Purification, biochemical characterization and immunogenicity of SA5K, a secretion antigen of Mycobacterium tuberculosis

Mycobacterium paratuberculosis CobT activates dendritic cells via engagement of Toll-like receptor 4 resulting in Th1 cell expansion

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne disease in animals and MAP involvement in human Crohn disease has been recently emphasized. Evidence from M. tuberculosis studies suggests mycobacterial proteins activate dendritic cells (DCs) via Toll-like receptor (TLR) 4, eventually determining the fate of immune responses. Here, we investigated whether MAP CobT contributes to the development of T cell immunity through the activation of DCs. MAP CobT recognizes TLR4, and induces DC maturation and activation via the MyD88 and TRIF signaling cascades, which are followed by MAP kinases and NF-κB. We further found that MAP CobT-treated DCs activated naive T cells, effectively polarized CD4(+) and CD8(+) T cells to secrete IFN-γ and IL-2, but not IL-4 and IL-10, and induced T cell proliferation. These data indicate that MAP CobT contributes to T helper (Th) 1 polarization of the immune response. MAP CobT-treated DCs specifically induced the expansion of CD4(+)/CD8(+)CD44(high)CD62L(low) memory T cells in the mesenteric lymph node of MAP-infected mice in a TLR4-dependent manner. Our results indicate that MAP CobT is a novel DC maturation-inducing antigen that drives Th1 polarized-naive/memory T cell expansion in a TLR4-dependent cascade, suggesting that MAP CobT potentially links innate and adaptive immunity against MAP.

Characterization and identification of distinct Mycobacterium massiliense extracellular proteins from those of Mycobacterium abscessus

Mycobacterium massiliense is an emerging pathogen and very similar to Mycobacterium abscessus of rapidly growing mycobacteria in the phenotype and genotype. Pathogenic bacteria secrete a diversity of factors into extracellular medium which contribute to the bacterial pathogenicity. In the present study, we performed the comparative proteome analysis of culture filtrate proteins from a clinical isolate of M. massiliense and M. abscessus strains using two-dimensional gel electrophoresis and liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). Interestingly, 9 proteins of M. massiliense were distinctly expressed from those of M. abscessus. Bioinformatic analysis of the identified proteins revealed that 3 unique proteins corresponded to serine/arginine rich protein, membrane protein from Streptomyces coelicolor, and one hypothetical protein from Corynebacterium efficiens YS-314, respectively. Culture filtrate proteins from M. massiliense induced the release of pro-inflammatory cytokines from macrophages in a dose-dependent manner but not that from M. abscessus. Taken together, the functional study on the identified proteins uniquely produced from M. massiliense may provide not only the clues for the different pathogensis, but also help develop the diagnostic tools for the differentiation between two mycobacterial species.

The secretion antigen SA5K has a role in the adaptation of Mycobacterium bovis bacillus Calmette-Guérin to intracellular stress and hypoxia

The Mycobacterium tuberculosis TB8.4 (Rv1174c) gene encodes a secreted protein of 8.4 kDa (TB8.4) which has been suggested to be involved in reactivation of dormant mycobacteria. We have previously reported that inactivation of an identical gene (sa5k) in Mycobacterium bovis BCG causes impaired ability of the mutant strain (BCGsa5k::aph) to grow inside human macrophages. This study aimed to investigate the role of TB8.4 in the reactivation of aged cultures of BCG as well as the role of the sa5k gene in the resistance of BCG to intracellular stress conditions and adaptation to hypoxia. Although when added to aged cultures of BCG, TB8.4 caused a statistically significant increase in the number of colony-forming units, a similar effect was obtained in cultures incubated with BSA, suggesting a non-specific growth stimulation by TB8.4. Compared to parental BCG, the BCGsa5k::aph strain showed an increased susceptibility to reactive oxygen and nitrogen intermediates and to acid stress and an impaired ability to adapt to reduced O2 concentrations, when tested in the oxygen-limited Wayne culture system. These results suggest that the product of the sa5k gene (SA5K protein) has a role in both resistance of BCG to intracellular stress and in its adaptation to hypoxia.

Immunomodulation by SanPharma Fungal Metabolic Products

OBJECTIVE

In the present study, a series of fungal metabolite products from SanPharma (Dohren, Germany) were tested for effects on human peripheral blood leukocytes in vitro using standard immunologic methods.

BACKGROUND

Therapeutic strategies used in German biological medicine often include treatment (oral, nasal, rectal, topical, or injection) with fungal or bacterial products, also known as "isopathic remedies," of which some are limited to metabolic products, whereas others include microbial cell lysates and cell wall fragments as well. The SanPharma products are based on metabolites, and do not contain microbial cell wall compounds.

METHODS

Activation of natural killer (NK) cells was evaluated by cell surface immunostaining using CD3, CD56, CD69, and CD25 monoclonal antibodies. Production of interferon-gamma was evaluated by enzyme-linked immunoabsorbent assay (ELISA) on supernatants collected after 5 days' culture of peripheral blood mononuclear cells (PBMC). Direct mitogenic effect was assessed using the lipophilic membrane dye PHK26 (Sigma-Aldrich, St. Louis, MO) in a fluorescence-based proliferation assay, in which fluorescence intensity is reduced upon cell divisions. Cell viability upon exposure to fungal metabolites was assessed using propidium iodide staining and flow cytometry.

