the world and viruses

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Conrad Mervyn Bell
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1 More than 5,450 viruses belonging to more than 2,000 species, 287 genera, 73 families and 3 orders are recognized in the 8th ICTVreport report. the world and viruses 1

1889 H2N2 Emerging viruses in the past: Some

for plasma safety 1968 HongKong H3N2 2002

Hantavirus 90ties vcjd 1880 1900 `20 `40 `60

2 1889 H2N2 Emerging viruses in the past: Some examples: CJD included due to its relevance for plasma safety 1968 HongKong H3N SARScoronavirus 1977 USSR H1N Korea Hantavirus 90ties vcjd `20 `40 `60 ` Asia H2N2 Chickungunya spanish flu H1N1 80ties HIV 70ties Enterovirus 70 Coxsackievirus A24 HCV 1999 WNV in North America 2

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4 What is a virus: A particle composed of a nucleic acid and protein, in some cases surrounded by a host derived lipid membrane Viruses are obligatory parasites 4

5 How big is a virus: The size varies from approx. 20 nm (Parvoviridae) up to ~350 nm (Poxviridae) virus bacteria erythrocyte 5

6 Non enveloped viruses nucleic acid protein 6

7 Enveloped viruses nucleic acid protein lipid membrane with proteins embedded 7

IV: Single stranded (+)sense RNA (Picornaviruses; Togaviruses, etc) a) Polycistronic mrna e.g. Picornaviruses; Hepatitis A. Genome RNA = mrna.

8 III: Double stranded RNA (Reoviruses; Birnaviruses) These viruses have segmented genomes. Each genome segment is transcribed separately to produce monocistronic mrnas. IV: Single stranded (+)sense RNA (Picornaviruses; Togaviruses, etc) a) Polycistronic mrna e.g. Picornaviruses; Hepatitis A. Genome RNA = mrna. Means naked RNA is infectious, no virion particle associated polymerase. Translation results in the formation of a polyprotein product, which is subsequently cleaved to form the mature proteins. b) Complex Transcription e.g. Togaviruses. Two or more rounds of translation are necessary to produce the genomic RNA. 8

9 Baltimore classification I: Double stranded DNA (Adenoviruses; Herpesviruses; Poxviruses, etc) Some replicate in the nucleus e.g adenoviruses using cellular proteins. Poxviruses replicate in the cytoplasm and make their own enzymes for nucleic acid replication. II: Single stranded d(+) (+)sense DNA (Parvoviruses) Replication occurs in the nucleus, involving the formation of a ( )sense strand, which serves as a template for (+)strand RNA and DNA synthesis. III: Double stranded RNA (Reoviruses; Birnaviruses) These viruses have segmented genomes. Each genome segment is transcribed separately to produce monocistronic mrnas. IV: Single stranded (+)sense RNA (Picornaviruses; Togaviruses, etc) a) Polycistronic mrna e.g. Picornaviruses; Hepatitis A. Genome RNA = mrna. Means naked RNA is infectious, no virion particle associated polymerase. Translation results in the formation of a polyprotein product, which is subsequently cleaved to form the mature proteins. b) Complex Transcription e.g. Togaviruses. Two or more rounds of translation are necessary to produce the genomic RNA. 9

10 V: Single stranded ( )sense RNA (Orthomyxoviruses, Rhabdoviruses, etc) Must have a virion particle RNA directed RNA polymerase. a) Segmented e.g. Orthomyxoviruses. First step in replication is transcription of the ( )sense RNA genome by the virion RNA dependent RNA polymerase to produce monocistronic mrnas, which also serve as the template for genome replication. b) Non segmented e.g. Rhabdoviruses. Replication occurs as above and monocistronic mrnas are produced. VI: Single stranded (+)sense RNA with DNA intermediate in life cycle (Retroviruses) Genome is (+)sense but unique among viruses in that it is DIPLOID, and does not serve as mrna, but as a template for reverse transcription. VII: Double stranded DNA with RNA intermediate (Hepadnaviruses) This group of viruses also relies on reverse transcription, but unlike the Retroviruses, this occurs inside the virus particle on maturation. On infection of a new cell, the first event to occur is repair of the gapped genome, followed by transcription. 10

First step in replication is transcription of the ( )sense RNA genome by the virion RNA dependent RNA

b) Non segmented e.g. Rhabdoviruses. Replication occurs as above and monocistronic mrnas are produced.

(+)sense but unique among viruses in that it is DIPLOID, and does not serve as mrna, but as a

VII: Double stranded DNA with RNA intermediate (Hepadnaviruses) This group of viruses also relies on

11 V: Single stranded ( )sense RNA (Orthomyxoviruses, Rhabdoviruses, etc) Must have a virion particle RNA directed RNA polymerase. a) Segmented e.g. Orthomyxoviruses. First step in replication is transcription of the ( )sense RNA genome by the virion RNA dependent RNA polymerase to produce monocistronic mrnas, which also serve as the template for genome replication. b) Non segmented e.g. Rhabdoviruses. Replication occurs as above and monocistronic mrnas are produced. VI: Single stranded (+)sense RNA with DNA intermediate in life cycle (Retroviruses) Genome is (+)sense but unique among viruses in that it is DIPLOID, and does not serve as mrna, but as a template for reverse transcription. VII: Double stranded DNA with RNA intermediate (Hepadnaviruses) This group of viruses also relies on reverse transcription, but unlike the Retroviruses, this occurs inside the virus particle on maturation. On infection of a new cell, the first event to occur is repair of the gapped genome, followed by transcription. 11

12 Semliki Forest virus: Membrane fusion 12

13 Triangulation number= Area of equilateral triangle of sides S (new face) Area of small equilateral triangle representing 1 subunit 1

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number Done by Corrected by Doctor Ashraf

number Done by Corrected by Doctor Ashraf number 4 Done by Nedaa Bani Ata Corrected by Rama Nada Doctor Ashraf Genome replication and gene expression Remember the steps of viral replication from the last lecture: Attachment, Adsorption, Penetration,