Litoria Caerulea Research Articles

Caerin 1.1 and 1.9 peptides halt B16 melanoma metastatic tumours via expanding cDC1 and reprogramming tumour macrophages

BackgroundCancer immunotherapy, particularly immune checkpoint inhibitors (ICBs) such as anti-PD-1 antibodies, has revolutionised cancer treatment, although response rates vary among patients. Previous studies have demonstrated that caerin 1.1 and 1.9, host-defence peptides from the Australian tree frog, enhance the effectiveness of anti-PD-1 and therapeutic vaccines in a murine TC-1 model by activating tumour-associated macrophages intratumorally.MethodsWe employed a murine B16 melanoma model to investigate the therapeutic potential of caerin 1.1 and 1.9 in combination with anti-CD47 and a therapeutic vaccine (triple therapy, TT). Tumour growth of caerin-injected primary tumours and distant metastatic tumours was assessed, and survival analysis conducted. Single-cell RNA sequencing (scRNAseq) of CD45+ cells isolated from distant tumours was performed to elucidate changes in the tumour microenvironment induced by TT.ResultsThe TT treatment significantly reduced tumour volumes on the treated side compared to untreated and control groups, with notable effects observed by Day 21. Survival analysis indicated extended survival in mice receiving TT, both on the treated and distant sides. scRNAseq revealed a notable expansion of conventional type 1 dendritic cells (cDC1s) and CD4+CD8+ T cells in the TT group. Tumour-associated macrophages in the TT group shifted toward a more immune-responsive M1 phenotype, with enhanced communication observed between cDC1s and CD8+ and CD4+CD25+ T cells. Additionally, TT downregulated M2-like macrophage marker genes, particularly in MHCIIhi and tissue-resident macrophages, suppressing Cd68 and Arg1 expression across all macrophage types. Differential gene expression analysis highlighted pathway alterations, including upregulation of oxidative phosphorylation and MYC target V1 in Arg1hi macrophages, and activation of pro-inflammatory pathways in MHCIIhi and tissue-resident macrophages.ConclusionOur findings suggest that caerin 1.1 and 1.9, combined with immunotherapy, effectively modulate the tumour microenvironment in primary and secondary tumours, leading to reduced tumour growth and enhanced systemic immunity. Further investigation into these mechanisms could pave the way for improved combination therapies in advanced melanoma treatment.

Spontaneous reoccurrence of Batrachochytrium dendrobatidis infections in Australian green tree frogs (Litoria caerulea) following apparently successful heat therapy: Case report.

Heat therapy has been reported as a safe, effective, and readily available treatment method for heat-tolerant frogs infected with Batrachochytrium dendrobatidis (Bd). We treated wild-caught Australian green tree frogs (Litoria caerulea) infected with Bd using two periods of elevated ambient room temperature (28.2-30.3°C for 7 weeks followed by 28.9-34.1°C for 4 weeks). Frogs exhibited persistent and even increasing infection loads in the first treatment period despite prolonged exposure to elevated temperatures, likely due to the presence of cooler microenvironments within their enclosure (25.5-27.0°C). All frogs eventually returned negative qPCR tests for Bd at the end of the second treatment period, but detectable infections reoccurred one month after frogs were returned to standard housing temperatures (21.2-28.7°C). Our findings suggest that elevated ambient temperature alone might not eliminate Bd in vivo but can reduce infections loads such that they are undetectable by qPCR analysis of skin swabs. Additional factors, such as cooler microenvironments within enclosures or relative humidity, may influence the success of heat therapy. We recommend further research into the combined effects of temperature and humidity during heat therapy and emphasize the importance of accurate temperature measurements as well as post-treatment monitoring at Bd-permissive temperatures to confirm successful clearance of infections.

