Barrier Epithelia Response Antimicrobial Peptides Mucus escalator Airway Mucus layer Saline Epithelium Mucus secreting goblet cell Cilia Epithelial Cells http mhmicroscopy med unc edu flyer flyer html http users umassmed edu michael sanderson mjslab cilia and calcium text htm Alveolar defense Alveolar space Other constituents Complement IgA Surfactant Microbe Macrophage Capillary Red Blood Cell Of course microbes can defeat these defenses Cilia paralysis Streptococcus pneumoniae Chlamydia pneumoniae Cell entry Mycoplasma pneumoniae Cell adhesion Bordatella pertussis Neisseria meningitidis Microbes can use our immune systems to fight each other H influenzae and S pneumococcus inhabit the same niche in the lung These immune responses block S pneumoniae growth Innate immune responses are generated by H influenzae Early pathogenesis of Anthrax infections Phagocytosis by alveolar macrophage Germination within vacuole Release from vacuole No replication within the macrophage Macrophages move back to lymph nodes following phagocytosis The insect breathing apparatus is also susceptible to infection Tracheal mites Tracheal tube Alas insects do not appear to use mucus Instead insects produce a peritrophic matrix to protect internal epithelia Type 1 peritrophic matrix Adult mosquitoes Type II peritrophic matrix larval mosquitoes Pathogens must pass through the peritrophic matrix Peritrophic matrix Baculovirus digest mucus Gut epithelia Microfilaria Plasmodium digest chitin Secreted antimicrobial peptides Main antimicrobial components of nasal fluid lysozyme lactoferrin defensins Antimicrobial peptide and protein production Constitutive expression ears tears nose skin saliva gut milk genital tract Peptides can also be induced during an infection Tzou et al 2000 Immunity 13 737 48 Human antimicrobial peptides Peptide type a defensin b defensin Cathelicidin Name HNP1 4 HNP5 hBD1 2 hBD3 hBD4 LL 37 Location granulocytes paneth cells gut genital tract skin lung gut epithelium skin lung tonsils testis gastric antrum granulocytes lung skin testis gut lymphocytes Drosophila antimicrobial peptides Type a helical defensin proline rich glycine rich Name cecropin defensin drosomycin drosocin metchinikowin diptericin attacin Activity G G F G G F F GF GG adapted from Bulet et al p 89 107 in Infectious Disease Innate Immunity ed by Ezekowitz and Hoffman 2003 Defensins can be delivered in at least two manners defensins secreted directly from epithelia defensin stored in neutrophil granules and used in vacuoles Defensin structure Ganz 2003 Nat rev immun 3 710 20 Cathelicidins share a common non active pro subunit called cathelin SS SS Cathelin Domain 98 114 aa Cathelicidin 12 100 aa Linear antimicrobial peptide activity AMP insertion destabilizes outer leaflet Antimicrobial peptide Phospholipid Antimicrobial peptide mechanisms Barrel stave pore Peptide crosses both membrane leaflets Torroidal pore Peptide remains in contact with headgroup Are there reasons to believe amps might work in other ways Orthodoxy Alternative The baffling case of buforin II Buforin is a proteolytic product of histone H2A Buforin enters bacterial cells and does not cause lysis Park et al 2000 PNAS 97 8245 What do the bacteria think Treatment of E coli with cecropin A Wong et al 2003 Antimicrobial agents and chemotherapy 47 1 6 Don t go rubbing them all over you body yet Antimicrobial peptides can also act as signaling molecules Three properties of antimicrobial peptides Bacterial responses to antimicrobial peptides Alteration of lipid surface Proteolysis Sequestration Gram positive vs Gram negative cells Gram positive Gram negative outer membrane Peptidoglycan LPS Lipopolysaccharide structure O Antigen R6 Outer core O Antigen Gal 4 R R 5 R3 Inner core Man R 2 Kdo PO4 GLN Abe Glc Rha Gal n 1 40 GLN PO4 Lipid A Salmonella alters its LPS structure in response to AMPs and the altered LPS is a less effective Tlr4 activator Kawasaki K et al J B C 2004 279 20044 8 PhoP Q was originally thought to detect Mg ion concentrations PhoP Q is activated by AMPs and turns on virulence genes Helicobacter secretes a cecropin that activates neutrophils Bylund J et al 2001 Antimicrobial Agents and Chemotherapy June 1700 4 LL37 mediated killing and DNA uptake Lysis of bacteria Secretion of antimicrobial peptides Release of plasmid DNA Uptake and expression Shigella plasmid DNA reduces LL 37 expression Islam et al 2001 Nat Med 7 180 5