Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Interferones

2,480 views

Published on

Interferones

Published in: Health & Medicine
  • Be the first to comment

Interferones

  1. 1. Interferons Dr. Kanwal Deep Singh Lyall
  2. 2. • Immune system • Cytokines • Definition • History • Classification • Functions • Components • Mechanism of action • Negative regulators & antagonists • Applications • Adverse effects • References
  3. 3. Immune System
  4. 4. Immunity Innate Acquired natural Artificial Active passive Active passive Antigens or pathogens entering naturally Immune response Antibodies (placental or colostrum) Antigen introduction (vaccines) Performed antibodies (Ig)
  5. 5. INNATE IMMUNITY Rapid responses to a broad range of microbes ACQUIRED IMMUNITY Slower responses to specific microbes External defenses Internal defenses Skin Mucous membranes Secretions Phagocytic cells Antimicrobial proteins Inflammatory response Natural killer cells Humoral response (antibodies) Cell-mediated response (cytotoxic lymphocytes) Invading microbes (pathogens) Innate & Acquired Immunity
  6. 6. Innate Immune Response • Activated rapidly and functions within hours infection • Considerable interplay occurs between the adaptive and innate immune defenses. • Important components are • cytokines • complement • collectins • natural killer (NK) cells
  7. 7. Nonspecific Host Defenses & Host Systems • Nonspecific Host Defenses – act on any type of invading agent • Types of Nonspecific Defenses • Physical Barriers • Chemical Barriers • Cellular Defenses • Inflammation • Fever • Molecular Defenses
  8. 8. Cytokines • Regulatory proteins that mediate intercellular communication during an antiviral defense • 1st indicators of host infection • Paracrine, autocrine, endocrine • control inflammation, induce antiviral state in cells & regulate adaptive immune response. • Exert activities by binding to specific receptors & activating gene expression • Interferons are the members of cytokine family
  9. 9. Definition • Interferons (IFNs) are natural cell-signaling proteins produced by the cells of immune system of most vertebrates in response to challenges such as viruses, parasites & tumor cells • Belong to large class of glycoproteins k/a cytokines • Produced by a wide variety of cells in response to ds-RNA, a key indicator of viral infection.
  10. 10. History
  11. 11. • Japanese virologists , Yasu-ichi Nagano & Yasuhiko Kojima - Institute for Infectious Diseases at university of Tokyo • Improved small pox vaccine - rabbit-skin or testis previously inoculated with UV- inactivated virus - inhibition of viral growth when re-infected at same site with live virus • some inhibitory factor & began to characterize it • published these findings in 1954
  12. 12. • British virologist Alick Isaacs & Swiss researcher Jean Lindenmann, - National Institute Of Medical Research, London • Noticed an interference effect caused by heat- inactivated influenza virus on growth of live influenza virus in chicken egg membranes in a nutritive solution chorioallantoic membrane
  13. 13. • Published results in 1957, • In this paper coined term ‘interferon’ • Today that specific interfering agent is k/a a ‘Type I interferon’
  14. 14. Classification
  15. 15. IFNs Type I (viral IFNs) IFN α (leucocytes) IFN β (fibroblasts) IFN ω (leucocytes) IFN τ (trophoblasts) •Induced by viral infections •Have different binding affinities but similar biological effects Type II (immune IFNs) IFN γ •Mitogenic or antigenic stimuli, inflammatory stimuli •NK, CD4 TH1, CD8 B cells • Production controlled by cytokines secreted by IL 12 & 18
  16. 16. General properties • Species specific , not virus specific • Inactivated by proteolytic enzymes not nuclease & lipases • Resist heating @ 56- - 60° c x 30 – 60 mnts • Stable at Ph 2-10 (not γ, labile at ph 2) • Mol. Weight 17000 • Non-dialysable & non-sedmentable • Poorly antigenic • Potency expressed in IU/ml • Non-toxic , diffuses freely in body • Wide spectrum antiviral activity
  17. 17. Inducers Viral • Live viruses • Attenuated viruses • ds DNA Non-virals • Mycobacterial • Fungi • Protozoa • Endotoxins • Phytoagglutinins • Polyribonucleotides • Polyphosphates • Polysulphates • Prayons
  18. 18. Biological effects • Anti-viral - resistance to virus infec. • Antimicrobial – resistance to i/c pathogens – toxoplasma, chalmydia • Cellular effects -Negative cell growth regulator & inhibits proliferations ,inhibits DNA & protein synthesis • Increased expression of MHC antigens • Immunomodulator – enhanced cytotoxity of NK, K & T cells • Activation of macrophage cytocidal activity • Modulation of antibody formation • Activation of supp. T cells & suppression of DTH
