Immunoterapia. Prof Ennio Carbone Corso Medicina e Chirurgia 2013

Transcription

1 Immunoterapia Prof Ennio Carbone Corso Medicina e Chirurgia 2013

2 Lecture Structure Open Discussion on Tumor Immunology concept The cancer is an inflammatory disease The immunotherapy: Past Present Future

3 Cancer is an Inflammatory Disease

4 EFFECTOR FUNCTIONS:CYTOKINES

5 Main Immunity mechanism involved in cancer disease

6 Immunomodulation & Malignancy Active immunotherapy elicits response in host Passive immunotherapy administration of externally stimulated immunologic components Problems Tumor antigens difficult to identify Tumor cells capable of altering antigen expression Tumors produce immunosuppressive factors

7 THE PAST

8 Immunomodulation &Malignancy Active Immunotherapy: IL-2 + cationic liposome Passive Immunotherapy: IL-2 + NK cells, IL-2 + Tumor Infiltrating Lymphocytes (TILs)

9 COME GENERARE CLONI CD4+ANTI MAGE van der Bruggen, Pierre, Zhang, Yi, Chaux, Pascal, Stroobant, Vincent, Panichelli, Christophe, Schultz, Erwin S., Chapiro, Jacques, Van den Eynde, Benoît J., Brasseur, Francis & Boon, Thierry Tumor-specific shared antigenic peptides recognized by human T cells. Immunological Reviews 188 (1),

10 COME GENERARE CLONI CD8+ ANTI MAGE van der Bruggen, Pierre, Zhang, Yi, Chaux, Pascal, Stroobant, Vincent, Panichelli, Christophe, Schultz, Erwin S., Chapiro, Jacques, Van den Eynde, Benoît J., Brasseur, Francis & Boon, Thierry Tumor-specific shared antigenic peptides recognized by human T cells. Immunological Reviews 188 (1),

11 Induction of tumor necrosis and regression Inhibition of tumor vascularization Inhibition of tumor cell proliferation TNF-alpha Melanoma K Melanoma + TNF

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13 The experimental system ACT CD8 GP100 pontaneously A develop a cutaneous melanomas the Cdk4 R24C mutation in their and survive well into their second gns of illness. C57BL 6 mice carrye show a dark skin phenotype elanocytes also reside in the basal is and are not confined to the derlicles. This distribution of melanouman skincand is not Aobserved in ma models (Noonan et al., 2001). evelop multiple, small pigmented starting at an age of 6 8 months. ese lesions do not become larger e defined them as mouse nevi. In few melanocytic tumors start to A New BL6 mouse model transgenic for Immune surveillance and immune evasion of melanoma HGF with CDK-4 mutation recapitulate grow progressively, indicating transformation Immune surveillance into a primary cutaneous melanoma. C57BL 6 Hgf-Cdk4 and immune evasion of melanoma B B A human R24C mice show a similar phenotype, but nevi and melano- melanoma disease. mas appear with significantly decreased latency and increased penetrance (Figure 1A). At the age of 1 yr, the incidence of progressively growing nodular melanomas was 7% in C57BL 6 Hgf mice (n = 14) and 62% in C57BL 6 Hgf-Cdk4 R24C mice (n = 61). Although both genetic alterations are present in all cells, they selectively promote malignantimmune conversion surveillance of melanocytes and immune evasion of melanoma because only very few mice develop tumors of other histology at the time of melanoma-related death. C Spontaneous nodular melanomas are not randomly distributed in the skin of Hgf-Cdk4 R24C mice and vary in number and tumor growth kinetics. Tumors appear mostly on the back and more rarely in other localizations such as the ear, nose, belly, extremities, anus and tail (Figure 1B). Fast-growing tumors (tumor volume Immune surveillance and immune evasion of melanoma A B B Figure 3. Macroscopic and microscopic appearance of melanoma metastases. (A) From left to right: Representative pictures of a draining lymph node, the lungs and the liver of an Hgf-Cdk4 R24C mouse bearing a large primary melanoma in the skin. (B) Corresponding H&E stains at a magnification of 25 (top) and 400 (bottom). (C) Left: Macroscopically visible lymph node, lung and liver metastases in a cohort of 39 Hgf-Cdk4 R24C mice (left). Right: Lung metastases in mice with rapidly growing nodular (n = 15), slowly growing nodular (n = 12), and slowly growing flat melanomas (n = 12). B Figure 5. Analysis of tumor and immune cells infiltrating the draining lymph nodes. (A) Representative immunofluorescence picture showing melanoma cells stained for Trp1 in green, immune C immune cell recruitment (Figure 4A, middle). Flow cytometric analyses of single cell suspensions derived from primary tumors confirmed that 60% of primary Hgf- Cdk4 R24C melanomas contain less than 3% CD45 + immune cells. The remaining 40% of primary tumors contained between 6 and 15% CD45 + immune cells, which predominantly D showed a Gr1 + CD11b + myeloid phenotype (Figure 4B). A correlation with the macro- Next we characterized the tumor microenvironment of primary Hgf-Cdk4 R24C melanomas on a molecular level using quantitative RT-PCR. Primary melanomas strongly expressed the melanosomal enzymes gp100 (Si ) and Trp2 (Dct) as well as the melanocyte-specific isoform 2 of the transcription factor Mitf when compared with nevi or healthy skin, confirming the presence of large numbers of pigmented melanoma cells (Figure 4C). An increased Landsberg Pigment Cell and Melanoma 2010

