Diphtheria (C. diptheriae) and Anthrax (B. anthracis)

List these characteristics of Diphtheria
1. intracellular/extracellular
2. high/low G+C
3. shape
4. yes/no capsule
5. Gram + or -

1. extracellular
2. high G+C
3. club shaped
4. capsule
5. gram +

What kind of human disease does diphtheria cause?

Upper respiratory tract and mucosal membrane infection leading to formation of a pseudomembrane in the throat and inflammation of the neck

What are the virulence factors of diphtheria

Diphtheria toxin

How does diphtheria toxin enter the cell: explain the biochemistry

through ADP ribosylation of EF2

How does diphtheria toxin enter the cell? explain the biological process

The B subunit binds to the receptor and the A subunit is endocytosed into an endosome. Acidification of the endosome causes release of the A subunit which leads to ADP-ribosylation of EF2, blocking protein synthesis, and leading to cell death

What confers resistance to diphtheria toxin and how?

Bafilomycin, prevents endosomal acidification

What four mutations could you make to confer resistance to Diphtheria toxin?

1. mutate the receptor
2. mutate the proton pump
3. alter genes
4. use furin protease to cleave DT

How is does C. diphtheriae get diphtheria toxin?

Through a lysogenic bacteriophage where DT is induced in response to low iron

What is used for the vaccine to diphtheria?

Diphtheria toxoid (enzymatically inactive and cannot bind iron)

What does TDAP protect against?

Tetanus, Diphtheria, Pertussis (Whooping cough)

what is the difference between endotoxins and toxins?

endotoxins are produced by gram negative bacteria and are heat stable while toxins are heat labile and produced by bacteria

What are the three types of toxins?

1. A-B toxins
2. Hemolysins
3. Superantigens

List the characteristics of a toxin?

- synthesized during infection
- secreted
- act at a distance
- recapitulate activity in vitro
- enzymes, pore-formers, or superantigens
- antigenic, but can become nontoxic
- immunogenic (toxoids) used for vaccines

A-B toxins

toxins that are comprised of an A (catalytic subunit brought into host cell via pore formation) and B (binding subunit that binds to host cell receptor to stimulate endocytosis)

hemolysins

toxins that lyse red blood cells to release hemoglobin

cholesterol dependent cytolysins

a family of hemolysins that bind cholesterol, oligomerize, and form large pores for the insertion of proteins into host cells

superantigens

cause an intense immune response due to the release of cytokines from host cells --> sepsis and immunosuppression

Are effectors toxins?

no - and they do not act at a distance

chimeric toxins

Toxins in which the B-subunit is changed out for another B-subunit that will target specific cells and promote antibody formation
- used as a therapeutic agent but was too toxic, and not selectively toxic enough

List these characteristics of B anthracis:
1. spore forming? y/n
2. capsule? y/n
3. high/low G+C
4. shape
5. motile? y/n
6. weaponized? y/n
7. human to human transmission? y/n

1. yes spore forming
2. yes capsule
3. low G+C
4. rod shaped
5. non-motile
6. weaponized
7. no human to human transmission

What are the virulence factors of B. anthracis?

1. the 3-protein toxin (A-B type)
2. the capsule (blocks phagocytosis)

What is special about the spores of B. anthracis?

they can survive in soil, but only grow/germinate/release toxins when inside the host, and they sporulate upon release from the host (O2-dependent)

What are the characteristics of human disease caused by B. anthracis?

- coal black pimples --> fever and headache
- fever, fatigue --> respiratory distress --> shock and death within 24 hr

What are the three ways humans can get B. anthracis?

1. cutaneous
2. inhalation
-- livestock workers disease (Shearing sheep)---
3. oropharyngeal/gastrointestinal: from contaminated meat

What the components of anthrax toxin?

1. B subunit: protective antigen (PA)
2. 1st A subunit: Edema factor (EF)
3. 2nd A subunit: Lethal factor (LF)

how does the lethal factor work?

Acts as a protease and cleaves MAP kinase --> shock and death

What are targets of vaccine/protection against toxin?

- the PA
- NLRP1 inflammasome protects against toxin???