Viruses I – Structure of viruses

Lecture 89

Mgr. M. Jelínek

michael.j@email.cz

Obsah

1) Virus as a entite

2) Introduction to virology

3) Composition of virion

4) Viral replication strategies

1) Viruses are the entities:

• Physical – shape, weight, size

• Biochemical – consisting of nucleid acids, proteins, phospholipids

• Biological

• Infectious agens

Virus as a biological entite

• Intracelullar obligate parasites +/-

• They have no ribosoms or energetic metabolism either -

• They have no binar division -

• They have a genom (RNA or DNA) +

• They are affected by biological evolution +

• They interact with living organisms +/-

2) Introduction to virology

Viruses of procaryots: bacteriofages, cyanofages, mycofages, viruses of protozoans, viruses of plants, animals, human Can we use

bacteriophages in medicine?

Probably not, but...

in ecology, research

We can

Subviral entities

• Viroids

Free chains of RNA, can cause deseases, mostly in plants

Virusoids – „parasites of virus“, hepatitis D

Briefly the history of virology

• Babylonia, Antient Greek – knowledge of rabies• Chine – very simple vaccination against small

pox • Egypt – hieroglyfs with people with polymyelitis• Breeding of plants• Vaccination – 18. century, England• L. Pasteur, vaccination against rabies virus

The 20. century

1892: Dimitrij Ivanovski – tabbaco virus desease

1898: Loeffler a Frosh - foot and mouth disease

1901: Carlos J. Finlay, Colonel W. Reed -virus of yellow fever – building of Panama canal

1911: Peyton Raus - virus and sarkomas

1915, 1917: Twort, dHérelle - bacteriofags

1935: W. Stanley – tabbaco virus desease was observed

Importance of virology

• Stopping of spreading of dangerous or pandemic incectious diseases

• Research of common diseases

• New treatment approach – gene therapy, nanotechnologies

• Metodical advances in molecular biology

• Informations in ecology and evolution biology

Important viral infection in the 20. century

• Influenza epidemies, most important 1919

• Dengue fever, tick born encephalitis

• Ebola virus

• Virus HIV, 80´s

The origin of viruses

regressive theory (viruses developed from cellular parasites)

origin in cellular RNA or DNA

coevolution of viruses from beggining of life origin in catalytical, autoreplicated RNA molecules

Methods of viral investigation

• Centrifugation – diferencial centrifugation, ultracentrifugation, electrone microscopy

• PCR, elektrophoresis, imunodetection, fluorescence microscopy

• Cell cultures, animal models, plaque assays

• Epidemiological methods, screening of population

3) Virion

Composition of virion:

• Nucleid acid (genom)

• Capsid

• Envelope (only enveloped viruses )

Nucleocapsid –virion, or capsid and genomu for coated viruses

http://hiv.boehringer-ingelheim.com/com/HIV/Information_material/Images.jsp

Viral nucleid acid

= viral genom: RNA/DNA, circular/linear, ss/ds, segmented, nonsegmented

Mostly 5 – 50 kb, 5 – 100 genes

Genes for • Structural genes – proteins of capsids, glykoproteins of

envelope, proteins of matrix• Non – structural genes – enzymes, oncogenes• Non – coding regulatory regions – promotors...• Genes ale often overlapped, are produced at clusters

and so on

Capsid is protein- made structure with genom in its inner

Composition of capsids:• Identical structural protein units - capsomers. • Capsomere is composed from structure viral

proteins

Capsid

Basic types: • ikozahedron consists of  20

triangular areas with 12 peaks (globular proteins)

• Helixal complex (viz cytoskelet), filium/bacillus viruses

• Cell like viruses

• Complicated structures of bacteriofags (head, flagellum, spikes)

Morfology of capsid:

Převzato z: www.biol.vt.edu

Viral envelope

• Phosfolipid bilayer with origin in cell membrane

• It contains glycoproteins – coded by viruses, they interacts with cell receptor

• It contains glycoproteins – coded by viruses, they interacts with cell receptor

Properties of viral envelope

• Primary potects the genom

• It helps to spread the viral genom

• Viral and cellular membranes can fused

Proteins of viral envelope - antigenes

Other components

• Virion can contain other proteins – enzymes, cellular proteins, viral chaperons

• Proteins used against imunne system

• Proteins for latency

4) Replication strategies of viruses

• DNA viruses – ssDNA, dsDNA

• RNA viruses – ssRNA, ds RNA

• Retroviruses – RNA transcribed to DNA and back to RNA

• Hepadnaviruses – DNA transcribed to RNA and back to DNA

RNA

(+)ssRNA (-)ssRNA dsRNA

DNA

ssDNA dsDNA

Viruses with reverse transcriptase

RetrovirusesRNA

Hepadnaviruses DNA

mRNAmRNA

dsDNA

HERPESVIRY

POXVIRY

I.I. ssDNA

II.II.

PARVOVIRY

dsDNA

dsRNA

III.III.

REOVIRY

IV.IV.(+)ssRNAPICORNAVIRY, TOGAVIRY

(–)ssRNA

(–)ssRNA

(+)ssRNA

V.V.ORTHOMYXOVIRYRHABDOVIRY

(+)ssRNARETROVIRY

Reverzní transkripceVI.VI.

dsDNAHEPADNAVIRY

VII.VII.