A new species of Australotaenia (Cestoda: Proteocephalidae) from a hylid frog in Australia

A new species of the little-known genus Australotaenia de Chambrier & de Chambrier, 2010 is described from Ranoidea australis (Gray) (Anura: Hylidae), commonly known as the giant frog, northern snapping frog or round frog and which is a burrowing frog species native to Australia. Australotaenia hobbsi n. sp. is the fourth species of the genus, but the first taxon found in a burrowing frog and in northern Australia. The other species were found in Australian tree frogs (Litoria spp.) in southwestern and southeastern Australia, and in the homalopsid snake Enhydris enhydris (Schneider) in Cambodia. Australotaenia hobbsi n. sp. differs from its congeners (i) by the wider strobila (maximum body width 1,750 µm versus < 930 µm), scolex (570 µm versus < 390 µm) and suckers (diameter 215–230 µm versus < 140 µm); (ii) by the smaller relative size of the cirrus sac (12–15% of proglottid width versus 17–33%); (iii) by the absence of a vaginal sphincter (present in the other three species); (iv) different arrangement of the inner longitudinal musculature, which consists of a few individual muscle fibres (in contrast to the fibres grouped in bundles in other species). Australotaenia species and Pangasiocestus romani Scholz & de Chambrier, 2012 from the spot pangasius Pangasius lernaudii Boucourt, both of the subfamily Acanthotaeniinae, are unique among proteocephalids in terms of intermediate uterine development, with a high concentration of chromophilic cells around the tip of the lateral uterine diverticula.

It's not easy being green: Comparing typical skin colouration among amphibians with colour abnormalities associated with chromatophore deficits.

Amphibians can obtain their colour from a combination of several different pigment and light reflecting cell types called chromatophores, with defects in one or several of the cells leading to colour abnormalities. There is a need for better recording of colour abnormalities within wild amphibian populations, as this may provide baseline data that can be used to determine changes in environmental conditions and population dynamics, such as inbreeding. In this study, we provide records of several types of chromatophore deficiencies, including those involving iridophores, xanthophores and melanophores, among two Australian tree frog species; the green and golden bell frog, Litoria aurea, and the eastern dwarf tree frog, L. fallax. We explore these colour abnormalities in terms of the chromatophores that have likely been affected and associated with their expression, in combination with typical colour phenotypes, colour variations and colour changes for these species. We intend for our photographs to be used as a visual guide that addresses the need for more accessible information regarding the physical manifestation of different chromatophore defects among amphibians.

Broad-scale pesticide screening finds anticoagulant rodenticide and legacy pesticides in Australian frogs

Pesticide contamination poses a significant threat to non-target wildlife, including amphibians, many of which are already highly threatened. This study assessed the extent of pesticide exposure in dead frogs collected during a mass mortality event across eastern New South Wales, Australia between July 2021 and March 2022. Liver tissue from 77 individual frogs of six species were analysed for >600 legacy and contemporary pesticides, including rodenticides. More than a third (36 %) of the liver samples contained at least one of the following pesticides: brodifacoum, dieldrin, DDE, heptachlor/heptachlor epoxide, fipronil sulfone, and 2-methyl-4-chlorophenoxyacetic acid (MCPA). Brodifacoum, a second-generation anticoagulant rodenticide, was found in four of the six frog species analysed: the eastern banjo frog (Limnodynastes dumerilii), cane toad (Rhinella marina), green tree frog (Litoria caerulea) and Peron's tree frog (Litoria peronii). This is the first report of anticoagulant rodenticide detected in wild amphibians, raising concerns about potential impacts on frogs and extending the list of taxa shown to accumulate rodenticides. Dieldrin, a banned legacy pesticide, was also detected in two species: striped marsh frog (Limnodynastes peronii) and green tree frog (Litoria caerulea). The toxicological effects of these pesticides on frogs are difficult to infer due to limited comparable studies; however, due to the low frequency of detection the presence of these pesticides was not considered a major contributing factor to the mass mortality event. Additional research is needed to investigate the effects of pesticide exposure on amphibians, particularly regarding the impacts of second-generation anticoagulant rodenticides. There is also need for continued monitoring and improved conservation management strategies for the mitigation of the potential threat of pesticide exposure and accumulation in amphibian populations.

