The role of complement system and the immune response to tuberculosis infection

Copyright: © 2021 by the authors. The complement system orchestrates a multi-faceted immune response to the invading pathogen, Mycobacterium tuberculosis. Macrophages engulf the mycobacterial bacilli through bacterial cell surface proteins or secrete proteins, which activate the complement pathway. The classical pathway is activated by C1q, which binds to antibody antigen complexes. While the alternative pathway is constitutively active and regulated by properdin, the direct interaction of properdin is capable of complement activation. The lectin-binding pathway is activated in response to bacterial cell surface carbohydrates such as mannose, fucose, and N-acetyl-D-glucosamine. All three pathways contribute to mounting an immune response for the clearance of mycobacteria. However, the bacilli can reside, persist, and evade clearance by the immune system once inside the macrophages using a number of mechanisms. The immune system can compartmentalise the infection into a gran-ulomatous structure, which contains heterogenous sub-populations of M. tuberculosis. The granuloma consists of many types of immune cells, which aim to clear and contain the infection whilst sacrificing the affected host tissue. The full extent of the involvement of the complement system during infection with M. tuberculosis is not fully understood. Therefore, we reviewed the available literature on M. tuberculosis and other mycobacterial literature to understand the contribution of the complement system during infection

The PE-PPE Family of Mycobacterium tuberculosis: Proteins in Disguise

Data Availability: The authors declare no data was used for the work reported in this paper.Copyright © 2022 The Author(s). Mycobacterium tuberculosis has thrived in parallel with humans for millennia, and despite our efforts, M. tuberculosis continues to plague us, currently infecting a third of the world’s population. The success of M. tuberculosis has recently been attributed, in part, to the PE-PPE family; a unique collection of 168 proteins fundamentally involved in the pathogenesis of M. tuberculosis. The PE-PPE family proteins have been at the forefront of intense research efforts since their discovery in 1998 and whilst our knowledge and understanding has significantly advanced over the last two decades, many important questions remain to be elucidated. This review consolidates and examines the vast body of existing literature regarding the PE-PPE family proteins, with respect to the latest developments in elucidating their evolution, structure, subcellular localisation, function, and immunogenicity. This review also highlights significant inconsistencies and contradictions within the field. Additionally, possible explanations for these knowledge gaps are explored. Lastly, this review poses many important questions, which need to be addressed to complete our understanding of the PE-PPE family, as well as highlighting the challenges associated with studying this enigmatic family of proteins. Further research into the PE-PPE family, together with technological advancements in genomics and proteomics, will undoubtedly improve our understanding of the pathogenesis of M. tuberculosis, as well as identify key targets/candidates for the development of novel drugs, diagnostics, and vaccines. Graphical abstract [available online at: https://ars.els-cdn.com/content/image/1-s2.0-S0171298522001474-ga1_lrg.jpg] Functions of the PE-PPE family. A diagrammatic representation of the functions elicited by the proline-glutamic acid (PE)-proline-proline-glutamic acid (PPE) family proteins. Initially, the PE-PPE family due to its polymorphic and repetitive nature was considered a source of genetic and antigenic variation in Mycobacterium tuberculosis (M. tuberculosis) (Cole et al., 1998). However, PE-PPE proteins have since been assigned a wide range of diverse roles, which are outlined in the figure. The functions of the PE-PPE family are extensive, including modulating host immune responses, subverting host defence strategies, resisting diverse stresses of the host, and manipulating host cell fates, ultimately to ensure the survival of M. tuberculosis. The arrows indicate the PE-PPE-induced effects whereas the blunt-end arrows indicate the PE-PPE-inhibited effects. Chains of arrows and blunt-end arrows also highlight the functional pathways and consequential effects of PE-PPE-elicited functions. Abbreviations: cluster of differentiation (CD); major histocompatibility complex (MHC); interleukin (IL); interferon-gamma (IFN-ɣ); transforming growth factor-beta (TGF-β); tumour necrosis factor-alpha (TNF-α); sodium dodecyl-sulfate (SDS); polymorphic GC-rich (PE-PGRS); major polymorphic tandem repeat (MPTR).The authors declare no funding was used for the work reported in this paper