14 ACT adoptive cell therapy transfer Chemotherapy with ciclophosphamide Adoptive transfer specific CD8+ T cell (from TCR trasgene gp100) adjuvant CpG (poly riboinosinic: poly ribocitidinic acid) AFTER 2 MONTHS REMISSION TUMOR RECOVER

15 HGF CDK4(R24C) melanomas resisting ACT with gp100specific CTLs show partial loss of antigen expression in an inflammatory tumour microenvironment. J Landsberg et al. Nature 000, 1-5 (2012) doi: /nature11538

16 Loss of gp100 antigen expression in relapsed HGF CDK4(R24C) melanoma lines is reversible after re-transplantation. J Landsberg et al. Nature 000, 1-5 (2012) doi: /nature11538

17 a Relapse down-regulated genes (335) Relapse up-regulated genes (245) b -log10(p-value log10(p value) FDR BH adjusted adjusted) Relapse down-regulated genes Relapse up-regulated genes GO ID (BP) Description p-value* GO: pigmentation 1.7e-09 GO: melanin metabolic process 4.7e-07 GO: secondary metabolic process 5.4e-06 GO: carboxylic acid metabolic process 3.5e-04 GO: regulation of synaptic plasticity 8.3e-04 GO: immune system process 6.3e-16 GO: immune response 3.3e-15 GO: defense response 1.5e-12 GO: anatomical structure development 3.9e-09 GO: chemotaxis 8.5e log fold vs untreated) log2 fold change (Relapse vs. control) c Color Key d Color Key Value log2 fold change HCmel3 tumours Control Relapse Re-Tx Value log2 fold change HCmel3 tumours Control Relapse Re-Tx Relapse down-regulated genes Relapse up-regulated genes Pigmentation genes Trpm1 Rab17 Oca2 Kit Gpr143 Rab38 Mlana Rab27a Slc45a2 Mreg Ednrb Gpnmb Mcoln3 Pmel Hps5 Mlph Mitf Shroom2 Tyrp1 Sox10 Mc1r Tyr Myo5a Trappc6a Dct Supplementary Figure 4. Gene expression analysis reveals reversible down-regulation of pigmentation genes and up-regulation of immune response genes in relapsed HCmel3 melanomas in vivo. a, Vulcano scatter-plot visualizing the identification of differentially expressed genes (coloured dots) in untreated control (n=5) vs. relapsed HCmel3 melanomas (n=5). The significance of the respective genes is plotted versus the log2 fold change between the two experimental groups. The p-values were corrected for multiple testing by the Benjamini and Hochberg procedure (BH). Horizontal and vertical dashed lines indicate the cut-off thresholds for p-values (<0.01) and log2 fold changes (>2). A list of all differentially expressed genes is given in Supplementary Table 1. b, Over-represented gene ontology biological process subcategories (GO BP) in the respective

