Maggot chymotrypsin I from Lucilia sericata is resistant to endogenous wound protease inhibitors

Use of biosurgery for the treatment of foot ulcers infected with therapy-resistant bacteria: a case report

Biosurgery (larval therapy) has been used for centuries. However, in recent times, this treatment has been replaced with the use of antibiotics for the treatment of wounds. Due to increasing antibiotic resistance, larval therapy is once again coming to the fore as an effective and efficient treatment. Due to the increasing ageing population, along with an increase in patients with arterial occlusive disease, diabetes and immobility, the number of patients with hard-to-heal wounds will increase. The stressors associated with wounds, such as pain, limited physical functionality, depression and social withdrawal, have a negative impact on patient quality of life. This case report documents the performance of biosurgery in a patient with multimorbidities.

Anti-inflammatory and wound healing potential of medicinal maggot excretions/secretions at the ocular surface

PURPOSE

In the skin, Lucilia sericata maggot excretions/secretions (ES) accelerate wound healing and limit inflammation. This study aimed to determine whether ES have similar beneficial effects at the ocular surface.

METHODS

Human corneal epithelial cells (HCEC) were cultured with ES and cell viability was determined by the MTT assay. Additionally, mRNA expression of growth factors, antimicrobial peptides (AMPs) and cytokines was assessed by qPCR. ES ability to modulate TLR-induced IL-6 and IL-8 expression was determined by qPCR and ELISA. ES potential to promote corneal healing was evaluated in vitro by a migration assay in HCEC, and in vivo using a mouse model.

RESULTS

ES did not impair HCEC viability up to 25 μg/ml. Among the factors evaluated, only hBD-2 was upregulated (2.5-fold) by 1.5 μg/ml ES after 6 hrs (P = 0.04). In HCEC, ES reduced Poly I:C-induced IL-6 and IL-8 mRNA (P ≤ 0.001) and protein (P ≤ 0.0001) expression. A similar effect was observed with Flagellin (TLR5 agonist) but it was less robust for FSL-1 (TLR2/6 agonist) and Pam3CSK4 (TLR1/2 agonist). The greatest in vitro migration effect was observed with 6.2 μg/ml ES after 44 hrs where gap area compared to vehicle was 53.3 ± 3.7% vs. 72.6 ± 5.4% (P = 0.001). In the mouse model, the maximum healing effect was present with 1.5 μg/ml ES after 12 hrs with a wound area of 19.0 ± 2.7% vs. 60.1 ± 21.6% (P = 0.003) or 77% reduction of the wound area compared to the negative control.

CONCLUSIONS

ES significantly reduce in vitro TLR-induced production of inflammatory cytokines and promote corneal wound healing.

The effect of Lucilia sericata larval excretion/secretion (ES) products on cellular responses in wound healing

Chronic wounds are still regarded as a serious public health concern, which are on the increase mainly due to the changes in life styles and aging of the human population. There are different types of chronic wounds, each of which requires slightly different treatment strategies. Nevertheless, wound bed preparation is included in treatment of all types of chronic wounds and involves tissue debridement, inflammation, and infection control, as well as moisture balance and epithelial edge advancement. Maggot therapy (MT) is a form of biological debridement which involves the application of live medical grade Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) larvae. Whereas it was initially thought to act mainly through debridement, today MT is known to influence all four overlapping physiological phases of wound repair: homeostasis, inflammation, proliferation, and remodelling/maturing. During MT, medical-grade larvae are applied either freely or enclosed in tea-bag like devices (biobag) inside the wounds, which suggests that larva excretion/secretion (ES) products can facilitate the healing processes directly without the need of direct contact with the larvae. This review summarizes the relevant literature on ES-mediated effects on the cellular responses involved in wound healing.

