Oral Immunology - 0607 - L21 24 - Immune Modulation and Vaccines AND Dental caries

  1. Tissue typing: HLA Matching
    • - ABO
    • - HLA-A, HLA-B, HLA-DR (most important for grafting and transplantation)
    • - Preformed Abs- previous pregnancies, transfusions, transplantations
    • - Donor Ab screening: Sera of potential donors (donor Abs) mixed with lymphocytes of recipient + C’. Lysis is mismatch
    • - Cross-matching: Sera of recipient (recipient Abs) mixed with donor’s lymphocytes + C’. Lysis is mismatch
    • - Flow Cytometry
    • - PCR
  2. Evasion and subversion of the immune system by pathogens
    • - Genetic variation within pathogens prevents effective long-term immunity; Mutation and recombination allow influenza virus to escape from immunity
    • - Certain pathogens sabotage or subvert immune defense mechanisms
    • - Bacterial superantigens stimulate a massive but ineffective T-cell response
  3. Host defense against Streptococcus pneumoniae is type specific
    • - When exposed to S.p. for the first time, Ab are made and bacteria are cleared
    • - Over time, there is a different type of S.p.
    • - Old response no more effective; new response needed
  4. Two types of variation allow repeated infection with type A influenza virus
    • Antigenic drift - mutations alter epitopes in hemagglutinin, old Abs no more work
    • Antigenic shift - RNA segments are exchanged between viral strains in a secondary host, new hemagglutinin expressed, works if no cross-protective immunity.
  5. Antigenic variation in trypanosomes allows them to escape immune surveillance
    • Many inactive VSG genes (antigenic) but only one site for expression
    • Gene conversion - inactive genes copied into the expression site
    • Rounds of gene conversion allows the trypanosome to vary expressed VSG
  6. Bears have only one V gene. they generate diversity through gene conversion by moving dormant genes to the variable region.
  7. Persistence and reactivation of herpes simplex virus infection - cold sores
    • Primary infection - low expression of MHC I
    • Latent phase - trigeminal ganglion; low MHC I; evasion from CD8 T cells
    • Recurrent infection back at the initial infection site
  8. Some pathogens resist destruction or exploit the host for their good
    • Mycobacterium tuberculosis is taken up by macrophages but prevents the fusion of the phagosome with the lysosome.
    • Listeria monocytogenes, escape from the phagosome into the cytoplasm of the macrophage, where they multiply.
    • Toxoplasma gondii (a protozoan parasite ) generates its own vesicle, unavailable to MHC loading
    • Treponema pallidum (spirochete; syphilis) avoids elimination by coating its surface with host proteins until it has invaded tissues like CNS
    • Some strains of Borelia burghdorferi (Lyme disease) may coat themselves with complement inhibitory protein H.
  9. Immunosuppression or inappropriate immune responses can contribute to persistent disease
    • Staph. enterotoxins and TSST-1 - toxic shock; superantigen, stimulated T cells undergo massive responses and apoptosis, resulting in generalized immunosuppression
    • Bacillus anthracis - anthrax lethal toxin (lethal factor and protective antigen). Protective antigen routes lethal toxin to cytosol. MAP kinase inhibition leading to apoptosis of infected macrophages and premature DC maturation.
    • The measles virus can cause a relatively long-lasting immunosuppression in malnourished or undernourished children. Infected DC render T and B cells hyporesponsive to Ag.
  10. Immunodefiency Diseases
    • Occur when immune system components defective
    • Primary immunodeficiencies
    • - Caused by mutations in genes involved in immune responses
    • - Highly variable clinical manifestations: Recurrent and often overwhelming infections in very young children; allergy, abnormal proliferation of lymphocytes, and autoimmunity may occur
    • Secondary immunodeficiencies
    • - consequence of other diseases, or secondary to environmental factors such as starvation, or medical intervention.
