chapter 6 viruses and prions (exam 2)

Define virus

nonliving/noncellular entities that can infect plant, animal, and bacterial cells & can have RNA or DNA genomes and are filterable infectious agents (very small)

can viruses synthesize their own nucleic acids and proteins apart from a host?

NO

viruses can obligate intracellular pathogens? Meaning?

disease-causing microbes that must invade living cells and hijack their biochemical and cellular tools to replicate

Define a virus that infects a bacterium? what is a virion?

bacteriophages, a virion is a single infectious virus particle protected by a protein

what is a capsid, and what macromolecule makes up the capsid?

a protein shell that packages and protects a virion’s genome and also accounts for the bulk of a virons mass

capsomere?

three dimensional protein subunits that make up capsids

three general virus capsid shapes?

helical, icosahedral, complex

what macromolecule comprises the viral envelop?

lipids

what is a naked virus?

NO ENVELOPE

where does and enveloped virus obtain its envelop?

budding from the host and taking a portion of the cell membrane as a coating when the virus leaves

Another term for spikes?

peplomeres

What macromolecule makes up viral spikes?

proteins

what part of the virus binds to specific factors on a host cell which determines the exact cell type a virus can infect?

viral spikes

the influenza virus that causes swine flu is called H1N1. Name the glycoproteins that produce “HA” and “NA” spikes which are represented by the letters H and N respectively, in H1N1

HA is hemagglutinin & NA= neuramindase

in general can a single virus’s genome contain both DNA and RNA?

No

Which type of single-stranded RNA virus genome functions directly as mRNA?

single stranded sense RNA viruses (ssRNA+)

what enzyme is used by single-stranged antisense RNA (ssRNA-) viruses to make mRNA form an RNA template?

RNA-dependent RNA polymerases

what is the function of the enzyme reverse transcriptase?

builds a double-stranded DNA using single-stranded viral RNA genomes as a template

why do RNA viruses mutate more quickly than DNA viruses?

RNA polymerase do not have the proofreading capabilities of DNA polymerase

do attenuated virus strains cause disease in healthy non-immunocompromised hosts?

no

define tropism

the preference of a pathogen for a specific host and even a specific tissue

the influenza virus undergoes processes called antigenic drift and antigen shift. Define the two processes and describe the outcome of each using the example of influenza.

Drift= minor genetic changes in virus (leads to influenza epidemics) Shift= a major genetic reassortment that dramatically changes the virus -( leads to viral strains with new features/ leads to influenza pandemics)

The pfizer and Moderna SAR-CoV-2 vaccines use which immunization strategy?

mRNA vaccinations and vector vaccines

what viral protein is coded for by pfizer and Moderna SARS-CoV-2 vaccines, which is then produced by the host?

viral protein spike protein

The johnson & johnson SARS-CoV0-2 vaccine use which immunization strategy?

the vector vaccine approach

True or False? viruses are not classified into domain. Their highest taxnomic classification is kingdom

false, viruses are not assigned to domains or kingdom, instead they are put into the phylum ranking (order level then family and sometimes subfamily)

in bacteriophage what type of replication kills the host cell when new phage are released?

lytic replication

define prophage?

it is the result of the phage genome being incorporated into the host cell genome, it then copies its own genome as well as the prophage genome

what is the medical importance of phage conversion?

important because they have the ability to confer new pathogenic properties to bacterial cells

step 1 of animal virus replication in the order they occur and briefly describe what occurs during:

attachment: naked viruses attach to host cell membranes through capsid protein

step 2 of animal virus replication in the order they occur and briefly describe what occurs during:

penetration: enveloped animal viruses enter the host cell through membrane fusion or endocytosis, naked virus enter through endocytosis

step 3 of animal virus replication in the order they occur and briefly describe what occurs during:

uncoating: animal virus capsids enter the host cells and the the capsid is broken down, releasing the viral genome

step 4 of animal virus replication in the order they occur and briefly describe what occurs during:

replication: DNA viruses import their genome into host cell nucleus to be transcribed and replicated, resulting mRNA is shipped from nucleus to cytoplasm to create viral

step 5 of animal virus replication in the order they occur and briefly describe what occurs during:

assembly: new capsids are partially built and packed with viral genome before finished and sealed

step 6 of animal virus replication in the order they occur and briefly describe what occurs during:

release: viral proteins are embedded in the host cell membrane before virion release, naked virusrupture the host cell during release.

define acute infection:

infections that run their course and are cleared by the host immune system (ex. the cold and influenze)

define persistent infection?

