Virology Exam 1 Flashcards
List the characteristics used to describe viruses
small, 20-300 nm, filterable
simple
obligate intracellular parasites
infectious
include important pathogens
what are some important milestones in veterinary virology
smallpox vx
transmission & vx rabies
filterability of foot/mouth dx
isolated swine flu influenza virus
electron microscopy of virus/TMV
cell culture system & poliovirus
ectromelia pathogenesis
rinderpest vx & eradication
co-evolution of virus & host
first recombinant DNA virus
identification of avian bornavirus by gene microarray method
identification of Theiler’s dx associated virus by mass sequencing method
3 types of virsuses
iscosahedral
helical
complex structure
enveloped viruses
lipoprotein outercoving of virions of some viruses, derived from cell membranes
easier to eliminate
DNA and RNA genomes
non-enveloped viruses
no lipoprotein outer covering
harder to eliminate/resistant
DNA and RNA genomes
helical viruses
enveloped RNA genome (e.g. Rhabdoviridae aka rabies)
define virion
complete virus particle
define capsid
protein shell that surrounds viral nucleic acid, protects viral genome from destructive agents, introduction of viral genome into host cells
define nucleocapsid
capsid + nucleic acid
define capsomers
cluster of proteins on capsid that make up one morphologic unit seen by e- microscopy
list the steps of viral replication
- attachment
- penetration & uncoating
- transcription
- translation
- replication
- assembly of virions & release
what protein is important for the attachment step of a virus to cell receptor
viral attachment protein (VAP)
describe DNA viruses
dsDNA or ssDNA with linear or circular DNA
low mutation rates
DNA polymerase
more durable
degraded by DNAases & heat
DNA viral inclusions are present in nucleus
describe RNA viruses
dsRNA or +, -, or ambisense (both +,-) ssRNA
higher mutation rates
degraded by RNAases, heat, formaldehyde, UV light
RNA viral inclusions present in cytoplasm
virus’s routes of transmission
skin, conjunctiva, oral cavity, respiratory tract, GI tract, urogenital tract
virus’s mechanisms of spread
viruses restricted to epithelia
subepithelial invasion, lymphatic spread
viremia
infection of other organs
virus’s mechanisms of spread
viruses restricted to epithelia
subepithelial invasion, lymphatic spread
viremia
infection of other organs
what factors restrict viruses to epithelia
specific cell receptors
temperature aspects of replications
topography of viral budding
polarization of epithelial cells
virus dependence on host cell machinery
topography of virus maturation
protected from specific host defenses
what organs are more commonly affected by secondary viremia
nasal/oral mucous membranes
brain
skin
lungs
kidney
what organs are more commonly affected by primary viremia
liver and spleen
define a cell-free virus
virus doesn’t utilize immune cells
define a cell-associated virus
virus utilizes macrophages, lymphocytes, platelets, RBC to evade immune response and infect host
innate immunity for viruses
-anatomic
-physiologic
-cells
-mechanisms
anatomic: skin, mucosa, ciliary apparatus
physiologic: lysozymes, gastric acid, bile, digestive enzymes
cells: dendritic cells, macrophages, NK cells
mechansims: interferons, cytokines, complement
type I IFN-alpha
leukocytes
antiviral
type I IFN-beta
fibroblasts epithelium
antiviral
type II IFN - gamma
T cells, NK cells
immunoregulatory
what do IFN cause
flu-like symptoms - fever, chills, nausea, malaise
four classic signs of inflammation
redness, pain, heat, swelling
acquired immunity
neutrophils, eosinophils, macrophages, lymphocytes
T cells, B cells, NK cells
Antibodies (IgG, M, A)
passive transfer
antibody functions
neutralization
opsonization
antibody-dependent cell-mediated cytotoxicity
complement activation
MHC I
CD8+ (CTL)
endogenous
MHC II
CD4+ (T helper and suppressor/reg)
exogenous
what do viral infections and modified live vaccines stimulate?
B cells (antibodies)
CTL’s
what do inactivated/killed viral vaccines and subunit vx stimulate?
B cell & T helper cell activity (cytokines)
what can be measured by serological testing?
