Spore-FP1 tuberculosis mucosal vaccine candidate is highly protective in guinea pigs but fails to improve on BCG-conferred protection in non-human primates.

Tuberculosis remains a major health threat globally and a more effective vaccine than the current Bacillus Calmette Guerin (BCG) is required, either to replace or boost it. The Spore-FP1 mucosal vaccine candidate is based on the fusion protein of Ag85B-Acr-HBHA/heparin-binding domain, adsorbed on the surface of inactivated Bacillus subtilis spores. The candidate conferred significant protection against Mycobacterium. tuberculosis challenge in naïve guinea pigs and markedly improved protection in the lungs and spleens of animals primed with BCG. We then immunized rhesus macaques with BCG intradermally, and subsequently boosted with one intradermal and one aerosol dose of Spore-FP1, prior to challenge with low dose aerosolized M. tuberculosis Erdman strain. Following vaccination, animals did not show any adverse reactions and displayed higher antigen specific cellular and antibody immune responses compared to BCG alone but this did not translate into significant improvement in disease pathology or bacterial burden in the organs.

Mycobacteria-Specific T Cells Are Generated in the Lung During Mucosal BCG Immunization or Infection With Mycobacterium tuberculosis.

Specific T cell responses are central for protection against infection with M. tuberculosis. Here we show that mycobacteria-specific CD4 and CD8 T cells accumulated in the lung but not in the mediastinal lymph node (MLN) at different time points after M. tuberculosis infection or BCG immunization. Proliferating specific T cells were found in the lung after infection and immunization. Pulmonary, but not MLN-derived CD4 and CD8 T cells, from M. tuberculosis-infected mice secreted IFN-γ after stimulation with different mycobacterial peptides. Mycobacteria-specific resident memory CD4 and CD8 T cells (TRM) expressing PD-1 accumulated in the lung after aerosol infection and intratracheal (i.t.) -but not subcutaneous (s.c.)- BCG immunization. Chemical inhibition of recirculation indicated that TRM were generated in the lung after BCG i.t. immunization. In summary, mycobacteria specific-TRM accumulate in the lung during i.t. but not s.c. immunization or M. tuberculosis infection. Collectively our data suggests that priming, accumulation and/or expansion of specific T cells during BCG immunization and M. tuberculosis infection occurs in the lung.

Impaired dendritic cell differentiation of CD16-positive monocytes in tuberculosis: role of p38 MAPK.

Tuberculosis (TB) is one of the world's most pernicious diseases mainly due to immune evasion strategies displayed by its causative agent Mycobacterium tuberculosis (Mtb). Blood monocytes (Mos) represent an important source of DCs during chronic infections; consequently, the alteration of their differentiation constitutes an escape mechanism leading to mycobacterial persistence. We evaluated whether the CD16(+)/CD16(-) Mo ratio could be associated with the impaired Mo differentiation into DCs found in TB patients. The phenotype and ability to stimulate Mtb-specific memory clones DCs from isolated Mo subsets were assessed. We found that CD16(-) Mos differentiated into CD1a(+) DC-SIGN(high) cells achieving an efficient recall response, while CD16(+) Mos differentiated into a CD1a(-) DC-SIGN(low) population characterized by a poor mycobacterial Ag-presenting capacity. The high and sustained phosphorylated p38 expression observed in CD16(+) Mos was involved in the altered DC profile given that its blockage restored DC phenotype and its activation impaired CD16(-) Mo differentiation. Furthermore, depletion of CD16(+) Mos indeed improved the differentiation of Mos from TB patients toward CD1a(+) DC-SIGN(high) DCs. Therefore, Mos from TB patients are less prone to differentiate into DCs due to their increased proportion of CD16(+) Mos, suggesting that during Mtb infection Mo subsets may have different fates after entering the lungs.

Clinical isolates of Mycobacterium tuberculosis differ in their ability to induce respiratory burst and apoptosis in neutrophils as a possible mechanism of immune escape.

Tuberculosis pathogenesis was earlier thought to be mainly related to the host but now it appears to be clear that bacterial factors are also involved. Genetic variability of Mycobacterium tuberculosis (Mtb) could be slight but it may lead to sharp phenotypic differences. We have previously reported that nonopsonized Mtb H37Rv induce apoptosis of polymorphonuclear neutrophils (PMNs) by a mechanism that involves the p38 pathway. Here we evaluated the capability to induce PMN apoptosis of two prevalent Mtb lineages in Argentina, the Latin America and Mediterranean (LAM), and Haarlem, using the H37Rv as a reference strain. Results showed that LAM strains strongly induced apoptosis of PMN which correlated with the induction of reactive oxygen species (ROS) production and p38 activation. Interestingly, the highly prosperous multidrug-resistant M strain, belonging to the Haarlem lineage, lacked the ability to activate and to induce PMN apoptosis as a consequence of (1) a weak ROS production and (2) the contribution of antiapoptotic mechanisms mediated at least by ERK. Although with less skill, M is able to enter the PMN so that phenotypic differences could lead PMN to be a reservoir allowing some pathogens to prevail and persist over other strains in the community.

Outbreaks of mycobacterium tuberculosis MDR strains induce high IL-17 T-cell response in patients with MDR tuberculosis that is closely associated with high antigen load.

