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MIMM-211 final > Virology #2 > Flashcards

Virology #2 Flashcards

1
Q

Overall infectious cycle

A

Single birion will give rise to several or even thousands of new virus in a single host cell…basic mechanisme:

Attatchment/adsorption of a virion to a receptor site on host cell

Entry/Penetration of virion or its genome in host cell

Uncoating (for animal vuris): caosid seperate and release viral genome

Biosynthesis of new nucleic acids and viral proteins by the host cell’s enzyme and ribosome (transcritption, translation, replication)

Assembly of new viral particles within the host cell

Release of newly formed virions from host cell (pic for summary )

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2
Q

2 phases of viral infectious cycle

A

EArly phase: attachment to delivery of the genome+ “Early P” synthesized soon after injection and are usually need to take control of the host cells and for viral genome replication

Late phase: “Late P”=virus structural P such as capsomere+ Final steps of the infectious life cycle–>assembly and relase

Check pic

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3
Q

2 different cycle

A

Lytic: ends witht he lysis and death of host cell (virulent phages)

Lysogenic cycle: host cell stays alive, phage DNA=incorporated ito the host DNA (temperate phages)…virus are called latent (may be for years)
can exist in episome: sperate from the host cell chromosal DNA and estblishe latency

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4
Q

Attachment

A

Virus cant diffuse passively thru membrane… must attach to receptors on host cell surface

BActeriphages: Chemical attraction(viral P& cell P on cell wall)+some use fibers at the end of their tails to attach to host cell surface (tails anchored to cell wall)

Animal virus: GlycoP spikes (envelopped viruses) or other attachment molecule on capsid (naked virus) that mediate attachment to plasma mem P/receptors+ Virus bind specifically: Host range/specifitu depend on viral: depends on viral and host surface molecular interaction…

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5
Q

Entry/Penetration

A

Entry of viral genome into host cells

Bacteriohages: rekease a P enz (lysozyme)=weakends bact. cell wall+phage tail pierce thru cell wall+nucleic acid from capsid go thru tail and enter (only nucleic acid enters)

ANimal virus: Direct penetration or membrane fusion or Endocytosis…check pic

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6
Q

Direct penetration

A

Naked viruses
Capsid attaches and sinks into the cytoplasmic membrane, creating a pore where the genome enters

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7
Q

MEmbrane fusion

A

Viral env and host memb fuse, releasing capsid into the cell wall cytoplam

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8
Q

Endocytosis:

A

Envelopped and naked virus

AFter attachment, host cell negulfs the entire virus

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9
Q

Uncoating (only in animal virus)

A

Seperation of viral nucleic acid from its capsid…process varies with virus type:

Action of lysosomal enz of the host cell
Acidification of the content of the endosome: diassembly of capsid
For some viruses, uncoating occus in the host cytoplasm, other in nucleus,

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10
Q

Biosynthesis

A

Bacteriophage:
Synthesis of many copies og phage DNA using host cell’S nucleotide and several of its enz+ After, biosynthesis of viral P begins, using host cell ribosomes and aa

Animal virus: Baltimore’s classes

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11
Q

Assembly

A

Bacteriphages:
Nucleic acid and viral P assembled into complete virions

Animal: Spontaneous process…most DNA viruses assemble in the nucleus…most RNA assemble in cytoplasm

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12
Q

Realease

A

BActeriphage: lysis: host cell breaks open and dies (lyytic cycle)

Animal: relase via budding (acquire a portion of the cellulat membrane into which viral P r inserted in synthesis stage)… naked viruses are relased by exocytosis(similar to budding but without acquisition of env.) or lysis

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13
Q

REquirement for a successful infection

A

Enough virus
Cel susceptible and permissive
Local antiviral defense absent or overcome

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14
Q

PAttern of a viral infections

A

Abortive inf
Acute inf
Chronic inf
PErsistent inf
Latent inf

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15
Q

Abortive infection

A

Virus enter hose cell bu cant complete replication cycle successfully

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16
Q

Acute infection

A

Short-term , intense infection

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17
Q

Chronic infection

A

Long lasting, virus continously produce low levels of new particles and host immune sutem may struggle to clear infection