A molecular approach to maggot debridement therapy with Lucilia sericata and its excretions/secretions in wound healing

Chronic wounds caused by underlying physiological causes such as diabetic wounds, pressure ulcers, venous leg ulcers and infected wounds affect a significant portion of the population. In order to treat chronic wounds, a strong debridement, removal of necrotic tissue, elimination of infection and stimulation of granulation tissue are required. Maggot debridement therapy (MDT), which is an alternative treatment method based on history, has been used quite widely. MDT is an efficient, simple, cost-effective and reliable biosurgery method using mostly larvae of Lucilia sericata fly species. Larvae can both physically remove necrotic tissue from the wound site and stimulate wound healing by activating molecular processes in the wound area through the enzymes they secrete. The larvae can stimulate wound healing by activating molecular processes in the wound area through enzymes in their excretions/secretions (ES). Studies have shown that ES has antibacterial, antifungal, anti-inflammatory, angiogenic, proliferative, hemostatic and tissue-regenerating effects both in vivo and in vitro. It is suggested that these effects stimulate wound healing and accelerate wound healing by initiating a direct signal cascade with cells in the wound area. However, the enzymes and peptides in ES are mostly still undefined. Examining the molecular content of ES and the biological effects of these ingredients is quite important to illuminate the molecular mechanism underlying MDT. More importantly, ES has the potential to have positive effects on wound healing and to be used more as a therapeutic agent in the future, so it can be applied as an alternative to MDT in wound healing.

Crustacean Proteases and Their Application in Debridement

Digestive proteases from marine organisms have been poorly applied to biomedicine. Exceptions are trypsin and other digestive proteases from a few cold-adapted or temperate fish and crustacean species. These enzymes are more efficient than enzymes from microorganism and higher vertebrates that have been used traditionally. However, the biomedical potential of digestive proteases from warm environment species has received less research attention. This review aims to provide an overview of this unrealised biomedical potential, using the debridement application as a paradigm. Debridement is intended to remove nonviable, necrotic and contaminated tissue, as well as fibrin clots, and is a key step in wound treatment. We discuss the physiological role of enzymes in wound healing, the use of exogenous enzymes in debridement, and the limitations of cold-adapted enzymes such as their poor thermal stability. We show that digestive proteases from tropical crustaceans may have advantages over their cold-adapted counterparts for this and similar uses. Differences in thermal stability, auto-proteolytic stability, and susceptibility to proteinase inhibitors are discussed. Furthermore, it is proposed that the feeding behaviour of the source organism may direct the evaluation of enzymes for particular applications, as digestive proteases have evolved to fill a wide variety of feeding habitats, natural substrates, and environmental conditions. We encourage more research on the biomedical application of digestive enzymes from tropical marine crustaceans.

What is the optimal treatment time for larval therapy? A study on incubation time and tissue debridement by bagged maggots of the greenbottle fly, Lucilia sericata

The effective use of larvae of the greenbottle fly, Lucilia sericata, in wound debridement requires a working knowledge of how feeding changes over time. Using a laboratory assay and bagged larval dressings, the effect of incubation time on larval feeding rates and body mass was investigated for up to 120 hours at 32°C. The mass of tissue digested increased significantly in incremental 24-hour periods up to 72 hours, with no significant consumption occurring afterwards. Larval mass increased only up to 48 hours. A further test comparing the efficacy of a single 96-hour application of larvae against two consecutive 48-hour applications found that the mass of tissue digested in the latter was 14.3% higher than the former, a difference that was statistically significant. Current clinical guidance suggests a 4-day application period for bagged larvae. Based on these results, an incubation time of 72 hours (3 days) for bagged larvae would be the most effective at the study temperature. However, it is acknowledged that wound temperature can vary, whereby feeding rates would likely differ. In view of this, we conclude that a period of 3 to 4 days is optimum for the application of larvae, and current guidelines should be adhered to.

Sarconesin: Sarconesiopsis magellanica Blowfly Larval Excretions and Secretions With Antibacterial Properties

