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Virology

Virology morphology

QuestionAnswer
What is the avg size of a virus? 20-300nm in diameter
Why are viruses filterable? Because they pass through micropore filters
What are the 3 morphologies of viruses? cubic, helical and complex
What type of viruses are ether sensitive? enveloped
Why are viruses obligatory intracellular parasites? because they have a limited genome and need the host cell’s hardware
Can viruses infect any type of host? No, only permissive host. Not non-permissive
Why do some viruses need a helper virus? because they are defective and require a co-infection
Where is the viral genome encoded into? capsid
What is the capsid made of? proteins called protomers or capsomeres, some viruses (e.g. HIV) derive from pro-peptides by protease activity How do you stop protease activity?
What is a nucleocapsid? protein-nucleic acid complex
How are the capsid assembled in helical vs icosahedral symmetry? by assembling the capsid on the nucleic acid vs independent of it the icosahedral (can cause defective virus)
Where can the envelope of a virus be derived from in a host? cell membrane, nuclear env or golgi while “budding” out
What kinds of proteins are on the surface envelope of a virus? glycoproteins
What is the function of glycoproteins? They are viral attachment proteins (VAP’s) e.g. gp120 on virus bidns CD-4 receptors in TH cells
What are the 4 stages of cell infections? 1. Recognition, 2. penetration, 3. uncoating, 4. synthesis and propagation
What is tropism? tissue specificity in viral infections due to receptors
How do glycoproteins appear on the cell? as spikes or peplomeres
How does ether act on envelopes? it disrupts their lipid rich envelope
What are hemaggluttins (HA’s)? (VAP) Viral attachment proteins that bind RBC’s
What do HA’s of orthomyxoviruses (influenza) bind? the terminal sialic acid (neuramic), released by neuramidases
What are fusion inhibitors? inhibit interaction of VAP’s with target cell
How do non-enveloped viruses penetrate the cell? via receptor mediated endocytosis or viropexis, done by hydropobically permating through(slipping by)
How do enveloped viruses penetrate the cell? By fusion, of viral envelope with the cell membrane
Where do RNA and DNA viruses replicate? RNA in the cytoplasm and most DNA in the nucleus
Which DNA or RNA viruses are known as tumor viruses? DNA= Herpesviridae(EBV- burkitts lymphoma), Papilomaviridae(papilloma virus – cervical cancer), poliomaviridae, adenoviridae, hepadnaviridae (HBV-hepatomas) and RNA = retroviridae (can cause tumor).
What are the 4 groups of RNA genome? ss +ve sense (mRNA like, fast, no RNA-P), ss –ve (antisense, not fast, use as a template for +ve strand, uses viral RNA-P) dsRNA (segmented) viruses, retroviruses (2 copies of +ve ssRNA)
Which type of RNA functions as an mRNA? +ve sense
Which RNA type does not contain RNA dependent RNAP and why? +sense, because it is already used as an mRNA and it can make proteins
Which RNA type cannot infect when purified? -ve sense RNA
Which RNA is there an mRNA capping segmented dsDNA
What is reverese transcriptase? RNA dependent DNA polymerase
What particles are packed in retroviruses? Reverse transcriptase, RNase H, protease, integrase enzymes and ssRNA genome(2copies)
After RNA is copied to DNA the hybrid what does RNase H Do? replace the other strand with DNA
What is a provirus? In Retroviruses when the final form is obtained DNA-DNA strand
What do integrase enzymes do? introduce retroviral DNA into the host DNA
Besides Retroviruses with oncologic genes, is there any other type of RNA virus capable of forming tumors? yes, lentiviruses
What happens in DNA viruses? Virus uncoats, dNA enters the nucleus, it is then transcribed to mRNA and viral proteins are made.
What do early genes in DNA viruses do? transcribe regulatory proteins
What do late genes in DNA viruses do? make proteins for replications and capsid packaging
What is an arbovirus? it is acirus that has arthropod vectors such as mosquitoes or ticks to transmit to a vertebrate host
What are some arboviruses? dengue, yellow fever, encephlatis
What are some of the families that the arboviruses belong to? togaviridae, flaviviridae, bunyaviridae, rhabdoviridae, arenaviridae, reoviridae.
What are the 3 genes in arboviruses and wha they code for? 1. gag - capsid, 2. pol – reverse transcriptase, Nuclease(RNaseH), integrase and protease, 3. env – envelope glycoproteins
What are prions made of? Not viruses, it is a mutantprtoeins with particles made of a single protein, without nucleic acid.
What are prions resistant to? Formaldehyde, heat, uv, nucleases and somewhat protease resistant
What do prions Do? Create a wild type protein misfold
What is an amyloid? Is when prions expose the hydrophobic part of protein causing it to agglutinate and pile up in the nerve cells.
