Viral Pathogenesis I

Question 1

Virion Structure

Answer 1

All viruses have capsids, but not all viruses have an envelope
Can be additional proteins such as matrix proteins present sometimes
DNA or RNA contained between capsid or envelop

Alcohol swipes, soap, etc is good at eliminating envelops and killing viruses
Naked viruses: this is not the case and harder to inactivate them

Question 2

Genetic Material: DNA

Answer 2

Double stranded DNA held together by disulfide and hydrogen bonds; can be circular or linear
Single stranded DNA

Many of the anti-virals target viral replication, and this depends on type of structure of DNA/RNA

Question 3

Genetic Material: RNA

Answer 3

Single stranded: has uracil instead of thymidine
Can have double stranded RNA
Unique challenges because must come up with new strategies to replication because normal human cells do not make copies of RNA

Question 4

mRNA from DNA

Answer 4

Viruses use host ribosomes to translate new viral proteins
All viruses, regardless of the type of genetic material, must generate mRNA.

Virus with double stranded DNA – very easy to use host machinery because this is what cells do

RNA polymerase recognize DNA and make copy of DNA template strand
mRNA: complimentary to DNA template strand, and then recognized by ribosomes and translated into proteins

Viruses with DNA genome: can use this strategy

Question 5

Viral Replication Cycle

Answer 5

Attachment: once attached to cell, it undergoes conformational change to get in

Entry, uncoating: endocytosis (enveloped or naked) or membrane fusion (enveloped only)

Genome expression and genome replication: virus opens endocytic vesicle to release genetic information, which undergoes transcription into mRNA and copied into new genetic information with new proteins made as well

Assembly: components of new genetic material and proteins come together to make new viral particles

Maturation and egress: viruses can lyse the cells by breaking the plasma membrane and released into extracellular environment
Enveloped viruses not only lyse the cell, but take part of the cytoplasmic membrane with them via budding

Question 6

Assembly of Capsids

Answer 6

Assembly and release process
Herpes simplex virus
Capsid formation in nucleus of cell with immature capsid with DNA
Proteins that help capsid come together via scaffolding
Nucleus of cell is where virus is assembled
Transcription = nucleus
Translation = cytoplasm

Question 7

Plus Sense vs. Minus Sense

Answer 7

Plus sense: ultimately wants to make more plus sense; only way to do this is make complimentary strand via minus strand to serve as template and cannot directly replicate, but directly translate
Viruses: are intracellular

Plus sense is analogous to the CODING strand and must be converted to minus sense in order to have a template to make copies from but the copies made/output are plus sense
Minus sense is already the TEMPLATE strand, thus the copies are directly made from this template, and the output/copies are plus sense

Viruses: are intracellular; most effective way to kill a virus is to stop the replication or “factory” analogy