Lepiniopsis ternatensis sap stimulates fibroblast proliferation and down regulates macrophage TNF-α secretion

Christensen Fund for Melanesi

Functional genetic variation in pe/ppe genes contributes to diversity in Mycobacterium tuberculosis lineages and potential interactions with the human host

Data availability statement: The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/Supplementary material available online at https://www.frontiersin.org/articles/10.3389/fmicb.2023.1244319/full#SM1 ..Copyright © 2023 Gómez-González, Grabowska, Tientcheu, Tsolaki, Hibberd, Campino, Phelan and Clark. Introduction: Around 10% of the coding potential of Mycobacterium tuberculosisis constituted by two poorly understood gene families, the pe and ppe loci, thought to be involved in host-pathogen interactions. Their repetitive nature and high GC content have hindered sequence analysis, leading to exclusion from whole-genome studies. Understanding the genetic diversity of pe/ppe families is essential to facilitate their potential translation into tools for tuberculosis prevention and treatment. Methods: To investigate the genetic diversity of the 169 pe/ppe genes, we performed a sequence analysis across 73 long-read assemblies representing seven different lineages of M. tuberculosis and M. bovis BCG. Individual pe/ppe gene alignments were extracted and diversity and conservation across the different lineages studied. Results: The pe/ppe genes were classified into three groups based on the level of protein sequence conservation relative to H37Rv, finding that >50% were conserved, with indels in pe_pgrs and ppe_mptr sub-families being major drivers of structural variation. Gene rearrangements, such as duplications and gene fusions, were observed between pe and pe_pgrs genes. Inter-lineage diversity revealed lineage-specific SNPs and indels. Discussion: The high level of pe/ppe genes conservation, together with the lineage-specific findings, suggest their phylogenetic informativeness. However, structural variants and gene rearrangements differing from the reference were also identified, with potential implications for pathogenicity. Overall, improving our knowledge of these complex gene families may have insights into pathogenicity and inform the development of much-needed tools for tuberculosis control.PG-G is funded by an MRC-LID PhD studentship. JP is funded by a Newton Institutional Links Grant (British Council, No. 261868591). TGC was funded by the Medical Research Council United Kingdom (Grant Nos. MR/M01360X/1, MR/N010469/1, MR/R025576/1, MR/R020973/1, and MR/X005895/1). SC was funded by Medical Research Council United Kingdom grants (ref. MR/M01360X/1, MR/R025576/1, MR/R020973/1, and MR/X005895/1). LT is funded by the FIC-NIH (K43TW011125) and the Royal Society (FLR\R1\191166 and FCG\R1\201022)

Molecular epidemiology and evolutionary genetics of Mycobacterium tuberculosis in Taipei

<p>Abstract</p> <p>Background</p> <p>The control of tuberculosis in densely populated cities is complicated by close human-to-human contacts and potential transmission of pathogens from multiple sources. We conducted a molecular epidemiologic analysis of 356 <it>Mycobacterium tuberculosis </it>(MTB) isolates from patients presenting pulmonary tuberculosis in metropolitan Taipei. Classical antibiogram studies and genetic characterization, using mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing and spoligotyping, were applied after culture.</p> <p>Methods</p> <p>A total of 356 isolates were genotyped by standard spoligotyping and the strains were compared with in the international spoligotyping database (SpolDB4). All isolates were also categorized using the 15 loci MIRU-VNTR typing method and combin with <it>NTF </it>locus and RD deletion analyses.</p> <p>Results</p> <p>Of 356 isolates spoligotyped, 290 (81.4%) displayed known spoligotypes and 66 were not identified in the database. Major spoligotypes found were Beijing lineages (52.5%), followed by Haarlem lineages (13.5%) and EAI plus EAI-like lineages (11%). When MIRU-VNTR was employed, 140 patterns were identified, including 36 clusters by 252 isolates and 104 unique patterns, and the largest cluster comprised 95 isolates from the Beijing family. The combination of spoligotyping and MIRU-VNTR revealed that 236 (67%) of the 356 isolates were clustered in 43 genotypes. Strains of the Beijing family was more likely to be of modern strain and a higher percentage of multiple drug resistance than other families combined (P = 0.08). Patients infected with Beijing strains were younger than those with other strains (mean 58.7 vs. 64.2, p = 0.02). Moreover, 85.3% of infected persons younger than 25 years had Beijing modern strain, suggesting a possible recent spread in the young population by this family of TB strain in Taipei.</p> <p>Conclusion</p> <p>Our data on MTB genotype in Taipei suggest that MTB infection has not been optimally controlled. Control efforts should be reinforced in view of the high prevalence of the Beijing strain in young population and association with drug resistance.</p