18 -log1 lo 0 1 genes GO: anatomical structure development 3.9e-09 GO: chemotaxis 8.5e log fold change (Relapse vs untreated) log2 fold change (Relapse vs. control) c Color Key d Color Key Value log2 fold change HCmel3 tumours Control Relapse Re-Tx Value log2 fold change HCmel3 tumours Control Relapse Re-Tx Relapse down-regulated genes Relapse up-regulated genes Pigmentation genes Trpm1 Rab17 Oca2 Kit Gpr143 Rab38 Mlana Rab27a Slc45a2 Mreg Ednrb Gpnmb Mcoln3 Pmel Hps5 Mlph Mitf Shroom2 Tyrp1 Sox10 Mc1r Tyr Myo5a Trappc6a Dct Supplementary Figure 4. Gene expression analysis reveals reversible down-regulation of pigmentation genes and up-regulation of immune response genes in relapsed HCmel3 melanomas in vivo. a, Vulcano scatter-plot visualizing the identification of differentially expressed genes (coloured dots) in untreated control (n=5) vs. relapsed HCmel3 melanomas (n=5). The significance of the respective genes is plotted versus the log2 fold change between the two experimental groups. The p-values were corrected for multiple testing by the Benjamini and Hochberg procedure (BH). Horizontal and vertical dashed lines indicate the cut-off thresholds for p-values (<0.01) and log2 fold changes (>2). A list of all

19 Proinflammatory mediators directly promote HGF CDK4(R24C) melanoma cell dedifferentiation leading to impaired recognition by gp100-specific CTLs. J Landsberg et al. Nature 000, 1-5 (2012) doi: /nature11538

20 a Ctrl 24h 48h 72h pmel-1 CTL conditioned medium 18% Count 24% Count 41% 56% Count Count BM-M! conditioned medium Count 32% Count 65% 78% Count Ngfr b Ctrl TC CM M! CM gp kda Ngfr 75 kda ß-Actin 42 kda Supplementary Figure 6. Exposure of HCmel3 melanoma cells to culture supernatants of activated T-cells or macrophages increases Ngfr expression and decreases gp100 expression. a, Flow cytometric analysis of Ngfr expression on the surface of HCmel3 cells cultured for 24h, 48h, and 72h in the presence of supernatants harvested from TCRtg pmel-1 CTL activated with their cognate gp100aa25-33 peptide antigen (top row) or from bone marrow-derived macrophages activated with LPS (bottom row). b, Immunoblot analyses for gp100 and Ngfr expression in lysates of HCmel3 cells cultured for 72h as indicated. NATURE 6

21 TNF alpha control the melanoma gene plasticity a b Color Key HCmel3 +Tnf- down-regulated genes (139) c HCmel3 +Tnf- up-regulated genes (243) GO ID (BP) Description p-value* GO: pigmentation 5.6e-07 GO: melanin biosynthetic process 1.4e-04 GO: secondary metabolic process 2.1e-03 GO: carboxylic acid metabolic process 9.5e-03 GO: immune system process 6.7e-12 GO: defense response 4.2e-11 GO: immune response 7.5e-11 GO: anatomical structure development 8.2e-11 GO: positive regulation of cell migration 1.4e-08 GO: regulation of apoptotic process 5.4e-08 d Value log2 fold change Pigmentation genes HCmel3 in vitro Control +Tnf- Trpm1 Rab17 Oca2 Kit Gpr143 Rab38 Mlana Rab27a Slc45a2 Mreg Ednrb Gpnmb Mcoln3 Pmel Hps5 Mlph Mitf Shroom2 Tyrp1 Sox10 Mc1r Tyr Myo5a Trappc6a Dct log2 fold change (HCmel3-R vs. control) r = 0.61 co-regulated co regulated 50% 50% only only TNF Tnf- 7% anti regulated inversely regulated 2% 2% only HCmel3 R only HCmel3-R 41% 41% log2 fold change (Tnf- vs. control) Supplementary Figure 8. Gene expression changes caused by short-term Tnf- treatment are largely recapitulated in HCmel3 relapse lines compared to parental HCmel3 melanoma cells. a, Over-represented gene ontology biological process subcategories (GO BP) in HCmel3 cells treated with Tnf- for 72 hours vs. untreated HCmel3 cells (see also Supplementary Tables 5 and 6). Differentially expressed genes were identified by applying an absolute log2 fold change cut-off >1.5. b, Gene expression heat map of 25 pigmentation genes showing global down-regulation in Tnf- treated HCmel3 cells in vitro.

