In vitro T-cell immunogenicity of oligopeptides derived from the region 92-110 of the 16-kDa protein ofMycobacterium tuberculosis

Hsp16.3 of mycobacterium tuberculosis in exosomes as a biomarker of tuberculosis

Exosomes are selectively packaged cell-derived vesicles that contain a rich cargo of nucleic acids and proteins. The small heat shock protein, Hsp16.3, is an important capsule protein produced by Mycobacterium tuberculosis (MTB). Exploring the distribution of Hsp16.3 in exosomes is valuable to tuberculosis biomarker development. Our results showed that Hsp16.3 protein overexpressed in cells can be efficiently packaged into exosomes. U937 cells infected with MTB secreted abnormally excessive amounts of Hsp16.3 protein in exosomes. Finally, a substantial number of Hsp16.3 proteins were detected in blood exosomes of tuberculosis patients. The research provides a potential exosome-based tuberculosis biomarker for MTB diagnosis.

Enhancement of immune response against Mycobacterium tuberculosis HspX antigen by incorporation of combined molecular adjuvant (CASAC)

Tuberculosis (TB) is one of the deadliest human diseases worldwide caused by mycobacterial infection in the lung. Bacillus Calmette-Guerin (BCG) vaccine protects against disseminated TB in children, but its effectiveness is still questionable due to highly variable protections in adolescence and elderly individuals. Targeting the latency M.tb antigen is a recent therapeutic approach to eradicate dormant pathogen that could possibly lead to disease activation. In this study, we aimed to potentiate immune responses elicited against 16 kDa α-crystalline (HspX) tuberculosis latency antigen by incorporation of Combined Adjuvant for Synergistic Activation of Cellular immunity (CASAC). Histidine-tagged recombinant HspX protein was initially produced in Escherichia coli and purified using Ni-NTA chromatography. To evaluate its adjuvanticity, C57BL/6 mice (n = 5) were initially primed and intradermally immunised in 2-weeks interval for 4 rounds with recombinant HspX, formulated with and without CASAC. Humoral and cell-mediated immune responses elicited against HspX antigen were evaluated using ELISA and Flow Cytometry. Our findings showed that CASAC improved humoral immunity with increased antigen-specific IgG1 and IgG2a antibody response. Stronger CD8+ and Th1-driven immunity was induced by CASAC formulation as supported by elevated level of IFN-γ, TNF-α, IL-12 and IL-17A; and with low IL-10 secretion. Interestingly, adjuvanted HspX vaccine triggered a higher percentage of effector memory T-cell population than those immunised with unadjuvanted vaccine. In conclusion, CASAC adjuvant has great potential to enhance immunogenicity elicited against HspX antigen, which could be an alternative regimen to improve the efficacy of future therapeutic vaccine against Mycobacterium tuberculosis.

Insights into Macrophage Autophagy in Latent Tuberculosis Infection: Role of Heat Shock Protein 16.3

Tuberculosis (TB) is a major bacterial infectious disease worldwide that is predominantly caused by Mycobacterium tuberculosis (Mtb). The comorbidity of multiple drug-resistant TB strains with HIV and diabetes is widespread. In the presence of these diseases, host immunity is weakened, allowing the recovery of dormant bacilli and leading to recurrent TB infection. As an important component of the host innate and adaptive immune responses, macrophage autophagy plays a significant role in protecting the host against TB. However, dormant bacilli can escape from autophagosomes and/or suppress autophagy, thus surviving within the host for an extended period of time, although the underlying mechanism remains elusive. Heat shock protein 16.3 (Hsp16.3, HspX, Rv2031c, and Acr) is one of the immunodominant proteins expressed during latent TB infection (LTBI). It may help maintain the protein stability and long-term viability of Mtb by inhibiting macrophage autophagy, resulting in LBTI. In this review, we discuss how dormant bacilli escape from autophagosomes, and we focus on the role of Hsp16.3 in regulating macrophage autophagy in LTBI so as to provide a firm basis for further studies. Hsp16.3 may represent a potential biomarker of LTBI and novel pharmacological target for anti-tubercular drugs.

