Low cationicity is important for systemic in vivo efficacy of database-derived peptides against drug-resistant Gram-positive pathogens

Abstract

As bacterial resistance to traditional antibiotics continues to emerge, new alternatives are urgently needed. Antimicrobial peptides (AMPs) are important candidates. However, how AMPs are designed with in vivo efficacy is poorly understood. Our study was designed to understand structural moieties of cationic peptides that would lead to their successful use as antibacterial agents. In contrast to the common perception, serum binding and peptide stability were not the major reasons for in vivo failure in our studies. Rather, our systematic study of a series of peptides with varying lysines revealed the significance of low cationicity for systemic in vivo efficacy against Gram-positive pathogens. We propose that peptides with biased amino acid compositions are not favored to associate with multiple host factors and are more likely to show in vivo efficacy. Thus, our results uncover a useful design strategy for developing potent peptides against multidrug-resistant pathogens.

Sequence Permutation Generates Peptides with Different Antimicrobial and Antibiofilm Activities

“…The antimicrobial activity spectrum of the WW peptide series was performed on a panel of Gram-positive and -negative bacteria using the standard broth micro-dilution method [ 28 ] with minor modifications as described [ 23 ]. The minimal inhibitory concentrations (MIC) of WW291-WW298 against eight bacteria are provided in Table 2 .…”

“…A fluorescence-based assay was performed for the determination the membrane active nature of peptides. A rapid increase in the fluorescence was detected as a consequence of peptide treatment at 3.1 µM, indicating membrane damage ( Figure 3 ) [ 23 ]. In the case of S. aureus USA300 ( Figure 3 A), the peptide WW298 showed a time-dependent fluorescence buildup, much higher than that of WW295.…”

“…For instance, horine, a refined peptide of WW291 with activity mainly against Gram-positive bacterial species [ 26 ], may be used to selectively eliminate MRSA and VRE when they become offensive pathogens in patients. Our previous database discovered anti-MRSA peptide DFTamP1 [ 22 ], as well as its optimized peptides DFT503 and DFT561 [ 23 ], may serve the same purpose. In the current APD [ 9 ], 551 AMPs are annotated to be primarily active against Gram-positive bacteria.…”

“…The antibacterial activity of peptides was evaluated using a standard broth microdilution protocol with minor modifications as previously described [ 23 ]. In brief, logarithmic phase bacterial cultures (i.e., optical density at 600 nm ≈ 0.5) were diluted to OD 600 ~0.001 and partitioned into a 96-well polystyrene microplate at 90 μL per well.…”

“…We have been utilizing database approaches, ranging from database screening to database filtering technology [ 20 , 21 , 22 ]. Recently, we found the importance of low cationicity for systemic efficacy of the database-designed peptides in mice against methicillin-resistant Staphylococcus aureus (MRSA) [ 23 ]. On the basis of this idea, we designed an even shorter peptide WW291 (formerly TetraF2W-RK) [ 24 ].…”