  11. Inherited immunodeficiency diseases
    • caused by recessive gene defects
    • Mostly on X-chromosome
    • - Females can shut defective X chromosome with defective gene (do better; X-inactivation)
    • Defects in either the adaptive or the innate immune system
    • Rare
    • - Selective deficiency in IgA is the most frequently
    • reported - respiratory infections
  12. Mechanisms used by viruses of the herpes and pox families to subvert the host immune system
    • Inhibition of humoral immunity - virally encoded receptor/protein to block Ab/complement functions
    • Inhibition of inflammatory response - blocking chemokines and cytokines; EBV causes deficiency of adhesion molecules, e.g. ICAM-1, LFA-3; mimic TLRs to block pathways to NFkb
    • Blocking Ag processing and presentation - inhibition of MHC I; inhibition of TAP for peptide transportation
    • Immunosuppression - EBV mimics IL-10 to inhibit TH1 and reduce IFN-gamma
  13. Bruton's X-linked agammaglobulinemia (XLA)
    • - The first description of an immunodeficiency disease (male child)
    • - Defect in tyrosine kinase called Btk (Bruton's tyrosine kinase) -> defect in Ab production
  14. IgG levels in newborn infants fall to low levels at about 6 months of age
    • High before birth, passively transferred maternal IgG.
    • Drops shortly before birth and own IgG starts to rise at birth at a very slow rate -> lowest level reached at 6 mo pp
  15. X-linked Hyper IgM syndrome
    • - Commonest of hyper IgM syndromes
    • - Defect CD40L -> no adequate costimulation, defective class switching
  16. Common variable immunodeficiency (CVID)
    • - Usually a deficiency in IgM, IgG, and IgA together
    • - Decreased serum Ig and abnormal Ab responses
    • - Develops recurrent infections
  17. Severe congenital neutropenias
    • - Persistently low neutrophil counts (<200 per ul; normally 3-5.5k/ul)
    • - bone marrow transplant needed
  18. Defects in complement components are associated with susceptibility to certain infections and the accumulation of immune complexes
    • MAC (C5-9) Deficiency -> Neisseria infection
    • C3 deficiency -> infection w/ pyogenic bacteria and Neisseria, sometimes immune-complex disease
    • Classical pathway (C1,2,4) deficiency -> immune-complex disease
    • MBL pathway (MBL, MASP1,2, C2,4) deficiency -> childhood infections
    • Alternative pathway (Factors D, P) deficiency -> infection w/ pyogenic bacteria and Neisseria, NO immune-complex disease
  19. Defects in phagocytic cells: persistence of bacterial infections
    • TLR signalling defects (e.g., MyD88 or IRAK4) -> severe cold pyogenic bacterial infections
    • G6PD deficiency -> defective respiratory burst, chronic infection
    • Myeloperoxidase deficiency -> defective intracellular killing, chronic infection
  20. Severe combined immunodeficiency (SCID)
    • Commonest is XSCID
    • Mutation in the gene for IL-2R common gamma chain (γc) shared by:
    • - IL-2, 4, 7, 9, 15, and 21
    • - T cells and NK cells fail to develop normally
    • - B cell numbers normal, but non-functional
  21. Grafting of bone marrow can be used to correct immunodeficiencies caused by defects in lymphocyte maturation, but two problems can arise
    • GvHD, systemic immune disease
    • Host-vs-Graft response -> graft failure
  22. Acquired immune deficiency syndrome (AIDS)
    • - The most extreme immune suppression caused by a pathogen - the human immunodeficiency virus (HIV)
    • - opportunistic pathogens infection, aggressive form of Kaposi's sarcoma or B-cell lymphoma, profound decrease in CD4 T cells number
    • - Two types of HIV: HIV-1 (chimpanzee, common in western countries, more aggressive) and HIV-2 (monkey)
    • - Groups of HIV-1: M (main), O (outlier), and N (non-M, non-O)
    • - M group is classified (according to genetic diversification) into subtypes, or clades, A to K
    • - Virus is mainly carried by cells w/ CD4, which acts as the receptor for the virus, along with a co-receptor, usually the chemokine receptors CCR5 or CXCR4; Dendritic cells and macrophages are also infected; or as a free virus in blood, semen, vaginal fluid, or mother's milk.
  23. Typical course of untreated infection with HIV
    • Flu-like (majority) in the first 2-6wk after infection, CD4 T rises slightly then drops quickly w/ some rebound.
    • Secoconversion happens, CD4+ PBL, aymptomatic for years, CD4 drops below 500/ul
    • Symptomatic, CD4 keeps dropping to 200/ul
    • AIDS starts and CD4 keeps dropping to zero, death.
