Nature of Human Viruses Flashcards
T/F: Virus can’t get through a filter
False!
Viruses are filterable agents
Are viruses alive?
No, they are not considered alive
- they require a living cell to grow
How do viruses divide?
- infect a susceptible cell and take over cellular machinery
- do NOT divide via binary fission
T/F: Antibiotics/antifungals do NOT work on viruses
True!
- some antiviral agents are available but most viruses have no effective drugs
What is viruses genetic material?
RNA/DNA
- newly made particle= virions spread the virus to new cells
What is nucleic acid plus capsid called?
- nucleocapsids
What are the 2 viral capsids and what are their characteristics?
Helical capsids in human viruses:
- all negative RNA viruses
- all have enveloped viruses
- most are spaghetti like and not rigid
Icosahedral:
- can be enveloped or naked
- complex structure
- formed from viral capsid proteins with the nucleic acid inside
- can form spontaneously form once a sufficient amount of capsid protein is present
- can withstand stomach acid in some cases
- ex: HPV
There are 2 types of capsid structures. What are they?
- helical
which are all enveloped - icosahedral
which can be enveloped or naked
What does it mean for a naked virus?
- no lipid bilayer
- must be an icosahedral
What are viral envelopes derived from?
- infected cell membranes
Which type of virus (enveloped or naked) is more labile/easier to disrupt?
- enveloped are more fragile due to easy disruption of lipid bilayer making virus unable to enter
- naked viruses are more resistant stomach acid, detergents, solvents, heat, and drying agents and can be transferred through oral-fecal route
How are enveloped viruses are spread?
- respiratory droplets, blood, and sexual contact
- naked viruses can do all these things plus oral-fecal spread
What is required for viruses to infect?
- proteins need to recognize on the surface of the cell (lipid bilayer)
What does a neutralizing antibody do?
- prevent a virus from infecting cell
- recognize surface proteins on virion:
- for naked viruses: bind capsid proteins
- for enveloped viruses: bind envelope glycoproteins embedded in the lipid bilayer
What is the genome for positive single stranded RNA viruses?
- same sense as mRNA
- +ssRNA
What is the difference of negative sense RNA viruses (-ssRNA)?
- NOT like mRNA
- must use genome -ssRNA as a template to make mRNA
What is the root for family of virus?
- virdae
What virus has a segmented genome?
- BOAR viruses:
bunyavirus, orthomyxovirus, arenavirus, reovirus
What is a steady state virus-cell interaction?
- virus does not kill the cell but does produce virus
- non-cytocidal
- productive and non-cytocidal
What is a lytic-cytocidal virus-cell interaction?
2 types:
lytic:
- kills cell, cell death needed to release virus
cytopathic:
- kills cell by making it so sick but not needed to release virus
- productive and cytocidal
What is a latent virus-cell interaction?
- virus infects cells and doesn’t produce any virus but can reactivate
- ex: any herpesvirus
- nonproductive and noncytocidal
What is syncytial formation?
- infected cell fuses membranes of neighboring cells that are not infected to form large multinucleated cells
- a way for virus to spread to cells
T/F: Cell transformation by viruses is the same as bacterial transformation
False!
- if a virus can transform a cell, it’s more likely to cause cancer
- transforming a cell makes them immortal and able to grow on top of each other aka no contact inhibiton
What are the viruses that cause cancer?
- EBV (Epstein-Barr Virus)-Burkitt lymphoma, Nasopharyngeal carcinoma, oral hairy leukoplakia (in HIV infections)
- HPV (Human Papilloma Virus) – Cervical, Anal, and Oropharynx
- Human Herpes Virus 8-Kaposi’s Sarcoma (in HIV infections, immunocompromised)
- HTLV (Human T cell lymphotropic virus) Adult T-cell leukemia and lymphoma
- HBV (Hepatitis B virus)-Hepatocellular carcinoma
- HCV (Hepatitis C Virus)-Hepatocellular carcinoma
All DNA viruses are….
icosahedral
All -ssRNA viruses are (except coronavirus)…
helical
What viruses are linear ssDNA?
Parvovirus
What viruses are linear dsDNA?
Adenovirus, Herpesvirus, and Poxvirus
What viruses are circular dsDNA?
Papillomavirus and Polyomavirus
What viruses are circular mostly ds but small part is ssDNA?
Hepadnavirus
What viruses are +ssRNA?
Hepevirus, Picornavirus, Calicivirus, Togavirus, Coronavirus, Flavivirus, and Retrovirus
Retrovirus have +ssRNA but incorporate 2 strands of same RNA into virion
What viruses are -ssRNA?
Filovirus, Paramyxovirus, and Rhabdovirus
What viruses are segmented -ssRNA?
Arenavrius, Bunyavirus, and Orthomyxovirus
What viruses are segmented dsRNA?
Reovirus
What viruses are circular -ssRNA?
Deltavirus (HDV) but required Hep B virus to replicate
