Virology and COVID-19

BIO315, Week 8A & 8B

How are viroids and prions different from viruses?

viroids → infectious, naked SS-RNA, no capsid; do not act as mRNA; may alter some regulatory function

prions → infectious proteins, no nucleic acid; misfolded protein (that causes normally folded proteins to become misfolded); protease resistant protein aggregates and amyloid deposits; spreads rapidly from cell to cell

Please compare and contrast enveloped and non-enveloped viruses.

enveloped → have membrane derived from host cell, takes membrane of human cell and encodes glycoproteins (specific receptors with host cells), sialic acid, inside has protein capsid

nonenveloped → capsid with nucleic acid (more resistant to nucleic acid), very hard to deactivate virus, will persist and be virulent for multiple days

Why can some viruses cause cancer?

special genes that work in cell cycle → are in S-phase

viruses (to make cell) → induces S-phase (synthesis, creation of new cells); induces oncogenes and induces S-phase

Please compare and contrast the lytic and lysogenic cycles.

lytic → phage replicates quickly → kills host cells (good/bad conditions) → no bacterial integration and host cells burst (RNA can only do lytic)

(good conditions → more cells replicated, bad → know to burst and persist)

lysogenic → phage is quiescent, may integrate into host cell genome, any replicate when host cell divides (moderate condition) (only DNA viruses, RNA cannot enter prophage)

(moderate conditions → hide until bad conditions and will escape)

Please compare and contrast generalized and specialized transduction.

generalized → bacterial chromosome is chopped up and put into bacterial capside phage → hijacks cell cycle and wants cell to take bacterial particles, do not want to waste time and make energy for replication, recombines chromosome and tries to enter new cell

specialized → phage enters specific location → takes bacterial chromosome and will take some viral and bacterial DNA out (transducing) → will intergate into new cell → transducing cannot enter lytic phase, must use galactose gene

What happens during the latent eclipse, latent non-eclipse, and rise periods of a viral one-step growth curve? Why does the number of viral particles level off after the rise period?

latent eclipse → no external viruses are made, no external phages, optimal phage breaks open host cell through chloroform, no viable phage

latent non-eclipse → viral particles inside

rise periods → lots of viral particles are released through lysis

Level off → all cells producing viral products generally need more host cells

What are some functions of viral genes classified as early, middle, or late during the viral life cycle.

early → replication of viral genome, needs to hijack cell cycle, encodes same proteins for cell replication, prepares for synthesis

middle → replication of proteins and informing, more viral genome and capsid, synthesis

late → after replication, encode proteins for viruses and releasing with capsids

What two mechanisms can animal viruses use to enter host cells? Which one can lead to quicker detection by the host immune system (and please explain why)?

receptor mediated endocytosis → internalized, enters into cytoplasm into ribosome

fusion of viral envelope → left in membrane of host cell and capsid is released → leads to quicker detection; membrane fusion (COVID-19)

Please compare and contrast the replication of ssRNA and ssDNA viruses in eukaryotic cells.

ssRNA → needs special enzyme to go from RNA to DNA, single stranded, 2 versions (+-), has ssRNA to replicate and and reproduce in

ssDNA → has thymine, needs host cell dependent polymerase, more stable than ssRNA (less mutations), replicates in nucleus

Please compare and contrast antigenic drift and antigenic shift.

both → involve changes in viruses and genetic makeup

antigenic drift → shift in virus genetic makeup, reacting in a mixing of genes, creating a mix of different viral strains; more drastic change; recombine nucleic acid

antigenic shift → gradual change in genetic makeup (minor changes) due to small mutations in genetic makeup, recurring in new viruses with similar but different makeup (ex. influenza and COVID-19)

Please describe the COVID-19 reproductive cycle and use part of it to explain why women, on average, are less at risk for severe symptoms from COVID-19 than men.

cycle → ssRNA → fuses with membrane of cell → infected cell translates and enters into S-phase → after synthesis, ssRNA can be directly translated → begins replication of viral proteins

women are less at risk → have 2 X chromosomes, 2 distinct receptors, virus has harder time since they have 2 receptors to infect

men only have 1 X chromosome → easier to get virus and will spread more quickly

What 4 factors put you most at risk for catching COVID-19 from an infected person? On average, how many people does each person infected with omicron COVID-19, alpha COVID-19, and the seasonal flu infect?

4 factors: both without mask (infected vs unaffected), enclosed space, duration of interaction, and distance

near them for a long time and without masks → high likelihood of infection or spread of infection

(15 people can get infected by one person) (if immuno-compromised, more vulnerable to infection)

How can face masks reduce the spread of COVID-19? What characteristics make masks more effective?

reduces spread of COVID-19 → blocks respiratory droplets and air particles from infected

masks more effective → higher the layer count, resistant to humidity, filtered mask

How do COVID-19 PCR tests work?

PCR → sample from infected → perform reverse transcription, will see with fluorescence, amplification of molecule sides, keep repeating until sample reacts

reverse transcriptase → uses viral RNA to isolate retrovirus and amplify DNA after 40 cycles (1 RNA makes 1 DNA → replicates DNA (known as doubling time))

What advantages does mRNA vaccines have over traditional protein vaccines?

mRNA vaccines → have faster development, no need for growing viral proteins, amplify, adaptable

our cells develop spike proteins for viral DNA → phagocytoses by macrophages

RNA → spike protein → MHC-1 → activates cytotoxic killer T cells

Why do you think a significant percentage of people who received a placebo in the Pfizer vaccine study developed fatigue and chill?

Placebo → not having an treatment done to them but do not know they have been given something without effects

Placebo effect → Pfizer vaccine → developed fatigue and chills → psychosomatic (brain believes its been given something to treat it and reacts like it would as if it was fighting the virus, have symptoms similar to flu)