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15 Cards in this Set
- Front
- Back
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Routes of viral entry
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mucous membranes, mouth, respiratory tract, eye, urogenital tract, skin.
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Steps in viral replication
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Recognition and Attachment
Penetration Transcription and Translation Replication of viral genome |
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HIV recognition and attachment
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HIV glycoprotein 120 interacts with CD4+ on macrophages and T cells.
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Adenovirus (dsDNA, naked)
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capsid fiber proteins interact with cell glycoproteins and alpha-beta integrins. Clathrin mediated endocytosis.
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Penetration
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Energy dependent
non-enveloped: receptor-mediated or viropexis (direct penetration) Enveloped: fuse membranes with cellular membranes to deliver nucleocapsid or genome into cytoplasm. |
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4 mechanisms of penetration
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Endocytosis into vacuoles (endosomes)
Translocation (of entire virion across plasma membrane) Injection: after attachment, genome is injected while capsid remains outside. Fusion: virus envelope fuses with cell membrane (e.g. Herpex Simplex, enveloped, dsDNA) |
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Replication of DNA viruses
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Host cell nucleus:
ssDNA-->dsDNA replication like dsDNA Host RNA polymerase -->mRNA-->viral proteins |
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Replication of Pox viruses
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replicate in host cell cytoplasm
require encapsidated viral enzymes for transcription and replication. |
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Replication of Hepadna viruses
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dsDNA (circular, enveloped)-->RNA genome intermediate.
RNA genome -->mRNA RNA genome-->full length RNA; template for synthesis of DNA genome via reverse transcriptase (Hepatitis B) |
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RNA viruses
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Most replicate in cytoplasm and need viral proteins for replication (exceptions: orthomyxo, retro)
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Replication of +RNA
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genome serves as
1) mRNA 2) template for - strand |
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Retroviruses
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ss +RNA-->cDNA-->host genome-->mRNA (made by host)-->proteins + virus genome copies
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ss -RNA viruses
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1st: make + strand in order to make mRNA. Need to have its own machinery to do this.
Genome serves two functions 1) transcription 2) replication |
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Replication of ds RNA
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directly used as mRNA (+ strand)
RNA polymerase in capsid |
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Assembly and exit of virion
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1) maturation of virion (packaging)
2) exit by lysis of cell or budding of virus from membrane. Acquires host cell membrane proteins this way. |
