Block 3 virology Q1 Flashcards
(+)ssRNA Replication process (Host whores) (+)—>(-)—>(+)
The virion translates its RNA into mRNA via the host’s RNA-dependent RNA polymerase —> It then uses a (+) sense template to make (-) sense intermediates via RDRP —> from the intermediate (-) sense it makes both (+) sense & mRNA, which it translates to make proteins —> the proteins, mRNA, & (+) sense RNA are them assembled into mature viruses
(-)ssRNA Replication process (Build-a-bitch) (-)–>(+)—>(-)
The virion uses the RDRP in its cores cytoplasm for primary transcription of (-)sense RNA to make mRNA, (+)sense RNA, & the replicative complex —> It translates its mRNAs to accumulate products (virion proteins etc) —> the virion proteins interact with the replicative complex to cause it to make more full-length (+)sense RNA intermediates (therefore more genomic/parental (-)sense RNA) —> Secondary transcription happens with the progeny (-)sense RNA (then translation and accumulation of products i.e structural proteins)—-> Finally the nucleocapsid is assembled and matured, as it buds through the host cell’s membrane it will acquire its viral envelope
viroids
“VaNS”
unencapsulated (Naked) ssRNA viruses (these replicate and usually only cause plant diseases (except Hep D)
Icosahedral vs. Helical shaped viruses
Icos= Can either be naked or enveloped (easy to kill)
Heli = Always enveloped
Prion viruses
Only made of infectious proteins, these cause slow diseases, transmissible spongiform (CJD) encephalopathies
Susceptible = UV light, NaOH, Autoclaving, Hypochlorite
Resistant = Formaldehyde & nucleases
DNA vs RNA viruses
It’s either one or the other, not both!
DNA = has an Owls eye appearance (intranuclear inclusions) & they’re usually dsDNA
RNA= has cytoplasmic inclusions & are usually ssRNA (except retroviruses)
Steps of the typical infectious cycle
“Apply Pressure Under The Right ARmpit”
Attachment
Penetration
Uncoating
Transcription (-ssRNA) &/or Translation ((+/-)ssRNA)
Replication
Assembly
Release
Eclipse (prep-load) vs Exponential growth period (fire)
Eclipse= ~1-20hrs; it’s from when the virus attaches a host cell and can’t infect other cells (viral load appears to be 0 on a chart)
- Initial entry + disassembly of the parental virus —> assembly of the first progeny active synthesis ( aka from Attachment —> Assembly)
EXP= ~8-72 hrs. This is when the number of assembled progeny viruses increases exponentially over a period of time & then reaches a plateau (with no other increase in viral load)(can give 100-10,000 virions per cell!!!
Viral receptors on host cells & their viruses
“I Pee CHAtteRing with EVery CREep in the HoTtub”
ICAM
CD4
Ach
EGF
CR2/CD21
HVEM
Sialic acid
ICAM = intracellular adhesion i.e polio
CD4 = lymphocyte marker (helper) i.e HIV
Ach = neurotransmitter i.e rabies
EGF = growth factor i.e vaccina
CR2/CD1 = complement factor i.e Epstein-Barr
HVEM = TNF-family i.e herpes
Sialic acid = a part of the extracellular glycoproteins i.e Influenza, corona, & reovirus
Reveptor-mediated fusion of an enveloped virus: envelope fusion vs endocytotic entry
Envelope fusion:
The virion attaches to the host cell via its receptors, then the viral and host cell’s envelopes fuse to bring in the nucleocapsid, and the viral envelope forms a patch on the host’s membrane
Endocytotic entry:
The virion attaches to the host cell and forms a clathrin-coated endocytotic vesicle via virion-receptor interactions, it’s amplified, and the nucleocapsid is released inside the host cell
Forming a viral envelope (Budding)
Glycoproteins are made in the ER and glycosylation begins—>
The glycoproteins are moved in a vesicle to the golgi to continue glycosylation until the viral glycoproteins are moved in a vesicle to the host’s cell membrane —->
From there, the viral glycoproteins bind to the host’s membrane and form a patch to wait until a nucleocapsid migrates to it to bud outside the host cell to be released as a free virion
Methods of transmission:
Respiratory “AIR”
Fecal-oral “FOE”
Blood-borne “HIgH”
Sexy times “Hump”
Animal or bugs “Rabid”
Resp = Influenza A & rhinovirus via aerosols, sensitive to drying, & closer contact means more infectiousness
F&O = Enteroviruses (i.e polio) they replicate in the gut
Blood-Borne = Hep B & HIV, via sharing needles (IV drug abuse)
Sex = HIV
Animals/bugs = rabies
Egg inoculation:
Chorioallantoic membrane innoculation “CHoPpeR”
Amniotic inoculation “AIM”
Yolk sac inoculation “YeaH”
Allantoic inoculation “All Her gAINs”
CMI = Herpes, Poxvirus, & Rous Sarcoma
AI = Mumps & Influenza
YSI = Herpes
AI = HIV, Avian Adenovirus, Influenza & Newcastle disease
Poliovirus
“polio ENTeRs FrOm the gut”
Properties (type, genome, transmission)
Disease
An Enterovirus with RNA genome that’s transmitted via the fecal-oral route
It infects the gut and can be excreted in poop & also enter the blood (viraemia). From there, it infects both non & neuronal tissues (paralysis)
It causes poliomyelitis (iron lung patients) & gastro illness
Influenza A virus
Properties (type, genome, transmission)
Disease
An Myxovirus that’s enveloped with a segmented RNA genome
Its got a wide infectious range from people to animals because of its extensive antigenic variation
It causes respiratory infections
Tumour causing viruses
Epstein-Barr “Eat BLeuberries”
HPV (Human papillomavirus) “HP the Basilisk’s Chamber”
HTLV-1 (Human T-cell leukemia virus)
Hep C “Hard Cider & Liquor”
EB = Burkitts Lymphoma
HPV = Benign warts & Cervical carcinoma
HTLV-1 = Leukemia
Hep C = Liver carcinoma
Tumour-causing virus infectious pathways
General
Exceptions
The virus infects a cell and integrates its own nucleic acid & DNA into the host’s genome. This way it can alter gene expression by either activating certain host genes or activating its own genes to promote uncontrolled replication and delay cell growth (aka tumour making 101)
Exceptions include:
Herpes = causes latent infection, but its own nucleic acid stays separate from the hosts’ genome
Retroviruses = have an RNA genome so they need to make a DNA copy of their genome to replicate
Treating & preventing viral infections
Antivirals, vaccines, & immunization
Adenoviruses
Properties (shape, genome, effects)
Types A-G
A
B “BARs are PerFeCt for Cold Henesy”
C “5 CARs CLATter”
D “DESK”
E “ Krusty Fucking EyEs”
F & G “Fucking GAG”
Testing for Adenoviruses
Using them as therapeutics
Shape = icosahedral, NAKED, dsDNA its capsid has:
Fibre + penton –> These are host protein receptors that determine the virus’s tissue infectivity
Hexon –> This is the most abundant capsid protein, which is a target for the immune system
Genome = It has a big dsDNA (35kbp), and it encodes its own DNA pol and regulator factors so it can replicate in the nucleus (no lysing + immunity is long-lasting)
Causes =
- Hemagglutination (via the fibre capsid protein), so you can use the hemagglutination inhibition test
- It infects quiescent cells (non-dividing) to make them divide & its expressed proteins block the host’s immune system/ blocks cytokines (TNFa & interferons), and increases the viruses’ replication/transcription/& translation
Types:
A = Animals only
B = Acute respiratory disease, pharyngeal-conjunctival fever, & hemorrhagic cystitis
C = 5% of acute respiratory infections in children, which can persist as latent infections in the adenoids and tonsils
D = Episodic and sporadic kerato-conjunctivitis (pink eye)
E = Epidemic keratoconjunctivitis and fever
F & G = Acute gastroenteritis
Testing for adenoviruses:
Assessing high levels of neutralizing antibody titer
&
ELISA (poop analysis)
Adenoviruses as therapeutic agents:
- Used as antigen vectors (aka a gene delivery system via replacing deficient genes (Feline immunodeficiency virus), promoting cytotoxicity & amelioration of the disease (reducing its severity i.e. pseudorabies virus)
Parvovirus B19
“parvovirus is INSiDe Dusty ACs & EIther Enters From HarmFul air”
Properties (shape, genome, transmission, & effects)
Associated conditions
treat
An Icosahedral shaped naked virus that has ssDNA and infects humans
Trans = via airborne droplets to close contacts
Infects = It establishes infection in erythroid cells (adults’ bone marrow & Infants’ liver)
Causes =
- Febrile illness (in blood recipients)
- Aplastic crisis (patients with hemolytic anemia)
- Erythema infectiosum (aka 5th disease in healthy people)
- Hydrops fetalis (congenital infection)
Ass. with conditions =
- Encephalitis
- Neuropathies
- Myocarditis
- Nephritis
- SLE (sys. Lupus erythematosus)
- Henoch-Schonlein purpura (purpura, arthritis, & abdominal pain)
- Rheumatoid arthritis
Treatment =
- *Mainly supportive care
- fever use acetaminophen or ibuprofen
- Itching use a topical anesthetic or antihistamine