Larval therapy (LT) is an alternative treatment for healing chronic wounds; its action is based on debridement, the removal of bacteria, and stimulating granulation tissue. The most important mechanism when using LT for combating infection depends on larval excretions and secretions (ES). Larvae are protected against infection by a spectrum of antimicrobial peptides (AMPs); special interest in AMPs has also risen regarding understanding their role in wound healing since they degrade necrotic tissue and kill different bacteria during LT. Sarconesiopsis magellanica (Diptera: Calliphoridae) is a promising medically-important necrophagous fly. This article reports a small AMP being isolated from S. magellanica ES products for the first time; these products were obtained from third-instar larvae taken from a previously-established colony. ES were fractionated by RP-HPLC using C18 columns for the first analysis; the products were then lyophilised and their antimicrobial activity was characterized by incubation with different bacterial strains. These fractions' primary sequences were determined by mass spectrometry and de novo sequencing; five AMPs were obtained, the Sarconesin fraction was characterized and antibacterial activity was tested in different concentrations with minimum inhibitory concentrations starting at 1.2 μM. Potent inhibitory activity was shown against Gram-negative (Escherichia coli D31, E. coli DH5α, Salmonella enterica ATCC 13314, Pseudomonas aeruginosa 27853) and Gram-positive (Staphylococcus aureus ATCC 29213, S. epidermidis ATCC 12228, Micrococcus luteus A270) bacteria. Sarconesin has a significant similarity with Rho-family GTPases which are important in organelle development, cytoskeletal dynamics, cell movement, and wound repair. The data reported here indicated that Sarconesin could be an alternative candidate for use in therapeutics against Gram-negative and Gram-positive bacterial infections. Our study describes one peptide responsible for antibacterial activity when LT is being used. The results shown here support carrying out further experiments aimed at validating S. magellanica AMPs as novel resources for combating antibacterial resistance.

Pharmacological Properties of the Medical Maggot: A Novel Therapy Overview

In the last decade, maggot has been hailed as the miraculous “medicinal maggot” for its diverse properties, including antimicrobial, antibiofilm, anti-inflammatory, and wound healing activities. The fact that maggots show so many beneficial properties has increased the interest in these tiny larvae dramatically. Whilst there is relatively abundant clinical evidence to demonstrate the success of maggots as debridement agents, not so much emphasis has been placed on the basic science evidence, which was a combination of physical and biochemical actions. This review differs from those earlier works in that it is undertaken to provide an update of the latest scientific basis published on maggot, particularly active ingredients within maggot excretions/secretions (ES). Further investigations should focus on the isolation, identification, recombination, transgenosis, and mass production of the beneficial molecules within maggots.

Benefits of maggot debridement therapy on leg ulcers: a literature review

Maggot debridement therapy (MDT) is an effective method for debriding wounds such as leg ulcers, supporting the concept of wound bed preparation ( Dumville et al, 2009 ; Soares et al, 2009 ; Mudge et al, 2014 ). New evidence is emerging to suggest that maggots might contribute to wound healing in other ways. For example, the reduction of biofilms and disinfection of wounds ( Van Der Plas et al, 2008 ; Brown et al, 2012 ; Pritchard and Brown, 2015 ) plus regulation of protease levels ( Chambers et al, 2003 ; Van Der Plas et al, 2009a ; Van Der Plas et al, 2009b ). This review will discuss research exploring new benefits of maggots in the management of individuals with chronic leg ulcers.

Quality control of a medicinal larval (Lucilia sericata) debridement device based on released gelatinase activity

Lucilia sericata Meigen (Diptera: Calliphoridae) larvae are manufactured worldwide for the treatment of chronic wounds. Published research has confirmed that the primary clinical effect of the product, debridement (the degradation of non-viable wound tissue), is accomplished by a range of enzymes released by larvae during feeding. The quality assessment of larval activity is currently achieved during production using meat-based assays, which monitor insect growth and/or the reduction in substrate mass. To support this, the present authors developed a complementary radial diffusion enzymatic assay to produce a visual and measureable indication of the activity of larval alimentary products (LAP) collected under standardized conditions, against a gelatin substrate. Using basic laboratory equipment and reagents, the assay is rapid and suited to high throughput. Assay reproducibility is high (standard deviation: 0.06-0.27; coefficient of variation: 0.75-4.31%) and the LAP collection procedure does not adversely affect larval survival (mortality: < 2%). Because it is both cost- and time-effective, this method is suited to both academic and industrial use and supports good manufacturing and laboratory practice as a quality control assay.

Mechanism of Action of Prolyl Oligopeptidase (PREP) in Degenerative Brain Diseases: Has Peptidase Activity Only a Modulatory Role on the Interactions of PREP with Proteins?

In the aging brain, the correct balance of neural transmission and its regulation is of particular significance, and neuropeptides have a significant role. Prolyl oligopeptidase (PREP) is a protein highly expressed in brain, and evidence indicates that it is related to aging and in neurodegenration. Although PREP is regarded as a peptidase, the physiological substrates in the brain have not been defined, and after intense research, the molecular mechanisms where this protein is involved have not been defined. We propose that PREP functions as a regulator of other proteins though peptide gated direct interaction. We speculate that, at least in some processes where PREP has shown to be relevant, the peptidase activity is only a consequence of the interactions, and not the main physiological activity.

