Recombinant mycobacterial DNA-binding protein 1 with post-translational modifications boosts IFN-gamma production from BCG-vaccinated individuals' blood cells in combination with CpG-DNA

Tuberculosis remains a large health threat, despite the availability of the tuberculosis vaccine, BCG. As BCG efficacy gradually decreases from adolescence, BCG-Prime and antigen-booster may be an efficient strategy to confer vaccine efficacy. Mycobacterial DNA-binding protein 1 (MDP1, namely Rv2986c, hupB or HU) is a major Mycobacterium tuberculosis protein that induces vaccine-efficacy by co-administration with CpG DNA. To produce MDP1 for booster-vaccine use, we have created recombinant MDP1 produced in both Escherichia coli (eMDP1) and Mycolicibacterium smegmatis (mMDP1), an avirulent rapid-growing mycobacteria. We tested their immunogenicity by checking interferon (IFN)-gamma production by stimulated peripheral blood cells derived from BCG-vaccinated individuals. Similar to native M. tuberculosis MDP1, we observed that most lysin resides in the C-terminal half of mMDP1 are highly methylated. In contrast, eMDP1 had less post-translational modifications and IFN-gamma stimulation. mMDP1 stimulated the highest amount of IFN-gamma production among the examined native M. tuberculosis proteins including immunodominant MPT32 and Antigen 85 complex. MDP1-mediated IFN-gamma production was more strongly enhanced when combined with a new type of CpG DNA G9.1 than any other tested CpG DNAs. Taken together, these results suggest that the combination of mMDP1 and G9.1 possess high potential use for human booster vaccine against tuberculosis.

Genetic engineering employing MPB70 and its promoter enables efficient secretion and expression of foreign antigen in bacillus Calmette Guérin (BCG) Tokyo

Vaccination is an important factor in public health. The recombinant bacillus Calmette Guérin (rBCG) vaccine, which expresses foreign antigens, is expected to be a superior vaccine against infectious diseases. Here, we report a new recombination platform in which the BCG Tokyo strain is transformed with nucleotide sequences encoding foreign protein fused with the MPB70 immunogenic protein precursor. By RNA-sequencing, mpb70 was found to be the most transcribed among all known genes of BCG Tokyo. Small oligopeptide, namely, polyhistidine tag, was able to be expressed in and secreted from rBCG through a process in which polyhistidine tag fused with intact MPB70 were transcribed by an mpb70 promoter. This methodology was applied to develop an rBCG expressing the receptor binding domain (RBD) of severe acute respiratory syndrome coronavirus 2. Immunoblotting images and mass spectrometry data showed that RBD was also secreted from rBCG. Sera from mice vaccinated with the rBCG showed a tendency of weak neutralizing capacity. The secretion was retained even after a freeze-drying process. The freeze-dried rBCG was administered to and recovered from mice. Recovered rBCG kept secreting RBD. Collectively, our recombination platform offers stable secretion of foreign antigens and can be applied to the development of practical rBCGs.

Sensing and reacting to dangers by caspases: Caspase activation via inflammasomes

Caspases are well known as mediators of programmed cell death, or apoptosis, in which their functions are highly conserved throughout evolution. In addition to inducing apoptosis, caspases have important roles in immune reactions. As part of a cell's response to pathogens or alarm (cellular danger) signals from damaged cells, caspase-1 is activated by forming an inflammatory complex with apoptosisassociated speck like protein containing a caspase recruitment domain (ASC) and nucleotide-binding oligomerization domain like receptor (NLR) family proteins. The activated caspase-1 then cleaves and promotes the maturation of cytokines, such as IL-1β, IL-18, and IL-33. Although it has long been unclear how hosts recognize diverse stresses, including injury and pathogen infection, and react appropriately, recent analyses have revealed many details about the sensing mechanisms provided by NLRs. Members of the NLR family are activated and yield different outcomes depending on the stimulus. For example, the NLR member cryopyrin/NALP3 induces cytokine secretion and lipid synthesis in response to viral dsRNA and K＋ efflux, while another NLR, IPAF, induces IL-1β? in response to the virulence protein, flagellin. Cryopyrin/NALP3-mediated caspase-1 activation is involved not only in the immune response to pathogens but also in the stress response to UV irradiation in human skin. In this review, we focus on the stress responses that particularly involve inflammatory caspases. Since host reactions to stresses have been studied in invertebrates as well as in mammals, we also review the caspase-mediated immune responses that have been identified in the fruit fly Drosophila melanogaster, and suggest that the contribution of caspases to general stress responses is evolutionally conserved.