Stuck on you: Wind‐dispersed seeds attach to the external surfaces of a tree frog

AbstractMany plants exploit the ability of animals to move in order to disperse their pollen and seeds. Despite the growing understanding of the role animals play in the reproductive lives of plants, there are few examples of amphibians contributing to these processes. We report on an Australian tree frog, Litoria fallax, interacting with and likely moving seeds of the broad‐leaved cumbungi, Typha orientalis, over short distances via external transport. Field observations revealed both juvenile and adult L. fallax individuals carrying typha seeds, which were adhered to the skin on the feet, legs, belly and dorsum. Approximately 30% of observed frogs were found to be carrying 1–14 seeds at a time. The small size and specialised fibre tufts of typha seeds, which enable them to be primarily dispersed by wind, also make them susceptible to being unintentionally picked up and transported by L. fallax as they move through aquatic environments. The moist surfaces of frogs, coupled with their presence in freshwater systems that can be dominated by typha, create favourable conditions for seed attachment. These findings highlight a previously unknown interaction between an amphibian and a plant that enables seed dispersal, supporting the need for further exploration into unexpected plant vectors.

Host-defence caerin 1.1 and 1.9 peptides suppress glioblastoma U87 and U118 cell proliferation through the modulation of mitochondrial respiration and induce the downregulation of CHI3L1.

Glioblastoma, the most aggressive form of brain cancer, poses a significant global health challenge with a considerable mortality rate. With the predicted increase in glioblastoma incidence, there is an urgent need for more effective treatment strategies. In this study, we explore the potential of caerin 1.1 and 1.9, host defence peptides derived from an Australian tree frog, in inhibiting glioblastoma U87 and U118 cell growth. Our findings demonstrate the inhibitory impact of caerin 1.1 and 1.9 on cell growth through CCK8 assays. Additionally, these peptides effectively curtail the migration of glioblastoma cells in a cell scratch assay, exhibiting varying inhibitory effects among different cell lines. Notably, the peptides hinder the G0/S phase replication in both U87 and U118 cells, pointing to their impact on the cell cycle. Furthermore, caerin 1.1 and 1.9 show the ability to enter the cytoplasm of glioblastoma cells, influencing the morphology of mitochondria. Proteomics experiments reveal intriguing insights, with a decrease in CHI3L1 expression and an increase in PZP and JUNB expression after peptide treatment. These proteins play roles in cell energy metabolism and inflammatory response, suggesting a multifaceted impact on glioblastoma cells. In conclusion, our study underscores the substantial anticancer potential of caerin 1.1 and 1.9 against glioblastoma cells. These findings propose the peptides as promising candidates for further exploration in the realm of glioblastoma management, offering new avenues for developing effective treatment strategies.

Proteomic analysis of anti-MRSA activity of caerin 1.1/1.9 in a murine skin infection model and their in vitro anti-biofilm effects against Acinetobacter baumannii.

