Virology - Exam 4 Flashcards
who discovered the filterable infectious agent, toxin?
Ivanoski
who discovered agent multiplied only in cells, the actual virus?
Beijerinck
who discovered viral structure under EM?
Stanley
who discovered first proof of viral infections in animals?
Loeffler & Frosch
who vaccinated first against rabies but was unable to find the causative agent?
Pasteur
importance of cow pox virus
milkmaids, cows, pustules, inoculation/vaccination
definition of viruses
broad terminology, infectious or inactivated virus particle, or viral nucleic acid and protein in infected host cell
definition of virology
study of viruses and viral diseases
definition of virologist
someone who studies viruses
definition of veterinary virology
the study of viruses in non-human animals
definition of taxonomy
science of naming, describing, and classifying organisms
definition of bacteriophages
viruses that infect bacteria and can sometimes kill them, icosahedral head and helical tail
definition of oncolytic viruses
viruses that infect and kill cancer cells, oncolysis, stimulation of host antitumor immune responses
definition of virion
a complete virus particle that consists of an RNA or DNA core with a protein coat, extracellular infective form of a virus
definition of viriod
infectious particle smaller than any of the known viruses, plant diseases, very small circular RNA molecule, lacking the protein coat of a virus
definition of prion
infectious agent composed of protein material that can fold in multiple ways leading to disease that is similar to a viral infection
definition of arbovirus
arthropod born virus, replicates in and is transmitted by bugs, maintain in nature by going through cycle between host and vector
definition of genome
viral DNA or RNA, only a few genes, code for structural components and enzymes needed
definition of capsid
protein shell that encases the viral genome, most viruses have one (except Reoviruses), usually symmetrical
function of a capsid
protection, antigenic sites, and virus attachment
definition of capsomere
basic subunit protein of the capsid
definition of nucleocapsid
capsid and viral genome
definition of an endosome
membrane bound compartment, Golgi, lysosome for degradation or recycled back to plasma membrane
definition of budding
enveloped proteins, peel out with membrane
definition of exocytosis
opposite of endocytosis, packaged before exiting
definition of fusion
merging of the virus envelope with the host cell lipid bilayer membrane, mediated by pH, enveloped viruses only
definition of prophage
virus genome of bacteriophage that’s integrated into the DNA of a host cell
definition of provirus
virus genome that’s integrated into the DNA of a host cell
definition of eclipse infection
infectivity of the virus disappears due to uncoating
definition of acute infection
rapid onset of disease & symptoms
definition of latent infection
virus remains in asymptomatic host cell for long periods
definition of persistent infection
disease processes occurring over a long period, fatal, noncytocidal changes
definition of passive viremia
direct inoculation of virus in host and no replication at site of entry
definition of active viremia
viremia following virus replication in host
definition of primary viremia
spreading into the blood from infected area
definition of secondary viremia
spreading to other organs/tissues
definition of cytopathic
toxic viral proteins, interferences with cell membrane function
definition of neoplastic
tissue becoming malignant
definition of inclusion bodies
represent sites of viral replication in nucleus/cytoplasm, viral capsid proteins
definition of negri bodies
eosinophilic inclusion bodies found in cytoplasm of nerve cells infected by rabies virus
definition of hemagglutination
assay used for quantification of virus dilutions involving RBC
definition of apoptosis
programmed cell death
definition of HeLa & Vero cells
transformed (cancerous) immortal cell lines, keep multiplying in different layers
definition of TCID50
tissue culture infectious dose
definition of LD50
50% lethal dose
definition of ID50
50% infectious dose
definition of immunoprophylaxis
prevention of disease by the production of active/passive immunity
definition of adjuvants
formulations added to vaccines to improve immunogenicity
parameters for virus classification
genome, replication strategies, and morphology
Baltimore’s Classification System
7 different classes based on viral genome, strandedness (double or single), or sense (positive or negative; polarity)
what is an envelope
lipid bilayer with embedded glycoproteins, makes it more fragile
function of an envelope
facilitates virus entry into host cells, helps virus adapt quickly and evade host immune system
capsid symmetry
