virology - overview(general characteristics, viral taxonomy, viral replication, epidemiology ) Flashcards
study of viruses
virology
Importance of Studying Virology
Understanding viral evolution and behavior
Control of viral infections
Public health and global security
Economic impact in agricultural and livestock industries
factors under the “understandifng of viral evolution and behavior”
Predicting future outbreaks
developing effective countermeasures
“Understanding viral evolution and behavior”
How do we able to PREDICT FUTURE OUTBREAKS
by studying the evolution of viruses and their interactions with host, scientist can better anticipate and prepare for new viral threats
“Understanding viral evolution and behavior”
How do we able to DEVELOP EFFECTIVE COUNTERMEASURES
development of targeted and prevention strategies based on how they behave and evolve
Factors under the CONTROL OF VIRAL INFECTION
vaccine development
antiviral drug development
disease prevention and control
“CONTROL OF VIRAL INFECTION”
how vaccine development works?
virology research is essential for creating vaccines that protect against viral infection
“CONTROL OF VIRAL INFECTION”
how antiviral drug development works
by studying viral replication and structure scientist can develop drugs to inhibit viral growth
“CONTROL OF VIRAL INFECTION”
how disease prevention and control works
by understanding how viruses spread and cause disease is crucial for implementing effecting public health measures
factors under “PUBLIC HEALTH AND GLOBAL SECURITY”
pandemic preparedness
biosecurity
“PUBLIC HEALTH AND GLOBAL SECURITY”
how do we implement PANDEMIC PREPAREDNESS
by studying past pandemics helps us prepare for future outbreaks and develop response plans
“PUBLIC HEALTH AND GLOBAL SECURITY”
how BIOSECURITY works
by understanding viral threats for protecting against bioterrorism and accidental releases of dangerous viruses
factors under “EGONOMIC IMPACT”
agricultural and livestock industries
how agricultural and livestock are affected by viral infection
viruses can cause significant economic losses in agriculture and animal husbandry. Studying theses viruses helps develop prevention and control measures
example of viral infection in PH
ASF and Bird Flu wherein once infected, they will be depopulated
depopulated means
intentional killing of livestock to prevent spreading of infection
An infectious strict obligate intracellular parasite that comprises either DNA or RNA as its genetic material and often surrounded by a protein coat or membrane.
virus
can virus live without a host cell?
naur
can virus synthesize protein independently?
doesn’t synthesize protein independently
Smallest infectious agent
virus
how small the virus is?
20 nm to 300 nm
they can infect only certain types of cells or tissues
viral tropism
Zika virus size
0.045 um
nucleic acid of a virus
dna OR rna
nucleic acid of cell
BOTH dna and rna
Viruses have a FEW proteins that make up their _____ and ‘_____
outer coat and internal structure.
Cells have MANY proteins that perform various functions within the cell
true or false
true
SOME viruses have a lipid envelope, which is a layer of ______.
lipoprotein
Cells have a cell membrane, which is composed of a ___ and
___
phospholipid bilayer and proteins.
do Viruses have ribosomes
naur, they don’t
Cells have ribosomes, which are responsible for ___synthesis
protein
do Viruses have mitochondria
naur
Cells generally have mitochondria, which are the “______” of the cell and produce energy.
powerhouses
: Viruses may have a few enzymes, but they generally lack the enzymes necessary for
_____
independent replication
: Cells have many ___that catalyze various biochemical reactions.
enzymes
Viruses cannot replicate on their own. They must invade a host cell and use the host’s machinery to replicate.\
true or false
true
Cells can replicate independently through ______ (for prokaryotes) or _______ (for eukaryotes).
