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Viral characteristic
| Question | Answer |
|---|---|
| Unique properties of viruses | Either DNA or RNA, strict intracellular parasite, replicates in host cell, uses host cell to replicate nucleic acid. |
| viral structure | nucleic acid surrounded by capsid and possibly a lipid or polysaccharide envelope |
| capsid | protein shell around nucleic acid |
| nucleocapsid | nucleic acid + capsid |
| capsomere | structural unit of capsid |
| envelope | lipid membrane around nucleocapsid in some viruses- stolen from host cell, factor of antigenicity |
| vorion | complete viral particle |
| Charactoristics used to classify viruses | DNA or RNA, ss or ds, size and shape of virus, envelope, host cell infected, disease produced |
| prion | proteinatious infectious particle, replicate through conversion of other host proteins |
| diseases caused by prions | Scrapie, Kuru, CJD, BSE bovine spongiform encephalitis (mad cow) |
| Major steps in viral replication | attachment, penetration, uncoating, biosynthesis, morphogenesis, release |
| Herpes simplex virus type 1 (HSV1) | Fever blisters- infect nervous tissue |
| Herpes simplex virus type 2 (HSV2) | genital area- infect nervous tissue |
| Cytomegalovirus (CMV) | found in the lymphotropic- lympatatic system |
| Epstein-Barr virus (EBV) | found in the lymphotropic- lympatatic system |
| Overall Structure double-stranded DNA genome | encodes for 60-120 genes- 1 copy- linear |
| icosahedralcapsid: | 5 diff. proteins |
| tegument: | enclosed a group of protein tha are needed for early infection, they are going to start the replication process. They help turn off the functions |
| Envelope | Viral derives proteins host derived photolipids |
| Infection cycle 1.Binding | invalue viral glycoproteins (gc,gd) Envelope going to search for specific receptors on the host cell |
| RNA transcription/DNA replication In the nucleus: viral DNA can either circularizeddue to cellular DNA repair enzymes circularized state: | the virus becomes latent |
| In the nucleus: viral DNA can either circularizeddue to cellular DNA repair enzymes or it can remain linearthrough the action of the immediate-early ICP0 protein, which inhibits cellular DNA repair. linear state: | a productive replication cycle begins |
| Two main phases of transcription •Early: ____________________________________________ •Late: ____________________________________________ | transcription that occures before DNA replicates |
| Two main phases of transcription ____________________________________________ •Late: ____________________________________________ | transcription that occures during DNA replication |
| Early transcription Immediately early genes | set of 5 |
| Early transcription Immediately early genes | MRNA is formed in the nucleus, they are primed by the tegament proteins |
| Early transcription Immediately early genes | MRNA will leave nucleus and enter cytoplasma looking for ribosomes immediate early proteins go back into lucleus- they they will prime the next round of transcription. |
| Early transcription Delayed early genes | 12 geans are needed for the next process structual proteins and replicate DNA |
| Early transcription Late transcription | Structural proteins are being made- host shut down - capsid protein - envelope proteins Start DNA replication Early transcription ends. |
| all Herpesvirusescan establish latencyin the body after primary infection | Latency = virus is dormant in cell |
| Latent herpes viral genome (DNA) may be | circular form inside host cell No treatment to prevent establishment of latent infections. Nor will remove altent virus |
| Latency occurs within specific nerve cells –HSV-1: | trigeninal ganglia |
| Latency occurs within specific nerve cells ––HSV-2: | Sciatic nerve gangha |
| HSV-1 and HSV-2: are not systemic illnesses | will only be infecting one part of your body |
| systemic illnesses | systemic a pathogen able to infect the whole body like to hide inside the cells and avoid the host immune system. |
| Transmission of HSV1 | oral to aral |
| HSV1 virus multiplies | in the epithelia cell of the mouth, throat, face - result distrys some cells |
| Cells often fuse together producing | multinuncleated giant cells |
| Blisters develop at the inoculation site | coldsores-fever blisters saliva and cells secretions contain the virus particle |
| Transmission of HSV2 | spread via break in skin or mucus membranes- most often throu sexual contact will end up having blisters on the external genitalia |
| HSV2 blister form | large multinucleated cells- can have upto 50,000-200,000 virus per cell |
| HSV2 incubation time | 1 week- shedding host cell lyse to reveal virus |
| HSV2 replication | virus will use host machinary to replicate viruses- Shuts down the host matabolism. |
| What are the two enzymes that virus makes | Viral thymidine kinase DNA polymerase |
| Viral thymidine kinase | provide substrates for replication of viral genome |
| DNA polymerase | diff. from the cellular DNA polymerase in subtrate specificity |
| most effective drug agains HSV | Acyclovir (zovirax) |
| Herpes thymidine kinase | add a phosphate group to acyclovir |
| Cellular enzymes | kinases adds 2 phosphate groups |
| Acyclovir has two mechanisms of action Mechanissm 1 | acyclovir triphosphate bond to viral DNA- inactivates |
| Acyclovir has two mechanisms of action Mechanissm 2 | acyclovir triphosphate incorporated in the newly synthesized virus DNA- stops viral replication |
| varicella | chicken pox |
| Zoster | shingles |
Created by:
kmaemom
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