Virology I - Mclean Flashcards
Nonenveloped virus vs Enveloped virus
Where is protein envelope from?
Nonenveloped virus only contains a capsid and nucleic acid.
Enveloped virus contains these and also an envelope, which consists of proteins in envelope membrane. This is from the HOST CELL
how to get protein from ssRNA.
ssRNA -> + polarity / strand -> mRNA sense -> protein synthesis
ssRNA -> - polarity / strand -> anti mRNA sense
if its -, you have to convert it to + to get protein.
protomer vs capsomere.
helical vs icosahedral
protomer is a monomer of a capsomere.
protomer = single polypeptide type. Helical made of protomers
capsomere = group of protomers. Icosahedral made of capsomeres.
One-step growth curve
eclipse period
exponential growth.
1 virus infects cell. You have eclipse period, where virus disassembles. You then have reassembly, and this is where eclipse period ends.
eclipse period: time from initial entry to assembly of first progeny virion. VIRUS = NONINFECTIOUS
exponential growth: rapid progeny production after eclipse period.
Steps in Replication Cycle:
Step 1: Adhere. (stick to) Binds to surface of cells via normal receptors
2.) Penetrate
3.) Uncoat (take out nucleic acid)
4.) Replication of viral genome
5.) Assembly, release of viral genome.
2 principal mechanisms of penetration:
Receptor-mediated endocytosis. (invagination of membrane)
Membrane fusion. (Envelope virus). Membranes fuse from both host cell / virus
Location of Viral genome in cell:
Most DNA viruses tend to replicate in the nucleus.
Most RNA viruses tend to replicate in the cytoplasm or cytosol.
Replication of Viral Genome:
DNA virus replication mechanism
Parental DNA -> Early mRNA -> Early Proteins.
Early Protieins -> replication of virus. Makes progeny DNA.
Progeny DNA -> late mRNA -> Late proteins.
Early proteins play important role in replication.
Late Proteins play important role in assembly of nucleocapsids.
Replication of Viral Genome:
RNA virus replication mechanism
+ ssRNA -> Viral proteins.
Viral proteins include RNA-dependant RNA polymerase
which convert the + ssRNA to -ssRNA.
-ssRNA goes through another round from RNA-dependant RNA polymerase to make +ssRNA.
From -ssRNA, virus caries in a premade RNA-dependent RNA polymerase (enzyme) into the host so it can do this.
Release of progeny viruses
Enveloped vs naked:
Enveloped typically released via budding
Naked typically released via lysis
Episome:
Nucleic acid from virus hangs out separate from host cell, like a plasmid.
Response of a host cell to viral infection ranges from:
1.) Viral infections in which no progeny virus produced (nonpermissive cells) (nothing happens)
2.) Viral infections which host cell surface altered antigenically but not killed, progeny released (budding)
3.) Viral infections result in a latent viral state in host cell. Persistence of viral genome inside host genome, latent viruses. (fuse with DNA, example is HIV)
4.) Lysis
CCR 5 Delta 32:
Mutation CC, mutates receptor on cell that HIV normally binds to.
Retroviridae (HIV):
General Characteristics
skim
Lipid envelope
+ ssRNA
Linear RNA (2 identical copies)
Icosahedral capsid
3-9 genes
Genus of HIV:
Lentivirus
SIV and FIV are also lentiviruses
3 important genes for HIV
gag: Group Associated antiGens
pol: POLymerase (RNA-dependent DNA polymerase or reverse transcriptase), integrase, and protease
env: ENVelope glycoproteins (gp120 - surface protein attachment, gp41 - transmembrane protein)
Also has poly A tail which provides stability
One way to look for HIV:
(diagnosis)
Look for CA = Major capsid protein (p24)
HIV Cell Tropism (which cells do they like to infect?)
CD4 T cells.
Macrophages/Monocytes. Major reservoir cell
