(6-14) Viruses Of Animals Flashcards
1. Define virus and describe the composition of a virus. 2. Differentiate between “naked” and enveloped viruses and between phage and animal viruses. 3. List the criteria for classifying animal viruses based on their physical characteristics. 4. List the groups of animal viruses based on routes of transmission. 5. Describe in the proper sequence what occurs in viral replication in animal cells. 6. Describe how and where viral proteins are made. 7. Identify the event in which an envel
Describe the two items that constitute the nucleocapsid.
- Protein capsid
~ made of capsomeres - Nucleic Acid
~ ss or ds DNA (or)
~ ss or ds RNA
What is the (optional) viral envelope composed of?
The envelope is a lipid membrane derived from the infected host cell plasma membrane.
How do viruses attach to host cells?
Attachment to host cell is via protein or glycoprotein spikes.
What are the 4 attributes animal viruses can be classified by?
- Genomic structure
- Virus particle structure
- Presence or absence of envelope
- Route of transmission
Describe animal virus genomic structure.
- DNA or RNA
- ss or ds
- Single molecule or segmented (more than one nucleic acid molecule)
Describe the 3 possible structural shapes an animal virus particle may be found in.
- Isometric
- Pleomorphic
- Helical
[Animal Viruses do not occur in the complex Teleform of T4 phage.]
Name 4 routes of transmission that animal viruses may be classified by.
- Enteric
- Respiratory
- Zoonotic
- Sexually-transmitted
How are enteric viruses generally transmitted?
Via fecal-oral route.
Name 2 presentations of enteric viruses. Which is most common?
- Gastroenteritis– more common
- Systemic disease
What is rotavirus’ route of transmission?
Enteric
What is poliovirus’ route of transmission?
Enteric
How are respiratory viruses specifically transmitted?
They’re usually inhaled via infected respiratory droplets.
What is the influenza viruses route of transmission and where does it generally remain located within the host’s body?
Influenza virus uses respiratory transmission and generally remains located in the respiratory tract.
What is the term for a virus that is transmitted from an animal to human (or to another animal)?
Zoonotic
What is the term given to a zoonotic virus that is transmitted via arthropod? Give one example.
Arbovirus
~ ex. West Nile Virus
Name 2 presentations of sexually-transmitted viruses. Cite one example of a sexually transmitted virus.
- Lesions on genitalia
- Systemic infections
~ ex. HIV
Are host interactions of viruses simple or complex?
Complex
How do outcomes of infection differ between bacteriophages and animal viruses?
- For bacteriophages, outcome of infection depends only on phage and bacteria.
- For animal viruses, outcome of infection can be influenced by cells other than host.
What type of host cells can influence animal virus outcomes?
Immune cells
What two categories are infections divided into, based upon disease and state of virus and host?
- Acute
- Persistent
How can an acute infection be described?
Short-lived, but severe (productive)
How can persistent infections be described?
Infection established for years or life; may or may not have disease symptoms.
What do acute infection disease symptoms result from?
Tissue damage and infection of new cells
Give 4 examples of acute animal infections.
- Mumps
- Measles
- Influenza
- Polio
What is the typical timeframe for a host’s defense mechanism to eliminate an acute (animal) viral infection?
A period of days to months
What do productive, acute animal infections produce?
Large numbers of viruses during replication
What are the 8 steps of acute infection by animal virus?
- Attachment to receptor on host cell
- Entry into susceptible cell
2a. Uncoating of virion
~ Removing protein coat exposing nucleic acid - Transcription
- Replication
- Maturation
- Release
- Spreading within host
- Shedding and transmission to other hosts
How does HIV attach to CD4 and CCR5?
With spikes
What are the 3 ways acute animal viruses gain entry into a susceptible cell?
- Fusion
~ All naked viruses enter by Fusion - Endocytosis
What 2 ways do viruses leave their host cell?
- Cell lysis
- Budding
What are the possible effects of budding on the host cell?
- Kills cell
- Cell lives
How does HIV kill its host cells?
HIV kills host cell as buds
What type of viral release from host cell is associated with a persistent infection?
Budding, in which the host cell survives.
What are the 3 steps of budding?
- Viral proteins that are to become spikes of virus attach to host plasma membrane.
- Viral matrix protein coats insie of plasma membrane.
- Nucleocapsid becomes enclosed by viral envelope which is composed of the host’s plasma membrane.
[Budding is complete and plasma membrane remains intact.]
What 3 categories can viruses be divided into, based upon detection of virus during period of persistence?
- Latent infections
- Chronic infections
- Slow infection
When viruses are continually present in host
and release from infected cell via budding, it is termed a _________ infection.
Persistent
In which type of persistent infection is an infectious virus not detected until reactivation?
Latent infections
In which type of persistent infection can infectious virus can be detected at all times?
Chronic infections
In which type of persistent infection does infectious virus gradually increases in amount over long period of time?
Slow infections
Herpes Simplex Type 1 a ________ infection.
Latent
When are Herpes Simplex Type 1 infectious particles detected?
Reactivation
In Herpes Simplex Type 1 virus, are symptoms of reactivation and initial disease similar or different?
They MAY differ
The acute initial phase of HSV-1 presents with what 2 symptoms?
- Cold sores
- Fever
[sometimes symptomless]
When HSV-1 infects the sensory ganglia of the trigeminal nerve, what is the resulting viral state?
HSV-1 is repressed (for years)
What does HSV-1 reactivation present as?
Cold sores
What type of infection is Hepatitis B?
Chronic (latent)
How many people carry the Hepatitis B virus?
300 M
What 3 ways are Hepatitis B spread?
- Blood products
- Saliva
- Semen
Which disease Infects liver cells and can lead to liver failure in 1-10% of cases?
Hepatitis B
In the chronic infections, Hep B and C, when is the infectious disease released, and what are the symptoms?
- After initial infection, with or without symptoms
- No symptoms
Which 2 groups of infectious agents cause slow infections?
- Retroviruses
~ including HIV - Prions
Which type of infection features Infectious agent gradually increases in amount over long period of time?
Slow infections
In which 2 ways can viruses can alter their properties?
- Mutation
- Genetic reassortment
What type of virus can multiply in widely divergent species? Cite one example.
Zoonoses
~ ex. West Nile Virus infects birds or humans through mosquito vectors
What type of genetic shift are pandemics caused by?
Antigenic shift
How many RNA segments does the influenza virus have?
8
What is the importance of hemagglutinin in the influenza virus?
Hemagglutinin is a key protein involved in attachment to host cells. If the structure of it changes, influenza antibodies can no longer recognize the protein. Hence, they cannot fight the virus.
How does hemagglutinin interact with the ciliated epithelia of the lower respiratory system?
Hemagglutinin forms the influenza spike, which attaches to the sialic acid on the cell.
Which type of mutation can change the hemagglutinin of an influenza virus slightly?
A point mutation, resulting in antigenic drift
If human and avian influenza were to simultaneously infect the same cell (ex. pig or duck) and accidently intermix their RNA, what might result?
The avian hemagglutinin may bond with the other 7 segments of human influenza RNA, resulting in a human influenza virus that humans cannot fight. [Antigenic shift.]