BACKGROUND: The proinflammatory cytokine interleukin 17 (IL-17) plays an important role in immune responses but it is also associated with tissue-damaging inflammation. So, we evaluated the ability of Mycobacterium tuberculosis clinical isolates to induce IL-17 in tuberculosis (TB) patients and in healthy human tuberculin reactors (PPD(+)HD). METHODS: IL-17, interferon γ (IFN-γ), and interleukin 23 (IL-23) receptor expression were evaluated ex vivo and cultured peripheral blood mononuclear cells from TB and PPD(+)HD stimulated with irradiated clinical isolates from multidrug resistant (MDR) outbreaks M (Haarlem family) and Ra (Latin American-Mediterranean family), as well as drug-susceptible isolates belonging to the same families and laboratory strain H37Rv for 48 hours in T-cell subsets by flow cytometry. RESULTS: We observed that: (1) MDR strains M and Ra are stronger IL-17 inducers than drug-susceptible Mtb strains of the Haarlem and Latin American-Mediterranean families, (2) MDR-TB patients show the highest IL-17 expression that is independent on the strain, (3) IL-17 expression is dependent on CD4(+) and CD8(+) T cells associates with persistently high antigen load. CONCLUSIONS: IL-17--producing T cells could play an immunopathological role in MDR-TB promoting severe tissue damage, which may be associated with the low effectiveness of the second-line drugs employed in the treatment.

Paradoxical role of CD16+CCR2+CCR5+ monocytes in tuberculosis: efficient APC in pleural effusion but also mark disease severity in blood.

The role of CD16(-) and CD16(+) Mo subsets in human TB remains unknown. Our aim was to characterize Mo subsets from TB patients and to assess whether the inflammatory milieu from TB pleurisy modulate their phenotype and recruitment. We found an expansion of peripheral CD16(+) Mo that correlated with disease severity and with TNF-α plasma levels. Circulating Mo from TB patients are activated, showing a higher CD14, CD16, and CD11b expression and Mtb binding than HS. Both subsets coexpressed CCR2/CCR5, showing a potential ability to migrate to the inflammatory site. In tuberculous PF, the CD16(+) subset was the main Mo/MΦ population, accumulation that can be favored by the induction of CD16 expression in CD16(-) Mo triggered by soluble factors found in this inflammatory milieu. CD16(+) Mo in PF were characterized by a high density of receptors for Mtb recognition (DC-SIGN, MR, CD11b) and for lipid-antigens presentation (CD1b), allowing them to induce a successful, specific T cell proliferation response. Hence, in tuberculous PF, CD16(+) Mo constitute the main APC population; whereas in PB, their predominance is associated with the severity of pulmonary TB, suggesting a paradoxical role of the CD16(+) Mo subset that depends on the cellular localization.

Evidence of Bacillus thuringiensis intra-serovar diversity revealed by Bacillus cereus group-specific repetitive extragenic palindromic sequence-based PCR genomic fingerprinting.

Bacillus thuringiensis is classified into serovars on the basis of H-flagellar antigens. Several alternative typing methods have been described. Among them, a B. cereus group-specific repetitive extragenic palindromic (Rep)-PCR fingerprinting technique was shown to be discriminative and able to identify B. thuringiensis serovars. The aim of this study was to investigate the genomic diversity and relationship among B. thuringiensis strains collected from different Argentinean ecosystems. Thirty-seven B. thuringiensis reference strains and 131 Argentinean isolates were analyzed using a B. cereus group-specific Rep-PCR. Fourteen different patterns were identified among the Argentinean isolates. Eight could not be associated to any pattern obtained from a reference strain. The pattern identical to the serovar kurstaki HD-1 strain was the most frequently identified in 68 native isolates. The profiles allowed tracing a single dendrogram with two groups and eight main lineages. Some strains showed distinctive patterns despite belonging to the same serovar. An intraspecific diversity resulted from this analysis that was highlighted by this technique since strains from a given serovar showed distinct profiles. This study may help to establish a system of B. thuringiensis classification with a higher discrimination level than established by the H antigen serotyping.

Mycobacterium tuberculosis impairs dendritic cell response by altering CD1b, DC-SIGN and MR profile.

During a chronic infection such as tuberculosis, the pool of tissue dendritic cells (DC) must be renewed by recruitment of both circulating DC progenitors and monocytes (Mo). However, the microenvironment of the inflammatory site affects Mo differentiation. As DC are critical for initiating a Mycobacterium tuberculosis-specific T-cell response, we argue that interference of M. tuberculosis with a correct DC generation would signify a mechanism of immune evasion. In this study, we showed that early interaction of γ-irradiated M. tuberculosis with Mo subverts DC differentiation in vitro. We found that irradiated M. tuberculosis effect involves (1) the loss of a significant fraction of monocyte population and (2) an altered differentiation process of the surviving monocyte subpopulation. Moreover, in the absence of irradiated M. tuberculosis, DC consist in a major DC-specific intercellular adhesion molecule 3-grabbing non-integrin receptor (DC-SIGN(high))/CD86(low) and minor DC-SIGN(low)/CD86(high) subpopulations, whereas in the presence of bacteria, there is an enrichment of DC-SIGN(low)/CD86(high) population. Besides, this population enlarged by irradiated M. tuberculosis, which is characterized by a reduced CD1b expression, correlates with a reduced induction of specific T-lymphocyte proliferation. The loss of CD1molecules partially involves toll-like receptors (TLR-2)/p38 MAPK activation. Finally, several features of Mo, which have been differentiated into DC in the presence of irradiated M. tuberculosis, resemble the features of DC obtained from patients with active tuberculosis. In conclusion, we suggest that M. tuberculosis escapes from acquired immune response in tuberculosis may be caused by an altered differentiation into DC leading to a poor M. tuberculosis-specific T-cell response.