Next Generation Sequencing Identifies Five Major Classes of Potentially Therapeutic Enzymes Secreted by Lucilia sericata Medical Maggots

Lucilia sericata larvae are used as an alternative treatment for recalcitrant and chronic wounds. Their excretions/secretions contain molecules that facilitate tissue debridement, disinfect, or accelerate wound healing and have therefore been recognized as a potential source of novel therapeutic compounds. Among the substances present in excretions/secretions various peptidase activities promoting the wound healing processes have been detected but the peptidases responsible for these activities remain mostly unidentified. To explore these enzymes we applied next generation sequencing to analyze the transcriptomes of different maggot tissues (salivary glands, gut, and crop) associated with the production of excretions/secretions and/or with digestion as well as the rest of the larval body. As a result we obtained more than 123.8 million paired-end reads, which were assembled de novo using Trinity and Oases assemblers, yielding 41,421 contigs with an N50 contig length of 2.22 kb and a total length of 67.79 Mb. BLASTp analysis against the MEROPS database identified 1729 contigs in 577 clusters encoding five peptidase classes (serine, cysteine, aspartic, threonine, and metallopeptidases), which were assigned to 26 clans, 48 families, and 185 peptidase species. The individual enzymes were differentially expressed among maggot tissues and included peptidase activities related to the therapeutic effects of maggot excretions/secretions.

The impacts of larval density and protease inhibition on feeding in medicinal larvae of the greenbottle fly Lucilia sericata

Larval therapy, the therapeutic use of blowfly larvae to treat chronic wounds, is primarily used in debridement. There are, however, gaps in current knowledge of the optimal clinical application of the therapy and mechanisms of action in the debridement process. Using an artificial assay, two studies were undertaken to investigate these aspects of larval debridement by Lucilia sericata Meigen (Diptera: Calliphoridae); the first studied the effects of the density of larvae on tissue digestion and larval mass, and the second considered the effects on the same parameters of incorporating protease inhibitors into the feeding substrate. The total mass of tissue digested increased with larval density until saturation was observed at 5.0-7.5 larvae/cm(2) . This range was considered optimal as lower doses resulted in the removal of less tissue and higher doses offered no additional tissue removal and appeared to exacerbate competition for feeding. In the second study, increased protease inhibitor concentration led to significant decreases in tissue digestion and larval mass, suggesting that serine proteases, particularly trypsin, may play major roles in larval digestion. Such information is important in elucidating the main constituents that make up larval digestive products and may be significant in the development of new therapies.

Growth and survival of blowfly Lucilia sericata larvae under simulated wound conditions: implications for maggot debridement therapy

Maggot debridement therapy has become a well-established method of wound debridement. Despite its success, little information is available about the optimum duration of the treatment cycle and larval growth in wounds. This study examines the development of Lucilia sericata (Diptera: Calliphoridae) larvae under two containment conditions (bagged and free range) under simulated wound conditions and assesses the impact of transport and further storage of larvae on their survival and growth. There was no significant difference in size between bagged and free-range larvae over the 72-h experimental period. Larvae grew fastest 8-24 h after inoculation and completed their growth at 40-48 h. Mortality rates were similar (0.12-0.23% per hour) in both containment conditions and did not differ significantly (P = 0.3212). Survival of free-range larvae was on average 16% lower than survival of bagged larvae. Refrigeration of larvae upon simulated delivery for > 1 day reduced their survival to < 50% and caused a reduction in growth of up to 30% at 12 h, but not at 48 h, of incubation. Therefore, it is recommended that free-range larvae are left in the wound for a maximum of 40-48 h, and bagged larvae for 48-72 h. Larvae should be used within 24 h of delivery to avoid high mortality caused by prolonged refrigeration.