Caerin 1 is a family of host defense peptides with antimicrobial properties originally isolated from the Australian tree frog. Both caerin 1.1 and caerin 1.9 have been demonstrated to inhibit infections caused by multiple antibiotic-resistant bacteria, both in vitro and in vivo. In this current study, we conducted a comparison of the minimum inhibitory concentrations of caerin 1.1 and caerin 1.9 (referred to as caerin 1.1/1.9) with commonly used antibiotics against various bacteria, including Staphylococcus aureus, Copper-Green Pseudomonas aeruginosa, Acinetobacter baumannii, and Streptococcus haemolyticus. Our findings reveal that caerin 1.1/1.9 not only prevent the formation of biofilms by A. baumannii but also exhibit a therapeutic effect on established biofilms. Furthermore, our study demonstrates that caerin 1.1/1.9 significantly inhibit the growth of methicillin-resistant Staphylococcus aureus (MRSA) strains in a murine skin infection model. A quantitative proteomic analysis conducted as part of our study indicates that caerin 1.1/1.9 primarily activate oxidative phosphorylation pathways, along with several pathways associated with tissue repair and growth. These findings were observed in comparison to untreated tissues that were infected with MRSA in mice. In summary, our research outcomes suggest that caerin 1.1/1.9 exhibit the potential to serve as promising drug candidates for treating complicated antibiotic-resistant bacterial infections in humans. IMPORTANCE Caerin 1.1 and caerin 1.9, natural antimicrobial peptides derived from tree frogs, have demonstrated the ability to inhibit the growth of antibiotic-resistant bacteria, comparable to certain widely used antibiotics. Additionally, these peptides exhibit the capacity to prevent or treat biofilms formed by bacteria in conjunction with bodily components. The mechanisms underlying their antibacterial effects were investigated through a mouse model of bacterial skin infection, utilizing proteomic analysis as a technological approach.

First description of buccopharyngeal anatomy in Pelodryadinae larvae: Morphological comparison and systematic implications (Anura: Hylidae: Pelodryadinae: Litoria rubella and Ranoidea caerulea).

Pelodryadinae, the Australian tree frogs, is a monophyletic group endemic to the Australo-Papuan region. Although we have a relatively good knowledge about tadpoles' phenotypic diversity in terms of external morphology, information about internal anatomy is rare for the subfamily; for instance, their buccopharyngeal cavity is completely unknown. Herein I describe for the first time the buccopharyngeal anatomy of two pelodryadins: Litoria rubella and Ranoidea caerulea. I compare my results with available evidence from Phyllomedusidae, that is, the sister clade to Pelodryadinae, and briefly comment on buccopharyngeal cavity within Hylidae. Both species can be readily distinguished based on lateral ridge, postnarial, buccal roof arena, infralabial papillae, and lingual papillae. Variation between the two species may suggest a large diversity within Pelodryadinae. Pelodryadinae and Phyllomedusinae present similar buccopharyngeal morphologies, although Agalychnis callidryas has a unique morphology and putative apomorphic transformations can be observed in Pithecopus + Phyllomedusa, Ranoidea, and Phasmahyla.

Discovery of a novel antifungal agent: All-hydrocarbon stapling modification of peptide Aurein1.2.

Aurein1.2 is secreted by the Australian tree frog Litoria aurea and is active against a broad range of infectious microbes including bacteria, fungi, and viruses. Its antifungal potency has garnered considerable interest in developing novel classes of natural antifungal agents to fight pathogenic infection by fungi. However, serious pharmacological hurdles remain, hindering its clinical translation. To alleviate its susceptibility to proteolytic degradation and improve its antifungal activity, six conformationally locked peptides were synthesized through hydrocarbon stapling modification and evaluated for their physicochemical and antifungal parameters. Among them, SAU2-4 exhibited significant improvement in helicity levels, protease resistance, and antifungal activity compared to the template linear peptide Aurein1.2. These results confirmed the prominent role of hydrocarbon stapling modification in the manipulation of peptide pharmacological properties and enhanced the application potential of Aurein1.2 in the field of antifungal agent development.

Isolation of Brucella inopinata from a White's tree frog (Litoria caerulea): pose exotic frogs a potential risk to human health?

