MYCOBACTERIUM Tuberculosis immunopathogenesis

immunopathogenesis of mtb

1. Presenter: Dr Ilham Iqbal Moderator:Dr Danish Zahoor

2. taxonomy

3. Mycobacterium tuberculosis Complex M mungi , M orygis

4. MORPHOLOGY OF MYCOBACTERIUM TUBERCULOSIS

5. Cell wall _ mtb

6. Epidemiology

7. Sequelae

8. Mode of transmission : Infectious particles from a TB pt. aerosolised (by coughing ,sneezing or talking) . dry – Inhalation of Droplet Nuclei .(<5µm) remain suspended for long periods. terminal air passages .

9. Other modes : M bovis : ingestion of contaminated milk Skin inoculation from contamination of abrasion in pathologists and lab workers – PROSECTOR’s wart Venereal transmission .

10. Determinants of infection : closeness of contact Degree of severity Duration & intimacy of contact Shared environment Infectiousness of the source Cases with positive smears, laryngeal TB - highly infectious Positive only on culture – less infectious HIV infected TB – Low smear positivity ,hence maybe be less infectious

11. RISK for progression from infection to active disease : 3 to 4 % of infected individuals acquire active tuberculosis during the first year after tuberculin conversion and additional 5% after that . Small inocula – less risk Immunocompromised _more risk

12. Risk factors to disease - HIV -homeless -malnutrition - imunocompromised -renal failure -iv drug abusers smokers -alcoholics - elderly,children - silicosis -crowded (prisons) Risk factors for active tuberculosis : Recent infection Fibrotic lesions

13. Primary v/s Secondary TB

14. Primary tuberculosis Children and Immunocompromised Source of organism : Exogenous Progressive Pulmonary TB Miliary . resembles acute bacterial pneumonia Consolidation of lobe, hilar lymphadenopathy and pleural effusion .

15. Primary infection : Begins with the inhalation of Mycobacteria Ends with T cell mediated immune response Initial focus usually sub pleural and in the middle lung zones First phagocytosed by alveolar macrophages Transported by these cells to hilar lymph nodes Ultimate residum – calcified scar in lung parenchyma & hilar L.N ( GHON COMPLEX,ranke’s )

16. Secondary tuberculosis : mostly years after when host resistance is weakened . Shortly after primary inf. in some cases Re infection or Reactivation of dormant disease Hematogenous spread : Occurs in the apex of the lung 2 special activities of secondary tuberculosis caseous necrosis cavities

17. Primary v/s Secondary

18. Pathogenesis

19. I) MYCOBACTERIAL ENTRY INTO HOST CELLS : Inhaled respiratory droplets Deposited in distal alveoli (<10 %) Receptors present on Phagocytic cells macrophages

20. II) Uptake by Macrophages Interaction between the MTB ligands and the receptors on host cells Initiated by bacterial contact with macrophage multiple receptors involved Receptors include CLR’s ,CR’s ,SR’s Cholesterol promotes phagocytosis

21. CE

22. III) Phagosomal manipulation

23. 1)Prevention of phagolysosome FORMATION : M. tuberculosis grow in an early endosome –like compartment - 1 ) inhibiting PI3P generation on the phagosome . 2) Man LAM , disrupts a calcium dependent calmodulin signalling pathway 3) SapM ,PI3P Phosphatase , decr . PI3P 4) Failure of Phagosome to acidify ( decr . v ATPase , Mycobacterial urease ) 5) impairing the recruitment of active, GTP-bound Rab7 while retaining Rab5. Mycobacterial proteins Ptp A and NdkA impair Rab7 activation .

24. 2) Escape in to the cytosol 5 types of type7 secretion systems (TSSS) The Esx-1 system permeabilizes the phagosomal membrane -- direct cytosolic access to mtb . Encoded by RD1 Effectors : ESAT -6 MEMBRANE DAMAGE CFP-10 BCG vaccine has attenuated Esx -1 system Role in immunity

25. Esx-1 machinery - innate immune receptors in the cytoplasm to gain access to M. tuberculosis constituents activate the inflammasome in the host cytoplasm. uninfected macrophages to foci of infection by inducing matrix metalloproteinase 9 (MMP-9) by nearby non-hematopoietic cells . Adaptive immune response : recognized by both CD 4 and CD 8 T cells .