Characterization of desmoglein-3 epitope region peptides as synthetic antigens: analysis of their in vitro T cell stimulating efficacy, cytotoxicity, stability, and their conformational features

Desmoglein-3 (Dsg3) adhesion protein is the main target of autoantibodies and autoreactive T cells in Pemphigus vulgaris (PV) autoimmune skin disorder. Several mapping studies of Dsg3 T cell epitope regions were performed, and based on those data, we designed and synthesized four peptide series corresponding to Dsg3 T cell epitope regions. Each peptide series consists of a 17mer full-length peptide (Dsg3/189-205, Dsg3/206-222, Dsg3/342-358, and Dsg3/761-777) and its N-terminally truncated derivatives, resulting in 15 peptides altogether. The peptides were prepared on solid phase and were chemically characterized. In order to establish a structure-activity relationship, the solution conformation of the synthetic peptides has been investigated using electronic circular dichroism spectroscopy. The in vitro T cell stimulating efficacy of the peptides has been determined on peripheral blood mononuclear cells isolated from whole blood of PV patients and also from healthy donors. After 20 h of stimulation, the interferon (IFN)-γ content of the supernatants was measured by enzyme-linked immunosorbent assay. In the in vitro conditions, peptides were stable and non-cytotoxic. The in vitro IFN-γ production profile of healthy donors and PV patients, induced by peptides as synthetic antigens, was markedly different. The most unambiguous differences were observed after stimulation with 17mer peptide Dsg3/342-358, and three truncated derivatives from two other peptide series, namely, peptides Dsg3/192-205, Dsg3/763-777, and Dsg3/764-777. Comparative analysis of in vitro activity and the capability of oligopeptides to form ordered or unordered secondary structure showed that peptides bearing high solvent sensibility and backbone flexibility were the most capable to distinguish between healthy and PV donors.

Adaptive immune stimulation is required to obtain high protection with fatty acid binding protein vaccine candidate against Fasciola hepatica in Balb/C mice

Fascioliasis is a parasitic disease that mainly affects cattle and sheep, causing significant economic losses with a great impact in developing countries. Human fascioliasis is becoming more important with the high endemicity in some countries of the world. Previous studies have shown the importance of Fasciola hepatica fatty acid binding proteins (FABP) as protective molecules against fascioliasis in various animal models including mice, rabbits, and sheep. Our studies have shown the protective efficacy of recombinant FABP (rFh15) when the protein is formulated in the adjuvant adaptation system (ADAD), using either natural or synthetic immunomodulators. The ADAD system is most effective when it is used 5 days before each dose of specific vaccine antigen. The results showed survival rates of up to 50% with less severe hepatic lesions and high levels of IgG2a or IFNγ in immunized mice, using the ADAD system, compared to survival rates of 13% with no hepatic lesion reduction and high levels of IgG1 and IL-4 in those mice immunized with the simplified mode (ADADs).

The Schistosoma bovis Sb14-3-3ζ recombinant protein cross-protects against Schistosoma mansoni in BALB/c mice

Current control programs against schistosomiasis could be reinforced through the use of an effective vaccine. Schistosome 14-3-3 proteins have been proposed as candidates for vaccine against the respective infections, and were seen to elicit high protection levels against Schistosoma bovis in a previous work done by our group. We have therefore investigated the protective capacity of the 14-3-3 protein from S. bovis - Sb14zeta - against Schistosoma mansoni in mice. In addition, we have addressed the influence of the co-administration of three different immunomodulators with the 14-3-3 polypeptide. Protection was high when the Sb14zeta protein was combined in two independent experiments with the AA2829 and PAL immunomodulatory molecules as regards both the reduction of worm numbers (mean: 64.8%) and egg loads in liver (mean: 73.9%) or intestine (mean: 71.5%). In contrast, the degree of protection achieved with the Sb14zeta-CpG vaccine was very low (14.9% reduction in worm numbers, and 46.6% and 32% reduction in liver and intestinal egg loads). The immune responses observed in the vaccinated animals showed that the production of IFNgamma and the absence of IL-4, accompanied by a strong humoral response, are insufficient to elicit protection against S. mansoni.

The Sb14-3-3ζ recombinant protein protects against Schistosoma bovis in BALB/c mice

Schistosoma bovis is a trematode parasite mainly affecting cattle and sheep. Evidences about the arise of drug resistance and the high rates of re-infection of animals in endemic areas have pointed out the need of developing new control tools, e.g., effective vaccines. Schistosomes 14-3-3 proteins have been defined as vaccine candidates against respective infections. We have therefore investigated the protective capacity of the 14-3-3 protein from S. bovis - Sb14zeta - against S. bovis in mice. In addition, we have addressed the influence of the co-administration of four different immunomodulators with the 14-3-3 polypeptide. The values of protection against S. bovis were statistically significant when the Sb14zeta was combined in two independent experiments with the AA0029 (61.0% and 40.31%), AA2829 (49% and 36.3%) and PAL (49% and 40.075%) immunomodulatory molecules. Immune responses from vaccinated animals showed that the highest protection rates do not necessarily match with a dominant Th1-type response.