normally icosahedral or helical (capsomeres and nucleic acids wound together)
steps in the flow of genetic information
transcription, translation, replication
transcription
DNA copied into RNA via RNA polymerase
translation
mRNA read to form a protein
6 steps in replication
attachment, penetration, Uncoating, replication, assembly, and release
Attachment/adsorption
attachment of the virion to the host cell surface, receptor selectively bind specific substrate, can use host cell receptors
Penetration/entry
bringing the viral genome to the other side of the host cell’s plasma membrane, energy and temperature dependent, via endocytosis, membrane fusion, or direct penetration
endocytosis
virus gains entry into host cell without passing through membrane, active transport
direct penetration
viral genome injection into the host cell’s cytoplasm after initial attachment, pore mediated, naked viruses only
Uncoating
capsid protein removal and the release of viral genome in the host cell, programmed, mediated by pH and lysosomal enzymes, large viruses have their own Uncoating enzymes, loss of infectivity, makes it fragile
Replication/synthesis
genomic expression of the viruses, replicate, and make functional proteins
Assembly/maturation
packing the viral genome and proteins into new virions following a specific order, Golgi, building blocks
Release/shedding
expulsion and release of progeny virions via budding, exocytosis, or cell lysis
cell lysis
naked virions, break open and fall out quickly
reverse transcription
synthesis of DNA from an RNA template
key enzymes in DNA replication
DNA polymerase, RNA polymerase, reverse transcriptase, made in nucleus except Pox
key enzymes in RNA replication
RNA polymerase, ribosomal enzymes, made in cytoplasm except Retro and Flu
life cycle of a DNA virus
virion attaches, enters, DNA uncoated, transcribed, mRNA produced, DNA replicated, capsid proteins made, virions mature & release
life cycle of a pox virus
large and have more genes so they carry their own RNA polymerase and produce mRNA in the cytoplasm
which entry method will pox viruses NOT use
direct penetration
life cycle of an RNA virus
attachment, entry, Uncoating, RNA replication by RNA polymerase, translation and synthesis, maturation and release, positive or negative strandedness, can do twice and make a double strand
life cycle of a retrovirus
penetration, Uncoating, reverse transcription of RNA -> DNA, DNA -> nucleus (provirus), can divide indefinitely with the host cell DNA
life cycle of influenza virus
attachment, endocytosis, RNA enters nucleus and replicated via polymerase, mRNA makes new proteins and releases into ECF
horizontal transmission
within same species, to each other
vertical transmission
to offspring
cross species transmission
between different species
zoonosis
from animal to human or vice versa
role of reservoir hosts & example
hold infection without being sick, mode of transmission i.e.: ebola in bats
example of abnormal cell growth
cancer
example of cell damage/death
lysis, cell membrane alteration, apoptosis
example of no apparent changes
persistent, latent, immunosuppresion
4 steps of infection in host
adsorption/entry, Uncoating/replication, maturation, and release (infective form)
primary cell line
derived from tissues, die after a few generations
diploid cell line
developed from human embryos, grow for many generations
ECE
embryonated chicken eggs; used for virus isolation, identification, and production of vaccines via candling. can detect virus via mortality, lesions, inclusion bodies, viral antigens, and hemagglutination assays
methods of viral diagnoses
EM, fluorescent antibody staining, or immunocytochemistry
innate immunity
non-specific, constantly present, no previous exposure to virus required, rapid response
adaptive immunity
specific, develops after virus exposure, specific to that virus, cross-protection, slow response
first line of defense
chemical and mechanical barriers, reflexes
second line of defense
innate immunity
third line of defense
adaptive immunity
antiviral drugs
dependent on metabolic pathways of their host cell for replication, most agents that interfere with virus replication are toxic to the cell i.e. interferon
immunoprophylaxis
prevention of disease by the production of active/passive immunity
active immunity
most effective, vaccinations
passive immunity
antibodies administered, vaccine of pregnant animal will pass immunity to offspring
live attenuated vaccine
viable virus but with reduced virulence tissue cultures, embryonated eggs, live animals, parental, oral, nasal
inactivated vaccine
killed virus particles, purified proteins and lipid solvents, formaldehyde
recombinant vaccine
protein antigens to induce immunity against the virus using adjuvants, yeasts, bacteria