binary fission; mitosis
size of a Parvoviridae
22nm
size of Poxviridae
200-450 nm
varying shape of a virus
Sphere
Rod
Bullet
Brick
virus particles are called as
virions
anatomy of a virus where it contains the genome
nucleic acid
anatomy of a virus where it is the innermost part
nucleic acid
the formation of a nucleic acid of a virus
may be
LINEAR or CIRCULAR
anatomy of a virus
nucleic acid
capsid
envelope
a protein coat that surrounds the nucleic acid
capsid
it mediates attachment to host cell receptor
capsid
determines host specificity and organ specificity of virus - viral tropism
capsid
antibody binding site
capsid
Host specificity
Ex. Rabies Virus
it’s host specificity is ___
and the organ specificity is ____
acetylcholine receptor
liver
a term for nucleic acid and capsid is called as
nucleocapsid
a complete virus particle is called as
virion
the lipid that surround the capsid is called as
envelope
envelope has lipoprotein, t or f
t
responsible for viral entry of into the host through budding
envelope
susceptible to drying and destruction in the environment, they typically are transmitted via direct contact (respiratory, sexual, or parenteral contact )
envelope
If a virus has an envelope they are unstable to
Dryness
Heat/high temp
Detergents
Extreme pH
Liquid solvents
because enveloped viruses are very susceptible to drying and destruction in the environment, they typically are transmitted via
direct contact such as respiratory, sexual, or parenteral contact
this methods will prevent exposure to the environment and successful propagation of the viral agent to another susceptible host
inserted into viral envelope are viral proteins such as
hemagglutinin (HA), neuraminidase or glycoprotein spikes
a virus with no envelope is called as
Naked viruses
naked viruses
they are resistant to environmental factors. Because of their stability they are typically transmitted via ___
fecal-oral route
it is the middle portion of the nucleocapsid and envelope that may be enzymatic activities or biologic function related to infection, interaction with host cell proteins
matrix protein
spike-like projections on the surface of the envelope of some viruses which attach to the host cell receptor during viral replication
glycoprotein spikes
assist in the stabilization of attachment for the lipid envelope and for attachment to the host cell to facilitate viral entry
glycoprotein spikem
often referred or described the nucleic acid genome surrounded by a symmetric protein coat called capsid
nucleocapsid
function of nucleic acid genome
encodes the protein required for viral penetration, transmission, and replication.
this determines the mechanism for mechanism for viral replication
viral genome structure
viral capsids are made up of repeating structural subunits referred to as
capsomeres
they associate to form capsid and a characteristic of symmetrical structure
capsomeres
it connects the inside of the virus to the outside which helps the virus interact with the cell it wants to infect
matrix protein
3 capsid arrangement
icosahedral
helical
complex
helical and icosahedral is the most common capsid structure geometrically
nucleic acid arrangement
linear and circular
Arrangement of the capsid identifies the _____ of the virus
shape
Helical form of capsid of a virus means it’s nucleic acid is always
RNA
___-capsomeres arrange in cubical and 20 flat sides/triangles that form a symmetric figure
icosahedral
irregular shaped capsids usually assume what form or shape
helical form and spiral shaped
viruses that can cause disease in human ranges from approx ____
20-300nm
even the largest viruses, such as the poxvirus are cannot be detected by a light microscope because they are less than _____ the size of staphylococcal cell
<1/4
since viruses are can’t be detected by light microscope, what microscope is used in 1930s to visualized viruses
electron microscope
Based on the observations of ____, he concluded that all the virus has to make mRNA to effectively replicate no matter what the genome is made of
David Baltimore
an RNA needed by viruses to effectively replicate no matter what the genome is made of
mRNA
Based on the chemical nature of the viral genome, the need for mRNA synthesis, and the particular genome replication strategy used, viruses are grouped into _______ different classes
seven
baltimore classification
Ask these 3 questions
1.
2.
3.
- type of genetic material, is it DNA or rna
- number of strands; is it stranded or doubles stranded
- can they make their own mRNA
for simplicity, many texts limit the viral classification to 3 basic properties, what are these?
- viral morphology
- method of replication including genome organization whether if it’s rna or dna and single or double
- presence or absence of lipid envelope
this refers to the strategy of the virus to duplicate the viral genome
means of replication
according to bailey’s and scotts, viral taxonomy is determined by what agency
ICTV international commitee on taxonomy of viruses of microbiological societies.
