PORNTHIP CHAICHOMPOO

Transcription

1 SCBM344 Cellular and Molecular Pathology 2(2-0-4) Cellular and molecular pathology of PORNTHIP CHAICHOMPOO

2 OBJECTIVES Describe structure, classification and life cycle of virus Describe the mechanisms of host immune response against to pathogenic virus Describe the immune evasion of pathogenic virus Analyze the morphology of viral infected cells

3 VIRUS IS An infectious, obligate intracellular parasite Package genome in a particle for transmission from host to host Viral genome contains information to initiate and complete an infectious cycle within a cell All viral genomes are able to establish themselves in a host population so that viral survival is ensured

4 Viruses are much too small to be seen with any light microscope. The largest smallpox virus is more than 5 times smaller than E. coli and 50 times smaller than a human red blood cell.

5 VIRAL STRUCTURE GENOME; DNA OR RNA CAPSID; PROTEIN SHELL Nucleocapsid ENVELOPE; LIPID MEMBRANE (PRESENCE OR ABSENCE) HIV-1

6 VIRAL CLASSIFICATION Nature and sequence of nucleic acid in virion (viral genome) Symmetry of protein shell (capsid) Presence or absence of lipid membrane (envelope) Dimension of virion & capsid

7 VIRAL CLASSIFICATION: I. CLASSICAL HIERARCHICAL SYSTEM KINGDOM International Committee on Taxonomy of Viruses (ICTV) PHYLUM/DIVISION CLASS ORDER (~VIRALES) FAMILY (~VIRIDAE) GENUS (~VIRUS) Unassigned SPECIES (~VIRUS) Retroviridae GROUP/SUBTYPE Lentivirus HIV-1 M Piconavirales Picornaviridae Enterovirus Enterovirus C

8 Viral classification: II. Baltimore classification system The original Baltimore system missed one genome type: Group VII: dsdna-rt (e.g. Hepadnaviruses) VII dsdna-rt Clues; ü DNA of equivalent polarity is also (+) strand ü Complementary of (+)strand RNA/DNA is (-)strand ü mrna is always (+)strand ü mrna is ribosome ready. Therefore, it can be translated into protein ü NOT ALL (+)RNA is mrna!!! S.J. Flint et al., 3 rd Principles of Virology.ASM Press.2009.

9 Viral classification: II. Baltimore classification system 7 Groups I. dsdna viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses) II. ssdna viruses (+ strand or "sense") DNA (e.g. Parvoviruses) III. dsrna viruses (e.g. Reoviruses) IV. (+)ssrna viruses (+ strand or sense) RNA (e.g. Picornaviruses, Togaviruses) V. (-)ssrna viruses (- strand or antisense) RNA (e.g. Orthomyxoviruses, Rhabdoviruses) VI. ssrna-rt viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses) VII. dsdna-rt (e.g. Hepadnaviruses) KEY NOTE If you know the genome structure, you should be able to deduce; ² How mrna is made from the genome ² How the genome is copies to make more genomes

10 Bal. sys. I II Copyright 2013, 2010, 2007 Pearson Education, Inc.

11 Bal. sys. III IV Copyright 2013, 2010, 2007 Pearson Education, Inc.

12 Bal. sys. V VI Copyright 2013, 2010, 2007 Pearson Education, Inc.

13 LIFE CYCLE OF VIRUS

14 INFECTIOUS CYCLE 1. ATTACHMENT & ENTRY INTO TARGET CELL 2. VIRAL GENOME REPLICATION AND VIRAL PROTEIN SYNTHESIS 1RNA SYNTHESIS 2REPLICATION OF DNA VIRAL GENOMES 3TRANSCRIPTION & RNA PROCESSING 4REVERSE TRANSCRIPTION & INTEGRETION 5TRANSLATION 3. ASSEMBLY

15 Infectious cycle: ATTACHMENT & ENTRY INTO TARGET CELL 1. Direct penetration; e.g. poliovirus Cowan M.K. The McGraw-Hill (2012) Bauman R.W. Pearson Education (2012)

16 Infectious cycle: Attachment & Entry into Target cell 2. Membrane fusion Cowan M.K. The McGraw-Hill (2012) Bauman R.W. Pearson Education (2012)

17 Infectious cycle: ATTACHMENT & ENTRY INTO TARGET CELL 3. Endocytosis Ø Most enveloped viruses and some naked viruses enter host cells by triggering endocytosis. Ø Attachment of the virus to receptor molecules on the cell s surface stimulates the cell to endocytize the entire virus. Ø Adenoviruses (naked) and herpesviruses (enveloped) enter human host cells via endocytosis. Bauman R.W. Pearson Education (2012)

