Module 10 Flashcards
2 types of RNA viruses
Positive and negative stranded
Which RNA virus strand can immediately be translated?
positive strand
Which RNA virus strand cannot be immediately translated?
negative strand
What enzyme is necessary for RNA viruses to transcribe a negative strand virus?
RNA-dependent RNA polymerase
What enzyme for RNA transcription do humans not possess?
RNA-dependent RNA polymerase
This RNA virus can incorporate into the host genome
retroviruses (like HIV)
This is the only virus group with a dsRNA genome
Reoviridae (like rotavirus)
What type of strand do most DNA viruses have?
both positive and negative strands
What makes parvoviruses an exception to DNA virus genome rules?
they’re ssDNA
2 types of viral capsids
icosahedral and helical
What type of viruses have helical symmetry
RNA viruses
Capsid shape of rhabdoviruses (like rabies)
bullet shaped
What type of viruses have icosahedral symmetry?
DNA viruses
How do viruses acquire a viral envelope
by budding through a host cell nuclear or cytoplasmic membrane and taking a piece with it
List the DNA viruses
think HHAPPPy: Hepadna, Herpes, Adeno, Papova, Parvo, Pox
List the RNA viruses
just think it’s everything except HHAPPPy
4 steps of viral replication
adsorption and penetration, uncoating of the virus, synthesis and assembly of viral products, and release of virions from the host cell by lysis or budding
passage of virion from surface of the cell across the cell membrane and into the cytoplasm
penetration
cell membrane invaginating that encloses a virion in an endocytic vesicle
receptor-mediated endocytosis
How do some enveloped viruses, like HIV, enter a host cell?
membrane fusion of the viral envelope with the host plasma membrane
stepwise process of disassembly of a virion that enables the expression of viral genes that carry out replication
uncoating
Where do viral DNA transcription and replication occur?
host cell nucleus
What form of mRNA codes for capsid structural proteins?
late mRNA
2 problems RNA viruses encounter
no host cell RNA polymerase to use and usually eukaryotic mRNA only produces one polypeptide
Type I RNA virus replication
ssRNA with + polarity that replicates via complementary (-) strand intermediate
Type II RNA virus replication
ssRNA with - polarity that replicates via a complementary (+) strand intermediate
Type III RNA virus replication
Viruses with a dsRNA genome- have to have RNA dependent RNA polymerase/transcriptase in order to transcribe
Type IV RNA virus replication
ssRNA of + polarity that is replicated by a DNA intermediate (uses reverse transcriptase, or RNA-dependent DNA polymerase)
Assembly of RNA viral nucleocapsids happens in the:
cytoplasm
Assembly of DNA viral nucleocapsids happens in the:
nucleus
Difference in release of naked virions vs enveloped virions
naked are exocytosed and enveloped virions bud out
4 possible outcomes from viral infection in a cell
non permissive (virus can’t replicate or cell dies too fast), permissive (virus replicates but doesn’t do anything), latent viral state, host cell death and viral release through lytic cycle
viral family that includes all influenza viruses
orthomyxoviridae
viral family that includes mumps, measles, RSV, and parainfluenza
paramyxoviridae
Flu symptoms that differentiate it from a cold or other viral infection
muscle aches, high fever, and headaches
structure of orthomyxoviridae virions
spherical, with 8 negative stranded RNA with a nucleocapsid with helical symmetry capsid
2 types of glycoprotein spikes on orthomyxoviridae
hemagglutinin activity (HA) and neuraminidase activity (NA)
What does hemagglutinin attach to?
sialic acid receptors on the surface of erythrocytes
What does neuraminidase do?
cleaves neuraminic acid and disrupts the mucin barrier, exposing sialic acid binding sites underneath it
What is critical for the release of newly formed virions from an infected host cell?
neuraminidase
What protein forms a proton channel and depends on host cell nuclear functions to be transcribed?
flu M2 protein
What type of influenza affects humans and animals?
Type A
small changes in HA or NA of influenza that make it slightly different
antigenic drift
When 2 influenza strains co-infect the same cell, what can happen?
