Virology 1 Flashcards
Viruses—A Little History
- Virus—Latin word meaning “___”
- Late 1800’s o Charles Chamberland in Pasteur’s lab made a filter that would hold back the ___ ___.
o Iwanowski (Russia) and Beijerinck (Holland) showed that a plant infection (___ ___ disease) could be transmitted by ____ that passed through Chamberland filter.
• Something smaller than the smallest bacteria that was known about back then
o ___ and ___ disease of cattle was also transmitted by bacteria-free filtrates.
o ____ seen with light microscope. • Largest of all the viruses
• 1928-1950’s
o Virus was grown in suspensions of minced ____ tissue.
o Virus was grown in developing __ ___.
o Discovery of antibiotics inhibited ____ of cell and tissue cultures. • So you could study viruses without contamination of bacteria
o Electron microscope developed (1939) and ___ of viruses was delineated.
• 1953—Watson and crick described the structure of DNA
Viruses—A Little History • Virus—Latin word meaning “poison” • Late 1800’s o Charles Chamberland in Pasteur’s lab made a filter that would hold back the smallest bacteria. o Iwanowski (Russia) and Beijerinck (Holland) showed that a plant infection (tobacco mosaic disease) could be transmitted by extracts that passed through Chamberland filter. • Something smaller than the smallest bacteria that was known about back then o Foot-and-mouth disease of cattle was also transmitted by bacteria-free filtrates. o Poxviruses seen with light microscope. • Largest of all the viruses • 1928-1950’s o Virus was grown in suspensions of minced kidney tissue. o Virus was grown in developing chick embryos. o Discovery of antibiotics inhibited contamination of cell and tissue cultures. • So you could study viruses without contamination of bacteria o Electron microscope developed (1939) and morphology of viruses was delineated. • 1953—Watson and crick described the structure of DNA
Properties of Viruses
- Size: ___ nm to __ __ nm
- ___ ____ parasites
- Do not produce ___ or ___
- Genome is either ___ or ____
- Morphologic types • __ ___• ____
- Assembled from components
Properties of Viruses • Size: 20 nm to several hundred nm • Obligate intracellular parasites • Do not produce energy or proteins • Genome is either DNA or RNA • Morphologic types • Naked capsid • Enveloped • Assembled from components
Viral Classification—Symmetry
- ____ o Capsid is ___ ___ ___
- Enveloped with helical nucleocapsid (influenza virus) o Envelope wrapped around ___ __ ____ o Contains important structures for ____ of other cells
- ____ symmetry o ____ faces o Genome is encapsulated in there
- Enveloped with icosahedral nucleocapsid (herpesvirus)
- ____symmetry (poxvirus): Doesn’t match any other viral structures
Naked or Enveloped and then Helical or Icosahedral
Viral Classification—Symmetry • Helical o Capsid is wound around genome • Enveloped with helical nucleocapsid (influenza virus) o Envelope wrapped around host cell membrane o Contains important structures for infection of other cells • Icosahedral symmetry o Pentagon faces o Genome is encapsulated in there • Enveloped with icosahedral nucleocapsid (herpesvirus) • Complex symmetry (poxvirus): Doesn’t match any other viral structures Naked or Enveloped and then Helical or Icosahedral
Virus Classification—Type of Nucleic Acid
- Its either DNA or RNA but its __ ___
- Classified based on whether you ___ with DNA or RNA • No matter what you start with you need mRNA to make protein • _strand or _ strand
Virus Classification—Type of Nucleic Acid • Its either DNA or RNA but its not both • Classified based on whether you start with DNA or RNA • No matter what you start with you need mRNA to make protein • + strand or - strand
Virus Properties
- naked capsid Ex) Polio
- ___ coat • Subunits of protein coat called____
- environmentally ___ • temperature • acid • proteases • detergents • drying
- generally released by __ ___ • Infect cell. turn it into viral making cell. Viral prodcuts build up in cell and it bursts.
Virus Properties • naked capsid Ex) Polio • protein coat • Subunits of protein coat called capsomeres • environmentally stable • temperature • acid • proteases • detergents • drying • generally released by cell lysis • Infect cell. turn it into viral making cell. Viral prodcuts build up in cell and it bursts.