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18
Q

Persistent aingection

A

Long lasting , virus comes in waves periodiclaly reactive and replicate leading to eccurent symptoms

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19
Q

LAtent infections

A

Virus remains dormant or inactive in host for a long time (In waves but longer timespan)

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20
Q

Viral tropism

A

Cellular tropism
Tissue tropism
host tropism

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21
Q

Cellular tropism

A

Virus replicates ina particulat tissue or organ but not in another

22
Q

Tissue tropism

A

Virus replicats ina particular tissue or organ but not anotehr

23
Q

Host tropism

A

Virus replicates in one host specie sbut not another

24
Q

Virus spread within the body

A

Virus stay localized and containe by tissue struc

Some spread beyong and lead to systemic infection (many infected organs)

2 components of viral disease: Effects of viral replication on the host and effect of host reponse on virus and host

25
Q

Mode of virus transmission

A

Direct transmission person-person (aerosol, fecal-oral, sexual contact, transfusion of contam blood, Hand-mouth/eye, mouthe mouth contact)

Animal to animal, with humans as accidental hosts (bite, aerosols from rodent- contaminated quarters)

TRansmission by anthropod vector (mosquitos)

26
Q

TRansmission

A

Horizontal transmission: members of same species

Vertical tr: parent and offspring

Germ line trans: AGent transmitted as part of the genome

Nosocomial: Inf while in hospital or health care faiclity

27
Q

Zoonosis

A

Any disease or infection that is naturally transmissible from animals to humans

Animal=essetial role in maintaning zoonotix infections in nature

May be bacterial, viral, fungal or parasitic

28
Q

Emerging viral disease

A

Env change (drought…)

human behavior(drug use…)

Social, political, economic facto(poverty)

TRavel and commerce (air travel…)

Health care (blood transfusion…)

Microbial adaption (microbe mutation…)

Public health measure (inadequate vaccine)

29
Q

Culturing virus in lab

A

Cannot grow in culture media…need a host…. 3 type of media:
Mature organisme (bact.plant. animals)
Embryonated (fertlized eggs)
Cell culture

30
Q

In bacteria (culture)

A

BActeriophage… bacteria from liquid culture or on agar plate

Plaque assay technique (chekc pic):
1- Mix bact. and phages with liquid warm utrient agar and poured in a thin layer across the surface of an agar plate
2- Lysis of bact. produces plaques: Virulent phage makes plaque (lytiv)
TEmperate phages (lysogenic cycle)
Allow the estimation of phages #

31
Q

Culturing virus in plant and animal

A

Studying immune sys response in infected live animals

Anima inoculation may be used as a diaagnostic procedure, identify and isolate virus from clinical specimen

32
Q

In embryonated eggs

A

Inexpensive
STerile
Ideal site for growing virus:
virus injected into the egg…viral grwoth signaled by changes/death of embryo

Some vaccine still prepared in cheicken egg culture

A hole is drilled in shell and viral suspendion injected into egg’S fluid… viru sinjected at sites best suites for their replication

33
Q

Cell culture

A

ll isolated from an organisma nd grown on a medium/broth

Practical when antibiotics provided a way to limit bact. growth and use of Bioseafety cabinet… less expensive also

Tissues are treated with enzyme to seperate cells that are suspended in a solition with appropriate factors for cells to grow

normallu (primary ) cells tend to adhere to the glass or plastin container and reproduce to form a monolayer

TRansfomed cells (cancerous/continuous) do not grow in a monolayer (monolayer deteriorated)

34
Q

Type of cell line in cell culturee

A

Primary
Continuous

35
Q

Primary cellli ne

A

Derived from tissues or organs, tend to die out after on lu a few gen.. contact inhibition slows the growth of the cells when too dense (so growth sustained by making a second culture)

36
Q

Continous cell line

A

TRansformed(cancerous) cells can maintain indefinite # of gen. and can frow regardless of cell density (no contact inhibition)

37
Q

Cytophatic effec t(CPE)

A

Changes in cell morphoology caused by infecting virus:

Cell death

Rounding (sweilling) or shrinkage of the infected cell

Fusion with adjacent to forma syncytia

Appearance of nuclear or cytoplasmic inclusion bodies

38
Q

Plaque assays

A

A SINGLE BIRYS IS SUFFICIENT TO PRODUCE A PLAQUE

formation relies on virus infection and lysis of host cell

Method to quantify the # of infectious viral particle in stock

PLAQUE-FORMING UNIT (PFU/mL)

39
Q

Plaque formation by a lytic virus

A

Initial cell infected by 1 virion (cells covered with agarose)

Infected cells lysed and virion=released
Newly made virions infect and lyse neighboring cells
Infection process is allowed to proceed intil the area of cell lysis becoms sufficietly large to be visible

**MOI

40
Q

MOI

A

Multiplicity of infection: average #of infectious particles addded/cell (ratio #virus particles/#host cell in infection medium)

**different from # of infectious particle that infect each cell (we can control that)

Distribution of virs/cell is best described by the Poisson distribution (graphique)

41
Q

Focus forming assay (FFA)

A

Not all virus lyse cells

FFA is immunostaining technique and a variation of plaque assay

Useful for quantifying virus that cause CpE: visible damage in host cells but not cell death: host cell from cluster of infected cells (foci) that can be visualised with fluorescnece or stain using antibodies agaisnt a viral antigen

42
Q

Cell division and cancer

A

Cell division:

Under stric genetic control: gene dictate if cell can longer divid… those that can are prevented from unlimited div…. gene for cell division can be turned on/off

Neoplasia: uncontrolled cell division.. mass of neoplastic cell is tumor

Benign(unharmful) VS malignant(cancer…metastasis=when tumors spread)

43
Q

Oncogene theory of the Induction of Cancer in humans

A

Proto-oncogene promote cell growth/division

Uncotrolled activation of oncogene (active proto-oncogene) can lead to cancer(transform normal cell to cancerous)

Env. factor contribute activation of oncogene: UV, radiation, carcinogen (mutagenic chemicals, viruses)

Viruses may cause 20-25% of human cancer: carry copies of oncogene as part of genome, promoste ecogene alr prenset, inerfere with tumor repressionééé oncogenic virus becoms integrated into the host cell dNA and induce tumor

PICx2

44
Q

Nomal cells to TUmor cells

A

oncogenic virus REplicate alon with the host cell chrom

Tumor cell acquire properties that are distinct from normal

Transformed cells tend to be irregularly shaped, increased cell motility, lose contact inhibition culture

45
Q

RNA oncogenic virus

A

REtroviridae some

Viral RNA is transcirbed to DNA (using Rev. tranc)=can integrate into host DNA=provirus
Ex. human Tcell leukamia viru cause leukemia and lymphomaSome retroviridae contain oncogene, other have promoter that turn on oncogene or other cancer-causing factors

46
Q

Virus to treat virus

A

Oncolytic viruses infect and lyse cancer cell

Virus geneticaly modified to slectively infect cancer cells

47
Q

SARS-Cov-2

A

SEver acute respiratory syndrome coronavirus 2
Envelopped, (+) ssRNA virus, ACE-2 receptor on cell required for entry (Class 4)

Electron microscopy show the spie glycoprotein that gives the virus a shape of a crown

Coronaviruse fenerally cause mild upper respiratoru illess and cause 10-30% of common cold cases

2019=pic

48
Q

mRNA vaccine

A

mRNA encoding the antigen of choice encapsulated in liquid nanoparticle… after injection, P production in muscle cells peaks

SImpler and quicker to synthesize

49
Q

Influenza Virus

A

Spanish Flu: (-) ssRNA, helical capsid, env with glycoP

GlycoP are hemagglutinin (HA/H antigen) and neuraminidase (NA or N antigen).. each virus has one type HA and one NA

50
Q

Plasticity of Influenza Genome… IMPO

A

Antigenic drift: minor change in influenza virus antigene due to gene mutation

Antigenic shift: major change in ingluenza virus antigen due to gene reassortment

MIMM-211 final (7 decks)

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