Viral infection Flashcards by Lstudy123 Emm

how big are viruses?

very small, non cellular microbe
10-200 nm

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what is composition of virus particle?

nucleic acid genome(DNA or RNA)
protein shell (capsid)
sometimes lipid layer (envelope) = acquired from cells they exit from. associated with virus proteins

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how do virus spread/grow?

replication (unique)
= virus genome directs synthesis of virus proteins & progeny virus genomes using cellular machinery

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how do virus components form virus particles?

virus components produced by the host cell are assembled into
progeny virus particles

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what does obligate intra-cellular parasite mean?

small and relatively simple microbes that cannot grow outside of living cells. dedicated to carrying out pathogenic life-cycle (doesn’t have capacity to carry out by itself)

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what are examples of respiratory viruses?

SARS-CoV-2 (covid)
Influenza

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what is example of GI tract virus?

norovirus

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what is examples of blood borne viruses?

HIV and hepatitus

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how do genomes of different viruses vary?

chemistry - RNA or DNA
structure - double stranded, single stranded, linear, circular
size - 3500 bases to 330 000 base pairs

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what is role of protein caspid?

protects the genome from environement
-delivers genome to cell (has proteins that target cells to infect)

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what is virus envelope?

lipid bilayer (derived from host cell) containing viral proteins that some viruses capsid are enveloped

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which viruses mutate quicker - RNA or DNA?

RNA

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what are the phases of viral growth cycle?

attachment (specific cells/system effected)
entry (can use a view methods)
uncoating (delivered to cytoplasm - integration/latency/lysogeny)
synthesis of viral components (through transcription to virus mRNA and translation to viral protieins or through genome replication)
assembly & release (lysis or budding)

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when is there latency period in virus?

varies for each virus but usually latency period between hours 1-5 when you can’t detect anything happening

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what is usually first clinical sign of a virus?

virus particle in blood stream

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what is a unique enzyme in RNA that can be targeted during replication phase?

reverse transcriptase
=needed as RNA undergoes reverse transcriptase to DNA to make more RNA

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why do some people argue that viruses may not be alive?

they take metabolism & energy from hosts and they don’t have genes for protein synthesis themselves (no ribosomes)

what is virus structure?

nucleic acid genome

=protein caspid
=sometimes a lipid envelope associated with virus proteins

relative simplicity means repeated structures

what are some key components of SARS-Cov2 structure?

spike = necessary for entry into host
membrane
envelope
nucleocaspid
RNA
4 structural proteins
16 non structural proteins
glycoproteins

what is
a) chemistry
b)structure
c) size
of virus genome?

a) DNA or RNA
b) double stranded, single stranded, linear or circular
c) 3500-330 000 base pairs

how do enveloped viruses acquire their envelopes?

by budding

what is budding process?

basically, virus enters cell and capsid is shed, replication occurs and then capsid reforms around multiple of the replicated bacteria. the viruses are then released from cell by leaving through membrane and when they leave, membrane of host cell envelops virus creating envelope in budding process

what is transmission for respiratory tract viruses?

inhalation & touch
sexual (upper respiratory)

what is transmission for gastro-intestinal tract viruses?

ingestion & inhalation

what is transmission of urogenitary tract?

sexual transmission

what is transmission of blood viruses?

vertical (child birth) needles products insect vector

what does localised virus mean and examples?

localised means virus remains at site of infection e.g. rhinovirus or molluscum

what is example of neural spread?

herpes simplex virus (HSV) -can spread from epithelial cells to neurons and can exist in body as latent

what is example of hematogenous spread?

in blood (HIV)

what are viral factors that cause damage to host cells - how do they damage host cell?

-by direct cytotoxicity (replication within host cell) - cell lysis (viruses induce bursting of host cell to release viral particles) - cell-cell fusion (proteins produced by virus on surface and promote fusion of membrane and spread between host cells - so viruses interrupt normal cell function) - inhibition of host cell transcription, translation alters function - alteration of host cell cycle, proliferation (cancer)

what are host factors that cause damage to viral cells?

- apoptosis (cell suicide- could be instructed by host cells) - lysis of infected cells by immune cells - inflammation

is self limiting a bigger or smaller risk?

smaller risk

why can HIV and influenza virus only be found in certain body areas and for what reason?

* Influenza virus - post translational modification of one of influenza virus proteins is dependent on a protein that is only expressed in cells of respiratory tract. * HIV can only enter cells that have CD4 and the chemokine receptor on the cell surface - cells of the immune system.

can viruses replicate in any cell of body?

no, they can only replicate in cells that have the right properties for that virus

what are 2 examples of immune response to infection?

-neutralising antibodies (that bind to virus to block them from entering into host cell for replication) - cytotoxic T cell response (promotes destruction of infected cell)

what are problems posed by viral infections?

- latency = not always aware of when someone carrying disease (herpes, varicella-zoster) - chronic/persistent infections (HIV & hepititus) - transformation of host cells - evolution (idea they replicate so quick that they can change surface molecules to drift away from drug receptor and drug receptors can only change so much before they won't fit) e.g. zoonotic, recombination - treatment options (vaccines, passive immunisation, anti-viral drugs)

what techniques are done to detect the virus?

PCR - qPCR = good for viruses that are hard to culture. loop mediated isothermal amplification (LAMP) Antigen = blood/swab/saliva. host cells. fluorescent antibody staining

what is loop mediated isothermal amplification (LAMP)?

a one-step amplification reaction that amplifies a target DNA sequence with high sensitivity and specificity under isothermal conditions (about 65°C). - was developed to address some limitations of PCR

what is serology and how can it help detect virus?

involves the checking for presence or levels of antibodies (like IgG & IgM) whcih can give idea of protection and how long it lasts

what are different types of anti-viral drug targets (different targets)?

-viral nucleic acid polymerase -viral enzymes involved in viral nucleic acid replication or in protein synthesis (integrase & protease) -uncoating -attachement/entry -release

what are different types of vaccines?

- live attenuated - inactivated - sub-unit - toxin - nucleic acid based