26. Esx-1 in immunity

27. Possible fates of intracellular Mycobacterium tuberculosis .

28. 3. Role of autophagy Process that sequesters and destroys damaged cell organelles and intracellular MTB .

29. Strategies to inhibit autophagy

30. IV) Events following Phagocytosis Initial stages of infection Host macrophage bacilli multiply Contain bacillary kills macrophages Multiplication non activated monocytes attracted to site ingest bacilli

31. Access to lung parenchyma Through infected macrophages Directly infecting epithelial cells During the earliest stage of primary tuberculosis (<3weeks ) bacteria proliferate in the pulmonary alveolar macrophages and air spaces , resulting in bacteremia and seeding of multiple sites Most people at this stage are asymptomatic or have a mild flu like illness .

32. PRINCIPAL LESIONS in lung parenchyma EXUDATIVE PROLIFERATIVE /PRODUCTIVE TYPE ACUTE inflammatory ,EDEMA fluid Chronic granuloma Lung tissue Peri fibrous tissue and Caseous necrosis /tubercle Neutrophils , foll by monocytes Cavity /Calcification Heal / massive necrosis Tuberculin test positive

33. V) Host response After 2-4 wks of infection, 2 host responses develop Tissue damaging macrophage activating response response DTH to various bacillary cell mediated antigens phenomenon Destroys nonactivated macrophages activates macrophag that contain multiplying bacilli that kills digesting tubercle bacilli

34. Tissue damaging response Infected macrophages chemokines attract inactivated monocytes , lymphocytes, neutrophils The pathological features of TB are the result of degree of hypersensitivity & the local concentration of antigen

35. CMI response With the development of effective CMI Bacillary Ags processed by macrophages stimulate T cells to secrete a no. of lymphokines Activation of local macrophages Organization of lymphocytes, macrophages, Langerhans giant cells, fibroblast Granuloma formation

36. GRANULOMAS :

37. granuloma

38. Granulomatous inflammation Macrophages activated by INF γ differentiate to “ epitheloid histiocytes ” Some epitheloid cells fuse to form giant cells, peripheral nuclei . Haults infection in some ,where as in other with risk factors results in caseation and necrosis . TNF and chemokines : recruit more monocytes

39. MGC s MGCs : associated with virulent mycobacteria . MGC formation depends on: PIMs, lipomannan (LM), TDM β1 integrin expression expression of disintegrin metalloproteinase ADAM9. granulomas contain both persistent infection and accumulation of immune cells , represent a stalemate between the host and the pathogen, implying a benefit to both.

40. OUTCOME

41. Resolution Can be by innate or adaptive immune responses In case of efficient CMI infection arrested permanently at this point Granuloma subsequently heal, leaving small fibrosis and calcified lesions

42. LTBI

43. Post 3 weeks ,MTB Antigens enter lymphnodes presented to T cells . TH1 cells activates macrophages to bactericidal IL 12 produced by DC’s – Differentiation of TH1 cells T Cell Priming

44. Active pulmonary tuberculosis If infection is not controlled Latently infected persons immune system becomes weak granuloma centre becomes liquefied Serves as rich medium in which bacteria can replicate in an uncontrolled manner

45. Tissue destruction cavity formation bronchial wall & blood vessel invaded & destroyed May spread to other tissue via lymphatics and blood miliary or extra Tb

46. S pread Direct extension Lymphohematogenous Lymphatics to regional lymphnodes , farther to blood stream , inturn , distributes bacilli to organs ( miliary ) Bronchi Caseating lesion discharges its contents into bronchus GIT If swallowed passed to stomach and intestines

47. Innate Adaptive Immune responses to infection

48. PAMP OF MTB innate immune receptors Activation of NF- Κ B pathway Proinflammatory cytokines Recruitment of cells Role of innate immunity

