Virology Set I

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What is the definition of a virus?

Submicroscopic
Obligate intracellular 'parasites'
Replicate only in living susceptible cells

Do viruses have metabolic activity?

No

Do viruses have ribosomes or tRNA?

No

Do all viruses have envelopes?

No

What virus families have double-stranded (ds) DNA genomes?

Papillomaviridae
Adenoviridae
Herpesviridae
Poxviridae
Asfarviridae

What virus families have single-stranded (ss) DNA genomes?

Circoviridae
Parvoviridae

Which virus families have double-stranded (ds) DNA genomes?

Reoviridae
Birnaviridae

Which virus families have +ve RNA genomes?

Picornaviridae
Caliciviridae
Coronaviridae
Arteriviridae
Flaviviridae
Togaviridae

Which virus families ahve -ve RNA genomes?

Orthomyxoviridae
Paramyxoviridae
Rhabdoviridae
Filoviridae
Bunyaviridae

What do virion proteins do?

Protect nucleic acids
Attach to receptors on cells
Penetrate cell membrane
Replicate nucleic acid
Begin program for replication
Modify host cell

Which two virus families replicate via reverse transcriptase?

Retroviridae
Hepadnaviridae

What three methods are used for virus cultivation?

Animal inoculation
Inoculation into embryonated eggs
Cell culture

What are the different types of cell culture?

Primary cell culture
Finite or diploid cell lines
Continuous cell lines

How are host cells generally damaged by viruses?

Accumulation of viral structural components
Formation of virion aggregates within the cell
Shutdown of cellular protein synthesis

What are some methods used for virus titration?

Plaque assay
Pock assay
Transformation assay
Quantal assays (TCID50, ID50, LD50)

What are some methods used for virus isolation and identification?

Light microscopy
Films and smears
Biopsy or autopsy
Electron microscopy

What are some methods used to detect viral antigens?

ELISA
Radioimmunoassay (RIA)
Immunofluorescene (IFA)
Immunoperoxidase staining
Radioimmunoprecipitation (RIP)
Western blotting

What are some methods used to detect viral nucleic acid?

Dot-blot hybridization
In-situ hybridization
Southern blot hybridization
Northern blot hybridization
Polymerase chain reaction (PCR)
Nucleic acid sequencing

What are some methods used to identify viral isolates?

Hemagglutination and hemagglutination inhibition
Hemadosporin and hemadosporin inhibition
Complement fixation

What are some limitations of using serology to detect a viral infection?

Detects exposure not when exposure occurred
For correlation with disease
Paired sera
IgM only produced early in infection
CSF

How are 'quasispecies' of viruses made?

Errors in replication

What substances can induce virus mutations?

Nitrous acid
Hydroxylamine
Nitrosoguanidine
5-bromodeoxyuridine
Ultraviolet light

What are some different types of mutations?

Plaque morphology mutations
Host range mutations
Temperature-sensitive mutations
Deletion mutations
Point mutations

What are some different genetic interactions between viruses?

Complementation
Recombination (breakage-reunion mechanism, copy-choice mechanism, reassortment)

What are some non-genetic interactions between viruses?

Heterozygosis
Interference
Phenotypic mixing

What are some possible interactions between a virus and it's host cell?

Lysis
Transformation
Integration
Persistant infection

What two types of maps are used to map viral genomes?

Restriction maps
Transcriptional maps

Where do DNA viruses replicate?

Nucleus of host cell

Where do RNA viruses replicate?

Cytoplasm of host cell

What are the main enzymes that viruses use for nucleic acid replication or mRNA synthesis?

DNA-dependent DNA polymerase
DNA-dependent RNA polymerase
RNA-dependent DNA polymerase
RNA-dependent RNA polymerase

What are some different ways that viruses penetrate a cell?

Translocation
Endocytosis
Fusion
Injection

What viral genes encode for enzymes or factors that help in virus replication and are expressed before nucleic acid replication?

Early genes

What viral genes encode for structural proteins and factors for virus assembly and are expressed after nucleic acid replication?

Late genes

In which phase of viral reproduction does attachment, penetration, and uncoating take place?

Eclipse phase

In which phase of viral reproduction is the virus assembled?

Maturation phase

In which phase of viral reproduction does the virus get out of the cell?

Release phase

In which phase of viral reproduction does the virus lose it's infectivity?

Inactivation phase

What are some mechanical and chemical barriers to viral infection?

Skin
Epithelial cilia
Low pH

What are some factors that defend against viral infection?

