Viruses & Prions Flashcards
What are 5 differences between viruses and other microorganisms?
They’re non-living, small, an obligate intracellular parasite, contain either DNA or RNA (never both) and have minimal/no enzymes or ribosomes
Capsids are:
A protein coat composed of capsomeres surounding virions
The nucleocapsid contains:
Genetic information
What is a lipid envelope?
An outer layer surrounding the capsid in some viruses
Enveloped viruses are ____ easily inactivated by disinfectants
more
Glycoproteins/spikes can be found:
Inserted in either the capsid or envelope
The functions of glycoproteins are:
Cellular attachment and recognition of binding sites in host cells
Viruses usually have a specific ____ ____
host range
The 6 DNA viruses are:
Herpesvidrae, Poxviridae, Adenoviridae, Papillomaviridae, Parvoviridae, Hepadnaviridae
What are the three main steps of viral infection?
- Attachment and penetration into host cell
- Replication of the genome
- Assembly and release of new virus
What are the two methods of penetration for viral infection?
Fusion and pinocytosis
Enveloped viruses usually penetrate the host cell by ____
fusion
During penetration, the ____ and/or ____ is removed from the virus
envelope, capsule
Virus and its nucleic acids are released into the ____ upon penetration
cytoplasm
Describe how DNA viruses replicate in host cells
- Use the host cell’s DNA polymerase to produce viral DNA
- Occurs in nucleus
Describe how RNA viruses replicate in host cells
- Uses own RNA polymerase to produce viral RNA
- Occurs in cytoplasm
Describe how RNA retroviruses replicate in host cells
- Uses own reverse transcriptase in the capsid to produce viral RNA
Replicated viral RNA/DNA have new ____
nucleocapsids
If an enveloped virus, the envelope is ____ into the host cell’s plasma membrane and ____
inserted, buds
What are the 3 outcomes of infection?
Productive/acute, latent, and chronic infection
Describe productive/acute infections
- Virus replicates
- Produces virions
- Host cell often killed = lytic infection
Describe latent infections
- Viral genome persists but doesn’t replicate
- Provirus
- Herpes, HIV
Describe chronic infections
- Virus replicates without destroying host cell
- Persists for long period of time
What are the symptoms of acute infection for chickenpox
Fever, itchy rash on trunk and head
How is chickenpox transmitted?
Direct contact, droplet and airborne if scratched
For chickenpox, skin is always present in ____ stages of lesion
different
Describe latent infection of chickenpox
Virus is present in the ganglion, but not replicating, until triggered and reactivates
What are 2 complications of chickenpox?
Secondary bacterial infection and CNS disease
What are 2 methods to prevent chickenpox?
Active and passive immunization
Describe active immunization
- Live attenuated vaccine
- Highly protective, memory cells produced
Describe passive immunizations
- Effective up to 3 days post-exposure
- Mainly for immunocompromised and neonates
What is shingles/zoster?
Reactivation of chickenpox
What are the symptoms of shingles?
Skin rash (2-5 weeks) and pain
What is a complication of shingles?
Post herpetic neuralgia (PHN)
Describe PHN
- Pain persists from months to years
- Can cause permanent nerve damage
How to treat PHN?
Give antiviral (acyclovir) within 48-72 hours
Oncogenic virus can transform normal host cells into:
Cancer cells
What are the 2 methods in viral diagnosis?
Polymerase chain reaction (PCR) and culturing
What are prions?
Misfolded protein that act as infectious agents in susceptible animals
____ prion disease is always fatal
Human
What are the symptoms of human prion disease:
- Ataxia (losing balance)
- Cortical visual symptoms
- Dementia
- Myoclonus: sudden muscle jerks
- Akinetic mutism: inability to speak
What are the 4 antiviral drugs discussed in class?
Fuzeon, acyclovir, HAART (Highly active antiretroviral therapy), tamiflu
What is the function of fuzeon?
Stops fusion of HIV into cells
What is the function of acyclovir
Stops replication of herpes viruses by interfering with viral DNA polymerase
What is the function of HAART?
A combination of antiviral drugs for stopping the replication of HIV
What is the function of tamiflu?
Stops budding/release of influenza
For small pox, the skin is always present in ____ stages of lesion
identical
What are some examples of prion diseases?
Mad cow disease, scrapie in sheep, CJD & vCJD in humans
