Bacteria avoid protective immunity

Question 1

Examples of ways in which bacteria avoid protective immunity

Answer 1

modulators on pathogen surface. Inhibit phagocytosis. Interfere with TLR signalling pathway, altering interferon and cytokine production.

Question 2

Gram negative vs Gram positive

Answer 2

Both: capsule, cytoplasmic membrane.
Gram +ve: no LPS, thick peptidoglycan.
Gram -ve: LPS, thin peptidoglycan

Question 3

Antibodies in protection

Answer 3

Protect by recognising epitopes of surface proteins and polysaccharides

Question 4

CD4 and CD8 in protection

Answer 4

Protect by recognising protein epitopes presented by MHCI or MHCII

Question 5

Antigenic Diversity

Answer 5

modulation of surface structure to avoid immune recognition

Question 6

consequences of antigenic diversity

Answer 6

serious infection and death.
chronic, persistent or latent disease.
ability of the same bacterial species to infect a host time and time agai.
difficulties in devising vaccines.

Question 7

How many serotypes of S. pneumoniae capsule

Answer 7

over 90

Question 8

How are antibodies protective against the Streptococcus pneumoniae?

Answer 8

Recognise key polysaccharides within the capsule. Protective as they agglutinate, opsonise and fix complement.

Question 9

Serotype 9A of S. pneumoniae

Answer 9

Glucose - Glucuonic acid - Galactose - N-acetyle manosamine - Glucose

Question 10

Serotype 9L of S. pneumoniae

Answer 10

Glucose - Glucose - Galactose - Mannose - Glucose

Question 11

Serotype 14 of S. pneumoniae

Answer 11

Galactose - Glucose - Galactose - Glucose

Question 12

Salmonella enterica

Answer 12

different strains have different O-antigens (64 described)

Question 13

Antigenic diversity at strain level

Answer 13

During course of infection, a particular bacterium strain changes its antigenic makeup - it’s a race against the immune system

Question 14

phase variation

Answer 14

genes can be re-arranged or switched on/off. reversible process. enable bacteria to change the way they express protective antigens

Question 15

phase variation in Neisseria gonorrhoeae

Answer 15

1. N. gonorrhoeae attach to epithelial cell surface (with help from surface proteins, OPA proteins and type IV pili).
2. Invade cells and deeper tissues.
3. Undergo another cycle of infection using attachment proteins.

Question 16

Type IV Pili

Answer 16

Encoded by pilin genes. Allow bacteria to adhere to genital tract. Attach to host cell surface as at the tip of each pilus is a particular protein that docks to the receptor on the host surface

Question 17

pilin genes

Answer 17

mosaic of conserved sequences and variable minicasettes (mc1 - mc6).
Up to 20 pil genes.
One is expressed at any given time (pilE)
have many others within the chromosome that have a different composition of variable regions –> change these to create new versions
non-expressed are called pilS

Question 18

Opa proteins

Answer 18

Foudn in Neisseria meniingitidis and gonorrhoeae
Opacity associated proteins.
bacteria contain multiple (up to 12) opa genes –> switched on or off

Question 19

Opa proteins in a plate

Answer 19

Bacteria producing Opa proteins are opaque.

Bacteria which do not produce Opa proteins are transparent.

Question 20

Slipped Strand Mispairing

Answer 20

Bacteria can switch Opa proteins on or off.
Loops out part of the encoding gene so it translates either in or out of frame. Repeated sequences in the gene - replicated then gene switched off.