22 TNF-α induces human melanoma cell dedifferentiation leading to selectively impaired recognition by autologous CTLs specific for melanocytic antigens. J Landsberg et al. Nature 000, 1-5 (2012) doi: /nature11538

23 Cytokines Therapy The cytokines used so far are: IFN-a/b/g, IL-1, IL-2, IL-4, IL-5 and IL-12, GM-CSF, TNF Few results obtained the network complexity hamper the approach efficiency It is difficult reach working concentration in the tumor site.

24 MAGIC BULLET

25 IMMUNOTERAPIA GENICA

26 SCINTIGRAFIA CON ANTICORPI MONOCLONALI

27 Perché abbiamo bisogno di terapie innovative contro il cancro?

28 Le chemioterapie disponibili non sono in grado di eliminare selettivamente le cellule tumorali I tumori sono in grado di selezionare geni (multidrug resistance genes, MDR) che eliminano efficientemente il farmaco.

29 The Present

30 Nature 2011.vol 480

31 Established immune treatments mabs based 9 mabs directed against 6 oncoproteins: Her2/neu (Solid tumors) EGFR (Solid tumors) VEGF (Solid tumors) CD20 (Hemathological malignancies) CD52 (Hemathological malignancies) CD33 (Hemathological malignancies)

32 FDA approved cytokines treatments IL2 (Proleukin) Melanoma Kidney Cancer INF alpha Melanoma Kidney Cancer Low response 15% patients Seriuos systemic inflammation

33 Generation and regulation of antitumour immunity

34 Enhancement of APC Activity Manipulation of co-stimulatory signal Monoclonal Antibodies Immunoterapia del cancro Vaccinazione Uso di citokine Infusione (Adoptive therapy) DNA DC VIRUS IL15, IL21

35 Manipulation of Co-stimulatory Signal Biotechnology assisted: gene cloning and transfection, large in vitro Tumor cell culture

36 Combining Co-stimulation and APC

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38 Strategie di generazione dei vaccini Genetico: librerie di DNA riconbinante sono trasfettati in cellule bersaglio esposte al riconoscimento dei CTL ottenuti dal paziente, il gene trasfettato in grado di attivare i linfociti viene isolato sequenziato ed espresso come peptide Biochimico: le molecole MHC vengono purificate dal tumore i peptidi eluiti e separti per HPLC, quindi vengono testati individualmente per la loro capacità di indurre attività citotossica da parte dei CTL

39 Antitumor vaccine Prophylactic (hepatitis B, HPV) Therapeutic

40 Efficacy differences between Prophylactic and Therapeutic vaccine Hepatitis B and HPV vaccine give a good protection since they specific viral antigens are known. Therapeutic vaccine have a reduced effcacy if any.

41 Therapeutic vaccine lack of antigen hamper their efficacy No specific Ag Patients treatment performed with: small peptides (pharmacokinetic fast removed), DC not stimulated with right adjuvant thus not not fully matured (anergy)

42 THE FUTURE

43 Next therapeutic vaccine GlaxoSmithKline is generation I currently conducting a large (.2,500 patients) randomized phase III trial using a recombinant fusion protein encoding a single cancertestis antigen (MAGE-A3) in HLA-A2-positive non-small cell lung cancer patients, together with their ASO2B adjuvant consisting of a saponin/lipid-aemulsion combined with TLR4 and TLR9 agonists. Initial read-outs from the phase II trial (180 patients) showed somesurvival response (27%), but this did not reach statistical significance. LIMITATIONS: no information on the MAGE3 expression in lung cancer

44 Next therapeutic vaccine generation II Virus based: NCI vaccinia virus recombinant coding for prostate specific Ag, B7.1, ICAM-1, LFA-3 plus GM-CSF Result prostate cancer patients survival 25 months survival instead 15 months

45 Problem: patient treatment with a single tumor specific Ag or a repertoire of several tumor associated Ags?

46 The GVAX exeperience The prostate cancer cells in toto engeneerized with GMCSF gene were administred to prostate cancer patients. FAILURE they did not cover the whole tumor associated Ags spectra

47 DC vaccine based intervention the Provenge exeperience Provange was a DC based vaccine for advanced prostate cancer patients composed by PBMC+cytokines and tumor derived differentiation Ags 1 out 341 treated patents respond however 2,6% patients have areduction of cancer prostate Ag Survival 25.8 months instaed of 21.7 months FDA granted the approval since these patients have no other therapy

48 Direct manipulation of T lymphocytes The CAR generation: Chymeric Antigen Receptors transduced T cells recognizing native tumor antigens (scfv antibodies)