TIME management by medicinal larvae

Wound bed preparation (WBP) is an integral part of the care programme for chronic wounds. The acronym TIME is used in the context of WBP and describes four barriers to healing in chronic wounds; namely, dead Tissue, Infection and inflammation, Moisture imbalance and a non-migrating Edge. Larval debridement therapy (LDT) stems from observations that larvae of the blowfly Lucilia sericata clean wounds of debris. Subsequent clinical studies have proven debriding efficacy, which is likely to occur as a result of enzymatically active alimentary products released by the insect. The antimicrobial, anti-inflammatory and wound healing activities of LDT have also been investigated, predominantly in a pre-clinical context. This review summarises the findings of investigations into the molecular mechanisms of LDT and places these in context with the clinical concept of WBP and TIME. It is clear from these findings that biotherapy with L. sericata conforms with TIME, through the enzymatic removal of dead tissue and its associated biofilm, coupled with the secretion of defined antimicrobial peptides. This biotherapeutic impact on the wound serves to reduce inflammation, with an associated capacity for an indirect effect on moisture imbalance. Furthermore, larval serine proteinases have the capacity to alter fibroblast behaviour in a manner conducive to the formation of granulation tissue.

The effects of Sarconesiopsis magellanica larvae (Diptera: Calliphoridae) excretions and secretions on fibroblasts

Sarconesiopsis magellanica is a necrophagous blowfly which is relevant in both forensic and medical sciences. Previous studies regarding this species have led to understanding life-cycle, population and reproduction parameters, as well as identifying and characterising proteolytic enzymes derived from larval excretions and secretions (ES). As other studies have shown that ES proteolytic activity plays a significant role in wound healing and fibroblasts play a relevant role in granulation tissue formation during such healing, the present study was aimed at analysing the biological effect of S. magellanica larval ES on fibroblasts. ES were obtained from third-instar larvae and added to fibroblast cells at three concentrations (10, 5 and 1 μg/mL) to evaluate their behaviour. MTT assays were used for analysing cell proliferation and viability, whilst cell adhesion was measured by optical density with 10% SDS. Fibroblast migration and morphology was recorded by microscopic observation. ES did not affect fibroblast viability and induced an increase in cell proliferation; cell adhesion became reduced, whilst cell migration through extracellular matrix increased. ES also induced a decreased cell surface and morphological alterations. Changes in all the above-mentioned parameters were reduced when ES were incubated at 60 °C, probably due to protease denaturation. These results suggested that the proteases contained in S. magellanica larval ES contributed towards granulation tissue formation, increased cell migration and promoted cell proliferation. All these data support carrying out further experiments aimed at validating S. magellanica usefulness in larval therapy.

Recent advances in developing insect natural products as potential modern day medicines

Except for honey as food, and silk for clothing and pollination of plants, people give little thought to the benefits of insects in their lives. This overview briefly describes significant recent advances in developing insect natural products as potential new medicinal drugs. This is an exciting and rapidly expanding new field since insects are hugely variable and have utilised an enormous range of natural products to survive environmental perturbations for 100s of millions of years. There is thus a treasure chest of untapped resources waiting to be discovered. Insects products, such as silk and honey, have already been utilised for thousands of years, and extracts of insects have been produced for use in Folk Medicine around the world, but only with the development of modern molecular and biochemical techniques has it become feasible to manipulate and bioengineer insect natural products into modern medicines. Utilising knowledge gleaned from Insect Folk Medicines, this review describes modern research into bioengineering honey and venom from bees, silk, cantharidin, antimicrobial peptides, and maggot secretions and anticoagulants from blood-sucking insects into medicines. Problems and solutions encountered in these endeavours are described and indicate that the future is bright for new insect derived pharmaceuticals treatments and medicines.

Could microbe stimulated maggots become a targeted natural antibiotics family?

Maggot debridement therapy plays an important role in treatment of diabetic foot ulcers and other chronic infectious wounds, cause of this is its extremely low drug resistance. However, the microbe stimulated maggot, we may call it a derivative of normal sterile maggot, could exhibit stronger bacterial or bactericidal effects. Methods of the pretreatment on maggot was different germ solution were artificially mixed and added with originally sterile maggots, the novel secretions were collected. Some of this have been demonstrated by plate test and telescope analysis. Thus, we hypothesize that maggot especially the larvae of Lucilia sericata was conducted as the germ irritant receptor, and diverse germs interacted with it, at last, novel secretions/excretions we got will offer a great help to the general surgery clinicians as well as researchers who are interested in novel antibiotics discovery.

