Lecture 15-Viruses

living cells

Viruses must be grown in _________

plaques

Bacteriophages form ________ on a lawn of bacteria

cell culture

Animal and plants viruses may be grown in __________

living animals or in embryonated eggs

Animal viruses may be grown in ___________ or _____________

1.)infect cells and incubate

2.)incubate at 37 degrees

3.)Take sample of the mixture after every hour

4.)separate cells from the liquid(supernatant)

5.)make serial dilutions(water down sample) and do plaque assay

Overview of One Step growth curve -experiment

‘plaque forming units’ (PFU)

______________________ is a common way to measure the amount of virus in solution

Eclipse, Maturation, and Release

Three growth phases from a one-step growth curve

-the virus as entered the cell and is apart of the host cells machinery to begin mass production.

-the phase ends when the first viral parts are assembled into mature virions

Question - what is going on during eclipse - why

no sign of virus?

1.)Attachment and Pentration

-uncoating

2.)Transcription of early mRNA

-translation of early proteins

3.)Replication of viral genome

-transcription of late mRNA

4.)Translation of late proteins

-assembly of virions

List steps of the Eclipse in viral replication cycle

enzymes that are needed to replicate genome

For the eclipse phase of Viral replication cycle:

What are the early proteins that are translated?

structural proteins for virion

For the eclipse phase of Viral replication cycle:

What are the late proteins that are translated?

nucleus or cytoplasm

What are the two locations where some of the eclipse phase steps occur?

List the steps of Multiplication of viruses

List the steps of Bacteriophage Life Cycle

-Attachment to host cell receptor

-Entry into cell via endocytosis(brought into cell in an endosome)

-Fuses envelope to plasma membrane

-releases capsid into cytoplasm

Brief Overview of Attachment of Eukaryotic Virus Attachment

Non-enveloped-binds to capsid

Enveloped-binds viral glycoproteins(receptor binding protein)

Differences in viral receptor on non-enveloped vs enveloped viruses?

-trigger conformation in capsid for entry

-conformational change in glycoprotein for entry

-May send signals to cells

What are the three things that can be triggered from virus binding?

CD4 and CCR5

HIV receptor _____ and coreceptor ______

ACE2

SARS-Cov2 viral receptor

Tropism

the spectrum of tissues and cell types infected by a given virus.

appropriate viral receptor

Tropism is often explained by the presence or absence of the ______________________

Each type of virus binds to one (usually) or more (rarely) receptors to attach to the cell surface, initiating the entry process.

What is the general specificity for viruses to receptors

polymerase

DNA viruses must go to cell nucleus to use host ___________

Poxvirus

Viruses that replicate in cytoplasm with viral polymerase

viral polymerase

 RNA viruses must encode a ____________

-Host cells cannot read RNA to make more RNA

+ss RNA

 (+/-) ssRNA can be translated as mRNA to make viral

proteins, therefore it can be infectious

-ss RNA

(+/-) ssRNA and retrovirus genomes must be replicated to be able to be translated

small

(small/large) viruses use host cell DNA polymerase

and other enzymes.

large

(large/small) viruses encode many of the enzymes required (e.g. DNA polymerase) and are more “autonomous”

pox- and herpes-

2 examples of large viruses that encode many of their own enzymes and are more autonomous

ribosomes

All viruses make proteins with host __________

cytoplasm

For eukaryotic virus life cycles: Translation occurs in __________

RNA genomes- encode their own RNA-dependent RNA polymerase, which uses a complementary RNA as template (+ -> – or – -> +)

RNA polymerase

RNA genomes from viruses encode their own ______________ which later on uses one strand to code the other(+ → - or - →+)