49 The immunotherapy frontiers 2011 Ipilimumab Anti CTLA-4 mab

50 GRUPPO DI STUDIO I An- CTL- 4 Mabs break tumor tolerance The new england journal of medicine A No. at Risk Ipilimumab dacarbazine Placebo dacarbazine Patients Surviving (%) Placebo dacarbazine Ipilimumab dacarbazine Months Censored Censored B No. at Risk Ipilimumab dacarbazine Placebo dacarbazine Patients without Progression (%) Ipilimumab dacarbazine Placebo dacarbazine Months Censored Censored C Patients with Complete or Partial Response (%) No. at Risk Ipilimumab dacarbazine Placebo dacarbazine Ipilimumab dacarbazine Placebo dacarbazine Duration of Response (mo) Censored Censored 2522 n engl j med 364;26 nejm.org june 30, 2011 The New England Journal of Medicine Downloaded from nejm.org at KAROLINSKA INSTITUTE UNIVERSITY LIBRARY on November 5, For personal use only. No other uses without permission. Copyright 2011 Massachusetts Medical Society. All rights reserved. Robert C et al N. Engl.J. Med :2517

51 BIOLOGICAL EFFECT OF ANTICTLA-4 BLOCKADE

52 Next generation T cells immunomodulators

53 Melanoma V600E activating mutation of BRAF Inhibitor of BRAF gave 50% rsponse in patients. However resistance appears in 1 year Association between ipilimumab and vemurafinib (BRAF inhibitor)

54 IL-2 and IL-15 in Cancer therapy

55 The IL-15 relevancy in Immune activation

56 Next Antibody generation to fight cancer

57 ANTI LEUKEMIC ANTI LYMPHOMA anti IL2R alpha mabs antibodies specific for IL-2Rα: basiliximab (Simulect; Novartis AG), a chimeric antibody approved by the US Food and Drug Administration (FDA); daclizumab (also known as anti-tac; Zenapax; F.Hoffman-LaRoche Ltd), is the first humanized antibody, which has also been approved by the FDA45 4 All this antibodies are blocking the proliferation of lymphoma and leukemia cells

58 18 anticorpi sono approvati dalla FDA, 1 è stato tolto dal commercio (17 disponibili per la pratica clinica) 14 sono Ab non modificati IgG, 2 radioconiugati, 1 coniugato con tossina, 1 Fab 150 sono in fase di sviluppo clinico

59 Key step to mab tumor targeting

60 * * * * * * * *

61 HOW GENERATE NEW mab for THERAPY

62 Stuff required for mab therapy Hybridomas (mouse) Chimerization and humanization Genetically Different display library structure based design

63 Carter Nature Reviews Immunology 6, (May 2006) doi: /nri1837

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65 Antibodies manipulations

66 Anticorpi ottimizzati per scopi terapeutici

67 ACT Adoptive Cell Transfer Therapy

68 Current clinical protocols for adoptive cell therapy

69 Tumor infiltrating lymphocytes

70 HOW OPTIMIZE THE CTL ANTI TUMOR COMPLIANCE

71 The adoptive therapy with TILs 2006 Nature Review Immunology Adoptive Immunotherapy for Cancer Gattinoni et al

72 Cancer Regression in Patients After Transfer of Genetically Engineered Lymphocytes Richard A. Morgan, et al 6 OCTOBER 2006 VOL 314 SCIENCE

73 WHY PATIENT LYMPHODEPLETION?

74 THE IMMUNODEPLETION EFFECTS

75 Sinergisticantitumor effect of immunotherapy and viral therapy

76 Survival outcome of combined immunotherapy and virus treated tumor bearing mice

77 NK CELLS COULD BE USED IN TUMOR THERAPY?

78 Antibodies modulating NK cells functions in neoplastic patients UARK , A Study of Expanded Natural Killer Cell Therapy for Multiple Myeloma (NK )

79 Antibody to manipulate NK cell Cancer targeting I

80 ACT with NK cells

81 Future Global and Combined approaches using NK cells

82 Letteratura della lezione Nat Med September ; 10(9): Cancer immunotherapy: moving beyond current vaccines Steven A Rosenberg, James C Yang, and Nicholas P Restifo Adoptive immunotherapy for cancer: building on success Luca Gattinoni, Daniel J. Powell Jr., Steven A. Rosenberg and Nicholas P. Restifo Nature Rev Immunology 2006:383 Nature Reviews Immunology 6, (August 2006) The biology of interleukin-2 and interleukin-15: implications for cancer therapy and vaccine design Thomas A. Waldmann Ljunggren and Malmberg Prospect to use NK cells in human cancer therapy Nature Immun :329

