Caerin 11

The host defense peptide caerin 1.9 was originally isolated from skin secretions of an Australian tree frog and inhibits the growth of a wide range of bacteria in vitro. In this study, we demonstrated that caerin 1.9 shows high bioactivity against several bacteria strains, such as Staphylococcus aureus, Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus haemolyticus in vitro. Importantly, unlike the antibiotic Tazocin, caerin 1.9 does not induce bacterial resistance after 30 rounds of in vitro culture. Moreover, caerin 1.1, another peptide of the caerin family, has an additive antibacterial effect when used together with caerin 1.9. Furthermore, caerin 1.1 and 1.9 prepared in the form of a temperature-sensitive gel inhibit MRSA growth in a skin bacterial infection model of two murine strains. These results indicate that caerin 1.1 and 1.9 peptides could be considered an alternative for conventional antibiotics. IMPORTANCE Antibiotic-resistant bacteria cause severe problems in the clinic. We show in our paper that two short peptides isolated from an Australian frog and prepared in the form of a gel are able to inhibit the growth of antibiotic-resistant bacteria in mice, and, unlike antibiotics, these peptides do not lead to the development of peptide-resistant bacteria strains.

Antibiotic resistance-related bacterial infections and cancers become huge challenges in human health in the 21st century. A number of naturally derived antimicrobial peptides possess multiple functions in host defense, including anti-infective and anticancer activities. One of which is known as the caerin 1 family peptides. The microbicidal properties of these peptides have been long discussed. The recent studies also established the usage of two members in this family, caerin 1.1 and caerin 1.9, in antimultiple antibiotic-resistant bacteria species. It is increasingly evident that caerin 1.1 and caerin 1.9 also contain additional activities in the suppression of tumor. In this review, we briefly outline the therapeutic potentials and possible mechanism of action of caerin 1.1 and 1.9 in the treatment of multiple antibiotic-resistant bacterial infection and cancer immunotherapy.

Objective: To investigate the effect of the 131I-labeled high-affinity peptides Caerin 1.1 and Caerin 1.9 for the treatment of A549 human NSCLC cells. Methods: ① 3-[4,5-Dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and plate clone formation assays were performed to confirm the in vitro anti-tumor activity of Caerin 1.1 and Caerin 1.9. ② Chloramine-T was used to label Caerin 1.1 and Caerin 1.9 with 131I, and the Cell Counting Kit 8 assay was performed to analyze the inhibitory effect of unlabeled Caerin 1.1, unlabeled Caerin 1.9, 131I-labeled Caerin 1.1, and 131I-labeled Caerin 1.9 on the proliferation of NSCLC cells. An A549 NSCLC nude mouse model was established to investigate the in vivo anti-tumor activity of unlabeled Caerin 1.1, unlabeled Caerin 1.9, 131I-labeled Caerin 1.1, and 131I-labeled Caerin 1.9. Results: ① Caerin 1.1 and Caerin 1.9 inhibited the proliferation of NSCLC cells in vitro in a concentration-dependent manner. The half-maximal inhibitory concentration was 16.26 µg/ml and 17.46 µg/ml, respectively, with no significant intergroup difference (P>0.05). ② 131I-labeled Caerin 1.1 and 131I-labeled Caerin 1.9 were equally effective and were superior to their unlabeled versions in their ability to inhibit the proliferation and growth of NSCLC cells (P>0.05).