Liposomes as immunological adjuvants and delivery systems in the development of tuberculosis vaccine: A review

Liposomes are phospholipid bilayer vesicles, which are biocompatible, biodegradable and nontoxic vehicles suitable for numerous drug and gene delivery applications. In this review, we discuss the prospect of using liposome technology in the development of a vaccine for tuberculosis. Tuberculosis remains an important health problem that requires the development of an effective vaccine, especially since the only approved vaccine for it continues to be the Bacille Calmette-Geurin (BCG) one developed 100 years ago. This review focuses on the different applications of liposomes toward achieving this goal. Numerous liposomal formulations showing prospect in the research stage and in clinical trials are discussed.

Liposomes as immunological adjuvants and delivery systems in the development of tuberculosis vaccine: A review

Liposomes are phospholipid bilayer vesicles, which are biocompatible, biodegradable and nontoxic vehicles suitable for numerous drug and gene delivery applications. In this review, we discuss the prospect of using liposome technology in the development of a vaccine for tuberculosis. Tuberculosis remains an important health problem that requires the development of an effective vaccine, especially since the only approved vaccine for it continues to be the Bacille Calmette-Geurin (BCG) one developed 100 years ago. This review focuses on the different applications of liposomes toward achieving this goal. Numerous liposomal formulations showing prospect in the research stage and in clinical trials are discussed.

Generation of a T cell receptor (TCR)-like single domain antibody (sDAb) against a Mycobacterium Tuberculosis (Mtb) heat shock protein (HSP) 16kDa antigen presented by Human Leukocyte Antigen (HLA)-A*02.

The discovery of heat shock protein 16 kDa antigen protein has deepen the understanding of latent tuberculosis since it was found to be primarily expressed by Mycobacterium tuberculosis during latent phase leading to the rapid optimization and development in terms of diagnosis and therapeutics. Recently, T cell receptor-like antibody has been explored extensively targeting various diseases due to its dual functionality (T cell receptor and antibody). In this study, a TCR-like domain antibody (A2/Ab) with the binding capacity to Mtb heat shock protein (HSP) 16 kDa antigen presented by major histocompatible complex (MHC) HLA-A*02 was successfully generated via biopanning against human domain antibody library. The generated antibody (A2/Ab) exhibited strong functionality and binding capacity against the target assuring the findings of this study to be beneficial for the development of latent tuberculosis diagnosis and immunotherapeutics in future.

Specific and cross-reactive immune response against Mycobacterium tuberculosis antigens in mice immunized with proteoliposomes from Mycobacterium bovis BCG

Objective To characterize the immunogenicity and the induction of cross-reactive responses against Mycobacterium tuberculosis (M. tuberculosis) of a proteoliposome (PL) from Mycobacterium bovis Bacillus Calmette–Guérin (BCG) with and without alum hydroxide (AL) as adjuvant (PLBCG-AL and PLBCG, respectively) in BALB/c mice. Methods BALB/c mice were inoculated with phosphate buffer solution, BCG, PLBCG and PLBCG-AL. The humoral immunogenicity was determined by ELISA [immunoglobulin G (IgG), IgG1 and IgG2a] and the cellular immunogenicity was evaluated in vivo by delayed type hypersensitivity. The humoral cross-reactive response against M. tuberculosis was determined by Western blot. Results Sera from animals immunized with PLBCG-AL and PLBCG showed significant increase in specific total IgG and IgG1 antibodies and the presence of cross-reactive antibodies against M. tuberculosis antigens, which were more intense with the use of alum as adjuvant. Mice immunized with PLBCG and PLBCG-AL also showed a specific cellular response in vivo. Conclusions The cellular and humoral immunogenicity of PLBCG and the capacity to induce cross-reactive responses against M. tuberculosis is in agreement with the protective capacity previously demonstrated by this vaccine candidate and supports the continuation of its evaluation in further stages.

