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