Proteolytic activity regarding Sarconesiopsis magellanica (Diptera: Calliphoridae) larval excretions and secretions

Sarconesiopsis magellanica (Diptera: Calliphoridae) is a medically important necrophagous fly which is used for establishing the post-mortem interval. Diptera maggots release proteolytic enzymes contained in larval excretion and secretion (ES) products playing a key role in digestion. Special interest in proteolytic enzymes has also been aroused regarding understanding their role in wound healing since they degrade necrotic tissue during larval therapy. This study was thus aimed at identifying and characterising S. magellanica proteolytic enzyme ES products for the first time. These products were obtained from first-, second- and third-instar larvae taken from a previously-established colony. ES proteins were separated by SDS-PAGE and their proteolytic activity was characterised by zymograms and inhibition assays involving BAPNA (Nα-benzoyl-dl-Arg-p-nitroanilide) and SAPNA substrates, using synthetic inhibitors. The protein profile ranged from ∼69kDa to ∼23kDa; several of them coincided with the Lucilia sericata ES protein profile. Serine-protease hydrolysis activity (measured by zymogram) was confirmed when a ∼25kDa band disappeared upon ES incubation with PMSF inhibitor at pH 7.8. Analysis of larval ES proteolytic activity on BAPNA and SAPNA substrates (determined by using TLCK and TPCK specific inhibitors) suggested a greater amount of trypsin-like protease. These results support the need for further experiments aimed at validating S. magellanica use in larval therapy.

Growth and Survival of Bagged Lucilia sericata Maggots in Wounds of Patients Undergoing Maggot Debridement Therapy

Maggot debridement therapy (MDT) is an established method of debridement of nonhealing wounds. Despite intense clinical research about its efficacy and effects of substances produced by the larvae, growth and development of maggots in the wounds remain largely unexplored. In the present study, the bags with larvae (n = 52), which had been used to debride traumatic, ischemic, diabetic and venous ulcers, were collected and examined. Survival, length, width and larval instar of the maggots within each bag were recorded and analyzed with respect to the wound type and duration of the treatment. Survival of maggots after a 48-h cycle of MDT ranged between 63.6 and 82.7%. Maggots in venous ulcers had on average 9–19% higher mortality than maggots within traumatic, ischemic, and diabetic ulcers. Length of larvae after 48 h cycle of MDT reached on average 7.09–9.68 mm, and average width varied between 1.77 and 2.26 mm. Larvae in venous ulcers were significantly smaller after 48 h, but not after 72 h treatment compared to the other wound types. Further studies should be aimed to identify other patient-associated factors which might influence growth and survival of the larvae during maggot debridement therapy.

Degradation of MSCRAMM target macromolecules in VLU slough by Lucilia sericata chymotrypsin 1 (ISP) persists in the presence of tissue gelatinase activity

Venous leg ulcer slough is unpleasant to the patient and difficult to manage clinically. It harbours infection, also preventing wound management materials and dressings from supporting the underlying viable tissues. In other words, slough has significant nuisance value in the tissue viability clinic. In this study, we have sought to increase our knowledge of slough by building upon a previous but limited analysis of this necrotic tissue. In particular, slough has been probed using Western blotting for the presence of proteins with the capacity to engage microbial surface components recognising adhesive matrix macromolecules. Although the samples were difficult to resolve, we detected fibrinogen, fibronectin, IgG, collagen, human serum albumin and matrix metalloproteinase-9. Furthermore, the effect of a maggot-derived debridement enzyme, chymotrypsin 1 on macromolecules in slough was confirmed across seven patient samples. The effect of chymotrypsin 1 on slough confirms our thesis that this potential debridement enzyme could be effective in removing slough along with its associated bacteria, given its observed resistance to intrinsic gelatinase activity. In summary, we believe that the data provide scientists and clinicians with further insights into the potential molecular interactions between bacteria, wound tissue and Lucilia sericata in a clinically problematic yet scientifically interesting wound ecosystem.

Lucilia sericata chymotrypsin disrupts protein adhesin-mediated staphylococcal biofilm formation

Staphylococcus aureus and Staphylococcus epidermidis biofilms cause chronic infections due to their ability to form biofilms. The excretions/secretions of Lucilia sericata larvae (maggots) have effective activity for debridement and disruption of bacterial biofilms. In this paper, we demonstrate how chymotrypsin derived from maggot excretions/secretions disrupts protein-dependent bacterial biofilm formation mechanisms.

