Virol 2015

Medical Virology

Prof. H. YuwonoDepartemen Mikrobiologi FK Unsri

[email protected]

EMERGING VIRAL DISEASES• HIV/AIDS• Hantavirus pulmonary syndrome (HPS)• West Nile encephalitis (WNV)• Severe acute respiratory syndrome (SARS)• Monkey pox• Human metapneumovirus• 2009 H1N1 pandemic influenza• Ebola• MERS-CoV

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Consequences of viral infections

• 50% of all absenteeism• Children: 7 or more viral infections per year that

involve a visit to a physician• Suffering, followed by recovery• Persistent disease• Fatal disease• Congenital disease• Contributory factor in cancer• Contributory factor in other diseases

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SOME ARE ASYMPTOMATIC!

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VIRUSES CAN BE USEFUL

• VACCINE DEVELOPMENT

• GENE THERAPY

• TOOLS TO INVESTIGATE HOST CELLS

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BASIC STEPS IN VIRAL LIFE CYCLE

• ADSORPTION• PENETRATION• UNCOATING AND ECLIPSE• SYNTHESIS OF VIRAL NUCLEIC ACID AND PROTEIN• ASSEMBLY (maturation)• RELEASE

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What are viruses?

• Small obligate intracellular parasites• Virion

– Complete virus particle : nucleic acid + protein coat, which may be surrounded by an envelope

• Viral Genome– EITHER RNA or DNA genome surrounded by a protective

virus-coded protein coat (Capsid)• Propagation depends on specialized host cells supplying the

machinery for replication, metabolism and biosynthesis

• The DNA or RNA genome may be :– ss – single stranded or– ds – double stranded

• Genomes may be either:– (+) sense: Positive-sense viral RNA is identical to

viral mRNA and thus can be immediately translated into protein by the host cell.

OR– (-) sense: Negative-sense viral RNA is

complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation.

• Retroviruses?

Definitions

• Bacteriophage– Virus that infects prokaryotic (bacterial) cells.

• Nucleocapsid: – viral nucleic acid + the protein coat that encloses

it.– Represents the packaged form of the viral

genome.

Viral Structure - Overview

Fig 1. Schematic overview of the structure of animal viruses

** does not exist in all viruses

Nucleic acid

CapsidNucleocapsid

Envelope protein

Membrane proteinViral envelope**

Spike protein

Virus & Bacteriophage

http://micro.magnet.fsu.edu/cells/virus.html

Viral Structure

Figure 1 An array of viruses. (a) The helical virus of rabies. (b) The segmented helical virus of influenza. (c) A bacteriophage with an icosahedral head and helical tail. (d) An enveloped icosahedral herpes simplex virus. (e) The unenveloped polio virus. (f) The icosahedral HIV with spikes on its envelope.

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HERPESVIRIDAEHEPADNAVIRIDAE

ENVELOPED

PAPILLOMAVIRIDAEPOLYOMAVIRIDAE(formerly grouped together as the PAPOVAVIRIDAE)

CIRCULAR

ADENOVIRIDAE

LINEAR

NON-ENVELOPED

DOUBLE STRANDED

PARVOVIRIDAE

SINGLE STRANDEDNON-ENVELOPED

POXVIRIDAE

COMPLEXENVELOPED

DNA VIRUSES

Modified from Volk et al., Essentials of Medical Microbiology, 4th Ed. 1991

All families shown are icosahedral except for poxviruses

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FLAVIVIRIDAETOGAVIRIDAE

RETROVIRIDAE

ICOSAHEDRAL

CORONAVIRIDAE

HELICAL

ENVELOPED

ICOSAHEDRAL

PICORNAVIRIDAECALICIVIRIDAEASTROVIRIDAE

NONENVELOPED

SINGLE STRANDEDpositive sense

BUNYAVIRIDAEARENAVIRIDAE

ORTHOMYXOVIRIDAEPARAMYXOVIRIDAE

RHABDOVIRIDAEFILOVIRIDAE

SINGLE STRANDEDnegative sense

REOVIRIDAE

DOUBLE STRANDED

RNA VIRUSES

ENVELOPED

HELICAL ICOSAHEDRAL

NONENVELOPED

Modified from Volk et al., Essentials of Medical Microbiology, 4th Ed. 1991