Beginnings Of Virology Flashcards by Lara JO

Where do infectious diseases rank in world wide number of cause of death?

Place 2, number 1 is cardiovascular diseases

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Which six diseases cause 90 % of infectious disease deaths?

Pneumonia, tuberculosis, diarrhoeal diseases, malaria, measlees, HIV (and Sars Cov2)

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What is the abiogenesis theory and how was it disproven?

Life forms spontaneously out of unenlivend matter (maggots in rotting meat) — disproven by Pasteurs Swan neck bottle

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Against which viral diseases where the first vaccines developed?

Human Pox (Variola), Rabies

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What did Robert Koch establish?

-Animal model: Anthrax pathogen from cattle to guinea pig
-Systematic approach
-Transparent artificial culture media

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What are the principles of the Koch-Henleschen Postulate?

Pathogen must be detectable in all diseased animals, not in healthy ones (problematisch in Viren: persistente/latente Infektionen)
cultivating pathogen in pure culture (not possible with Kochs Method)
pathogen can reproduce disease in healthy individuals (Problematic in viruses, long incubation period)
Pathogen can be reisolated from newly diseased animals

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Is it possible to cultivate viruses with the methods of Robert Koch?

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What was a crucial technique to cultivate viruses? (to fullfill kochs postulates)

Ceramic filter — bacteria can be separated
Virus is stopped by fine grain Kitasto filter — no toxid fluid = virus concept

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What are the first described viruses? And which virus is the first HUMAN virus identified?

NON HUMAN:
Tobacco Mosaic Virus (not filterable)
Foot and mouth disease virus

HUMAN
Yellow fever virus (Flavivirus)

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Where is yellow fever found? What is the route of transmission? What vaccine is used?

-In tropical regions transmitted by mosquito (=vector) but no transmission from patient to patient
-Vaccine: attenuation in chicken embryo cell culture (17 D)

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Why is it easier to isolate bacteria than viruses?

Viruses are submicroscopial genetic parasites which need the cellular system of the host for their replication –> identification of a permissive (animal) host needed
They are obligate intracellular — effective cell culture systems required

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What are the problems of animals as model organisms for viral diseases? What is the solution?

Ethics
Costs
Hazards
Space requirements
Reproducibility

SOLUTION: working with cells instead of whole organisms

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Eukaryotic cell cultures: What are primary cell cultures and permanent cell cultures and what is the advanatge?

Primary: cells directly from an animal — passages — dedifferentiation and dying after only a few passages

Permanent: use of tumor cells from patients or artificial tumor cells

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How can cells be artificially immortalised?

-Tumor virus
-Chemical/ physical noxa
-Genetechnical manipulation

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What are the requirements for effecient cell culture techniques?

-Sterile working
-Antibiotics
-Culture medium
-Immortalisation
-Growth factors (undefinded ingedients: serum, plasma, lymph, extracts of embryos; defined: factors produced by industry)

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What are the characteristics of the polio virus?

Transmission between human host and animal host is possible
Live ettenuated vaccine in HeLa cells

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what are the characteristics of a virus?

-infectious
-very small parasites
-obligate intracellular
-viral genome (DNA or RNA)
-genome replicated in suitable host cell
-new viruses generated de novo in host cell

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what do viruses lack?

-protein translation apparatus
-own enegergy generation

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what are always the components of a virus?

-nucleic acid
-capsid

what is the capsid?

protein layer encoded by virus

what facultative components of a virus are there?

-envelope (protein)
-lipid membrane

what is the simplest way to arrange identical protein subunits? What defines the structure? And which form does the virus have?

helix –> helical virus
defined by amplitude and pitch

is the virus morphology a good parameter for defining a virus?

no, because it is very diverse

What are the criteria for classification of a virus?

-Type of nucleic acid for the genome
-existence of an envelope
-symmetry of the capsid (helical, icosahedral)
-arragement of genes
-replication strategy

which criteria concerning the classification of viruses regarding the nucleic acids are used?

-DNA, RNA -size -single stranded, double stranded -linear, circular, segmented

what are not criterias to classify viruses?

-host range -pathogenicity and kind of disease

how many viruses classes are there according to the baltimore schema?

I-VII

How is the ICTV nomenclature structured? (important for exam)

order: virales family: viridae genus: virus species: name

whose genome is bigger: RNA virus or DNA virus? Why?

DNA virus, because the RNA polymerase has no proofreading function (no stability in sequence)

What types of subviral infectious agents are there?

Virosoids Viroids Prions

what are the characteristics of virusoids? Name one example

encode proteins but not capsid proteins, they are helper dependent viruses (the virusoid-nucelic-acid is packaged by the capsid proteins of the helper virus) e.g.: Hepatitis delta virus

what are the characteristics of viroids?

infectious RNA, encodes no proteins, capsid or envelopes at all RNA is self complementary and forms rod shaped stabile structures infect plants

what are prions?

infectious proteins, but no nucleic acid

which prion diseases are known?

Creutzfeldt_jakob Scrapie BSE chronic wasting disease

How can virus infection be detected in a cell culture?

cytopathic effect development of inclusion bodies hemadsorption

what are the steps of the viral replicative cycle?

adsorption penetration replication generation of new particles release by cell lysis (virus burst)

How can viruses be counted?

addition of dilution series on tissue culture cell counting of plaques in the monolayer

how can a biologically cloned virus be isolated?

covering the cell culture with agar local cell lysis viral progeny is locally fixed/stained isolate plaque with pipette

which assays can be used to quantify viruses?

-plaque assay (quantifies only infectious particles) -focus assay -EM -Pock assay (Pock formation) -Hemagglutinin assay

how can cytolytic and non-cytolytic viruses be counted?

lytic: plaque forming units non-lytic: focus forming units (dye reaction)

what is the difference between polyclonal antibodies and monoclonal anitbodies?

polyclonal: wide reactivity, low specificity monoclonal: high range of reactivity, high specificity (one epitope)

what are ambisense genomes?

ssRNA: genome and antigenome or coding

Which viruses replicate via reverse transcription?

L+RNA (Retroviridae like HIV) C-ss/ds DNA (Hepadnaviridae like HBV)

Define primary cell culture and cell line

primary cell culture: culture of cells from original tissue cultivated in vitro for the first time (not immortal but can be sub-cultured or gworn into strains) cell line: immortal cell cultures (spontaneous or induced)

How does the plaque assay work?

Ability of a single infectious viral particle to form a macroscopical, cytopathic effect in a monolayer of cultivated cells