Fever
Age
Nutritional status
Hormones
Genetics
Species resistance

What are some defenses against viral infection that are present in the extracellular fluid?

Macrophages (B & T cells)
Dendritic cells
Plasma cells

What are some defenses of viral infection that act on virus infected cells?

Cytotoxic Tcells
Helper T cells
NK cells
Interferon

What are some innate immune responses to viral invasion?

Inflamation
Phagocytic cells (neutrophils, monocytes, macrophages)
Interferon
NK cells

What are some acquired immune responses to viral invasion?

T lymphocytes
B lymphocytes

What host proteins are involved in immune responses to viral invasion?

MHC class I and II proteins
Proteins that cleave endogenous antigens
Transporter associated with antigen presentation (TAP)
T cell receptor (TCR) proteins
T cell accessory molecules
Ig molecules

What are some ways that viruses can evade immune recognition?

Induction of immunosuppression
Induction of immune tolerance
Destruction of antigen presenting cells
Inhibition of recognition by antibodies

What are some ways that viruses can inhibit recogniton by CMI response?

Infection of cell lacking MHC class I antigen
Inhibition of MHC formation
Downregulation of viral protein expression
Induction of mutation in viral protein T cell epitopes

How can viruses induce an autoimmune disease?

Modulation of immune cells to present self antigens
Molecular mimicry

What are the stages of viral pathogenesis?

Absorption
Penetration
Uncoating
Transcription
Translation
Replication
Assembly
Release

What are some molecular determinants of viral virulence?

Envelope glycoproteins and capsid proteins
Viral polymerase and other proteins
Noncoding regions of viral genome

What are some mechanisms of viral virulence?

Modulation of host immune response
Modulation of growth factors and cytokines
Modulation of apoptosis
Disruption of intracellular Ca homeostasis
Production of reactive oxygen and nitrogen intermediates
Modulation of intracellular deoxynucleoside triphosphate pool

What are some ways that viral infections can persist for a long time?

Ability to infect host cells without being cytopathic
Integration into the host chromosomes
Inhibition of detection and elimination by the host immune responses

What factors can reactivate a herpesvirus infection?

Immunosupression
Stress
Hormonal changes
Nerve damage
UV exposure

What are some possible targets for antiviral action in the HIV replication cycle?

Binding
Reverse Transcriptase
Integration
Viral Gene Expression
Post-transcriptional Processing and Assembly
Budding or release

What type of vaccines are considered conventional vaccines?

Live virus (Wild or Attenuated)
Inactivated virus

What are some novel approaches to vaccine development?

Subunit vaccines (peptides)
Gene deleted vaccines
DNA vaccines
Virus vectored vaccines

What are some different strategies used to develop live wild-type virus vaccines?

Unnatural route
Unnatural host
Unnatural time of year

What are some different strategies used to develop live attenuated virus vaccines?

Naturally occurring variant
Gene reassortment
Heat mutated
Site-directed mutagenesis
Adaptation to natural host (animal passage and cell culture passage)
Using vectors

What are some different strategies used to develop Inactivated whole virus vaccines?

Cell culture
Animal tissue

What are some different strategies used to develop inactivated virus subunit vaccines?

Naturally occurring subunits
Detergent-split virus

What are some different strategies used to develop inactivated virus peptide vaccines?

In vitro chemical synthesis

What are some different strategies used to develop inactivated virus protein vaccines?

Recombinant DNA expression in bacteria
Recombinant DNA expression in yeast
Recombinant DNA expression in mammalian cells
Recombinant DNA expression in cell culture or insect cells
Recombinant DNA expression in heterologous virus

What term refers to the fact that protection is conferred on the unvaccinated in a population when a certain threshold number of individuals is vaccinated?

Herd Immunity

What is the study of the determinants, dynamics and distribution of disease in populations?

Epidemiology

What is the measure of disease frequency in a population over a specific period of time?

Incidence rate

What is the measure of disease frequency at a particular time?

Prevalence rate

What is the term for a virus that is infecting people worldwide?

Pandemic (Panzootic)

What are some different types of studies done to investigate causation of an epidemic?

Cross-section study
Case-control study
Cohort study

What are all the different modes a virus can be transmitted?

Horizontal
Direct contact
Indirect contact
Common vehicle
Airborne
Arthropod-borne
Vertical
Iatrogenic (accidental transmission by professionals)
Nosocomial (hospital-derived infection)
Zoonotic

What are some different ways of disease surveillance?

Notifiable disease reporting
Laboratory-based surveillance
Population-based surveillance

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