Cold-blooded hosts, particularly exotic frogs, have become a newly recognized reservoir for atypical Brucella species and strains worldwide, but their pathogenicity to humans remains largely unknown. Here we report the isolation and molecular characterization of a B. inopinata strain (FO700662) cultured from clinical samples taken from a captive diseased White's Tree Frog (Litoria caerulea) in Switzerland. The isolation of B. inopinata from a frog along with other reports of human infection by atypical Brucella raises the question of whether atypical Brucella could pose a risk to human health and deserves further attention. The investigations included histopathological analysis of the frog, bacterial culture and in-depth molecular characterization of strain FO700662 based on genome sequencing data. Originally identified as Ochrobactrum based on its rapid growth and biochemical profile, strain FO700622 was positive for the Brucella- specific markers bcsp31 and IS711. It showed the specific banding pattern of B. inopinata in conventional Bruce-ladder multiplex PCR and also had identical 16S rRNA and recA gene sequences as B. inopinata. Subsequent genome sequencing followed by core genome-based MLST (cgMLST) analysis using 2704 targets (74% of the total chromosome) revealed only 173 allelic differences compared to the type strain of B. inopinata BO1T, while previously considered the closest related strain BO2 differed in 2046 alleles. The overall average nucleotide identity (ANI) between the type strain BO1T and FO700622 was 99,89%, confirming that both strains were almost identical. In silico MLST-21 and MLVA-16 also identified strain FO700662 as B. inopinata. The nucleotide and amino acid-based phylogenetic reconstruction and comparative genome analysis again placed the isolate together with B. inopinata with 100% support. In conclusion, our data unequivocally classified strain FO700622, isolated from an exotic frog, as belonging to B. inopinata.

Male nuptial display colour and vocalisation appear to signal independent information in the whirring tree frog

When different modes of communication are used in combination and for example convey visual and acoustic information, they form a multimodal signal. Frogs are best known for using acoustic communication, but many species also use visual or colour signals, some of which are dynamic, and may be combined with acoustic signals. In this context, the question of whether these two modes of communication reinforce the same message or offer different information is poorly understood. Male whirring tree frogs, Litoria revelata, use a multimodal signal during courtship, which combines a vocalisation and dynamic sexual dichromatism, with nuptial display colours shifting from brown or grey to bright yellow. Here, we examined the properties of the advertisement call and nuptial colour of vocalising male whirring tree frogs and tested whether the two signals were likely to reinforce each other or convey independent information. We found only weak associations between elements of male colouration and vocalisations, suggesting that advertisement calls and nuptial colour do not reinforce each other and that the signals may instead convey different information.Significance statementDynamic nuptial colour and vocalisation in combination is a relatively common multimodal signal in frogs but is unstudied. We looked for relationships between properties of colour and vocalisation in an Australian tree frog to explore whether the two sensory modes formed backup signals or multiple messages. We did not find predictive relationships between nuptial colour and vocalisation, supporting the multiple messages hypothesis and suggesting that nuptial colour is not necessarily directed at females for the purposes of mate attraction, potentially differing from the assumed function of the vocalisation. Our study is also the first to formally characterise aspects of dynamic sexual dichromatism in the whirring tree frog (Litoria revelata) and the first to describe the advertisement call of this species in its southern distribution. Whilst we do not specifically address the function of dynamic sexual dichromatism in this species, our findings do not contradict the existing literature in respect to it being a male-male directed signal.

Invasion of a non‐native anuran likely disrupts pond ecosystems

Abstract Freshwater ecosystems worldwide are under increasing pressure from multiple threats, including invasive species and climate change, with ponds being particularly vulnerable because of their shallow depth and dynamic hydrology. Australian brown tree frogs Litoria ewingii, introduced to New Zealand in 1875, have spread across both main islands, breeding in a large range of shallow fishless ponds. Since native frogs do not produce aquatic tadpoles, any tadpole influence will be novel, so these ecosystems may be especially vulnerable to such influences. To determine the functional role of L. ewingii tadpoles and to uncover potential effects on pond community structure and function, we conducted two 3‐week‐long mesocosm experiments. The first crossed tadpole presence with predatory invertebrate presence. Mesocosms containing tadpoles had a lower biomass of periphyton and macrophytes, and lower abundance of two families of small‐sized invertebrates (Culicidae and Chironomidae) compared to mesocosms without tadpoles, possibly as a consequence of grazing, predation or reduced dipteran oviposition. However, predatory invertebrates did not affect tadpoles except at their smallest stage, so L. ewingii probably are not subject to strong top‐down control by invertebrates in fishless ponds. We evaluated the effects of tadpole density on ecosystem processes in the second experiment where half the mesocosms also were shaded to simulate permanent pond hydrological status; shading stabilised the temperature fluctuations typical of temporary ponds. In shaded mesocosms tadpole density did not change phytoplankton, whereas in unshaded mesocosms, phytoplankton biomass increased with tadpole density, possibly because tadpole excretion enhanced algal growth in high light conditions. Higher densities of tadpoles also decreased dissolved oxygen concentration regardless of shading during the day—potentially an indirect effect of grazing on macrophytes and periphyton reducing photosynthesis. Overall, these non‐native tadpoles are likely to be having large influences on ecosystem processes such as nutrient cycling in small ponds, especially when at high densities. In light of these potential effects on pond ecosystems, and the generalist traits of these frogs which could see them spread to even remote alpine ponds, control measures to prevent further range expansion should be considered in New Zealand.

