Pathogenicity and Virulence

describe the chemical and physical structure of an enveloped virus

host derived membrane, gets it from the cell when they leave---> survival adv. because now it looks like the host

nucleic acid

capsid

genetic material

glycoprotein

describe the chemical and physical structure of a naked virus

capsid--> acts like a nucleus, made up of capsomeres., nucleic acid, genetic material

what is the nucleocapsid in a virus

the nucleic acid and the capsid

is an enveloped or a naked virus easier to control

enveloped because it is made up of lipids instead of a hard crusty membrane

describe how bacteriophages are cultured

bacterial viruses are easiest to grow, hosts in liquid medium or spread as "lawns" on agar and inoculated with virus

describe how animal viruses are cultured

animal and plant viruses are cultivated in tissue cultures from animal organ in culture medium or hairy root-based system in liquid medium

what does PFU stand for

plaque forming units

describe the 4 possible outcomes of animal virus infections

1. transformation: viruses infect and change shape/ replication of the cell/ tumor cell divison---> Onco viruses and HPV

2. lysis: cell lysis; death of the cell and release of the virus; Parvo virus ---> causes fifth disease

3. persistence: will continuously reproduce and infect other cells and people but at some point you are done being infected, slow release of virus without causing cell death

4. latent: virus continues to be present, once infected always infected, virus present but not replicating (HIV, chickenpox, herpes)

Name and describe the 4 stages of viral replication

1. attachment: absorption of phage virion

2. penetration of viral nucleic acid

3. synthesis of viral nucleic acid and protein and assembly and packaging of new viruses

4. cell lysis and release of new virions

lysogenic lifecycle with virus example

lysogenic lifecycle only applies to phages, they go into the lysogenic life cycle when number of host cells available is low, attach and inject, viral DNA is integrated into host DNA, viral DNA is replicated with host DNA at cell division, can switch to lytic cycle

temperate phage, herpes

lytic lifecycle with virus example

attach and inject, phage components are synthesized and virions are assembled, lysis of the host cell and release of new phage virions (makes more and then finds a new host)

virulent phage, T4

antigenic drift vs shift

Antigenic Drift: Small mutations change surface proteins; seasonal slight changes

Antigenic Shift: reassortment, abrupt change (pandemics), no immune response

what viral classification are viruses of archaea

All have DNA genomes

almost all are double-stranded circular DNA viruses

what is an example of double-stranded DNA bacteriophages, what is its virulence, what is it associated with

T4

always kills the host

associated with E.coli

on average, archaea virus genomes are _______ than bacteriophage genomes

smaller

what are the replication strategies of archaeal viruses like

more like eukaryotic viruses than bacteriophages

there is no virus-specific RNA polymerase

example of double stranded DNA animal viruses that have unusual replication strategies

pox viruses: replication occurs in cytoplasm instead of nucleus; very difficult to make a vaccine, can't make an RNA vaccine because the genetic material is large and too complicated

example of DNA tumor viruses

herpes virus

dsDNA virus that cause diseases

able to remain latent for extended periods of time

reactivate under stress or weakened immune system

examples of positive strand RNA virus

poliovirus

spread through contaminated water and food

coronaviruses

examples of corona viruses

SARS: severe acute respiratory syndrome

MERS: middle eastern respiratory syndrome (transmitted from camels)

SARS-COV2: covid

examples of negative strand RNA animal virus

rabies virus: rhabdovirus, bullet shaped, enveloped, nucleocapsid containing several enzymes

influenza virus: hemagglutin surface proteins elicit an immune response, neuraminidase is the exit portion of the life cycle, has RNA replicase

what an example of a virus that undergoes antigenic drift

influenza

what viruses use reverse transcriptase

retroviruses and hepadnaviruses

what is reverse transcription

synthesize DNA from RNA template

what are prions

infectious proteins whose extracellular form contains only protein, denatured proteins that degrade and accumulate in the cells (very slow process), no nucleic acid

ingest or through kuru (eating human brains)

what is Creutzfeldt-Jakob disease

brain degrades over time

what are the enzymes specific to virions

lysozyme: makes hole in cell wall to allow nucleic acid entry, also lyses bacterial cell to release new virions

neuraminidases (influenza): destroy glycoproteins and glycolipids, allows liberation of viruses from cell

nucleic acid polymerases: RNA replicase --> RNA-dependent RNA polymerases; reverse transcriptase --> RNA dependent DNA polymerase in retroviruses

Categories of exotoxins

AB toxins

Cytolytic toxins

Super antigen toxins

Cytolytic Exotoxins

Work by degrading cytoplasmic membrane, causing cell lysis and death. Toxins that lyse red blood cells

AB exotoxin

Some best known and most potent exotoxins are AB toxins. Made up of an Active (A) domain and and a binding (B) domain

What clostridium produce potent AB toxins?

Clostridium tetani and clostridium botulinum

Super antigen exotoxins

Cause an overstimulation of the immune system which can lead to shock or death. Generally due to a localized infection, but with synthetic effects.

What are major producers of exotoxin superantigens?

Staphylococcus aureus and streptococcus pyrogenes

Endotoxins

Toxic lipopolysaccharides found in the cell walls of most gram-negative bacteria. Secreted products of living organisms. They are cell-bound and released in toxic amounts when cells lyse.

Properties of exotoxins

-Chemistry:

-mode of action; symptoms:

-destroyed with heat?:

-fever potential?:

-genetic origin?:

Properties of Endotoxins

-Chemistry:

-mode of action; symptoms:

-destroyed with heat?:

-fever potential?:

-genetic origin?:

stages of disease

infection: the organism invades and colonizes the host

incubation period: the time between infection and onset of symptoms

acute period: the disease is at its height

decline period: disease symptoms are subsiding

convalescent period: patient regains strength and returns to normal

compare the effects of coagulase, streptokinases, and hyaluronidase

enzymes as virulence factors

coagulase: coagulates plasma proteins, adv for survival or organism to prevent immune cells from finding it (staph aureus)

streptokinase: associated with streptococcus, opposite of coagulase, secretes it in order to spread

hyaluronidase: break down cell cement, breaks down cell membrane and the cells move on to deeper areas (streptococcus pyogenes)

common vs host to host transmission

common: comes from a common source, in direct common source such as a vehicle

host to host: travels from direct contact between people

Modes of transmission

Can be direct or indirect