- enveloped
- ___ layer
- Derived from ___ ___ ____
- Just like the cell membrane
- ____ • Envelope similar to host cell membrane
- ____ made from virus • It will insert these into its envelope
- ____
- Environmentally ____ • Don’t survive very long outside of a cell in which they can replicate
- __ ___ modifications • They make modifications to the cell membrane
- Released by ________ • Budding one at a time • Many use combo of these two approaches
• enveloped • outer layer • Derived from host cell membrane • Just like the cell membrane • Lipids • Envelope similar to host cell membrane • Glycoproteins made from virus • It will insert these into its envelope • proteins • Environmentally labile • Don’t survive very long outside of a cell in which they can replicate • Cell membrane modifications • They make modifications to the cell membrane • Released by budding and cell lysis • Budding one at a time • Many use combo of these two approaches
Steps in Viral Replication
1-7
Steps in Viral Replication 1. Absorption 2. Penetration 3. Uncoding 4. Tx 5. Tlation 6. Assembly 7. Release
Virus Families
More ___ virus families than DNA virus families
Grouped based on their ___
Virus Families More RNA virus families than DNA virus families Grouped based on their structure.
Cytopathic Effects of Viruses: What do we see in viral infected cells
- ___ ___ o Sites of virus assembly are taking place in cytoplasm o ___ viruses typically replicate in cytoplasm
- ___ ___ o Viruses that are ___ viruses replicate in the nucleus
- Cytoplasmic/Nuclear Inclusions
- ___
- ____ ____ o Form giant cells
- ____ o Virus can cause cells to become transformed, replicate uncontrollably • Associated with cancer
Cytopathic Effects of Viruses: What do we see in viral infected cells • Cytoplasmic Inclusions o Sites of virus assembly are taking place in cytoplasm o RNA viruses typically replicate in cytoplasm • Nuclear Inclusions o Viruses that are DNA viruses replicate in the nucleus • Cytoplasmic/Nuclear Inclusions • Lysis • Multinucleated Syncytium o Form giant cells • Transformation o Virus can cause cells to become transformed, replicate uncontrollably • Associated with cancer
Effects of Viruses on Host Cells
- Virus enters the host cell • It can go two ways depending on cell type. • Viruses have different tropisms for different cells
- 1) ____ infection: o virus replicates in the cell and __ __→____ infection.
- 2)____ infection: o virus gets into a cell in which it ___ ___ but it can carry out a few fcns (make some early gene products)→____ Infection.
- ___: Small amts of virus are released overtime. • Never completely cleared by the body
- ___: Virus sits quietly in cell and then something triggers it to replicate • Symptoms aren’t as bad subsequent times
- ____: leads to cancer
- ____: virus at low level with no signs or symptoms • After long period of time then the signs and symptoms will occur
Effects of Viruses on Host Cells • Virus enters the host cell • It can go two ways depending on cell type. • Viruses have different tropisms for different cells • 1) Permissive infection: o virus replicates in the cell and kills it→cytocidal infection. • 2) Nonpermissive infection: o virus gets into a cell in which it can’t replicate but it can carry out a few fcns (make some early gene products)→Persistant Infection. • Chronic: Small amts of virus are releasedovertime. • Never completely cleared by the body • Latent: Virus sits quietly in cell and then something triggers it to replicate • Symptoms aren’t as bad subsequent times • Oncogenic: leads to cancer • Slow: virus at low level with no signs or symptoms • After long period of time then the signs and symptoms will occur
Determinants of Viral Disease
Nature of disease
- ___ ___
- ___ of ___
- Virus ___ to ___ ___
- Tissue ____ of virus
- Cell ____ for virus ____
- Viral ___ (___)
What determines what will happen once you are infected with a virus
Determinants of Viral Disease Nature of disease • Target tissue • Portal of entry • Virus access to target tissue • Tissue tropism of virus • Cell permissiveness for virus replication • Viral pathogen (strain) What determines what will happen once you are infected with a virus
Severity of disease
- ___ ability of virus • How easy to cause destruction of cells
- ___ status • ____ • Prior ___
- _______→Inclusion bodies
- ___ of ___ ___
- ___ to_____ of infection • Longer it goes on, the more severe it is
- General ___ of person • Nutrition • Other diseases
- __ __ of person
- ___
Severity of disease • cytopathic ability of virus • How easy to cause destruction of cells • Immune status • Competence • Prior immunity • Immunopathology→Inclusion bodies • Size of virus inoculum • Time to resolution of infection • Longer it goes on, the more severe it is • General health of person • Nutrition • Other diseases • Genetic makeup of person • Age
Mechanisms of Viral Cytopathogenesis
- Inhibition of cellular ___ ___
- Inhibition and degradation of cellular___
- Alteration of ___ ___: ____ insertion, ____ formation, disruption of ____, _____
- ____ bodies
- ____ of virion components
Mechanisms of Viral Cytopathogenesis • Inhibition of cellular protein synthesis • Inhibition and degradation of cellular DNA • Alteration of cell membrane: Glycoprotein insertion, Syncitia formation, disruption of cytoskeleton, permeability • Inclusion bodies • Toxicity of virion components
Viral Pathogenesis—Initiation of Infection
- ___ ___ must be able to initiate infection.
- Cells at the site of infection must be ____, ___ and ____ for the virus.