Dynamics of horizontal walking and vertical climbing in the Australian green tree frog (Ranoidea caerulea).

Despite the high mechanical demands associated with climbing, the ability to ascend vertically has evolved independently in most major animal lineages. However, little is known about the kinetics, mechanical energy profiles or spatiotemporal gait characteristics of this locomotor mode. In this study, we explored the dynamics of horizontal locomotion and vertical climbing on both flat substrates and narrow poles in five Australian green tree frogs (Ranoidea caerulea). Vertical climbing is associated with slow, deliberate movements (i.e. reduced speed and stride frequency and increased duty factors) and propulsive fore-aft impulses in both the forelimb and hindlimb. By comparison, horizontal walking was characterized by a braking forelimb and a propulsive hindlimb. In the normal plane, tree frogs mirrored other taxa in exhibiting a net pulling forelimb and a net pushing hindlimb during vertical climbing. In terms of mechanical energy, tree frogs matched theoretical predictions of climbing dynamics (i.e. the total mechanical energetic cost of vertical climbing was predominantly driven by potential energy, with negligible kinetic contributions). Utilizing power as a means of estimating efficiency, we also demonstrate that Australian green tree frogs show total mechanical power costs only slightly above the minimum mechanical power necessary to climb, highlighting their highly effective locomotor mechanics. This study provides new data on climbing dynamics in a slow-moving arboreal tetrapod and raises new testable hypotheses about how natural selection can act upon a locomotor behavior that is notably constrained by external physical forces.

Paradigm shift in frog sperm cryopreservation: reduced role for non-penetrating cryoprotectants.

Sperm cryopreservation has been recognised as a tool for preventing loss of genetic diversity in amphibians; however, the combined effect of penetrative and non-penetrative cryoprotectants in cryodiluents is poorly understood. We demonstrate a clear benefit of using low concentrations of non-penetrative cryoprotectants when cryopreserving sperm of Australian tree frogs. Sperm cryopreservation protocols have been developed for an increasing number of amphibian species since the recognition of a global amphibian decline. Yet, the development of these protocols has neglected to elucidate the combined effect of the penetrative(PCP) and non-penetrative cryoprotectant (NPCP) on the recovery of live, motile sperm. The two-factor hypothesis of cryoinjury recognises a trade-off between cooling cells slowly enough to allow osmotic dehydration and therefore avoid intracellular ice formation, but fast enough to minimise effects from increasing extracellular osmolality as the frozen fraction of the media increases during freezing. We tested the effect of two concentrations of a PCP (10 and 15% v/v dimethyl sulfoxide (Me2SO)) and two concentrations of an NPCP (1 and 10% w/v sucrose) in various combinations on the sperm of six pelodryadid frogs. In all species, 15% v/v Me2SO with 1% w/v sucrose provided superior post-thaw recovery with high proportions of forward progressive motility, live cells and intact acrosomes (typically >50% for each). Theoretically, it has been suggested that increased NPCP concentration should improve cell survival by increasing the rate and extent of cell dehydration. We suggest, however, that the elevated osmolality in the unfrozen water fraction when 10% sucrose is used may be causing damage to cells via excessive cell shrinkage and solute effects as proposed in the two-factor hypothesis of cryoinjury. We showed this response in sperm across a range of frog species, providing compelling evidence for this hypothesis. We suggest protocol development using the PCP/NPCP ratios demonstrated in our study will be broadly applicable to many amphibian species.