  19. 19. • Inhibition of tumor cell growth • Activation of T and natural killer • Cell cytotoxicity, • Stimulation of macrophages • Up-regulation of cell surface MHC class I molecules • Promotion of T helper type 1 responses • Inhibition of angiogenesis
  20. 20. Immunomodulation Effects • Activate NK cells • Increase MHC class I expression • Activate macrophages • Kill cells • Increase MHC II expression, antigen • Presentation to helper T cells
  21. 21. IFN α , IFN β • IFN α produced by leukocytes • IFN β produced by fibroblasts • Both bind to interferon cell receptors type 1 • Both encoded on chromosome 9 • Different binding affinities but similar biological effects • Viral infection is stimulus for expression • Used to mobilize 1st line of defense • Largest group and are secreted by almost all cell types
  22. 22. IFN ω • Antigenically distinct from ifnα • Antiviral & antiproliferative activity • Intratumoral therapy reduces growth of human tumors
  23. 23. IFN-τ • Responsible for maternal recognition of the fetus in ruminants • IFN-τ inhibits HIV replication more strongly than human IFN-α • Efficiently inhibits early steps of the biological cycle of HIV, decreasing i/c HIV RNA & inhibiting initiation of the reverse transcription of viral RNA into proviral DNA • Ovine recombinant IFN-τ cross species barrier
  24. 24. IFN alpha IFN beta IFN gamma Monocytes, B – lymphocytes Fibroblasts & epithelial cells ActivaNK, CD4 TH1, CD8 B cellsted T-cells, Max. antiviral activity Intermediate antiviral activity More lyphokine activity than antiviral 13 genes 1 gene 1 gene Chr. 9 Chr. 9 Type 1 receptors Type 1 receptors Type 2 receptors Homology with IFN α-80- 95% 30-50% Less than 10%
  25. 25. Components of IFN system • IFNs • IFN genes • IFN receptors • Enzymes (JAK, STAT pathway) • cis-acting DNA elements (ISRE & GAS) • IRP (IFN regulated proteins)
  26. 26. IFN genes • Large no. of viral genes in humans • 13 IFN α genes, 1IFN β, 1 IFN ω – short arm of chr. 9 • single IFN γ gene - long arm of chr.12
  27. 27. IFN receptors • Act through cell surface receptors-species specific • Present on all cells except erythrocytes • α, β, ω - common receptor-consisting of 2 subunits, IFNAR-1 & IFNAR-2 • γ – receptor used by α,γ – consists of 2 subunits, IFNGR-1 & IFNGR-2 • IFN α, β receptor null mice – unable to survive in viral state
  28. 28. JAKs, STATs • STATs = signal transducer and activator of transcription • 7 STAT proteins – stat 14, 5a, 5b & 6 • JAKs =Janus family of tyrosine kinase (JAK) enzymes • 4 JAKs – jak 1-3 & Tyk-2
  29. 29. Mechanism Of Action
  30. 30. Virus infected cell IFN IFN attaches with receptor on neighbor cell Inactive RNAase L 2-5A synthesase + dsDNA Activate RNAase L Preotein kinases + ds DNA Phosphorilates elF-2 Degrades DNA Inhibits protein synthesis
  31. 31. General action of cytokines
  32. 32. General action of IFNs
  33. 33. Interferon Mediated Signaling
  34. 34. Jak-Stat pathway
  35. 35. Activation of receptor assoc. jaks
  36. 36. leads to the phosphorylation and dimerization of the Stat- 1 (p91) and Stat-2 (p113) proteins
  37. 37. •Subsequent translocation, along with IRF-9 (p48) to nucleus. •The complex of these three proteins, k/a IFN-stimulated gene factor 3 (ISGF-3)
  38. 38. Activates the transcription of IFN-α/β inducible genes through the ISRE (IFN stimulated response element)
  39. 39. The Jak-1 and Jak-2 kinases are activated by IFN -γ
  40. 40. phosphorylation and homodimerization of the Stat-1 protein and subsequent translocation to the nucleus
  41. 41. activates the transcription of IFN- γ- inducible genes
  42. 42. General Action Of IFNs
  43. 43. Interferon-induced Proteins • Protein Kinase (PKR) • 2,5-oligoadenylate synthetase (OAS) & RNase L • RNA-specific adenosine deaminase (ADAR), • Mx protein GTPases
  44. 44. •Phosphorylation of protein synthesis initiation factor (eIF-2)
  45. 45. •Minimal basal expression • Increase 10-1000 fold in response to IFN • In the presence of ds RNA - synthesize 2’-5’-linked oligoadenylates
  46. 46. Deamination of adenosine to inosine- edits ds-RNA
  47. 47. Family of Mx protein GTPases- targets viral nucleocapsids
  48. 48. Induaction of nitric oxide synthesae – increased intracellular conc. Of nitric oxide – inhibition of viral replication
