Study on the Cell Wall Skeleton Derived from Mycobacterium bovis BCG Tokyo 172 (SMP-105): Establishment of Preparation and Analytical Methods

The Adjuvant Activity of BCG Cell Wall Cytoskeleton on a Dengue Virus-2 Subunit Vaccine

The uneven immunogenicity of the attenuated tetravalent dengue vaccine has made it difficult to achieve balanced protection against all four serotypes of the dengue virus (DENV). To overcome this problem, non-replicative vaccines have come into focus, as their immunogenicity is adjustable. This approach is excellent for multivalent vaccines but commonly faces the issue of low immunogenicity. In this present study, we developed a non-replicating dengue vaccine composed of UV-inactivated dengue virus-2 (UV-DENV-2) and DENV-2 NS1-279 protein encapsidated within nanoparticles. This vaccine candidate was administered in the presence of BCG cell wall cytoskeleton (BCG-CWS) as an adjuvant. We revealed, here, that encapsidated immunogens with BCG-CWS exerted potent activities on both B and T cells and elicited Th-1/Th-2 responses in mice. This was evidenced by BCG-CWS significantly augmenting antibody-mediated complement-fixing activity, strongly stimulating the antigen-specific polyfunctional T cell responses, and activating mixed Th-1/Th-2 responses specific to DENV-2- and NS1-279 antigens. In conclusion, BCG-CWS potently adjuvanted the inactivated DENV-2 and DENV subunit immunogens. The mechanism of adjuvanticity remains unclear. This study revealed the potential use of BCG-CWS in vaccine development.

Mycobacterium bovis BCG-mediated suppression of Th17 response in mouse experimental autoimmune encephalomyelitis

INTRODUCTION

Multiple sclerosis (MS) is an autoimmune disease mediated by a pro-inflammatory immune response. Experimental autoimmune encephalomyelitis (EAE) induced by immunization of mice with a myelin oligodendrocyte glycoprotein (MOG) peptide emulsified in killed Mycobacterium tuberculosis-containing complete Freund's adjuvant (CFA-EAE) is used as a model of MS. Mycobacterium bovis BCG has been reported to ameliorate clinical symptoms of CFA-EAE, although the precise mechanism has not yet been documented. Since CFA-EAE uses adjuvant with mycobacterial antigens, mycobacterial antigen-specific T cells induced by CFA may cross-react with BCG and modulate EAE.

METHODS

To exclude the influence of cross-reactivity, a modified murine EAE model (cell wall skeleton (CWS)-EAE) that does not induce mycobacterial antigen-specific T cells was established and used to reevaluate the therapeutic effects of BCG on EAE.

RESULTS

Inoculation with BCG 6 d after CWS-EAE induction successfully ameliorated EAE symptoms, suggesting that the therapeutic effects of BCG are independent of the mycobacterial antigen-specific T cells induced by the CFA-EAE protocol. BCG inoculation into the CWS-EAE mice resulted in reduced levels of MOG-specific Th17 in the central nervous system (CNS) with reduced demyelinated lesions of the spinal cord. In the draining lymph nodes of the MOG-immunized sites, BCG inoculation resulted in an increase in MOG-specific Th17 and Th1 cells at an early stage of immune response.

CONCLUSION

The results suggest that BCG inoculation suppresses the Th17 response in the CNS of EAE mice via a mechanism that may involve the suppression of egress of encephalitogenic T cells from lymphoid organs.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

Nano-BCG: A Promising Delivery System for Treatment of Human Bladder Cancer

Mycobacterium bovis bacillus Calmette–Guerin (BCG) remains at the forefront of immunotherapy for treating bladder cancer patients. However, the incidence of recurrence and progression to invasive cancer is commonly observed. There are no established effective intravesical therapies available for patients, whose tumors recur following BCG treatment, representing an important unmet clinical need. In addition, there are very limited options for patients who do not respond to or tolerate chemotherapy due to toxicities, resulting in poor overall treatment outcomes. Within this context, nanotechnology is an emergent and promising tool for: (1) controlling drug release for extended time frames, (2) combination therapies due to the ability to encapsulate multiple drugs simultaneously, (3) reducing systemic side effects, (4) increasing bioavailability, (5) and increasing the viability of various routes of administration. Moreover, bladder cancer is often characterized by high mutation rates and over expression of tumor antigens on the tumor cell surface. Therapeutic targeting of these biomolecules may be improved by nanotechnology strategies. In this mini-review, we discuss how nanotechnology can help overcome current obstacles in bladder cancer treatment, and how nanotechnology can facilitate combination chemotherapeutic and BCG immunotherapies for the treatment of non-muscle invasive urothelial bladder cancer.

Mycobacterial cell-wall skeleton as a universal vaccine vehicle for antigen conjugation

Mycobacterial cell-wall skeleton (CWS) is an immunoactive and biodegradable particulate adjuvant and has been used for immunotherapy in patients with cancer. The CWS of Mycobacterium bovis bacillus Calmette-Guérin (BCG-CWS) was studied as a universal vaccine vehicle for antigen conjugation, to develop potentially effective and safe vaccines. Here, we describe experiments in which protein antigens, such as keyhole limpet haemocyanin (KLH), ovalbumin (OVA) and bovine serum albumin (BSA) were highly efficiently coupled to 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS)-activated carboxyl groups of BCG-CWS, and tested the immunogenicity of OVA-conjugated BCG-CWS vaccine. We found that a strong immune response was induced in mice immunised with OVA-conjugated BCG-CWS, which was similar to the enhancement of the immune responses in mice immunised with OVA and complete Freund's adjuvant. Covalent conjugation of OVA to BCG-CWS was essential for Th1-skewed immune responses, with prominent expression of IFN-γ. Furthermore, antigen-conjugated BCG-CWS vaccine is simple to manufacture, safe, and easy to use. Our results suggest that mycobacterial CWS as a universal vaccine vehicle for conjugation of a wide variety of antigens constitutes a breakthrough for development of the most promising vaccines for infections, allergic diseases, and cancer.