viral taxonomy is divided into what categories
6 orders
87 families
19 subfamilies
348 genera
2290 species
baltimore classification
These viruses act like the cell and make their own mRNA directly from their DNA. (Examples: Adenovirus, Herpesvirus)
Class I: Double-Stranded DNA (dsDNA)
baltimore classification
They need to make their DNA double-stranded first before using it for mRNA production. (Examples: Parvovirus)
Class II: Single-Stranded DNA (ssDNA)
baltimore classification
Their RNA acts directly as mRNA, or they can make single-stranded copies for protein building. (Examples: Reovirus)
Class III: Double-Stranded RNA (dsRNA)
Double-Stranded RNA (dsRNA)
baltimore classification
Their RNA can be directly used as mRNA. (Examples: Rhinovirus)
Class IV (positive-sense RNA):Single-Stranded RNA (ssRNA)
baltimore classification
Their RNA needs to be flipped into a positive strand first for mRNA production. (Examples: Influenza virus)
Class V (negative-sense RNA):Single-Stranded RNA (ssRNA)
baltimore classification
These have RNA, but also carry an enzyme that makes DNA from their RNA. The DNA is then used to make mRNA. (Examples: HIV)
Class VI: Positive-sense ssRNA with Reverse Transcriptase
baltimore classification
Similar to class VI, they have RNA but make DNA with an enzyme. However, their final genetic material is DNA, not RNA. (Examples: Hepatitis B virus)
Class VII: Double-Stranded DNA with Reverse Transcriptase
to summarize, what are the classes of baltimore classification
CLASS I-dsDNA
CLASS II-ssDNA
CLASS III-dsRNA
CLASS IV-ssRNA (+)
CLASS V-ssRNA (-)
CLASS VI-ssRNA with RT
CLASS VII-dsDNA with RT
characterization of viral genomes has increasingly improved as a result of advances in molecular techniques
____ of viral nucleic acid , including entire DNA or RNA genomes, has become a routine procedure in the clinical research setting and has specific applications in the clinical diagnostic laboratory as well
sequencing
due to genetic instability of viral genomes, DNA/RNA sequencing is limited to providing evidence for species relationships, epidemiologic comparisons of isolates, and genotype information - each of which may direct antiviral therapies.
as a result,, clinical virologists generally categorize viruses first as ___
as containing DNA or RNA
check nalang muna if ang genome ni virus is DNA or RNA
then further organize them by family and common names based on nucleic acid sequence and phylogenetic related ness
virus’ Replication occurs only in .
living cells
May lead to the death of the host cell (virulent viruses) or may occur ______ to the host cell (moderate viruses).
without apparent damage
the six steps of replication, called infectious cycle, proceed as follows
attachment
penetration
uncoating
macromolecules synthesis - gene expression gene replication
viral assembly
viral release
viral replication steps
early events - APU
middle events - GG
late events - AR
early events of viral replication
APU
Attachment
penetration
uncoating
middle events of viral replication
GG
gene expression
gene replication
late events of viral replication
assembly
release
this viral replication step is also called as adsorption
attachment
first step in infectious cycle of virus or viral replication
attachment
this step involves recognition of a suitable host cell and specific binding between viral capsid proteins (often glycoprotein spikes) and the carbohydrate receptor of the host cell
attachment
Recognition of a suitable host cell and specific binding between viral capsid proteins (glycoprotein spikes) and the carbohydrate receptors of the host cell.
attachment
this step of viral replication that is also referred to as virus entry
penetration
early events where the Viruses enter the host cell
penetration
one mechanism of penetration involves the formation of syncytia, explain why?
the lipid envelope will fuse with the host cell membrane, this one is not only for internalizing the virus to enter the cell, but also to infect additional host cells forming multinucleated cells
so basically, parang bubblegum, once attach sa isang host cell, it can infect another membrane of other host cell. Magdidikitdikit and will form syncytia
other mechanism of penetration, or how virus are penetrated.
endocytosis - phagocytosis of host cell
injection of viral nucleic acid into the host cell
a type of penetration of naked viruses
direct penetration
also referred as virus entry
penetration
penetration
internalizing of the virus but also leads to fusion between the infected host cell and additional host cells forming multinucleated cells called
syncytia
a penetration of Enveloped Viruses - cell fusion with the cell membrane via _____
endocytosis
an early events wherein there’s a Removal of protein coat to free the nucleic acid
uncoating
it occurs once the virus has been internalized
uncoating
it isthe process by which the capsid is removed; this may be through the degradation of viral enzyme, or host enzymes, or simple dissociation.
