SARS CoV-2

step 3

+ ssRNA is immediately translated to produce SARS-CoV-2 replicase

step 6

+ ssRNA viral genome is translated into SARS-CoV-2 proteins by host ribosomes

How many coronaviruses are known to infect humans?

6; 4 cause the common cold, SARS and MERS cause fatal illness

syncytium

A large multinucleate cell, typically formed by the fusion of many smaller cells

What is antigenic drift?

Antigenic drift refers to the evolutionary accumulation of amino acid substitutions in viral proteins selected by host adaptive immune systems as the virus circulates in a population. Antigenic drift can substantially limit the duration of immunity conferred by infection and vaccination. Antigenic drift describes small mutations, especially in key binding proteins, that interfere with the immune system's ability to recognize and clear the microbe. The COVID-19 vaccines target the spike protein (viral glycoprotein required for attachment). Mutations in the spike protein decrease the immune system's ability to recognize and therefore respond to an infection with SARS-CoV-2.

Who first showed that DNA was the 'transforming factor' that turned rough S. pneumonia colonies to smooth colonies?

Avery, MacLeod and McCarty

Whole genome sequencing of the novel virus indicated that it matched 86.9% nucleotide sequence identity with which other coronavirus?

High similarity to a bat SARS-like CoV; likely a beta-coronavirus

list the ways we can disrupt the SARS-CoV-2 lifecycle

Inhibition of attachment binding, inhibition of endocytosis, inhibition of host/viral membrane fusion, protease inhibitors, use of nucleoside analogs

In the conclusions, the authors state that their study does not fulfill Koch's postulates. Which of Koch's postulates were fulfilled? Which were not fulfilled?

Not fulfilled: Imperfect creation of pure culture (Postulate 2); infected primary cell culture and observed changes but did not infect healthy individuals and mimic exact disease previously observed (Postulate 3)

Why was it expected that SARS-CoV-2 would mutate?

RNA viruses are prone to mutation

step 5

RdRp synthesizes a complementary - RNA strand to serve as the template to make more viral genome and mRNA

step 4

SARS-CoV-2 protease cleaves the SARS-CoV-2 replicase into individual viral proteins, including RNA-dependent RNA polymerase

How was the novel virus detected (using primers targeting what region)?

Sequencing of RNA from the bronchoalveolar fluid of infected patients determined that the novel virus had sequence similarity to a betacoronavirus. RT-PCR using a consensus RdRp region of pan beta-CoV confirmed that the novel virus belonged to the Coronaviridae family of viruses.

What is the name of the protein that complexes with RNA polymerase?

Sigma factors are unique to bacteria, and they complex with the RNA polymerase enzyme to form a holoenzyme and scan the DNA for a promoter sequence.

Fred Griffith

Specifically, the highly virulent S strain had a smooth capsule, or outer coat composed of polysaccharides, while the nonvirulent R strain had a rough appearance and lacked a capsule (Figure 1).

Would identification of the novel virus have been more difficult if it did not belong to a known family of viruses?

Yes, because we currently use similar sequences of known related viruses to help us understand the characteristics of the novel virus. Yes, it would make design of primers targeting virus more difficult.

Describe step 1 of the SARS-CoV-2 viral replication cycle

attaches via the SARS-CoV-2 spike protein to the host receptors ACE2 and TMPRSS2

step 2

binding to the ACE2 and TMPRSS2 host receptors initiates the host to form an endosome around the virus

Why are bacteria that lack capsule also less virulent?

capsule prevents phagocytosis by macrophages

acidification of the endosome initiates the viral envelope to

fuse with the endosomal membrane and release viral + ssRNA into the host cytoplasm

What are the newly synthesized DNA strands that are moving towards an opening replication fork called?

leading strands

what does RNA-dependent RNA polymerase do to disrupt the SARS-CoV-2 life cycle

nucleoside analog that incorporates into viral RNA will disrupt viral replication

What does the SARS-CoV-2 protease inhibitor do

prevents processing of SARS-CoV-2 replicase

What primers did the authors of this article use to determine that the novel virus was likely a corona virus?

primers that were specific for viral genomes and placed in a position of similar sequence

SARS-CoV-2 enters the host cell via

receptor-mediated endocytosis

list the SARS-CoV-2 proteins

spike, envelope, membrane, nucleocapsid

Transmission electron micrographs indicated the virions had what appearance that is consistent with the Coronaviridae family?

they had the crown-like spikes. Distinctive spikes that give the characteristic corona, or "crown", appearance. All coronaviruses are enveloped with viral glycoproteins embedded in the envelope, giving this characteristic appearance.

All non-enveloped animal viruses enter the cell via endocytosis.

true

step 7

viral assembly occurs and new virions are released from the host cell via exocytosis

Why were cytopathic effects measured and not viral plaques?

with animal viruses, if they are enveloped, we won't be able to look for lysis of animal cells. so you'll be observing cytopathic effects instead. how is the virus changing the morphology/function of the host cells.