  49. 49. •Upregulation of MHC class I & class II antigens expression •Enhance activation & effector function of cytotoxic T cells capable of destroying virus infected cells
  50. 50. Negative Regulators & Antagonists
  51. 51. Cellular Negative Regulators Of IFN Signaling • The family of suppressors of cytokine signaling (SOCS) - binds to JAKs - inhibits signaling - inhibits the tyrosine phosphorylation & nuclear translocation of Stat-1 • STAT-induced STAT inhibitors (SSI)
  52. 52. • Cytokine inducible SH2 protein (CIS) • Protein inhibitors of activated Stat (PIAS) PIAS 1 & PIAS 3 - directly associate with Stat-1 & Stat-3, - block the DNA-binding activity - Stat-1-mediated gene activation
  53. 53. Viral Antagonists of IFN Signaling • viruses encode proteins – impair activity of JAK-STAT signaling pathway • Molecular mimicry - viruses encode products- mimic cellular components of the IFN signal pathway- antagonist- impairs development of antiviral state
  54. 54. • Poxviruses- encode soluble IFN receptor homologues (vIFN-Rc)- secreted from poxvirus-infected cells- bind IFNs- prevent them from acting through their natural receptors • Adenovirus- E1A protein-inhibits DNA binding activity of ISGF-3
  55. 55. Applications • For human use they are produced by buffy coat leucocyes from blood banks NDV and Sendai virus as inducers • Many of these are in clinical use and are given intramuscularly or subcutaneously
  56. 56. Uses • IFN alpha • Condyloma acuminata • Ch HBV & HCV infections • Prophylax. & treatment in immunosupressed patients exposed to VZV , HSV 1&2 • Prophylaxis in CMV infect (renal transplant pts) AIDS associated kaposi’ sracoma • Hairy cell leukaemia • IFN gamma • Immunostimulant in onco. And immunoedeficients
  57. 57. Antiviral • Chronic HCV • HBV • In combination with ribavirin in HIV • HPV • HHV8 • CMV • Human Rhinovirus • Herpes virus
  58. 58. Antitumor • Cell differentiation & growth regulatory properties • Metastatic melanoma • Hematological cancers • Solid cancers • Hairy cell leukemia • Renal cell ca • Life threatening hemangiomas • Chronic myelogenous leukemia • Follicular non-hodgkin’s lymphoma
  59. 59. Multiple Sclerosis (MS) • Relentlessly progressive neurodegenerative disease - remissions and relapses - associated with demyelinationof nerves • Based on the immunomodulatory properties of the interferons • i/m IFN-β- reduction in the annual rate of relapses of MS • Addition of natalizumab, a recombinant monoclonal antibody augments the ability of IFN- β
  60. 60. Recombinant forms of α IFN • Alpha-2a drug name Roferon • Alpha-2b drug name Intron A • Alpha-n1 drug name Wellferon • Alpha-n3 drug name AlferonN • Alpha-con1 drug name Infergen
  61. 61. Recombinant forms of β IFN • Beta-1a drug name Avonex • Beta-1b drug name Betaseron Recombinant forms of γ IFN • Gamma-1b drug name Acimmune
  62. 62. Pegylation • Attaching a molecule of polyethylene glycol • PEG-inert, long chain amphiphilic molecules • Linear or branched structure • Increase size of IFN - prolonged absorption and ½ life & decreased clearance • retention of biological activity, stable compound & enhance water solubility
  63. 63. α IFN-2a (Roferon A) • 165 amino acids long protein chain • Recombinant DNA technology • Non-glycosylated protein • Short ½ life, large volume of distribution, larger renal clearance. • These problems were resolved by pegylating alpha- 2a resulting in peginterferon alpha-2a that is named Pegasys.
  64. 64. Adverse Effects • Flu-like symptoms: increased body temperature, feeling ill, fatigue, headache, muscle pain, convulsion, dizziness, hair thinning, and depression • Erythema, pain and hardness on the spot of injection • Immunosuppression , in particular though neutropenia • High level toxicity (Kidney, liver, bone marrow and heart) • All known adverse effects usually reversible • Disappear a few days after the therapy
  65. 65. References • Antiviral Actions of Interferons,Charles E. Samuel. Clin Microb Rev, Oct. 2001, p. 778–809 • Clinical uses of interferons, Robert M. Friedman, British Journal of Clinical Pharmacology • Antitumor Effects of Interferon-v: In Vivo Therapy of Human Tumor Xenografts • in Nude Mice, Holly M. Horton,1 Pepe Hernandez, Suezanne E. Parker, and Kerry M. Barnhart, [CANCER RESEARCH 59, 4064–4068, August 15, 1999] • Anti-Human Immunodeficiency Virus Activity of Tau Interferon in Human Macrophages: Involvement of Cellular Factors and β-Chemokines Christine Rogez, et al. J Virol. 2003 December; 77(23): 12914–12920

×