- Chronic parvovirus infection, use IV Immunoglobulins (IVIG)
- Aplastic crisis use packed RBC transfusions
Erythema Infectiosum aka 5th virus (inf agent is the Parvovirus B19)
Features (IP, Phases)
IP ~ 7-10 days
Phase 1 (peak virus levels and RBC destruction)
- Fever, malaise, myalgia, chills, & bright red rashes (raised slapped cheek app)
Phase 2 (Rash & arthralgia)
- Virus disappears (not infectious anymore)
- Erythematous maculopapular rash on the arms and trunk (lace-like app) due to the immune complexes in the capillaries of the skin
Phase 3
- Frequent reoccurrence & clearance, triggered via exercise, irritation, heat, & Sun)
Aplastic crisis (inf agent is the Parvovirus B19)
Effects on anemic, healthy, & thrombocytopenic patients
anemic patients = causes symptoms by destroying RBCs (pallor, fatigue, reduced hemoglobin)
Thrombocytopenic patients = Bruising & hydrops fetalis
Hydropis fetalis
Associated virus
Treatment/prophylaxis
Test
Ass. virus = associated with a maternal or fetal infection of the B19 parvovirus
Treat/pro = Preggos exposed to B19 should get IgG & M serology done (then repeated in 3 weeks)
Test = If IgMs develop, then there’s an acute infection
Polyomavirus-papovaridae
Human infections
JCV
“Dumb JOCK Missed the Pass”
BKV
“Bad Kidneys don’t Vent Harsh Chemicals”
MCV
Epi/Pathogenesis
Lab diagnosis & treatment
JCV = associated with progressive multifocal leuko-encephalopathy, a rare & fatal disease that causes demyelination. It usually impacts AIDs patients
Features= JCV reactivates & infects the CNS (via the blood), causing cytocidal infection in oligodendrocytes leading to demyelination
Sympt progression =
- Early: impaired speech & mental capacity
- Later (fast): Paralysis & lost motor capacity
- Death: 3-6 months after symptom onset
BKV = Hemorrhagic cystitis in AIDs & nephropathic patients
Features = Urine shedding is super prevalent (more than viremia, it’s 10 times higher than shedding is serum)
Tests=
- Serology (seroprevalence is nearly ubiquitous)
- Infected renal tubular cells (decoy cells) deteriorate too fast (urine microscopy is limited)
Test = Steroids don’t work; use antivirals (cidofovir)
MCV = Associated with Merkle cell carcinoma, a rare & aggressive form of skin cancer
Epi/Patho =
JCV & BKV: transmitted via droplets via the resp or urine. Patients are typically infected in childhood, and normally, antibodies are made.
&
The infection spreads from resp + urine to the kidneys, where they can lay dormant in the tubular epi of healthy people
Lab Diag & Treat =
BKV: DNA hybridization in urine
JCV: In PM, lesions in brain tissue
No antiviral treatment or vaccines (cause it’s generally asymptomatic)
HPV (Human papilloma virus)
“HPV DOEsn’t ChAnGE a Patient’s Wacky BP”
Properties (genome, transmission, & effects)
Pathogenesis
Other strains
Lab diagnosis
treat
HPV is a DNA virus that establishes infection in the e keratinocytes (skin) and mucus membrane
Normally it’s subclinical
But if its clinical symptoms include = Benign papilloma, warts (verrucae) or squamous cell papilloma
Patho=
- Transmitted via abrasions; the virus initially attaches to integrin and laminin receptors —>
The virus is then endocytosed, and its genome is incorporated into the host DNA —>
The infection is limited to the basal cells of the striated epithelium (cells can differentiate in the upper layers) & the virus only infects epithelial cells (NOT LIVE TISSUE!)—>
Non-cytolytic inf (virus particles are released after they degrade, desquamating cells
Lab Diagnosis:
- Papanicolaou staining (shows koilocytes aka cells with many structural changes i.e nuclear enlargement, irregular nuclear membrane, hyperchromasia (darker stain), & perinuclear halo)
- Viral oncogenes/oncoproteins E6 & E7 inactivate tumor suppressor genes p-53 & pRb
Other strains=
- HPV 16&18: Cancer (cervix, vulva, vagina, penis, anus, & oropharynx
- Sexually transmitted strains= condylomata, acuminate, &/or venereal warts
Treat/prevent= vaccines
- Gardasil (Merck)
- Cervarix (GlaxoSmithkline)
Both protect against initial infection of HPV 16 & 18
Crops of vesicles in diff stages of development
VS
Crops of vesicles in the same stage
Chicken Pox
&
Small pox
Direction examination (lab diagnostics)
Antigen detection
Electron microscopy
Light microscopy
Viral genome detection
Ag = Immunofluorescence & ELISA
EM = Shows viral particle morphology