Infections that run their course and are caused by persistent viruses that remain in host for long periods (many weeks to a lifetime)

defien provirus:

chronic or latent infections caused by a persistent infection integrates their genome into the host cell.

what is one of the most important advances in HIV treatment for healthcare providers who may have been exposed to HIV?

post exposure prophylaxis (PEP) or preventing the infection from starting (administered to people after an accidental needle stick)

define latent infection?

infection in which the host does not have signs or symptoms and can have flare-ups

which virus causes the latent infection called cold sores?

human herpes virus HHV-1/HSV-1

which virus causes chickenpox? which virus causes the latent infection called shingles?

chickenpox= herpes viridae/HHV-3, Shingles = HHV-3

define: oncogenic virus

virus that cause cancer

according to the u.s. centers for disease control and prevention (CDC) what percentage of all cervical cancer cases are linked to HPV?

90%

which two retroviruses form proviruses form proviruses and can quietly persists in host cells for more thatn a decade before emerging to cause leukemia or lymphoma?

the human T-Lymphotropic viruses HTLV-1 & HTLV-2

define a plaque/ what does one plaque represent

a clear zone on a growing plate of bacteria that represents a single bacteriophage in the initial sample

what is a concern when vaccines are made from virions purified from fertilized chicken eggs?

people allergic to eggs cannot get the vaccine

define sensitivity and specificity in reference to diagnostic testing methods:

sensitivity: the ability of a diagnostic test to detect low levels of the target to limit false negative results (spikes), specificity= whe the diagnostic test reliably detects only the agent of interest without producing false positive results

aggulatination assay

2 strategies used - 1. adheres antibodies (proteins made against certain parts of antigen) that are specific to the viral antigen you want to detect in a patient sample onto very small latex beads if the patient sample has the antigen that is specific to the antibody, they will bind to each other (lock and key). The bound will clump with other antigen.antibody & will agglutinate and come out of solution. 2. a variation- coats a known virus onto latex bead and if patient sampel has antibodies made for the specific antigen, binding and agglutination will happen

agglutination assays can be used to detect other pathogens and molecules not just viruses.

true

What type of immunoassay adheres viral antigen to latex beads to determine if a patient sample contains antibodies made to the virus? (Remember, the test could also use antibody-coated latex beads to test if the patient’s sample has the antigen that is specific to the antibody).

agglutination test

What type of immune assay adheres an antigen or antibody to a surface and usually changes color if binding occurs?: 

Enzyme linked immunosorbent assays (ELISAs)

Immunoassays such as agglutination and PCR have limitations. One limitation is seroconversion. What is a seroconversion window?:

the couple of weeks it take for an infections antibodies to develop

What do PCR tests amplify? What does the acronym PCR stand for?: 

Polymerase Chain Reaction - amplifies specific parts of a genetic sequence

Why can’t a viral infection be treated with antibiotics?

they are not cells and antibodies only target cell structures

When developing drugs, what is selective toxicity and why is it important?

when a drug stops the pathogen but leave the host cell unharmed, it wont poison the cell

What two categories of testing options are currently used to detect active SARS-CoV-2 infections?:

antigen tests and reverse transcription - PCR tests (RT-PCR)

What does the RT-PCR test detect? What does the antigen test detect?

RT-PCR= detects the genetic material of SARS-CoV-2, antigen test = detects SARS-CoV-2 proteins

Which test is the “gold standard” test when detecting SARS-CoV-2 infection?: 

RT-PCR test

postexposure prohylaxis:

prevention treatement applied after an exposrure to limit infection

prions?

infectious proteins that can cause disease, transmitted by transplants or ingestion - some prion diseases are inherited

current theory explaining how normal prion proteins become misfolded?

infectious version of prion proteins makes contact with the normal, version, causing changes in the shape

why are diseases caused by prions called spongiform encelphalopathies?

they cause brain degeneration leaving spongy holes in the tissue.

two spngiform diseases that occur when a child inherits a parental gene that encodes a mutated form of the prion protein

Gerstmann-Straussler-Scheinker syndrome and Fatal Familial Insomnia

which type of acquired Cretzfeldt-Jakob disease (CJD) has been given the name mad cow disease?

variant CJD

what is sporadic CJD linked to?

spontaneous mutation in the normal cellular prion protein that affects 200-400 people in the U.S.

How does a person acquire iastrogenic CJD?

accidentally through medical intervention

Several neurodegenerative diseases have been associated with misfolded proteins in the brain but are not considered spongiform encephalopathies. List three of them.: 

 Alzheimer’s disease, Parkinson’s disease, and Amyotrophic disease