macrophages, which have an immunomodulatory role and probably contributing to chronicity of Lacaziosis.

     

Cutaneous and Bone Marrow Histoplasmosis After 18 Years of Renal Allograft Transplant

The frequency of histoplasmosis among solid organ transplant (SOT) recipients appears to be low where there are only a few case series, mostly among renal and liver transplant recipients. Herein we report a case of a 44-year-old woman who underwent a living-related renal transplant 18 years prior to evaluation, developed a nodule after followed by ulceration upon her posterior right leg and a second one upon her left leg 3 months and 2 months before her hospitalisation, respectively. The biopsy of lesion revealed the presence of Histoplasma spp. Bone marrow aspiration was performed and also revealed the same organism. She had initially received itraconazole without improvement of lesions, while a new lesion appeared on her left arm. Healing of all lesions could be observed after 40 days of liposomal amphotericin B when she was submitted to skin grafts on the legs and a surgical treatment on the arms, and the myelosuppression improved simultaneously. Histoplasmosis seems to be very uncommon among patients who underwent to organ solid transplantation. Most cases occur within 12–18 months after transplantation, although unusual cases have been presented many years post-transplant. There are cases reported in the literature, occurring from 84 days to 18 years after organ transplantation, but without cutaneous involvement. Our patient developed lesions on limbs and myelosuppression after 18 years of chronic immunosuppression medication. This case suggests that besides cutaneous histoplasmosis is an uncommon infection following iatrogenic immunosuppression and even rarer over a long period after the transplantation. Clinicians who care SOT recipient patients must bear in mind histoplasmosis infection as differential diagnosis in any case of cutaneous injury with prolonged fever and try to use as many tools as possible to make the diagnosis, once this disease presents a good prognosis if it is diagnosed and treated promptly.     

Virulent synergistic effect between Enterococcus faecalis and Escherichia coli assayed by using the Caenorhabditis elegans model

Background

The role of enterococci in the pathogenesis of polymicrobial infections is still debated. The purpose of this study was to evaluate the effect of virulent enterococci in the presence or absence of Escherichia coli strains in the in vivo Caenorhabditis elegans model.

Principal Findings

This study demonstrated that there was a synergistic effect on virulence when an association of enterococci and E. coli (LT50 = 1.6 days±0.1 according to the tested strains and death of nematodes in 4 days±0.5) was tested in comparison with enterococci alone (LT50 = 4.6 days±0.1 and death in 10.4 days±0.6) or E. coli alone (LT50 = 2.1±0.9 and deaths 6.6±0.6) (p<0.001). In addition, there was a relation between the virulence of E. faecalis strains alone and the virulence potential of the association with E. coli strains. Finally, in the presence of avirulent E. coli strains, enterococci have no effect (LT50 = 4.3±0.5 and deaths in 10.8±0.8), independently of the level of their own virulence, demonstrating that the ‘enterococci effect’ only occurred in the presence of virulent E. coli strains.

Conclusion

This study allows a better understanding of a bacterial cooperation. Moreover, it could help to optimize the antibiotic regimen during polymicrobial infections.     

Virulence potential and genomic mapping of the worldwide clone Escherichia coli ST131

Recently, the worldwide propagation of clonal CTX-M-15-producing Escherichia coli isolates, namely ST131 and O25b:H4, has been reported. Like the majority of extra-intestinal pathogenic E. coli isolates, the pandemic clone ST131 belongs to phylogenetic group B2, and has recently been shown to be highly virulent in a mouse model, even though it lacks several genes encoding key virulence factors (Pap, Cnf1 and HlyA). Using two animal models, Caenorhabditis elegans and zebrafish embryos, we assessed the virulence of three E. coli ST131 strains (2 CTX-M-15- producing urine and 1 non-ESBL-producing faecal isolate), comparing them with five non-ST131 B2 and a group A uropathogenic E. coli (UPEC). In C. elegans, the three ST131 strains showed intermediate virulence between the non virulent group A isolate and the virulent non-ST131 B2 strains. In zebrafish, the CTX-M-15-producing ST131 UPEC isolates were also less virulent than the non-ST131 B2 strains, suggesting that the production of CTX-M-15 is not correlated with enhanced virulence. Amongst the non-ST131 B2 group isolates, variation in pathogenic potential in zebrafish embryos was observed ranging from intermediate to highly virulent. Interestingly, the ST131 strains were equally persistent in surviving embryos as the non-ST131-group B2 strains, suggesting similar mechanisms may account for development of persistent infection. Optical maps of the genome of the ST131 strains were compared with those of 24 reference E. coli strains. Although small differences were seen within the ST131 strains, the tree built on the optical maps showed that these strains belonged to a specific cluster (86% similarity) with only 45% similarity with the other group B2 strains and 25% with strains of group A and D. Thus, the ST131 clone has a genetic composition that differs from other group B2 strains, and appears to be less virulent than previously suspected.