uncoating
this process is necessary to release the viral genome for the delivery of the viral DNA or RNA to its intracellular site of replication in the nucleus or cytoplasm
uncoating
Starts at the production and synthesis of mRNA for protein synthesis
gene expression - macromolecular synthesis
In macromoleculr synthesis, it involves viral transcription of mRNA which encodes the __
early and late viral proteins
gene expression Depends on the ______ and ___ of the nucleic acid
type of nucleic acid; polarity
Middle event: _______Synthesis
Macromolecular
mRNA encodes for early viral proteins, describe the early proteins
non structural elements such as enzymes
mRNA encodes for late viral proteins, describe the late proteins
structural components
DNA gene expression happens in the nucleus because it needs the enzyme polymerase except what family
Except for Poxviridae-gene expression happens in the cytoplasm because they carry their own enzymes)
RNA gene expression of Poxviridae happens at the _____ because they already carry their own enzyme
cytoplasm
which polarity of RNA does not need to convert mRNA as they can use the RNA itself to produce proteins
positive
RNA type with (__) polarity-acts as a template to produce mRNA with the help of RDRP (RNA dependent RNA polymerase). Kailangan muna maconvert to positive sense before translation
negative
Duplication of many nucleic acids
gene replication
2 proteins are synthesized by the mRNA
early protein
late protein
early protein synthesized by the mRNA is for
transcription - non structural components such as enzymes
late protein synthesized by the mRNA is for
structural components of the virus
This is the process of copying DNA into RNA. It usually happens in the cell’s nucleus, but some viruses do it differently. The copied RNA is then changed a bit before being used.
transcription
This is the process of turning RNA into proteins. It happens outside the nucleus. These new proteins are often sent back into the nucleus to help the virus multiply.
translation
late event wherein Structural proteins, genomes and viral enzymes are assembled into virus particles.
assembly
in this process the Envelopes are acquired during viral “budding from a host cell membrane
assembly
common area for budding to form an envelope
nuclear endoplasmic reticulum and cytoplasmic membrane
Acquisition of an ____is the final step in viral assembly
envelope
2 ways to Release of intact virus particles occurs
cell lysis or virus particle budding.
detection of virus released by budding is more difficult, because the cell monolayer remains intact.
an example of it is the influenza viruses, which as released by budding with minimal cell destruction, it can be detected in cell culture by an alternative technique called
hemadsorption
explain the process of hemadsorption as an alternative technique used in cell culture to detect virus that uses cell budding as a way to release viruses
when the red blood cells are added to the plate with the cells that might have viruses, if the virus is there, it will make the red blood cells stick to the surface of the “houses.” Scientists can then see that the red blood cells are sticking and know that the virus is there because only certain viruses can make the red blood cells stick this way.
In short, hemadsorption is a test where scientists use red blood cells to check if viruses are on the surface of the cells that are releasing them through cell budding. If the red blood cells stick, it means the virus is there!
period of viral infection wherein no detected virus in the cells
during eclipse period
viral infections may produce one of three characteristic clinical presentation
acute viral infection
latent infection
chronic or persistent infection
this viral clinical presentation displays evident signs and symptoms
acute viral infection
this viral clinical presentation has no visible signs and symptoms observed, but the virus is still present in the host cell in a lysogenic state (resting state) or maintained as a nuclear or cytoplasmic episome
latent infection
the viral clinical presentation, in which low levels of virus are detectable and the degree of visible signs or symptoms varies
chronic or persistent infection
period of viral infection wherein virus are detected in cell, but no manifestations
Dito na magmanifest of infection. Nagkakaroon na ng cytopathic effect.
latent period
alteration in the morphological and functional ability of the virus inflicted cells
cytopathic effect
determinants of the viral disease
what are under the nature of the disease
target tissue
portal of entry of virus
access of virus to target tissue
tissue tropism of virus
permissiveness of cells for viral replication
pathogenic activity (strain)
Cytopathic effects
cell lysis
cell fusion
inclusion bodies
presence of appropriate receptors on the surface of the cell determines whether virus can adsorb to it and the virus gets into the cell
cellular factors
Death of the cell is followed by lysis and release of large numbers of virions.
cell lysis
Some cause fusion of adjacent cell membranes, leading to syncytium formation by paramyxoviruses
cell fusion
____ and some retroviruses also give rise to syncytia
Herpesviruses
structures with distinct size, shape, location and staining properties that can be demonstrated in virus infected cells under the light microscope
inclusion bodies
may confer new properties on the cells.
