Excretions/secretions from medicinal larvae (Lucilia sericata) inhibit complement activation by two mechanisms

Inhibition of vertebrate complement system by hematophagous arthropods: inhibitory molecules, mechanisms, physiological roles, and applications

In arthropods, hematophagy has arisen several times throughout evolution. This specialized feeding behavior offered a highly nutritious diet obtained during blood feeds. On the other hand, blood-sucking arthropods must overcome problems brought on by blood intake and digestion. Host blood complement acts on the bite site and is still active after ingestion, so complement activation is a potential threat to the host's skin feeding environment and to the arthropod gut enterocytes. During evolution, blood-sucking arthropods have selected, either in their saliva or gut, anticomplement molecules that inactivate host blood complement. This review presents an overview of the complement system and discusses the arthropod's salivary and gut anticomplement molecules studied to date, exploring their mechanism of action and other aspects related to the arthropod-host-pathogen interface. The possible therapeutic applications of arthropod's anticomplement molecules are also discussed.

Maggot Treatment of Necrotic Toe Developed After Traumatic Subtotal Amputation

Maggot debridement therapy (MDT) has been used for years in the treatment of chronic wounds and necrotic tissues. We report a case of subtotally amputated third toe that was treated with MDT after reattachment and developing complete necrosis. The necrotic toe was replaced with viable tissue and the wound healed completely after 2 weeks of MDT application. This case points out the regenerative effects of MDT besides its mechanical debridement effect on the necrotic tissue.

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.

Opposite valence social information provided by bio-robotic demonstrators shapes selection processes in the green bottle fly

Social learning represents a high-level complex process to acquire information about the environment, which is increasingly reported in invertebrates. The animal-robot interaction paradigm turned out to be an encouraging strategy to unveil social learning in vertebrates, but it has not been fully exploited in invertebrates. In this study, Lucilia sericata adults were induced to observe bio-robotic conspecific and predator demonstrators to reproduce different flower foraging choices. Can a fly manage two flows of social information with opposite valence? Herein, we attempt a reply. The selection process of L. sericata was affected by social information provided through different bio-robotic demonstrators, by avoiding coloured discs previously visited by a bio-robotic predator and preferring coloured discs previously visited by a bio-robotic conspecific. When both bio-robotic demonstrators visited the same disc, the latency duration increased and the flies significantly tended to avoid this disc. This indicates the complex risk-benefit evaluation process carried out by L. sericata during the acquisition of such social information. Overall, this article provides a unique perspective on the behavioural ecology of social learning in non-social insects; it also highlights the high potential of the animal-robot interaction approach for unveiling the full spectrum of invertebrates' abilities in using social information.

Telehealth-guided home-based maggot debridement therapy for chronic complex wounds: Peri- and post-pandemic potential

Patients with complex chronic lower extremity wounds require a great deal of interaction with outpatient and inpatient services. Paradoxically, these are the very patients that, because of their chronic comorbidities, are at greatest risk for COVID-related morbidity and mortality. Disinfected Phaenicia (Lucilia) sericata (Medical Maggots; Monarch Labs, Irvine, California) were applied in a standardised fashion by a home-health nurse with direct monitoring, guidance, and collaboration of the attending surgeon. A family member was able to change the outer dressing daily based on normal wound exudate. The inner maggot debridement therapy (MDT) dressing was changed at 2 days showing dramatic reduction in necrotic tissue, elimination of profound malodor, and no evidence of local or advancing infection. The entire initial telehealth-guided application took approximately 20 minutes. The first telehealth-guided MDT dressing change took 14 minutes. We used an artificial-intelligence-based algorithm to measure changes in wound characteristics. At day 0, 46% of the total surface area was covered in malodorous black, necrotic tissue. The first dressing change saw an elimination in assessed malodor with necrotic tissue constituting 14% of total surface area. The second dressing change at 5 days showed a greater than 99% reduction in necrotic tissue. This manuscript constitutes what we believe to be the first telehealth-guided MDT conducted during a resource-limited peri-pandemic period. We believe that MDT, which is an extension of efforts regularly performed in clinic and hospital, may have the potential to reduce resource usage while potentially improving care and quality of life for people with limb and life-threatening complications of diabetes and other chronic diseases.

Maggot Therapy in Wound Healing: A Systematic Review

BACKGROUND

It is estimated that 2% of the population in developing countries suffer from a chronic wound, making it a hidden phenomenon that is increasing as populations age. The ease of access to maggot therapy has made it increasingly attractive for implementation. This study aimed to explore the effectiveness of maggot therapy as compared to hydrogel dressings in the healing of chronic wounds.

METHODS

An electronic literature search until October 2019 was performed using Medline, Embase, and Cumulative Index of Nursing and Allied Health Literature. The eligibility criteria were chronic wound patients with an intervention that involved a comparison of any maggot species with hydrogel dressings.

RESULTS

The full text of five studies, involving 580 patients with chronic wounds, was retrieved. Four studies used the Lucilia sericata species. The maggot therapy facilitated faster and more effective debridement of non-viable tissue. It enabled faster development of granulation tissue and increased reduction in the wound surface area compared to hydrogel dressings. Maggot therapy had no effect on disinfection or complete healing rate for the wound.

CONCLUSION

Maggot therapy should be considered for faster wound debridement, granulation tissue development, and wound surface area reduction as well as in surgical contraindications. This review can be used as a guide to assist clinicians in identifying patients who may benefit from maggot therapy.