  24. Virion of HIV
    • within nucleocapsid: dsRNA, reverse transcriptase, integrase (integrate viral DNA into host genome, stays forever)
    • envelope proteins: gp120 and gp40 bind to CD4, use CCR5 or CXCR4 as coreceptor; MHC proteins capture something and put it on to hide from the immune system .
  25. Dendritic cells initiate infection by transporting HIV from mucosal surfaces to lymphoid tissue
    DC-SIGN used to bind the virus
  26. HIV Therapy
    • - Zidovudine (AZT)- nucleoside analogs that inhibits reverse transcriptase
    • - Highly active antiretroviral therapy (HAART) - combination therapy with a cocktail of viral protease inhibitors and nucleoside analogs; has lead to great increases in survival
    • - Vaccines are attractive but difficult
  27. Vaccination
    • Active immunization: Deliberate induction of adaptive immunity to a pathogen by injecting a dead or attenuated (nonpathogenic) form of the pathogen (vaccine).
    • “Passive immunization”: Immunity is transferred by administration of an immune serum or Ig
  28. Adjuvants:
    • Are compounds that enhance the immune response when administered with antigen, thereby producing higher antibody titers and prolonged production.
    • The distinction between primary and secondary immune responses become blurred when adjuvants are used.
  29. Adjuvants that enhance immune responses
    • Only two adjuvants - alum and MF59 - are licensed for use in vaccines given to humans
    • - Incomplete Freund’s: oil in water emulsion, antigen diffuses slowly, constantly stimulating immune response
    • - Complete Freund’s: also oil in water
    • - Freund’s adjuvant with MDP: mimics the same result
    • - Alum (aluminum hydroxide gel)
    • - Alum plus killed B.p.
    • - ISCOMs (immune stimulartory complexes) are made from a protein Quil A (comes from bamboo in South America) that contains viral proteins to deliver stimulation to T cells
  30. Approaches to vaccine develpment
    • Live attenuated or killed bacteria- Innate & Adaptive (e.g. BCG, Cholera)
    • Live attenuated viruses – E.g. Polio, rabies
    • Subunit (Ag) vaccines – inactivated toxin (“toxoid”). E.g. Tetanus toxoid, diphtheria toxoid. Polysaccharide vaccines have protein conjugate for
    • induction of B and T cell responses
    • Conjugate vaccines- E.g. Haemophilus influenzae, pneumococcus
    • Synthetic vaccines- Recombinant DNA. E.g. Hepatitis (recombinant proteins)
    • Viral vectors- Clinical trials of HIV antigens in canarypox vector
    • DNA vaccines- Plasmid of cDNA, CpG DNA (TLR9 agonist)- Clinical trials ongoing for several infections
  31. Vaccination with cowpox virus elicits neutralizing Abs that react with antigenic determinants shared with ________.
    smallpox virus
  32. Attenuated viruses are selected by growing human viruses in non-human cells
    • 1. Isolate pathogenic virus from patient
    • 2. grown in human cell culture
    • 3. cultured virus infect monkey cells
    • 4. to grow well, acquire many mutations; no longer grows well in human cells (attenuated)
    • 5. used as vaccine
  33. Production of live attenuated viral strains by recombinant DNA techniques
    • 1. isolate virus
    • 2. isolate genes for receptor-binding proteins, virrulence, core proteins
    • 3. mutate/delete virulence gene
    • 4. resulting virus is viable, immunogenic, but avirulent, used eaas vaccine
  34. Influenza virus vaccination complication
    • Reye's syndrome - an acute pathological condition affecting the central nervous system.
    • Principally associated with children who have taken aspirin
    • no known direct cause-and-effect relationship between aspirin use and Reye's syndrome
  35. Diseases w/o effective vaccine
    • malaria, tuberculosis, ...
