The LL-23V9 peptide had significantly increased activity compared to LL-23; however, GI-20, the central fragment of LL-37, had increased activity against Phil82 as compared to either LL-23 or LL-23V9
The LL-23V9 peptide had significantly increased activity compared to LL-23; however, GI-20, the central fragment of LL-37, had increased activity against Phil82 as compared to either LL-23 or LL-23V9. peptides against a strain of pandemic H1N1 of 2009 (A/California/04/09/H1N1 or Cal09). Unexpectedly, LL-37 had markedly reduced activity against Cal09 using several cell types and assays of antiviral activity. A mutant viral strain containing just the hemagglutinin (HA) of 2009 pandemic H1N1 was inhibited by LL-37, suggested that genes other than the HA are involved in the resistance of pH1N1. In contrast, GI-20 did UK 14,304 tartrate inhibit Cal09. In conclusion, the central helix of LL-37 incorporated in GI-20 appears to be required for optimal antiviral activity. The finding that GI-20 inhibits Cal09 suggests that it may be possible to engineer derivatives of LL-37 with improved antiviral properties. Introduction Like the defensins, the cathelicidins are a large family of cationic antimicrobial peptides expressed in many species and have broad UK 14,304 tartrate spectrum antimicrobial activity. Despite this, hCAP18/LL-37 is the only known human cathelicidin . The hCAP18 is 18kD precursor protein with a signal peptide, a cathelin-like domain and antimicrobial domain. LL-37 is a 37- amino acid cationic peptide produced by cleavage of the anti-microbial domain from the hCAP18 protein. Like many other antimicrobial peptides LL-37 is cationic. LL-37 is implicated in host defense against a variety of infections [1C4]. It is produced by neutrophils, macrophages and various epithelial cells as well. LL37 concentration can range from 2C5 g/ml (0.4C1M) in bronchoalveolar lavage fluid from healthy individuals and can increase up to 20 g/ml (2.2M) UK 14,304 tartrate during infections. In nasal secretions its concentration can vary from 1.2C80 g/ml [5, 6]. There is mounting evidence that LL-37 may play a role in host defense against influenza A virus (IAV) through antiviral and immune-modulatory activities. LL-37 improves outcome of IAV infection in mice through inhibition of viral replication and reduction of virus-induced pro-inflammatory cytokine generation . Upregulation of LL-37 expression by stimulation with leukotriene B4 correlated with improved outcome of IAV infection in mice . We have partially characterized the mechanism of anti-IAV activity of LL-37 . LL-37 does not block hemagglutination activity, cause viral aggregation, or reduce viral uptake by epithelial cells, rather it inhibits viral replication at a post-entry step prior to viral RNA or protein synthesis in the cell . Likely sources of LL-37 in the IAV-infected respiratory tract include infiltrating neutrophils , macrophages  and respiratory epithelial cells . LL-37 is an amphipathic peptide with a predominantly hydrophobic surface and a cationic surface. In addition to LL-37, several active fragments of smaller size are produced in vivo, including LL-23 which contains the 23 N-terminal amino acids of LL-37 . Intensive studies have been undertaken to determine the functional roles of different domains of LL-37 with the goal of developing peptides with increased anti-microbial or immune modulatory activity. Wang et al. has recently shown that LL-23 has limited antibacterial activity and noted that it has a single hydrophilic (serine) interruption in its hydrophobic surface (Fig 1). Replacement of this serine with valine (LL-23V9) significantly improved anti-bacterial activity . The smallest fragment of LL-37 that retains antibacterial activity is KR-12 . This peptide retains the core amphipathic helix structure of LL-37 and carries 5 cationic residues. The slightly larger peptide, FK-13 is the smallest peptide having HIV neutralizing activity . A larger peptide, GI-20 has strong anti-HIV activity comparable to full length LL-37 . Open in a separate window Fig 1 LL-37 and derived peptides employed in this study.Panel A. Shows peptide regions corresponding to the parent LL-37 as indicated with pairs of arrows and residue numbers. Note that GI-20 corresponds to residues 13C32 with the positions of I13 and G14 are swapped (9). In addition, the C-terminus of GI-20, as well as FK-13 and KR-12, is amidated. These LL-37 fragments are named in the same manner as LL-37 by taking the first two amino acids in single-letter code followed by peptide length. Panel B. Biophysical properties of the peptides obtained from or calculated using the Antimicrobial Peptide Database (test or ANOVA with post hoc test (Tukeys). ANOVA was used for multiple comparisons to a single control. P values less than or equal to 0.05 were considered significant. Results Antiviral activity of LL-37 and derived fragments against seasonal H3N2 IAV and mouse-adapted PR-8 H1N1 IAV Fig 1 depicts the different LL-37 derived peptides used in this study. Although LL-37 had clear dose-related antiviral Rabbit Polyclonal to AP-2 activity against the seasonal Phil82.