Lecture 14 Flashcards
What toxin is responsible for toxic shock syndrome? How does it damage the hosts tissues?
Toxic shock syndrome toxin
TSST is a superantigen which stimulates T cells by forcing interactions between MHC and TCR causing uncontrolled cytokine (IL-2) release, leading to septic shock. 20% of T cells are activated. Causes decreased tissue perfusion and oxygen delivery.
What is a surface acting toxin? What is an example and what bacteria produces this toxin?
A toxin that bins to a receptor to induce a signal in the cell
Toxic shock syndrome toxin produced by Staph aureus
Whats the difference between a large pore-forming toxin and a small pore-forming toxin? What is an example of both?
Large pore-forming toxin- 20-30nm pores, targets phagosomes or plasma membrane. e.g LLO (Listeria)
Small- 1nm pores, targets the plasma membrane e.g. alpha toxin (Staph aureus)
Describe how AB toxins work. What is an example?
B toxin: Binds to a receptor on the surface of the host cell and helps the A domain translocate into the host cytoplasm.
A toxin: Has the toxin activity. This domain is translocated into the host cytoplasm, either from an endosome or from the ER
e.g. Diptheria, Cholera, or Anthrax toxins
What bacteria produces diptheria toxin?
Corynebacterium diptheriae
How does the diptheria toxin damage host tissues and cause symptoms of disease?
Diptheria toxin damages mucosal cells by ADP-ribosylating the host Elongation factor 2 to inhibit EF2 binding to tRNA, thereby preventing protein synthesis. Damaged mucosal cells in the throat, results in a pseudomembrane compromised of bacteria, inflam cells, and fibrin. Can cause suffocating or damage to internal organs following the release of the toxin into the blood stream.
How does the cholera toxin work to cause large amounts of watery stool?
Cholera toxin kills cells by ADP-ribosylating a host GTP-ase. This constitutively activtes adenyl cyclase which results in cAMP accumulation in the host cell. cAMP activates cystic fibrosis transmembrane conductance regulator (CFTR) which pumps Cl- out of the cell. This results in secretion of ions and a large amount of water into the lumen of the intestine.
How does the cholera toxin get into the host cell?
Cholera toxin binds to the surface of the cell and is endocytosed into the cell. It then gets trafficed into the ER where its removed from the endosome into the cytoplasm.
Explain why Vibrio cholerae is required to have the adhesin TCP to also have the cholera toxin gene
V.cholerae uses an adhesin called TCP to adhere to the surface of the host cells. TCP is a type IV pilus and is needed for virulence.
Cholera toxin gene is encoded by a bacteriophage. The bacteriophages receptor is TCP therefore only bacteria with a TCP are infected by the bacteriophage and acquire the toxin.
Energetically not favourable to have the toxin gene if the bacteria doesn’t have the TCP.