First Report on the Use of Larvae of Cochliomyia macellaria (Diptera: Calliphoridae) for Wound Treatment in Veterinary Practice

Factors contributing to the delay or prevention of the natural wound healing process include infection and ineffective conventional treatment. Alternative therapies, such as the maggot debridement therapy (MDT), may be helpful for successful treatment in these cases. Aiming to disseminate information about the possibility of using other species of flies for wound treatment, besides the best known Lucilia sericata Meigen, 1826 (Diptera, Calliphoridae), we report here a successful MDT case with the application of Cochliomyia macellaria (Fabricius, 1775) larvae to treat an infected wound with extensive area of necrotic tissue in a dog. Five sterile larvae were applied to each square-cm of lesion and kept on the animal for only 48 h. The healing was successful, from both qualitative and quantitative points of view. The ratio of wound healing (RWH) reached almost 50% on the 5th day and 100% on the 14th day after MDT. Although the overall animal prognosis had been unfavorable, mainly due to the sepsis, the patient began to recover and had improved clinical condition from the fifth day after MDT. This study shows the importance and effectiveness of MDT in promoting faster and more complete healing of a complex wound.

New Insights Into Culturable and Unculturable Bacteria Across the Life History of Medicinal Maggots Lucilia sericata (Meigen) (Diptera: Calliphoridae)

Because of the nutritional ecology of dung- and carrion-feeding, bacteria are the integral part of Lucilia sericata life cycle. Nevertheless, the disinfected larvae of the blowfly are applied to treat human chronic wounds in a biosurgery named maggot debridement therapy (MDT). To realize the effects of location/diet on the gut bacteria, to infer the role of bacteria in the blowfly ecology plus in the MDT process, and to disclose bacteria circulating horizontally in and vertically between generations, bacterial communities associated with L. sericata specimens from various sources were investigated using culture-based and culture-independent methods. In total, 265 bacteria, including 20 families, 28 genera, and 40 species, were identified in many sources of the L. sericata. Culture-dependent method identified a number of 144 bacterial isolates, including 21 species, in flies reared in an insectary; specimens were collected from the field, and third-instar larvae retrieved from chronic wounds of patients. Metagenetic approach exposed the occurrences of 121 operational taxonomic units comprising of 32 bacterial species from immature and adult stages of L. sericata. Gammaproteobacteria was distinguished as the dominant class of bacteria by both methods. Bacteria came into the life cycle of L. sericata over the foods and transovarially infected eggs. Enterococcus faecalis, Myroides phaeus, Proteus species, Providencia vermicola, and Serratia marcescens were exchanged among individuals via transstadial transmission. Factors, including diets, feeding status, identification tool, gut compartment, and life stage, governed the bacteria species. Herein, we reemphasized that L. sericata is thoroughly connected to the bacteria both in numerous gut compartments and in different life stages. Among all, transstadially transmitted bacteria are underlined, indicating the lack of antagonistic effect of the larval excretions/secretions on these resident bacteria. While the culture-dependent method generated useful data on the viable aerobic gut bacteria, metagenomic method enabled us to identify bacteria directly from the tissues without any need for cultivation and to facilitate the identification of anaerobic and unculturable bacteria. These findings are planned to pave the way for further research to determine the role of each bacterial species/strain in the insect ecology, as well as in antimicrobial, antibiofilm, anti-inflammatory, and wound healing activities.

Effectiveness of Chronic Wound Debridement with the Use of Larvae of Lucilia Sericata

The process of successful wound healing depends on effective debridement and infection control. One method of wound debridement, known since antiquity, is based on the use of fly larvae. Solid scientific evidence proves that maggot debridement therapy (MDT), like surgical intervention, can be effectively and safely used to remove necrotic tissue. Based on a review of the related literature, this study was designed to assess the effectiveness of chronic wound cleansing with the use of larvae of Lucilia sericata (Phaenicia sericata). Maggot therapy, applied in wound debridement and treatment, is a safe and effective method. Its benefits are associated with debridement, disinfection and faster tissue growth. MDT may reduce the duration of antibiotic therapy and the need for hospitalization, or it may decrease the number of outpatient visits required. It is a relatively cost-effective method, and, in addition to financial gains, it may reduce the frequency of inpatient treatment. In the literature, an increasing amount of scientific evidence confirms that such treatment can effectively reduce the biofilm and bacterial load in a wound.

DNA methylation analysis of negative pressure therapy effect in diabetic foot ulcers

OBJECTIVE

Negative pressure wound therapy (NPWT) has been used to treat diabetic foot ulcerations (DFUs). Its action on the molecular level, however, is only partially understood. Some earlier data suggested NPWT may be mediated through modification of local gene expression. As methylation is a key epigenetic regulatory mechanism of gene expression, we assessed the effect of NPWT on its profile in patients with type 2 diabetes (T2DM) and neuropathic non-infected DFUs.

METHODS

Of 36 included patients, 23 were assigned to NPWT and 13 to standard therapy. Due to ethical concerns, the assignment was non-randomized and based on wound characteristics. Tissue samples were obtained before and 8 ± 1 days after therapy initiation. DNA methylation patterns were checked by Illumina Methylation EPIC kit.

RESULTS

In terms of clinical characteristics, the groups presented typical features of T2DM; however, the NPWT group had significantly greater wound area: 16.8 cm2 vs 1.4 cm2 (P = 0.0003). Initially only one region at chromosome 5 was differentially methylated. After treatment, 57 differentially methylated genes were found, mainly located on chromosomes 6 (chr6p21) and 20 (chr20p13); they were associated with DNA repair and autocrine signaling via retinoic acid receptor. We performed differential analyses pre treatment and post treatment. The analysis revealed 426 differentially methylated regions in the NPWT group, but none in the control group. The enrichment analysis showed 11 processes significantly associated with NPWT, of which 4 were linked with complement system activation. All but one were hypermethylated after NPWT.

CONCLUSION

The NPWT effect on DFUs may be mediated through epigenetic changes resulting in the inhibition of complement system activation.

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.