    • Measles - IgM based, heatsensitive, difficult to use in tropical countries w/o refrigeration
  36. 2010 Milestone in Cancer Vaccine
    • Provenge: Advanced hormone resistant prostrate cancer vaccine. April 30, 2010: FDA Approval to Dendreon
    • DC from patient activated with PAP (Prostatic Acid Phosphatase), GM-CSF (granulocyte monocyte colony stimulating factor) fusion protein
    • Vaccination of patient
    • - 3 year survival increased by 38%
  37. The three most important elements in relation to caries
    • host and teeth
    • microflora
    • substrate (diet)
    • also important, time, saliva
  38. Association of S. mutans with Caries - clinical data (mid 70’s)
    • • Strains isolated proved cariogenic in animals
    • • Relationship of S. mutans to Carious Lesions
    • – a. Lesion First
    • - S. mutans found in plaque over incipient lesions involving pits and fissures of smooth surfaces.
    • - 71% had > than 10% S. mutans.
    • - 70% no caries little or no S. mutans
  39. Bacteria Produce Acid
    • During acid attack, plaque fluid pH is lowered.
    • pH drop changes the ecological environment close to tooth
    • Aciduric - endures acid, favors overgrowth of S. mutans
    • Acidogenic - S. mutans produces acid
  40. Saliva Neutralizes Acid
    • Stephan Curve: pH drops after rinsing with sucrose more in caries active vs. caries inactive areas.
    • Critical pH is 5.5, causes plaque to demineralize the enamel
  41. ___________ results in cavitation.
    Subsurface demineralization
  42. Parotid duct is located next to the _______.
    • upper first molar
    • there will be IgA and other salivary components, but no serum factors including IgG
  43. Sublingual duct pours saliva on the ____ surface.
    lingual
  44. Gingival crevice fluid
    • Fluid exists into saliva from crevice containing:
    • – Serum elements
    • – PMNs
    • Crevice contains both
    • – Innate factors: Lysozyme, lactoferrin, lactoperoxidase
    • – Acquired factors: IgG, IgA
  45. Caries Process
    • Bacterial adherence and production of acid from carbohydrates.
    • Demineralize enamel
    • Saliva can buffer acid and provide many sources of proteins that can effect the outcome
    • Microbial habitat or niche is important
    • Bacteria can accumulate on a variety of enamel surfaces:
    • – Buccal
    • – Lingual
    • – Proximal
    • – Occlusal, most important, w/ pits and fissures
    • Surfaces are different
    • Smooth surfaces require bacteria to attach via adhesins and glucans
    • Proximal surfaces are exposed to both saliva and crevice fluid
    • Occlusal caries - bacteria are impacted into deep crevices where Saliva can't reach
  46. Highest concentration of IgG would be found _________, and the highest concentration of IgA is found __________. There is a huge difference in pits and fissures in adult and child teeth - Difficult to penetrate saliva into this.
    • in proximal areas of teeth
    • on smooth areas of teeth
  47. Difficulty of bristle penetrating the fissure
  48. Saliva can interfere with caries by many mechanisms:
    • – Buffering with bicarbonate
    • – Dilution by flow
    • – Healing by calcium deposition
    • – Lubricating soft tissues
    • – Antibacterial mechanisms: both innate and acquired immune capabilities
  49. LAP and Proximal Decay
    • Children with LAP have minimal proximal decay.
    • Children with LAP have saliva that kills S. mutans, not due to difference in pH
    • An active antimicrobial factor found in LAP saliva is Lactoferrin (Lf)
    • Lf in LAP patients has a SNP (Single nucleotide polymorphism) in amino acid position 29 (or 47) that codes for lysine (K); Control group had arginine (R) at 29.
    • Lf with lysine killed SM (also S. mitis, S. sanguis), whereas arginine one didn’t
  50. Move from crevice to saliva thru vasculature and junctional epithelium
    • Primary (azurophilic):
    • Secondary (specific): Toxic oxygen, Lactoferrin, Lysozyme
  51. Lf Causes membrane to leak proteins and causes them to die?
  52. First line of Defense
    • Influence of Co-Inhabiting Bacteria
    • Acid produced by S. mutans = Lactic acid
    • Cohabitated by Veillonella, also early plaque former
  53. S. mutans FIL Produces
    lactic acid, w/ lactic acid dehydrogenase (LDH)