parenteral inoculation (IV,IM,SQ) with viral vaccines due to systemic immunity
e.g. parvovirus
how are viruses shed
respiratory and oropharyngeal secretions
feces
urine
skin
milk
blood
genital secretions
type I hypersensitivity
anaphylaxis
IgE
type II hypersensitivity
cytotoxic
IgM/IgG
type III hypersensitivity
immune complex
IgG
type IV hypersensitivity
cell-mediated, delayed hypersensitivity
CTLs
autoimmunity
immune response directed against normal host components
primarily cell-mediated or humoral
vx-induced suspected cases
broad & directed against many organs or can be organ/antigen specific
how do viruses induce autoimmune dx
exposure of hidden antigens
molecular mimicry
failure of regulatory control of immune response
virus’s mechanisms of spread
viruses restricted to epithelia
subepithelial invasion, lymphatic spread
viremia
infection of other organs
how does a virus spread from blood –> tissues
fenestrated/inflamed capillaries
transcytosis by endothelial cells
replication in endothelial cells
trafficking of infected lymphocytes & monocytes
how do viruses invade the respiratory tract
aerosolized virus or self-inoculation of mucous membranes
replication in resp epithelium
level of tract dependent on size, temp, immunity
how do viruses invade intestinal tract
ingestion or viremia
replicated in intestinal epithelium
how do viruses invade the CNS
replication in blood vessels of meninges, choroid plexus, brain, spinal cord
transported across blood vessels via infected leukocytes
by CSF or neurons
what happens if viruses invade the fetus
fetal death, abortion, stillbirth
congenital defects
immunotolerant carrier state
inapparent carrier state
what other organs can viruses invade
liver, testis, pancreas, synovial cells
what are dead-end organisms
provide an example
organs that cannot shed a virus
e.g. brain
what are the two components of viral dx
- effects of viral replication on host
- effects of host response on virus & host
describe why vaccines are used
- stimulate a protective immune response (immunological memory)
- establish herd immunity
Modified Live Vx
Pros
Pros
- best immune response, esp. cell-mediated
-few inoculations
-stimulates mucosal immunity IgA
-no adjuvants
-decreases change of hypersensitivity rxn
-induce IFN
-inexpensive
Modified Live Vx
Cons
-risk of reversion to virulence
-cold storage
-inactivated by UV, heat, disinfectants
-contaminants
-cannot give to pregnant animals
-immune enhancement
Inactivated Vx
Pros
stable in storage
unlikely to cause disease
unlikely to contain viable, contaminating organisms
cost effective
Inactivated Vx
Cons
multiple doses
poor CMI response
large amounts of Ag
problems with disease if there is failure to completely inactivate virus
exacerbated diseases
adjuvants
vx induced tumors or grandulomas
immune disorders
subunit vs
pros/cons
PROS
-specific & safe
CONS
-similar to inactivated vx
mRNA vx
pros/cons
pros
-advanced technology
cons
-newer
dna vx
pros/cons
PROS
-easy to administer
-expression of genes for 60 days
- pure, stable
-low cost
-no interference by maternal Ab
CONS
-insertional mutagenesis & oncogenesis
synthetic peptide vx
pros/cons
pros
-safe, non-toxic, stable
cons
-expensive
-poorly immunogenic
virus vector vx
pros/cons
pros
-safe
-easy to administer
-reduced replication due to gene introduction
cons
-possible disease due to vector itself
-reduced replication of the vector in unnatural host
successful use of vaccines
lack of reservoir
long duration of immunity
lack of antigenic variation
safe efficacious vx
ease of administration
acceptability to client
cost-effective
appropriate storage and administer of vx
vaccine failures
animal already infected
wrong virus used
non-protective antigens used
animal doesn’t respond to vx
incorrect administration
adverse rxns
sensitivity equation
a/a+c = true +/total diseased
positive, possess disease
specificity equation
d/b+d= total -/total non-diseased
negative, non-diseased
inherent variability
variation can be caused by variation in animal subjects & reading of results by those reading them
virus isolation (VI)
identification of unknown agents,
detects live virus (antigen)
direct fluorescent antibody (FA)
fluorescent Ab detects antigen
indirect FA
detects antigen using 2 Ab
hemagglutination Inhibition (HI)
detects parvo & influenza - two important viruses that agglutinate RBC
Ab present “button” (HI)
Ab not present “lattice” (HA)
polymerase chain reaction (PCR)
detects viral nucleic acids
agar gel immunodiffusion (AGID)
detects antibody
enzyme linked immunosorbent assay (ELISA) SEROLOGY
detects antibody
titers
2-fold serial dilution of serum
detects antibody
positive predictive value equation
a/a+b
negative predictive vale equation
d/c+d
prevalence _____ PPV and _____ NPV
increases PPV
decreases NPV
components of validity
sensitivity
specificity
PPV
NPV
screening test significance
sensitivity
fast, cheap
diagnostic test significance
specificity
confirm clinically diseased animals
qualities of a test
1.
2.
- precision
- validity
best scenario test results
valid but not precise
valid and precise
increasing sensitivity increases the likilhood of _________
false positives
increasing specificity increases the likilhood of _________
false negatives
components of virsuses
proteins & glycoproteins
nucleic acids (DNA/RNA)
lipids - envelope
difference between structural proteins & non-structural proteins
structural: make up virion, protect genome, VAP for tropism, Ag that induce neutralizing Ab, CTL and Th cells, enzymes/regulatory proteins
non-structural: encoded by viral genome and expressed in infected cells, not part of virion, replication functions, host-interaction functions
viral genome types
monopartite
multiparttite/segmented (can do reassortment)
diploid