Blow fly Lucilia sericata nuclease digests DNA associated with wound slough/eschar and with Pseudomonas aeruginosa biofilm

In chronic wounds, it may be clinically important to remove extracellular bacterial and patient DNA as its presence may impede wound healing and promote bacterial survival in biofilm, in which extracellular DNA forms part of the biofilm architecture. As medicinal maggots, larvae of Lucilia sericata Meigen (Diptera: Calliphoridae) have been shown to efficiently debride wounds it became of interest to investigate their excretions/secretions (ES) for the presence of a deoxyribonuclease (DNAse) activity. Excretions/secretions products were shown to contain a DNAse, with magnesium, sodium and calcium metal ion dependency, and a native molecular mass following affinity purification of approximately 45 kDa. The affinity purified DNAse degraded genomic bacterial DNA per se, DNA from the slough/eschar of a venous leg ulcer, and extracellular bacterial DNA in biofilms pre-formed from a clinical isolate of Pseudomonas aeruginosa. The latter finding highlights an important attribute of the DNAse, given the frequency of P. aeruginosa infection in non-healing wounds and the fact that P. aeruginosa virulence factors can be toxic to maggots. Maggot DNAse is thus a competent enzyme derived from a rational source, with the potential to assist in clinical wound debridement by removing extracellular DNA from tissue and biofilm, and promoting tissue viability, while liberating proteinaceous slough/eschar for debridement by the suite of proteinases secreted by L. sericata.

Wound debridement potential of glycosidases of the wound-healing maggot, Lucilia sericata

The wound-healing maggot, Lucilia sericata Meigen (Diptera: Calliphoridae), degrades extracellular matrix components by releasing enzymes. The purpose of this study was to investigate the glycosylation profiles of wound slough/eschar from chronic venous leg ulcers and the complementary presence of glycosidase activities in first-instar excretions/secretions (ES1) and to define their specificities. The predominant carbohydrate moieties present in wound slough/eschar were determined by probing one-dimensional Western blots with conjugated lectins of known specificities. The presence of specific glycosidase activities in ES1 was determined using chromogenic and fluorogenic substrates. The removal of carbohydrate moieties from slough/eschar proteins by glycosidases in ES1 was determined by two-dimensional electrophoresis and Emerald 300 glycoprotein staining. α-D-glucosyl, α-D-mannosyl and N-acetylglucosamine residues were detected on slough/eschar-derived proteins. Furthermore, it was demonstrated that the treatment of slough/eschar with ES1 significantly reduced uptake of the carbohydrate-specific stain. Subsequently, α-D-glucosidase, α-D-mannosidase and N-acetylglucosaminidase activities were identified in ES1. Specific chromogenic and fluorogenic substrates and gel filtration chromatography showed that these activities result from distinct enzymes. These activities were mirrored in the removal of α-D-glucosyl, α-D-mannosyl and N-acetylglucosamine residues from proteins of slough/eschar from maggot-treated wounds. These data suggest that maggot glycosidases remove sugars from slough/eschar proteins. This may contribute to debridement, which is ultimately accomplished by a suite of biochemically distinct enzymes present in ES1.

Recombinant Lucilia sericata chymotrypsin in a topical hydrogel formulation degrades human wound eschar ex vivo

Larval biotherapy is a debridement tool used in wound management. The mechanism of action involves degradation of eschar by serine proteases including chymotrypsin within the alimentary fluids of first instar Lucilia sericata. With the rationale of obviating some limitations of biotherapy, including cost, complexity of use, and patient reticence, the present study describes a mobile hydrogel formulation containing freeze-dried recombinant L. sericata chymotrypsin designed for topical application. Neither freeze-drying nor formulation into the hydrogel significantly attenuated the measured activity of released enzyme compared to fresh-frozen enzyme in aqueous solution. Gel electrophoresis confirmed qualitatively that the chymotrypsin/hydrogel formulation both with and without supplementary urea at 10% (w) /(v) degraded human chronic wound eschar ex vivo. Mindful that the hallmark of intractability of chronic wounds is aberrant biochemistry, the pH activity profile for the enzyme/hydrogel formulation was compared with exudate pH in chronic wounds of mixed aetiology in a cohort of 48 hospital in-patients. Five patients' wounds were acidic, however, the remainder were predominantly alkaline and coincided with the pH optimum for the insect enzyme. Thus, a recombinant L. sericata chymotrypsin and hydrogel formulation could represent a pragmatic alternative to larval therapy for the management of chronic wounds.