Gut T cell-independent IgA responses to commensal bacteria require engagement of the TACI receptor on B cells.

The gut mounts secretory immunoglobulin A (SIgA) responses to commensal bacteria through nonredundant T cell-dependent (TD) and T cell-independent (TI) pathways that promote the establishment of mutualistic host-microbiota interactions. SIgAs from the TD pathway target penetrant bacteria, and their induction requires engagement of CD40 on B cells by CD40 ligand on T follicular helper cells. In contrast, SIgAs from the TI pathway bind a larger spectrum of bacteria, but the mechanism underpinning their production remains elusive. Here, we show that the intestinal TI pathway required CD40-independent B cell-activating signals from TACI, a receptor for the innate CD40 ligand-like factors BAFF and APRIL. TACI-induced SIgA responses targeted a fraction of the gut microbiota without shaping its overall composition. Of note, TACI was dispensable for TD induction of IgA in gut-associated lymphoid organs. Thus, BAFF/APRIL signals acting on TACI orchestrate commensal bacteria-specific SIgA responses through an intestinal TI program.

Interferon-gamma and interleukin-4 single nucleotide gene polymorphisms in Paracoccidioidomycosis.

The gene polymorphisms interferon-gamma (IFN-gamma) +874 T/A and interleukin (IL)-4 -590 C/T have been associated with the altered production of cytokines. Therefore, they might be indicative of the occurrence of Paracoccidioidomycosis (PCM) caused by Paracoccidioides brasiliensis. The analysis of single nucleotide polymorphism (SNP) at position+874 IFN-gamma showed an increase occurrence of A/T genotype in both PCM patients and healthy individuals as control (HIC) (56% and 45%, respectively), while the allelic distribution showed 82% of A allele in the patients and 80% in the controls. The SNP of -590 IL-4 showed that C/T genotype was significantly (p<0.05) more prevalent (39%) in PCM group compared to the HIC group (19%), while IL-4 C/C genotype was significantly less frequent (59%) in the patient group compared to the control group (81%). Otherwise, 41% of PCM patients and 19% of HIC individuals carried the IL-4 T allele. Stimulation of peripheral blood mononuclear cells (PBMC) from PCM patients with cell extract antigenic preparations (PbAg) as well as secreted and surface antigens (MEXO) of P. brasiliensis evidenced that there is no difference in the IFN-gamma production related to A and T alleles between PCM and HIC individuals. However, with IL-4 production, PCM patients classified as C phenotype showed two times more IL-4 production than PCM patients classified as T phenotype and HIC controls. In conclusion, our results suggest that functional genetic variants in the IL-4 promoter could influence the production of IL-4 in PCM.

Protective immunity induced by rPb27 of Paracoccidioides brasiliensis.

A cDNA coding for an antigenic protein (rPb27) from the pathogenic fungus Paracoccidioides brasiliensis was cloned and its protective activity was determined against paracoccidioidomycosis (PCM). The cDNA sequence contained an open reading frame (ORF) of 660 base pairs encoding a protein of 219 amino acids with a predicted molecular weight of 25kDa. The deduced amino acid sequence exhibited 100% identity to the 27kDa P. brasiliensis hypothetic protein (access number AA49615). The complete coding cDNA was cloned into a pGEX 4T-2 plasmid and expressed in Escherichia coli as a glutathione-S-transferase-tagged (GST) recombinant protein. Mice immunized with purified rPb27 were able to develop high levels of IgG2b, moderate levels of IgG1 and low levels of IgG2a. At the same time the levels of TGF-beta and IFN-gamma were high while a very low production of IL-10 was verified. Using confocal microscopy with anti-rPb27 mouse serum against P. brasiliensis yeast forms, surface and cytosolic staining pattern were observed. Moreover, immunization of mice with this antigen induced a significant degree of protection in the lungs (93%), liver (93%) and spleen (100%) at 60 days after challenge with infection. Thus, the granulomatous lesions revealed a greater degree of compaction and organization, with few lesions in the lungs and no dissemination of the fungus to other organs. These results showed that a recombinant protein of P. brasiliensis (rPb27) promoted acquired protection against infection with P. brasiliensis yeast forms, suggesting the use of this protein for future development as a prophylactic vaccine for PCM.

Analysis of memory T cells in the human paracoccidioidomycosis before and during chemotherapy treatment.

Memory T cell populations in patients with paracoccidioidomycosis (PCM) were analyzed before and after chemotherapy treatment. Peripheral blood mononuclear cells (PBMC) collected from patients infected by Paracoccidioides brasiliensis or from non-infected individuals were stimulated in vitro with either membrane and extra-cellular antigens (MEXO) or yeast cell antigen preparation (PbAg) of P. brasiliensis. An increase in the level of CD4(+) memory T cells was determined in PBMC from PCM patients before (NT) and after treatment (TR) and in those with PCM relapsed (RE) compared to that from non-infected controls (NINF). The CD8(+) memory T cells were increased in PBMC from RE patients stimulated with MEXO, but not in NT or TR. The distribution of memory B cells did not differ between NT and TR patients, while a significant elevation was determined in RE patients and higher antibody levels were also detected. The cytokine analysis showed low production of IFN-gamma by cells from RE patients compared with NT or TR patients. In contrast, high production of IL-4 was detected in NT and RE patients, and moderate levels were produced by RE patients. These results suggest that IFN-gamma production may participate in the maintenance of immunological memory in the acquired protection against P. brasiliensis infection and this data can contribute to future development of successful treatment of PCM to avoid relapsing.

Interleukin-10 and tumor necrosis factor-alpha single nucleotide gene polymorphism frequency in paracoccidioidomycosis.