The membrane activity of the antimicrobial peptide caerin 1.1 is pH dependent.

Histidine-rich antimicrobial peptides (AMPs) are an important class of membrane-active peptides that can provide a scaffold to induce pH-sensitive interactions with cell membranes. The Australian tree frog AMP, caerin 1.1 (Cae-1), has three histidine residues, which modify the interactions with neutral and negatively charged lipid systems. NMR and MD simulations showed that in an acidic environment in comparison to physiological conditions, Cae-1 induced greater perturbation of the lipid dynamics and water penetration into the membrane interior. Lipid packing, chemical environment, and dynamics of the phospholipid headgroup were monitored using 31P solid-state NMR. In particular, the CODEX technique revealed that Cae-1 has a large impact on the slow re-orientation of the lipids. 2H solid-state NMR showed that Cae-1 ordered the acyl chains across the hydrophobic core. Interestingly, titration of the paramagnetic Mn2+ into the lipid-AMP systems resulted in extensive quenching of the 13C solid-state NMR signals of the lipid headgroup and acyl chain carbons. These results supported the MD results that showed Cae-1 was mainly inserted within the lipid bilayer structure of both neutral and negatively charged membranes, with the charged residues dragging the water and phosphate groups inwards. This could be an early step in the mechanism of membrane disruption by histidine-rich AMPs and indicated that Cae-1 is potentially forming toroidal pores in bilayers of neutral and negatively charged lipid membranes, especially under acidic conditions.

The membrane activity of the antimicrobial peptide caerin 1.1 is pH dependent

Antimicrobial peptides are an important class of membrane-active peptides that can provide alternatives or complements to classic antibiotics. Among the many classes of AMPs, the histidine-rich family is of particular interest since they may induce pH-sensitive interactions with cell membranes. The AMP caerin 1.1 (Cae-1), from Australian tree frogs, has three histidine residues, and thus we studied the pH dependence of its interactions with model cell membranes. Using NMR spectroscopy and molecular dynamics simulations, we showed that Cae-1 induced greater perturbation of the lipid dynamics and water penetrations within the membrane interior in an acidic environment compared with physiological conditions. Using 31P solid-state NMR, the packing, chemical environment, and dynamics of the lipid headgroup were monitored. 2H solid-state NMR showed that Cae-1 ordered the acyl chains of the hydrophobic core of the bilayer. These results supported the molecular dynamics data, which showed that Cae-1 was mainly inserted within the lipid bilayer for both neutral and negatively charged membranes, with the charged residues pulling the water and phosphate groups inward. This could be an early step in the mechanism of membrane disruption by histidine-rich antimicrobial peptides and indicated that Cae-1 acts via a transmembrane mechanism in bilayers of neutral and anionic phospholipid membranes, especially in acidic conditions.

Early exposure to UV radiation causes telomere shortening and poorer condition later in life.

ABSTRACTDetermining the contribution of elevated ultraviolet-B radiation (UVBR; 280–315 nm) to amphibian population declines is being hindered by a lack of knowledge about how different acute UVBR exposure regimes during early life-history stages might affect post-metamorphic stages via long-term carryover effects. We acutely exposed tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a multi-factorial laboratory experiment, and then reared them to metamorphosis in the absence of UVBR to assess carryover effects in subsequent juvenile frogs. Dose and irradiance of acute UVBR exposure influenced carryover effects into metamorphosis in somewhat opposing manners. Higher doses of UVBR exposure in larvae yielded improved rates of metamorphosis. However, exposure at a high irradiance resulted in frogs metamorphosing smaller in size and in poorer condition than frogs exposed to low and medium irradiance UVBR as larvae. We also demonstrate some of the first empirical evidence of UVBR-induced telomere shortening in vivo, which is one possible mechanism for life-history trade-offs impacting condition post-metamorphosis. These findings contribute to our understanding of how acute UVBR exposure regimes in early life affect later life-history stages, which has implications for how this stressor may shape population dynamics.