- Local host ____-___l defense systems must be __ or ___ ____. • Ex) sIgA
- Viruses can get into any opening in the human body. They can also shed from those sites.
Viral Pathogenesis—Initiation of Infection • Sufficient virus must be able to initiate infection. • Cells at the site of infection must be accessible, susceptible, and permissive for the virus. • Local host anti-viral defense systems must be absent or initially ineffective. • Ex) sIgA • Viruses can get into any opening in the human body. They can also shed from those sites.
Diagnosis of Viral Disease
- ___ and ____ provide first clues; often allow ___ of bacterial and fungal infections
- laboratory studies are done to:
- ___ the clinical diagnosis by ____ the virus • Maybe you can trt it depending on the virus • define the disease process
- allow ____ ____. Many viruses have to be reported to the centers for disease control
- methods
- ___/___
- ___ ___
- ___ ___
- _____/____ /____ • Using Antibodies to identify infection
- detection of viral ___ ___→PCR
- ____ • Look in serum for Ab to the virus
Diagnosis of Viral Disease • history and symptoms provide first clues; often allow exclusion of bacterial and fungal infections • laboratory studies are done to: • confirm the clinical diagnosis by identifying the virus • Maybe you can trt it depending on the virus • define the disease process • allow epidemiologic monitoring • Many viruses have to be reported to the centers for disease control • methods • cytology/histology • electron microscopy • cell culture • immunohistochemistry/immunofluorescence/immunoassays • Using Antibodies to identify infection • detection of viral nucleic acids→PCR • serology • Look in serum for Ab to the virus
cytology/histology • ___ • Many nuclei in one cell • ___ ___ • ______s→ HPV infection
electron microscopy • ___ ___ stain of specimen • immunoelectron microscopy
growth in cell culture • Inoculation of ____cells
detection of viral proteins • ____ & immunohistochemistry • Fluorescent or enzyme labeled ___
detection of viral nucleic acids • ___• Gel Electrophoresis to detect amplified DNA • Real time PCR
Immunoassays Like a pregnancy test
serology • Detection in patient serum
cytology/histology • Syncytia • Many nuclei in one cell • inclusion bodies • koilocytosis→ HPV infection electron microscopy • direct negative stain of specimen • immunoelectron microscopy growth in cell culture • Inoculation of susceptible cells detection of viral proteins • immunofluorescence & immunohistochemistry • Fluorescent or enzyme labeled Ab detection of viral nucleic acids • PCR • Gel Electrophoresis to detect amplified DNA • Real time PCR Immunoassays Like a pregnancy test serology • Detection in patient serum
Interferon–Induction of the Anti-Viral State
• Functions
o inhibition of ___ ___
o inhibition of ___ ___
o ______
• Types (Have different sources)
o α-interferon—___ interferon
o β-interferon—___ interferon
o γ-interferon—activated ___ cells and __ cells
- IFN is important for fighting viral infections
- Virus gets in the cell and induces production of ___
- ___ ____ NA are better at inducing IFN
- Cell dies from viral infection and IFN is ____
- IFN will signal
o uninfected cells to destroy the ___ and reduce __ ___ • So virus can produce protein in the cell
o ____ of infected cells
o Activation of ____ cells
• Alpha and Beta produced in response to ___ infection and then Gamma comes in to ____
Interferon–Induction of the Anti-Viral State • Functions o inhibition of viral multiplication o inhibition of cell division o immunomodulation • Types (Have different sources) o α-interferon—leukocyte interferon o β-interferon—fibroblast interferon o γ-interferon—activated T cells and NK cells • IFN is important for fighting viral infections • Virus gets in the cell and induces production of IFN • Ds NA are better at inducing IFN • Cell dies from viral infection and IFN is released • IFN will signal o uninfected cells to destroy the RNA and reduce protein syn • So virus can produce protein in the cell o Apoptosis of infected cells o Activation of immune cells • Alpha and Beta produced in response to viral infection and then Gamma comes in to fight
New Test for Viral Infections
- ___ ___ ____ ___
- Use ___ ___ to express proteins of wide variety of viral proteins
- See persons ____ to wide variety of viruses
New Test for Viral Infections • Systemic viral epitope scanning • Use bact viruses to express proteins of wide variety of viral proteins • See persons immunity to wide variety of viruses
Antivirals
- most viral diseases, except HIV disease, are ___ ___ and do not require treatment
- current antivirals target ____viruses, ____ viruses (B and C), ____ viruses, ____syncytial virus and ___
- field is rapidly evolving as viruses become ___ to ___ ___
Antivirals • most viral diseases, except HIV disease, are self-limited and do not require treatment • current antivirals target herpesviruses, hepatitis viruses (B and C), influenza viruses, respiratory syncytial virus and HIV • field is rapidly evolving as viruses become resistant to older drugs
