Frog skin cultures secrete anti-yellow fever compounds

Abstract

There is an urgent need to develop novel antimicrobial substances. Antimicrobial peptides (AMPs) are considered as promising candidates for future therapeutic use. Because of the re-emergence of the Flavivirus infection, and particularly the yellow fever virus (YFV), we have compared the antiviral activities from skin secretions of seven different frog species against YFV (strain 17D). Secretions from Sphaenorhynchus lacteus, Cryptobatrachus boulongeri and Leptodactylus fuscus displayed the more powerful activities. S. lacteus was found to inhibit viral lysis of Vero E6 cells even at the highest viral concentration evaluated of 10 LD. We also report the identification of a novel frenatin-related peptide from S. lacteus and found that this peptide-on its own-can lead to 35% protection against YVF, while displaying no cytotoxicity against somatic cells even at fivefold higher concentrations. These results are attractive and support the need for continued exploration of new sources of AMPs from frog skin secretions such as those described here in the development of new compounds for the treatment of infectious diseases in general and specific viral infections in particular.

Unveiling the Multifaceted Mechanisms of Antibacterial Activity of Buforin II and Frenatin 2.3S Peptides from Skin Micro-Organs of the Orinoco Lime Treefrog (Sphaenorhynchus lacteus)

“…The protein expression was confirmed by proteomic analysis of the secretions obtained from the SMOs culture of S. lacteus [25]. Here, both peptides were synthesized according to the sequences identified in previous studies [19,25]. The sequence alignment of the primary structure of the peptides buforins I and II and Parasin I with a fragment of histone H2A shows that the peptides contain almost identical sequences to the parental histone H2A, only differing in their size and region location (Figure 1).…”

“…We report here, for the first time, the presence of BF2 in secretions of skin micro-organs of S. lacteus . Besides, in this work we have characterized for the first time a novel frenatin peptide (F2.3S) that was recently discovered in SMOs of S. lacteus in our laboratory [19]. …”

“…The peptides are 16 to 17 amino acid long and share a high sequence identity, showing punctual variations at the C-terminus. In particular, frenatin F2.3S was identified in our laboratory from in vitro skin micro-organs (SMOs) of S. lacteus and shares low sequence identity with previously described frenatins 1 and 3 [19,20], such as frenatin 1 from L. infrafrenata and Frenatin 2D from Discoglossus sardus [16,21]. In contrast, frenatin 2.1S, 2.2S and 2.3S from S. lacteus conform a highly homologous group with reported antimicrobial activity against both Gram-positive and Gram-negative bacteria, including reference species and clinical strains [16,22].…”

“…In contrast, frenatin 2.1S, 2.2S and 2.3S from S. lacteus conform a highly homologous group with reported antimicrobial activity against both Gram-positive and Gram-negative bacteria, including reference species and clinical strains [16,22]. Moreover, our group found that F2.3S has the capacity to protect cells from yellow fever virus infection [19]; a property that might be related to the immunomodulatory properties reported for the peptides of frenatin family [18]. The immunomodulatory activity was reported especially for frenatin 2.1 due to its capacity to differentially stimulate macrophages in order to produce pro-inflammatory (TNFα, IL-23, IL-6) and anti-inflammatory (IL-10) cytokines in mononuclear cells of mouse peritoneum and spleen [23].…”

“…The immunomodulatory activity was reported especially for frenatin 2.1 due to its capacity to differentially stimulate macrophages in order to produce pro-inflammatory (TNFα, IL-23, IL-6) and anti-inflammatory (IL-10) cytokines in mononuclear cells of mouse peritoneum and spleen [23]. In spite of the previous studies about the antimicrobial and immunomodulatory activities of frenatins [19], the mechanism of action of F2.3S remains unknown. …”