18 ASSEMBLY The majority of viruses leave an infected cell by; Release from the cell by budding or lysis Exocytosis

19 S.J. Flint et al. ASM Press Group: V (-)ssrna Order: Unassigned Family: Orthomyxoviridae Genus: Influenza A HA = hemagglutinin NA = neuraminidase M1, M2 = viral proteins

20 S.J. Flint et al. ASM Press Group: I dsdna Order: Herpesvirales Family: Herpesviridae Subfamily: Alphaherpesvirinae Genus: Simplexvirus Species: HSV-1 or HSV-2

21 HOST DEFENSE TO VIRAL INFECTION

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23 Innate immunity to viral infection Antigen presenting cells Monocytes/macrophage Dendritic cells Viruses 2011;3:

24 IFN: antiviral agent Abbas et al 2009 ISG The interferon-stimulated genes that restrict viral replication and confer an antiviral state. Swiecki M and Colonna M.Curr Opin Virol Dec;1(6):

25 IFN: antiviral agent Swiecki M and Colonna M.Curr Opin Virol Dec;1(6):

26 Adaptive immunity to viral infection

27 Adaptive immunity to viral infection Nature Biotechnology.2007;25(12):

28 VIRUSES EVADE IMMUNE RESPONSES

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30 MECHANISM OF 1. Pathogenic viral infectious cycle 2. Immunity to viral infection 3. Immune evasion by virus

31 DNA virus Family Genera Diseases/Clinic Poxviridae Orthopoxvirus Smallpox/Variola Mulluscipoxvirus Molluscum contagiosum Herpesviridae Simplesvirus HSV-1, HSV-2 Varicellovirus VZV/chickenpox Epstein-Barr Virus Burkitt s lymphoma Baltimore system I-II DNA DdDp/DdDp * DNA Viral enzymes: DdDp = DNA-dependented DNA polymerase Host enzymes: DdDp = DNA-dependented DNA polymerase 2002 J.S. & E.S.

32 Infectious cycle: HSV-1 1. Virion attachment and entry into the cell 2. Transport to the nucleus 3. Viral gene expression: (a) immediate early, (b) early and (c) late 4. Viral DNA replication 5. Nucleocapsid assembly 6. Capsid maturation 7. Primary envelope formation 8. Egress by exocytosis Kukhanova MK, et al.biochemistry (Mosc) Dec;79(13):

33 S.J. Flint et al. ASM Press Group: I dsdna Order: Herpesvirales Family: Herpesviridae Subfamily: Alphaherpesvirinae Genus: Simplexvirus Species: HSV-1 or HSV-2

34 Immunity to HSV Host cell - Macrophages - Dendritic cell - Fibroblasts - Epithelial cells Melchjorsen J.Rev Med Virol Mar;22(2):

35 Immune evasion by HSV A. HSV vhs proteins interfere with cell protein translation by specifically degrading host mrnas. B. Viral US11 and γ34.5 interfere with host PKR function, by impairing its capacity to phosphorylate EIF2A, which blocks translation within infected cells. C. Host sensors activate TRAF3 after detecting HSV determinants, which normally leads to IRF3 activation. However, UL36 interferes with TRAF3 ubiquitination blocking its IRF3-activating capacity. ICP0 and US3 also interfere with IRF3 activation. Impaired IRF3 function will result in poor secretion of interferons by infected cells. D. Viral ICP27 interferes with STAT-1 signaling mediated by IFNR, which would otherwise lead to the secretion of antiviral effectors. Suazo PA, et al.mediators Inflamm. 2015;2015:

36 dsdna-rt virus Hepadnavirus Hepatitis B virus Pregenomic (pg) Beck J and Nassal M. World J Gastroenterol 2007;13(1): J.S. & E.S.

37 Infectious cycle: HBV Urban S, et al.j Hepatol Feb;52(2):282-4.

38 THE LIFE CYCLE OF HEPATITIS B VIRUS Biorad.com

39 Immunity to HBV Zoulim F, et al.gastroenterology Jun;144(7):

40 Immune evasion by HBV Rehermann B.Nat Med Jul;19(7):

41 15 min

42 NATURE OF THE RNA TEMPLATE (+) Strand RNA genomes: naked, ready to be translated upon entry (exception: retrovirus, coronavirus) (-) Strand RNA genomes: coated with protein; ready to begin RNA synthesis upon entry dsrna genomes: cannot be copied into mrna by the cell; virions contain RNA polymerase

43 (+)ssrna virus Family Togavirus Genera Diseases/Clinic Alphavirus Chikungunya Rubibirus Rubella Family Flaviviridae Genera Flavivirus Virus Diseases/Clinic Yellow fever Hemorrhage&Hepatitis Dengue Dengue fever / DHF Zika Microcephaly 2002 J.S. & E.S.

