Schein - Intro To Viruses Flashcards
Virus properties
They are small obligate intracellular parasites that have nucleic acid and protein. They may or may not have an envelope and they may or may not have spikes.
Virion structure
Core: Made up of one type of nucleic acid and a protein capsid
Envelope: lipid bilayer that is host derived and usually has glycoprotein spikes coming out of it.
Properties to help classify viruses
Does it have DNA or RNA? Single or double stranded? Is the SS RNA + or - strand? Is the nucleocapsid icosohedral, helical, or complex? Is the virion naked or enveloped?
What does it mean to be a + strand and a - strand?
If it is a + strand then the message is sense and therefore when it meets up with the host ribosome it can just be translated into protein.
If it is a - strand then it has to be encoded into a + strand before proteins can be made.
Protomer and Capsomere
Protomer is a protein subunit
Capsomere is made up of protomers
- they make up the icosohedral capsid
What’s the deal with the glycoprotein spikes?
They are antigenic. So, if w have antibodies that bind to them it usually opsonizes them and thus neutralize them. These same spikes also bind to our cell receptors to create havoc. But not all cells have the specific receptors that the viruses can act on.
Steps in virus replication
Adsorption Entry Synthesis of proteins which make the girl RNA or DNA Replication of genome Synthesis of the structural proteins Packaging of the genome Acquisition of envelope if necessary Release of virus from the cell
How does adsorption occur?
Through attachment of the glycoprotein spikes
How does entry occur?
Virus can get into cell in many different ways.
- endocytic route is clathrin mediated
- non-endocytic route allows for fusion at the cell surface
Effects of viruses on cells
No apparent effect
Kill. Host cells
Fuse infected cells
Transform. Cells
Virus detection
Viral Antigens
Serology
PCR
Plaque assay
Plaque assay
Basically you have test tubes with various dilutions of viruses. You take a sample from each test tube and put it on an agar with a monolayer of mammalian cells. At higher concentrations you will see full clearing of the plate because the virus is killing everything but as the concentration of virus gets lower you will see only clearing spots so you can count t he colonies.
Virus neutralization assay
You have a known amount of virus in a test tube. You then add different dilutions of the patients serum. The patients serum has antibodies in it so they will neutralize the virus. You then take the different tubes and plate them to see if there was a “Cytoplasmic effect (CPE)”. If there was no growth then there was a cytoplasmic effect of the virus but if there was growth then there was no cytoplasmic effect of the virus
Hemagluttination
- heme agglutination inhibition
SOme virus particles agglutinate RBCs by attaching to the receptors outside of RBCs.
- so, if they blood pellets then there was no virus in the serum.
- you can then add antibody to neutralize the virus and then the RBCs won’t get agglutinated and they will pellet again.
What are. Some ways viruses can be uncoated? Not such high yield.
Their coats can be shed at the plasma membrane
Their coats can be shed if the virus is engulfed in an endosome and then released, it can remain in the endosome.
Their coats can be shed as it enters the nucleus.
