1.a.infeksi Virus

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MUHAMMAD ASAAD MAIDIN

Department of Microbiology, Faculty of Medicine,Hasanuddin University, Makassar



The objectives are that students should be

able to know and understand

1. The nature, structure and classification

of viruses.2. The differences of replication cycle of

viruses between DNA and RNA.

3. The ability of viruses to cause diseaseand effect viruses on host.







PROPERT

IES OF VIRUSES1. Virus structure consist of : Nucleic acid ,

capsomer / capsid and envelope

2. Genome can be either DNA or RNA3. Viruses do not have ribosome

4. Viruses do not replicate by binary fission

5. Viruses range from 18 nm to 300 nmin diameter.



6. Obligate intracellular organisms

7. Sensitive to interferon

8. No sensitivity to antibiotics

9. Can not grow on artificial media.



* The arenavirus family (an RNA virus family) appears to package ribosomes 'accidentally'. The packaged ribosomes

appear to play no role in viral protein synthesis.

Differentiation between Bacteria, Mycoplasma, Rickettsia,

Chlamydia and Viruses

Their growth

on artificial

media

Division by

binary fission

Whether they

have both DNA

and RNA

Whether

they have

ribosomes

Their

sensitivity to

antibiotics

Bacteria + + + + +

Mycoplasma + + + + +

Rickettsia - + + + +

Chlamydia - + + + +

Viruses - - - - -



STABILITY OF VIRUSES

- Stable when added MgCl2, MgSO4,Na2SO4

- Stable is important for preparing vaccine.

PH 5.00 -9,00

- When exposed to ultra violet lamp¼

lossactivity.



CHEMISTRY PROPERTIES OF VIRUSES´

Destroyed on 50o-60oC,with in 30¶.

Can be kept in -70oC for several months

and in -170oC for years in Nitrogen tank.

To keep in -170¶C must be mixed with

dimeth

yl sulfoxide (DMSO) 5 % for

maintenance their activity.



Gbr 3.

DNA double helix

Sugar-phosphate

backbone

Nucleotides



DNA double helix

Three dimension



NUCLEIC ACID VIRUS Either DNA or RNA

DNA virus is always in double

stranded, except Parpovirus insingle stranded.

RNA virus is always in single

stranded, except Reovirus in doublestranded.



NAKED ICOSAHEDRAL

NAKED HELICAL



FIVE BASIC STRUCTURAL FORMS OF

VIRUS S YMMETR Y

1. Naked icosahedral symmetry, e.g.

poliovirus, adenovirus, hepatitis A virus.

2. Naked helical symmetry, e.g. tobacco

mosaic virus, so far no human viruses

with this structure known.



3. Enveloped icosahedral symmetry, e.g. herpes

virus, yellow fever virus, rubella virus

4. Enveloped helical symmetry, e.g. rabies virus,

influenza virus, para influenza virus, mumps

virus, measles virus

5. Complex symmetry e.g. poxvirus



COMPLEX SYMMETRY; POX VIRUS









Basic Classification of Viruses

Nucleic acid

- RNA or DNA- single-stranded or double-stranded

- nonsegmented or segmented

- linear or circular

- if genome is single stranded RNA, canit function as mRNA?

- whether genome is diploid (it is in

retroviruses)

Virion structure

- symmetry (icosahedral, helical,complex)

- enveloped or not

- number of capsomers













GLOSSAR Y :

1. Capsid : The protein coat that surrounds the

nucleic acid of a virus.

2. Nucleo Capsid : The virus structure composedof the nucleic acid surrounded by the capsid.

3. Capsomer : Substructure of virus particle.

4. Genome : A set of genes



5. Envelope : A host cell derived membrane,

containing virus specific antigens, that¶s is

acquired during virus maturation.

6. Virion : the mature virus particle, with all

of its structural components intact.



T-Lymphocyte

Muh.Asaad Maidin

Glucoprotein virus

Attached to receptor CD4

& co-receptor of sel T



Muh.Asaad MaidinPenetration and

uncoating

T-Lymphocyte





DNA Virus Replication



DNA VIRUS REPLICAT

IONe.g. Adeno virus

1. Attachment, Penetration and uncoating

Viral capsid proteins interact with cellsurface receptors and penetration is probably via

endocytosis. Virion are transported to the nucleus

and uncoated . DNA enter nucleus, probably

through a nuclear pore.



2.Early transcription and early translation :

Adenovirus uses host cell polymerase, early

mRNA trascribed and mRNA processed by host

cell. T he DNA replicate by a strand displacementmechanism.

3. Late transcription and late translation :

Late mRNA code predominantly for structural proteins.



4. Assembly : occurs in the nucleus DNAenters the particles after immature capsidare formed.T he capsid undergo amaturation process, after which the cell

lyse and the virion leak out.5. Budding/ release. Virions may be

released due to cell lysis. Budding virusesdo not necessarily kill the cell, some may

be able to set up persistence.



RNA VIRUS REPLICAT

ION

1). RNA virus do not copy their RNA into

DNA.

2 ). RNA virus which copy their RNA into

DNA



1). RNA virus do not copy their RNA into DNA.

Need an RNA-dependent RNA-polymerase to

replicate their RNA.

No viral protein can be made until viral m-RNA

available.



1.1. Plus stranded RNA viruses.

The virion RNA is the same sense as

m-RNA so function as m-RNA. Thism-RNA can be translated immediately

upon infection of the host cell.

eg. Picornavirus , polio virus, togavirus,flavivirus



1.2. Negative stranded RNA viruses.

The virion is negative sense as a

complementary to m-RNA copied into the

complementary plus-sense m-RNA. Needs tocode RNA-dependent RNA-polymerase.

eg. Orthmyxovirus, measles virus,

rabies virus, mumps virus.



1.3. Double stranded RNA virus (dsRNA )

The virion RNA is double stranded so

cannot function as m-RNA needed

RNA- polymerase to make mRNA

e.g. Rotavirus



2 ). RNA viruses which copy their RNA into DNA.Retroviruses although plus-sense, virion

RNA is not release in the cytoplasm, so

does not function as mRNA. Virion RNA serve

as a template for Reverse transcriptaseenzyme (RT ) immediately copied into DNA.

Retroviruses need to code RT enzyme and

package it in virion.



HIV Life Cycle - Prof.Dr.dr.Asaad Maidin M.Sc.exe



There are four main effects of virusinfection on the cell:

1. Death

2. Fusion of cells to form multinucleated cells.3. Malignant transformation

4. No apparent morphologic or function

change



R eferences ;

1. Cohen,J., Powderly,W.G.,et al, 2004.Infectious Diseases, 3 rd edith. Mosby.

2. Levinson, W., and Jawetz, E., 2002 Medical

Microbiology, a Lange medical book, seventh edith.

3. Metseelar, D., and Simpson,D.I.H.,1982.

Practical virology, For Medical Students andPractisioners in Tropical Countries, Oxford Univ.Press.

4. Mims,C.,Dockrell,H.M, et al, 2004.

Medical Microbiology, 3rd edith.Elsevier Mosby.

5. Virella, G., 1997. Microbiology and Infetious Diseases,

3rd edition,William & Wilkins a waverly company.

6. Internet.





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