83 GRUPPO DI STUDIO DI IMMUNOBIOINGEGNERIA

84 Nanotechnology and Vaccine AIDS May be Cured by Nanotechnology With Nanoemulsion Nasal Vaccine Producing Immunity to HIV, Smallpox and Other Infectious Diseases

85 ANTIVIRAL CHEMOTHERAPY Viruses are obligate intracellular parasites. Therefore antiviral drugs must specifically target viral functions without inhibiting essential host cell processes

86 Possible Targets for Antiviral Chemotherapy TARGET Attachment Uncoating Primary viral RNA synthesis in RNA viruses Reverse Transcription Regulation of RNA synthesis Processing of RNA transcripts Translation of viral mrna Protease processing/maturation Replication of DNA viruses Replication of RNA viruses PROTOTYPE DRUG Receptor analogs/wins Amantadine RNA-dependent RNA polymerase inhibitors AZT (zidovudine) HIV Tat inhibitors Ribavirin Interferons Protease inhibitors Acyclovir RNA-dependent RNA polymerase inhibitors

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88 Controlling Viral Infections" Public Health Measures "-Sanitation "-Vector Control "-Behavioral Changes" Vaccines" Antiviral Drugs"

89 VACCINOLOGY" Subunit Vaccines" Viral Vectors" DNA Vaccines" Peptide Vaccines"

90 Vaccines How can we prevent infectious diseases? The goal of vaccination is to induce a long lived immune response that prevents disease Requires adaptive/antigen-specific responses Long lived immunological memory Accelerated recall responses that rapidly control the infection

91 Passive immunity involves the transfer of preformed antibodies" Active immunity gives rise to long-term protection" Naturally acquired vs. artificial immunity"

92 LIVE VIRAL VACCINES" Are attenuated forms of the parental (virulent) virus. Infection with the attenuated (vaccine) strain does not cause disease but induces protective immunity. Therefore, the vaccinee is is immunologically protected if exposed to the virulent virus." " POTENTIAL PROBLEMS WITH LIVE VIRAL VACCINES:! Risk of reversion to virulence" Storage and transportation" Unrecognized agents may contaminate cultures" "! "

93 INACTIVATED or KILLED VIRUS VACCINES! Examples:" Inactivated poliovirus vaccine" Influenza virus vaccine" Hepatitis A vaccine" Rabies vaccine" Efficacy Issues:! Must ensure complete inactivation" Multiple vaccinations (boosters) may be necessary" Non-replicating agents may be less effective at eliciting immune responses"

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95 SUCESSFUL VACCINATIONS: SMALLPOX ERADICATION Virology and disease aspects! No secondary hosts; only infects humans" No persistent infection" Subclinical infections are not spread" Easily diagnosed! Immunology! Infection confers long term immunity" One stable serotype" Vaccine is cheap and stable! Social and political aspects! Severe disease with high morbidity and mortality" Eradication from developed countries demonstrated feasibility" Political willingness

96 PATHOLOGY, IMMUNE SYSTEM AND THERAPY

97 Key Points I: Viruses are obligate intracellular parasites There are numerous methods and routes of transmission They infect permissive host cells This is defines their TROPISUM Local vs. Systemic infections Primary vs. Secondary Viremia Outcomes/ Types of Infection Acute/ latent/ chronic/ transforming

98 Key Points II: Immune Responses to Viruses Innate (Interferon α/β; Macrophages; NK cells) Adaptive (B cells/ Abs; T cells/ CD4/CD8) Detrimental effects? Viral Strategies for Evading the Immune Response Hide from the immune response Downregulate gene expression Antigenic variation (DRIFTS and SHIFTS) Downregulation of cell surface molecules (MHC class I) Cytokine analogues/ interference Tolerance

99 Key Points III Infection Control PUBLIC HEALTH VACCINES Live- attenuated Inactivated- killed Advantages/ disadvantages ANTIVIRAL CHEMOTHERAPY Target a virus-specific process Avoid cellular toxicity