Pathogen-mediated manipulation of arthropod microbiota to promote infection

Abstract

Arthropods transmit diverse infectious agents; however, the ways microbes influence their vector to enhance colonization are poorly understood.Ixodes scapularisticks harbor numerous human pathogens, includingAnaplasma phagocytophilum,the agent of human granulocytic anaplasmosis. We now demonstrate thatA. phagocytophilummodifies theI. scapularismicrobiota to more efficiently infect the tick.A. phagocytophiluminduces ticks to expressIxodes scapularisantifreeze glycoprotein (iafgp), which encodes a protein with several properties, including the ability to alter bacterial biofilm formation. IAFGP thereby perturbs the tick gut microbiota, which influences the integrity of the peritrophic matrix and gut barrier—critical obstacles forAnaplasmacolonization. Mechanistically, IAFGP binds the terminald-alanine residue of the pentapeptide chain of bacterial peptidoglycan, resulting in altered permeability and the capacity of bacteria to form biofilms. These data elucidate the molecular mechanisms by which a human pathogen appropriates an arthropod antibacterial protein to alter the gut microbiota and more effectively colonize the vector.

A Tick Antivirulence Protein Potentiates Antibiotics against Staphylococcus aureus

“…IAFGP and the 24-amino-acid peptide derived from IAFGP, peptide P1 (PARKARAATAATAATAATAATAAT), reduce S. aureus biofilms, including those by methicillin-resistant S. aureus (MRSA) (18,19). Having determined 0.1 mg/ml of IAFGP or P1 yields the strongest effects against S. aureus biofilms without any adverse effects on growth (see Fig.…”

“…Having determined 0.1 mg/ml of IAFGP or P1 yields the strongest effects against S. aureus biofilms without any adverse effects on growth (see Fig. S1A in the supplemental material) (18,19), using a microplate assay we evaluated whether 0.1 mg/ml IAFGP or P1 enhances traditional antibiotic therapy against S. aureus. We measured the MIC of each antibiotic against two S. aureus isolates, a laboratory strain (SA113) and a common methicillin-resistant strain (USA300 JE2), in liquid culture and in the presence of recombinant glutathione S-transferase (GST)-tagged IAFGP, GST alone, P1 peptide, or its scramble control peptide, sP1 (AATAATATAAARRAAAAPTTAKTT).…”

“…Having explored the synergistic properties of IAFGP with antibiotics using transgenic flies and mice ( Fig. 1 and 2), we next sought to investigate the role of P1, an IAFGP derivative (18,19), in synergizing with antibiotics in vivo using two different infection models. Similar to our experiments with the transgenic flies, we assessed synergy of antibiotics with P1 using the control mCherry-expressing transgenic D. melanogaster infected with S. aureus.…”

“…Transpeptidase enzymes are inactivated by ␤-lactam antibiotics through their direct binding with the enzyme, while vancomycin binds the terminal D-Ala-D-Ala residues and inhibits the cross-linking between glycan strands (23). We have shown that IAFGP and P1 can directly bind the terminal (5th) D-alanine residue of the nascent S. aureus peptidoglycan and in doing so alters peptidoglycan in a nonlethal fashion, and this binding is directly correlated with an inhibition of bacterial biofilms (19). We propose the antivirulence properties of IAFGP in altering biofilms, through targeted binding and manipulation of peptidoglycan, can function synergistically with select antibiotics to improve treatment against bacterial infection.…”

“…In doing so, we identified peptide P1, a 24-aminoacid peptide composed of a PARKAR spacer followed by 6 AAT triplets, which phenocopied IAFGP in inhibiting Gram-positive bacterial biofilms in vitro and in vivo, including those by S. aureus and MRSA (18). More recently, we identified the mechanism by which IAFGP and P1 inhibited biofilms among Gram-positive pathogens, including S. aureus: binding and targeted manipulation of the bacterial peptidoglycan (19).…”