Intracellular Pathogens- Lecture 17

Question 1

Benefits of living inside host cells

Answer 1

(1) Evade the immune system
(2) Access to nutrients
(3) no competition with host microbiota

Question 2

Risk of living inside host cells

Answer 2

(1) Degradative organelles, phagolysosome
(2) ROS, reactive oxygen species

Question 3

Mechanisms of entry into cells cells

Answer 3

(1) Receptor-mediated endocytosis (non phagocytic cells)
(2) Phagocytosis (white blood cells)

Question 4

Characteristics of Listeria Monocytogenes

Answer 4

gram-positive, firmicute, cause of food borne illness because of ability to survive cold, salty temperatures, facultative anaerobe

Question 5

Listeriosis life cycle

Answer 5

Entry into cells through receptor-mediated
(1) Internalins A and B: interact with adhesion protein, E-cadherin and IntB interacts with hepatocyte growth factor receptor, clathrin-mediated endocytosis through Actin re-arrangement
(2) punch and degrade the vacuole using listeriolysin O and PlcA and PlcB (phospholipase C enzymes)
(3) Hpt transporters: used for G6P acquisition
(4) ActA polymerization at poles of listeria mediates push into neighbouring cells when critical mass reached

Question 6

Characteristics of Mycobacterium tuberculosis

Answer 6

Gram-positive aerobe, Actinobacteria, found only in human, obligate human pathogen

Question 7

Tuberculosis

Answer 7

Phagocytosis into cells, uses EXS-1 system (T7SS) to eject effectors into host cells: Culture filtrate protein and early secretory antigenic target, which forms heterodimer

Question 8

M-Tb vaccine

Answer 8

Uses live Mtb, non-functional EXS-1 system, effectiveness is low since dominant antigens (CFP and ESAT) are not used