Viruses Flashcards
How small?
28nm-200nm
How many types of nucleic acid?
One
Types of nucleic acid available in viruses
ss DNA, ds DNA, ss RNA, ds RNA
DNA viruses have what nucleic acid type?
ssDNa or ds DNA
RNA viruses have what nucleic acid type?
ssRNA or dsRNA
Retroviruses have what type of nucleic acid?
ssRNA
Hepadnaviruses have what type of nucleic acid?
dsDNA
Describe the structure of a virus
Protein coat (Capsid) made up of capsomeres which are units of the icosahedron
Nucleic acid core - two geomatric forms - Icosadehral or helical
Can have envelopes
Can have tails
Envelopes on viruses can..
produce immune response
Describe icosohedral structure
20 triangular faces, 30 sides, 12 vertices
Capsomeres: pentons or hexons
Very efficient protein expression as little/no waste of space
What is a bacteriophage? What is their structure like? What are they used for?
Virus of bacteria - helical structure - used to study bacterial genetics
How to culture bacteriophage viruses?
1) pour mixture of molten top agar, bacterial cells and diluted phage suspension onto a solidified nutrient agar plate
2) Let it solidify
3) Sandwich of top agar and nutrient agar forms
4) Incubate
5) Should have phage plaques and a lawn of host cells
How do viruses replicate?
1) Attachment (adsorption)
2) Penetration (injection) but protein coat remains outside
3) Synthesis of nucleic acid and protein
4) Assembly and packaging
5) Release (lysis)
6) Virions produced
Viruses need host cells because..
They do not have their own cellular machinery, i.e. they can’t make proteins or ATP or metabolise by themselves and hence are not living organisms
In order, what is produced when viruses try to replicate?
Eclipse: Early enzymes, nucleic acid, protein coats
Maturation: Assembly and release then occurs
How are viruses transmitted? Give an example of a specific virus for each method of transmission.
Respiratory - influenza A Faecal-oral - Enterovirus and Polio Blood-borne - Hepatitis B,C and HIV Sexual transmission - HIV Animal or insect vectors - Rabies virus, Zeka virus
What is a virus tissue tropism?
Its favourite place to effect
Which specific type of immune system cells detect HIV?
CD4+ cells
What acts as the receptor for poliovirus?
CD155
List some in vivo disease processes caused by viruses
cell destruction virus-induced changes to gene expression (eg HPV) Immunopathogenic disease (eg HIV)
Acute virus infections are…
localised to a specific site of the body
What is viraemia?
When the virus is in the blood. This can cause widespread infection of tissues
Properties of Influenza A virus?
- Myxovirus
- Enveloped virus
- Segmented RNA genome
- Infects a wide range of animals other than humans (pigs, birds etc)
- Undergoes extensive antigenic variation
- Major cause of respiratory infections
Describe an influenza A infection. How is it spread? Where does it infect?
Spread by respiratory route.
Virus infects cells of respiratory epithelium
Destruction of respiratory epithelium occurs, which may cause secondary bacterial infections
Altered cytokine expression leading to fever e.g. interleukin-1 and interferon
Retrovirus
HIV
Myxovirus
Influenza
Rhinovirus
Common cold
Reovirus
Various
Picornavirus
Polio
Herpesvirus
Varicell zoster and herpes
Paramyxovirus
Measles, rubella
Adenovirus
Tonsilitis
Poxvirus
Smallpox
List viruses controlled by current antiviral therapy
Cytomegalovirus (CMV) Hepatitis viruses Herpes viruses HIV Influenza viruses Respiratory syncytial virus (RSV)
Name some key characteristics of antiviral drugs
- able to enter the cells infected with the virus
- interfere with viral nucleic acid synthesis and/or its regulation
- some drugs interfere with ability of virus to bind to cells
- some drugs stimulate the body’s immune system
Best responses to antiviral drugs are?
In patients with competent immune systems as this works synergistically with the drug to eliminate or supress viral activity
Antiviral drugs treat
infections caused by viruses other than HIV
Antiretroviral drugs treat
Infections caused by HIV
HSV1 treats
Herpes Simplex Virus
Oral herpes
HSV2 Treats
Herpes Simplex Virus
Genital herpes
Medications for the varicella zoster virus treat
chickenpox and shingles
Amantadine (Symmetrel) is active against
Influenza A
Amantadine is used when?
Prophylatically when a vaccine is not available or cannot be given
Amantadine can reduce recovery time. Give the CNS side effects.
insomnia, nervousness, lightheadedness
Amantadine GI side effects?
anorexia, nausea etc
What type of drug is Acyclovir (Zovirax)
Synthetic nucleoside analog
Acyclovir suppresses the replication of which viruses?
HSV1, HSV2, VZV (Varicella)
What formulations of Acyclovir are available?
Oral, topical and parenteral forms
What are nonretroviral neuraminidase inhibitors (NNIs) used for?
Stopping the flu virus from replicating and to reduce the overall duration of illness.
Oseltamivir is a NNI with what side effects?
nausea, vomiting
Zanamivir is a NNI with what side effects?
diarrhoea, nausea, sinusitis
When should NNI treatment occur?
within 2 days of influenza symptom onset
What does HAART stand for? What is it?
Highly active antiretroviral therapy. It includes at least 3 medications and they work in different ways to reduce the viral load
What is an RTI drug? How do they work?
Reverse transcriptase inhibitors. Block activity of the enzyme reverse transcriptase, preventing production of new viral DNA
Give 3 types of RTI subclasses
Nucleoside RTIS (NRTIs) Nonnucleoside RTIs (NNRTIs) Nucelotide RTIs (NTRTIs)
Give examples of RTIs
Abacavir Didanosine Stavudine Delavirdine Lamivudine Tenofovir
