Heterologous Boost Following Mycobacterium bovis BCG Reduces the Late Persistent, Rather Than the Early Stage of Intranasal Tuberculosis Challenge Infection

Abstract

Adults are the leading population affected by tuberculosis (TB) epidemic and death. Developing an effective vaccine against adult TB is urgently needed. Mycobacterium bovis Bacillus Calmette-Guerin (BCG) prime-heterologous boost strategy has been explored extensively to protect adults against primary TB infection, but the majority of experimental regimens have not improved the protection primed by the BCG vaccine. The reason attributed to the failure remains unknown. In this study, CTT3H-based vaccines, namely DMT adjuvanted CTT3H subunit or DNA vaccine (pCTT3H-DMT), and recombinant adenovirus rAdCTT3H were constructed. Protective efficacy and immunogenicity of BCG prime-CTT3H based boosters were compared in C57BL/c mice models of primary or late persistent TB infection. Similar protective efficacy against early intranasal infection was provided by different CTT3H-based vaccines alone in vaccinated mice, and their protection was inferior to that of the BCG vaccine. In addition, CTT3H-based heterologous boosters did not enhance the protection conferred by the BCG vaccine against primary infection. However, all of these three boosters provided stronger protection against late persistent TB infection than BCG alone, regardless of vaccine types. Although BCG prime-boosters elicited Th1-biased responses to the antigen CTT3H, the number of CTT3H-sepcific IFN-γ-expressing TEM (CD62LloCD44hi) and IL-2-expressing TCM (CD62LhiCD44hi) cells in the spleen was not improved before exposure to Mycobacterium tuberculosis infection. In contrast, IFN-γ+ TEM and IL-2+ TCM cells in spleens, especially in lungs were significantly increased in BCG prime-boosters after exposure vaccination. Our results indicate that BCG prime-boost strategy might be a promising measure for the prevention against late persistent TB infection by induction of IFN-γ+ TEM and IL-2+ TCM cells in the lung, which can be used as alternative biomarkers for guiding the clinical practice and future development of TB vaccine for adults.

Recombinant BCG With Bacterial Signaling Molecule Cyclic di-AMP as Endogenous Adjuvant Induces Elevated Immune Responses After Mycobacterium tuberculosis Infection

“…Elevated c-di-AMP in rBCG-DisA had changed the immunogenicity of BCG from our results, but the enhancement may be not sufficient to be distinguished with the immune responses induced by BCG alone. The Mtb infection model could be established by intravenous (54–56), aerosol (25, 48), or intranasal (47, 57) infection routes. In this study, we used intravenous infection of mice as a model for evaluation study, which resulted in much higher bacteria loads than human tuberculosis.…”

Enhanced tuberculosis clearance through the combination treatment with recombinant adenovirus-mediated granulysin delivery

“…The recombinant shuttle plasmid pDChGLs, containing the tandem-fusion of the sequence encoding the signal peptide of tissue plasminogen activator (tPA) and human granulysin (238 bp) was synthesized by Obio Technology Company (Shanghai, China). As shown in Figure S1 A , rAd5-based rAdhGLs, expressing granulysin extracellularly, was packaged and constructed by co-transfecting plasmids pDChGLs and pBHGloxΔE1,3Cre (Microbix, Mississauga, ON, Canada) (1:1) into human embryonic kidney 293 (HEK293, ATCC ® CRL-1573 TM ) cells with Lipofactamine 2000 reagent (Invitrogen, Carlsbad, CA, USA), as previously described 9 , 10 . rAdhGLs was rescued by homologous recombination, amplified in HEK293 cells, and purified with the standard method of CsCl density gradient centrifugation.…”

Deletion of BCG_2432c from the Bacillus Calmette‐Guérin vaccine enhances autophagy‐mediated immunity against tuberculosis

“…The residual BCG strains in the organs were inhibited using 2 μg/ml 2-thiophenecarboxylic acid hydrazide (Sigma-Aldrich). As described previously, 24,25 the bacterial load of the spleen and lungs and lung histopathological changes and scores were compared to evaluate the protective effect among different groups. A two-tailed Student's t-test was performed to test two different groups.…”

“…Memory T cells, especially IL-2 + CD4 + T CM cells are closely associated with vaccine-induced long-term protection against adult TB. 25 The absolute number of Ag85B-specific IL-2-positive CD62L hi CD44 hi (T CM ) cells and IFNγ-expressing CD62L lo CD44 hi (T EM ) cells (Figure S6) in the spleen and lungs of both BCG WT -and ΔBCG_2432cvaccinated mice were compared 28 and 60 days after immunization (Figure 6A). On day 28, IFNγ + CD4 + T EM and IL-2 + T CM cells appeared in the spleen of BCG WT -and ΔBCG_2432c-vaccinated mice.…”