Complement dependent and independent interaction between bovine conglutinin and Mycobacterium bovis BCG: implications in bovine tuberculosis

© 2019 Mehmood, Kouser, Kaur, Holmskov, Al-Ahdal, Sim, Kishore and Tsolaki. Bovine conglutinin, the first animal collectin to be discovered, is structurally very similar to Surfactant Protein D (SP-D). SP-D is known to interact with Mycobacterium tuberculosis, and the closely-related M. bovis, the causative agent of bovine tuberculosis. We speculated that due to the overall similarities between conglutinin and SP-D, conglutinin is likely to have a protective influence in bovine tuberculosis. We set out to investigate the role of conglutinin in host-pathogen interactions during mycobacterial infection. We show here that a recombinant truncated form of conglutinin (rfBC) composed of the neck and C-type lectin domains, binds specifically and in a dose-dependent manner to the model organism Mycobacterium bovis BCG. rfBC showed significant direct bacteriostatic effect on the growth of M. bovis BCG in culture. In addition, rfBC inhibited the uptake of M. bovis BCG by THP-1 macrophages (human monocyte lineage cell line) and suppressed the subsequent pro-inflammatory response. Conglutinin is well known as a ligand of the complement activation product, iC3b. rfBC was also able to inhibit the uptake of complement-coated M. bovis BCG by THP-1 macrophages, whilst maintaining the pro-inflammatory response. It is likely that rfBC inhibits the phagocytosis of mycobacteria by two distinct mechanisms: firstly, rfBC interferes with mannose receptor-mediated uptake by masking lipoarabinomannan (LAM) on the mycobacterial surface. Secondly, since conglutinin binds iC3b, it can interfere with complement receptor-mediated uptake via CR3 and CR4, by masking interactions with iC3b deposited on the mycobacterial surface. rfBC was also able to modulate the downstream pro-inflammatory response in THP-1 cells, which is important for mobilizing the adaptive immune response facilitating containment of mycobacterial infection. In conclusion, we show that conglutinin possesses complement-dependent and complement-independent anti-mycobacterial activities, interfering with both the known major mechanisms of mycobacterial uptake by macrophages. As mycobacteria are specialized intracellular pathogens, conglutinin may inhibit M. bovis and M. tuberculosis from establishing an intracellular niche within macrophages, and thus, negatively affect the long-term survival of the pathogen in the host

Two new rapid SNP-typing methods for classifying Mycobacterium tuberculosis complex into the main phylogenetic lineages

There is increasing evidence that strain variation in Mycobacterium tuberculosis complex (MTBC) might influence the outcome of tuberculosis infection and disease. To assess genotype-phenotype associations, phylogenetically robust molecular markers and appropriate genotyping tools are required. Most current genotyping methods for MTBC are based on mobile or repetitive DNA elements. Because these elements are prone to convergent evolution, the corresponding genotyping techniques are suboptimal for phylogenetic studies and strain classification. By contrast, single nucleotide polymorphisms (SNP) are ideal markers for classifying MTBC into phylogenetic lineages, as they exhibit very low degrees of homoplasy. In this study, we developed two complementary SNP-based genotyping methods to classify strains into the six main human-associated lineages of MTBC, the 'Beijing' sublineage, and the clade comprising Mycobacterium bovis and Mycobacterium caprae. Phylogenetically informative SNPs were obtained from 22 MTBC whole-genome sequences. The first assay, referred to as MOL-PCR, is a ligation-dependent PCR with signal detection by fluorescent microspheres and a Luminex flow cytometer, which simultaneously interrogates eight SNPs. The second assay is based on six individual TaqMan real-time PCR assays for singleplex SNP-typing. We compared MOL-PCR and TaqMan results in two panels of clinical MTBC isolates. Both methods agreed fully when assigning 36 well-characterized strains into the main phylogenetic lineages. The sensitivity in allele-calling was 98.6% and 98.8% for MOL-PCR and TaqMan, respectively. Typing of an additional panel of 78 unknown clinical isolates revealed 99.2% and 100% sensitivity in allele-calling, respectively, and 100% agreement in lineage assignment between both methods. While MOL-PCR and TaqMan are both highly sensitive and specific, MOL-PCR is ideal for classification of isolates with no previous information, whereas TaqMan is faster for confirmation. Furthermore, both methods are rapid, flexible and comparably inexpensive

