Lecture 30 - Antivirals Flashcards by Paityn Murray

obligate intracellular parasites that rely on host biosynthetic machinery to reproduce

viruses

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when not inside an infected cell, viruses exist as independent particles known as:

virions

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what are the major components of a virion?

double or single stranded DNA or RNA
a protein coat (capsid)
some also possess a lipid envelope (derived from the host cell)

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how big is a virion?

~1/100th the size of the average bacterium

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the group of cell types (or species) that a virus can infect

viral range

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a virus that only infects bacteria

bacteriophage

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viruses that infect animals or plants

animal viruses or plant viruses

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true or false: most animal viruses do not cross phyla, and some only affect closely related species

true

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viruses can be classified based on:

the shape of their capsid (helical, icosahedral, complex)

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the ability of viruses to cause disease

pathogenicity

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the degree of pathogenicity

virulence

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some viruses can remain dormant in organisms, this is called:

latency

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what is an example of a latent virues?

the virus that causes chicken pox in children can come back as shingles in adults

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what are the four phases of the viral “life cycle”?

absorption, penetration, replication, release

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the surface of viruses have proteins that bind to receptor proteins on host cells

absorption

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viral DNA or RNA crosses the plasma membrane to the cytoplasm or nucleus

penetration

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once inside, viral DNA or RNA interacts with host machinery for translating DNA or RNA into viral protein

replication

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newly synthesized virion particles are released to continue the infection cycle

release

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what is the central dogma of biology?

DNA –trascription–> RNA (mRNA) –translocation–> protein

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where does DNA transcription and replication occur?

the nucleus

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where does protein translation occur?

the cytoplasm

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most DNA viruses enter the host cell neucleus ehere the viral DNA is often integrated into the host genome and transcribed into mRNA by:

host DNA-dependent RNA polymerase

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carry their own DNA-dependent RNA polymerase and replicate in the host cell cytoplasm

poxviruses

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viral genome replication requires _____ from the host or virus

DNA-dependent DNA polymerase

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double stranded RNA viruses require _____, so the must make itself

RNA-dependent RNA polymerases

the viral RNA-dependent RNA polymerase acts both as a _____ and a _____

transcriptase (to transcribe mRNA), replicase (to replicate the viral genome)

most RNA viruses complete their replication in the:

host cell cytoplasm

have an RNA genome that directs the formation of a DNA molecule (RNA --> DNA --> mRNA --> protein)

retroviruses

viral enzyme that copies viral RNA into DNA (an RNA-dependent DNA polymerase)

reverse transcriptase

true or false: most retroviruses do not immediately kill their host cells, rather infected host cells can continue to replicate producing daughter cells with integrated proviral DNA

true

a cheap and effective way of preventing infections by viruses

vaccinations

vaccines can consist of:

live-attenuated or killed viruses, viral proteins, or mRNA

anti-viral drugs can exert actions at several stages of viral replication including:

viral entry, nucleuic acid synthesis, protein synthesis, viral packaging, and virion release

combination therapy can result in greater clinical effectiveness against viral infections and can also prevent or delay the emergence of:

resistance

anti-viral drugs are virustatic, which means that they are only active against:

replicating viruses and do not affect latent viruses

a nucleoside analog (fake DNA binding block) which viruses incorporate into their genomes during replication

acyclovir

acyclovir lacks a hydroxyl group important for forming the:

backbone of the DNA molecule (DNA chain termination)

acyclovir is used as an:

anti-herpes drugs

acyclovir must be phosphorylated to _____ to be incorporated into viral DNA as a terminal substrate

acyclovir-triphosphate

has an affinity for acyclovirthat is about 200x that of the mammalian enzyme

thymidine kinase

acyclovir resistance in the herpes simplex virus can result from:

- impaired production of viral thymidine kinase - altered thymidine kinase substrate specificity - altered viral DNA polymerase

a family of retroviruses that lead to chronic persistent infection with gradual onset of clinical symptoms

lentivirus

human immunodeficiency virus (HIV) is a:

lentivirus

what type of cells does HIV infect?

human immune cells (CD4+ T cells)

when CD4+ T cells decline below a critical level, cell mediated immunity is lost and the body becomes susceptible to:

opportunistic infections (AIDS)

in the abscence of HIV treatment, there is generally no true period of:

viral latency following infection (replication is constant)

anti-viral HIV drugs target viral infection at multiple levels including:

fusion, transcription, integration to host genome, and virion release

current HIV treatment usually involves:

3 or more antiretroviral drugs

can slow or reverse the increases in viral RNA load that normally accompany progression of disease

highly active antiretroviral therapy (HAART)

HIV infection begins with attachment of HIV envelope proteins called _____ to _____ receptors on the surfaces of the T cells

gp120, CD4 and CCR5

what do HIV entry inhibitors do?

interfere with binding, fusion, and entry of an HIV virion into a human cell

a CCR5 receptor antagonist (interferes with HIV binding to T cells)

maraviroc

____ enzyme synthesizes DNA from HIV RNA using nucleosides in the host T cell

HIV reverse transcriptase

small molecule drugs that are similar to the host cell nucleosides, and are incorporated into new HIV DNA chains as if they were endogenous nucleosides

nucleoside reverse transcriptase inhibitors (NRTI)

how do nucleoside reverse transcriptase inhibitors (NRTIs) stimulate chain termination?

NRTIs lack a 3'OH on the ribose ring, making attachment of the next nucleoside impossible

true or false: mammalian RNA and DNA polymerases are sufficiently distinct to permit a selective inhibition of viral reverse transcriptase

true

a viral enzyme that inserts viral genome into the DNA of the host cell

integrase

what do integrase strand transfer inhibitors (INSTs) do?

they block the action of integrase to inhibit HIV proliferation

what is an example of an nucleoside reverse transcriptase inhibitor (NRTI)?

raltegravir

this viral enzyme cleaves precursor proteins to form the final structure proteins of the HIV virion core

aspartate proteases

designer drugs based on molecular characterization of the active site of the viral enzyme

HIV protease inhibitors

HIV protease inhibitors are usually used in combination with:

reverse transcriptase inhibitors

a common anti-influenza drug that inhibits an early step in replication (viral uncoating) of the influenza A virus

amantadine

functions as a proton ion channel required at the onset of infection to permit acidification of the virus core, which in turn activats viral RNA transcriptase

M2 protein

blocks proton transfer through M2, thus blocking acidification and the initiation of viral transcription

amantadine

a prophylactive against influenza A (not B) virus infection and can reduce the duration of symptoms if given within 48 hours after contact

amantadine

what is the more effective method at treating influenza: prophylactics or vaccines

vaccines

an inhibitor of neuroaminidases produces by influenza A and B

zanamivir

what does zanamivir do?

cleaves sialic acid residues from viral proteins that enables viruses to be released from the host cell