Immune evasion of bacterial infection

Question 1

How can bacteria evade innate immunity

Answer 1

• Neutralization of antimicrobial peptides
• Complement neutralization
• Prevent phagocytosis

Question 2

How do bacteria prevent phagocytosis, a part of the innate escape

Answer 2

• Inhibition of chemotaxis, so the phagocytes doesn’t migrate towards them
• Bacterial surface structures that block phagocytosis by preventing Ab binding to the capsule by having proteins that bind to the Fc region instead. Bacteria also have clumping factors that makes it harder for the phagocyte to recognize it. Also biofilm formation
• killing of phagocytes
• Evading bacterial killing within macrophages

Question 3

How can bacteria evade the adaptive immunity

Answer 3

• Molecular mimicry, bacteria can attract circulating proteins to its own surface so it doesn’t get recognized
• Suppression and degradation of antibodies - expression IgG proteases and dehydrolysases at its surface
• Hiding inside cells like thrombi
• Super antigens - activates all T cells

Question 4

Other than the normal bacterial IS evasion, how can Gram+ bacteria (Staphylococci and streptococci) immune evade

Answer 4

• Intra cellular aggregation –> Eap - These can facilitate the adhesion of bacteria to each other and to the host cells, this has been shown to lock the neutrophil recruitment
• Surface adherence –> Extra cellular fibrinogen bindning protein.