Aplicación de una biblioteca de anticuerpos lineales humanos frente al polisacárido capsular de Neisseria meningitidis serogrupo B / Application of a human linear antibody library against the capsular polysaccharide from Neisseria meningitidis serogroup B

Neisseria meningitidis serogrupo B produce aún morbimortalidad significativa. Su polisacárido capsular muestra similitud estructural con proteínas humanas y pobre inmunogenicidad, obstaculizando así el desarrollo de vacunas y anticuerpos monoclonales (AcM) y policlonales contra esta bacteria. Recientemente se han creado bibliotecas artificiales de anticuerpos humanos expresados en bacteriófagos que reconocen específicamente a moléculas diana existentes, con la ventaja sobre los AcM convencionales por su rápida obtención, sin utilización de animales de laboratorio, lo que emerge como alternativa atractiva para la producción de AcM contra antígenos peculiares o complejos. Se realizó un trabajo de investigación básica, utilizando una biblioteca de fagos filamentosos que expresan constitutivamente regiones variables de anticuerpos humanos, que se enfrentó al polisacárido capsular de N. meningitidis serogrupo B. Los resultados que se obtuvieron mediante ELISA policlonal sugieren la existencia de anticuerpos humanos expresados en fagos que lo reconocen(AU)

Neisseria meningitidis serogroup B still produces a significant morbidity and mortality. Bacterial capsular polysaccharide in serogroup B shows structural homologies with human proteins and poor immunogenicity which make difficult the development of vaccines and polyclonal and monoclonal antibodies (MAb) against it. Artificial libraries of human antibodies via the expression and selection of them in bacteriophages have become known. Those antibodies are used as specific recognizing molecules capable to join to almost any existing target, with advantages over conventional MAb due to its faster obtainment without needing animal immunization, emerging as an attractive alternative for the production of MAb against complex or particular antigens. This was a basic experimental piece of work, using a phage library that expresses variable regions of human immunoglobulins to identify ligands with the capacity to recognize N. meningitidis serogroup B polysaccharide. Polyclonal ELISA screening suggests the existence of human antibodies expressed in phages which recognized the antigen of interest(AU)

Purification of an IgA Monoclonal Antibody Specific for the Acr Protein of Mycobacterium tuberculosis by Immunoaffinity Chromatography

Background: A monoclonal antibody (mAb) of the IgA isotype, designated TBA61, is specific for the Acr protein of Mycobacterium tuberculosis (MTB). TBA61 has been used in studies exploring protection against tuberculosis (TB), and its efficacy has been proven using different challenge models. To purify the mouse IgA isotype, a combination of methods, such as globulin precipitation, ion exchange, and gel filtration, is usually required to achieve a satisfactory degree of purity. Methods: To minimise the number of chromatographic steps, we proposed to employ immunoaffinity chromatography using the Acr protein of MTB as a specific ligand for this mAb. For this purpose, the HspX gene was cloned and expressed in Escherichia coli, and recombinant Acr (rAcr) was coupled to a cyanogen bromide-activated Sepharose 4B matrix, which was used to purify TBA61 mAb from ascites produced in mice in a single step. Results: The recovery from the purification procedure was 1.46 mg per mL of ascites. Analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot showed a high purity. The purified mAb retained its reactivity against the Acr protein based on enzyme-linked immunosorbent assay (ELISA) and western blot. Conclusion: The purification method used is rapid, simple, and specific and can be easily scaled up.

The use of Streptomyces for immunization against mycobacterial infections.

Tuberculosis is one of the leading causes of mortality produced by an infectious agent. Different strategies including bioinformatics are currently being tested to identify and improve vaccines against tuberculosis. Comparative genome analysis between Streptomyces coelicolor and Mycobacterium tuberculosis suggest that both descend from a common Actinomycete ancestor. In this work, we suggest the use of Streptomyces as a live vector and explore the capacity of Streptomyces immunization to induce a protective response against mycobacterial infection. First, we compared the theoretical proteomes of S. coelicolor A3(2) with those of M. tuberculosis H37Rv and Mycobacterium bovis AF2122/97. This study showed a high similarity at the level of individual genes sequences with both bacteria sharing several membrane proteins. Then, we administered Streptomyces intraperitoneally to mice and determined its distribution by histopathology and culture; we did not find systemic dissemination. After administration of Streptomyces through different routes, we identified the most immunogenic, inducing strong humoral response, as denoted by the high serum antibody titers against this organism with cross reactivity to mycobacterial antigens. Finally, we evaluated the level of protection elicited by the inoculation of Streptomyces in Balb/c mice challenged with BCG. In these animals, lung bacillary loads were significantly lower than the control non-sensitized group.. These observations, along with Streptomyces' potential for expressing foreign proteins, suggest that Streptomyces could be an advantageous vector in the design of new tuberculosis vaccines.