Flashcards in Microbiology 7 - Viral disease Deck (26)
Are viruses bigger or smaller than bacteria?
What are the parts of a virus? (4)
Nucleic acidProtein coat (also known as capsid)Envelope (lipid - only some viruses)Protein spikes (only some viruses)
Do viruses contain RNA or DNA?
Either RNA or DNA (never both)
3 types of virus structure?
Icosahedral symmetry (made of 20 equilateral triangles) e.g. adenovirusHelical symmetry (made up of a single repeated unit that aggregate around the viral nucleic acid)Complex virus structure
How do viruses infect a cell? (6)
-The virus attaches to a cell receptor via a ligand (protein spike)-The virus enters the cell (either by endocytosis (if the virus doesn't have an envelope) or by fusion of viral and cell envelope mediated by viral enzymes (if the virus has an envelope)-Uncoating of the virus (viral nucleic acid is released from the capsid)-Nucleic acid and protein synthesis (host ribosomes are always used and some viral enzymes are used to build new proteins and nucleic acid from instruction in the original nucleic acid)-Assembly of assembling virus within cell-release of newly formed virus (several different mechanisms)
During the assembly stage what may be seen down the light microscope?
Crystals of assembling virus - inclusions
Mechanisms by which newly formed viruses within a cell can be released?
Budding (part of the cell membrane is napped off to produce a virus with an envelope around it)Lysis (virus accumulates until it causes lyses of the cell and release of virus)
Is the host cell killed by budding?
Is the host cell killed by release of virus via lysis?
Why do antibiotics not work on viruses?
Antibiotics work by being selectively toxic to certain bacterial structures (e.g. ribosomes, cell wall) which viruses do not have
What are the possible targets of antiviral drugs?
Viral nucleic acid polymerasesOther viral enzymes involved in viral nucleic acid replication or protein synthesis e.g. integers, proteaseUncoatingAttachement/ entryrelease
What is another type of therapy (apart from antiviral drugs) that can be used to treat viruses?
What is an example of an anti-flu antiviral?
How does a virus cause illness? (3)
Cell death due to lysis or hijacking of cell machineryCell death due to the immune system (especially cytotoxic T cells)Cell proliferation (e.g. wart causing virus infects skin cells and causes them to proliferate - can lead to cancer)
What type of cancer can hepatitis B and C viruses cause?
Primary hepatocellular carcinoma
What type of cancer can Human herpes virus type 8 cause?
What type of cancer can helicobacter pylori cause?
What type of leukocyte can recognise proteins on the cell surface as being foreign and will signal the infected cell to commit suicide to prevent the formation of further mature virus?
Cytotoxic T lymphocytes
What can bind directly to viruses to prevent them binding to cellular receptors?
Antibodies e.g. IgG, IgM
What makes you feel so unwell when you have influenza?
The virus induces interferon release which makes you feel ill
What are interferons?
a group of signaling proteins made and released by host cells in response to the presence of several pathogens
What can happen to viruses in terms of being eliminated from the body?
-Virus can be eliminated by the immune system-Some viruses may become quiescent (latent) with the possibility of reactivating e.g. herpes simplex virus, varicella-zoster virus-The virus may remain continually active for years causing chronic infection e.g. HIV and hep C (these patients may remain asymptomatic but infectious for decades before getting life threatening complications)
How are virus infection confirmed in the laboratory?
Either by detection of the antibody response against the virus (antigen detection)By detection of the presence of the virus itself (PCR)(older techniques include cell culture and electron microscopy)
what is the incubation period?
The period between exposure to an infection and development of symptoms
Out of IgM and IgG, what never fully disappears from the blood stream after infection?