What specific mechanisms does Mycobacterium tuberculosis use to evade the host immune system?6 answersMycobacterium tuberculosis (Mtb) employs a multifaceted strategy to evade the host immune system, ensuring its survival, replication, and transmission. One primary mechanism involves the manipulation of host innate immune responses through the modulation of cytosolic nucleic acid-sensing pathways, affecting cellular events such as membrane trafficking, cell death, and autophagy. Mtb also exploits the host's immune responses by evading and taking advantage of these responses to maintain a state of equilibrium, characterized by immunological control and bacterial persistence, through the secretion of protein and lipid effectors that influence macrophage functions and inflammatory responses.
At the molecular level, Mtb interferes with the signaling functions of host immune molecules by exploiting the host ubiquitination system. For instance, the host E3 ubiquitin ligase ANAPC2 interacts with the mycobacterial protein Rv0222, suppressing the expression of proinflammatory cytokines, thereby inhibiting the host's ability to mount an effective immune response. Additionally, Mtb induces DNA hypermethylation in the host, particularly affecting the IL-2/STAT5, TNF/NF-κB, and IFN-γ signaling pathways, which results in decreased immune responsiveness.
Mtb also directly inhibits the activation of the NLRP3 inflammasome and pyroptosis in macrophages, a critical component of the host's innate immune defense, through the action of the serine/threonine kinase PknF. The pathogen's ability to evade immune defense is further complicated in patients with conditions like diabetes mellitus, where dysregulated inflammation and tissue remodeling occur. Mtb's genome encodes PE/PPE/PE_PGRS proteins that modulate immune responses, aiding in immune evasion. The bacterium also alters the expression of host noncoding RNAs (ncRNAs), impacting immune response modulation and contributing to its pathogenesis. Despite the production of IFNγ, a potent inducer of cell-autonomous immunity, Mtb resists IFNγ-mediated antimicrobial responses, partly through evasion of Guanylate binding proteins (GBPs)-mediated immunity, facilitated by the ESX1 secretion system. Lastly, Mtb's interaction with neutrophils and macrophages can lead to the formation of neutrophil extracellular traps (NETs) and macrophage extracellular traps (METs), which, while part of the host defense, can also cause tissue damage and contribute to the pathogen's evasion strategies.
What are the specific molecular mechanisms that Mycobacterium tuberculosis uses to evade the immune system's response?5 answersMycobacterium tuberculosis (Mtb) employs various molecular mechanisms to evade the host immune response. These include the manipulation of host immune regulatory machinery, such as intranuclear regulatory mechanisms, costimulatory molecules, the ubiquitin system, and cellular intrinsic immune components. Additionally, Mtb possesses an arsenal of protein and lipid effectors that influence macrophage functions and inflammatory responses, aiding in immune evasion and persistence within the host. Furthermore, Mtb can alter the expression of noncoding RNAs, potentially leading to dysregulated biological processes that contribute to its pathogenesis and long-term survival within the host. The bacterium's ability to evade immune responses and establish persistent infections underscores the importance of understanding these mechanisms for developing more effective tuberculosis prevention, diagnosis, and treatment strategies.
What are the TB vaccines that induce innate immune responses?4 answersThe TB vaccines that induce innate immune responses include recombinant dormancy-associated Mtb proteins Rv2659c and Rv1738, which activate Toll-like receptors (TLRs) 2 and 4 and stimulate the production of inflammatory cytokines. Another vaccine candidate, BCGΔBCG1419c, has been shown to elicit a longer-lasting and potentially less inflammatory immune response compared to BCG, with lower frequencies of exhausted CD4+ T helper cells and higher frequencies of IL10-producing T cells. Additionally, the BCG Mexico and Phipps strains have been found to induce innate inflammatory and antimicrobial responses in macrophages, including the production of tumor necrosis factor (TNF)-α, type I interferon (IFN-I), and IFN-γ. The induction of trained immunity, a form of innate immune memory, has also been associated with the beneficial effects of BCG vaccination against TB. Overall, these findings suggest that targeting innate immune responses may be valuable for the development of effective TB vaccines.
What are the molecular mechanisms of tuberculosis?5 answersThe molecular mechanisms of tuberculosis involve the development of drug-resistant strains, immune evasion strategies, and host-pathogen interactions. Drug-resistant strains of tuberculosis, including multidrug-resistant (MDR), extensively drug-resistant (XDR), and totally drug-resistant (TDR) strains, have emerged due to inappropriate TB practices and inadequate treatment. Mycobacterium tuberculosis (Mtb) has powerful molecular structures and drug resistance pathways that contribute to the emergence of these strains. During infection, M. tuberculosis suppresses host gene transcription, particularly genes involved in pathogen sensing, phagocytosis, and antigen processing. The survival of M. tuberculosis within infected cells is facilitated by a complex immune "molecular off switch" controlled by microRNAs and Alu regulatory elements. The pathophysiology of tuberculosis involves various aspects such as cell-surface interactions, phagosome inhibition, oxidative stress, secretion systems, proteolysis, immunopathogenesis, interactions with HIV, persistence, and drug resistance. The successful strategy of M. tuberculosis in circumventing host defenses, persisting in the host, and developing resistance is still not fully understood.
What is Host immune response to Tuberculosis bacili?5 answersThe host immune response to Mycobacterium tuberculosis (MTB) infection involves a complex interplay between immune cells and the pathogen. The initial response is mediated by innate immunity, including phagocytosis by macrophages and dendritic cells, leading to the activation of adaptive immune responses. The adaptive immune response is characterized by the production of cytokines, such as IFN-γ, which enhance phagocytosis and control bacterial growth. However, MTB has evolved mechanisms to evade the host immune response, leading to persistence and limiting clearance by the host. Understanding the immune response is crucial for developing effective preventive and therapeutic strategies against MTB. The interaction between MTB and the host immune system occurs within the lung, where complex processes determine the outcome of infection. Overall, the host immune response plays a critical role in controlling MTB infection and determining the clinical course and pathology of tuberculosis.
Which genes are involved in virulence factor for Mycobacteriun tuberculosis?5 answersSeveral genes are involved in the virulence factors of Mycobacterium tuberculosis (Mtb). One important gene is ESAT-6, which is secreted by the pathogen and plays a role in hijacking macrophage function to establish successful infection and transmission. Another gene, hbhA, is responsible for adherence of Mtb to non-phagocytic cells and the formation of intracytosolic lipid inclusions. Additionally, there are genes involved in modulating the physiology of Mtb to evade the host immune system and persist within macrophages, such as those involved in cell entry, fatty acid degradation, mycolic acid synthesis, and phagosome acidification inhibition. Furthermore, the gene Rv2577 has been identified as a potential alkaline phosphatase/phosphodiesterase enzyme, playing a role in Mtb virulence. These genes and their functions are crucial for the pathogenicity and survival of Mtb.