49. DC- MHCII CD4-T CELLS IFN- γ Macrophage Activation Phagocytosis Activated macrophages TNF γ PDGF TGF β FGF

50. DC- MHCI Infected macrophages TH2 ACTIVATION of CD8 CELLS KILLING OF BACTERIA

51. ROLE OF IFN- γ activates cells to kill a significant fraction of the bacteria by activating expression of nitric oxide synthase 2 production of reactive nitrogen intermediates ( RNI ) IFN- γ also enhances phagosome maturation Autophagy

52. Role of vit D Vitamin D3 induces transcription of the nuclear vitamin D receptor transcription of the gene encoding cathelicidin , precursor of LL-37 protein -can directly kill M. tuberculosis . Vitamin D deficiency is associated with active TB in humans

53. ROLE OF TNF TNF : activation of macrophages for killing of intracellular mycobacteria and to modulate apoptosis of infected cells immunopathology of TB, Restrict growth of the bacteria within macrophages, limiting the spread of the infection

54. Host susceptibility to disease Genetic deficiency in IL 12 and IFN γ pathway vulnerable to severe mycobacterial disease Latent to active ? Neutrophils in blood of active TB express Interferon responsive genes that correspond to extent of lung disease monitored by radiographic analysis .

55. VIRULENCE FACTORS Mycolic acid (C78 _C90 ) Mycoside (GLYCOLIPID ) Cord Factor .(TDM) Sulphatides . Wax D Lipo-Arabino Mannan (LAM) . Heat Shock Protein . Mac-1 Integrin . Antigen 85 Complex .

56. VIRULENCE FACTORS

57. Cell secretion and envelope proteins exposed to environment Virulence factor comment Cord factor ( Trehalose 6,6 dimycolate ) Intiates caseation necrosis , chronic granulomas, inhibits killing by macrophages , inhibits migration of leucocytes CFP HSPX/ Acr ESAT 6 /CFP 10 19 KDP Glutamine synthetase

58. cell wall components VIRULENCE FACTOR COMMENT ERP Exported repetitive protein MAS Mycoserosic acid synthetase Fadd 26/28 Fatty acid degradation Mmp L7 Conserved transmembrane transport protein FBP A Fibronectin binding protein, mycolyltransferese PCA : methyl tranferase LAM Depression of interferons Scavenges oxygen free radicles

59. Enzymes VIRULENCE FACTORS Lipid metabolism Icl Isocitrate lyase lipase Amino acid and purine LEUD,TRPD,TROC,TURC Metal uptake ( iron,Mg ) MbtC , MpTpB Anaerobic respiration and oxidative stress proteins Nitrate reductase , kat G rRNA transcription carD protein

60. HIV AND TB

61. Effects of HIV virus on TB granuloma HIV infection increases the frequency of extrapulmonary TB fewer lymphocytes and epithelioid macrophages, poorer cellular organization, and large areas of necrosis larger number of acid-fast bacilli . lower frequency of sputum smear positivity IRIS syndrome

62. Tnf factor antagonist’ s reactivate latent TB . monoclonal antibodies Infliximab Adalimumab Receptor blocker Etanercept

63. Diabetes and TB In addition to increasing the risk to develop active TB, DM increases TB disease severity Diabetes is associated with _ diminished Th1 and Th17 responses in latent TB, which might confer increased susceptibility to development of disease exaggerated pro-inflammatory response in active disease, which might worsen TB pathology

64. Smoking and TB Cigarette smoke is associated with compromised function of alveolar macrophages inhibition of Th1 activation and enhancement of regulatory T cell activation polarization of recruited macrophages to an immuno -suppressive phenotype which might promote the development of active disease

65. Key messages TB infection and disease is a spectrum rather than a binary outcome Innate and adaptive immune responses are crucial for protective immunity to TB disease The granuloma is the hallmark of TB infection and disease and plays a central role in TB pathogenesis The balance between inflammatory and anti-inflammatory factors drives the degree of pathology in TB Reactivation is the common mechanism of TB disease occurrence

66. THANK YOU