new cell-surface antigens
: viruses such as measles, mumps, adenoviruses, cytomegalovirus and varicella virus cause damage to the chromosomes of host cells
damage to the chromosomes of host cells
Viruses have evolved mechanisms to continue to survive in the face of a strong host immune response
latent and persistent infections
2 types of inclusion bodues
intracytoplasmic inclusion bodies
intranuclear inclusion bodies
an inclusion bodies of viruses that have cytoplasmic assemble yield cytoplasmic inclusion
intracytoplasmic inclusion bodies
Intracytoplasmic inclusion bodies are found in cells that are infected by
These are found in cells infected with
rabies virus (Negri bodies),
vaccinia (Guarneri bodies),
fowl pox (Bollinger bodies),
molluscum contagiosum (molluscum bodies), paramyxoviruses and reoviruses
Intranuclear inclusion bodies are seen in cells infected by
found in cells infected with herpesviruses, adenoviruses and parvoviruses
intranuclear inclusion bodies
were classified into two types by Cowdry (1934)
Cowdry type A
Cowdry type B
Cowdry type ______ inclusions - variable size and granular appearance (as with herpesvirus, yellow fever virus
A
Cowdry type ______ inclusions - more circumscribed and often multiple (as with adenovirus, poliovirus)
B
Some viruses, such as _____ may produce both intranuclear and intracytoplasmic.
measles virus and cytomegalovirus
phenomenon where a virus enters a dormant or “sleeping” state within a host cell. This allows the virus to persist for long periods without causing any noticeable symptoms.
VIRUS LATENCY
Virus Latency virus example
herpesvirus, CMV, EBV, HBV,
viruses that utilizes respiratory transmission
paramyxoviruses
influenza viruses
picornaviruses
rhinoviruses
varicella-zoster vvirus
b19 virus
viruses that utilizes feco-oral transmission
picornaviruses, rotavirus, reovirus, noroviruses, adenovirus
viruses that utilizes contact (lesions or fomites ) transmission
herpes simplex virus, rhinoviruses, poxvirus, adenovirus
viruses that utilizes zoonoses transmission
togavirus
flavivirus
bunyavirus
orbivirus
arenavirus
hantavirus
rabies
influenza A
orf (pox)
viruses that utilizes blood transmission
HIV
HTLV- 1
HBV
HCV
HDV
cytomegalovirus
viruses that utilizes sexual transmission
blood borne viruses
herpes simplex virus
human papillomavirus
molloscum contangiosum
viruses that utilizes congenital transmission
rubella
cytomegalovirus
b19
echovirus
herpes simplex
varicella zoster
HIV
viruses that utilizes genetic transmission
prions
retroviruses
Entry: Virions enter through an epithelial surface, - undergo __ replication.
limited
Migration: migrate to the __where some are taken up by macrophages and inactivated - others enter the bloodstream.
regional lymph nodes
: Virions which enter the bloodstream
Primary viremia
: From the blood, the virus gains access to the large reticuloendothelial organs—liver, spleen, and bone marrow—in which it again multiplies, and a large amount of virus is produced which again spills over into the bloodstream
Secondary viremia
: reaches the target organ through the bloodstream - Multiplication in the target sites produces the distinctive lesions.
Target organ
\represents the time taken for the virus to spread from the site of entry to the organs of viral multiplication and hence to the target organs for the production of lesions.
incubation period
incubation period where less than a week and primarily applies to viruses causing localized infections that spread rapidly on mucous sur faces.
short incubation period
this incubation period has a span of 7-21 days
medium incubation period
periods measured in weeks or months (e.g. 2–6 weeks for hepatitis A and 6–20 weeks for hepatitis B).
long incubation period
measured in years, which is why the agents involved were originally termed ‘slow’ viruses. .
very long incubation period
immunological response to virus infection
antibody-mediated immunity
non-immunological response to virus infection
phagocytosis
fever
hormones
malnutrition
age
interferon
__ protects the host against reinfection by the same virus.
Humoral immunity
which Ig plays a major role in blood and tissue spaces
IgG and IgM
role of Ig A in immunity
secretory IgA antibody is important in protecting against infection by viruses through the respiratory or gastrointestinal tracts
act as a natural defense mechanism against viral infections as most viruses are inhibited by temperatures above 39°C.
fever
Careless use of steroids in the treatment of ___ may cause blindness
herpetic keratoconjunctivitis