44 Infectious cycle: DENGUE VIRUS Screaton G, et al. Nat Rev Immunol Dec;15(12):

45 (-)ssrna virus Family Orthomyxoviridae Genera Diseases/Clinic Influenza virus Influenza Family Paramyxoviridae Genera Paramyxovirus Virus Diseases/Clinic Mumps Parotitis, Orchitis Meningoencephalitis Genera Morbillivirus Virus Diseases/Clinic Measles Measles Family Filoviridae Genera Filovirus Virus Diseases/Clinic Ebola Systemic inflammatory response syndrome 2002 J.S. & E.S.

46 Infectious cycle: INFLUENZA A VIRUS Qiagen.com

47 Immunity to Influenza Influenza evade immunity Iwasaki A and Pillai PS.Nat Rev Immunol May ; 14(5):

48 (+)ssrna-rt virus Retrovirus HIV J.S. & E.S.

49 HIV entry into target cell Abbas et al 2009

50 HIV life cycle Abbas et al 2009

51 Antiviral model of HIV-1 infection DeVico AL and Gallo RC. Nat Rev Microbiol May;2(5):

52 HIV-1 diversity Goulder PJ and Watkins DI.Nat Rev Immunol Aug;8(8):

53 HIV-1 transmission Izquierdo-Useros N, et al.blood. 2009;113: )

54 Progression of infection Abbas et al 2009

55 Progression of infection Abbas et al 2009

56 Clinical course of HIV diseases Abbas et al 2009

57 AVERAGE TIME AFTER EXPOSURE TO DETECT HIV ANTIGENS AND ANTIBODIES

58 Absolute number of CD4/CD8 T cells

59 Viral load

60 ELISA detection for human HIV-1 infection Patient serum B

61 THE MORPHOLOGY OF VIRAL INFECTED CELLS

62 DEFINITION OF VIRAL INFECTION

63 DEFINITION A resistant cell: the cell has no receptor it may/may not be competent to support viral replication A susceptibility cell: the cell has a functional receptor for given virus it may/may not be able to support viral replication A permissive cell: the cell has capacity to replicate virus it may/may not be susceptible A susceptibility and permissive cell: the only cell that can take it and replicate it.

64 Host cells DEFINITION Infection Viral genome replication Resistant cell X X Susceptibility cell ± Permissive cell ± Susceptibility & permissive cell

65 HIV-1 variants VIROLOGY Target 235, cell types (1997) Annu. Rev. Immunol :

66 X4 T-tropic HIV-1 Permissive cell Susceptibility cell x Resistant cell

67 U87 null cell line U87.CD4.CCR5.CXCR4 cell line Princen K, et. al. Retrovirology 2004

68 CYTOPATHIC EFFECT (CPE)

69 EFFECTS OF VIRUS TO INFECTED CELLS CYTOCIDAL INFECTION STEADY-STATE PERSISTENT INFECTION CELLULAR TRANSFORMATION

70 A. CYTOCIDAL INFECTION Cell death and histological appearance of characteristic CPE e.g. Picornaviruses, herpesviruses Many viruses can inhibit host DNA, RNA and protein synthesis. E.G., Picornaviruses, herpesviruses, adenoviruses Cell endosomes may be damaged, resulting in the release of hydrolytic enzymes and cell destruction Infected cells usually swell

71 INCLUSION BODIES (CPE) Intracellular structures of viral proteins or virions May result from the clustering of subunits or virions within the nucleus or cytoplasm (e.g., The Negri bodies in rabies infections) May contain cell components such as ribosomes (arenavirus infections) or chromatin (herpesviruses) Regardless of their composition, these inclusion bodies can directly disrupt cell structure. Negri bodies Tortora GJ, et.al.microbiology-an introdution.11 th ed Copyright 2013, 2010, 2007 Pearson Education, Inc.

72 Virus infection can drastically alter plasma membranes through the insertion of virus-specific proteins so that the infected cells are attacked by the immune system. When infected by viruses such as herpesviruses and measles virus, as many as 50 to 100 cells may fuse into one abnormal, giant, multinucleated cell called a syncytium. HIV appears to destroy CD4 T-helper cells at least partly through its effects on the plasma membrane. Measles virus Tortora GJ, et.al. Pearson Education.2013.

73 B. STEADY-STATE PERSISTENT INFECTION Infected cells: Produce and release virus but no CPE, may be found syncytia Can grow and divide but not killed Little destruction of infected cells Does not occur with DNA viruses Occur with several RNA viruses (lassa virus, retoviruses, rubella, some paramyxoviruses) Virus released by cell budding

74 C. CELLULAR TRANSFORMATION Viruses produce tumors in animals can transform cell culture Patient with EBV Infection Virus DNA integrated into host DNA, alter growth and morphology Chromosomal abnormalities New virus ag and DNA production e.g. Adenovirus, HPV, HSV, EBV, HBV, sarcoma virus, HTLV1,2 Willey JM, et. al.mcgraw-hill (2008)

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