Morphological study on Mycobacterium bovis BCG Tokyo 172 cell wall skeleton (SMP-105)

Mycobacterial cell wall consists of rigid cell wall skeleton (CWS), a mycoloyl arabinogalactan peptidiglycan complex, in which mycoloyl structure varies by the mycobacterial species diversely, whereas the arabinogalactan peptidoglycan structure is consistent comparatively. The CWS of Mycobacterium bovis BCG has long been expected as a potent adjuvant for immunotherapy of malignant tumor. Although the chemical structure of CWS has been established in the last few decades, the physicochemical properties of CWS having highly amphipathic micelle structure with very long mycoloyl and carbohydrate chains are not unveiled. In this study, the ultrastructure of CWS of M. bovis BCG Tokyo 172 (SMP-105), suspended in several solvents with different polarity, was investigated with a particle size analyzer, a transmission electron microscope (TEM) and other techniques. As a result, the particle size was about 4.7 to 67.8 microm in physiological saline, but it became smaller and more compact when suspended in hydrophobic solvents. TEM images showed two different morphological forms distinctively: double folded sheet structure in hydrophilic conditions and multilayered rolled sheet structure in hydrophobic conditions. These studies have revealed characteristic surface features of SMP-105, the hydrophobic moiety occupying dominant space and the hydrophilic moiety smaller space, respectively, which may lead to the acceleration of immunological studies on this product.

Activation of Toll-like receptor 2 by a novel preparation of cell wall skeleton from Mycobacterium bovis BCG Tokyo (SMP-105) sufficiently enhances immune responses against tumors

The cell wall skeleton of Mycobacterium bovis BCG has been investigated as an immunopotentiating adjuvant for immuno-therapy of malignant tumors via Toll-like receptor (TLR) 2 and TLR4. However, due to its high molecular weight, highly complicated lipoglycan structure, and complicated purification and isolation procedure, its exact structure-activity relationship has not been well established. We have newly isolated the cell wall skeleton from M. bovis BCG Tokyo (SMP-105) and examined the binding of SMP-105 with TLR. It was revealed that highly purified SMP-105 activates the nuclear factor-kB promoter in a TLR2-dependent manner, not a TLR4-dependent manner, using a reporter gene assay system. Peritoneal exudated cells of TLR2 and MyD88 knockout mice severely reduced the induction of tumor necrosis factor-alpha and interleukin-6 in the presence of SMP-105, whereas cells from TLR4 knockout mice produced similar levels of cytokines to wild-type mice. Dendritic cells and macrophages accumulated in the draining lymph nodes of treated mice. When mice were administered both SMP-105 and mitomycin C-inactivated Lewis lung carcinoma cells simultaneously, interferon-gamma-producing cells reacting to the tumor were increased distinctly in draining lymph nodes. When C57BL/6 mice, into which splenocytes from OT-I transgenic mice had been transferred, were administered with both SMP-105 and E.G7-OVA, OVA-specific cytotoxic T lymphocytes (CTL) increased markedly. Mice treated with SMP-105 and inactivated Lewis lung carcinoma cells suppressed the growth of implanted tumors. These results suggest that the activation of TLR2 by SMP-105 sufficiently enhanced immune responses, such as the number of interferon-gamma-producing cells and CTL, and prevented the growth of tumors without the contribution of TLR4.

Comprehensive analysis of mycolic acid subclass and molecular species composition of Mycobacterium bovis BCG Tokyo 172 cell wall skeleton (SMP-105)

The mycobacterial cell envelope consists of a characteristic cell wall skeleton (CWS), a mycoloyl arabinogalactan peptidoglycan complex, and related hydrophobic components that contribute to the cell surface properties. Since mycolic acids have recently been reported to play crucial roles in host immune response, detailed molecular characterization of mycolic acid subclasses and sub-subclasses of CWS from Mycobacterium bovis BCG Tokyo 172 (SMP-105) was performed. Mycolic acids were liberated by alkali hydrolysis from SMP-105, and their methyl esters were separated by silica gel TLC into three subclasses: alpha-, methoxy-, and keto-mycolates. Each mycolate subclass was further separated by silver nitrate (AgNO(3))-coated silica gel TLC into sub-subclasses. Molecular weights of individual mycolic acid were determined by MALDI-TOF mass spectrometry. alpha-Mycolates were sub-grouped into cis, cis-dicyclopropanoic (alpha1), and cis-monocyclopropanoic-cis-monoenoic (alpha2) series; methoxy-mycolates were sub-grouped into cis-monocyclopropanoic (m1), trans-monocyclopropanoic (m2), trans-monoenoic (m3), cis-monocyclopropanoic-trans-monoenoic (m4), cis-monoenoic (m5), and cis-monocyclopropanoic-cis-monoenoic (m6) series; and keto-mycolates were sub-grouped into cis-monocyclopropanoic (k1), trans-monocyclopropanoic (k2), trans-monoenoic (k3), cis-monoenoic (k4), and cis-monocyclopropanoic-cis-monoenoic (k5) series. The position of each functional group, including cyclopropane rings and methoxy and keto groups, was determined by analysis of the meromycolates with fast atom bombardment (FAB) mass spectrometry and FAB mass-mass spectrometry, and the cis/trans ratio of cyclopropane rings and double bonds were determined by NMR analysis of methyl mycolates. Mycolic acid subclass and molecular species composition of SMP-105 showed characteristic features including newly-identified cis-monocyclopropanoic-trans-monoenoic mycolic acid (m4).