What causes transmissible spongioform disease and why is it called that? prions cause it and it is because the infected cells have a vacuolated appearance
What is the gene that causes the misfold, and what protein is made? PrPc is the gene and PrPsc is the protein made
What animal is affected by scrapie? sheep
What animal is affected by mad cow disease (bovine spongioform disease)? Cattle
What animal is affected by Kuru and Creutzfeldt Jacob Disease ? Humans
Where are viruses cultured? in embryonated chicken eggs, primary cell cultures and permanent cell lines
Why are viruses cultured? to make vaccines
Why do some people need to check for allergies to a vaccine? chicken protein contaminants may be present and can trigger a reaction
What are methods of viral Quantitation and titration(physical methods)? PCR, RIA, ELISA, electron microscopy
What are The biological methods of viral detection? Animal death, infection, cytopathic effects including plaque assays
Whar are the cytopathic effects that help in virus detection? presence of cell lysis, necrosis, syncytial formation, giant cell formation, inclusion formation, vacuolization
What is inclusion and how are they detected? Inclusions are indicatory of rabies and they are detected by taking up eosin stain
How do you detect viral specific proteins? by ELISA, RIA, Western Blot
How is influenza detected? by a hemagluttinin assay
What does PCR help you detect? virus-specific nucleic acid
What are the means of laboratory infection? aerosols, ingestion, skin penetration and eye splashes
What are some methods of laboratory safety? training aseptic techniques, no mouth pipetting, no eating/drinking/smoking in lab, protective gear, sterilization of wastes, hoods, immunizations, level 4 facility conatinent of high risk viruses(e.g. ebola and rabies).
What morphology of viruses is stable at 37C? icosahedral
Are enveloped viruses more heat labile(change)? Yes
Most viruses are inactivated at 50-60C except for? Polyoma, HBV and prions
What temperature can most viruses be stored? -80C
What temperature can viruses be lyophilized (dehydrated)? at 4C or RT
What happens to enveloped viruses at 90C? lose infectivity, and they are sensitive to freezing and thawing
What do salts do to viruses and how doe sit affect shelf life? stabilizes them, for this reason why vaccine preparations contain salts to increase shelf life
What salt stabilizes picornaviruses and reoviruses? MgCl2
What salt stabilizes herpesviruses? Na2SO4
What pH are most viruses stable? Between 5-9
Are enteric viruses stable at low pH? Yes
What does very high pH do to viruses? kills all of them
What does UV light and y Radiation do to viruses? inactivates them they can’t replicate
How does photodynamic inactivation work? toluidine blue, neutral red or proflavine are absorbed by nucleic acids in the virus, making them sensitive to light
Which virus are feature of the virus makes them ether sensitive? envelope
What detergents are used to inactivate enveloped and non-enveloped viruses? enveloped = Nonidet (NP40) and Triton X-100. Non-enveloped= SDS
Why is formaldehyde a great inactivation agent for vaccines? it interacts less with protein and does not reduce antigenicity, it attaches better to single strand than double strand nucleic acids
What is recombination? viruses can interchange DNA to create a new mutant virus, lot of variability in segmented RNA (e.g. influenza)
What is complementation? when 2 viruses on the same host cell can complement each other by transactivation
What is interference? when one virus inhibits the replication of another in the same host
What virus could be used for gene transfer in mammalian cells for gene therapy? retrovirus and certain DNA viruses(adenovirus)
Why retroviruses for gene therapy? They have 2 copies and can permanently leave one in the host, used to replace defective genes, but the oncogenes need to be removed, the only down is that retrovirus may recombine with other viruses making it oncogenic
What is the major route of transmission of viruses? aerosols and dropplets
What viruses are transmitted by aerosols and droplets influenza, measles, smallpox etc.
What viruses are transmitted by fecal-oral route? enteroviruses, polio, rotaviruses, HAV
What viruses are transmitted by sexual contact? HBV, HSV2, HIV1 and 2
What viruses are transmitted by hand-mouth/eye and mouth-mouth? HSV1, EBV, Rhinovirus
What viruses are transmitted by blood exchange? HIV, HBV
What viruses are transmitted by animal to animal with human as an accidental host? rabies(dog), aerosols (rodents) arenaviruses and hantaviruses
What viruses are transmitted by arthropod vectors (e.g. mosquitos and fleas)? arboviruses – togaviruses, flaviviruses and bunyaviruses
What is the transmission pattern of human-arthropod? urban yellow fever, dengue
What is the transmission pattern of lower-vertebrate anthropod with tangential human infection? Jungle yellow fever, st. Louis encephalitis
What is the transmission pattern of arthropod-arthropod with accidental human? Colorado tick fever, LaCrose encephalitis
Why are arthropods a good vector? because they are not affected in any way by the virus
What are the routes of entry for viruses? Skin, GI, Respiratory tract, UG system or eye, fomites(needles)
What are the 2 most popular route of entry respiratory tract and GI
Do some viruses only infect locally? yes, e.g. influenza, parainfluenza only infects respiratory tract
How do some viruses spread systemically? Via viremia or the lymphatic system
How can viruses replicate ate the point of entry ? yes, and then they spread through the body including the CNS according to tropism
Can viruses remain latent in the body? Give an example? yes, e.g. herpes remains latent in trigeminal ganglia or sacral ganglia this is a chronic infection
What salt stabilizes orthomixoviruses and paramixoviruses? MgSO4
What salt stabilizes herpesviruses? Na2SO4
Created by: studypharm