how does a virus "know" which cell to infect?

[THEnamesSARA]

ah im not suure. is it through the marker protein?

[Dak]

Sort of. Viruses generally have a molecule on their cell surface that is responcable for fusing the membrane of the virion and the cell, thus injecting the virion into the cell. The fusion molecule is usually designed so that it will only activate upon reacting with a certain molecule on the target cell's membrane.

 

For example, HIV has a molecule called gp120 on it's surface; gp120 reacts with molecules called CD4 and either CXCR5 or CCR3, meaning that HIV infects helper-t-cells and macrophages (helper-t-cells and macrophages being the cells that have CD4 and either CXCR5 or CCR3 on their surface).

[mattbimbo]

Dak

Viruses generally have a molecule on their cell surface

 

viruses do not have a cell surface!

 

Dak

for fusing the membrane of the virion

 

you probably mean the lipid envelope of the virion/capsid! but not all viruses have lipid envelopes.

 

Dak

thus injecting the virion into the cell.

 

not all viruses are injected. HIV for instance. in fact i don't know of one viruses that infects mammals which are injected into cells.

[sabbath]

viruses do not have a cell surface!

 

 

 

you probably mean the lipid envelope of the virion/capsid! but not all viruses have lipid envelopes.

 

 

 

not all viruses are injected. HIV for instance. in fact i don't know of one viruses that infects mammals which are injected into cells.

 

viruses are not injected themselves. only the viral RNA is. which uses the cell as a replicating factory.

[mattbimbo]

sabbath

viruses are not injected themselves. only the viral RNA is.

 

you are right that it is the genes, DNA or RNA, which are injected.

but i believe the injection systems of which you are think are mostly, if not entirely, confined to bacteriophages.

 

many eukaryotic viruses, enter cells through receptor-mediated endocytosis, where they are tranpsorted to intracellular compartments, where the viruses uncoat themselves to release their genetic material, etc. eukaryotic cells are more complicated than bacteria. so simply injecting genes into the cytoplasm of eukaryotes would not stimulate their replication because the enzymes don't exist for it. in prokaryotes this is of course difference, where polymerases exist in the cytoplasm.

[Dak]

viruses do not have a cell surface!

 

quite a few viruses yoink cell surface off of the cell that creates them.

 

HIV, for example, is covered by cell-surface membrane from helper-t-cells or macrophages, with the addition of gp120 which it forses the cells to manufacture and plonk onto their membrane prior to budding.

 

you probably mean the lipid envelope of the virion/capsid! but not all viruses have lipid envelopes.

 

Yes indeed, that is what i meant. and tbh i was under the impression that all non-bacteriophage viruses had a cell membrane/lipid envelope (not saying im right, just saying i was unaware of any virions that dont steal host-membrane during budding).

 

 

not all viruses are injected. HIV for instance. in fact i don't know of one viruses that infects mammals which are injected into cells.

 

if my terminology was off, you can blame southern confort

 

I meant the capsid being placed in the cytoplasm, but as mattbimbo said, it's not allways simple. viruses that have fusion molecules can 'inject' their capsid strait into the cytoplasm, those that enter via receptor-mediated endocytosis usually end up in lysosomes or the golgi apperatus (iirc) and have to 'break out' of there and enter the cytoplasm.

[YT2095]

forgive my over simplicity here but isn`t a Key/Lock type of thing?

 

the Virus can Only attatch to certain "receptors" perculiar to that particular cell type and position.

[CharonY]

Basically that is correct. In about any case I can think of the virus attaches to certain receptors. The mode in which the virus inserts genetic material varies though, as described above.

[mattbimbo]

DAK

just saying i was unaware of any virions that dont steal host-membrane during budding

they are called non-enveloped viruses, the particles are stable in the open, ie air and water, while enveloped virions are predominantly internal.

 

lock/key pretty much sums it up.

 

in an immune response, antibodies can bind to the virus particles thereby 1) inhibiting their uptake by the cells which the virus targets and 2) facilitating their uptake by immune cells such as macrophages. it can seem complex but it is just another variation on the lock/key interaction.

[scicop]

wow..you dudes are really geeking out here

[YT2095]

wow..you dudes are really geeking out here

 

and this presents a problem because..... ?