RNA segments can be mispackaged into the wrong virus and makes a new viral serotype. Called Antigenic Shift
Trading of RNA segments between animal and human flu strains
antigenic shift
most common cause of human flu
H1N1
Oseltamivir, zanamivir, and peramivir are what kind of drugs?
antivirals to treat type A flu that are NA inhibitors
Serotype of bird flu
H5N1
Differences between paramyxoviridae and orthomyxoviridae structure
for para, NA and HA are on the same glycoprotein spike, not two separate ones
What protein of paramyxoviridae causes infected host cells to fuse into giant multinucleated cells?
fusion protein
What protein causes the formation of syncytial cells?
F-protein
What does RSV lack compared to other paramyxoviridae
lacks both HA and NA
What virus most frequently affects the parotid glad and testes?
mumps
What virus has a prodrome period?
measles
small red lesions with blue-white centers found in the mouth due to Measles infection
Koplik’s spots
rash that spreads across the entire body with high fever is characteristic of what virus?
measles
treatments for measles
post-exposure vaccination and immune serum globulin
Acute viral hepatitis types
HAV, HBV, HCV, and HDV
Chronic viral hepatitis types
HBC, HCV, and HDV
Hepatitis type with positive single stranded RNA
HAV
Diagnosis of hepatitis
IgM shows acute infection, igG shows old infection and protective abs
structure of HBV
hepadnavirus- DNA
big virus with enveloped capsid and circular dsDNA
marker for active HBV infection
HBeAg
methods of transmission of HBV
mother to baby, sexual, and parenteral
Severe acute hepatitis w rapid liver destruction
fulminant hepatitis
Disease states caused by HBV
acute, fulminant, and chronic
leading cause of chronic hepatitis
HCV
Which hepatitis form needs another hepatitis form in order to infect?
HDV
What does HDV need in order to infect?
HBV
3 main concepts of retroviridae
retro, grow, and blow
capsid proteins of HIV
p24, p17, p9 and p7
2 HIV lipid membrane proteins
gp120 and gp41
3 HIV viral proteins essential for replication
RT, protease, and integrase
Diagnostic tests for HDV infection
delta antigen and anti-HDV ab
Antibodies against HBsAg is protective against what?
HBV and HDV
Asymptomatic carriers of HBV never develop what antibodies?
anti-HBsAg
IgM anti-HBcAg is used to detect what?
new HBV infection
IgG anti-HBcAg is used to detect what?
old HBV infection
HbeAg is used to detect what?
High infectivity of HBV
anti-HBeAg is used to detect what?
low infectivity of HBV
Genome across all RNA retroviruses
2 LTRs, gag, pol, and env genes
Genes that flank whole viral genome
Long terminal repeat sequences (LTRs)
2 functions of retrovirus LTRs
Sticky ends (insert into host DNA) and promoter/enhancer (bind to LTRs and modify viral DNA transcription)
What does gp120 bind to on cell surface?
CD4 molecule on surface of T cells, macrophages, and microglia
What does gp41 do?
mediates fusion of the HIV viral envelope with the cell plasma membrane allowing viral contents to enter
What are CXCR4 (fusin) and CCR5 required for?
they’re cofactors required for HIV entry into T cells and macrophages
this HIV cofactor enhances the entry of T cell line-tropic HIV isolates
CXCR4 (fusin)
This HIV cofactor is specific for macrophage line-tropic HIV isolates
CCR5
Immune response where an infected person first exhibiting detectable levels of anti-HIV abs in their blood serum
seroconversion
Clinical significance of HIV infection
T-cell death, multinucleated giant T cells, hypergammaglobulinemia from B lymphocytes, monocytes and macrophages span BBB
Individuals infected with HIV but show no signs of disease progression for 12+ years
long term non progressors
individuals repeatedly exposed to HIV but never become infected
highly exposed persistently seronegatives
Therapies under HAART
AZT, non-nucleoside RT inhibitors (NNRTIs), protease inhibitors
Transmission route of Ebola
person-to-person contact
What does SARS-CoV-2 bind to?
ACE2 receptors