Allelic variants of cytokine genes seem to be involved in mechanisms of resistance or susceptibility to several diseases. The aim of this study was to investigate the frequency of genotypes with the tumor necrosis factor-alpha TNF-alpha gene polymorphism G/A at position -308 and the IL-10 gene polymorphism G/A at position -1082, and to verify a possible association of these polymorphisms with paracoccidioidomycosis (PCM) caused by Paracoccidioides brasiliensis. Genotyping was performed by allele-specific polymerase chain reaction (ASPCR) and restriction fragment length polymorphism (RFLP) on genomic DNA isolated of granulocytes from 54 PCM patients and 31 noninfected individuals. The analysis of SNP at position -1082 IL-10 showed a high frequency of GA genotype in both patients and controls (51% and 55%, respectively), while the allelic frequency showed 54% of G allele in the patients and 66% of A allele in the controls. The GG genotype was more frequent in patients (85%) and controls (68%) when we analyze the SNP at position -308 of TNF-alpha gene. Otherwise, 91% of PCM patients and 84% of noninfected individuals carried the G allele in -308 TNF-alpha SNP. Stimulation of cells from individuals with PCM phenotyped as A+ (GA or AA genotypes) presented elevation of TNF-alpha producing cells when compared with IL-10-producer cells. These findings reinforce the critical role of IL-10 and TNF-alpha in the paracoccidioidomycosis and can strongly suggest that the genetic screening of the -308G/A and -1082G/A polymorphisms may be a valid tool for identification of subjects needing a more appropriate therapy.

Membrane and extracellular antigens of Paracoccidioides brasiliensis (Mexo): identification of a 28-kDa protein suitable for immunodiagnosis of paracoccidioidomycosis.

In this work, we analyzed serological responses of paracoccidioidomycosis (PCM) patients to membrane and extracellular antigens (Mexo) of Paracoccidioides brasiliensis by ELISA, immunoblot technique and immunofluorescence assays to identify a specific antigen profile. Among 140 PCM serum samples analyzed, a homogeneous IgG response to Mexo was observed. The specificity of this antigen was 96.6% in relation to control sera and 81.2% to sera from patients with diverse infections. Patients undergoing treatment for more than 1 year showed a reduced antibody response against Mexo. These results suggest that the presence of anti-Mexo antibodies might be an indicator of active disease. A protein from Mexo with a molecular weight of 28 kDa (Pb28) was the most specific antigen in humoral immune responses to PCM, since it reacted with 100% of patient sera and did not react with heterologous serum samples tested. This protein was purified by molecular filtration chromatography in FPLC system and, when tested by immunoblotting, it maintained its reactivity and specificity of 100% with PCM sera. The Pb28 N-terminal amino acid sequence comparison analysis in the non-redundant GenBank database at NCBI revealed no significant homology to known PCM proteins or to other fungal proteins of known function. Since the 28-kDa protein of P. brasiliensis seems to be specific for PCM, it can be used as an alternative antigen in immunoblotting diagnostic methods.

Modulation of CD28 and CD86 expression in patients with paracoccidioidomycosis in different periods of treatment.

Paracoccidioides brasiliensis, a thermo-dimorphic fungus, is the ethiologic agent of paracoccidioidomycosis (PCM). The recidive is the greatest obstacle of this disease, because the yeast usually returns after the long treatment period. In the present work, we have investigated the cellular immune response of cells from peripheral blood drawn from patients with different duration of PCM. The classification of patients ranged from nontreated to those with long-standing disease over 5 years. Unstimulated as well as cells stimulated with phytohemaglutinin or two different antigen preparations, secreted (MEXO) or somatic (PbAg) of P. brasiliensis, were characterized. We found that cells from patients with disease proliferate considerably upon stimulation with the antigen preparations and that cells from patients with disease of long duration does not proliferate that vigorously as from patients with more recent diagnosis. Both interferon (IFN)-gamma and interleukin (IL)-4 appear to be increased in patients, but IFN-gamma tended to increase upon treatment while IL-4-secretion decreased. With respect to CD28 and CD86, we found that the subset of CD28 positive CD8 cells are decreased in all stages of the disease as compared to control individuals. A subset of CD86 positive CD19 cells appeared to be considerably increased compared to the controls. Indeed, our results demonstrated that the treatment of PCM patients promoted a regulation of IFN-gamma, IL-4 levels and CD28, CD86 expression bringing new insight to the cellular immune response in PCM.

Protective immunity induced in mice by F0 and FII antigens purified from Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis causes a chronic granulomatous mycosis prevalent in South America, and cell-mediated immunity represents the principal mode of protection against this fungal infection. We investigated whether immunization with P. brasiliensis antigens fractionated by anionic chromatography on fast protein liquid chromatography (FPLC) could elicit protective immunity. BALB/c mice were immunized by subcutaneous injection of either 10 microg fractions 0 (F0), II (FII) or III (FIII) in the presence of 100 microg of Corynebacterium parvum and 1 mg of Al(OH)(3) and challenged with pathogenic P. brasiliensis strain. Mice immunized with F0 presented cellular and humoral immune responses with significant production of IFN-gamma, and high levels of IgG2a and IgG3 isotypes. Immunization with FII induced significant production of IFN-gamma and IL-10 associated with high levels of IgG1 and IgG2a. It was demonstrated that immunization with F0 or FII promoted significant decrease of organ colony-forming units (CFUs) in the lung after challenge infection without fungi dissemination to the spleen or liver. In contrast, FIII immunized mice develop a progressive disseminated disease to spleen and liver presented significant levels of INF-gamma, IL-10 or TGF-beta associated with high production of IgG1 and IgG2a with low production of IgG2b and IgG3 after challenge infection. Taken together, these findings suggest that antigens of F0 and FII are reliable vaccine candidates against the paracoccidioidomycosis.