Presence of RD149 Deletions in M. tuberculosis Central Asian Strain1 Isolates Affect Growth and TNFα Induction in THP-1 Monocytes

Central Asian Strain 1 (CAS1) is the prevalent Mycobacterium tuberculosis genogroup in South Asia. CAS1 strains carry deletions in RD149 and RD152 regions. Significance of these deletions is as yet unknown. We compared CAS1 strains with RD149 and concurrent RD149-RD152 deletions with CAS1 strains without deletions and with the laboratory reference strain, M. tuberculosis H37Rv for growth and for induction of TNFα, IL6, CCL2 and IL10 in THP-1 cells. Growth of CAS1 strains with deletions was slower in broth (RD149; p = 0.024 and RD149-RD152; p = 0.025) than that of strains without deletions. CAS1 strains with RD149 deletion strains further showed reduced intracellular growth (p = 0.013) in THP-1 cells as compared with strains without deletions, and also as compared with H37Rv (p = 0.007) and with CAS1 RD149-RD152 deletion strains (p = 0.029). All CAS1 strains induced higher levels of TNFα and IL10 secretion in THP-1 cells than H37Rv. Additionally, CAS1 strains with RD149 deletions induced more TNFα secretion than those without deletions (p = 0.013). CAS1 RD149 deletion strains from extrapulmonary sources showed more rapid growth and induced lower levels of TNFα and IL6 secretion in THP-1 cells than isolates from pulmonary sources. This data suggests that presence of RD149 reduces growth and increases the induction of TNFα in host cells by CAS1 strains. Differences observed for extrapulmonary strains may indicate an adaptation which increases potential for dissemination and tropism outside the lung. Overall, we hypothesise that RD149 deletions generate genetic diversity within strains and impact interactions of CAS1 strains with host cells with important clinical consequences

Phylogeny of Mycobacterium tuberculosis Beijing Strains Constructed from Polymorphisms in Genes Involved in DNA Replication, Recombination and Repair

The original publication is available at http:/www.plosone.orgBackground: The Beijing family is a successful group of M. tuberculosis strains, often associated with drug resistance and widely distributed throughout the world. Polymorphic genetic markers have been used to type particular M. tuberculosis strains. We recently identified a group of polymorphic DNA repair replication and recombination (3R) genes. It was shown that evolution of M. tuberculosis complex strains can be studied using 3R SNPs and a high-resolution tool for strain discrimination was developed. Here we investigated the genetic diversity and propose a phylogeny for Beijing strains by analyzing polymorphisms in 3R genes. Methodology/Principal Findings: A group of 3R genes was sequenced in a collection of Beijing strains from different geographic origins. Sequence analysis and comparison with the ones of non-Beijing strains identified several SNPs. These SNPs were used to type a larger collection of Beijing strains and allowed identification of 26 different sequence types for which a phylogeny was constructed. Phylogenetic relationships established by sequence types were in agreement with evolutionary pathways suggested by other genetic markers, such as Large Sequence Polymorphisms (LSPs). A recent Beijing genotype (Bmyc10), which included 60% of strains from distinct parts of the world, appeared to be predominant. Conclusions/Significance: We found SNPs in 3R genes associated with the Beijing family, which enabled discrimination of different groups and the proposal of a phylogeny. The Beijing family can be divided into different groups characterized by particular genetic polymorphisms that may reflect pathogenic features. These SNPs are new, potential genetic markers that may contribute to better understand the success of the Beijing family. © 2011 Mestre et al.Publishers' Versio

Investigation on Mycobacterium tuberculosis Diversity in China and the Origin of the Beijing Clade

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