RESULTS

All fungal metabolite products specifically induced the expression of the CD69 marker on human CD3-negative, CD56-positive NK cells, but not CD3-positive T cells, in vitro, as shown by the induction of the CD69 marker on up to 50% of NK cells after 18 hours' culture with metabolites. Only one of the five metabolite products, Roqueforti, induced cyclooxygenase-2 (COX-2), indicating that nuclear factor-kappaB (NFkappaB)-mediated signaling may not have been involved in the NK activation by the other four products. The Notatum product reduced baseline levels of COX-2, indicating an anti-inflammatory effect. No evidence of toxic or mitogenic effects was found.

CONCLUSIONS

The fungal metabolite products from SanPharma specifically activate human NK cells in vitro.

Disruption of the gene encoding for secretion antigen SA5K affects growth of Mycobacterium bovis bacillus Calmette-Guerin in human macrophages and in mice

An 8.3-kDa secretory antigen of Mycobacterium bovis bacillus Calmette-Guerin (BCG), called SA5K, was previously identified and characterized in our laboratory. Sequence analysis of the BCG sa5k gene, including the corresponding promoter region, showed that it is identical to the homologous gene in Mycobacterium tuberculosis (Rv1174c). No significant homology with other proteins was found and the physiologic role of SA5K for mycobacteria remains unknown. In the present study, a BCG mutant strain (BCGsa5k::aph) was constructed by allelic exchange involving the replacement of the sa5k gene with a kanamycin-inactivated copy. Mutant and parental strains showed similar growth rates in liquid medium, suggesting that the loss of the sa5k gene does not affect the in vitro growth of BCG. Nevertheless, BCGsa5k::aph showed a reduced ability to grow in human macrophages compared with the wild-type BCG, suggesting that SA5K is involved in intracellular survival/multiplication mechanisms. The mutant strain was also attenuated in vivo in a mouse infection model, showing impaired growth/survival in spleen and liver and fewer and smaller granulomatous lesions compared to the parental strain. Complementation of the mutation restored the parental phenotype. Taken together, results presented in this study suggest a role for SA5K in the growth capacity of BCG both in an intracellular milieu and in infected mice.

Expression of SA5K, a secretion antigen of Mycobacterium tuberculosis, inside human macrophages and in sputum from tuberculosis patients

An 8.3 kDa protein (SA5K), secreted by Mycobacterium tuberculosis/Mycobacterium bovis bacillus Calmette-Guérin (BCG) in culture filtrate, has been previously described in our laboratory. In the present study, analysis of the distribution of SA5K gene (Rv1174c) among M. tuberculosis strains, isolated from a wide variety of clinical specimens, revealed that the gene is present in all clinical isolates analyzed (29/29). SA5K expression inside human macrophages infected with BCG was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) on RNA extracted from bacterial cells following 24 and 48 h of infection. In addition, in order to evaluate whether SA5K gene was also expressed at the site of infection in the lung, a nested RT-PCR assay was developed to detect specific mRNA in sputum samples collected from smear positive tuberculosis patients. SA5K mRNA was detected in all the samples containing high numbers of tubercle bacilli demonstrating that the corresponding gene is expressed during the course of clinical infection.

PPE antigen Rv2430c of Mycobacterium tuberculosis induces a strong B-cell response

The variation in sequence and length in the C-terminal region among members of the unique PE (Pro-Glu) and PPE (Pro-Pro-Glu) protein families of Mycobacterium tuberculosis is a likely source of antigenic variation, giving rise to the speculation that these protein families could be immunologically important. Based on in silico analysis, we selected a hypothetical open reading frame (ORF) encoding a protein belonging to the PPE family and having epitopes with predictably higher antigenic indexes. Reverse transcriptase PCR using total RNA extracted from in vitro-cultured M. tuberculosis H37Rv generated an mRNA product corresponding to this gene, indicating the expression of this ORF (Rv2430c) at the mRNA level. Recombinant protein expressed in Escherichia coli was used to screen the sera of M. tuberculosis-infected patients, as well as those of clinically healthy controls (n = 10), by enzyme-linked immunosorbent assay. The panel of patient sera comprised sera from fresh infection cases (category 1; n = 32), patients with relapsed tuberculosis (category 2; n = 30), and extrapulmonary cases (category 3; n = 30). Category 2 and 3 sera had strong antibody responses to the PPE antigen, equal to or higher than those to other well-known antigens, such as Hsp10 or purified protein derivative (PPD). However, a higher percentage of patients belonging to category 1, as opposed to clinically healthy controls, showed stronger antibody response against the PPE protein when probed with anti-immunoglobulin M (IgM) (71 versus 37.5%) or anti-IgG (62.5 versus 28.12%). Our results reveal that this PPE ORF induces a strong B-cell response compared to that generated by M. tuberculosis Hsp10 or PPD, pointing to the immunodominant nature of the protein.