LM = Shows histological appearance of inclusion bodies
VGD = Hybridization & PCR (specific nucleic probes)
Indirect Examination (Lab techniques)
Cell culture “CHIC”
Eggs
Animals “DAD”
CC= Cytopathic effect (CPR), Haemabsorption, & immunofluorescence
Egg= Pocks on CAM, Haemagglutination, & Inclusion bodies
Animals = Disease or death
CMV retinitis AIDs
severely immunocompromised
Serology
detect rising titers of antibodies between the acute & convalescent stages of infection
OR
detecting IgM in the primary infection
Virus Isolation (lab diagnostics) cell cultures used
Primary cells
Semi-continuous cells
Continuous cells
P = Monkey kidney
SC = Human embryonic kidney & skin fibroblasts
C =
- A549 (Human lung cancer cell for respiratory viruses)
- HeLa (epithelial cell from cervical cancer cell line)
- HL-60 (Human leukemia cell line)
ID viruses cell
Cell cultures
Neutralization test
CC =
- cytopathic effect (Ballooning cells or syncytia formation can be specific or non-specific)
- Haemadsorption (cells get the ability to stick to mammalian RBCs)
Neutralization= lowering virus infectivity by mixing it with specific antibodies
Electron microscopy (Lab diagnostics)
“CANARy poop”
“VHV”
“SCHMuk”
Need 10^6 virus particles to visualize species
poop = Rotavirus, adenovirus, Norwalk-like viruses, astrovirus, & calicivirus
Vesicle fluid = HSV & VZV
Skin = Papillomavirus, orf Molluscum contagiosum
Serology (Lab Diagnostics)
Criteria for diagnosing a primary infection
Criteria for diagnosing reinfection
Criteria for primary infection:
- A 4-fold or more increase in IgG titre OR the total antibody count between acute & convalescent sera
- IgMs present
- Seroconversion, A single high titre of IgG (or the total antibody) this is VERY UNRELIABLE
Criteria for reoccurring infections;
- A fold or more increase in IgG titre (or total antibody count between acute and convalescent sera)
- The absence or slight increase in IgM
Western blot (proteins)
Lane 1
Lane 2
Sample A
Sample B
Sample C
L1 = +
L2 = -
A = -
B = Intermediate
C = +
Serology uses (Lab Diagnostics)
HIV & Rabies
Rubella & Hep A
Resp & diarrheal disease
HIV/Rabies = serology isn’t useful cause the symptoms can appear months-yrs after the seroconversion
Rubella & Hep A = Serology IS USEFUL because the symptoms coincide with antibody production (more IgG&M = active disease)
Resp/diarrheal disease= serology is retrospective & not useful because symptoms appear before antibodies are made
Negri bodies appear in which virus?
Rabies
Owl eye inclusion bodies indicate what infection in the lung
CMV infection
General patterns of infection
Acute “AIRR”
Persistent “PLC”
Latent (reactivating) “LHS”
Slow virus infection “My HIVe”
Acute = Rhinovirus, Rotavirus, & influenza
Persistent = Lymphocytic choriomeningitis inf
Latent = Herpes simplex virus
Slow = Measles & HIV
Major Roles of Immunity in Viral Defence
CMI vs. Humoral
CMI = Clearing the virus
Humoral = Protects against reinfection
Mechanisms of viral persistence
“persist in AIR & Dust”
-Antigenic variation
- Immune tolerance (causes a reduced response to antigens, maybe due to pre-natal inf, molecular mimicry, & genetic factors)
- Restricted gene expression
- Down-regulation of MHC I expression (can’t recognize infected cells, i.e. adenoviruses)
- Down-regulation of accessory molecules (less immune recognition, i.e LFA-3 & ICAM-1 receptors by EBV)
- Infected immunoprivilaged sites (i.e HSV in sensory ganglia in the CNS, aka dermatomes)
- Direct infection of cells and the immune system (i.e Herpes, Retroviruses like HIV these usually lead to AIDs)
Cytopathological effects (viral lytic infections)
These infections cause cytopathic effects (major structural changes) like inclusion bodies:
- Virions in the nucleus (adenovirus)
- Virions in the cytoplasm
i.e. rhabdovirus, there are negri
bodies = RABIES
Hemadsorption
Infected cells with an enveloped virus containing hemagglutinin
The virus inserts hemagglutinins in the host’s cell membrane, so when it absorbs RBCs in modified areas of the membrane, it fuels the maturation of progeny viruses
Hemagglutinin tests will show RBCs specifically binding to the infected cells
Describe the right graph for proteins
Baltimore classification
DNA viruses
RNA viruses
Reverse transcribing viruses
DNA = ds & ss (+/-)
RNA = ds (+/-), ss(+), & ss(-)
RTV = ssRNA(+) & ssRNA(-)