  54. S. mutans C67 Produces
    acetic acid
  55. Veillonella alcalescens Ferments _______ to Produce __________
    • lactic acid
    • acetic acid
  56. S. mutans FIL cohabitates w/ Veillonella alcalescens, S. mutans C67 does not. W/ cohabitation, ____ caries happened.
    • less
    • acid was not available to cause demineralization of teeth in rats with Veillonella
  57. Replacement therapy
    impractical to eradicate oral flora from the mouth before inoculating the replacement
  58. Vaccination -> Ag?
    • Serotype carbohydrate
    • Antigen I/II
    • GTF
    • GBP
  59. Feasibility: Vaccination
    • 1. Transmission
    • 2. Secretory IgA system discovered
    • 3. A microbe amenable to vaccination
    • – Serotype
    • – Attachment factors; GBP; GTF
    • 4. Result of Immunization
    • – Agglutination
    • – Killing enhanced
  60. Vaccine Possibilities
    • Ways to Vaccinate:
    • – Swallowing
    • – Intra gastric – GALT
    • – Intra nasal – NALT
    • – Intra ductal – salivary gland
    • – IM and IV
    • Salivary (IgA) from oral; or Serum (IgG) Response (from IV injection)
  61. Vaccine Possibilities
    • Active or Passive Immunization:
    • – Active: Stimulate Lymphocytic response
    • – Passive: Apply already synthesized Ab to prevent colonization: In egg yolk; In milk; Apply to teeth
    • Goal: Reduce number of microbes
  62. Immunological Intervention
    • Inject S. mutans into monkeys --->serum IgG response ---> reduced caries
    • Inject S. mutans into rat salivary glands --> Secretory IgA response ---> reduced caries
    • Feed S. mutans to rats in capsule develop a mucosal immune response
    • –> salivary IgA without detectable IgG ---> less caries.
    • –> Produced secretory IgA in tears
    • These experiments led to the concept that there was a common mucosal immune system, Monitoring response in serum, saliva and tears
  63. Immunological Intervention
    • S.mutans challenge: Gut Associated Lymphoid
    • Tissue (GALT)
    • S.mutans challenge: Nasopharyngeal Associated Lymphoid Tissue (NALT)
    • - Antigen delivery by oral (swallowing) or nasal routes results in the migration of antigen-specific IgA-producing B-cells to effector organs (salivary
    • glands).
    • – Then get differentiation and maturation of these B cells and secretion of IgA in the lamina propria, where it crosses the ducts into the saliva
  64. Took Salmonella typhii, knocked out toxins, cloned in S. mutans I/II antigens and gave to rats; produced mucosally immunized rats to S. mutans I/II via IgA
  65. Passive Immunization
    • Topical application of monoclonal antibody to I/II antigen has been effective.
    • Studies of application of mouse monoclonal IgG specific antibodies for antigen I/II showed that recolonization of S. mutans was postponed for 2 years after a 9-day treatment with Chlorhexidine prior to admin of antibody.
  66. Passive Immunization
    • Julian Ma T. Lehner Nat Med 1998
    • Production of salivary IgA in a tobacco plant
    • Constructs encoding four proteins
    • – Heavy chain mouse gamma1 and alpha domains, K light chain and J chain also in mouse, secretory component from rabbit.
    • – Purified from tobacco plant by ammonium sulfate precipitation and protein G affinity column --> 10-80 mg/kg of plant.
    • Protocol
    • – Application to humans who had S. mutans on their teeth
    • – 9 days of application of CX
    • – Apply antibody or control to their teeth, two applications per week for three weeks.
    • Recolonization of S. mutans took 58 days in controls
    • No colonization by 118 days in either monoclonal IgG or in plant derived IgA topically applied
  67. Conclusions Caries Research and Practice:
    • 1. Early Evidence: (1900-1950);
    • Animal experiments implicate an coccal microbe
    • 2. Seminal Experiments (1960’s)
    • a. Followed Koch’s postulates
    • b. Strep was isolated and transferred from caries resistant to caries susceptible hamsters.
    • 3. Clear assoc. between carious lesion and S. mutans (1970’s)
    • 4. Genetic attributes of S. mutans identified (1980’s -present)
    • 5. Importance of sucrose as a substrate shown (1980’s - present)
    • 6. Diagnostic and Preventive Strategies Developed (1990’s)
Author
akhan
ID
321385
Card Set
Oral Immunology - 0607 - L21 24 - Immune Modulation and Vaccines AND Dental caries
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Oral Immunology - 0607 - L21 24 - Immune Modulation and Vaccines AND Dental caries
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