Preclinical Pharmacokinetics, Biodistribution, and Acute Toxicity Evaluation of Caerin 1.9 Peptide in Sprague Dawley Rats.

Caerin 1.9 is a natural peptide derived from the skin secretions of the Australian tree frog (Litoria) with broad-spectrum antimicrobial and anticancer bioactivity. It improves the efficacy of a therapeutic vaccine and immune checkpoint inhibitor therapy when injected intratumorally and inhibits TC-1 tumor growth when applied topically through intact skin in a TC-1 murine tumor model. This paper investigated the pharmaceutical kinetic profile, the tissue distribution, and the acute safety investigation of Caerin 1.9 peptide in Sprague Dawley (SD) rats. The results showed that subcutaneous injection of Caerin 1.9 at 100 mg/kg is safe and does not cause mortality or organ malfunction in the recipient rats. For the consecutive injection of F3 at 10 mg/kg, the peak concentration (Cmax) of F3 displayed at 1 hr after injection in male rats was 591 ng/mL, the average drug retention time was 0.807 hr, T1/2 was 4.58 hr, and AUC0-last was 1890 h × ng/mL. In female rats, Cmax was 256 ng/mL, with an average drug retention time of 2.96 hr, T1/2 of 1.33 hr, and AUC0-last of 740 h × ng/mL. The results showed that the concentration of Caerin 1.9 in the peripheral blood peaked at 1 hour. As injected concentration increased, T1/2 extended, and Cmax, AUC0-last, and volume of distribution at a steady state all increased. After 14 days of repeated subcutaneous injection at 10.0 mg/kg, no accumulation of Caerin 1.9 in plasma was observed. The results of tissue distribution showed that the Caerin 1.9 is below the LC-MS/MS detection threshold at a minimum concentration of 40 ng/g. In conclusion, Caerin 1.9 is well tolerated in rats and could be used with current immunotherapies for better management of solid tumors and genital warts.

Novel chytrid pathogen variants and the global amphibian pet trade.

Global wildlife trade spreads emerging infectious diseases that threaten biodiversity. The amphibian chytrid pathogen Batrachochytrium dendrobatidis (Bd) has caused population declines and species extinctions worldwide except in Asia. Fire-bellied toads (Bombina orientalis), exported in large numbers from Asia, are tolerant of Bd and carry hypervirulent ancestral chytrid BdAsia-1 variants. We assayed the virulence of a new isolate of BdAsia-1 on the model Australasian frog host Litoria caerulea. Infected individuals (n = 15) all showed rapid disease progression culminating in death, whereas sham-inoculated individuals (n = 10) presented no clinical signs of disease and all survived (log rank test, χ2 = 15.6, df = 1, p < 0.0001). The virulence of the new isolate of BdAsia-1 is comparable tothe one we assayed previously (χ2 = 0.0, df = 1, p = 0.91). Internationally traded wildlife, even when they appear healthy, can carry hypervirulent variants of pathogens. Once new pathogen variants escape into the environment, native species that have had no opportunity to evolve resistance to them may perish. Our study suggests that hypervirulent pathogens are being spread by the international pet trade. Notifiable wildlife diseases attributable to locally endemic pathogens often fail to generate conservation concern so are rarely subject to border surveillance or import controls. Because of the danger novel variants pose, national border control agencies need to implement disease screening and quarantine protocols to ensure the safety of their endemic fauna.